Symposium Organizers
Elisabetta Comini Universita' di Brescia
Pelagia Irene Gouma State University of New York-Stony Brook
Vincenzo Guidi University of Ferrara
David Kubinski Ford Motor Company
R1: Hybrids Materials and Detectors
Session Chairs
Tuesday PM, April 18, 2006
Room 3022 (Moscone West)
9:30 AM - **R1.1
Bio-Hybrid Materials for Immunoassay-Based Sensing.
Jonathan Fang 1 , Esther Lan 1 , Jing Zhou 1 , Bruce Dunn 1
1 Department of Materials Science and Engineering, University of California-Los Angeles, Los Angeles, California, United States
Show AbstractThe flexible solution chemistry of the sol-gel process has been used to synthesize nanostructured materials based on the encapsulation of biomolecules in a transparent, inorganic matrix. The resulting bio-hybrid material possesses two phases: a network of solid colloidal particles arranged with interpenetrating mesoporosity and a continuous solvent phase. It is now well established that the dopant biomolecules are immobilized in the mesoporous network and become part of the nanostructured architecture of the material. In nearly all cases, the dopant biomolecules retain their spectroscopic properties and biological activity. The resulting bio-hybrid materials have been widely explored as sensors with the biomolecule serving as both the biorecognition and transduction elements while the transparency of the matrix enables spectroscopic monitoring of the reactions.In this presentation we review our research directed at developing bio-hybrid based immunoassay approaches. We focus on the detection of cortisol, a steroid hormone released in the body at elevated levels in response to stress, which has become one of the principal biomarkers for monitoring astronaut health. We have developed a thin film optical biosensor for cortisol that was designed as part of a compact bioassay system for on-orbit monitoring and requires minimal liquid handling. The analysis is based on a competitive immunoassay in which cortisol antibodies are encapsulated in the sol-gel matrix. Well-defined calibration curves were obtained and the method of standard additions was used to determine quantitatively the cortisol concentration in human serum samples. The accuracy of the bio-hybrid immunoassay was demonstrated by the close correlation between the values from the bio-hybrid detector and those obtained using traditional immuno-binding techniques. In addition to cortisol, we will also present some of our recent immunoassay results involving the detection of peptides.
10:00 AM - R1.2
Biomimetic Nanotechnology: Structural Stability of Polypeptide Nanofilms.
Bingyun Li 1 , Donald Haynie 2
1 Orthopaedics, West Virginia University School of Medicine, Morgantown, West Virginia, United States, 2 Biomedical Engineering and Physics, Louisiana Tech University, Ruston, Louisiana, United States
Show AbstractSelf-assembly of designed polypeptides is a promising area of biomaterials research and development. We have prepared polypeptide nanofilms by electrostatic layer-by-layer self-assembly of cysteine-containing 32mers. We have studied the structural stability of the films by subjecting them to various extreme physical and chemical conditions. The results suggest that the film structure is very stable in organic solvent and, when dehydrated, at extreme temperatures. Such stability is in marked contrast to the behavior of proteins, which tend to denature under comparable conditions. Similar to proteins, polypeptide nanofilms cross-linked by disulfide bonds are considerably stronger than films stabilized by electrostatic, van der Waals, or hydrophobic interactions alone. These results provide further information on self-assembly of polypeptides which are a promising class of polyelectrolytes for the creation of nanofilms for biotechnology and biomedicine applications.
10:15 AM - R1.3
The Neurochip: An Advanced Nanomaterial for Small Molecule Capture of Biomolecule Binding Partners
Amit Vaish 1 4 , Mitchell Shuster 2 , Paul Weiss 3 2 1 , Michael Pishko 4 1 3 , Anne Andrews 6 1 3
1 Huck Institute of Life Sceince, Penn State University, State College, Pennsylvania, United States, 4 Chemical Engineering, Penn State University, State College, Pennsylvania, United States, 2 Physics, Penn State University, State College, Pennsylvania, United States, 3 Chemistry, Penn State University, State College, Pennsylvania, United States, 6 Veterinary Science, Penn State University, State College, Pennsylvania, United States
Show AbstractWe have developed coupling chemistries to tether the prototype small molecule neurotransmitter serotonin and its carboxylated precursor, 5-hydroxytryptophan, to “insertion-directed” self-assembled monolayers on Au surfaces thus achieving dilute, non-phase separated ligand coverage. Coupling chemistries are verified by grazing angle FT-IR. Nonspecific binding has been largely eliminated by surrounding the tethered ligands with oligoethylene glycols. Good specificity of the surfaces has been demonstrated by quartz crystal microbalance measurements of specific antibody recognition of serotonin-functionalized surfaces and serotonin membrane receptor recognition of 5-hydroxytryptophan surfaces, the latter mimicking free solution bio-recognition of serotonin. “Neurochip” materials will be used to screen for nucleic acid aptamers, which will be utilized as molecular recognition elements in the construction of novel nanosensors for in vivo neurotransmitter sensing.
10:30 AM - R1.4
Biocompatible poly(magnesium acrylate) Micro-pomegranates for Enzyme Immobilization.
Enrique Lopez_Cabarcos 1 , Jorge Retama 1 , Alejandro Castillo 1 , Beatriz Ruiz 2
1 Physical Chemistry II, Complutense University, Madrid Spain, 2 Analytical Chemistry , Complutense University, Madrid Spain
Show Abstract10:45 AM - R1.5
Anomalous pH Actuation of a Chitosan/SWNT Microfiber Hydrogel with Improved Mechanical Property
S. R. Shin 1 , S. J. Park 1 , S. G. Yoon 1 , C. K. Lee 1 , K. M. Shin 1 , M. K. Shin 1 , B. K. Gu 1 , M. S. Kim 1 , Y. J. Kim 1 , S. J. Kim 1
1 Dept. of Biomedical Engineering, Hanyang University, Seoul Korea (the Republic of)
Show AbstractSoft biological microactuators using pH-sensitive hydrogels have been studied for developing microactuation or biosensors systems. The actuators undergo a reversible change in volume that results in a dramatic dimensional swelling and shrinking on exposure to and removal of an external pH stimulus. Chitosan is candidate for soft biological microactuator because it is biocompatible natural polymer and swells in acidic media due to the protonation of the amino groups. However, the mechanical properties of chitosan hydrogels are rather poor for microactuator. So the single-wall carbon nanotubes (SWNTs) have been used to reinforce the biocompatible polymer chitosan. In this work, composite microfibers composed of chitosan and SWNTs have been fabricated with a wet spinning method. The dispersion was improved by sonic agitation of SWNTs in a chitosan solution and then centrifugation to remove tube aggregates. Raman spectroscopy was used to measure the SWNTs state in solution, the form of the microfibers. The average diameter of the microfibers is 80–130 μm and has a smooth, uniform, striated surface. The mechanical behavior was investigated with dynamic mechanical analysis (DMA). Mechanical testing showed a dramatic increase in Young’s modulus for the chitosan/SWNTs composite fibers fabricated using the improved dispersion method. The wet mechanical properties were also improved by addition of SWNTs while the pH sensitivity of the microfibers was largely unchanged. The strain on the microfibers was determined from tensile load measurements during pH switching in acidic or basic electrolyte solutions. The microfibers showed a general actuation behavior of expanding at pH = 2 and contracting at pH = 7 under low tensile loads. However, the reverse actuation behavior was exhibited under high tensile loads. This anomalous pH actuation is both new and surprising. It can be explained from analysis of the differences in sample stiffness and Poisson’s ratio under tensile load in electrolyte solutions with different pH values.
11:30 AM - **R1.6
Intercalative Organic/MoO3 Nanohybrids for the detection of VOCs
Ichiro Matsubara 1 , Tohio Itoh 1 , Junzhong Wang 1 , Woosuck Shin 1 , Noriya Izu 1 , Norimitsu Murayama 1
1 , National Institute of Advanced Industrial Science & Technology (AIST), Nagoya Japan
Show AbstractWe have proposed intercalative type organic-inorganic hybrid materials as gas sensors for selective detection of volatile organic compounds (VOCs). The organic and inorganic components take part in molecular recognition and transduction of chemical signals to measurable resistance changes, respectively. We have prepared intercalative organic/MoO3 hybrid materials with a layered structure. The thin films of Polypyrrole intercalated ((PPy)xMoO3) hybrid exhibit a distinct response to formaldehyde and acetaldehyde gases by increasing in their electrical resistivity, which could be induced by the incorporation of VOC molecules into the interlayers. On the other hand, polystylene intercalated MoO3 hybrid shows the resistance decreasing response to acetaldehyde gas. The two types of hybrid materials show the different response to VOCs, indicating that the VOC gas responsibility could be controlled by the organic component.
12:00 PM - R1.7
Stem Cell Impregnated Carbon Nanofibers/Nanotubes for Healing Damaged Neural Tissue.
Jong Eun Lee 3 , Jong Youl Kim 3 , Dongwoo Khang 4 , Thomas Webster 1 2
3 Anatomy, Yonsei University, Seoul Korea (the Republic of), 4 Physics, Purdue University, West Lafayette, Indiana, United States, 1 Biomedical Engineering, Purdue University, Lafayette, Indiana, United States, 2 Materials Engineering, Purdue University, West Lafayette, Indiana, United States
Show AbstractDue to their electrical and geometric properties similar to constituent components of neural tissue, carbon nanofibers/nanotubes are intriguing materials for neural tissue engineering applications. For this purpose, the objective of the present collection of studies was to determine functions of neural cells (including neurons, astrocytes (cells that contribute to detrimental glial scar tissue formation), and neural stem cells) on carbon nanofibers/nanotubes. In vitro results highlighted increased functions of neural stem cells and neurons while at the same time decreased functions of astrocytes on carbon nanofibers compared to currently implanted electrode materials. Moreover, directed axonal extension from neurons was achieved in vitro along aligned carbon nanofiber/nanotube patterns created on polymer surfaces. Lastly, due to promising in vitro data, carbon nanofibers/nanotubes impregnated with stem cells were implanted into rat brains which possessed damage (i.e., a transient focal ischemia). Specifically, middle cerebral artery occlusions (MCAO) were created in rat brains by using a well established left intraluminal vascular occlusion procedure for 60 minutes. At that time, stem cells placed into carbon nanofibers/nanotubes were implanted into the damaged neural tissue for up to 8 weeks. After the end of the prescribed time periods, healing of damaged neural tissue was measured from histological sections and T2 weighted magnetic resonance (MR) imaging. Importantly, histology pictures demonstrated the differentiation of stem cells around the implanted carbon nanofibers/nanotubes into neurons which reestablished neural activity in the damaged area of the rat cerebral cortex. Such data highlights the promise carbon nanofibers/nanotubes have in healing brain damage that may occur due to a number of pathological situations (such as stroke, Parkinson’s disease, Huntington’s disease, etc.).
12:15 PM - R1.8
Enhancement of Antibody Binding on SiO2 Love Wave Sensor Surface using (3-glycidoxypropyl)trimethoxysilane.
Nicolas Moll 1 , Duy Hai Dinh 1 2 , Emilie Pascal 1 3 , Corinne Dejous 1 , Jean-Paul Pillot 2 , Bernard Benneteau 2 , Dominique Rebiere 1 , Daniel Moynet 3 , Djavad Mossalayi 3 , Jacques Pistre 1
1 , Laboratoire IXL, Talence France, 2 , Laboratoire de Chimie Organique et Organometallique, Talence France, 3 , Laboratoire d'Immunologie et de Parasitologie, Bordeaux France
Show Abstract12:30 PM - R1.9
Particle and Pore Size Dependence of Proteinase K Diffusion Through Sol-Gel Derived Silica.
Winny Dong 1 , Weijen Lin 2 , YiHsuan Lin 2 , Doja Elmatari 1 , Nicole Contreras 1 , Maria Torres 1 , Sheridan Vo 1
1 Chemical and Materials Engineering, California State Polytechnic University, Pomona, Pomona, California, United States, 2 Biological Sciences, Cal Poly Pomona, Pomona, California, United States
Show Abstract This study examines the influence of microscale particle size and nanoscale pore size on the diffusion of Proteinase K through sol-gel derived silica. The ability to control and predict the diffusion rates of enzyme through silica microparticles may be useful in designing controlled drug-delivery systems. Enzyme-doped silica gels were dried via supercritical drying (aerogels), low surface-tension solvent exchange (ambigels), and ambient evaporation of the water/alcohol byproducts (xerogels). This resulted in silica with three different microstructures and pore sizes: aerogels (pore diameter on the order of 20 nm), ambigels (20-50 nm), and xerogels (> 50 nm). Microparticles of the protein-doped silica were formed through grinding and the emulsion-method. Particle sizes tested were between 20 - 250 um. Silica xerogels, with the lowest overall porosity and largest pores showed the highest retention, highest amount of enzyme released, and the fastest release rates compared to silica aerogels and ambigels. The enzyme release rate is inversely proportional to particle size and directly proportional to incubation temperature. The emulsion method also showed better retention of enzyme compared to the ground samples. Recent data suggests that the microstructure of xerogels do a better job at stabilizing the enzyme than ambigels and aerogels.
12:45 PM - R1.10
Selective Detection of Chemical Warfare Agents Based on Semiconductor Metal Oxides and Polymer Coated Surface Acoustic Waves.
Chuncai Yang 1 , Guizhen Feng 1 , Brent Marquis 1
1 , Sensor Research and Development Corporation, Orono, Maine, United States
Show AbstractThe selectivity, sensitivity and repeatability/reproducibility of semiconductor metal oxides (SMOs) and polymer coated surface acoustic waves (P-SAWs) for the detection of chemical warfare agents (CWAs) will be reported. In general, the unmodified SMOs such as WO3, SnO2, and In2O3, etc. have high sensitivity and their detection limits can be up to 10 ppb toward CWAs, however, they lack selectivity to the detecting target on interfering environments. Our report will be focused on several novel types of SMOs and their hybrid sensing materials, which have significantly increased their selectivity toward the detecting target such as sulfur mustard simulent, 1,5-dichloropentane (DCP) and Nerve agents’ simulent, dimethyl methylphosphonate (DMMP) on existing interfering chemicals such as hexane, diesel, and methanol, etc. P-SAWs are another type of detecting technologies for CWAs detection, in this report, we will demonstrate how to make reproducible P-SAWs sensors (sensor to sensor and batch to batch), to decrease the baseline drift, and to increase the density of coated polymers on SAW surface for increasing their sensitivity (up to 300 KHz frequency change for 10ppm DMMP detection and with 100ppb detection limit to Sarin (GB) and VX) based on our developed novel polymers, surface reaction and surface assemble technologies.
R2: Biotechnology
Session Chairs
Bruce Dunn
Vincenzo Guidi
Tuesday PM, April 18, 2006
Room 3022 (Moscone West)
3:15 PM - R2.2
Electro-sculpting for Tissue and Organ Engineering.
Dong Han 1 , Pelagia Gouma 1
1 Materials Science and Engineering, Stony Brook University, The State University of New York, Stony Brook, New York, United States
Show Abstract3:30 PM - R2.3
The Use of Superparamagnetic Nanoparticles as Labels in Immunoassays.
Peter Hawkins 1 , Richard Luxton 1 , Janice Kiely 2 , Jasvant Badesha 1 , Patrick Wraith 2 , Jackie Barnett 1 , John Eveness 1
1 Faculty of Applied Sciences, University of the West of England, Bristol United Kingdom, 2 Faculty of Computing, Engineering and Mathematical Sciences, University of the West of England, Bristol United Kingdom
Show AbstractImmunoassays rely on the rapid and specific interaction between an antibody and its antigen (analyte)and have found many applications in such diverse areas as medical diagnosis, food quality assurance, environmental monitoring, agriculture and national defense. The assay is usually quantified via a label such as gold particles, enzymes or radioactive, fluorescent or chemiluminescent molecules attached to the antibody. In the well-known pregnancy test, the antibody labeled with blue, micrometer-sized latex particles reacts with the pregnancy hormone and the combination then produces a blue line when the antigen reacts with a line of immobilized secondary antibody. A recent development is the use of micro- and nanometer-sized magnetic particles (PMPs) as labels which have cores of a superparamagnetic material, coated usually with a polymer layer to which the antibody attaches via a linker molecule. We have used PMPs as labels in sandwich assays and the number of immobilized PMPs quantified using a resonant coil magnetometer (RCM) of our design. Techniques that have been developed by others to quantify the PMPs include magneto-resistive devices and magnetic induction. In one version of our device, secondary antibody is immobilized in a reaction surface on one side of a small ceramic chip with a flat spiral sensing coil of the RCM deposited using thick film technology immediately opposite on the other side. PMPs become immobilized in a sandwich assay on the reaction surface and their presence causes a decrease in the resonant frequency of the coil (from about 30MHz) that is directly related to the number of PMPs. We have found that the reaction times for assays are considerably reduced when an external magnetic field is used to pull the combined PMPs and antigen to the surface so that a reaction is more likely to occur. It is also unnecessary to remove excess PMPs because immobilized PMPs have a stronger effect on the RF field created by the sensing coil as their induced magnetic dipoles are also orientated in the external field whereas the directions of the induced dipoles in the unbound PMP are randomized by Brownian motion, and as the sensitivity of the sensing coil falls rapidly with distance, excess PMPs still in suspension also have less effect. We will report on our investigations into the magnetic properties of PMPs that give the best performance. Two or more analytes can be analyzed simultaneously and we have developed a system that measures the concentrations of the cardiac markers CRP and CKMB in whole blood in 4 minutes with no sample preparation. This work will lead to a simple bench-top or handheld device.The familiar pregnancy test is an example of a simple lateral flow device with a result that is either yes or no. We have adapted our system to a lateral flow format that gives a much wider quantitative range and have developed a device capable of measuring the concentrations of the prostate cancer marker PSA in plasma samples.
3:45 PM - R2.4
Quantitative Detection Using Porous Silicon Biosensors.
Huimin Ouyang 1 2 , Philippe Fauchet 1 2
1 Electrical and Computer Engineering, University of Rochester, Rochester, New York, United States, 2 Center for Future Health, University of Rochester, Rochester, New York, United States
Show Abstract4:30 PM - R2.5
GaN Nanowires: A New Material for Optical and Electrochemical Sensing of DNA.
Chinpei Chen 1 , Abhijit Ganguly 1 , Li-Chyong Chen 1 , Kuei-Hsien Chen 2
1 Center for Condensed Matter Science, National Taiwan University, Taipei Taiwan, 2 Institute of Atomic & Molecular Sciences, Academia Sinica, Taipei Taiwan
Show AbstractGroup-III nitride semiconductors are quite popular, especially, in optoelectronic application. In last few decades, tremendous interest has been aroused towards the growth and application of III-nitride materials, especially, in 1-D structure. Beside their unique optoelectronic properties, these nitride systems are also well known for their non-toxicity and biocompatibility, however their application in bio-world is truly ignored until date. On the other hand, in DNA-sensor application, search for a suitable transducer-material is still a big challenge. No single characterization technique is complete; and, for a better understanding of any material system, both optical and electrical techniques have been proved to be complementary to each other. This leads to a concept of a complete-sensor, and a promising bio-application of GaN, which may be the first transducer-material for DNA-sensor in both optics- and electronic-based sensor-application. In this report, single-stranded DNA (ss-DNA) molecules were immobilized on GaN nanowires (NWs) through covalent binding. The ss-DNA-immobilization on GaN NWs surface shows a huge change in electrochemical (EC) property, indicating an increase in impedance due to the surface-modification. On the other hand, GaN, a direct and wide band-gap material, shows a remarkable change in its emission properties (photoluminescence, PL) due to the change in surface-properties. Same DNA-GaN NWs system could be subjected to both PL and EC characterizations. Moreover, the interaction between ss-DNA, immobilized on GaN surface, and its complementary base-pairs can be observed, distinctly, by both PL and EC techniques. This fact that GaN is sensitive to the immobilization of DNA bases and can promote the formation of complementary base-pairs, leads to a possible biosensor based on GaN NWs.
4:45 PM - R2.6
Development of a Template-Directed Nanotube Array Gas Sensor Platform for Biosensing Applications
Kurt Benkstein 1 , Christopher Montgomery 1 , Richard Cavicchi 1 , Steve Semancik 1 , Michael Tarlov 1
1 Chemical Science & Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractWhile Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) are known to be intra- and extra-cellular transducers in mammalian cells, the use of these molecules as biomarkers of cell response has been hindered by measurement difficulties associated with their low concentrations and the complex chemistry present upon release from cells. Toward the goal of measuring these potential biomarker molecules at the cell, we are developing a novel sensor platform to overcome the problems connected with the low concentrations and rapid reactivities of the target species. In order to achieve sufficient functionality to detect, for example, gas-phase NO in liquid media, a sensor platform must properly combine thin sensing films, nanoscale porous structure and compatible electrical contacts (i.e., compatible to both the active sensing material and the bio-active environment). This new conductometric sensor platform is based upon a porous nanotubular array membrane support structure. The large internal surface area realized for these nanostructured arrays serves as a template for thin metal oxide sensing films with enhanced sensitivity. Furthermore, the platform design facilitates incorporation of the sensor into the cell-growth medium, thus enabling proximal detection of ROS and RNS. In this presentation, we describe a research prototype that features an array of high-surface-area WO3 nanotubes (d = 200 nm, l = 60 μm) supported in an anodically etched alumina membrane, prepared via sol-gel chemistry. The nanotube arrays have been characterized electrically and by scanning electron microscopy and energy dispersive x-ray spectroscopy. Metal contact pads have been deposited at the top and bottom of the oxide-coated membrane to enable good electrical connection, while also permitting analyte diffusion into the pores of the sensor. Sensing experiments on volatile small molecules are also described to demonstrate the viability of the approach.
5:00 PM - R2.7
Gas-Sensor Cantilevers Synthesized from Ni-V-Zr Nanocomposites.
Reza Mohammadi 1 , Colin Ophus 2 , Larry Kostiuk 1 , Stephane Evoy 3 , Ken Westra 3 , Lee M. Fischer 3 , Yongliang Wang 4 , Velimir Radmilovic 4 , ZongHoon Lee 4 , Ulrich Dahmen 4 , David Mitlin 2
1 Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada, 2 Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada, 3 Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada, 4 Lawrence Berkeley Lab, National Center for Electron Microscopy, University of California at Berkeley, Berkely, California, United States
Show AbstractWhile Ni films have been used in a variety of magnetic and MEMS devices, they have had limited applications in the area of cantilever-based sensing. Though having several advantages over insulators and semiconductors, metals are notoriously difficult to pattern or release due to their high stress state, large surface roughness and low strength. The aim of this work is to describe the mechanical properties, the microstructure, and the device applications of Ni-V-Zr ternary alloy nanocomposite thin films. We fabricated a range of compositions and microstructures by co-sputtering from Ni-V and pure Zr targets. Nanoindentation tests indicate that the hardness of the fabricated materials is significantly higher than that of conventional Ni-based films. In addition, Ni-V-Zr nanocomposites are under less stress and are almost an order of magnitude smoother compared to pure Ni or binary alloys. The properties of the nanocomposites are discussed in relation to the materials’ thin-film growth mechanism, grain size, crystal structure and grain orientation (we performed TEM, SEM, AFM and XRD analysis). As proof of principle, we synthesized free-standing functionalized nano-scale cantilevers, which have the potential to be used as gas sensors in harsh or elevated temperature environments.
5:15 PM - R2.8
Localized Surface Plasmon Biosensor Using Ag Nanostructured Films Fabricated by a Reduction Method.
Tomofumi Arai 1 , Penmetcha Kumar 2 , Koichi Awazu 1 , Junji Tominaga 1
1 Center for Applied Near-Field Optics Research (CAN-FOR), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan, 2 Functional Nucleic Acids Group, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan
Show AbstractThe phenomenon of localized surface plasmon resonance (LSPR) has been attracting much attention for a highly sensitive and label-free biosensing method. Recently, we have developed a novel fabrication method of Ag nanostructured films indicating a strong LSPR by the reduction of AgOx thin films using reactive ion etching [1]. This fabrication technique possesses several advantages over other methods as follows: (i) a uniformly Ag nanostructured surface is obtained on large area (> 100 cm2); (ii) no additional heating is required; and (iii) only several minutes are needed for the reduction of the AgOx, and these advantages enable a reliable mass production of nanostructured Ag films and indicate a large potential for providing cost-effective LSPR biosensors. AgOx thin films with a thickness of 50-100 nm were deposited by reactive rf sputtering on Si wafers. The deposited AgOx thin films were reduced to Ag using the reactive ion etching with a gas flow of CF4, O2 and H2 for about 1 minute as an initial etching process, and then with a gas flow of O2 and H2 for several minutes as a second etching process. From scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (TEM), it was found that Ag nanoparticles with a diameter of about 20 nm were formed during the initial etching, and the nanoparticles were developed into the nanostructures during the second etching. The reflectance spectra of the Ag nanostructured films showed a distinctly low reflectance around 390 nm in air due to the localized surface plasmon resonance of the Ag nanoparticles. The wavelength shift of LSPR for the Ag nanostructured films was found to show a linear dependence with a high correlation coefficient (>0.99) on the refractive index of the surrounding materials, which was conformed using different kind of solvents such as water (n=1.333), ethanol (n=1.361) or pyridine (n=1.508). Thus, the Ag nanostructured films can be applied to a LSPR biosensor which detects specific absorptions of a minute quantity of biomolecules on the surface of the Ag nanostructured films by monitoring the wavelength shift of the LSPR. Next, we investigated the ability of this LSPR biosensor for detecting the binding events between streptavidin and biotin molecules, which were immobilized at the surface of the Ag nanostructured films via Ag-thiol bonds. We have found that the LSPR biosensor has an ability to detect interactions at about 100 nM of streptavidin.[1] J. Tominaga, J. Phys.: Condens. Matter 15, R1101 (2003).
5:30 PM - R2.9
Studies on Biosensing Property and Functionalization of In2O3 and Carbon Nanotube Field Effect Transistor.
Chao Li 1 , Fumiaki Ishikawa 1 , Tao Tang 1 , Chongwu Zhou 1
1 , USC, Los Angeles, California, United States
Show AbstractBiosensors based on one-dimensional nanostructure materials, such as metal-oxide nanowires (NWs) and carbon nanotubes (CNTs), are attracting considerable attention due to their superior performance in terms of sensitivity, response time, and label free detection. Such sensors are expected as next disease diagnosing or drug screening tools, which are highly relevant to our ordinal life. In this context, we firstly inspected the biosensing properties of In2O3 NW and CNT field-effect transistors (FET) toward low-density lipoproteins (LDLs), an important marker to detect individuals at risk for cardiovascular disease. Complementary sensing responses between the NW and the CNT FET have been observed after exposure to LDLs particles, with the enhanced conductance for the NW and the reduced conductance for the CNT. Secondly, we performed the real-time prostate-specific antigen sensing, which is an oncological marker to detect the presence of the most frequently diagnosed cancer among men in the US, the prostate cancer. We observed selectivity from bovine serum albumin (BSA), and high sensitivity up to 5ng/ml with the NW and 50ng/ml with the CNT respectively. Finally, to implement dense arrays of nanosensors with multiple probe molecules, we studied the selective functionalizations of ITO films and In2O3 NWs with a DNA single strand by utilizing the electrochemical switching of the linker molecule between quinone and hydroquinone. The selective immobilization of the complementary DNA single strand via the DNA double strand formation, as confirmed by the fluorescence study, revealed the successful selective functionalization of ITO films and NWs.
5:45 PM - R2.10
Integrated Conducting Polymer Nanowire Devices for Biological Sensing Applications
Adelaja Arojuraye 1 , Shaun Filocamo 3 , Catherine Klapperich 1 2 , Mark Grinstaff 1 3 , Unlu Selim 4
1 Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States, 3 Department of Chemistry, Boston University, Boston, Massachusetts, United States, 2 Manufacturing Engineering, Boston University, Boston, Massachusetts, United States, 4 Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts, United States
Show AbstractWe have fabricated an integrated device incorporating micro and nanoscale components. The microscale structures were fabricated on semiconducting surface by patterning and depositing simple metal structures on silicon substrates. The structures include planar microscale electrodes separated by an insulating area. This structure allows the nanowires to be easily probed. Nanoscale wires were “written” on the microscale structures using AFM electrochemical dip pen nanolithography (e-DPN). The tip of the AFM is dipped into a solution of monomer, and then the tip is pulled along the surface while a potential is applied between the tip and surface. Wires less than 10nm thick and wide can be drawn 1-2 microns in length. Each wire can be precisely placed and lies between two electrodes. We have characterized these devices using imaging AFM and Raman spectroscopy. We have also made conductivity measurements. We have used these integrated devices to investigate the properties of polymer nanowires of polypyrrole, polyaniline, and poly(ethylenedioxythiophene). Additionally, we have conjugated the monomers used to fabricate the polymer nanowires with biotin. Wires fabricated from these monomers can bind avidin and streptavidin in solution. Conducting polymers conjugated with biological ligands have the potential to detect specific binding events to detect biological agents or pathogens or an array of environmental toxins. Optimization of processing techniques will allow for more precise measurements and provide a foundation for future integration of nano and micro scale technologies involving conducting polymers.
R3: Poster Session: Organic Materials for Sensing and Biotechnology
Session Chairs
Elisabetta Comini
Pelagia Gouma
Wednesday AM, April 19, 2006
Salons 8-15 (Marriott)
9:00 PM - R3.1
Molecularly Imprinted Polymers and Pathogens' Specific Binding and Detection.
Chuncai Yang 1
1 , Sensor Research and Development Corporation, Orono, Maine, United States
Show AbstractThe surface molecularly imprinted polymers (MIPs) for water-born pathogens’ specific binding and detection will be reported based on various synthetic methods. Among them, light initiated polymerization of acrylic monomers for MIPs is most efficient. Our experiments demonstrate that the composition of MIPs is critical for a bacterium’s specific binding on the imprinted recognition sites. The density and orientation of imprints play a major role on the pathogens’ binding efficiency. A novel approach on how to imprint, remove and bind pathogens on MIPs has been developed. The scanning electron microscope (SEM) has been used to study the surface imprinted recognition sites and the subsequent pathogens’ binding on them. The washing procedure and fluorescent optical microscope have been used to distinguish the specific binding of pathogens from non-specific binding of pathogens on MIPs and non-MIPs control polymers. The testing results from SEM and fluorescent optical microscope have clearly proved that the specific binding is different from the non-specific binding and the specific bound pathogens are sat on the impressions/imprinted sites. The study of repeatable binding on the same MIPs and the reproducibility (MIPs to MIPs, batch to batch) indicates that surface molecularly imprinted polymers for water-born pathogens’ specific binding is efficient and Biosensors (MIPs coated on quartz crystal microbalance (QCM)) based on MIPs are cheap, easy and robust.
9:00 PM - R3.10
Non-Aqueous Single Step Electrodeposition of Nanowires of Cadmium Zinc Telluride (CZT) for Radiation Sensing
Thulasidharan Gandhi 1 , Krishnan Raja 1 , Manoranjan Misra 1
1 Material Science and Metallurgical, University of Nevada, Reno, Reno, Nevada, United States
Show AbstractA single step non-aqueous electrodeposition process for synthesis of nanowires of CdZnTe (CZT) compound semiconductor has been developed. Using this process nanowires of CZT were grown on a self-ordered nanotubular titanium oxide template. Propylene carbonate was used as the non-aqueous medium. Composition and structure of the nanowires of CZT were characterized by scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDX), X-ray diffraction (XRD) and optical absorption spectroscopy. The EDAX measurements showed Cd 0.96 Zn0.04 Te. XRD measurements proved the formation of compound CZT. The nanowires showed a band gap of around 1.7 eV. The electrical resistivity of the compound was greater than 10^9 ohm-cm. Further, to have a better understanding of the formation of ternary compound, different process parameters such as: bath temperature, deposition potential, pulse time and concentration of Cd/Zn ions are varied and the nanowire products are being characterized.
9:00 PM - R3.11
Self-Assembly Of Gold And Silver On Polystyrene-Polymethyl-Methacrylate Diblock Copolymers And Its Application To Surface Enhanced Raman Spectroscopy.
Alec Talin 1 , Blake Simmons 1 , Eric Majzoub 1 , Richard Anderson 1 , William Tong 2 , Zhiyong Li 2
1 , Sandia National Labs, Livermore, California, United States, 2 , HP Labs, Palo Alto, California, United States
Show AbstractWe investigate the growth of Au and Ag metals on PS-PMMA diblock copolymers and the application of the resulting metal-on-polymer films for Surface Enhanced Raman Spectroscopy (SERS). PS-PMMA self-assembles into a highly ordered morphology with feature dimensions in the tens of nanometers and geometries that include lamellae or hexagonally arranged cylinders of PMMA in a PS matrix. In our work we use these polymer surfaces as scaffolding for subsequent assembly of Au and Ag films. We find that evaporated Au self assembles into highly ordered patterns that closely match the underlying lamellae or hexagonal cylinder polymer morphology even up to a thickness of 20 nm. Ag, on the other hand, coalesces into islands with little apparent ordering. These differences translate into very distinct plasmon extinction and SERS characteristics for the metal-on-polymer films.
9:00 PM - R3.12
Carboxylated Carbon Nanotube assisted Hydroxyapatite Synthesis from Simulated Body Fluid.
Hak Yong Kim 1 , Santosh Aryal 2 , Shanta Bhattarai 2 , K.C. Remant 2 , P. Prabu 2 , N. Dharmaraj 3
1 Textile Engineering, Chonbuk National University, Chonju 561-756 Korea (the Republic of), 2 Bionanosystem Engineering, Chonbuk National University, Chonju 561-756 Korea (the Republic of), 3 Chemistry, Government Arts College, Udumalpet 642 126 India
Show Abstract9:00 PM - R3.13
Fabrication of Nanocomposites Using Highly Ordered Anodic Porous Alumina and Its Application to Ordered Arrays of Biomolecules
Masahiro Harada 1 , Futoshi Matsumoto 2 , Kazuyuki Nishio 1 2 , Hideki Masuda 1 2
1 Department of Applied Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo, Japan, 2 , Kanagawa Academy of Science and Technology, Sagamihara, Kanagawa, Japan
Show AbstractFabrication of ordered, fine structures of nanometer dimensions using anodic porous alumina, which has a naturally occurring ordered porous structure, has attracted growing interest for the development of several types of nanodevices. There have been many reports on the preparation of nanocomposites devices using anodic porous alumina as a host material. These nanocopsites device of porous alumina can be applied to the functional nanodevices, such as functional electrode array and high density arrays of functional biomolecules and so on. In this work, we describe fabrication processes of ordered metal disk arrays using highly ordered anodic porous alumina. The obtained ordered arrays of metals or semiconductors were applied for the preparation of functional nanodevices, such as nanodisk electrode arrays, or ordered arrays of biomaterials.
9:00 PM - R3.14
Redox Reactions of Bio Molecule for Nano-bio Battery
K. M. Shin 1 , S. J. Park 1 , S. G. Yoon 1 , C. K. Lee 1 , S. R. Shin 1 , B. K. Gu 1 , M. S. Kim 1 , M. K. Shin 1 , S. J. Kim 1
1 Dept. of Biomedical Engineering, Hanyang University, Seoul Korea (the Republic of)
Show AbstractMetal oxide nanoparticles, the ferritin protein can act as an energy storage source in nano-bio batteries containing ferrous ferritin and a reconstituted ferritin cage with different inorganic elements, such as Co, Mn, Ni, and Pt. These were introduced as two ferritin half-cells with different redox potentials between the ferrous ferritin and the reconstituted ferritin. It is important to analyze the reduction and oxidation reactions of ferritin, because redox reactions are intimately involved in both the oxidation of Fe, which occurs during Fe storage, and the reduction of Fe, which is involved in Fe release. In vitro experiments have suggested that, once the core iron is reduced, the iron ions can exit the protein shell, and then can re-enter with phosphate ions. An understanding of ferritin redox reactions is an important component in elucidating the mechanism of iron loading and unloading.In this work, the reduction of ferritin analyzed in a solution composed of 3-[N-morpholino]propanesulfonic acid-buffered containing oxidized methyl viologen using cyclic voltammetry. Electrochemical analysis showed that oxidized methyl viologen was changed into reduced methyl viologen using an applied potential, and that the HoSF was reduced by the reduced methyl viologen formed. The reduction and oxidation peaks of the methyl viologen appeared at potentials around –700 and –600 mV, respectively, and the reduction and the oxidation peaks of the released Fe appeared at potentials around –300 and –100 mV, respectively. The reduction of HoSF was influenced by the pH of the ferritin solution and a pH = 7.5 ferritin solutions was optimum for reducing HoSF.
9:00 PM - R3.15
Quick and Sensitive Magnetic Separation of Oligonucleotide with Gold/Magnetic Iron-oxide Composite Nanoparticles
Takao Yamamoto 1 , Takuya Kinoshita 1 , Satoshi Seino 1 , Takashi Nakagawa 1 , Takefumi Doi 2 , Tomoko Takano 2 , Shinsaku Nakagawa 2 , Masakazu Furuta 3 , Noriyuki Ohnishi 4
1 , Graduate School of Engineering, Osaka University, Suita, Osaka, Japan, 2 , Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan, 3 , Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, Japan, 4 , Magnabeat Inc, Ichihara, Chiba, Japan
Show AbstractWe have synthesized composite nanoparticles consisting of gold nanograins of a few nm immobilized on each substrate maghemite particle with an average diameter of 26 nm, and showed that these particles are useful for magnetic separation of functional biomolecules. We demonstrated that a target oligonucleotide was easily picked up from an aqueous solution by magnetically attracting these nanoparticels to which a probe oligonucleotide bonded. The probe was a thiol-modified oligonucleotide, 15-mer polythymine oligonucleotide, HS-5'-(T)15-3', and sulfur makes a firm bond with gold in the particles. The target oligonucleotide was 15-mer polyadenine oligonucleotide with a sequence complementary to the probe, which was labeled with fluoresceinisothiocyanate for detecting the targets magnetically retrieved, FITC-5'-(A)15-3'. Control experiments lacking for one of “gold grains”, “probe oligonucleotide” or “complementary sequence”, showed no fluorescence. We found that 0.75 nmol-oligonucleotide was picked up by 1-mg particles, and 15-30 minute was enough to saturate its amount. These nanoparticles were synthesized in an aqueous solution without using any detergent, and well dispersive in water. A reddish color of the dispersion, evidence of the occurrence of nanosized and dispersed gold grains, was observed with the naked eyes. The secondary particle size of the particles was 100 – 300 nm in water, and substantially no sedimentation occurs even after a day. The connection with the probe oligonucleotide was performed just by mixing two solutions at room temperature. This particle material should be a powerful tool for detecting a specific DNA/RNA sequence in vitro.
9:00 PM - R3.16
Application of Plasma Assisted Surface Technologies for the Construction of DNA and Protein Arrays.
Sanghak Yeo 1 , Changrok Choi 1 , Jaeyoung Yang 1 , Cheonmoon Park 1 , Heonyong Park 2 , Donggeun Jung 1
1 Physics, Sungkyunkwan university , suwon Korea (the Republic of), 2 molecular biology, Nanosensor and Biotechnology,, seoul Korea (the Republic of)
Show AbstractAbstractA plasma enhanced chemical vapor deposition (PECVD) method using plasma polymerized ethylenediamine (PPEDA) was employed to coat glass slides with amine functional groups. Fluorescein isothiocyanate (FITC) labeling indicated that the density of amine functional groups on these coated slides was affected by PECVD conditions, particularly deposition time. The PPEDA-coated slides were used for the development of DNA arrays. 5’-Amino-modified oligodeoxyribonucleotides (ODNs) and cDNA strands were immobilized onto PPEDA-coated slides and used for hybridization to labeled target strands.To immobilize proteins, plasma polymerized hexamethyldisiloxane (PPHMDSO) thin film was deposited onto the surface of glass slide. We modified PPHMDSO-coated glass slide by an additional oxygen plasma treatment with placing the patterned mask on the HMDSO-coated glass slide. Hydrophilic surfaces were detected by measuring the contact angle of water. Of great interest, proteins were strictly immobilized on the patterned O2 plasma treated areas, providing more efficient ways for fabricating the protein chips.These results demonstrate that PECVD and/or plasma surface treatment can be usefully used for the construction of DNA and protein arrays.
9:00 PM - R3.17
Sol-Gel Silica Films for DNA Microarray Applications
Kristjan Saal 1 2 , Margo Plaado 1 2 , Ilmar Kink 1 , Ants Kurg 1 3 , Uno Maeorg 1 2 , Ago Rinken 1 2 , Ants Lohmus 1
1 Lab. Of Low Temperatures, Institute of Physics, Tartu, Tatu, Estonia, 2 , Institute of Organic and Bioorganic Chemistry Tartu University, Tartu Estonia, 3 , Institute of Molecular and Cell Biology Estonian Biocentre, Tartu Estonia
Show Abstract9:00 PM - R3.18
Massive Assembly of Carbon Nanotube-Based Biosensor Arrays via “Surface-Programmed Assembly” Process.
Byung Yang Lee 1 , Jiwoon Im 1 , Minbaek Lee 1 , Dong Joon Lee 1 , Seunghun Hong 1
1 School of Physics and NANO Systems Institute, Seoul National University, Seoul Korea (the Republic of)
Show AbstractElectrical junctions based on carbon nanotubes (CNTs) have been drawing tremendous attention as highly-sensitive chemical or biological sensor components. However, a lack of reliable mass-production method for such junctions has been holding back their practical applications. One promising mass-production method for CNT-based junctions can be “surface-programmed assembly” process (Nature 425, 36 (2003)), where surface molecular patterns guide the ‘selective assembly’ and ‘precision alignment’ of carbon nanotubes on the substrate without using any external forces such as liquid flow, etc. Since this process does not require any high-temperature processing step, it can be applied to virtually general substrates. Using this method, we successfully demonstrated the fabrication of 256 x 256 carbon nanotube-based sensor arrays on both SiO2 and transparent thin glass substrates. Furthermore, by functionalizing the CNT junctions with enzyme L-glutamate oxidase, we demonstrated the selective detection of L-glutamate. Spectrophotometric analysis shows that the immobilized enzymes retain their activity after our process. AFM images show that enzymes are immobilized both in between and along the CNTs. These sensor arrays could be utilized in the field where the real-time detection of L-glutamate is needed such as in neurobiology or food industry.
9:00 PM - R3.19
A Laser Based, Solvent-free Technique for Depositing Functionalized Nanostructures.
Michael Papantonakis 1 , Eric Houser 1 4 , Chris Kendziora 1 , Erik Herz 2 , Ulrich Wiesner 2 , Richard Haglund 3 , Stephen Johnson 3 , R. McGill 1
1 Materials Science and Technology Division, US Naval Research Laboratory, Washington, District of Columbia, United States, 4 , Transportation Security Research & Development Laboratory, Atlantic City International Airport, New Jersey, United States, 2 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 3 Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, United States
Show Abstract9:00 PM - R3.2
Fabrication of Biocompatible Nanocapsules by Mineralization of Polymer Nanocages with Calcium Phosphate.
Kris Perkin 1 , Jeffrey Turner 2 , Karen Wooley 2 , Stephen Mann 1
1 Centre for Organized Matter Chemistry, University of Bristol, Bristol United Kingdom, 2 Chemistry, Washington University in St Louis, St Louis, Missouri, United States
Show Abstract The formation of self-assembled core-shell structures with nanoscopic dimensions offers exciting applications in fields such as imaging and therapeutics. This study demonstrates that a class of these structures, polymer shell cross-linked nanocages (NC), may be coated with an ultra thin shell of calcium phosphate. This natural mineral gives the NC added robustness and biocompatibility. Fabrication of these structures was achieved by first forming micelles with the diblock copolymer poly(acrylic acid)-b-poly(isoprene) (PAA-b-PI). The PAA outer shell was 22% cross-linked using a diamino crosslinker leaving NC ~60nm in diameter as measured by light scattering, transmission electron microscopy and AFM. The carboxyl groups present in PAA were utilised to electrostatically sequester Ca2+ ions into the surface of the NC. Addition of HPO42- ions induced mineralization and various techniques (EDXA, FT-IR and SAED) established that the mineral formed was amorphous calcium phosphate. UV-vis studies followed the concentration of a drug, beta-carotene, being absorbed into the hydrophobic isoprene core and showed that the inorganic shell had a large effect on the permeability of the NC. Thus, the coated nanocages were shown to have promise as biocompatible nanocapsules for drug delivery applications.
9:00 PM - R3.20
Electrical Properties of DNA-Nanoparticle Networks Using Electric Force Microscopy Analysis
Yu-Jin Kim 1 , N. J. Lee 1 , J. S. Kim 2 , B. H. Nam 2 , Y. S. Kim 3 , C. J. Kang 1
1 Physics and Nano-Bio Research Center, Myongji University, Yongin, Gyonggido, Korea (the Republic of), 2 Biological Science and Nano-Bio Research Center, Myongji University, Yongin, Gyonggido, Korea (the Republic of), 3 Electrical Engineering and Nano-Bio Research Center, Myongji University, Yongin, Gyonggido, Korea (the Republic of)
Show AbstractThe electrical properties of DNA-nanoparticle networks constructed by the self-assembly of biotinylated DNAs and streptavidins(STVs) are investigated using the scanning probe microscopy. Firstly, we built mono-, di- and trivalently networked DNA structure through the ratio regulation of DNA and streptavidin complexes and then its local electrical property was measured. It is well known characteristics that the conformational change affects the electrical properties of DNA. So we treated the surface of the mica substrate with Ni2+ ion to give a mechanical compression to the deposited DNA. As ion concentration increases, physical height of DNA decreses due to the stronger interaction between DNA and the substrate and more supercoiled DNAs were found. This is caused by the compensation of negatively charged DNAs by the positve metal ions. In this talk, using spectroscopy and observed images, the results analysed on the local electrical properties of DNA-nano particle networks related to their structural and inter molecular configuration will be presented.
9:00 PM - R3.22
Hydrogen Detection Using Polyaniline Nanofibers
Shabnam Virji 2 , Bruce Weiller 2 , Richard Kaner 1
2 Materials Processing and Evaluation, The Aerospace Corporation, El Segundo, California, United States, 1 Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractHydrogen is a clean energy source and sensors are needed for measuring the hydrogen concentration below the lower explosion limit in air of 4%. Polyaniline nanofibers are synthesized using a template-free rapid polymerization method. We have previously shown that the nanofibers respond well to a number of different gases including acids, bases, organic solvents, and redox active agents with resistance changes of over 8 orders of magnitude. Here we show that polyaniline nanofibers respond to hydrogen gas at room temperature with a small increase in conductivity. The suggested mechanism involves the dissociation of hydrogen and interaction with the amine nitrogen of the polyaniline chain. The response to hydrogen of doped and dedoped polyaniline nanofibers will be presented along with data on nanofiber composite films. The effect of humidity, oxygen, and deuterium on the sensor response will be presented and discussed in light of the proposed mechanism for hydrogen interaction with polyaniline nanofibers.
9:00 PM - R3.23
Self-assembled Porphyrin Nanostructures.
Roberto Paolesse 1 , Donato Monti 1 , Sara Nardis 1 , Corrado Di Natale 2 , Arnaldo D'Amico 2
1 Chemical Science and Technologies, University of Rome Tor Vergata, Rome Italy, 2 Electronic Engeenering, University of Rome tor Vergata, Rome Italy
Show Abstract9:00 PM - R3.24
Atomistic Study of Catalytic Growth of Carbon Nanotubes
Wei Xiao 1 , Mike Baskes 2 , Kyeongjae Cho 1
1 Mechanical Engineering, Stanford University, Stanford, California, United States, 2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractIn chemical vapor deposition (CVD) growth of carbon nanotubes (CNTs), metal nanoparticle catalysts are used as seeds for nanotube growth. During the CVD growth, hydrocarbon molecules (e.g., CH4) are catalytically reduced on the metal catalyst surface, and C atoms are deposited on the metal catalysts. This continuous supply of C atoms onto the catalyst nanoparticle over saturates the carbon in the metal and leads to a precipitation of a solid carbon structure on a part of the catalyst particle surface. Even though the research community generally knows these CVD growth processes of CNTs from metal nanoparticles, the detailed atomic processes during the CVD growth are not currently well understood. Specifically, the initial nanotube cap formation from the precipitation of oversaturated carbon in the metal nanoparticle is an important process to understand since the chirality of subsequently grown CNTs is determined from the initially formed cap structure. In this study, we have applied a modified embedded atom method (MEAM) potential to investigate the CNT growth from Ni nanoparticle catalysts. Carbon and Ni MEAM potential parameters and their cross potential parameters are carefully developed to simulate the growth process. Molecular dynamic simulations are used to examine the detailed atomistic processes of carbon nanotube growth from the Ni nanoparticle catalyst under diverse growth conditions.
9:00 PM - R3.25
Simple Detection of Binding Events Using an Anchoring Transition of Liquid Crystals on the Immobilized oligoDNAs.
Hak-Rin Kim 1 , Min-Geon Choi 1 , Joo-Eun Kim 1 , Jae-Hoon Kim 1 , Eui-Yul Choi 2 , Sang-Wook Oh 3
1 Department of Electronics and Computer Engineering, Hanyang University, Seoul Korea (the Republic of), 2 Central Research Institute of Boditech Inc. and Department of Genetic Engineering, Hallym University, Chunchon, Kangwon-Do Korea (the Republic of), 3 Department of Biology Education, Chonbuk National University, Jeonju, Jeonbuk Korea (the Republic of)
Show Abstract9:00 PM - R3.26
Patterning Substrate-templated Membrane Morphologies by Triton-X.
Nathanael Rosidi 2 , Michael Howland 1 , Annapoorna Sapuri-Butti 3 , Atul Parikh 3
2 Biomedical Engineering, University of California - Davis, Davis, California, United States, 1 Chemical Engineering, University of California - Davis, Davis, California, United States, 3 Applied Science, University of California - Davis, Davis, California, United States
Show Abstract9:00 PM - R3.27
Organic Semiconductor-based Flexible Thin-film Water Vapor Sensors for Real-time Monitoring of Plant Transpiration.
Satoshi Hoshino 1 , Manabu Yoshida 1 , Toshihide Kamata 1
1 Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki Japan
Show AbstractTo enable highly sensitive and real-time monitoring of plant transpiration directly from leaves, we have developed novel water vapor sensors, which are thin and flexible so as to make it possible to attach closely on the leaf surface. We employed microporous polymer membranes and a moisture sensitive polymer semiconductor with n-alkyl side-chain groups for the sensor fabrication. The thin and microporous film structure modified by adsorption of the polymer semiconductor provides a hydrophobic environment that prevents retention of the evaporated moisture inside and serves for efficient transport of the water vapor across the membrane. Thus the transpiration can be detected by the electrodes formed on the top surface of the sensor membrane through amperometry of the adsorbed moisture sensitive organic semiconductor. We confirmed that the sensor with an optimal device configuration showed a synchronous variation in output current around 10-10~10-9 A at 2 V for a change in the low-level transpiration rates ranging from 5 to 10 mmol/m2sec determined with a commercial transpiration meter (Delta-T Device AP-4 porometer), and enabled real-time monitoring of the transpiratinal variation. The sensor also had superior sensitivity to the porometer in regard to the measurement of the very low-level transpiration. We believe that these water vapor sensors, which have a suitable device configuration for low-cost and large-scale fabrication by printing technologies, will be useful for developing a transpiration monitoring system used in the field of precision agriculture based on irrigation control.
9:00 PM - R3.28
Polyaniline-Cellulose Acetate Hybrid System for Chemical Sensing
Aisha Bishop 1 , Elisabetta Comini 2 , Pelagia-Irene Gouma 1
1 Materials Science and Engineering, SUNY Stony Brook, Stony Brook, New York, United States, 2 Dept. of Chemistry & Physics, INFM Unita de ricerca di Brescia, Brescia Italy
Show AbstractLeucoemeraldine (LEB) is the reduced form of polyaniline (PANI) which has not been explored for sensing applications due to its insulating and unstable nature. Hybrid systems of LEB-PANI have shown to aid in the stability of the material yielding an active matrix for gas sensing. The electrospinning technique has been employed for preparation of PANI-cellulose acetate (CA) hybrid structures. Electrical resistance measurements reveal that the inherently insulating polymer matrix exhibits elevated conductivity upon exposure to NO2 and humidity and thus can serve as a candidate for NO2 and humidity sensing. This paper will address the sensing mechanism and stability of the PANI-CA film.
9:00 PM - R3.29
Sensitivity Enhancement of Reflective Interferometric Spectroscopy for Label-Free Biomolecular Detection
Jinghui Lu 1 , Tingjuan Gao 2 , Lewis Rothberg 2 1
1 Chemical Engineering, University of Rochester, Rochester, New York, United States, 2 Chemistry Department, University of Rochester, Rochester, New York, United States
Show AbstractState-of-the-art sensor devices, as efficient tools for disease diagnosis and prevention, environment monitoring, security investigation, food safety and so on, are in demanding needs and playing more and more significant roles in human life. We report a novel imaging technique with which we developed an advanced sensor for fast detection of label-free DNAs, RNAs, viral and bacterial pathogens qualitatively and quantitatively. Termed Reflective Interferometric Spectroscopy (RIS), our technique is based on removal of the destructive interference in the reflected intensity from an anti-reflection coated silicon substrate. Surface thickness variation that results from binding of target molecules can therefore be accurately measured. Our previous result demonstrated detection of short DNA oligonucleotides at femtomole-level. We recently improved the sensitivity of RIS so that as low as one Angstrom surface thickness change can be detected. In addition, using peptide nucleic acids (PNAs) as the sensing probe, we now can easily detect the complementary DNA targets at the amount of 10-fold less via signal amplification by gold nanoparticles.
9:00 PM - R3.3
Water-Soluble Dendritic Photosensitizers Capable of Multi-Photon Absorption and The Affects of Core Modification on Singlet Oxygen Generation.
Michael Oar 1 , William Dichtel 1 , Jason Serin 1 , Jean Frechet 1 , Tymish Ohulchanskyy 2 , Paras Prasad 2 , Joy Rogers 3 , Loon-Seng Tan 3
1 Department of Chemistry, University of California, Berkeley, California, United States, 2 Institute for Lasers, Photonics and Biophotonics, and Department of Chemistry, State University of New York, Buffalo, New York, United States, 3 Polymer Branch, Air Force Research Laboratory/MLBP, Wright-Patterson AFB, Ohio, United States
Show Abstract9:00 PM - R3.30
Modulation of Electronic Properties of Single Wall Carbon Nanotubes by the Presence of an Ionic Shell.
Vladimir Dobrokhotov 1 , Chris Berven 1
1 Physics, University of Idaho, Moscow, Idaho, United States
Show AbstractWe report the change to the band structure of two types of carbon nanotubes due to the presence of an isolated, non-conducting, uniformly charged shell held at a fixed distance above their surfaces. We find that, depending on the chirality of the nanotube, the strain on the lattice causes the dispersion relationships to change. This change can result in a modification of the band structure which can induce a metal-semiconductor transition. We consider these effects as a possible mechanism for heavy-metal ion sensing by functionalized carbon-nanotubes.
9:00 PM - R3.31
Materials used in Chemiblock Vapor Sensors
Douglas Schulz 1 , Aaron Halvorsen 1 , Conrad Thomas 1 , John Jacobson 1 , Jeremy Lee 1 , Aaron Reinholz 1 , Douglas Chrisey 1
1 Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota, United States
Show AbstractThe first chemical gas transducers that employ NanoblockTM substrates are described. Sensor fabrication is realized by controlled deposition of a novel C black/polymer composite onto Si wafers with subsequent processing steps yielding transducers with a small form factor (<1x1 mm2). These so termed “Chemiblocks” are inexpensive (<$0.10 each), exhibit fast response times (i.e., t90 < 10 sec), rapid recovery times (t10 < 60 sec) and a lower detection limit of <50ppm when exposed to a nerve gas stimulant, dimethylmethylphosphonate. Application to array-based detection is anticipated to be straightforward given the maturity of conventional C-black/polymer composite sensor technology whereby differentiation between target analytes and interferents is well established. The novel chemoselective polymer composition of the transducer layer has been tailored for the detection of Improvised Explosive Devices (IEDs) and preliminary results will also be presented.
9:00 PM - R3.32
Fast and Quantitative Detection of Pathogens at Ultralow Concentration.
Jinhao Gao 1 , Lihua Li 1 , Kin-Hung Chow 2 , Ling Wang 1 , Pak-Leung Ho 2 , Bing Xu 1 3
1 Department of Chemistry, The Hong Kong Univ. Sci. & Technol., Kowloon Hong Kong, 2 Center of Infection and Department of Microbiology, The University of Hong Kong, Hong Kong Hong Kong, 3 Bioengineering Program, The Hong Kong Univ. Sci. & Technol., Kowloon Hong Kong
Show AbstractWe have reported the application of biofunctional magnetic nanoparticles (FePt-Van) for pathogen capture at ultralow concentration. Here we describe a simple protocol based on vancomycin and FITC conjugates (FITC-Van) for detecting bacteria by fluorescence. We combine two schemes: one is that FePt-Van conjugates capture bacteria at ultralow concentration by specific multiple ligand-receptor interactions; the other is the high sensitivity of the fluorescence spectra. In this procedure, we use excess amount of D-Ala-D-Ala to completely release FITC-Van from bacterial surfaces. Using the calibration curve generated from a series of known bacterial concentrations, we can quantitatively detect bacteria at the concentration as low as 10 CFU/mL within 2 hours. We expect that this simple system will find other applications in biologic researches and clinical diagnoses.
9:00 PM - R3.33
Anion Sensors in Polyurethane Matrices: Synergy Between Matrix and Sensor Materials Improves Selectivity of the Sensing Process.
Manuel Palacios 1 , Radek Pohl 1 , Grigory Zyryanov 1 , Pavel Anzenbacher 1
1 Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio, United States
Show AbstractThe significant role anions play in both the biological systems and industrial processes demands the development of highly sensitive and selective anion sensors capable of operating in various media, particularly in water. Numerous anion receptors and sensors utilizing hydrogen bonding have been synthesized. Hydrogen bonds, unlike electrostatic interactions, are directional and may be used to induce selectivity in an anion-sensor interaction. Unfortunately, hydrogen bonds are relatively weak, which makes reliable sensing in strongly competitive media such as water difficult in most of the real-life applications. The anion receptors and sensors utilizing stronger but non-directional electrostatic interactions are, however, plagued by low selectivity as all anions present in the medium are indiscriminately attracted to such receptors. Here we present materials utilizing synergy between a polymer matrix and simple sensor moieties. These materials consist of blends of hydrogen-bond-based colorimetric anion sensors (2,3-di(pyrrole-2-yl)quinoxaline, DPQ) with extended conjugated chromophores embedded in hydrophilic polyurethane matrices. Anion sensors embedded in the hydrophilic polyurethane matrix have the advantage of water being stripped off hydrated anions thus reducing or removing the competing hydrogen bonding from water. The resulting semi-wet sensors may use both the change in color and in fluorescence as a signal output. Specifically, multi-well micro-assays for small anions utilize a new family of polyurethane-embedded fluorescent sensors. These assays use 0.2 μL of aqueous analytes in each well and respond with a response time of <10s.In summary, the use of synergy between hydrophilic matrices and anion sensors for sensing of aqueous analytes allows for using simpler and less expensive receptors and opens up new possibilities for the development of high performance anion sensors with good selectivity and response profiles at a fraction of cost of most anion sensors.
9:00 PM - R3.5
Newly Developed Fe-Fe2O3/PolyoxocarbosilaneCore-Shell Nanocomposite Prepared by Laser Pyrolysis: Characterization and Sensing Properties.
Ion Morjan 1 , Josef Pola 2 , Rodica Alexandrescu 1 , Florian Dumitrache 1 , Adelina Tomescu 3 , Ruxandra Birjega 1 , Ion Voicu 1 , Lavinia Albu 1 , Anna Galikova 2 , Victor Ciupina 4 , Zdenek Bastl 5
1 Laboratory of Laser Photochemistry , National Institute for Lasers, Plasma and Radiation Physics, 76900 Bucharest Romania, 2 , Institute for chemical Process Fundamentals of the Czech Academy of Science, 165 02 Prague 6 Czech Republic, 3 , National Institute of Materials Physics, 077125 Bucharest Romania, 4 , Ovidius University, Constanta, P.O.B. 8600 Romania, 5 , J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech, 182 23 Prague 8 Czech Republic
Show AbstractNanocomposite metal/polymer systems, combining inorganic materials together with polymers in nanoparticle form are presently promising for a new generation of high temperature gas sensors. Sensing performances are dependent upon the nanoscale morphology. We report here about the preparation of nanosized iron-based particles that are covered with organosilicon polymer. The IR laser pyrolysis of the ethylene-sensitized iron pentacarbonyl and hexamethyldisiloxane gas mixtures was used as synthesis technique. The core-shell nanostructures become superficially oxidized to gamma-Fe2O3 in the outer core phase, through incomplete protection against the atmosphere by the porous structure of the surrounding polymer. For the measurements of phase-separated structures within the composites, the particles were characterized by different analytical techniques (spectral analyses, electron microscopy and thermal gravimetry). The sizes, shapes, chemical composition, internal structure and morphology of the nanoparticles depend on flow rates of precursors and total pressure of the procedure. Transmission electron microscopy images are compatible with crosslinked nanochains which appear together with ca 20-100 nm sized balls. The balls consist of dark cores and a lighter shell phase that can be respectively attributed to elemental iron and a blend of iron oxide and polyoxocarbosilane. The Fe-rich nanocomposite (which is poor in polyoxocarbosilane) has rather uniform size of nanochains, whereas the Fe-poor nanocomposite contains both nanochains and nanoballs of various sizes. The organosilicon polymer shell in the former contains less C-H bonds. Thermal behavior of composites is characterized by two-stage evolvement of methane. The sensing properties of the nanocomposites, were tested by depositing thick films on alumina substrates and heating them at 450 C. The variation of their electrical resistance in presence of CO and CH4 (in dry and humid air) was measured. Preliminary results address the selectivity of the new nanostructures relatively to the tested toxic gases.
9:00 PM - R3.6
Silicon Microchannel Array as a Basis of Biosensor Device.
Natalia Vandysheva 1 , Alexander Bublikov 1 , Sergei Romanov 1 , Dmitrii Pyshnyi 2 , Alexander Lomzov 2
1 , Institute of Semiconductor Physics Siberian Branch of Russian Academy of Sciences, Novosibirsk Russian Federation, 2 , Institute of Chemical Biology and Fundamental Medicine Siberian Branch of Russian Academy of Sciences, Novosibirsk Russian Federation
Show Abstract9:00 PM - R3.7
Nanostructures for Biosensors: Patterning of Surface-Enhanced Raman Spectroscopy-active Substrates.
Ivano Alessandri 1
1 , University of Brescia, Brescia Italy
Show Abstract9:00 PM - R3.8
Sysnthesis of Chitosan Hydrogel Containing Ionic liquid: Swelling and Penetrating of Ionic Liquid
C. K. Lee 1 , S. J. Park 1 , S. G. Yoon 1 , S. R. Shin 1 , K. M. Shin 1 , M. K. Shin 1 , B. K. Gu 1 , M. S. Kim 1 , S. J. Kim 1
1 Dept. of Biomedical Engineering, Hanyang University, Seoul Korea (the Republic of)
Show AbstractThe swelling behavior of chitosan hydrogel in ionic liquid–water binary systems was studied using hydrophilic room-temperature ionic liquids (1-buthyl-3-methyimidazolium tetrafluorobrate, as donated BMI-BF4), to elucidate the swelling mechanism of chitosan hydrogels. The swelling of hydrogels is an important characteristic in their applications. Hydrogels show a large degree of swelling in aqueous environments, and a differential shirnk-swell response to different solvents, including organics and salt solutions. The most attractive field for hydrogels is in artificial muscles and actuators, because they provide a mechanical response to an electrical stimulation. Some hydrogels have been developed as polymer gel electrolytes for use in soft actuators, because hydrogels can be electrolytes themselves, and can also house an electrolyte by dissolving the electrolyte in the hydrogel network. However, hydrogel have a serious lack of electrical stability with regards to electrolytes in ambient conditions, caused by the high volatility of water. This means that there is limit to the application lifetime of hydrogels in polymeric conducting systems. Room-temperature ionic liquids (RTILs) are intersting liquid electrolytes for electrochemical applications. Major reasons for the interest in RTILs are their nonvolatility, high conductivity, and large electrochemical windows. Their nonvolatility diminishes the any risk to the electrical stability caused by loss of the solvent to the atmosphere. One aspect of RTILs is their ability to control water miscibility by simply changing the anion. Their utility in the field of polymer hydrogel electrolytes is not necessarily new. Thus, an understanding of the swelling behavior of hydrogel with a RTIL–water binary system is important for their application. In this study, we report on the preparation of a chitosan hydrogel containing an RTIL and on the elucidation of swelling mechanism of a chitosan hydrogel in an ionic liquid–water binary system. It was confirmed that chitosan hydrogels are much stiffer after immersing in a pure RTILs because the water existing inside the chitosan polymer network is extracted into the RTIL. The pH of the binary system changed when the RTIL was in contact with water. The chitosan hydrogels were fully dissociated at a 90% water content of the BMI-BF4–water binary system. The equilibrium binary system content behavior of the chitosan hydrogels depended upon the amount of free water, which is a measure of the number of water molecules that do not interact with the ionic liquid. Chitosan hydrogels containing the RTIL were prepared by dropping pure RTIL onto a fully water-swollen hydrogel.
9:00 PM - R3.9
Chemically Functionalized Nanopores for Bio-organism Detection.
Joakim Nilsson 1 , Sonia Letant 1
1 Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract
Symposium Organizers
Elisabetta Comini Universita' di Brescia
Pelagia Irene Gouma State University of New York-Stony Brook
Vincenzo Guidi University of Ferrara
David Kubinski Ford Motor Company
R4: Nanowires
Session Chairs
Nicolae Barsan
Elisabetta Comini
Wednesday AM, April 19, 2006
Room 3022 (Moscone West)
9:15 AM - **R4.1
Controlled Growth and Applications of Aligned Oxide Nanowires.
Zhong Wang 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractNanowire and nanotube based materials have been demonstrated as building blocks for nanocircuits, nanosystems and nano-optoelectronics. Controlled growth of aligned oxide nanowires is important for many technological applications. This presentation will focus on our recent progress in growing aligned oxide nanostructures and the characterization of their properties for applications in sensors, electron field emission, light emitting, spintronics and mechanics [1-10].[1]J. H. He, J. H. Hsu, C. W. Wang, H. N. Lin, L. J. Chen, Z. L. Wang “Pattern and Feature Designed Growth of ZnO Nanowire Arrays for Vertical Devices”, J. Phys. Chem. B, in press (2005).[2]J. Zhou, R.S. Yang, S.Z. Deng, L. Gong, J. Chen, J.C. She, Z.L. Wang, N.S. Xu “Growth and Field Emission Property of Tungsten Oxide Nanotip Arrays”, Appl. Phys. Letts., in press (2005).[3]J.H. He, C.S. Lao, L. J. Chen, D. Davidovic, and Z.L. Wang “Large-scale Ni-doped ZnO Nanowire Arrays and Electrical and Optical Properties”, J. Am. Chem. Soc., in press (2005).[4]X.D. Wang, C.S. Lao, E. Graugnard, C.J. Summers and Z.L. Wang “Large-size liftable inverted-nanobowl sheets as reusable masks for nanolithiography”, Nano Letters, 5 (2005) 1784-1788.[5]J. Zhou, Y. Ding, S.Z.i Deng, L. Gong, N.S. Xu and Z.L. Wang “Three-dimensional tungsten oxide nanowire networks”, Advanced Materials, 17 (2005) 2107-2110.[6]X.D. Wang , J.H. Song , P. Li , J. H. Ryou , R.D. Dupuis , C.J. Summers and Z.L. Wang ”Growth of Uniformly Aligned ZnO Nanowire Heterojunction Arrays on GaN, AlN, and Al0.5Ga 0.5N Substrates”, J. Am. Chem. Soc., 127 (2005) 7920-7923.[7]C. Yu, Q. Hao, S. Saha, and L. Shi, X.Y. Kong and Z.L. Wang " Integration of Metal Oxide Nanobelts with Microsystems for Nerve Agent Detection ", Appl. Phys. Letters, 86 (2005) 063101 + cover.[8]J.H. Song, X.D. Wang, E. Riedo and Z.L. Wang “Elastic Property of Vertically Aligned Nanowires”, Nano Letters, 5 (2005) 1954 - 1958.[9]A.L. Pan, H. Yang, R.B. Liu, R.C. Yu, Z.L. Wang and B.S. Zou “Color-tuned Photoluminescence of Alloyed CdSxSe1-x Nanobelts”, J. Am. Chem. Soc., in press (2005).[10] Thanks the support from NSF, DARPA, NASA and Airforce.[11] for details: http://www.nanoscience.gatech.edu/zlwang/
9:45 AM - R4.2
HRTEM of MoO3 Nanowires Prepared via Electrospinning
Krithika Iyer 1 , Aisha Bishop 1 , Pelagia Gouma 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States
Show Abstract1-D nanostructures have been traditionally produced successfully using a variety of vapor- solid growth processes. In a novel approach, electrospinning can be employed as a one-step fabrication technique for producing metal oxide nano- architectures for applications ranging from opto-electronic components to sensors. Molybdenum Trioxide sol-gel was prepared and electrospun using poly-vinyl-pyrrolidone as the carrier polymer. The electrospun matrix was calcined at 500°C exposing pure metal oxide nanowires. Characterization of these nanoassemblies using High Resolution Transmission Electron Microscopy (HRTEM) reveals that the nanowires are single crystals with diameters <10nm and lengths of the order of several μm. Details of the phase, crystallinity, and oxidation states of these 1-D nanostructures will be discussed.
10:00 AM - R4.3
Synthesis, Characterisation of WO3 Nanowires and Their Application in Chemical Gas Sensing.
Sandro Santucci 1 , Silvia Piperno 1 , Maurizio Passacantando 1 , Luca Lozzi 1 , Carlo Cantalini 2 , Phani Ayalasomajayula 1
1 Physics, University of L'Aquila and CNR-CASTI, L'Aquila Italy, 2 Chemistry, University of L'Aquila, L'Aquila Italy
Show AbstractWO3 nanowires have been synthesised by using a wet chemical solution with electrospinning technique. For the formation of pure WO3 nanowires, polymethylmethcrylate (PMMA) solution and tungsten hexa-chloride (WCl6) solution have been used as a base for the nanowire growth formation and WO3 source, respectively. The effect of variation of processing parameters, diameter of the nanowires, composition have been optimised by employing high resolution scanning electron microscopy, and transmission electron microscopy techniques. Nanowires synthesised at room temperature have exhibited WO2-x / PMMA mixture. On the other hand, complete pyrolsis of the PMMA has resulted for those annealed at 300°C for 3h in air in the formation of pure WO3 nanowires as evident from high spatial resolution photoelectron spectroscopy measurements showing the presence of WO3 only on the nanowires. X-ray diffraction measurements indicate the formation of mixed WO3 crystalline phases whit a predominance of the triclinic and orthorombic ones. A case study has been presented, where pure WO3 nanowires were used as NO2, CO, NH3 gas sensing elements and compared to previously investigated WO3 thin films. Preliminary results showed enhanced gas sensitivity, faster response and lower gas detection limit than that of the continuous thin films of WO3. Plausible mechanism for the enhanced sensitivity has also been discussed.
10:15 AM - **R4.4
Structure, Composition and Detection at Low Levels Using Individual and Multiple Nanostructures for Integrated Gas Sensor Microsystems.
Juan Morante 1
1 Electronics, University of Barcelona, Barcelona Spain
Show Abstract11:15 AM - **R4.5
Gas Sensing by quasi-1D Metal Oxides: Towards Understanding of the Surface Processes.
Andrei kolmakov 1
1 Physics, SIUC, Carbondale, Illinois, United States
Show AbstractWhen the diameter of the semiconductor quasi-1D nanostructure becomes comparable or lower than the material’s Debye length the tiny changes in the chemical state of the surface due to the presence of chemical or biological agents result in the depletion (or accumulation) of electrons through the entire volume of the nanostructure. Being combined with the large surface to volume ratio, this effective transduction of the surface events to the conductance change provides the basis for superior chemical sensing function by the oxide nanowire device. We have developed and tested few experimental approaches to tune sensitivity and selectivity of these sensors as well as implemented new methods to monitor the surface processes on individual nanostructures. In particular, the influence of surface sensitization with catalyst particles, radiation defects along with the effect of the gate potential (when configured as FET) on the surface reactivity and selectivity were directly demonstrated. We have tested a range of spectroscopy and imaging techniques to address local transport particularities taking place in the individual operating metal oxide nanostructure sensor. In particular, we were using Scanning Surface Potential Microscopy (SSPM) to investigate dc potential distributions in an operating device. We also have successfully implemented of synchrotron radiation based photoelectron emission spectro-microscopy (PEEM) to explore submicron compositional and electronic (work function) inhomogeneouties in individual metal oxide nanowire wired as a chemiresistor.Finally we are developing the new growth techniques for growth 1D nanostructures with tunable morphologies particularly prospective for chemical sensing. We believe that these results open new avenue to control and visualize both in real time and at nanoscale the surface phenomena taking place in 1-D nanostructure sensors.
11:45 AM - R4.6
On the Role of Oxygen Vacancies in the Determination of the Gas-sensing Properties of Tin-Oxide Nanowires.
Andrea Zappettini 1 , Mingzheng Zha 1 , Lucio Zanotti 1 , Davide Calestani 1 , Giancarlo Salviati 1 , Laura Lazzarini 1 , Roberto Mosca 1 , Elisabetta Comini 2 , Giorgio Sberveglieri 2
1 , IMEM-CNR, Parma Italy, 2 SENSOR Laboratory, INFM-Brescia University, Brescia Italy
Show Abstract12:00 PM - R4.7
Gas Sensing with Gold Nanoparticle-Decorated GaN Nanowire Mats.
Vladimir Dobrokhotov 1 , Chris Berven 1 , David McIlroy 1 , M. Norton 2 , Alaaedeen Abuzir 1 , Wei-Jiang Yeh 1 , Joeseph Bochenek 1 , Mark Cartwright 1 , Lidong Wang 1 , Jeremy Dawson 1 , Miles Beaux 1
1 Physics, University of Idaho, Moscow, Idaho, United States, 2 School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington, United States
Show AbstractThe electrical properties of chemical sensors constructed from mats of bare GaN nanowires and GaN nanowires decorated with gold nanoparticles are presented. The sensors were tested in vacuum and at atmospheric pressures of Ar, N2 and methane. The current-voltage (I-V) curves of the sensor constructed with bare GaN nanowires were Ohmic and the device was insensitive to all gases tested. The I-V curves of the sensor constructed from GaN decorated with Au nanoparticles were non-linear and exhibited a drop in conductivity of five orders of magnitude relative to bare GaN nanowire sensors. The Au nanoparticle decorated nanowires also exhibited electrical responses that were chemically selective. The sensor exhibited a nominal response to Ar and a slightly greater response to N2 relative to vacuum. A suppression of the conductivity of the Au-GaN device of 50% was observed upon exposure to methane. Both the drop in conductivity of the Au-GaN nanowire-based sensor, relative to bare GaN nanowires, and the response to methane are explained in terms of the formation of a depletion layer and an increase in the depletion layer width due to physisorption induced surface potentials.
12:15 PM - R4.8
Characterization of Dielectrophoretically Assembled Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) Nanowires.
Y. Dan 1 , Y. Cao 2 , T. E. Mallouk 2 , A. T. Johnson 3 , S. Evoy 4
1 Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Department of Chemistry, Penn State University, University Park, Pennsylvania, United States, 3 Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 4 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractThe development of a low-footprint integrated sensing array technology would open vast markets spanning a wide variety of applications. Clinical diagnostic applications alone represent a significant market that is already driving significant efforts. Indeed, the acetone concentration in the breath of a healthy person is around 5 ppm, but it is 300 ppm for person with metabolic disease like diabetes mellitus. Mercaptans and aliphatic acids were found in the breath of patients with liver cirrhosis while dimethyl- and trimethylamine were found in the breath of uremic patients. It has been established that one-dimensional "nanowire" sensing elements possess significant increased sensitivity over thin films due to the one-dimensional confinement of carriers in such structures. In addition, nanowire-based sensors enable the large-scale integration of high-density arrays directly onto fully processed silicon CMOS chips through dielectrophoretic integration methods [1,2].Conducting polymers are specifically ideal for such applications as they selectively respond to organic chemicals with high sensitivity under ambient conditions. Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) received sustained interest in recent years as one of the most stable conducting polymers. We here report sensing response of PEDOT/PSS nanowires (~10 um in length and ~250nm in diameter) grown using a porous templating method.[3] Such wires are integrated onto silicon surfaces using dielectrophoretic assembly through two assembly electrodes dielectrically coupled to two buried feed-in leads [1,2]. In order to minimize contact resistance to the assembly electrodes, we synthesized “striped” nanowires with a structure of gold-PEDOT/PSS-gold. From the characterization of wires of various dimensions, we determine that polymer material possess a nominal conductivity ~5 mho-cm. For instance, a L = 10 um long, D = 250 nm diameter wire possesses a nominal resistance of ~ 100 kohm and a contact resistance to the gold of ~30 kohm. These sensing wires showed a linear fractional change of resistance, with maximal change is –15%, -11%, +13% and +9% at the saturation vapor pressures of DMMP, DNT, Methanol and Acetone, respectively. The nanowire responds rapidly to all of the analytes with response and recovery time on the scale of seconds. Moreover, the sensors show a constant response over at least 20 cycles of exposure to analyte followed by air. We will present a complete physicochemical characterization of the sensing response of these sensing wires, and include preliminary results on their heterogeneous integration into large scale sensing arrays.[1] P. A. Smith, C.D. Nordquist CD, T.N. Jackson, T.S. Mayer, B.R. Martin, J. Mbindyo, and T.E. Mallouk. Appl. Phys. Lett, 77, 1399 (2000).[2] A. Narayanan, Y. Dan, et al. IEEE Trans. Nano., in press.[3] R. Hernandez, L. Richter, S. Semancik, S. Stranick, and T. E. Mallouk, Chem. Mater.,16, 3431-3438 (2004).
12:30 PM - R4.9
Embedded Piezoresistime Microcantilever Sensors: Materials for Sensing Hydrogen Cyanide Gas.
Timothy Porter 1 , Randy Dillingham 1 , Ray Stewart 3 , Tim Vail 2
1 Physics , Northern Arizona University, Flagstaff, Arizona, United States, 3 , Bay Materials, LLC, Menlo Park, California, United States, 2 Chemistry, Northern Arizona University, Flagstaff, Arizona, United States
Show AbstractThe embedded piezoresistive microcantilever (EPM) sensor represents a basic, MEMS-based platform for the sensing of a variety of analytes in a number of different applications. In the EPM design, a tiny (200 micron) piezoresistive microcantilever is partially embedded into a “sensing material”, forming a small, highly rigid and robust sensing unit that is portable, resistant to movement and shock, and requires only very simple and inexpensive support electronics to operate. The sensing material is designed to respond physically or chemically to the desired analyte molecules, resulting in a tiny strain in the cantilever. This strain results in a measurable change in the cantilever resistance, which is recorded by the electronics. Sensing materials we have used include hydrogels, functionalized hydrogels, antibody functionalized gels, and ss-DNA functionalized gels. Previous applications include sensors for medical testing, detection of toxic gases, detection of environmental toxins, and bio-agent detection. Sensor platforms may include handheld probes, laptop probes, and wireless mote sensors connected in a mesh network. In the present study, we will discuss different formulations for materials designed to detect hydrogen cyanide gas in an EPM sensor. These materials form the basis for a tiny, inexpensive, solid-state hydrogen cyanide detector that may be deployed in a mesh network of up to hundreds of sensors.
12:45 PM - R4.10
Controlled Growth of In2O3 Nanowires on Seeded Catalytic Substrates.
Alberto Vomiero 1 , Sebastiano Bianchi 1 , Elisabetta Comini 1 , Guido Faglia 1 , Matteo Ferroni 1 , Giorgio Sberveglieri 1
1 SENSOR Lab CNR-INFM, Brescia University, Brescia Italy
Show AbstractR5: Polymer Based Detectors
Session Chairs
Vincenzo Guidi
Xiao-Dong Zhang
Wednesday PM, April 19, 2006
Room 3022 (Moscone West)
3:00 PM - **R5.1
Colorimetric Sensor Arrays for the Detection of Toxic Industrial Chemicals.
Ken Suslick 1 , Michael Janzen 1 , Jennifer Ponder 1 , Chen Zhang 1 , Crystal Ingison 1
1 Chemistry, University of Illinois, Urbana, Illinois, United States
Show Abstract We have developed an entirely new class of lightweight chemical identification systems based on colorimetric sensor arrays: essentially a digital, multidimensional extension of litmus paper. For the detection of volatile organic compounds (VOC), we have demonstrated high sensitivity (below PEL levels) for the detection of toxic industrial chemicals (TICs). In addition, highly selective discrimination of pure analytes and of complex mixtures has been demonstrated. Array based vapor sensing has emerged as a powerful approach toward the detection of chemically diverse analytes. We have developed and patented a unique chemical detection technology in which colorimetric changes in an array of dyes constitute a signal much like that generated by the mammalian olfaction system; each dye is a cross-responsive sensor. This technology uses a disposable array of chemoresponsive dyes printed on an inert membrane as the primary sensor elements. Striking visual identifications of a wide range of VOCs are easily made at ppb levels, for example to hydrogen sulfide, methylsulfide, formic acid, acetic acid, ammonia, and hexylamine (i.e., sensitivities comparable to GC-MS detection). The design of the colorimetric sensor array is based on two fundamental requirements: (1) the chemo-responsive dye must contain a center to interact strongly with analytes, and (2) this interaction center must be strongly coupled to an intense chromophore. The first requirement implies that the interaction must not be simple physical adsorption, but rather must involve other, stronger chemical interactions. Chemoresponsive dyes are those dyes that change color, in either reflected or absorbed light, upon changes in their chemical environment. The consequent dye classes from these requirements are (1) Lewis acid/base dyes (i.e., metal ion containing dyes), (2) Bronsted acidic or basic dyes (i.e., pH indicators), and (3) dyes with large permanent dipoles (i.e., zwitterionic solvatochromic dyes).[1] Suslick, K. S. “An Optoelectronic Nose: Colorimetric Sensor Arrays” MRS Bulletin, 2004, 29, 720-725. [2] Rakow, N. A.; Sen, A., Janzen, M.C.; Ponder, J. B.; Suslick, K. S. “Molecular Recognition and Discrimination of Amines with a Colorimetric Array” Angew. Chem. Int. Ed. 2005, 44, 4528-4532.[3] Zhang, C.; Suslick, K. S. “A Colorimetric Sensor Array for Organics in Water”, J. Am. Chem. Soc. 2005, 127, 11548-11549.
3:30 PM - R5.2
Metalloporphyrins Based Chemical Sensors
Corrado Di Natale 2 3 , Roberto Paolesse 1 3 , Eugenio Martinelli 2 , Arnaldo D'Amico 2 3
2 Electronic Engeenering, University of Rome tor Vergata, Roma Italy, 3 Istituto Microelettronica e Microsistemi, CNR, Roma Italy, 1 Chemical Science and Technologies, University of Rome Tor Vergata, Rome Italy
Show Abstract3:45 PM - R5.3
Polyaniline Nanofiber Chemical Sensors for Homeland Security and Other Applications
Bruce Weiller 1 , Richard Kaner 2 , Shabnam Virji 1
1 Materials Processing and Evaluation Department, The Aerospace Corporation, Los Angeles, California, United States, 2 Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractPolyaniline is a conducting polymer with electrical properties that can change greatly upon exposure to various chemicals. Most notably, when polyaniline is exposed to strong acids and bases, the conductivity changes by greater than 8 orders of magnitude do to a well know doping and dedoping reactions. Recently, we have developed simple, chemical, template-free synthetic methods for polyaniline nanofibers. The polymerization methods are selective for nanofibers, can be readily scaled to make large quantities and can be controlled to selectively produce nanofibers with narrow distributions. Chemiresistor sensors are fabricated from polyaniline nanofibers by casting nanofiber films on microelectrode arrays. The nanofiber-based sensors have significantly better performance than conventional material in both sensitivity and time response for all analytes tested including acids, bases, hydrazine, and organic vapors. The high surface area, small diameter, and porous nature of the nanofiber films appear to allow facile diffusion of vapors into the films. Recently we have shown that new composite materials formed from nanofibers and various inorganic and organic materials can be used to detect analytes that do not give a significant response with unmodified polyaniline. For example hydrogen sulfide can be detected using polyaniline nanofibers modified with metal salts and organic additives can be used to detect phosgene. Finally we show that unmodified, doped polyanline nanofibers can be used to detect hydrogen gas. Therefore polyaniline nanofibers appear to be versatile chemical sensor materials that have excellent potential for many chemical detection applications including homeland security.
4:30 PM - R5.4
Towards Label-free Detection of Charged Macromolecules Using Field-effect-based Structures: Scaling Down from Capacitive EIS Sensor over ISFET to Nano-scale Devices.
Michael Schoening 1 , Maryam Abouzar 1 , Sven Ingebrandt 2 , Johannes Platen 1 , Andreas Offenhaeusser 2 , Arshak Poghossian 1
1 Applied Sciences and Technology , Aachen University of Applied Sciences & Research Centre Juelich, Juelich Germany, 2 ISG-2, Research Centre Juelich, Juelich Germany
Show Abstract4:45 PM - R5.5
Biosensors and Cell Culturing Substrates Based on Electrical Conducting Polymers.
Bohyun Kim 1 , Yong Doo Park 1 , Dae Hyun Kim 1 , Dong Hyuk Park 2 , Jinsoo Joo 2 , Hyoung J. Choi 3 , Kyu Baek Lee 1
1 College of Medicine, Korea University, Seoul Korea (the Republic of), 2 Physics, Korea University, Seoul Korea (the Republic of), 3 Polymer science and Engineering, Inha University, Inchon Korea (the Republic of)
Show Abstract5:00 PM - R5.6
Mesoporous Bioactive Glass Microparticles with Superior In Vitro Hemostatic and Bone-forming Activities.
Qihui Shi 1 , Todd Ostomel 1 , Chia-Kuang Tsung 1 , Galen Stucky 1
1 Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California, United States
Show AbstractWe have developed a surfactant-templated mesoporous bioactive glass (MBG) microparticles by an aerosol-assisted self-assembly process. The spherical MBG microparticles, with polydisperse particle sizes ranging from 0.2-2 μm, posses large specific internal surface area (~300 m2/g) and pore volume (~0.4 cm3/g) as well as large external surface area. These unique textural properties facilitate cation release and fluid adsorption to concentrate components in the fluid, which promote surface dependent blood clotting reactions and accelerate the kinetic deposition process of biological equivalent hydroapatite with an enhancement of bone-forming bioactivity. This material is promising for applications as a rapid acting hemostatic agent and template for the growth of artificial bone. Uncontrolled blood loss is the major cause of death in civilian and military trauma. The successful treatment of traumatic injuries requires the intervention of rapid-acting and biocompatible hemostatic agents. In vitro blood clotting investigation shows that MBG microparticles are able to rapidly induce a blood clot when exposed to blood through contact activation and release of coagulation co-factors. MBG microparticels have a faster clotting time and result in a stronger clot with less heat delivery than QuikClot, the leading inorganic hemostatic agent currently available. Bioactive glasses have been widely studied and used in clinical applications for bone and dental repair. MBG microparticles are able to greatly improve the biocompatibility and in vitro bone-forming bioactivity by mixing with the ammonium phosphate buffer to form a MBG cement. Upon mixing, a paste forms which can be molded to fill spaces generated in bones by physical injury. The paste sets within ~10 min with a rapid precipitation of rod-like calcium-deficient hydroxyapatite (d-HA) nanocrystals. It is known d-HA has high biocompatibility and bone-forming bioactivity in the process of bone forming. MBG cements, containing amorphous silica and d-HA phase, are therefore elicit an immediate precipitation of biologically equivalent apatite on its surface when immersed in stimulated body fluid, whereas other bone-repairing bioceramics like calcium phosphate cements, bioactive glasses and non-porous bioactive glass cements require long introduction period to induce the formation of apatite layer.
5:15 PM - R5.7
Inorganic Based Hemostatic Agents for Modulating the Blood Clotting Network.
Todd Ostomel 1 , Peter Stoimenov 1 , Qihui Shi 1 , Nathaniel Schaefle 1 , Patricia Holden 2 , Song-I Han 1 , Hasan Alam 3 , Galen Stucky 1
1 Chemistry and Biochemistry, UC Santa Barbara, Santa Barbara, California, United States, 2 Donald Bren School of Environmental Science and Management, UC Santa Barbara, Santa Barbara, California, United States, 3 Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States
Show Abstract Uncontrollable hemorrhage is the leading cause of battlefield deaths, accounting for over fifty percent of fatalities. Traumatic injuries of any nature present unique challenges to first aid responders with regard to initiating and maintaining hemostasis, particularly when traditional tourniquets and gauze dressings are insufficient for controlling massive bleeding. There is therefore a great need, for civilians and soldiers alike, for effective rapid acting hemostatic agents that can be directly applied to wounds by individuals with minimal medical training. Because a majority of these injuries involve intracavity bleeding, hemostatic agents that are conformable to the wound site and rapid acting are desirable. Moreover, when the body’s skin barrier is breached, opportunistic pathogens will colonize the inflicted site and further complicate recovery. The results of this work have culminated in both an improvement to the leading hemostatic agent currently utilized by the United States Armed Forces as well as an establishment of a new paradigm for designing rapid acting inorganic based hemostatic agents. Materials have been designed that can modulate the blood coagulation network through a manipulation of surface properties, electrolyte control, thermal application, and predictable adsorption capacity. The hemostatic agents prepared were characterized with regard to their thermal and material properties. Rheological studies of induced blood clot formation were used to identify the most important in vitro clotting parameters that predict in vivo hemostatic performance in a swine model of a life threatening battlefield injury. Antibactericidal activity of the prepared hemostatic agents against opportunistic pathogens was investigated. In addition, NMR spectroscopy has been applied to identify plasma metabolites chemically involved during induced blood clot formation by inorganic agents.
5:30 PM - R5.8
Aromatic Vapor Detection using Microcantilevers Functionalized with Self-Assembled Monolayers.
Andrew Riley 1 , Alan Schilowitz 1 , Mark Disko 1
1 Corporate Strategic Research, Exxon Mobil, Annandale, New Jersey, United States
Show AbstractSurface stress induced deflection of microcantilevers coated with self-assembled monolayers (SAMs) is used to sense for the presence of aromatic analytes including toluene and xylene. Monolayers are formed on gold coated cantilevers, using alkanethiols, mercaptanols, and aromatic thiols. These coatings create a variety of chemical functionalities at the cantilever surface, which impact the interactions between target molecules and the cantilever. The different organic functionalities in the self-assembled monolayers lead to varying degrees of sensitivity to the analytes. The differential responses of the cantilevers are investigated as a means to selectively detect aromatic vapors at trace levels.
5:45 PM - R5.9
An Electronic Tongue for Orange Juice Classification
Eliton Medeiros 1 3 , Rodrigo Martinez 1 3 , Rinaldo Gregorio Filho 3 , Luiz Mattoso 1 2 3
1 Embrapa Instrumentacao Agropecuaria, Embrapa, Sao Carlos, SP, Brazil, 3 Dept. Eng. Materiais, Univ. Federal de Sao Carlos, Sao Carlos, SP, Brazil, 2 ARS/BCE-LABEX, USDA/ARS/BCE-EMBRAPA, ALBANY, California, United States
Show AbstractR6: Poster Session: Inorganic Materials for Sensing
Session Chairs
Pelagia Gouma
Vincenzo Guidi
Thursday AM, April 20, 2006
Salons 8-15 (Marriott)
9:00 PM - R6.1
CO2 and O2 Sensing Properties of Nanostructured Sm1-xMxCoO3 (M = Ba, Sr, Ca; x = 0, 0.1) Prepared by Wet-chemical Synthesis.
Carlos Michel 1 , Emilio Delgado 1
1 Department of Physics, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico
Show Abstract9:00 PM - R6.10
Switchable Nanostructured Surfaces for High-Throughput Biochemical Analyses.
Joanna Aizenberg 1 , Tom Krupenkin 1 , Paul Kolodner 1 , Marc Hodes 1 , Ashley Taylor 1
1 , Lucent Technologies/Bell Laboratories, Murray Hill, New Jersey, United States
Show AbstractNew advances in the rapid detection and neutralization of biological agents are becoming crucial elements for biotechnology, medicine, defense, and national-security. There is enormous need for improved techniques of chemical reactions in small volumes, bacterial cell and spore lysis, and various methods to accelerate biochemical assays. This talk will discuss a novel nanotechnology approach that addresses the above tasks. Our approach is based on using specially tailored dynamically tunable surfaces, which bear chemically functionalized, high-aspect ratio nanostructures, in microfluidics, enhanced mixing in a small volume, and lysis. We demonstrate a great potential of this technique in accelerating various chemical reactions and biochemical assays for high-throughput biochemical analyses.
9:00 PM - R6.11
Hydrogen Gas Sensor Made of Sol-gel Derived SnO2 Thin Films with Thermally Stable Nanoparticles
Vladimir Aroutiounian 1 , Zaven Adamian 1 , Arsen Adamian 1 , Armen Stepanyan 1 , Artsrun Arakelyan 1
1 Phys. Semiconductors and Microelectronics, Yerevan State University, Yerevan, -, Armenia
Show Abstract9:00 PM - R6.12
Fabrication of Nano-Size Metallic Powder by Microemulsion
Yong Jin Kim 1 , Ji Hun Yu 2 , Gwiy Sang Chung 3 , Jung Ho Ahn 4
1 Powder Materials Research Center, Korea Institute of Machinery and Materials, Changwon Korea (the Republic of), 2 Powder Materials Research Center, Korea Institute of Machinery and Materials, Changwon Korea (the Republic of), 3 School of Electrical Engineering, Univ. of Ulsan, Ulsan Korea (the Republic of), 4 Department of Materials Engineering, Andong National University, Andong Korea (the Republic of)
Show Abstract9:00 PM - R6.13
Metal/Porous Silicon Schottky Diode Structures as Sensors
T.D. Dzhafarov 1 2 , Cigdem Lus 1 , Sureyya Aydin 1 , Emel Cingi 1
1 Physics, Yildiz Technical University, Istanbul Turkey, 2 Physics, Azerbaijan National Academy of Sciences, Javid str., Baku Azerbaijan
Show Abstract9:00 PM - R6.14
Luminescent Carbon Nanotubes by Surface Functionalization
Donglu Shi 1 , Jie Lian 2 , Wei Wang 1 , Peng He 1 , Guokui Liu 3 , Lumin Wang 4 , Rod Ewing 2
1 Chemical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio, United States, 2 Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States, 3 Chemistry Division, Argonne National Laboratory, Argonne, Illinois, United States, 4 Department of Nuclear Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract9:00 PM - R6.15
Electrospun Tungsten Oxide Nanofibers: Fabrication and Characterization
Guan Wang 1 , Xianrong Huang 1 , Michael Dudley 1 , Pelagia-Irene Gouma 1
1 Materials Science Dept., Stony Brook University, Stony Brook, New York, United States
Show AbstractTungsten oxide nanofibers have been successfully fabricated in a way based on electrospinning technique. An ethanol solution of Poly(Vinyl Acetate)(PVAc, Mw=500,000)was mixed with Tungsten isopropoxide to form a viscous precursor solution. Composite nanofibers were obtained by electrspinning this viscous solution. By calcination of the composite fibers, pure tungsten oxide nanofibers were obtained with controllable diameters of around 100 nm. Morphology of the fibers was characterized by SEM and TEM. Calcination process was studied by DSC/TG. And the detailed structure evolution process was investigated by synchrotron based in-situ XRD. The relationship between electrospinning parameters and nanofiber diameters was studied. Specific phases of the oxide nanofibers at various calcination temperatures were obtained.
9:00 PM - R6.16
Diameter Dependent Optical Constants of Gold Meso-Particles Electrodeposited on Aluminum Films
Dmitri Brevnov 1
1 Chem & Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractSolution-based methods to synthesize metallic particles, especially of gold and silver, have been known for decades. For deposition of metallic particles on a surface, the majority of reported procedures advocate the employment of a wet-chemistry method involving a reducing agent and a high oxidation state metal precursor. Subsequently, free-standing metallic particles prepared in solution are collected and transferred to a desired substrate. Regardless of wide utilization of this approach in research laboratories, its practical usefulness is limited. Therefore, in order to increase the technological utility of metallic particles, it is important to develop deposition methods, which directly produce strongly adhesive and particulate films with a narrow distribution of particle diameters on technologically relevant substrates.In this presentation, a procedure is described for electrodeposition of meso-particles of gold on aluminum films evaporated on silicon wafers. Electrodeposition of gold results in the formation of mono-dispersed particles with RSD of 25%. The mean particle diameter can be controlled by varying the electrodeposition time in the range of 30-80 nm. The size dependent optical constants of electrodeposited particles are resolved by spectroscopic ellipsometry. The absorption peak, associated with surface plasmons, shifts from 610 to 675 nm as the mean particle diameter increases from 42 to 74 nm. The electrodeposition of gold on aluminum is compatible with standard photolithographic metrology. This, this technique can be potentially used can be used for fabrication of sensing elements and arrays.In contrast to gold particles, electrodeposition of silver results in the formation of a porous network of interconnected particles of silver. The mean particle diameter of 30 nm translates to a specific surface area of 20 m2/g. The high surface area particulate and metallic films are important for a number of applications.
9:00 PM - R6.17
Synthesis Of Silicon Nanowires By Pulsed Laser Deposition Without Catalysts Or Addictives.
Kyung Ah Jeon 1 , Hyo Jeong Son 1 , Jong Hoon Kim 1 , Kyung-Hwa Yoo 2 , Sang Yeol Lee 1
1 Electrical and Electronic Engineering, Yonsei University , Seoul Korea (the Republic of), 2 Physics, Yonsei University, Seoul Korea (the Republic of)
Show AbstractSi nanowires (NWs) were fabricated in vacuum furnace by using a Nd:YAG pulsed laser with the wavelength of 325 nm. Commercial p-type Si wafer is used for target, and any catalytic materials are not used. Scanning electron microscopy (SEM) images indicate that the diameters of Si NWs ranged from 10 to 150 nm. Si NWs have various size and shape with a substrate position inside a furnace, and their morphologic construction is reproducible. The formation mechanism of the NWs is discussed.
9:00 PM - R6.18
Thermal Stability of Supported Noble Metal Nanocluster
Galif Kutluk 1 , Shinya Yagi 2 , Hirosuke Sumida 3 , Hirofumi Namatame 1 , Masaki Taniguchi 1
1 Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshimash Japan, 2 School of Engineering, Nagoya University, Nagoya Japan, 3 Technical Research Center, Mazda Motor Co, Hiroshima Japan
Show Abstract Metal cluster dispersed on planera and oxide supported have been used extensively as model catalysts [1]. Highly dispersed metal nanocluster shows the large deviation from its bulk on the chemical and electronic properties. The catalytic activity of the cluster strongly depending on the cluster size has been reported by reaction kinetics, however the origins of the catalytic activities on the cluster surface remained unclear [2]. The aim of this work is an investigation on the size dependence of electronic structure and crystalline structure of noble metal nanoclusters Rh, Pd and Pt, respectively. The X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Fine Structure (XAFS) analysis are performed in this study. The XPS was achieved on samples heat-treated in the ranging from room temperature to 180°C under two different environments, hydrogen mixture gas (H2(10%)+N2(90%)) for the reduction and oxygen gas (O2) for the oxidization. The samples for XPS measurements are prepared by supporting the highly dispersed nanoclusters on Si substrate coated with Ta thin film (Ta/si). The CaF2 supported nanocluster samples are used for the XAFS measurement. The nanocluster Rh, Pd and Pt are deposited on substrates (Ta/Si, CaF2) by gas phase condensation and arc plasma method, respectively. The samples are exposed to the atmosphere before the analysis. The size of the clusters in diameter is controlled in range d=1.5~7.0nm. The size and morphology of clusters on the substrates are characterized by combining Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). In contrast to nanocluster Rh and Pd, no remarkable change in the 4f5/2-7/2 core level photoelectron spectra for Pt cluster (with average size d=1.5) has been observed during the heat treatment in the range from room temperature to 180°C under reduction atmosphere. The drastic changes in 3d3/2,5/2 core level photoelectron spectra of Rh and Pd nanocluster (d≦2.0nm) have been detected with increasing of annealing temperature in reduction atmospheres. The 3d3/2, 5/2 core level spectrum recorded at room temperature is characterized by component of highly oxidized states (doublet) of PdO2 (peak located at 338.7eV and 344.2eV) coexisting with the doublet of pure Pd (peak located at 335.5eV and 340.8eV). The vanishing of doublet of PdO2 has been observed with increasing the annealing temperature of the sample in the reduction atmosphere. Finally, the spectrum is dominated by 3d3/2, 5/2 doublet of pure Pd at 175°C. No agglomerations of clusters have been observed during the heat treatment. The structures of the nanocluster including XAFS will be discussed in detail at the meeting. Reference:1. W. T. Wallace, B. K. Min, D. K. Goodman, J. Mol. Catal. A 228 3-10 (2005), and there in.2. V. Johanek et al., Science, 304, 1639 (2004).
9:00 PM - R6.2
A Computational Study on CO Adsorption onto SnO2 Small Grains.
Anna Mazzone 1
1 IMM, CNR , Bologna Italy
Show Abstract9:00 PM - R6.21
Effect of Calcination Temperature on Interface Properties Between In2O3 and Au Electrode in Nano Gap Semiconductor Gas Sensors.
Jun Tamaki 1 , Jun Niimi 1 , Satoshi Konishi 2
1 Dept. of Applied Chemistry, Ritsumeikan Univ., Kusatsu-shi, Shiga Japan, 2 Dept. of Micro System Technology, Ritsumeikan Univ., Kusatsu-shi, Shiga Japan
Show Abstract A semiconductor gas sensor has a simple structure consists of a sensing oxide layer and metal electrodes for resistance measurement. Recently, we have found that the gas sensitivity was increased when the size of electrode gap was decreased comparable to size of oxide grain in NO2 sensing using WO3 thin film sensors and in Cl2 gas sensing using In2O3 thin film sensors. Namely, the WO3 sensor with 100 nm gap showed ca. 10 times higher NO2 sensitivity than that with 1500 nm gap. In the nano gap sensor, only a few grains are included in the nano gap. When the gap size is decreased, the number of oxide grains and thus that of gain boundaries are decreased, inducing the increasing contribution of oxide-electrode interface in total sensor resistance. The increasing sensitivity with decreasing gap size suggests the much higher sensitivity at interface (Si) than at grain boundary (Sgb). In the sensing of 0.5 ppm NO2 using WO3 nano gap sensor, Si was 32 times higher than Sgb. It was demonstrated that the oxide-electrode interface was important in nano gap semiconductor gas sensors. The In2O3 sensor showed different responses to Cl2 gas depending on gas concentration, i.e., the resistance increase to high concentration (>1 ppm) of Cl2 and the resistance decrease to lower concentration Cl2 (<0.5 ppm). In this study, the effect of calcination temperature on the Cl2 sensing properties of In2O3 thin film sensors was investigated for both responses. For both responses, the nano gap effect was observed for In2O3 sensor calcined at 600 °C. When the calcinaion temperature is increased, the grain size is increased and the number of grains is decreased. Thus, it is expected that the sensitivity is increased with increasing calcination temperature. For the response of resistance increase, when the calcination temperature was increased, the Cl2 gas sensitivity was higher than the theoretical expectation using Si and Sgb at 600 °C, suggesting that the interface properties was improved by calcination at high temperature. On the other hand, contrary to the expectation, the Cl2 gas sensitivity was decreased with increasing calcination temperature for the response of resistance decrease. The response of resistance decrease results from the substitution of lattice oxygen with Cl (eq. 1). Oo2- + 1/2 Cl2 = Clo- + 1/2 O2 + e-(1)It is considered that the lattice oxygen is stabilized by calcination at high temperature, preventing the substitution. In this study, how Si and Sgb were changed with calcination temperature was investigated. Namely, the changes in the interface properties between In2O3 and Au as well as the surface properties of In2O3 were investigated.
9:00 PM - R6.22
Surface Characteristics and Phase Dependence of SnO2/MoO3 Nano- binary Systems as Gas Sensors.
Jordi Arbiol 1 3 , Juan Morante 1 , E Makeeva 2 , Marina Rumyantseva 2 , Alexander Gaskov 2
1 Electronics, University of Barcelona, Barcelona Spain, 3 TEM-MAT, SCT, University of Barcelona, Barcelona Spain, 2 Chemistry Department, Moscow State University, Moscou Russian Federation
Show AbstractNowadays, the synthesis procedures of nanostructures based on complex system of metal oxide compounds are offering a rich scenario of possibilities to achieve intermediate or new properties, specially, in the binary system. There are many recently works using addition of some metal oxide to the other one for having modified catalytic properties of the system in front of certain chemical specimens. It becomes worthy in many applications from catalysis to gas sensors as well as in the field of materials for new methods for the energy production. However, there are only few detailed analysis of these binary systems.In this framework, the addition of MoO3 to SnO2 has attracted many attentions. It is assumed that the presence of Mo atoms at the surface of SnO2 changes the acidity character. Therefore, this binary system has become very promising due to its excellent catalytic properties for preparing gas sensors or catalytic materials with selective oxidation of methanol and other organic compounds. Furthermore, these performances have strengthen their practical interest by using very small nanoparticles of SnO2 (semiconducting oxide) and MoO3 (d-metal oxide exhibiting catalytic activity), presenting a very high active surface value, for the development of high catalytically active materials as the catalytic characteristics in this nano-binary system are enhanced.In this contribution, we present the overall structural and physic-chemical analysis of a series of nano-SnO2/MoO3 mixed samples starting from 0 MoO3 mol. % (pure nano-SnO2 with very small grain size about 3nm) to 100 mol. % (pure MoO3). Special attention has been paid to optical based spectroscopy -Raman and FTIR measurements- obtained at the sensor working range that determine the surface and phase characteristics of the binary compound. These measurements have had to be combined with high-resolution transmission electron microscopy (HRTEM) results, that give us the nanostructure evolution of our samples with MoO3/SnO2 mol. % ratio, and electron energy loss spectroscopy (EELS) that brings information on evolution of the local electronic states associated to the oxygen atoms in the nanoparticles. All these characterization results help us to explain the catalytic behavior and the electric characteristics of these materials as gas sensors. β-MoO3 phase in SnO2 structure as well as the presence of α-MoO3 phase nanoparticles and segregation features will be presented and discussed. The catalytic behavior will be correlated with the acidity evolution of the surface of the SnO2 caused by the presence of MoO3. Above the 20 MoO3 mol %, MoO3 appears already as (forming big particles) and the properties of the binary system become dominated by the MoO3. This structural feature explains the saturation on the sensor response. It is outstanding to point out that in this case the molybdenum oxide is found in different phases instead orthorhombic that is expected after treatment at 500C.
9:00 PM - R6.23
Metal Oxide Nanowires: Growth, Applications and Devices
Sanjay Mathur 1 , Hao Shen 1 , Sven Barth 1 , Thomas Ruegamer 1
1 , Leibniz Institute of New Materials, Saarbruecken Germany
Show AbstractOne dimensional (1D) inorganic materials are gaining increasing attention because of their unique structural features and interesting functional properties. Given the structural stability, they show promising application potential in vacuum as well as in oxidizing atmospheres, which provides them a competitive edge over their carbon-based counterparts. A number of synthetic procedures have been developed and demonstrated for 1D nanostructures that have led to intriguing morphological variations (wires, tubes, belts, rods, etc.), however the control over radial and axial dimensions remains a continuing challenge. In addition, the choice of material is rather limited. We have developed a generic approach for the size-selective and site-specific growth of nanowires by combining vapor-liquid-solid (VLS) approach with the chemical influence of molecular precursors. The synthesis of nanowires (NWs) is based on the decomposition of discrete molecular species in the liquefied Au-Si alloy, which allows growing nanowires at low-temperatures with a precise control over their diameter and length. The precursor chemistry can be tuned to facilitate the stripping of organic ligands and to achieve complete decomposition that is critical for maintaining the gas phase super-saturation necessary for 1D growth. High-yield synthesis of NWs of tin, vanadium and iron oxides was performed by the chemical vapor deposition of appropriate metal-organic precursors. Axial and radial dimensions of the NWs were varied in the ranges 50-1500 nm and 25-40 µm, respectively by adjusting the precursor feedstock, deposition temperature, and catalyst size. We have investigated the device potential of these building blocks as photo- and gas sensors. For instance, illuminating tin oxide NWs with UV photons triggers interesting photo-conductance, which can be modulated by tuning the wire diameter as demonstrated for samples possessing radial dimensions in the range 50–1000 nms. The stable photo-response over several on-off cycles demonstrated their potential for applications in UV detectors or optical switches, where the NWs can act as resistive elements whose conductance changes by charge-transfer processes. In addition, tin oxide NWs were grown on sensor platforms and their response towards CO was compared with nanostructured tin oxide films. This talk will address the generic feature of our approach for the synthesis of oxide nanowires of various compositions and present the results obtained on device applications.
9:00 PM - R6.24
General Synthesis of Highly Ordered Multicomponent Nanostructures from Chemical Modification Sol-gel Process
Jie Fan 1 , Shannon Boettcher 1 , Galen Stucky 1
1 Chemistry, university of california, Santa Barbara, California, United States
Show AbstractMost advanced materials are multicomponent systems having two or more types of cations. Recently, more and more efforts were focused on fabrication of these systems structured on nanoscale due to their promising electrical, optical and catalytic properties. To develop such a nanostructured multicomponent system by sol-gel process, one needs the capability to prepare gels of high homogeneity in which cations of various kinds are distributed uniformly at an atomic scale through M1-linker-M2 bridges. A major problem in forming homogeneous multicomponent gels is the unequal condensation rates of the metal sources, which limits a general route to access these materials. In this work, we demonstrated a general strategy to synthesize highly ordered nanostructured multicomponent systems by successful control of condensation rate of metal precursors. Most mixed metal oxides (such as PbTiO and BaZrO), with 3-D cubic or 2D hexagonal structures, have been prepared by this route. Their dielectric and ionic transfer properties have also been explored.
9:00 PM - R6.25
Novel WO3 based Nanostructured Thin Films as Gas Sensor
Arun Prasad 1 , Pelagia Gouma 1
1 , SUNY Stony Brook, Stony Brook, New York, United States
Show AbstractTungsten trioxide thin films prepared by acidic precipitation technique have been tested and characterized as novel materials for gas sensing applications. WO3 powders of two different polymorphs (monoclinic and orthorhombic phases) are obtained from acid hydrolysis of sodium tungstate solution. The powders are dispersed in n-butanol and spun coated on sensor substrates made of alumina with gold interdigitated electrodes. SEM experiments on the films after a stabilization heat treatment at 500°C for 8 hours revealed that the grain sizes were around 300 nm for films of monoclinic phase and 150 nm for films of orthorhombic phase. XRD characterization and DSC studies confirm that the monoclinic phase transforms to orthorhombic phase around 400°C. Sensing experiments were carried out in a flow controlled sensing setup in the temperature range of 200°C – 500°C. The gases used for testing were NO2 and NH3 with synthetic air in the background. The sensitivities of the films towards the two test gases were plotted against concentration for different operating temperatures. Both phases showed selective detection towards NO2 over NH3. Monoclinic phase is suitable for low temperature (200°C-300°C) detection of NO2. An adsorption based sensing mechanism is used to explain the selectivity towards NO2.
9:00 PM - R6.26
Tin Dioxide Nanodimensional Film Based H2 sensor.
Serghei Dmitriev 1
1 Center of Applied and Environmental Chemistry, Moldova State University, Chisinau Moldova (the Republic of)
Show AbstractPaper presents results of investigation aimed at the development of tin dioxide nanodimensional film gas sensors (NDFGS) with high sensitivity to hydrogen. Specifics of the performed research consist in the approach based on the combination of utilization nanodimensional metal oxide film, as gas sensitive element of device, and group electron technology methods that allows to arranging from small to large scale manufacturing of given NDFGS.Gas sensitive nanodimensional film (NDF) had been formatted by means of chemical spray pyrolysis method on the both ceramic substrate for study and optimization of electrophysical and gas sensitive characteristics and “chip” of gas sensor (GS) preliminarily produced through group electron technology. Films were deposited at the temperatures in interval 400-500oC from water solutions of SnCl4.5H2O precursor. The thickness of SnO2 films was varied in the range 40-80 nm. Study of electrophysical characteristics of obtained layers has shown that the last one possess resistance on the level 105-106 Ohm/ at the working temperatures of GS. Gas sensitivity was determined as ratio of SnO2 film resistance in the pure air and in the presence of gas impurity in atmosphere (S=Rgas/Rair). Values of R were determined through Van-der-Pauw method.X-ray and SEM investigation has allowed establishing the interconnection between technologic parameters, nanostructure and gas sensitive characteristics of obtained films.Gas sensitivity S of the deposited undoped films has amounted 9-10 relative units to the 100 ppm of hydrogen in air. Modification of gas sensitive properties of tin dioxide NDF through bulk and surface doping with Pd has allowed to increasing hydrogen sensitivity up to almost 104 rel. units, providing the detection of hydrogen at the concentration on the level 1 ppm and shift of the sensitivity maximum from 350oC (in the case of undoped films) to 150oC (Pd doped NDF). Performed sensor chip thermal regimes modeling has allowed developing of the NDFGS topology with reduced power consumption (< 30 mW).
9:00 PM - R6.27
Nano Ordered High Throughput Diagnostic Platforms.
Ravikiran Kondama Reddy 1 , Shalini Prasad 1
1 ECE, Portland State University,OR, Portland, Oregon, United States
Show AbstractHigh throughput systems require rapid analysis of small sample volumes for short durations of time. Lab on a chip technology has been implemented for the design of such platforms and it finds its basis in miniaturization. For detection of disease and any other perturbations resulting in human performance decrements portable sensitive systems with small volume capability are essential. Modulations to various cellular and sub cellular species like proteins and nucleic acids are detected using this platform. These function as the indicators of disease. Detection is achieved by particle manipulation and trapping based on variations to size, dielectric property, weight, surface fictionalization. Nano ordered materials including nano-tubes, nano- wires, nano porous material which are assembled by NEMS and Electron Chemistry form the substrates for the aforesaid platforms. Electrical identifiers based on variations to binding properties and micro environment changes were used to identify the basis of the diseases. This provides us with a rapid assessment suitable for real time applications
9:00 PM - R6.28
Ultra-narrow Width Si FET Integrated with Micro-Fluidic Delivery for Charge Based Sensing
Ali Gokirmak 1 , Sandip Tiwari 1
1 Electrical and Computer Engineering, Cornell University, Ithaca, New York, United States
Show AbstractThe semiconductor industry has developed tools and expertise to build very small scale, very sensitive electronic structures. In recent years there has been a significant effort in building micro/nano fluidic systems using the tools developed for the semiconductor industry. Successful integration of field effect transistors with nano-fluidic systems can lead to extremely sensitive charge detectors which can be used for identification of large molecules in liquid samples. However, integration of the semiconductor devices with on chip micro/nano-fludic systems have significant materials, process and design challenges. We have developed techniques to monolithically integrate an ultra-narrow-channel field effect transistor (FET) with a nanoscale fluidic delivery tunnel passing underneath the gate for ultra-sensitive detection. A silicon nitride based shallow trench isolation (STI) scheme is used for electrical isolation. The device is designed to be used as an FET based sensor for sequencing of DNA, RNA and proteins, by detecting the local charge variations along the chains of these molecules as they are passed between the gate and the channel of the FET in an aqueous solution. The channel widths of the FETs, fabricated on bulk Si, are sub-10 nm with remarkable uniformity. The gates of these FETs are suspended 10 to 30 nm above their channels and the tunnels going through the devices are monolithically integrated with micro-fluidic sample delivery tunnels leading to the device. A 2-3 nm oxide layer is grown on the channel surface in order to prevent electrical leakage and electrolysis of water during the measurements. The tunnel height of the successfully fabricated devices is as small as 5 nm after growth of thermal oxide on the Si channel and the polysilicon gate surfaces for electrical isolation.The peripheral leakage currents are extremely important for ultra narrow channel FETs. A side-gated approach is utilized to suppress these leakage currents below 50 fA, leading to improved transistor behavior and sensitivity to charge perturbations. Suppression of leakage currents also significantly reduces the noise contribution from the fluctuations in the current level due to trapping and untrapping events taking place at the Si-STI interfaces. Side-gated FET structure allows electrostatic confinement of the electrons in the channel for increased spatial resolution.CMOS compatible processes and optical lithography are used for the fabrication these devices, allowing easy transition to mass production in commercial CMOS fabrication facilities. The device structure, characteristics of sub-10 nm width devices, the integration technology, and its application will be summarized.
9:00 PM - R6.29
Selective and Sensitive Hydrocarbon Detection Based on Tailored CdSe Quantum Dot/Polymer System.
Mayrita Arrandale 1 , Zhouying Zhao 1 , Oxana Vassiltsova 2 1 , Marina Petrukhina 2 , Michael Carpenter 1
1 College of Nanoscale Science and Engineering, The University at Albany-State University of New York, Albany, New York, United States, 2 Chemistry, The University at Albany - State University of New York, Albany, New York, United States
Show AbstractOur surface tailored CdSe quantum dots (QDs) incorporated into a PMMA host can offer unique capabilities for selective and sensitive detection of toxic hydrocarbons found in soil, water and air. Environmental fluorescence spectroscopy has afforded studies of how the fluorescence sensing properties of the QD change with respect to the tailor-designed fluorinated single or polyarene aromatic sensing groups attached to the QDs surface. Our efforts have focused primarily on the sensing of xylene and toluene, where we have achieved a 15 ppm to 100s ppb level sensitivity towards xylenes in air, which is about 2-3 times the sensitivity measured for toluene in air. Sensing studies extended to benzene and ethyl benzene will also be presented.
9:00 PM - R6.3
A1Bi3C6 Thin Films as NO Sensors.
Halyna Khlyap 1 , Violetta Bilozertseva 2 , Nina Dyakonenko 2 , Dmitrii Gaman 2 , Andrii Mamalui 2
1 , University of Technology, Kaiserslautern Germany, 2 Physics, National Technical University "KPI", Kharkov Ukraine
Show Abstract9:00 PM - R6.30
Characterization of TiO2 Derived Nanostructures for Gas Sensing Applications
Jordi Rodriguez 1 , Joan Ramon Morante 1 , Albert Cirera 1 , Polona Umek 3 , Jordi Arbiol 1 , Denis Arcon 2 3
1 electronics, universitat de barcelona, barcelona Spain, 3 Faculty for Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia Slovenia, 2 , Institute Jozef Stefan, Ljubljana, Slovenia Slovenia
Show AbstractTitania based nanotubes and nanoribbons were prepared hydrothermally via a reaction of anatase TiO2 powder with a NaOH solution. Nanotubes were synthesized at 100°C and nanoribbons at 200°C. Morphological and structural characterization was carried out using TEM, EPR, EDX and XRD. The specific surface area was studied by the BET technique. For the electrical resistance measurements, these materials were mixed with a binder and then deposited on platforms with electrodes and heater. Before gas measurements, sensors were dried at 100°C during several days. Different gas concentrations were obtained mixing different flows controlled by massflow controllers. A stainless steel chamber of 200ml and a flow of 200ml/min were used. Titania based nanotubes have a diameter between 10-20 nm and can reach up to 500 nm in length. Nanoribbons have a width between 150nm and 300nm. From EDX analysis, nanotubes consist on 44.8wt.% of titanium and 32 wt.% of oxygen while nanoribbons consist on 43.3 wt. % of titanium and 31.8 wt. % of oxygen. Sodium content also appears due to remaining synthesis products. After hydrothermal process, a cleaning step with HCl is required to form the definitive nanostructures. A (H,Na)TiO stochiometry for hydrothermal nanotubes and nanoribbons is purposed. XRD confirms that our material has the same titanate structure. Also EELS spectra presents hydrogen related features. BET studies show that nanoribbons specific surface area is 30m2/g while nanotubes specific surface area is 230 m2/g. One-dimensional nanostructures were exposed to NO2 gas for EPR and electrical resistance measurements. In the case of nanoribbons. The optimum working temperature was found to be 150°C. Response can be expected to be higher at lower temperatures, however sensors would be too much resistive. Sensor response based on nanoribbons operating at this temperature and 10%RH to different concentrations of NO2 is also studied. Response of 8% response is obtained at at 300 ppb. In spite of the high response of nanoribbons, nanotubes present a poor sensitivity although their high surface area. Only a 10% response is obtained for 7.5ppm NO2. The nanotubes based sensors present very high resistance and they can not be measured below 150°C with the actual electrode geometry. The optimum temperature is below 150°C but resistive sensors would not be operative. For EPR, adsorption took place at room temperature and 300 Torr of initial pressure of NO2 gas. A stronger adsorption of NO2 gas is observed in the case of nanotubes, what is expected since their specific surface area is for factor 7 higher that one of nanoribbons. The adsorption of NO2 was investigated with ESR (electron spin resonance) technique, which enabled us to build a picture of the surface properties of the TiO2 based nanotubes and nanoribbons and the way NO2 molecules are adsorbed.
9:00 PM - R6.31
Nanoscaled p-type Semiconductors for Gas Sensing: Nanopowders, Nanofilms, and Nanowires.
Kathy Sahner 1 , Perena Gouma 2 , Ralf Moos 1
1 Functional Materials, University of Bayreuth, Bayreuth Germany, 2 Dept. of Materials Science and Engineering, SUNY at Stony Brook, Stony Brook, New York, United States
Show Abstract9:00 PM - R6.32
A Study of the Design and Engineering of a Novel 3D Polymeric Scaffold Functionalised to Support Crystal Growth.
Brigid Heywood 1 2 , Adam Ovens 1 2 , Andrew Ray 2 , Graham Mitchell 2
1 Chemistry, Open University, UK, Milton Keynes United Kingdom, 2 Chemistry, Keele University, Keele , Staffs United Kingdom
Show Abstract9:00 PM - R6.33
Synthesis of Meso-porous SiO2 Ceramics Through Directional Solidification and Freeze-Drying
Predrag Kisa 1 , Chris Pekor 1 , Ian Nettleship 1 , Nicholas Eror 1
1 Materials Science and Egineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show Abstract9:00 PM - R6.34
Platform based Detection Technologies from Micro scale to Nanoscale
Shalini Prasad 1
1 ECE, Portland State University, Portland, Oregon, United States
Show Abstractsensitive bio chemical sensors for air based as well as fluidic environments. We incorporate the principles of micro cavity resonators to develop sensors that identify air based chemical agents by a variation to the quality factor and optical resonance frequency. Micro ring resonators are fabricated on a platform by incorporating the principles of optical lithography and individual micro cavities are functionalized to detect specific chemical agents. Unique optical spectra are obtained to indicate the detection of specific agents. The detection sensitivity and sensor parameters are compared with carbon nanotube based bio-chemical sensors fabricated by integrating micro fabricated platform with electrically assembled functional nanoube arrays for detecting chemical agents. The integration methodologies for both the sensor platforms are explored with the goal of realization of a total analysis system.
9:00 PM - R6.35
CO and NOx Gas Sensor Based on SnO2 Semiconducting Nanowires
Jae-Hwan Park 1 , Young-Jin Choi 1 2 , In-Sung Hwang 1 2 , Jong-Heun Lee 2 , Jae-Gwan Park 1
1 Materials Division, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Department of Materials Science and Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractThe SnO2 nanowires were synthesized by a simple thermal evaporation process using Sn metal powders at low temperature of 600~700oC. The diameter of the nanowires ranged from 50 nm to 200 nm depending on the processing temperature and the oxygen content with Ar carrier gas. X-ray diffraction analysis and transmission electron microscopy analysis indicated that the SnO2 nanowires are single crystals. The gas sensing properties of the sensors to carbon monoxide, nitrogen dioxide, and hydrogen were also investigated. The SnO2 nanowires showed high and fast response to both carbon monoxide and nitrogen dioxide gases.
9:00 PM - R6.36
Integration of Indium Oxide Nanowire Sensors with Low-power Microheaters.
Daihua Zhang 1 , Koungmin Ryu 1 , Chongwu Zhou 1
1 Electrical Engineering, University of Souther California, Los Angeles, California, United States
Show AbstractWe have assembled indium oxide nanowire sensors with low-power microheaters for detecting a broad class of chemical vapors. The sensing ability of individual indium oxide nanowires was systematically investigated at different temperatures and gas concentrations. The electrical conductance of a heated nanowire is highly sensitive to a wide variety of chem/bio species including oxygen, ethanol, carbon monoxide, nitrogen dioxide and dimethylmethylphosphonate, etc. We have further demonstrated that Au-functionalized indium oxide nanowires exhibit a dramatic improvement in sensitivity toward certain chemicals due to the enhanced catalytic dissociation of the molecular adsorbate on the Au nanoparticle surfaces. This transduction mechanism can form the basis for a fast, low-power sorption-based chemical sensor. Our novel approach will potentially allow for the large-scale fabrication of high-density nanosensor arrays.
9:00 PM - R6.37
Synthesis and Characterization of ITO Nanofibers by Electrospinning.
Yong Shi 1 , Shiyou Xu 1
1 Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, United States
Show Abstract9:00 PM - R6.38
Sub-micron Emission and Charge Transport Modifications of Multi-dimensional ZnO.
Ran Shi Wang 1 , Jin An 1 , J.B. Xu 2 , H.C. Ong 1
1 Physics, The Chinese University of Hong Kong, Hong Kong Hong Kong, 2 Electronic Engineering, The Chinese University of Hong Kong, Hong Kong Hong Kong
Show Abstract9:00 PM - R6.39
Preparation and Characterization of Nano-grain Size Commercially Pure Titanium: A Potential Material as Dental Implants.
Shahabeddin Faghihi 1 2 3 , Fereshteh Azari 2 , Jerzy A Szpunar 3 , Hojatolah Vali 2 , Maryam Tabrizian 1
1 Biomedical Engineering, McGill University, Montreal, Quebec, Canada, 2 Anatomy and cell biology, McGill University, Montreal, Quebec, Canada, 3 Mining, Metals and Materials Engineering, McGill University, Montreal, Quebec, Canada
Show Abstract9:00 PM - R6.4
In Vivo Cancer Diagnosis Using Well Defined Multifunctional Magnetic Nanocrystals.
Jae-Hyun Lee 1 , Young-wook Jun 1 , Jin-sil Choi 1 , Jinwoo Cheon 1
1 Chemistry, Yonsei University , Seoul Korea (the Republic of)
Show AbstractAlthough superparamagnetic iron oxide nanocrystals have been extensively studied as excellent magnetic resonance imaging (MRI) probes for various cell trafficking, gene expression, and cancer diagnosis, their success in in vivo applications for the diagnosis of cancer is rare. We report a unique protocol for the development of well-defined magnetic nanocrystal probe system using highly bio-compatible magnetite nanocrystals with multiple capabilities such as small size, strong magnetism, and the possession of active functionality for desired receptors. Upon conjugation to cancer targeting antibody, these nanocrystal conjugates are utilized as MRI probes for in vivo diagnosis of cancer and for the monitoring of cancer targeting events in live animals.
9:00 PM - R6.40
Adhesion of Pulsed Laser Deposited Calcium Phosphate Films to Titanium Alloy and Zirconia Substrates.
Hye-Lee Kim 1 , Sang-Wook Lee 1 , Kee-Man Kim 1 , Young-Sun Kim 1 , Won-Jun Lee 1 , Dae-Joon Kim 1 , Jung-Suk Han 2
1 Department of Advanced Materials Engineering and Bioengineering Research Center, Sejong University, Seoul Korea (the Republic of), 2 Department of Prosthodontics and Dental Research Center, College of Dentistry, Seoul National University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - R6.5
DRUV-Vis-NIR and EPR Characterization of MoO3-WO3 Single and Binary Oxides.
Sara Morandi 1 , Maria Cristina Paganini 1 , Elio Giamello 1 , Giovanna Ghiotti 1
1 , University of Torino, Torino Italy
Show AbstractMoO3 and WO3 are well known metal oxides extensively studied for their application in gas sensing devices. They are semiconductor oxides owing the capability to lose oxygen in reducing conditions and to restore the lost oxygen in oxidizing ones. Frequently, metal oxide combinations were tailored to achieve desired properties and to modify sensor performances. Recent studies focused on MoO3-WO3 mixed oxides report on their promising gas sensing potential. We prepared and characterized a Mo/W mixed oxide (Mo/W nominal ratio = 80/20) and for comparison purposes also MoO3 and WO3. Morphological and structural characterizations were carried out by SEM and XRD techniques, spectroscopic characterization by diffuse reflectance UV-Vis-NIR and EPR spectroscopies. DRUV-Vis-NIR spectra were recorded at room temperature after treatments in vacuum and after interaction with NO2/O2 and CO/O2 mixtures at increasing temperature up to 673 K. EPR spectra were recorded in X-band at 77 K after treatments in vacuum at increasing temperature and subsequently in dry oxygen at increasing temperature.XRD analysis showed that the mixed oxide is a new phase different from those of MoO3 and WO3. XRD patterns of the Mo/W oxide recorded after reducing treatment in vacuum at 723 K showed the appearance of peaks due to a crystalline phase different from that of the completely oxidized sample. This result enlightened the capability of the mixed oxide of losing oxygen not only from the surface but also in the bulk, changing its crystalline structure in some regions. Otherwise, MoO3 and WO3 do not change their XRD patterns after reducing treatments.DRUV-Vis-NIR spectra recorded after reducing treatments at increasing temperature (heating in vacuum or in a CO/O2 mixture) showed the formation of a variety of broad absorptions in the visible and near IR regions for all the oxides studied. These absorptions are eroded during oxidizing treatments at increasing temperature. These broad absorptions are assignable to electronic transitions from energy levels in the band gap, related to defects originated by the oxygen loss, to the conduction band. The most common defect in transition metal oxides is polaron, i.e. the trapping of an electron at one cationic site by the local lattice polarization that it causes. Therefore, the absorptions in the Vis-NIR region can be interpreted as: (i) intervalence charge transfers of the type [M5+-O-M6+]-[M6+-O-M5+] also called polaronic transitions; (ii) M5+ d-d transitions; (iii) M5+-O2- ligand to metal charge transfers. EPR characterization confirmed the presence of electrons trapped at cationic sites for all the three oxides. It was also possible to confirm for WO3 and MoO3 the loss of oxygen from the surface or sub-surface atomic layers and for the mixed oxide the presence of oxygen defects deeper in the bulk. Moreover, electrons trapped in defect sites of Mo/W oxide show peculiar EPR signals different from those present on MoO3 and WO3.
9:00 PM - R6.7
All-Optical Detection of CO and NO2 at High Temperatures by Au-YSZ Nanocomposites.
George Sirinakis 1 , Rezina Siddique 1 , Ian Manning 1 , Phillip Rogers 1 , Michael Carpenter 1
1 College of Nanoscale Science and Engineering, The University at Albany-State University of New York, Albany, New York, United States
Show Abstract9:00 PM - R6.8
Synthesis and Characterization of Tungsten Oxides for Gas Sensing Applications.
Pascal Ifeacho 1 , Tim Huelser 1 2 , Hartmut Wiggers 1 , Christof Schulz 1
1 Institute for combustion and gas dynamics, University of Duisburg-Essen, Duisburg Germany, 2 Institute of physics, University of Duisburg-Essen, Duisburg Germany
Show AbstractTungsten oxide is increasingly attracting attention as a material for the development of gas sensors. It has the ability to undergo large changes in conductivity in the presence of different gases, while showing quick response times. It shows high selectivity, and previous investigations have confirmed its suitability for sensing ethanol, O3 and NOx. Furthermore, its selectivity and sensitivity is complementary to well established SnO2 sensor materials, and thus can be used for combinational sensor technology. The challenges of developing a tungsten oxide sensor, involves effective synthesis and control of high surface area materials, as well as controlling material properties such as morphology. In this study, the synthesis of WO3 and WO2.x (2.6≥ x ≤2.8) are investigated by doping a premixed H2/O2/Ar flame with varying concentrations of WF6 in a low pressure reactor. The setup consists of 3 segments, in which a molecular beam arises due to the pressure differences in the various segments. This provides the possibility for online characterization of the particle size using a particle mass spectrometer (PMS). Furthermore, the molecular beam facilitates the deposition of particles on substrates such as interdigital capacitors and TEM grids, for ex-situ characterization. The PMS results indicate that mean particle diameters dp between 5 nm and 9 nm of the as-synthesized metal oxides could be obtained by varying the residence time and precursor concentration in the reactor. This result was further validated with BET measurements, which yielded a 91 m2/gm surface area, corresponding to a spherical diameter of 9 nm. H2/O2 ratios of 1.6 and 0.63 were selected to influence the stoichiometry of the powders, resulting in a blue coloured WO2.x and a white WO3. Non-stoichiometric metal oxides are interesting for gas sensing applications due to high charge carrier mobility as a result of oxygen vacancies. XRD analyses of the as-synthesized materials indicate that the powders are mostly amorphous, whereby the observed broad reflexes can be ordered to the orthorhombic structure of β-WO3. Thermal annealing at 700°C for 3 hrs in air resulted in polycrystalline WO3 comprising of both monoclinic and orthorhombic phases. The TEM image analysis shows the particles exhibit spherical morphology with some degree of agglomeration. Impedance Spectroscopy was used for electrical characterization of tungsten oxide thin films with a thickness of 50 nm. However, temperature dependent conductivity of the material deposited on interdigital capacitors with a width of 600 nm was investigated. Sensitivity experiments reveal different behaviours in low concentrations of NO and CO, whereby, the thin film sensitivity for NO was found to be better than that for CO as expected for tungsten oxides.
9:00 PM - R6.9
Mesostructured WO3 as a sensing material for NO2 detection.
E. Rossinyol 1 , A. Prim 1 , J. Arbiol 1 , F. Peiro 1 , A. Cornet 1 , J.R. Morante 1 , L. A. Solovyov 2 , B. Tian 3 , T. Bo 3 , D. Zhao 3
1 Electronics Materials and Engineering, Electronics Department, University of Barcelona, Barcelona Spain, 2 , Institute of Chemistry and Chemical Technology, Krasnoyarsk Russian Federation, 3 Molecular Catalysis and Innovative Materials Laboratory, Department of Chemistry, Fudan University, Shanghai China
Show AbstractTungsten oxide, with or without catalytic additives, is widely used for the detection of NO2, important for monitoring environmental pollution resulting from combustion or automotive emissions. As the adsorption of gas molecules takes place at the surface, one of the most important issues for tailoring the properties of the material as a gas sensor is the control of the active surface area. With the aim of increasing this active surface we synthesized mesostructured WO3 in a hard template route, using two different mesoporous templates: i) the three-dimensional cubic (space group la-3d) named KIT-6, ii) the two-dimensional hexagonal structure (space group p6mm) named SBA-15. Both materials present uniform small sizes of stabilised crystals and high values of active surface areas but with different structures, hexagonal and gyroidal, in order to point out the possible structure effects on the sensing process[1]. In this work, we present the response of the thick film sensors based WO3 mesostructured nanopowders printings to low concentrations of NO2. The screen-printed sensors exhibit very high sensitivities for concentrations of NO2 from 90ppb to 2ppm, pointing out differences in the sensing processes for the two structures, such as different response time and different sensitivity dependence on the gas concentration. Moreover, the influence of Cr and Cu on mesostructured WO3 sensing properties have been studied using samples with different concentrations of catalytic additives introduced in WO3 by the impregnation method. We will report the structural characterisation by TEM, XRD, XPS and Raman spectroscopy in order to identify the location of the additive, its oxidation state, and its main phase. The influence of catalytic additives in the sensing mechanism will be also discussed.[1] Rossinyol, E.; Arbiol, J.; Peiro, F.; Cornet, A.; Morante, J. R.; Tian, B.; Bo, T.; Zhao, D. Sensors and Actuators, B: Chemical B109(1), 57-63. ISSN:0925-4005, (2005)
Symposium Organizers
Elisabetta Comini Universita' di Brescia
Pelagia Irene Gouma State University of New York-Stony Brook
Vincenzo Guidi University of Ferrara
David Kubinski Ford Motor Company
R7: Oxide Nanostructures for Sensing
Session Chairs
Elisabetta Comini
Juan Morante
Thursday AM, April 20, 2006
Room 3022 (Moscone West)
9:00 AM - R7.1
Sub-Second Humidity Sensing based on Nanostructured Narrow-Bandpass Optical Filters.
John Steele 1 , Andy van Popta 1 , Matthew Hawkeye 1 , Jeremy Sit 1 , Michael Brett 1
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Show Abstract9:15 AM - R7.2
WAXS and PDF-Based Analyses of Chromium Doping in Nanocrystalline Titania (Anatase and Brookite).
Hengzhong Zhang 1 , Benjamin Gilbert 2 , Bin Chen 1 , Jillian Banfield 1 2
1 Department of Earth & Planetary Science, University of California - Berkeley, Berkeley, California, United States, 2 Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractCr-doped titania is an oxygen sensor material. The Cr content determines the concentration of oxygen vacancies and hence controls the function of the sensor. We used wide angle x-ray scattering (WAXS) to study the influence of the Cr content (0.5-10% Cr:Ti molar ratio) and the heat treatment (300 – 700 °C, 2h , air) on the structures of Cr-doped nanocrystalline titania samples. Real space Rietveld fitting of the pair distribution function (PDF) derived from WAXS data was used to determine the phase composition and the lattice parameters. The unheated Cr-doped titania samples consisted of ~ 6 nm anatase (~53-59 %) and ~ 6 nm brookite. We documented volume expansion of 1.20-1.26 % for Cr-doped anatase and 1.58-2.03% for Cr-doped brookite compared to the respective pure bulk phases. The cell parameters are only slightly dependent on the Cr content over the range of Cr contents studied. The experimental observations are consistent with a structural model in which increase in cell parameters due to Cr(III) substitution for Ti(IV) are largely offset by cell parameter decrease due to oxygen vacancies, especially at higher Cr concentrations. Sample heating increased the particle size and changed the phase composition. Anatase and brookite were found in samples heated below 600 °C, and rutile formed in samples heated above 600 °C. For anatase, a decreases but c increases with increasing heating temperature but for brookite, the cell parameters only change after rutile begins to form (i.e. 600 °C). These observations suggest octahedral deformation, possibly as the result of thermally activated redistribution of Cr. Our results show that Cr doping and heating can significantly affect the structural parameters of TiO2 that are essential for oxygen sensor performance.
9:30 AM - **R7.3
Direct Formation of Highly Porous Gas-sensing Films by In-situ Thermophoretic Deposition of Nanoparticles from the Aerosol Phase.
Nicolae Barsan 1 , Sahm Thorsten 1 , Alexander Gurlo 1 , Lutz Maedler 2 , Udo Weimar 1
1 Institute of Physical Chemistry, University of Tuebingen, Tuebingen Germany, 2 Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California, United States
Show AbstractCurrent state-of-the-art sensors have important technical limitations with regard to the deposition procedure. Variations in the deposition parameters such as including a new film or varying film thickness or functionalization (doping) of the films and batch production are difficult to implement and require repetition of the full process. Dry aerosol synthesis applying the Flame Spray Prolysis (FSP) has been used for direct (in-situ) deposition of pure and functionalized (doped) sensing materials. This eliminates these difficulties, and functionalization of the sensing films can be realized during one process step on ceramic (planar) and micro-machined substrates.Highly-crystalline SnO2 nano-powders of sub-micrometer grain sizes were made by the FSP technique. The aerosol generated by the dry FSP method was directly, in-situ thermophoretically deposited onto interdigitated Pt-electrodes to form a porous, thick film of controlled thickness within the active sensor area. Tin oxide grain size (10 nm) and a high film porosity (98 %) were used for film thicknesses from 9 to 40 nm using different deposition times. The as-obtained sensors show good homogeneity of the sensing film and good sensor performance. This innovative process has advantages such as superior control over the microstructure and morphology of the nano-powders compared to classical wet-chemistry methods. Furthermore, the process is clean and fast (minutes compared to days for comparable quantities) and also allows for in-situ functionalization. The in-situ prepared sensors of pure SnO2 and Pt doped SnO2 exhibited high carbon monoxide (CO) sensor signals (8 for 50 ppm CO in dry air at 350°C), good reproducibility, high analytical sensitivity and a remarkably low detection limit (1 ppm CO in dry air at 350°C). A combination of various films with different functions (filtering, sensing) by the same deposition process is possible which will enable direct construction of fully functional sensors in very short times using a simple and clean fabrication process. The structure of the nanoparticle film consists of a gas-solid network either formed by individual particles or agglomerates. The formation of the porous structure and its final properties can be described because the particles are deposited particle by particle or agglomerate by agglomerate to form the porous layer. This way the film structure can be modeled by a Monte Carlo simulation. Detailed information on the porous structure provides information on the transduction pathway and mass transfer parameters of the gas diffusing towards the solid interface.
10:00 AM - R7.4
Zinc Ooxide Thin Films used as UV and Gas Detectors Produced and Working at Room Temperature.
Ana Pimentel 1 , Rodrigo Martins 1 , Elvira Fortunato 1
1 Materials Science, FCT-UNL, Caparica Portugal
Show Abstract10:15 AM - R7.5
Investigation on Humidity Effect to SnO2-based Sensors in CO Detection.
Cesare Malagu' 1 , Michele Benetti 1 , Maria Cristina Carotta 1 , Alessio Giberti 1 , Vincenzo Guidi 1 , Luciano Milano 1 , Marco Piga 1 , Giuliano Martinelli 1
1 , university of Ferrara, ferrara Italy
Show AbstractIt is well known that humidity strongly interacts with SnO2 in the process of CO detection. The main theoretical approach to investigate the humidity role regards a competing effect between OH- groups and CO in the occupation of surface states, through bond formation with chemisorbed oxygen species. A different interpretation concerns the creation of surface dipoles that modify the surface energy by a change in the electron affinity of the material.Despite the interpretations found in the literature, it is still unclear whether water vapour presence reduces the sensitivity to CO or increases it. Aim of this work is to estimate the contribution of water on CO detection in real operating conditions to obtain a repeatable sensors signal. A dedicated experiment was then performed with a set of SnO2 sensors placed in a sealed chamber specific for the flow-through technique. A test chamber was placed in a thermostatic compartment to measure the room temperature with a precision of 0.5 degrees centigrade. The working temperature of the sensors was determined via a platinum resistor and the presence of water vapour in the test chamber was obtained via flow humidification. Three mass flow meters were employed to obtained various total flows in the test chamber and all wished ratios of CO and water vapour concentrations.It turned out that water partial pressure and not the relative humidity variations directly affect the sensors behaviour. To prove this, the partial pressure of water vapour was kept constant while varying the temperature of the test chamber and large relative humidity variations could be induced without a corresponding variation of the sensors signal. On the other hand, the sensors conductance proved to follow the water pressure variations when the temperature was kept constant. For a fixed temperature, it was then possible to fit the set of conductance values of a sensor with a continuous surface. CO concentration varied between 0-40 ppm and H2O vapour pressure between 500-4000 Pa, which represents the typical range of yearly variation. After the analytical surface is built for a sensor, the expression is inverted and every unknown CO concentration can be univocally determined by the sensor’s conductance once the water partial pressure is known. The surface represents a tool for compensating the water effect in CO detection.As soon as the rate of water-vapour pressure variation is slower than 500 Pa/h the sensors conductance, G is repeatable. This means that G is a single value function of temperature, water vapour and CO concentration. After a quicker water vapour variation instead, G has different values at the same temperature, water vapour pressure and CO concentration present before the variation. On the contrary, the sensitivity (dG/d[CO]) is almost constant, especially at the highest (>10ppm) CO concentrations. An explanation of this behaviour is proposed by the investigation of surface chemical reactions far from equilibrium.
10:30 AM - R7.6
Inverse Opal Nanoassemblies: Novel Architectures for Gas Sensors. The SnO2:Zn Case.
Alessandra Sutti 1 , Gianluca Calestani 1 , Chiara Dionigi 2 , Camilla Baratto 3 , Guido Faglia 3 , Giorgio Sberveglieri 3
1 Dipartimento di Chimica G.I.A.F, Universita' degli Studi di Parma, Parma Italy, 2 ISMN, CNR, Bologna Italy, 3 Dipartimento di Chimica e Fisica per l'Ingegneria e i Materiali, Universita' di Brescia, INFM - CNR, SENSOR Laboratories, Brescia Italy
Show AbstractGas sensing technologies are on the edge of the current environmental monitoring research, which is moving towards energy saving highly sensitive systems. Improving surface area and sensitivity, reducing the crystalline grain size and lowering the sensor working temperature are the main goals to set in this area. Owing to their highly porous interconnected structure assuring a huge surface for interaction with gases and an ordered porosity, inverse opal structures have a great potential interest in gas sensing, though they have been poorly considered due to the technological problems encountered in the assembly of devices.In the present work we propose a novel and low cost approach to the synthesis of high quality oxide nanostructures with inverse opal architecture which, transferred on alumina substrates provided with Pt interdigitated contacts and heater, were tested as gas sensing devices. Beside SnO2, a binary oxide well studied for this purpose, Zn containing ternary solid solutions were taken into account for sensor preparation.Inverse opals were here prepared taking advantage of the sol-gel technique, starting from opal templates. The formation of an inverse opal can then be thought as deriving from a sol-gel process performed in a confined environment, so that the preparation of inverse opal structures can be in principle extended to all the oxides for which a preparative sol-gel route is applicable, including a variety of semiconducting metal oxide of interest as chemical sensors (SnO2, V2O5, WO3, TiO2 etc..).The prototype sensors were then tested for pollutant (CO, NO2) and interfering (methanol) gases in order to compare the results with those obtained for conventional tin dioxide sensors prepared with sputtering technique and to study the influence of the different Zn dopings on the sensing properties. Showing a high application potential, the prototype sensors exploited high sensitivity even at low temperature and the enhancement of the relative response towards NO2 at 200°C in comparison with conventional SnO2 sensors obtained with sputtering techniques. The addition of Zn, moreover, increased the separation between the operating temperatures for reducing and oxidizing gases and resulted in a further enhancement of the selectivity to NO2 detection. Interesting behaviours were evidenced and related to the different Zn contents.A new way has been opened towards the tailored synthesis of more sensitive, less energy consuming, miniaturized gas sensing devices.
10:45 AM - R7.7
High Temperature Phases Of Nanostructured Tungsten Oxide For Gas Sensing Applications.
Andrea Ponzoni 1 , Elisabetta Comini 1 , Matteo Ferroni 1 , Guido Faglia 1 , Giorgio Sberveglieri 1
1 Chemystry and Physics Dept., CNR-INFM SENSOR Lab. and Brescia University, BRESCIA Italy
Show AbstractTungsten oxide is a widely used material for gas sensing applications due to its sensitivity towards different gases such as NO2, H2S, O3. Several works have been addressed to synthesis of nanostructured WO3 layers, ascribing the performance increase to a grain size scaling down to the nanometer range. The wide range of gas-sensing performances exhibited by tungsten oxide highlight that performances can not be fully explained by grain size arguments, but a more detailed characterization is necessary. For example, depending on the deposition method and annealing treatment, devices either highly or scarcely sensitive towards NH3 have been obtained. Such differences may arise from the different crystalline phases of the material. Concerning titanium dioxide, for example, several studies highlighted strong differences between the sensing properties exhibited by the anatase and the rutile phases.WO3 crystallizes in several phases. Powders have been observed to undergo phase transitions during heating cycles and a correspondence between temperature range and phase has been addressed. When WO3 is deposited in form of film, the interaction with the substrate can cause some deviation from this temperature-phase relation. Despite the stable phase at room temperature has been indicated to be the triclinic one, thin and thick films have been observed to crystallize, for example, in the monoclinic and in the orthorhombic phases.In this work we used thermal evaporation method to synthesize nanostructured WO3 films. Materials have been prepared by evaporating a metallic tungsten wire in reactive atmosphere (oxygen pressure p=0.22 mbar). In particular, we have focused our attention on temperature effects, heating substrates at temperatures between 200 and 800°C. Microstructural analysis has been accomplished by electron microscopy (SEM and TEM) techniques and atomic force microscopy (AFM). Samples with microstructure suitable for gas sensing applications have been synthesized. The materials exhibit polycrystalline structure with single crystalline domains less than 50 nm large. Surface reveals a porous morphology characterized by agglomerates about 1μm large that gives samples a high surface area.Samples have been tested as conductometric gas sensors towards NO2, CO and NH3. Measurements have been carried out by flow through technique in a thermostatic sealed chamber where atmosphere composition was controlled by mass flow controllers and certified gas bottles.Results highlighted the capability of the prepared tungsten oxide films to reveal NO2 concentrations comparable with the outdoor threshold value (50 ppb). These good sensing performances were ascribed to the material microstructure.
11:30 AM - **R7.8
Unprecedented Ultra-High Hydrogen Gas Sensitivity in Undoped Titania Nanotubes.
Keat Ong 2 , Maggie Paulose 2 , Oomman Varghese 1 , Gopal Mor 1 , Craig Grimes 1
2 , SentechBiomed Corporation, State College, Pennsylvania, United States, 1 Electrical Engineering, Penn State University, University Park, Pennsylvania, United States
Show AbstractA highly-ordered array of micron-length un-doped titania nanotubes exhibit an unprecedented variation in electrical resistance of about 8.7 orders of magnitude (50,000,000,000%), at room temperature, when exposed to alternating atmospheres of nitrogen containing 1000 ppm hydrogen and air. This represents the largest known change in electrical properties of any material, to any gas, at any temperature. The nanotube arrays were fabricated using anodic oxidation of titanium foil in a pH 4.0 electrolyte containing potassium fluoride, sodium hydrogen sulfate monohydrate and sodium citrate tribasic dihydrate. The dramatic change in resistance is believed to be due to the highly active surface states on the nanoscale walls of the tubes, high surface area of the nanotube architecture, and the well-ordered geometry allowing for hydrogen-sensitive tube-to-tube electrical connections.Discussed is the effect of nanotube length, pore width, and wall thickness on hydrogen sensitivity. Integrated with a humidity sensor to compensate for fluctuations in humidity, we present a case study on application of the sensor platform to measurement of transcutaneous hydrogen levels for diagnosis of neonatal necrotizing enterocollitis.
12:00 PM - R7.9
Gas Sensors Based on Nano WO3 and nano- WO3:Cr Obtained from Different Hard Template Routes.
Anna Prim 1 , X Illa 1 , Albert Romano 1 , Juan Morante 1
1 Electronics, University of Barcelona, Barcelona Spain
Show Abstract12:15 PM - R7.10
Nanostructured (Sn,Ti, Nb)O2 Solid Solution for Hydrogen Sensing.
Maria Cristina Carotta 1 , Michele Benetti 1 , Vincenzo Guidi 1 , Sandro Gherardi 1 , Cesare Malagu' 1 , Beatrice Vendemiati 1 , Giuliano Martinelli 1
1 Physics, University of Ferrara, FERRARA Italy
Show Abstract12:30 PM - R7.11
Site-Specific Nanopattenrning of Functional Inorganic Nanostructures for Gas Sensing Applications.
Suresh Donthu 1 2 , Zixiao Pan 1 2 , Mohammed Aslam 1 2 , Arvind Srivastava 1 2 , Vinayak Dravid 1 2
1 Materials Science and Engineering, Northwestern University, evanston, Illinois, United States, 2 International Institute for Nanotechnology, Northwestern University, Evanston, Illinois, United States
Show AbstractRemarkable progress has been made in recent years in regards to synthesis and characterization of nanostructures with exquisite control over shape as in nanorods, nanobelts, nanotubes, among other monolithic single crystalline structures. However, structural inhomogeneities such as grain boundaries and porosity in such structures can further enhance their gas sensing performance. For example Xia’s group1,2 reported that tin oxide polycrystalline nanorods exhibit superior gas sensitivity than single crystalline nanorods at ambient conditions, highlighting the role of structural inhomogeneities in further improving the gas sensing performance. However, while chemical composition control of these structures is extensively reported, through doping for example, attempts to control the “internal microstructure” of these nanostructures remain relatively under explored. Obviously, it is very enticing to develop strategies to engineer the internal-structure such as grain size and porosity of nanostructures and measure their associated performance attributes. Elucidation of such structure-property correlations of nanostructures is necessary to evaluate the suitability of these structures as future high performance nanodevices. We have recently developed a nanopatterning technique termed as soft-electron beam lithography (soft-eBL)3 which utilizes combination of sol-based precursors and colloidal solutions for patterning nanostructures of metal oxides and composites. Given colloidal solutions with controlled particle sizes and doping levels, it is possible to control the structure of nanopatterns including grain size, composition and porosity. On the other hand, using sol based materials as precursors for patterning and invoking the effects of substrate and heat-treatment profiles, it is equally amenable to control the texture and grain size of the nanopatterns. For example ZnO nanopatterns were fabricated using soft-eBL on variety of substrates including GaN and Sapphire which have structural compatibility with ZnO. Our preliminary results show that ZnO nanopatterns fabricated using soft-eBL technique show UV sensing performance at least comparable to monolithic ZnO nanorods of similar dimensions3 at room temperature. In addition we also observe that ZnO nanopatterns show high sensitivity to ethanol at room temperature when measured under exposure to UV light. These results indicate that by engineering the internal structure of nanopatterns, one can especially enhance gas sensing performance and gain unambiguous insight into structure-property relations of these structures. The presentation will cover the sol-gel precursor and colloidal assembly strategy for nanopatterning of functional inorganics using soft-eBL. We will also demonstrate the efficacy of this novel nanopatterning approach to engineer the “internal microstructure” of nanopatterns, and highlight the structure-property attributes in gas sensing considerations.
12:45 PM - R7.12
Nanoparticle Metal-Oxide Films on Microhotplate Platforms: Fabrication and Gas-Sensitive Properties.
Alexey Tomchenko 1 , Brent Marqius 1
1 , Sensor Research and Development Corp., Orono, Maine, United States
Show Abstract