Pu-Xian Gao, University of Connecticut
Joseph V. Mantese, United Technologies Research Center
Paul Ohodnicki, National Energy Technology Laboratory
Lin Shao, Texas Aamp;M University
GG2: MEMS and Micromachined Sensors
Monday PM, December 01, 2014
Hynes, Level 2, Room 209
2:30 AM - *GG2.01
Degradation of Ferroelectric Thin Film Pb(Zr,Ti)O3 in H2SO4
Leo J Small 1 Chris Apblett 1 Geoff Brennecka 1 Jon F Ihlefeld 1 David J Duquette 2
1Sandia National Laboratories Albuqerque USA2Rensselaer Polytechnic Institute Troy USAShow Abstract
Remote sensing applications in harsh environments require sensor materials appropriately matched to the environment. PbZr0.52Ti0.48O3 (PZT) is a candidate for remote sensing applications, where it could be used as both a sensor and power source. In this light, the evolution of the PZT-H2SO4 interface is explored at low pHs. A robotic microdroplet cell is developed to differentiate the electrochemical response of the cracks and pores inherent to the PZT film from that of continuous PZT. Accelerated chemical attack is observed at the pores, while the continuous PZT displays electrochemical hysteresis; the ferroelectric-solution interface can be switched between two different charge states at a given potential. As time progresses, electrochemical impedance spectroscopy reveals a change in the structure of the PZT-H2SO4 interface. Development of equivalent circuits to model the competing processes of pore growth, interfacial layer formation, and uniform chemical attack are guided by the evolution of film structure and chemistry as observed ex-situ with scanning electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction. The Point Defect Model for the passive state is used to explain the dissolution processes observed in the complex oxide. Application of this model to PbZrxTi1minus;xO3 for x = 0.25, 0.52, and 0.95 points to the role of titanium in the creation of an ionically insulating layer that impedes further chemical attack.
3:00 AM - *GG2.02
An Overview of the Development of High Temperature Wireless Smart Sensor Technology
Gary Hunter 1
1NASA Glenn Research Center Cleveland USAShow Abstract
Smart Sensor Systems that can operate at high temperatures are required for a range of aerospace applications . For example, for future aerospace propulsion systems to meet the requirements of decreased maintenance, improved performance, and increased safety; the inclusion of intelligence into the propulsion system design and operation is necessary. These systems must incorporate technology to monitor component conditions, analyze the incoming data, and modify operating parameters to optimize system operations. Overall, the goal is to make intelligent vehicle systems by developing Smart Sensor Systems operational in harsh environments.
A Smart Sensing System as described here implies the use of sensors combined with electronic processing capability. The definition of a Smart Sensor may vary, but typically at a minimum a Smart Sensor is the combination of a sensing element with processing capabilities provided by a microprocessor . A more expansive view of a Smart Sensor System is a complete self-contained sensor system that includes the capabilities for data storage, processing with a model of sensor response and other data, self-contained power, and an ability to transmit or display informative data to an outside user.
The harsh environment inherent in propulsion systems is especially challenging for Smart Sensor Systems; this paper addresses technology development for such applications. A basic sensing system for high temperature wireless pressure monitoring composed of a sensor, electronics, and wireless communication with scavenged power developed for health monitoring of aircraft engines and other high temperature applications has been demonstrated at 4750C . Other efforts will be discussed including a brief overview of the status of high temperature electronics and sensors, as well as their use and applications.
1. G. W. Hunter and A. Behbahani, “A Brief Review of the Need for Robust Smart Wireless Sensor Systems for Future Propulsion Systems, Distributed Engine Controls, and Propulsion Health Management”, 58th International Instrumentation Symposium, San Diego, CA, June 4-78, 2012
2. G. W. Hunter, J. R. Stetter, P. J. Hesketh, and C.C. Liu 2011. “Smart Sensor Systems”, Interface Magazine, Electrochemical Society Inc., Vol. 20, no. 1, Winter, 66-69
3. G. W. Hunter, et. al, “High Temperature Wireless Smart Sensor Technology Based on Silicon Carbide Electronics”, ECS Trans. 2014 61(4): 127-138; doi:10.1149/06104.0127ecst
3:30 AM - GG2.03
Silicon Integrated Oxygen Lambda Sensor Based on Micromachined Platforms and Ytria Stabilized Zirconia Thin Membranes
Alex Morata 2 Inigo Garbayo 2 Dolors Pla 2 Marc Salleras 1 Neus Sabate 1 Albert Tarancon 2 Joan Ramon Morante 2
1Institut de Microelectramp;#242;nica de Barcelona, CSIC Bellatera Spain2Catalonia Institute for Energy Research Sant Adria SpainShow Abstract
Lambda sensor is a solid-state electrochemical cell that provides a potential proportional to the logarithm of the oxygen concentrations at its electrodes. After Robert Bosch GmbH first introduced this sensor in the sixties, it has been extensively used for the measure of exhaust gas concentration of oxygen on internal combustion engines. An important improvement was achieved in the nineties by means of a reduction of mass and the incorporation of buried heaters. It resulted on a much rapidly starting sensor with a faster response.
The current work continues with this miniaturization approach with the aim to further expanding the availability of gas sensors to new market niches. For example, less consuming cheaper sensors could open the way to exhaustive atmosphere monitoring, by means of nets of portable wireless gas sensors (ubiquitous sensor networks). The presented fabrication route combines industrial clean room batch production processes with the use of nanometric thin films of Ytria Stabilized Zirconia (YSZ) as solid electrolyte. A drastic reduction of the power consumption is pursued by means of two convergent effects. On the one hand, the volume of the active part of the sensor allows a rapid heating with minimum power. On the other hand, the thin electrolyte provides a lower resistance, making possible to reduce the operating temperature and increase the response velocity.
A cross plane membrane potentiometric micro gas sensor has been fabricated and tested. The device is based on a thin electrolyte membrane deposited by large area pulsed laser deposition (LAPLD) on a micromachined silicon platform. 300 nm YSZ film is deposited as solid electrolyte on a sacrificial Si3N4 layer. A doped-silicon hexagonal supporting grid provides with the mechanical resistance to large area membranes of several square millimeters. Finally, thin porous Pt electrodes are sputtered at both sides of the electrolytic membrane.
Less than one second heating rates without damage have been observed. Oxygen partial pressure at different atmosphere has been neasured at 500 0C, showing a fast and stable response. The presented results prove the viability of potentiometric micro sensors in a nano-membrane architecture, opening the way for the fabrication of reliable, low cost, low consumption and rapid gas sensors.
3:45 AM - GG2.04
Theoretical Study and Performance Optimization of Grating-Structured Triboelectric Nanogenerators as Self-Powered Nanometer-Resolution Motion Sensors
Simiao Niu 1 Yu Sheng Zhou 1 Sihong Wang 1 Ying Liu 1 Zhong Lin Wang 1
1Georgia Institute of Technology Atlanta USAShow Abstract
Triboelectric nanogenerator (TENG) technology is an emerging new mechanical energy harvesting technology with numerous advantages. Amongst the multitude of TENG designs, the grating structure is not only the most promising for ultra-high output power but also the most complicated. In this work, the #64257;rst theoretical model of the grating structured TENG is presented with in-depth interpretation and analysis of its working principle. There are generally two different categories of grating TENGs with different output characteristics: grating TENGs with equal and unequal plate length. For each of these two categories, besides the study of the basic output profile, we performed an in-depth discussion on the influence of electrode structures, number of grating units, and thickness of the dielectric layers for the unequal plate structure in this work. As for the electrode structure, grating electrodes always lead to a better performance than plate electrodes for both of these categories. As for the most important parameters of grating TENGs—the number of grating units, our theoretical calculation clearly indicates that increasing the number of grating units to get a finer pitch will generally improve the output performance. However, when the pitch is very fine, the edge effect begins to dominate, resulting in degradation of performance when the number of units continues to increase. Thus, there exists an optimum number of grating units, and an optimum unit aspect ratio that mainly depends on the materials dielectric constant and the motion type. These are important parameters to consider for future structural design. As for the dielectric thickness in the unequal length design, the thickness of the dielectric of the longer plate should be much smaller than that of the shorter plate.
With the above theoretical understanding of the grating structured TENGs, we utilize their unique characteristics to work as self-powered motion sensors. One dimensional displacement and speed can be detected using peak/zero-crossing counting method, which is very robust against variations caused by non-uniform surface charge distribution, surface contamination or grating defects. Analysis of the OC voltage amplitude improved the displacement resolution to be 173 nm for a grating width of 100 mu;m. The real time speed can be detected by the SC current amplitude, which shows a very good linear correlation with a large dynamic speed range from 5 mu;msminus;1 to 0.1 msminus;1. This design opens a new paradigm for displacement/speed sensing by distinguishing itself from the existing technologies through a combination of self-powered, nano-resolution at a long working distance, high robustness and tolerance, non-optical simple structure as well as low cost. [1,2]
1. Energy & Environmental Science 2014, DOI: 10.1039/C4EE00498A.
2. Advanced Materials 2014, 26, 1719-1724.
4:30 AM - GG2.05
Multiples Individual Nanowire Integrated in SOI-CMOS Based Hot-Plates for High Temperature Ambient Gas Sensors
Cristian Fabrega 1 Francisco Hernandez-Ramirez 1 Joan Daniel Prades 2 Feng Shao 1 Joan Ramon Morante 1 2
1IREC Sant Adria de Besos Spain2UB Barcelona SpainShow Abstract
Individual metal oxide nanowires have been recognized as powerful gas sensor platforms with much better advantages than many of the widespread reported metal oxide based solid state resistive gas sensors. Individual MOx nanowire allows self-heating operation procedure saving up the heaters integration as part of the hot plate. Likewise, they show shorter response and recovery time solely limited by the thermal inertia of the hotplate and the chemical reaction taking place onto the sensing material surface as there is not any gas diffusion time. Moreover, they have also a total capability for being fully activated by UV illumination as all the volume of the nanowire is included in the absorption zone. It enhances the sensor response avoiding the use of heating excitation. And complementarily, their low thermal inertia allow to apply pulsed operational mode with the consequent advantage for controlling, cleaning and determining the starting point of the surface conditions.
Nevertheless, in spite of these improvements, individual nanowires, up to now, have not yet used for fabricate real sensors as there is not available suitable and feasible nanotechnologies allowing the nanomanipulation of these individual nanowires. Alternatively, serious efforts have been performed for growing them directly on micro hotplate obtaining something like a “mat” of nanowires and very different of the performance of individual nanowire acting as a quasi-perfect nanocrystal with the above described characteristics.
In this contribution, a methodology for allocate a distribution of individual nanowires between the designed interdigitated electrodes of a SOI-CMOS microhotplate is presented. It is based on a dielectrophoresis process on the previously deposited solution containing the nanowires. Electrical contacts are improved by in-situ thermal treatment using the self-heater of the hotplate. In this way, combining SOI-CMOS micro hot plate and multiples individual nanowires as sensing material distributed between the interdigitated electrodes, a high performant configuration suitable for harsh environments sensing of gases is obtained on the base of the robustness of both sensing material and microhotplate. Sensor prototypes and their characteristics will be presented taking ZnO nanowires as an example
4:45 AM - GG2.06
Titanium Nitride Thin Films Deposited by Reactive Magnetron Sputtering for Strain Gauge Applications
Nis Dam Madsen 1 Mathias Hausladen 1 Kasper Thilsing-Hansen 1 Serguei Chiriaev 1 Jakob Kjelstrup-Hansen 1
1University of Southern Denmark Sonderborg DenmarkShow Abstract
There is a demand for thin film strain gauge materials which are capable of operating at elevated temperatures. This work investigates the performance of TiNx thin films deposited using reactive magnetron sputtering for use as a strain gauge material. The depositions were made from a titanium target in a N2/ Ar atmosphere without intentional heating of the substrates. Films of different composition were prepared by varying the nitrogen flow from the metallic- to the poisoned mode of reactive sputtering. The deposition pressure was kept constant by adjusting the argon flow. The atomic composition of the films was estimated using energy-dispersive X-ray spectroscopy (EDX) showing an increasing content of nitrogen with increasing nitrogen flow. No oxygen was detected in the films made in the metallic target mode while up to 10% oxygen was detected in the remaining films. The structure of the films was studied using X-ray diffraction (XRD). The XRD diffractogram of the film deposited at the lowest nitrogen flow only contained the (00.2) peak from hcp titanium. As the nitrogen flow was increased, peaks from the cubic-TiN phase were observed in the diffractograms. At intermediate flows, a (111) texture of the cubic-TiN grains was observed, while the films deposited in the poisoned mode of sputtering (high nitrogen flows) developed a (200) texture. The intrinsic stress of the films was measured using the wafer curvature method based on the Stoney equation. Films deposited in the metallic mode were in tensile stress while the films made in the poisoned mode were compressively stressed. The film resistivity was measured on films deposited on polished BK7 glass substrates using a 4-point probe. The resistivity was in the range of 0.2-0.5 m#8486;#8729;cm and was found to increase with the nitrogen flow. The stability of the resistivity was also studied at 200°C for 300 hours revealing stable behavior of films deposited in the metallic and poisoned of sputtering, however, films deposited with intermediate nitrogen flows were instable. The piezoresistive gauge factor was measured on films structured into meander-type resistors and deposited onto a thermally grown SiO2 layer on a Si (100) wafer. The samples were strained in a 3-point bending setup in which the temperature could be controlled (TA Instruments Q800). The current-voltage (I-V) response was measured as function of load and temperature while the resistance was extracted from the slope of the I-V curves. The strain was calculated using Euler-Bernoulli beam theory. The gauge factors of the films were found to increase with increasing nitrogen flow while the temperature coefficients of resistivity changed from positive to negative.
5:00 AM - GG2.07
Amorphous WNx Metal For Accelerometers and Gyroscope
Abdulilah Mayet 1 Muhammad Mustafa Hussain 1 Mohamed Ghoneim 1
1King Abdullah University of Science and Technology Thuwal Saudi ArabiaShow Abstract
Nanoelectromecahnical systems (NEMS) are getting more attention for their higher resonant frequency #402;o and lower threshold voltage, thanks to their nano-scale size. However issues such as stiction, line edge roughness, nano fabrication difficulties and material fractures and fatigue limit out the material selection for NEMS device fabrication. In this work, a novel material (amorphous tungsten nitride a-WNx) has been demonstrated to overcome most of these issues. Amorphous WNx has high Young&’s modulus (E = 300 GPa) which makes the spring constant ks higher. This allows the fabricated devices to overcome the stiction issue in NEMS. This together with the high conductivity (R = 0.2 mOmega;.cm) yields high resonance frequency. Slightly tensile stress ( σ = —500 MPa) makes the released free standing parts remain straight neither curving downward nor curling upward. WNx NEMS fabricated devices has longer lifetime due to its hard surface, thanks to the high hardness (H = 3 GPa). Economic side of WNx is as attractive as the technical side. NEMS WNx is deposited by simple commercial PVD sputtering tool with commercial tungsten target and N2 gas flow. All the fabrication process steps are CMOS compatible, no need for special tools, neither special condition. Laterally moving cantilever device could be fabricated using a single mask, or three masks for vertically moving device, unlike 8 masks for PolyMUMPs devices. This could save more than 60% of the fabrication cost. Finally, the fabricated devices have high Q because of the high resonant frequency and small damping factor as well as high sensitivity. The high density (ρ = 19 g.cm-3) makes it the best candidate for accelerometer and gyroscope mass proof. The existing accelerometers and gyroscope either fabricated with piezoelectric film or with thermal bubbles. These devices have very low response in time. Another version of accelerometers and gyroscopes is operating as variable capacitors. This type of devices is fabricated with PolyMUMPs process, which makes it very complicated and expensive. On the other hand, their response time is very fast. Using WNx to fabricate accelerometers and gyroscope, gives the advantage of single mask easy process and fast response time. The high density of WNx leads to higher sensitivity device. Higher elasticity modulus leads to stiffer spring and longer lifetime in term of stiction, the most killing factor for NEMS and MEMS. The high conductivity leads to faster response in charging and discharging the sensing capacitance, which lead to a better operation than the existing classical devices. The amorphous metal WNx gives the advantage of fractureless springs and material, even distribution of the internal stress in the spring, higher elasticity than Si and wider temperature range for operation. All these characteristics give the amorphous WNx advantage to be the one of the best candidates for accelerometers and gyroscope fabrication.
5:15 AM - GG2.08
SiC-Based MIS Gas Sensor for High Temperature High Water Vapor Environments
Olga Casals 1 Thomas Becker 2 Albert Romano-Rodriguez 1
1Universitat de Barcelona (UB) Barcelona Spain2EADS Bremen GermanyShow Abstract
In the last years there is an intense research for the development of hydrogen or hydrocarbon-based fuel cells because of the feasibility to generate electrical energy from the reaction of these gases with oxygen. As a result, the exhaust gases of the cell have a high concentration of water vapor and CO2. However, due to an improper operation of the devices, the exhausts could contain rests of the fuel or byproducts of the catalytic reaction. For this reason, gas sensors are required to monitor the proper operation of the fuel cell.
In this work we will show the use of Pt/TaOx/SiO2/SiC Metal Insulator Semiconductor (MIS) capacitors to detect hydrogen, CO and saturated and unsaturated hydrocarbons in atmospheres with extremely high concentrations of water vapor (up to 40% by volume ratio of water vapor to nitrogen) and temperatures between 200 and 400#730;C. The TaOx layer is nominally 20nm thick, while the porous Pt contact has a thickness of about 40nm. The sensors gas response has been measured as the gate voltage change (#8710;V=VG(gas)-VG(N2)) under constant capacitance conditions and referred to the value when in N2 gas.
The obtained results indicate that, in absence of other gases involved in the fuel cell, the capacitors are almost insensitive to the presence of water vapor, while the addition of hydrogen to the water vapor gives rise to a diminution of the response to hydrogen with increasing water vapor concentration, saturating above 30%.
In this work we will report the response of the MIS capacitor to the different gases and mixtures of interest for this application and we will correlate the results with the most recent approaches to heterocatalysis on Pt surfaces in order to propose suitable sensing mechanisms.
5:30 AM - GG2.09
Effect of Growth Stress in High-K Dielectric Thin Films
Narayan K. V. L. V. Achari 2 1 Hareesh Chandrasekar 1 Amiya Banerjee 1 K. B. R. Varma 2 Navakanta Bhat 1 Srinivasan Raghavan 1
1Indian Institute of Science Bangalore India2Indian Institute of Science Bangalore IndiaShow Abstract
The scaling of silicon-based CMOS technology has hit a limit both in terms of the thickness of SiO2 based dielectric schemes, which are now limited by quantum tunneling, and secondly with respect to carrier injection from the drain into the Si channel. The first problem has been overcome by the use of high-k dielectrics, like zirconia and hafnia among many others. The issue of carrier injection necessitates the use of materials with high electron and hole mobilities, the most promising amongst them being Germanium having electron and hole mobilities of 3000 and 900 cm2/Vs respectively. Zirconia is known to form a stable interface with germanium unlike hafnia and hence can be used as high-k dielectric on Ge as a potential combination to replace conventional SiO2/Si for CMOS applications.
For the first time, in this interesting study we correlate growth stress in the ZrO2 films to their crystallinity and dielectric permittivity. Our results showed that compressive growth stress alone can change the ZrO2 films relative permitivity from 5 to 23. And effect of further increase in stress was also studied.
We reported electrical and structural characterization of ZrO2 /n-Ge  by reactive-direct current sputtering. As zirconia has phase dependent anisotropic dielectric permitivity. For the first time a clear selection of phase in thin film was achieved by precise control of growth temperature, stress and film thickness. Amorphous, tetragonal and monoclinic phases of zirconia were studied.
The best EOT of 8 Å at 5 nm oxide thickness was achieved in sputter deposited zirconia. A novel stack was proposed to reduce leakage current density in MOS capacitor structures, which showed promising leakage current reduction by an order of magnitude.
GG3: Poster Session I: Nanomaterials for Harsh Environment Sensors I
Monday PM, December 01, 2014
Hynes, Level 1, Hall B
9:00 AM - GG3.01
Printable Nanomaterials for Flexible Chemical Sensors and Electronics
Wei Zhao 2 Tom Rovere 2 Darshana L Weerawarne 1 Pharrah Joseph 2 Gavin B Osterhoudt 1 Jin Luo 2 Susan Lu 3 Bonggu Shim 1 Chuan-Jian Zhong 2
1State University of New York at Binghamton, Binghamton Binghamton USA2Binghamton University Binghamton USA3Binghamton University Binghamton USAShow Abstract
The ability for sensor or electronics devices to adapt or withstand complex environment is important for enabling their practical applications. Flexible sensors and electronics produced by roll-to-roll manufacturing process represent advanced approaches to the versatility of applications in terms of sensing environment and device durability. This report describes recent results of an investigation of nanomaterials that can be printed and processed on flexible substrates such as polyethylene terephthalate and polyimide. Size and composition controlled metal or alloy nanoparticles have been synthesized by wet chemical processes. The demonstration of the controllable printing and sintering of the nanoparticle inks on the flexible substrates by thermal and laser sintering techniques provide promising leads to establishing printable nanomaterials for flexible sensors and electronics. The morphological, structural, and electrical properties of the flexible devices are characterized using different techniques in correlation the detailed laser-sintering parameters with both pulsed and continuous-wave lasers. Results on the device strain-performance characteristics will also be discussed in correlation with the device durability and application.
9:00 AM - GG3.03
Chemical Synthesis and Characterization of Manganese Oxide Coated Ni Particles
Jun He 1
1Central Iron and Steel Research Institute Beijing ChinaShow Abstract
Nanostructural magnetic materials have the potential to revolutionize current data storage technologies, magnetoelectronics, and biotechnology. The surface and size effects have been one of the main topics among scientists. The ferromagnetic(FM)/antiferromagnetic(AFM) core/shell systems are gaining increasing attention due to their appealing novel properties and promising application. Many valuable phenomena, such as giant magnetoresistance and interfacial exchange bias effect, have been found. In this work, the manganese oxide coated Ni particles were prepared in a two-step process. The first step is the manufacture of Ni nanoparticles. The second step is the coating process, which is to cover the above precipitates manganese oxide. Detailed synthesis process is omitted here. Nanostructural characteristics are obtained by XRD and TEM observation. The TEM image of manganese oxide coated Ni particles clearly exhibits the core/shell structure with the core size of about 15~20 nm coated by 9 nm thick shell. No Ni-oxide phase is found, indicating the dependability of the processing method. Magnetization curves for the manganese oxide coated Ni particless were performed with maximum magnetic field 50 kOe at different temperatures after the zero field cooling(ZFC). The hysteresis loop below 5 kOe and the unsaturation of magnetization at higher field reflect the cooperative contribution of ferromagnetic and superparamagnetic characteristics in the sample. For T=300 K, the typical non-hysteretic superparamagnetic behavior is obtained, which is related to the small size effect of Ni nanoparticles. Basically, these curves can be fitted by the contribution of two kinds of magnetizations: M(H)=Msp(H)+chi;H, where Msp is a superparamagnetic one that follows a Langevin-like function, and chi;H is the linear component. The comparison between the ZFC and Field cooling(FC) hysteresis loops were also measured at 5 K for the Ni/MnO particles. It can be seen that the ZFC and FC loops are completely overlapped for both samples. There exists no exchange bias behavior, probably because of the weak ferromagnetic characteristic of Ni cores and poor interfacial coupling effect between FM core and AFM shell, even though the distinct core/shell structure has been exhibited. The magnetization measurements show that the total magnetization of each particle is the result of cooperation of the core and shell magnetic moments. Even though the interaction between them is too weak to cause exchange bias effect, but the typical two step magnetization behaviors have been presented in the annealed Ni/MnO particles. Through the analysis of M-T curves, we find out that the synthesized MnO-coated Ni particles , with the perfect nanostructure, are without any magnetic impurity phases.
9:00 AM - GG3.04
Electrospun P3HT/PMMA Blend Fibers for High Efficient, Real-Time and Low Cost Volatile Organic Compounds Sensors
Ming-Chung Wu 1 Ting-Han Lin 1 Shun-Hsiang Chan 1 Wei-Fang Su 2
1Chang Gung University Tao-Yuan Taiwan2National Taiwan University Taipei City TaiwanShow Abstract
Volatile organic compounds (VOCs) sensors are the imperative technology of modern life for environmental monitoring. There are no ending quests for low cost, high sensitivity, high reproducibility and high selectivity sensors. In this study, we demonstrated a VOCs sensor chip adopting the proposed methodology that the optical property of poly(3-hexylthiophene) (P3HT)/poly(methyl methacrylate)(PMMA) blend is sensitive to VOC vapor due to morphological evolution and hence can be served as an indication of the presence of VOCs. The P3HT/PMMA served as a representative blend, and the sensitivity of the P3HT/PMMA blend was optimized with respect to P3HT molecular weight, P3HT/PMMA blending ratio, and blend concentration. The present work utilizes P3HT/PMMA blend to sense various VOCs by detecting the variation of optical properties. In order to increase the specific surface area, the electrospinning technique was used to fabricate P3HT/PMMA VOCs sensing chips and it exhibit high optical absorbance and high sensitivity. A series of VOCs, such as toluene, chlorobenzene, ethanol, acetone, etc., were chosen to test the applicability of the sensor, and the results reveal high performance without disruption by water vapor. The measurements of the detection limit show that the concentration over explosive limits can be detected by the sensor within several minutes. The low cost, high sensitivity, high sensing accuracy, quick response, and real-time P3HT/PMMA VOC sensor chip developed in the present work signi#64257;cantly extends the current VOC sensing technology and can be extensively used to e#64256;ectively prevent humans and the environment from potential damages of VOCs.
9:00 AM - GG3.05
Energy Harvesting of PZT Nanoparticles Interconnected with Multi-Walled Carbon Nanotubes
Jin Kyu Han 1 Do Hyun Jeon 1 Jin Ho Kwak 1 Ki Young Choi 2 Eun Ju Ra 3 Jong Sun Lim 3 Sang Don Bu 1
1Chonbuk National University Jeon Ju Korea (the Republic of)2Seoul National University Seoul Korea (the Republic of)3Korea Research Institute of Chemical Technology Daejeon Korea (the Republic of)Show Abstract
Nanogenerators that harvest energy from mechanical vibration are an attractive area of nanotechnology fields. Recently, composite-type nanogenerator consisting of piezoelectric nanostructures and multi-walled carbon nanotubes (MWCNTs) is one of the excellent candidates for the future energy harvesting because they can apply the great electrical and mechanical properties of MWCNTs. Researches on the composite-type nanogenerators are focused on obtaining highest output power and understanding the role of the MWCNTs in the nanogenerators. However, the role of the MWCNTs is not fully understood because previous reports are based on the simply mixed MWCNTs and piezoelectric nanostructures in the polymer matrix. The interconnected growth of piezoelectrics onto MWCNTs provides not only key information to understand a systematic role of MWCNTs in nanogenerator property but also effective transfers of stress occurred in the MWCNT and piezopotential created in the piezoelectrics.
We report a successful growth of Pb(Zrx,Ti1-x)O3 (PZT) nanoparticles (NPs) interconnected with MWCNTs (PZT NPs-CNT) through injection method of sol-gel solution into a filter for squeezing them and annealing for crystallizing them. The injection method helps to minimize the remaining sol-gel solution after coating onto MWCNTs. High resolution transmission electron microscope analysis of PZT NPs-CNT reveals that the PZT NPs have a diameter of 20minus;30 nm and are polycrystalline with a tetragonal structure which atomically connected with the MWCNTs. Energy dispersive x-ray spectroscope of PZT NPs-CNT confirms the presence of lead, zirconium, titanium and carbon. In order to form the flexible thin film, the PZT NPs-CNT was mixed with poly-tetrafluroethylene of 5minus;30 % as binder and milled until 150 mu;m in thickness. The thin films were then attached to the Au/Cr coated polyimide film. By periodic banding movements, the open-circuit voltage and short-circuit current of the PZT NPs-CNT reaches about 0.2 V and 10 nA, respectively. In order to analyze the role of the MWCNTs in the nanogenerator, we controlled the ratio of the CNT and PZT NPs from 0.1 to 0.8, which can vary the internal resistance and conductance. We will discuss the role of the MWCNTs by measuring the output powers of weight-ratio-controlled PZT NPs-CNT.
9:00 AM - GG3.06
Effects of Temperature on Organothinol Self-Assembled Monolayers Coating of Copper Surface
Soorathep Kheawhom 1 Pacharaporn Kongsumrit 1
1Chulalongkorn University Bangkok ThailandShow Abstract
Copper is a promising material that can be used as conductive layer in printed electronics due to its high electrical conductivity and low cost compared to other metals. However, copper patterns printed are prone to oxidation and corrosion, and copper oxides degrade the electrical properties of the copper patterns. Coating the copper patterns by organothiol self-assembled monolayers (SAMs) is one of effective methods for oxidation and corrosion protection. However, the SAMs coating layer may not withstand high temperature. Although, thermal stability is also an important feature because it can limit their practical applications, only a few works have studied the effects of the temperature on the SAMs coating layer. In this work, we studied the thermal stability of organothiol SAMs coating on the copper surface. Moreover, mechanisms of SAMs decomposition were also investigated. The organothiol SAMs were coated on copper sheets prepared by electro-polishing followed by oxygen plasma treatment. Three types of organothiol molecules including 1-octanethiol (OTT), 2-ethylhexanethiol (2-EHT) and 2-phenylethanethiol (2-PET) were investigated. These chemicals are similar in terms of the number of carbon atoms but different in chemical structure. Contact angle, SEM, AFM, and potentiodynamic polarization are used to analyze hydrophilic and hydrophobic features, morphology, roughness, and corrosion inhibition efficiency, respectively. Mechanisms of SAMs decomposition were studied by FT-IR and XPS analyses. The copper surfaces coated by each organothiol SAMs were annealed at temperature ranging from 25 to 250°C. It was found that OTT SAMs were decomposed at 80°C while 2-EHT SAMs were decomposed at 140°C. In contrast, decomposition of 2-PET SAMs were occurred between 140°C and 250°C, because 2-PET molecule consists of aromatic rings that are more stable than other functional groups in OTT and 2-EHT structures. It is apparent that in all cases, decomposition of organic chain groups were occurred and followed by decomposition of thiolate bond.
9:00 AM - GG3.07
Copper Surfaces Protection by Organothiol Self-Assembled Monolayers
Soorathep Kheawhom 1 Supattra Haokratoke 1
1Chulalongkorn University Bangkok ThailandShow Abstract
Using copper as conductive material in printed electronics has gained considerable attention in recent years due to its high electrical conductivity and low cost compared to other metals. However, copper patterns printed are prone to oxidation and corrosion especially in environment containing chloride ion, and it affects the electrical properties of the copper patterns. Organothiol self-assembled monolayers (SAMs) coating is one of effective methods to protect the copper patterns from corrosion and oxidation. The condition used during SAMs formation affects quality of the organothiol-SAMs coating layer and hence corrosion protection efficiency. However, only a few works have studied the effects of the condition used during SAMs formation on the properties of the SAMs coating layer obtained. The aim of this work was to study the effects of concentration of organothiol molecules and temperature used during SAMs formation on wettability, packing density, roughness and corrosion inhibition efficiency of the SAMs coating layer. The organothiol-SAMs were coated on copper sheets prepared by electro-polishing followed by oxygen plasma treatment for 15 s. Three types of organothiol molecules including 1-octanethiol (OTT), 2-ethylhexanethiol (2-EHT) and 2-phenylethanethiol (2-PET) were investigated. These chemicals are similar in terms of the number of carbon atoms but different in chemical structure. Temperature ranging from -15 to 50 °C, and concentration of organothiol molecules ranging from 0.005 to 0.02 M in isopropanol alcohol (IPA) were studied. Contact angle analysis, SEM/EDX, AFM and potentiodynamic polarization are used to analyze the properties of the SAMs coating layer obtained. It was found that the condition used during SAMs formation strongly affects the quality of the SAMs coating layer. Organothiol molecules of 0.01 M provided the SAMs coating layer with highest corrosion inhibition efficiency. Higher concentration used yielded the SAMs with higher porosity or lower packing density. In contrary, with lower concentration used, the organothiol molecules could not fully cover the copper surface. The SAMs formed at 40 °C with OTT and 2-EHT, and at 0 °C with 2-PET were the most favorable condition with the water contact angle of 124.79°, 130.66° and 120.58°, respectively, and the corrosion inhibition efficiency of 96.24%, 99.37% and 98.90%, respectively.
9:00 AM - GG3.08
Solid-Phase Colorimetric Sensor Strips Based on Gold Probe-Loaded Nanofibrous Membranes for Lead Ions Assaying
Yan Li 1 Gang Sun 1 Bin Ding 1
1Donghua University Shanghai ChinaShow Abstract
Although the Au nanoparticle (Au NPs)-based chromatic lead ions detection allows straightforward observation often with high sensitivity and specificity, solution-phase chromatic sensors in general still have several limitations which practically deter its widespread use. Driven by actual need, we have developed a fast, sensitive and portable sensor strip for naked-eye chromatic assaying of Pb2+ utilizing electrospun Nylon-6/Polyvinylidene fluoride (N6/PVDF) nano-fibers/nets (NFN) membranes assemble L-glutathione conjugated Au NPs probes (Au@GSH). A basic principle here is that the Au@GSH on the N6/PVDF NFN membranes can aggregate to trigger the red shift from 550 nm to 600nm and a color change of pink to purple on the strip upon incubation with Pb2+. Benefiting from large specific surface areas, high porosity and Steiner Tree networks structure of the NFN membranes, the strips exhibited excellent stability, rapid response (10 min), wide detection range (10 to 100 mu;g/dl) and low naked-eye detection limit of 10 mu;g/dl at room temperature. Additionally, the sensing responses are visualized quantitatively by employing a chromatic framework that translates measured spectra into numeric color values which is directly related to color perception. Furthermore, the NFN-based strip displayed excellent anti-interference ability to other 10 possible interfering metal cations and 28-fold higher sensitivity than paper-based one upon exposure to a synthetic mixture. The result clearly demonstrated that this is promising sensing system which could act as a first step toward remediation of lead poisoning in future.
9:00 AM - GG3.09
Electrical Properties of Layer-by-Layer PANI/ZnO Nanocomposites Films
Rafaela da Silveira Andre 1 Bruno Cano Mascarenhas 1 Elaine Cristina Paris 2 Daniel Souza Correa 2 Luiz Henrique Capparelli Mattoso 2
1Embrapa Instrumentaamp;#231;amp;#227;o Samp;#227;o Carlos Brazil2Embrapa Instrumentaamp;#231;amp;#227;o Samp;#227;o Carlos BrazilShow Abstract
Nanocomposites based on inorganic nanoparticles incorporated in polymer matrixhave received much attention recently due to their electrical and optical properties and the wide range of potential applications . Among inorganic nanoparticles, zinc oxide (ZnO) present appealing features such as electrical and optical properties, it is biocompatible and can be prepared by simple chemical routes . As polymer matrix, polyaniline (PANI) is a widely studied conducting polymer due to good environmental stability and tunable conductivity . In the present work, we obtained nanocomposite films based on PANI/ZnO, which were obtained by the Layer-by-Layer (LBL) method aiming at applications in chemical sensors. PANI was purchased from Sigma Aldrich and ZnO particles were synthesized by the hydrothermal method at 150°C during 30 minutes. The films with 3, 5 and 7 bilayers of PANI/ZnO were deposited onto interdigitated platinum electrodes. The samples were characterized by UV-vis spectroscopy, scanning electron microscopy and electrical measurements, in air with different concentrations of ammonia. UV-vis spectroscopy and scanning electron microscopy confirmed the homogeneous adsorption of bilayers of PANI/ZnO onto the substrates. The electrical measurements yielded satisfactory differentiation for distinct concentrations of ammonia, indicating the potential application of nanocomposites based on PANI / ZnO as gas sensors.
Acknowledgments: This work was supported by CNPq, CAPES, FAPESP and Embrapa.
1. Dhingra, M., et al., Polyaniline mediated enhancement in band gap emission of Zinc Oxide. Composites: Part B, v. 45 p. 1515-1520, 2013.
2. HUANG, R.H., et al., Improvement of proton exchange membrane fuel cells performance by coating hygroscopic zinc oxide on the anodic catalyst layer. Journal of Power Sources, v. 227, p. 229-236, 2013.
3. Ahmed, F., el al., Preparation and characterizations of polyaniline (PANI)/ZnO nanocomposites film using solution casting method. Thin Solid Films, v. 519 p. 8375-8378, 2011.
9:00 AM - GG3.10
Nanostructured Films Based on Gold Nanoparticle/Conducting Polymer for Application in Electronic Tongue Sensors
Luiza Amim Mercante 1 Marcelo Saito Nogueira 1 2 Daniel Souza Correa 1 Luiz Henrique Capparelli Mattoso 1
1Embrapa Instrumentaamp;#231;amp;#227;o Samp;#227;o Carlos Brazil2Universidade de Samp;#227;o Paulo Samp;#227;o Carlos BrazilShow Abstract
The use of electronic tongue devices based on polymeric materials to evaluate and distinguish liquids has grown largely in the last decade due to its sensitivity and versatility. These sensors are generally obtained by the deposition of an active layer onto an electrode to interact with the analytes. For this, several film fabrication techniques have been used, emphasizes to the Layer-by-Layer (LbL) technique. In addition, the development of new materials for modifying the sensing units of the electronic tongue is crucial to improve the sensibility and sensitivity of the sensor. Therefore, in this study we focus on the production of materials whose properties are varied significantly by the interplay among their constituents. More specifically, we incorporate gold nanoparticles (AuNP) in the polymeric matrix of poly(allylamine hydrochloride) (PAH) to enhance the properties of tetrasulfonated nickel and cupper phthalocyanine (NiTsPc and CuTsPc) in LbL films. Characterization of the surface morphology, roughness and other physicochemical properties of nanostructured films were carried out by UV-Vis and Infrared spectroscopy, scanning electron microscopy, atomic force microscopy and electrical measurements. The UV-vis absorption spectroscopy revealed that both the Au@PAH/TsPc LbL films grow linearly with the number of deposited bilayers. According to FTIR data, the LbL film growth might be driven by electrostatic interactions between the NH3+ and SO3minus; groups from PAH and TsPc, respectively. The electrical behavior of LbL films was evaluated by measuring the electrical impedance, from 1 Hz to 1 MHz, and the results revealed an improvement of resistivity response due the presence of gold nanoparticles. The results demonstrated that the growth of Au@PAH/MTsPc LbL films was successfully achieved and therefore these films could be used in sensing and biosensing applications.
Acknowledgements: We thank financial support from FAPESP (Proc. 2013/23880-3), CNPq, CAPES, MCTI and EMBRAPA from Brazil.
9:00 AM - GG3.11
Nanocrystalline Zn1-xCoxO Thin Films: Structural, Morphological and Ozone Gas Sensing Properties
Ariadne Cristina Catto 1 Luis Fernando da Silva 2 Maria Ines Bernardi 1 Carlos Escanhoela 1 Valmor Roberto Mastelaro 1
1Instituto de Famp;#237;sica de Samp;#227;o Carlos, University of Samp;#227;o Paulo Samp;#227;o Carlos Brazil2Samp;#227;o Paulo State University Araraquara BrazilShow Abstract
Zinc oxide (ZnO) pure or doped are one of the most promising metal oxide semiconductors for gas sensing applications due to the well-know high surface-to-volume area and surface conductivity. ZnO has been proved to be an excellent gas-sensing material for different gases such as CO, O2, NO2 and ethanol. In this context, ZnO pure or doped exhibiting different morphologies and a high surface/volume ratio can be a good option regarding the limitations of the current commercial sensors. Different studies showed that the sensitivity of metal-doped ZnO (e.g. Co, Fe, Mn,) enhanced their gas sensing properties. Motivated by these considerations, the aim of this study consisted on the investigation of the role of Co ions on structural, morphological and the gas sensing properties of nanostructured ZnO samples.
ZnO and Zn1-xCoxO (0 < x < 5 wt%) thin films were obtained via the polymeric precursor method. The gas sensing properties as sensitivity, response time and long term stability, were investigated for a 33 to 930 ppb concentration range of ozone at different working temperatures. The gas sensing property was probed by electrical resistance measurements. The long-range and short-range structures around Zn and Co atoms were investigated by X-ray diffraction and X-ray absorption spectroscopy, while the microstructural characteristics of thin films were analyzed by a field-emission scanning electron microscope (FE-SEM).
XRD patterns of Zn1-xCoxO samples were indexed to the wurtzite ZnO structure and any second phase was observed even at a higher cobalt content. Co-K edge XANES spectra revealed the predominance of Co3+ ions. FE-SEM images showed that particle size decreases in function of cobalt content (40 - 30 nm). Gas sensor measurements pointed out that ZnO and Co-doped ZnO samples exhibit a good gas sensing performance concerning the reproducibility and a fast response time (around 10 s). The sensitivity value (Rgas/Ro) of ZnO was 45.0 when exposed to 33 ppb ozone at 250°C. Nevertheless, the Co addition contributed to reduce the sensitivity to ozone gas.
9:00 AM - GG3.12
A Research on Advanced Processes to Enhance the Ferro-, Piezoelectric Properties of PVDF(Poly Vinylidene Fluoride) Nanocomposite
Junyoung Lim 1 Yongsok Seo 1
1Seoul National University Seoul Korea (the Republic of)Show Abstract
Poly(vinylidene fluoride) (PVDF) has received much attention in recent years as a material for an organic sensor, due to its unique electric properties such as piezo-, pyro-, ferroelectric responses against external stimuli. Those properties are caused by characteristic structures, which are several forms like alpha (TGTG), beta (TTTT), and gamma(TTTGTTTG') phases. The electronegativity difference between fluorine and hydrogen attached to the backbone makes dipole moment along the perpendicular direction to chain axis. In alpha phase, however, all dipole moments cancel each other and make the net moment zero. On the other hand, the beta formed one shows strong net dipole moment when all dipoles are aligned in the same direction. In a preceding research, beta formed PVDF crystal shows well defined hysteresis P-E loop as a ferroelectric material, and large displacement in a electric field as a piezoelectric material. To achieve highly beta formed crystal, there are two basic principles in the applications. One is mechanical stretching. All trans conformation of beta formed crystal has the longest unit length, that's why elongational stress can induce the phase transformation from alpha to beta. And from the ferroelectric property, strong electric field makes the dipole moments aligned to the filed direction causing the structure to be beta formed.
In this study, we introduced some processes to manufacture the highly beta formed PVDF nanocomposite and to simplify the process. Nanotubes made from different atoms are added to the composite to increase an elongational effect, and the external electric field gets the dissolved solution stretched and electrically repulsed into the spinning jet, promoting the beta phase transformation. The rapidly rotating roll collects the spun fibers, causing further stretching effect. WAXD(Wide Angle X-ray diffraction) and FTIR(Fourier Transform Infrared Spectroscopy) were chosen to verify the amount of beta formed crystals in each samples.
9:00 AM - GG3.13
Multifunctional Nanocomposite Ion Gels from Gold Nanoparticles Templated Liquid Crystalline Brush Block Copolymers
Thanh Nguyen 1 Rajeswari M. Kasi 1
1University of Connecticut Storrs USAShow Abstract
We examined the influence of confining gold nanoparticles templated within hierarchically structured thiol functionalized liquid crystalline brush block copolymers (LCBBCs) gelled in ionic liquids on the overall nanoscale morphology, mechanical and electrochemical properties of the nanocomposite ion gels. In the first step, gold nanoparticles (AuNPs) were prepared by in situ reduction of the gold ions and stabilized by direct anchoring through the coordination bonds with the thiol functionalized LCBBCs. The resulting LCBBC/AuNPs nanocomposites comprised a hierarchical structure in which polymer-coated AuNPs were dispersed in a microsegregated LCBBCs matrix that further contained both LC and block copolymer ordering. In the second and final step, these LCBBC/AuNPs nanocomposites were solubilized in ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate, to form nanocomposite ion gels. The hydrophilic PEO unit is soluble in IL, while LC domains and AuNPs were insoluble in IL and formed junctions within the LCBBC/AuNPs nanocomposites ion gel network, which predominantly provides mechanical robustness to the ion gels. At 5 wt% concentration, strong LCBBC/AuNPs nanocomposites ion-gels exhibit interesting characteristics including excellent mechanical strength (~ 103 Pa), good optical properties with higher ionic conductivity (~ 10-2 Scm-1) and long-term electrochemical stability over the large potential range than plain polymer ion gels as well as other controls. Thus, self-assembled nanocomposite ion gels by virtue of their architecture and functionality encompassed tunable morphological, optical, thermal and mechanical properties are attractive new materials, offers a promising and versatile approach to design nanocomposite ion gels for templating various nanoparticles with multiple functionalities for applications in catalysis, electrochemical devices, photonic, and opto-electronics.
9:00 AM - GG3.14
Spectroscopic and Computational Analysis of Nickel-Germanium Clusters
Sinem Esra Ogun 1 Okan Esenturk 1 Emren Nalbant Esenturk 1
1Middle East Technical University Ankara TurkeyShow Abstract
In recent years, there is a strong preference toward bimetallic systems due to their superior properties. Transition metal integrated main group clusters (i.e. [PtPb12]2-, [Ni2Sn17]4-, [Ni2Ge9(PPh3)]2-, [Ni6Ge13(CO)5]4-, etc.) have strong potentials to be used as precursors to bimetallic nano-catalysts, in photovoltaic devices, light emitting diodes or in laser applications. Therefore, it is very important to investigate the spectroscopic properties of these clusters to improve currently used systems or develop new ones for applications in nanotechnology. In this study, optical and vibrational properties of the Nickel-Germanium clusters have been investigated via UV-Vis, FTIR, Fluorescence and Raman Spectroscopy. Also, frequency and Time-Dependent (TD) electronic transition calculations have been performed to complement the experimental results. The spectroscopic and computational findings toward evaluation of their potential future applications will be presented.
9:00 AM - GG3.15
Lead Clusters Encapsulating Transition Metals: Spectroscopic and Computational Investigation
Asude Cetin 1 Okan Esenturk 1 Emren Nalbant Esenturk 1
1Middle East Technical University Ankara TurkeyShow Abstract
The growing demand on new technologies in recent years is toward miniaturization of devices into nanometer size with enhanced performances. Currently, nanomaterials, especially bimetallic systems, are subject of intense research due to their unique properties. Transition metal integrated main group clusters (i.e. [PtPb12]2-, [Ni2Sn17]4-, [Ni2Ge9(PPh3)]2-, [Ni6Ge13(CO)5]4-, etc.) have a wide variety of application area including nanocatalysis, photovoltaic devices, light emitting diodes or laser applications. Therefore, it is essential to perceive the spectroscopic properties of these clusters in order to develop new ones with superior properties for various applications in nanotechnology. In this study, optical and vibrational properties of transition metal integrated lead clusters have been investigated. Experimental findings from UV-Vis, FTIR, Fluorescence and Raman Spectroscopy supported with frequency and Time-Dependent (TD) electronic transition calculations will be presented.
9:00 AM -
moved from GG3.02 to GG6.14
GG1: Optical Sensing
Monday AM, December 01, 2014
Hynes, Level 2, Room 209
9:30 AM - *GG1.01
Coupled Plasmonics-Enabled Chemical Sensors and Thermal Energy Harvesting Structures
Nicholas Karker 1 Gnanaprakash Dharmalingam 1 Michael A Carpenter 1
1College of Nanoscale Science and Engineering Albany USAShow Abstract
The surface plasmon resonance band of gold nanomaterials embedded in metal oxide heterostructure films is used both as an energy harvesting device structure as well as an optical beacon for the detection of emission gases, CO, NO2 and H2, at temperatures ranging between 500 and 800oC. A summary of previous experiments detailing the sensing characteristics will be provided. Challenges for the detection of emission gases include high levels of sensitivity, the selective detection of the gas of interest within a catalytically active environment as well as surmounting future integration challenges. Recent work will be detailed which shows the implementation of plasmonic based sensing arrays for the detection of emission gases. Variations in nanoparticle size, shape, geometric arrangement as well as the metal oxide matrix chemistry are being varied to produce next generation sensing arrays with enhanced selective sensing properties. Coupled with these recent studies is the novel design of plasmonic arrays that are being developed for their energy harvesting capabilities. Studies will be detailed on these next generation plasmonic structures that include their energy harvesting characteristics and subsequent detection of emission gases without the need of an external white light excitation source.
10:00 AM - *GG1.02
Surface Enhanced Raman Scattering Sensing of Chemicals with Highly Stable Nanostructures
Sheng Dai 1 2
1Oak Ridge National Laboratory Oak Ridge USA2University of Tennessee Knoxville USAShow Abstract
This presentation will be focused on the development of a novel thermally stable surface enhanced Raman scattering (SERS) substrate. Specifically, these substrates can withstand high temperatures in air for an extended period of time without the loss of their enhancement capabilities. To accomplish this, we utilized a bottom-up approach, where the polyol reduction process was used to synthesize silver nanowires (NW) that were roughly 90 nm wide to act as the SERS active moiety. Subsequently, the NW were coated with a thin protective layer of Al2O3 via atomic layer deposition (ALD) or surface sol-gel process (SSP). After heating these SERS substrates at 400°C for 24 h in air, it was found that the coated samples maintained a significant enhancement of the Raman signal, with further heating resulting in effectively no change in the SERS spectrum. The stability imbued by the ALD coating stems from limiting surface oxidation along with impeding aggregation that occurs at the higher temperature, which would otherwise lead to the destruction of the nanomorphology and complete loss of the SERS capabilities. These highly stable SERS substrates highlight the potential application of SERS in investigation of high-temperature chemical reactions and catalytic processes.
10:30 AM - GG1.03
Correlated Perovskite Films for Optical Sensing Applications in Extreme Environments
Andrew M. Schultz 1 Thomas D. Brown 1 Paul R. Ohodnicki 1
1National Energy Technology Laboratory Pittsburgh USAShow Abstract
Improvements in conventional fossil energy technologies requires increased ability to monitor gas species in extreme conditions such as high temperatures, high pressures, highly reducing or oxidizing atmospheres, and corrosive gases. Optical waveguide sensors with metal oxide thin films that measure optical changes as a result of changing external conditions represent a promising step forward in sensor development. The fuel stream of solid oxide fuel cells (SOFCs) is a promising target for improvements in gas sensing technology, with high operating temperatures and reducing gas streams. This talk reports on the optical gas sensing response of La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM), which has already stability as an anode material in SOFC systems. The near-IR transmission and resistivity response to varying hydrogen levels (1-100%) in a nitrogen background is reported. LSCM shows a large response to reducing gas streams with good recovery and stability. Simultaneous resistivity measurements allow for correlation of optical sensing response to traditional chemi-resistivity sensing literature. The effect of operating temperature on the resistivity and optical response is also reported. These results show high promise for incorporation of well-studied correlated conducting oxide systems into novel waveguide sensors.
10:45 AM - GG1.04
Irradiation Response of Graphene Enhanced Gallium Nitride Ultraviolet Photodetectors
Heather C Chiamori 1 Chetan Angadi 2 Nicholas Broad 3 Ruth Miller 1 Sharmila Bhattacharya 2 Debbie G Senesky 1
1Stanford University Stanford USA2NASA Ames Research Center Moffett Field USA3Stanford University Stanford USAShow Abstract
The performance of graphene-based ultraviolet (UV) photodetectors fabricated on gallium nitride (GaN) substrates is investigated under ambient and irradiated conditions. For harsh environment applications, UV photodetectors must be robust and handle conditions such as high temperatures, chemically corrosive or radiative environments. GaN is a candidate harsh environment material platform due to its wide bandgap (3.4 eV). GaN devices can operate at higher temperatures, handle higher power requirements and tolerate higher energy/radiative conditions. III-V nitrides (e.g. GaN) can be alloyed with ternary elements for heterostructured devices with potential cut-off wavelength control based on ternary element amounts. The integration of GaN with nanomaterials such as graphene can provide additional functionality.
The metal-semiconductor-metal (MSM) UV photodetector architecture consists of interdigitated comb finger electrodes (typically metal) patterned on a semiconductor substrate. When biased, MSM photodetectors should exhibit linear behavior and low dark currents. For GaN-based UV photodetectors fabricated on silicon wafers, devices can suffer topside illumination losses due to opaque metal electrodes, reducing external quantum efficiency. Enhancement of photodetector performance can occur with use of semi- or transparent electrodes.
Graphene has outstanding electrical, optical, and mechanical properties. A two-dimensional material consisting of carbon atoms arranged in a honeycomb configuration, graphene exhibits room temperature ballistic transport, high charge carrier mobilities and high current carrying capability. Additionally, graphene has absorption of 2.3% across the visible spectrum and a flat absorption spectrum from 300 to 2,500 nm, with potential for optical and optoelectronics applications. Specifically, graphene can be used as a transparent, conductive electrode material.
Although graphene was first isolated using mechanical exfoliation, the development of chemical vapor deposition (CVD) techniques and transfer methods has allowed large area integration for sensor applications. Using CVD-growth graphene and transfer techniques, graphene-based UV photodetectors are fabricated on GaN substrates, with graphene forming the metal portion of the MSM photodetector. The photodetector behavior is characterized using a UV light source under ambient and irradiated conditions (Cs-137 source). Raman spectroscopy is used to investigate the structural disorder of the graphene photodetectors. Recent studies have shown that graphene encapsulation can protect materials from electron beam irradiation damage as well as improve 1/f noise in graphene devices. As such, graphene may prove to be a radiation tolerant material that can be used in combination with GaN for extreme harsh environment applications.
11:30 AM - GG1.05
A Chemical Sensor for CO2 in Aqueous Environment Based on Fibre Optic Sensing Modified with a CO2 Responsive Coating
Marieke Burghoorn 1 Arjen Boersma 1 Ralph Stevens 1 Bob Dirks 2 Jolanda van Medevoort 3
1TNO Eindhoven Netherlands2TNO Delft Netherlands3TNO Zeist NetherlandsShow Abstract
During the last decade, the capture and storage of CO2 is presented as an important method to control the CO2 emission. CO2 chemical sensing in soil and water may contribute significantly to safe CO2 storage and is also relevant to horticulture. Contrary to commonly used electrochemical CO2 sensing systems, fibre Bragg gratings (FBG) enable sensing over large distances and at several locations and is a low maintenance and sensitive distributed chemical sensor system on a well known optical platform. The FBG is a one dimensional periodic array of high and low refractive index sections in the core of the fibre. Light is reflected on this grating, and the reflected wavelength depends on the periodic distance in the grating and thus changes with deformation of the fibre.
In order to use the FBG for chemical sensing applications, chemically responsive coatings are developed and applied to the FBG. The coating should expand and/or contract upon a change in CO2 partial pressure in aqueous environment. The swelling of the material must be carefully tuned, because high swelling will result in coating delamination from the glass fiber, and low swelling will not give enough response. The coating should maintain its mechanical strength in all circumstances to be able to stretch the glass fiber and thus cause a difference in reflected wavelength.
Here we present a responsive polymer coating that fulfils these requirements. Upon the presence of CO2, the pH of the water will change, which is measured with the coated FBG. The monomer solutions are processed using coating application equipment. The polymer coatings are mechanically stiff, have a good adhesion to the fibres and have proven to be durable so far. In order to reach these properties, a process for the application of the coating to the fibre was optimised and includes fibre stripping and cleaning, application of an adhesion promoter, application of the responsive coating and a post-treatment. The coated FBG is packaged with a semipermeable membrane which is permeable for gasses and water, but is impermeable for ions. The package protects the fragile coated FBG and in addition optimizes the sensor response. The packaged sensor was immersed into an aqueous solution and exposed to 100 % CO2 (1 bar)(resulting in decreasing pH) followed by 100 %N2 (to increase pH again) in several test cycles. Automatic measurements of the FBG wavelength response were performed in time. Using a detection resolution of 0.5 pm, fully reversible responses in the order of 200 pm with a good signal to noise ratio are measured with a response time of less than 3 hours.
11:45 AM - GG1.06
Localized Collection of Airborne Analytes: A Transport Driven Approach to Improve the Response Time of Existing Gas Sensor Designs Including SERS Based Detection of Small Molecule
Jun Fang 1 Se-Chul Park 1 Leslie Schlag 2 Thomas Stauden 2 Joerg Pezoldt 2 Heiko Jacobs 2
1University of Minnesota Minneapolis USA2Ilmenau University of Technology Ilmenau GermanyShow Abstract
We describe a new transport mechanism that supports the localized collection of airborn analytes at higher rates when compared to diffusion based standard commonly used. It combines advanced aerosol science with novel nanosensor designs.
Background: The detection of single molecular binding events has been a recent trend in sensor research introducing various sensor designs where the active sensing elements are nanoscopic in size. While it is possible to detect single binding events, the research has not yet addressed the question of how to effectively transport airborne analytes to these point-like sensing structures. Currently, diffusion-only-transport is used and it becomes increasingly unlikely for an analyte molecule to “find” and interact with sensing structures where the active area is shrunk in size, trading an increased sensitivity with a long response time.
Approach: Instead of using diffusion-only-transport, we introduce various analyte charging methods and electrodynamic nanolens based analyte concentration concepts to transport airborne analytes to nanoscopic sensing points to improve the response time of existing gas sensor designs. We demonstrate localized collection of analytes over a wide range of molecular weights ranging from 3×1017 to 1×102 Daltons, including (i) microscopic analyte particles, (ii) inorganic nanoparticles, all the way down to (iii) small organic molecules. We also demonstrate first experimental results towards an programmable active matrix based analyte collection approach referred to as “Airborn Analyte Memory Chip/Recorder” for “offsite” analyte analysis, which (i) takes samples of the particles or molecules in an Aerosol at specific points in time, (ii) transports the analyte sample to a designated spot on a surface, (iii) concentrates the analyte at this spot to achieve an amplification, (iv) repeats this sequence until the recording matrix is full, and (v) reads out the analyte matrix on the chip.
Implications: In all cases we find that the collection rate is several orders of magnitudes higher than diffusion-only-transport. The collection scheme is integrated on an existing surface-enhanced Raman spectroscopy based sensor. The process is able to detect analytes at 9 parts per million within 1 second. As a comparison, 1 hour is required to reach the same signal level when diffusion-only-transport is used. The novel “Airborn Analyte Memory Chip/Recorder” achieved by this approach could be a commodity item that is placed in an environment that a user would like to keep a record from. The information is retrieved on an as needed basis. Offsite analysis of the chip storing the information would make this approach more economical than an online monitoring system for all kinds of threads.
Jun Fang et al., Advanced Functional Materials (in press) (2014).
En-Chiang Lin et al., Advanced Materials 25(26), 3554-3559 (2013).
En-Chiang Lin et al., Nature Communications 4-1636 (2013).
12:00 PM - GG1.07
Optical Based Functional Sensor Materials for High Temperature, Harsh Environment Sensing Applications
Paul Ohodnicki 1 Andrew Schultz 1 Congjun Wang 1 John Baltrus 1 Thomas Brown 1
1National Energy Technology Laboratory Pittsburgh USAShow Abstract
High temperature compatible harsh environment sensors can enable improved process control for higher-efficiency, lower emission power generation applications. Such sensors can also have broad impacts across an array of other industries and applications including nuclear power generation, aviation, aerospace, and industrial manufacturing. Optical based sensor platforms are attractive because they (1) eliminate many common failure modes of electrical based sensors such as the need for electrical wiring and interconnects at the sensing location, (2) reduce the risk of explosions due to an electrical spark when deployed in explosive atmospheres, and (3) allow for increased functionality due to compatibility with broadband wavelength interrogation and distributed sensing methodologies. As a result, a recently established sensor material effort at the National Energy Technology Laboratory has placed an emphasis on the research and development of new optical based functional sensor layers along with prototype sensor demonstration on evanescent wave absorption spectroscopy-based sensor devices for extreme temperature applications. An overview of the current research efforts will be presented including new experimental results of gas sensing at temperatures ranging from 300-800oC coupled with theoretical modeling of both materials and functionalized sensors to explain measured sensing responses. Future research directions for improved materials and sensor development will be highlighted.
12:15 PM - GG1.08
Controllable Growth of Aluminum Nanorods Using Physical Vapor Deposition for Inexpensive and Degradation-Resistant Surface Enhanced Raman Spectroscopy
Stephen P Stagon 1 Xuefei Tan 2 Yongmin Liu 2 3 Hanchen Huang 2
1University of North Florida Jacksonville USA2Northeastern University Boston USA3Northeastern University Boston USAShow Abstract
Surface enhanced Raman spectroscopy (SERS) using metallic nanorod substrates has been generally limited to the laboratory setting due to rapid nanostructure degradation in ambient. Beyond just ambient, the extension of SERS to high temperature or reactive environment has not been possible due to even faster degradation of nanostructures in extreme conditions. Aluminum (Al) may be a unique candidate for SERS sensing in extreme conditions due to the formation of a stable surface passivation layer of aluminum oxide while maintaining moderate enhancement in SERS. However, existing theory and atomistic simulations indicate that the growth of Al nanorods using physical vapor deposition should be impossible. Here, through the use of oxygen (O) as a surfactant, we realize the controllable growth of Al nanorods using PVD and illuminate the mechanism enabling the growth of Al nanorods using PVD. It is proposed and experimentally validated that the concentration of O in the vacuum chamber during growth dictates the coverage of kink sites and step edges during growth. The binding of O at the Al kink or step edge increases the local kinetic barriers for a diffusing adatom. As diffusion from the top terrace dictates the diameter of nanorods grown from PVD, the diameter of Al nanorods can be controlled through modification of vacuum level during growth. When grown through this mechanism, Al nanorods have a protective shell of ~2nm of Al oxide. Through long term thermal annealing in ambient, it is shown that this oxide layer is stable at ~2nm in thickness to at least 475K and that the morphology remains unchanged up to 1275K, at which point the nanorods are fully crystalline Al2O3.
Taking the nanorods to technological application, SERS, for the detection of trace amounts of N-719 dye, is performed using the Al nanorods as substrates. Freshly fabricated Al nanorods produce moderate enhancement factors of ~103. The order of enhancement factor is maintained after annealing the Al nanorods in ambient for 30 days or at 475K for one day prior to use. Beyond enhancement and stability, Al is also attractive as an alternative to noble metal nanostructures due to its relative abundance and low cost. Our results indicate that the controllable growth of Al nanorods would enable a new breed of resilient SERS sensors.
12:30 PM - GG1.09
Towards Thermally Robust Chemical Sensors for Harsh Environments
Hui Chen 1 Fei Tian 1 Henry Du 1
1Stevens Institute of Technology Hoboken USAShow Abstract
The ability of Ag plasmonic nanostructure for surface-enhanced Raman spectroscopy (SERS)-based chemical sensing and measurements in harsh environments is a long-recognized challenge due to their tendency to coalesce or to Ostwald ripen at elevated temperatures, which diminishes SERS enhancement. We have fabricated thermally robust SERS substrates with Ag nanoparticles that maintain their discret size and distribution upon exposure to high temperature. Nanoparticles were immobilized on a porous anodized aluminum oxide (AAO) template via in situ growth from electroless-deposited Ag seeds and heated up to 500 0C for 360 min. The substrates were characterized at room tempreture with SERS, SEM and UV-VIS spectroscopy after heat treatment. Trapping nanoparticles within the pores of AAO prevented the coalescence of colloids at elevated temperatures, thereby preserving their LSPR and SERS activity. The feasibility of this thermally robust SERS-based sensor is demonstrated using both aqueous Rhodamine 6G (R6G) solution (as low as 10-7 M) and toluene vapor (#65374;2-3%) as modal analytes.
Pu-Xian Gao, University of Connecticut
Joseph V. Mantese, United Technologies Research Center
Paul Ohodnicki, National Energy Technology Laboratory
Lin Shao, Texas Aamp;M University
GG5: Sensors for Sustainable Environment
Tuesday PM, December 02, 2014
Hynes, Level 2, Room 209
2:30 AM - *GG5.01
Materials for High Temperature Electrochemical Applications: Fuel Cells, Sensors, Catalysts and Traps
Harry L Tuller 1
1MIT Cambridge USAShow Abstract
Extensive emissions and fuel economy directives are stimulating the development of ever more sophisticated energy conversion systems, sensors and catalyst systems with improved performance and self-evaluation capabilities. For the development of such systems, deeper insights are required to understand the often complex interplay between the chemical state of the material and its electrical, optical, thermal and mechanical properties. Examples, illustrating how information gained about the defect, electronic and transport structure of oxide materials can be used to optimize properties, are presented. Particular emphasis is focused on means for in-situ monitoring of the status of fuel cell electrodes, catalysts and traps.
3:00 AM - *GG5.02
Template-Realized Three-Dimensional Functional Nanostructures for Sensor and Energy-Related Device Applications within a Wide Temperature Range
Yong Lei 1
1Technical University of Ilmenau Ilmenau GermanyShow Abstract
With the device miniaturization, functional surface nanostructures become the foundation of modern and future devices. Comparing to planar nanostructures, three-dimensional (3D) nanostructures have extremely large surface areas and high structure densities, hence the realization of 3D nanostructures presents an important task for nanotechnology research. To address this point, template-based 3D nanostructuring techniques with scalable, parallel and fast fabrication processes have been developed in our group. Using these techniques, different 3D semiconductor nanostructures are achieved with advantageous features including perfect regularity of large-scale nanostructure arrays, high density, scalable and parallel fabrication processes, and cost-effectiveness, which are highly desirable for device applications. More importantly, the obtained 3D nanostructures have high structural controllability, which makes these 3D nanostructures as good systems for optimizing their properties. An addressing system of 3D nanostructures with nano-scale resolution is proposed for property investigation and device integration. Using these well-defined semiconductor nanostructures, high performance devices have been realized, mainly for energy-related applications (i.e., supercapacitors) that can be used within a wide temperature range and sensor applications. These achievements indicate the high potential and importance of the 3D nano-structuring techniques both for basic research and for device applications.
 Lei Y., Yang S.H., Wu M.H., Wilde G., Chemical Society Reviews, 40, 1247, 2011.
 Vellacheri R., Al-Haddad A., Zhao H.P., Wang W.X., Wang C.L., Lei Y., Nano Energy, 8, 231, 2014.
 Zhan Z.B., Lei Y., ACS Nano, 8, 3862, 2014.
 Wen L.Y., Mi Y., Wang C.L., Zhao H.P., Grote F., Zhan Z.B., Zhou M., Lei Y., Small, in press (DOI: 10.1002/smll.201400436), 2014.
 Cao D.W., Wang Z.J., Nasori, Wen L.Y., Mi Y., Lei Y., Angewandte Chemie International Edition, in press, 2014.
 Zhou M., Bao J., Xu Y., Zhang J.J., Xie J.F., Guan M.L., Wang C.L., Wen L.Y., Lei Y., Xie Y., ACS Nano, in press (DOI: 10.1021/nn501996a), 2014.
3:30 AM - GG5.03
High Temperature Mass Flux Sensors Using ZnO Nanorod Arrays
Hui-Jan Lin 1 Pu-Xian Gao 1
1University of Connecticut Storrs USAShow Abstract
The air and feedstock flux entering into a high temperature engine, a blast furnace, or a coal (or gas) -fired power plant is traditionally measured by either indirectly from temperature and pressure data, or directly using a total pressure probe. Meanwhile, sophisticated and large-size laser diode based measurement system is also being implemented as a promising in-situ monitoring technique at the moment. How to shrink the system and make it portable becomes a great challenge in this case. Herein, a miniaturized and portable measurement method is proposed here that can directly detect gas concentration and flow rate in-situ and real-time simultaneously.
The example sensor candidate is based on ZnO nanorod arrays which have been studied for detection of various inflammable gases including NO2, C2H5OH, CO, and H2. Here we successfully fabricated uniform and long ZnO nanorods array gas sensor by a continuous hydrothermal flow synthesis method. The respective ZnO nanorod gas sensor has been tested using amperometric detection mode. Meanwhile a piezoresistive signal on the ZnO nanorod surface is reliably extracted dependent on gas flow induced pressure on the nanorod arrays. These signals are systematically demonstrated with a good response and dual-signal differentiation ability upon different gas flow rates and concentrations of multiple gases at high temperature up to 800oC. The new type of ZnO nanorod array based gas flux sensors have shown high stability, high sensitivity, quick response and recovery time as well as high selectivity.
3:45 AM - GG5.04
Role of Self Assembled Hexagonal Structured Delafossite CuAlO2 Nanoparticles for Superior Ozone Gas Sensing Performance
Thirumalairajan Subramaniam 1 Valmor R. Mastelaro 1
1Instituto de Famp;#237;sica de Samp;#227;o Carlos (IFSC) Sao Carlos BrazilShow Abstract
In this study, we present a facile hydrothermal synthesis of hexagonal structured delafossite CuAlO2 comprised of nanoparticles with typical size ~ 70 nm, thermally stable up to 1200 ° C. Phase analysis carried out using X-ray diffraction and micro-Raman scattering confirmed the single-phase structure of delafossite CuAlO2. The field-emission scanning electron microscopy images revealed the hexagonal surface and the average nanoparticle size was estimated using transmission electron microscope. The gas sensing performance of delafossite CuAlO2 was tested towards ozone gas. At the operating temperature, the resistance of sensor decreased upon exposure to 200 ppb of ozone. This phenomenon is explained by the gas sensing characteristics of p-type semiconductor oxide. The hexagonal structured CuAlO2 detects ozone at a low range of 200 °C with 10 fold larger response than the earlier reported values for other delafossite structures. The results suggest that morphology plays an important role in the performance of sensor. Thus, hexagonal CuAlO2 structures can be considered as a good candidate for ozone gas sensor application.
Keywords: CuAlO2, delafossite, hexagonal, morphology, nanoparticle, ozone gas
4:30 AM - GG5.05
Facile Fabrication of Well-Ordered Porous Cu-Doped SnO2 Thin Film for H2S Sensing
Shuming Zhang 1 Pingping Zhang 1 Xuhui Sun 1
1Soochow University Suzhou ChinaShow Abstract
The well-ordered Cu-doped SnO2 and un-doped porous thin films with high specific surface area have been fabricated on a desired substrate using self-assembled soft templates combined with a simple physical co-sputtering deposition. The Cu-doped SnO2 porous film gas sensor shows a significantly enhancement in the sensing performance including high sensitivity, selectivity, reproducibility, and fast response and recovery time. The sensitivity of Cu-doped SnO2 porous sensor is one order higher than that of un-doped SnO2 sensor with the average response and recovery times to 100ppm H2S of about 10.1 and 42.4s, respectively, at the optimum operating temperature of 180°C. The well-defined porous sensors fabricated by the method exhibit high reproducibility due to the accurately controlled process. The facile fabrication process can be easily extended to other semiconductor oxide gas sensors fabrication with easy doping and multilayer porous nanostructure for the practical applications.
4:45 AM - GG5.06
Semiconductor-Like Sensitivity using Ultrathin Gold Nanowire Sensors
Ahin Roy 1 Tribhuwan Pandey 1 Ravishankar N 1 Abhishek Kumar Singh 1
1IISc Bangalore IndiaShow Abstract
1-D Semiconductors have been preferred materials for fabrication of chemical sensors due to the ease of adsorption-induced electronic structure modification. However, at nanoscale, surface passivation leads to deterioration of the merit of their sensitivity. In this study, using first principles density functional theory combined with Boltzmann transport calculations, we have observed sensitivity of as high magnitude as semiconductor nanowires towards chemical species in ultrathin gold nanowires (AuNWs). We observe that the sensing mechanism is directed by the modification of electronic structure of the AuNW and adsorption-induced scattering. Most importantly, the sensitivity of the system shows a linear relationship with the electron affinity of the analyte species. Based on this relationship, we propose an empirical parameter, which can predict an analyte-specific sensitivity of an AuNW, rendering them as effective sensor for a wide range of chemical analytes.
5:00 AM - GG5.07
Effect of Reaction Medium Polarity on Hierarchical Growth of In2O3 Architectures for Gas Sensing Applications
Manorama V Sunkara 1 Arunkumar Shanmugasundaram 1 Pratyay Basak 1
1CSIR-Indian Institute of Chemical Technology Hyderabad IndiaShow Abstract
Recent advances in synthesis strategies exercising appreciable control on the nucleation /growth can help to obtain exotic nanostructures and well defined morphologies. This has opened up newer possibilities to revisit and redesign materials with superior properties. The present work explains in detail a one pot hydro-/solvo- thermal synthesis route for the preparation of well defined bcc-In(OH)3 architecture. The morphological variation such as spheres, cubes, nano-diamonds, and nanoparticles could be obtained by the simple modulation of the reaction medium polarity. Hierarchical In(OH)3 architectures were synthesised by a hydro-/solvo- thermal route using indium chloride as the metal precursor and ethanolamine as the organic Lewis base. The polarity of the reaction medium was found to play a determining role on the final morphology of In(OH)3 obtained. A plausible mechanism of formation for these hierarchical In(OH)3 architectures could be postulated based on controlled experiments. Finally, transformation to porous In2O3 nanostructures while retaining the parent morphology could be achieved by calcining the corresponding In(OH)3 samples. The as prepared materials were characterized and assessed for their physico-chemical properties prior to their performance evaluation as gas sensor materials.
Detection and monitoring of harmful and inflammable gases are of great importance for monitoring environment and health. Among the various air pollutants, carbon monoxide (CO) is one of the most toxic gas, which reacts rapidly with human blood haemoglobin to form carboxy-haemoglobin and damages the human body by causing a reduction in cellular respiration. A trace amount of CO inhalation causes a large number of deaths annually in the world.1-3 Carbon monoxide sensing characteristics of the In2O3 nanostructures were investigated at different sensing temperatures (Ts) and at different gas concentrations (Gc). Gas sensing studies demonstrate an excellent sensing performance of the as prepared hierarchical In2O3 architectures in terms of high sensitivity (down to ppb level) as well as fast response (ΓRES)/recovery (ΓREC) time. Sensing response at room temperature and selectivity was improved substantially by the incorporation of gold nanoparticles into the In2O3 matrix.
Yamazoe, N. Sens. Actuators B 1991, 5, 7.
Kolmakov et.al. Adv. Mater.2003, 15, 997.
Guo et.al. CrystEngComm, 2013, 15, 4730-4738.
5:15 AM - GG5.08
Pd@SnO2 and SnO2@Pd Core@Shell Nanostructures for H2/CO-Sensing
Claus Feldmann 1
1Karlsruhe Institute of Technology (KIT) Karlsruhe GermanyShow Abstract
Gas sensors based on Semiconducting Metal Oxides (SMOX) are already multiply used to detect low concentrations of toxic and/or explosive gases (e.g. H2, CO, CH4, ethanol). They offer a low-cost, low-power-consumption alternative to sophisticated analytical equipment and can be easily deployed and operated. Originally, SMOX-based sensors date back to the pioneering work of Heiland, Bielanski and Seiyama . Even if such sensors are sold nowadays in millions per year , there is still much research to do to understand their function and the way how the active sensor surface interacts with the surrounding atmosphere, and finally, to improve their performance.
We have prepared core@shell nanocomposites with Pd0 encapsulated by SnO2 shells (Pd@SnO2) and SnO2 shells covered with Pd0 (SnO2@Pd) via water-in-oil (w/o)-microemulsions [3-5]. Such nanocomposites as model systems and a comparison of their sensor performance are shown for the first time. Both nanocomposites exhibit high-surface, porous matrices of SnO2 shells (>150 m2/g) with very small SnO2 crystallites (<10 nm) and Pd nanoparticles (<10 nm) that are uniformly distributed in the porous SnO2 matrix. Although similar by first sight, Pd@SnO2 and SnO2@Pd are significantly different in view of their structure with Pd inside or outside the SnO2 shell and in view of their sensor performance. As SMOX-based sensors both nanocomposites show a very good sensor performance for the detection of CO and H2. Especially, the Pd@SnO2 core@shell nanocomposite is unique and shows a fast response time (tau;90 < 30 seconds) and a very good response at low temperature (<250 °C), especially under humid-air conditions . Extraordinarily high sensor signals are observed when exposing the Pd@SnO2 nanocomposite to CO in humid air. Under these conditions even commercial sensors (Figaro TGS 2442, Applied Sensor MLC, E2V MICS 5521) are outperformed.
 A. Bielanski, J. Deren, J. Haber, Nature1957, 179, 668.
 K. Ihokura, J. Waston, The Stannic Oxide Gas Sensor: Principle and Application, CRC Press, Boca Raton 1994.
 D. H. M. Buchold, C. Feldmann, Nano Lett.2007, 7, 3489.
 H. Gröger, F. Gyger, P. Leidinger, C. Zurmühl, C. Feldmann, Adv. Mater.2009, 21, 1586.
 F. Gyger, M. Hübner, C. Feldmann, N. Barsan, U. Weimar, Chem. Mater.2010, 22, 4821.
 F. Gyger, A. Sackmann, M. Hübner, P. Bockstaller, D. Gerthsen, H. Lichtenberg, J.-D. Grunwaldt, N. Barsan, U. Weimar, C. Feldmann, Part. Part. Syst. Charact. 2014, 31, 591
GG6: Poster Session II: Nanomaterials for Harsh Environment Sensors II
Tuesday PM, December 02, 2014
Hynes, Level 1, Hall B
9:00 AM - GG6.01
Highly Sensitive Acetone Sensors Based on Rh Nanoparticles Embedded WO3 Nanofibers Synthesized by Electrospinning
Nam-Hoon Kim 1 Seon-Jin Choi 1 Sang-Joon Kim 1 Hee-Jin Cho 1 Il-Doo Kim 1
1KAIST Daejoen Korea (the Republic of)Show Abstract
Some of the volatile organic compounds (VOCs) in exhaled breath are used as bio-marker for specific diseases. Therefore, sensors for diagnostic use in exhaled human breath have attracted much attention due to their potential for fast, non-invasive, and convenient use; as well as the significant advantage of leaving no bio-hazardous waste, compared to conventional medical examination. Metal-oxide semiconductor gas sensors are good candidates for use as an exhaled-gas sensor because they chips and can easily be minimalized; however, in order to work well as breath sensors, metal-oxide semiconductor gas sensors need enhanced response and selectivity. In this work, we report remarkably improved properties of gas sensing by combining catalytic rhodium (Rh) nanoparticles (NPs) with WO3 nanofibers (NFs). We synthesized WO3 NFs by electrospinning, which is a facile and versatile process for producing webs of metal-oxide NFs. Rh NPs (2-4 nm) were synthesized using the polyol process. We functionalized Rh NPs inside of 1-D WO3 NFs by mixing dispersed Rh-NP solution with W-composite precursor/polyvinylpirrolidone (PVP) solution. The Rh NPs-WO3 NFs were obtained by calcination of the electrospinning as-spun fiber matrix at 600 °C. Addition of the Rh NPs, results in a rough surface morphology of the WO3 NFs, and also increases their gas-sensing properties. The gas-sensing characteristics of pure WO3 and Rh NPs-functionalized WO3 NFs, were tested using acetone, ethanol, H2S and toluene gases in a high humidity atmosphere (90% RH), which is similar to exhaled human breath. The results showed that Rh NPs-WO3 NFs exhibited about 2.5 times better response for acetone than did pure WO3 NFs. The high sensitivity to acetone by Rh NPs-WO3 NFs was attributed to the catalytic effect of the Rh NPs. The Rh NPs-WO3 NFs sensor also had a good enough response and recovery rate to be used as a VOC sensor for human exhaled breath. Therefore we propose that Rh NPs-WO3 NFs have strong potential for use in sensing acetone in exhaled human breath.
9:00 AM - GG6.02
ZnO-Based Metal-Semiconductor Junction
Taryam Al Shamsi 1 Ayman Rizk 1 Irfan Saadat 1
1Masdar Institute Abu Dhabi United Arab EmiratesShow Abstract
In this research the use of ZnO based sensors and thin-film transistors (TFT&’s) is explored for flexible large area sensor array applications. The sensors involve the use of an addressable array made of ZnO channel transistors and diodes fabricated on flexible substrates. This allows wearable sensor system that will be integrated into a remote low energy-sensing node for health care application. In this paper we are reporting the ongoing realization and optimization of ZnO-thin-film-based metal-semiconductor junction.
Samples consist of a thin (sim; 14 nm) ZnO-based film sandwiched between a 60 nm thick bottom metal contact and a top metal contact with thickness of 200 nm, deposited on a fused silica substrate.
The ZnO thin films were fabricated by means of radio frequency (RF) sputtering, creating a randomly oriented polycrystalline film structure. The junction comprises a Schottky contact as top electrodes (Ag, Ni) and an ohmic contact for bottom electrodes (Al, Ti) to induce the diode effect. Electrodes are deposited by means of DC-sputtering and thermal evaporation. For the metal-ZnO diodes, the barrier heights are as high as 1.00 V and 0.90 V for Ag and Ni respectively and as low as 0.00 V, 0.20 V for Al and Ti respectively.
The ZnO films deposited by RF sputtering lead to a different surface termination, stoichiometry and phase composition, so the influence of sputtering parameters such as total pressure, argon and oxygen flow on the Schottky behavior and film morphology are investigated theoretically and experimentally.
The devices resistivity and mobility are measured. Sentaurus Technology-CAD is used to simulate the band diagrams and output characteristics. Ellipsometer and XRD are used for ZnO film band gap and orientation characterization.
It is possible to achieve high electron mobility for sputtered ZnO on glass and thus maintaining good electrical conductivity. The ZnO film mobility is usually equal to the respective Hall-mobility for low interface traps; however, leakage currents may lead to the underestimation of the channel mobility. Measurements showed an increase of the reverse current which could be attributed to inhomogeneous barrier heights.
The obtained data are used to optimize the junctions for the TFT fabrication.
9:00 AM - GG6.03
Metallic Nanoparticle Diode and Electronics
Yong Yan 1
1Northwestern University Evanston USAShow Abstract
Diodes are essential to the exponential growth in computing capabilities and serve as a basic building block of many electronic components such as transistors, solar cells, and photodetectors. Despite broad importance, diodes have not been built from metals because the electric field that is needed to achieve current rectification cannot be established inside of a metal. Here we show that the junction between oppositely charged metal nanoparticles produces an electric field that rectifies current. Unlike other diodes such as the vacuum tube or p-n semiconductor diode, these metal nanoparticle diodes achieved highest currents under conditions that areanalogous to reverse bias in other material systems. To apply these diodes to the design of computational circuitry, we built working “AND” and “OR” logic gates and, in combination with metal nanoparticle sensors and resistors, we demonstrated all-metal nanoparticle circuits that functions as an “OR” or “NOR” gate. We expect that metal nanoparticle diodes will expand material choices, simplify the design of future electronic components, and provide functionality beyond that of traditional semiconductor p-n junctions.
9:00 AM - GG6.04
A Facile Method to Prepare ZnO Films via Hydrothermal Method: Room Temperature Ozone Gas Sensing Properties
Luis Fernando Da Silva 1 Baptiste Sauvage 2 3 Ariadne Catto 3 Caue Ribeiro 4 Valmor R Mastelaro 3 Khalifa Aguir 2 Elson Longo 1
1Samp;#227;o Paulo State University Araraquara Brazil2Aix Marseille Universitamp;#233; Marseille France3Instituto de Famp;#237;sica de Samp;#227;o Carlos, Universidade de Samp;#227;o Paulo Samp;#227;o Carlos Brazil4EMBRAPA Instrumentaamp;#231;amp;#227;o Samp;#227;o Carlos BrazilShow Abstract
The zinc oxide (ZnO) compound is one of the most promising metal semiconducting oxides for multifunctional applications, especially as chemiresistors. Additionally, ZnO compound has been proved to be an excellent gas-sensing material for toxic gases, such as CO, NOx, NO2, and O3. It is well established that ZnO microstructures exhibiting different morphologies and high surface/volume ratio can overcome the limitations of the current commercial chemiresistors. Herein, we investigated the influence of zinc precursor (sulfide, acetate, and nitrate) on the structural, morphological, and ozone gas sensing properties of ZnO thick films obtained by hydrothermal method at 110oC for 4 hours. The ZnO thick films were grown directly onto a SiO2/Si substrate with interdigitated Pt electrodes.
The crystalline phase and morphological features were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) measurements. The gas sensor measurements were carried out at room-temperature under blue light irradiation using different ozone levels (80 to 930 ppb).
X-ray diffraction measurements display a hexagonal wurtzite of ZnO with a preferential growth along  direction for the all samples. FE-SEM images show that the morphology of the both ZnO films obtained from zinc nitrate and acetate consists of the hexagonal nanorods of ca. 150 nm. Whereas, the ZnO film prepared from zinc sulfide was based on hexagonal disks-like structures of ca. 10 mm. Electrical measurements proved the efficiency of the ZnO films as ozone gas sensors at room temperature under blue light irradiation, displaying good gas sensing characteristics, such as a fast response (less than 25 s) and a short recovery time (less than 60 s) at a low ozone level of 80 ppb. On the other hand, the ZnO film obtained from sulfide exhibited a better gas sensing performance, with a faster response ( of ca.18.8 s) and a shorter recovery time of ca. 5.7 s, compared to ZnO films obtained from nitrate and acetate. These results point out that the zinc precursor becomes a key parameter to control of microstructural properties as well as the sensitive room-temperature ozone sensing performance under blue light irradiation of ZnO thick films obtained via hydrothermal method.
9:00 AM - GG6.05
Electrical VOCs Detection Using Poly(3-alkylthiophenes) with Different Side-Chain Lengths
Edilene Assuncao da Silva 1 Vinicius Jesse Rodrigues de Oliveira 1 Maria Luisa Braunger 1 Clarissa de Almeida Olivati 1
1UNESP Presidente Prudente BrazilShow Abstract
The polythiophenes can act as sensor materials of volatile organic compounds (VOCs) [1, 2], these sensors have a high demand for many applications such as environment monitoring and homeland security . Langmuir-Blodgett (LB) technique was employed to produce the polymeric thin films, since it provides organized molecular architecture at nanoscale level . We have mixed, amphiphilic molecules (stearic acid - SA) to poly(3-alkylthiophenes) (P3ATs): poly(3-butylthiophene), poly(3-hexylthiophene) and poly(3-octylthiophene), in order to improve deposition via Langmuir-Blodgett technique. The solutions of P3ATs/SA were fabricated with 43 molecular percentage of stearic acid that was chosen, among other films with different molecular percentages, due to good quality films and high conductivity presented. The mixed LB films were fabricated using a Langmuir trough model KSV 5000 and it was observed the deposition parameters. Film growth in hydrophobic glass was supervised using the UV-Visible optical absorption. Film morphology and roughness were analyzed through Atomic Force Microscopy. Electrical measurements, current versus voltage (I vs. V), and current versus time (I vs. t) were carried out in the IDE using Keithley 238 source-measure unit. In order to characterize the sensor behavior it was measured the current versus time with a fixed applied voltage of 5V on the presence of the VOCs: toluene, dichloromethane and tetrahydrofuran in dynamic flow, dragged by nitrogen. The electrical measurements were performed using the parallel contact that was obtained by depositing P3ATs/SA LB film on interdigitated electrodes (IDE). Thin films showed, in current versus time (I vs. t) curve, sensibility to the VOCs, with a decrease in the current value. Despite the incomplete reversibility of the process, sensors can be used several times. Even after a film have detected a VOC, the same film can detect different VOCs.
We acknowledge support from CAPES, FAPESP, CNPQ/INEO and LNLS.
 S. Ozawa et al. Journal of Nanoscience and Nanotechnology, 14, 9, 6624-6631 (2014).
 B. Li et al, Sensors and Actuators B, 123, 651 - 660 (2007).
 H. Kim and G Kwak. Macromolecules, 902-904 (2009).
 G. C. Ferreira et al. Synthetic Metals, 194, 65-70 (2014).
9:00 AM - GG6.06
Preparation, Characterization and Dielectric Properties of Na-Doped CaCu3Ti4O12 Ceramics
Leonardo Arruda 1 Andre Luis Boaventura 1 Eduardo Antonelli 1
1UNIFESP - Universidade Federal de Samp;#227;o Paulo Samp;#227;o Jose dos Campos BrazilShow Abstract
Ferroelectric materials have been widely used to fabricate capacitors. Nevertheless, their dielectric properties are generally closely related to the spontaneous polarization and phase transition, with resulted in a large variation in capacitance and dielectric loss at the Curie temperature, as well as fatigue and aging problem at an alternating electric field. Unusual cubic perovskite like CaCu3Ti4O12 (CCTO) has drawn a lot of attention, because revealed an extraordinarily high dielectric constant at room temperature. Compared with other compounds, CCTO possesses much higher permittivity. There are some hypotheses to explain the origin of the giant dielectric constant in CCTO, mainly including the extrinsic and intrinsic factors. Unfortunately, the high dielectric loss hampers a practical application. In this investigation, we propose to prepare and study the CCTO doped with Na aiming to reduce the dielectric loss. CCTO was prepared by the traditional solid-state reaction technique using starting materials of CaCO3, CuO and TiO2 reagents. After homogenization for 6h, the mixtures were calcined at 950oC for 10h. The powders were then ball-milled for 2h into fine powders, compacted into disk-shaped samples and then sintered at 1050oC for 6h. The phase and microstructure developments were followed by X-ray diffraction (XRD) using a Rigaku Ultima IV diffractometer (with a monochromatic CuKα radiation, lambda;=1.5406Å) and scanning electron microscopy (FEI), respectively. Electrical measurements were carried out with a Solartron SI 1260 impedance/gain-phase analyzer over a wide temperature range from 25 to 200oC. No phase transition is observed in the studied temperature. Dielectric constant and dielectric loss decrease with the increase of the Na content.
9:00 AM - GG6.07
Influence of Synthesis and Sintering Parameters on Structure and Phase Transitions of Ba0.77Ca0.23TiO3 - BaTi0.85Zr0.15O3 50/50 Ceramics
Renato Boschilia Junior 1 Andre Luis Boaventura 1 Antonio Carlos Hernandes 2 Eduardo Antonelli 1
1UNIFESP - Universidade Federal de Samp;#227;o Paulo Samp;#227;o Jose dos Campos Brazil2USP - Universidade de Samp;#227;o Paulo Samp;#227;o Carlos BrazilShow Abstract
The solid solutions based on (1-x)Ba(Ti1-xZrx)O3 - (x)BayCa1-yTiO3 (BZT-BCT) have attracted a significant research interest due to their high piezoelectric coefficients. Although in a small temperature range, some compounds presents piezoelectric coefficients values that exceed even the d33 of soft PZT. Nevertheless, the Influence of synthesis and sintering parameters on structure and phase transitions in these “pseudo binary” materials were not completely studied. Therefore, in the present work, ceramics of (0.5)BaTi0.85Zr0.15O3 (BTZ) - (0.5)Ba0.77Ca0.23TiO3 (BCT) (BCT-BZT) has been prepared by the solid state reaction of BZT and BCT compounds. To complete our study, samples with the nominal formulation Ba0.885Ca0.115Ti0.925Zr0.075O3 (BCZT) were prepared. The powders were individually calcined at 1200oC for 2h and then mixed in the proportion of 50/50, ball-milled for 12h into fine powders, compacted into disk-shaped samples and then sintered at 1320oC for 1min/2h/10h and at 1270oC for 1 min. The final density of each sintered specimen was determined by the Archimedes method. The BZT/BCT phase and microstructure developments were followed by X-ray diffraction (XRD) using a Rigaku Geigerflex diffractometer (with a monochromatic CuKα radiation, lambda;=1.5406Å) and optical microscopy (Zeiss AX10), respectively. Grain size of the ceramics was evaluated by the intercept method. Electrical measurements were carried out with a Solartron SI 1260 impedance/gain-phase analyzer over a wide temperature range from 25 to 200oC. The dielectric spectra are characterized by dielectric peaks that correspond to the ferroelectric-to-paraelectric phase transitions. In particular, there was observed that the two preparation methods results in different structural phase transitions with the temperature. Furthermore, the sintering temperature and time affect the phase transitions, microstructure and the dielectric properties of BCT-BZT ceramics. The conclusion is that the preparation methodology, sintering temperature and time has influence in the competition between the ions to occupy the same crystallographic site, with leads to compositional fluctuations of different micro-regions in the material.
9:00 AM - GG6.08
Carbon Monoxide Gas Sensor on Silicon-on-Insulator Integrated System Capable of Working under Harsh Environmental Conditions
Cristian Fabrega 1 Julian Gardner 2 Zoltan Racz 2 Florin Udrea 3 4 Tracy Wothrespoon 5 Joan Ramon Morante 1 6
1IREC Sant Adria de besos Spain2University of Warwick Coventry United Kingdom3Cambridge University Cambridge United Kingdom4CMOS Ssensor Cambridge United Kingdom5Micorsemi Monmouthshire United Kingdom6UB Barcelona SpainShow Abstract
Metal oxides are a candidate for active material adequate for low -cost & high- mass-production of gas sensors. After many options, integrated sensor devices based on silicon base platform become the more feasible and reliable technology only limited but the range of available temperature excursion although, nowadays, it can be overcome using SOI based platforms which could work up to 6000C. As both, active material and sensor platform, are able to operate at high temperature, place this technology in a very good position for its application under harsh enviroments, such as boilers.
In this work, we present an innovatibe CMOS-compatible, Silicon-on-insulator (SOI) integrated smart microsensor system capable of measuring multiple targets under harsh environmental conditions.
As part of this system, we will discuss around a CO sensor based on tin oxide thin films deposited by Pulsed Laser Deposition.
Due to the small effective area of the platform, 200 microns diameter, one of the stronger drawbacks is the availability of techniques for such localized deposition of sensing material. Although different methods have already been proposed as inkjet, sputtering, localized CVD, etc. They have some drawbacks concerning, respectively, to reproducibility, material stoichiometry control or strong requirement on ambient and platform conditions.
9:00 AM - GG6.09
Electrical Stability of Titanium Nitride Thin Films at Elevated Temperature Deposited by Reactive Magnetron Sputtering
Mathias Hausladen 1 Kasper Thilsing-Hansen 1 Nis Dam Madsen 1 Serguei Chiriaev 1 Jakob Kjelstrup-Hansen 1
1University of Southern Denmark Sonderborg DenmarkShow Abstract
Thin film resistors subjected to harsh conditions such as high temperature often exhibit a drift in resistivity. This drift will deteriorate the performance of devices relying on stable resistivity such as strain gauges. In this work, the electrical stability of titanium nitride thin films deposited using reactive sputtering has been investigated. The depositions were carried out in a N2/ Ar atmosphere from a titanium target onto polished glass substrates that were not intentionally heated. The effect of three parameters on the electrical stability was studied: deposition pressure, nitrogen flow and target power. The resistivity was measured using electrical 4-point measurements on two sets of samples. The first set was used to study the stability at room temperature while the second set was used to study the stability at 200°C for up to 350 hours. Additional substrates for further analysis of the films were included in each deposition.
The deposition pressure was found to have the most dramatic impact on the film stability. The film deposited at the highest pressure (0.5 Pa) was found to be very unstable even at room temperature. As the pressure was decreased the stability was drastically improved. Furthermore, a significant increase in the X-ray diffraction (XRD) peak intensities was observed indicating an increased crystallinity of the films. Cross sectional scanning electron microscopy images showed a more dense columnar film structure of the films deposited at low pressures while the films deposited at higher pressures appeared more porous. The increased density of films deposited at low pressure was verified by direct measurement of the film masses using a high precision micro scale. Energy-dispersive X-ray spectroscopy measurements showed large amounts of oxygen in the films deposited at higher pressures despite no oxygen being added during deposition. This indicates that oxygen diffuses deeper into the more porous films after the deposition process.
The variation of nitrogen flow was done from the metallic target mode to the poisoned target mode at constant pressure. The films deposited in the metallic and poisoned modes were found to be stable at 200°C with a resistivity drift below 2 % after an initial relaxation time of 50 hours. The films deposited at intermediate nitrogen flows were not stable at 200°C showing a continuing increasing trend in the film resistance. Furthermore, the XRD spectra showed a predominant (111) texture for the unstable films. The effect of target power on film stability was also investigated. It was generally found that the films made in the region in-between the metallic and poisoned target modes yielded unstable films at 200°C.
9:00 AM - GG6.10
Novel Co3O4 Nanorod Arrays Based Gas Sensors
Zhen Wen 1 Liping Zhu 1
1Zhejiang University Hangzhou ChinaShow Abstract
Novel Co3O4 nanostructure arrays with rhombus-shaped and needle-like morphologies have been prepared by using urea and hexamethylenetetramine as hydrolysis agents through a facile fluoride-assisted hydrothermal method, respectively. The precursor Co(CO3)0.5(OH)middot;0.11H2O or Co(OH)F plays a crucial role in the formation of needle-like or rhombic arrays. The as-prepared precursor can be further thermally converted to porous Co3O4 arrays without significantly altering the one-dimensional morphology. Both types of the Co3O4 nanostructure arrays can directly serve as gas sensors without complicated fabrication process, owing to the direct growth on the substrates, good ohmic contact with the electrodes and intensive contact with the substrates. The Co3O4 nanostructure arrays based gas sensors showed high-performance of ethanol detection. The highest sensitivity of rhombus-shaped and needle-like Co3O4 morphologies reached 30.4 and 89.6 for 100 ppm ethanol vapor and the optimal working temperature was as low as 160oC and 130oC, respectively. Meanwhile, both types of the sensors exhibited good response/recovery kinetics, outstanding selectivity and good reproducibility. The high ethanol gas sensing performance of the Co3O4 nanostructure arrays can be explained by a typical p-type behavior with the one-dimension structure, nano-porosity, quasi-single crystalline structure and open space. Higher sensitivity in nanostructure arrays with needle-like morphology than rhombus-shaped arrays can be mainly attributed to the different exposed crystal planes. We consider that the exposed planes simultaneously contain Co2+ and Co3+ on the surface are benefit for the gas-sensing properties.
9:00 AM - GG6.11
Highly Ionically Conducting Solid State Nanocomposite Polymer Membranes for Electrochemical Capacitor Applications
Yuxiang Wang 1 Danhao Ma 1 Kofi Adu 1 Clive Randall 1 Ramakrishnan Rajagopalan 1
1The Pennsylvania State University University Park USAShow Abstract
Proton conducting polyvinylalcohol based composite membranes were fabricated to be used as ionically conducting membranes for the development of flexible solid state electrochemical capacitors. Fillers such as silica nanoparticles were uniformly dispersed in polyvinyl alcohol/phosphoric acid mixture in order to improve the mechanical properties as well as increase the overall uptake of phosphoric acid. Effect of addition of silica on polymer properties were probed using impedance spectroscopy as well as other characterization tools that include transmission electron microscopy and infrared spectroscopy. It was shown that addition of phosphoric acid affects the crystallinity of the polymer and incorporation of silica facilitates the fabrication of freestanding solid state membranes as thin as 25mu;m. The effect of ionic conductivity over a wide range of temperature ranging from - 50 °C to 100 °C was also explored. Mechanism related to space charge conduction due to the addition of nanofillers was investigated. The fabricated membranes were then used to assemble all solid state stacked electrochemical capacitors with the help of flexible binder-free carbon nanotube electrodes.
9:00 AM - GG6.12
Highly Sensitive and Selective Detection of Acetone Using Porous Zn2SnO4 Nanofibers Functionalized with Graphene Oxide and Pd for Application in Exhaled Breath Gas Sensor
HeeJin Cho 1 Seon-Jin Choi 1 Sang-Joon Kim 1 Nam-Hoon Kim 1 Il-Doo Kim 1
1KAIST Daejeon Korea (the Republic of)Show Abstract
Zn2SnO4 has a cubic inverse spinel structure and has been attractive as a potential candidate for use in ultraviolet photo-detectors, electrodes for dye-sensitized solar cells, and gas sensors, due to its high electrical conductivity, high thermal stability, low absorption coefficient in the visible range, and high chemical sensitivity. Furthermore, low cost mass production of Zn2SnO4 nanofibers (NFs) can easily be achieved using the electrospinning method.
In this work, two efforts were made to enhance the selectivity and sensitivity of acetone detection by Zn2SnO4 NFs. First, we synthesized porous Zn2SnO4 NFs that had a high surface-to-volume ratio. The highly porous structure of these Zn2SnO4 NFs was formed via an in situ phase-separation between inorganic-metal precursor-rich regions and poly (vinyl acetate, PVAc) polymer-rich regions, during the electrospinning and following calcination steps. Second, we functionalized the Zn2SnO4 NFs with palladium (Pd) and graphene oxide (GO) to achieve better sensitivity and selectivity than pristine Zn2SnO4 NFs. The 1 wt% Pd-embedded, porous Zn2SnO4 NFs were fabricated by electrospinning, using a solution into which Pd was mixed as a form of salt with metal-precursor and PVAc-polymer in DMF. Then, the GO was uniformly functionalized with the 1 wt% Pd-embedded porous Zn2SnO4 NFs, to bring out the synergistic effects of the GO and Pd. The GO-Pd-functionalized porous Zn2SnO4 NFs showed vastly improved acetone detection capability, with sensitivity (Rs) of 125 at 5 ppm. This was 3.78-fold, 3.92-fold, and 6.78-fold better than the values achieved by pristine porous Zn2SnO4 NFs; 1 wt% Pd embedded porous Zn2SnO4 NFs; and GO functionalized with porous Zn2SnO4 NFs, respectively. We also confirmed that the new product was outstandingly selective for acetone, when compared to H2S (Rs=5) and toluene (Rs=6.5) in high humidity atmosphere (90 RH%). This condition is similar to exhaled human breath. This work suggests significant potential for precise acetone detection in exhaled breath using the optimized, GO-Pd-functionalized, porous Zn2SnO4 NFs.
9:00 AM - GG6.13
Well-Aligned SOMS Micro-Wires and Its Humidity Response
Kuei-Lin Chan 1 Min-Han Yang 1 Min-Chiao Tsai 1 I-Chun Chang 1 Ting-Ting Chen 1 Hsin-Tien Chiu 2 Chi-Young Lee 1
1National Tsing Hua University Hsinchu Taiwan2National Chiao Tung University Hsinchu TaiwanShow Abstract
Sandia Octahedral Molecular Sieves (SOMS) and well-aligned SOMS micro-wires with hydrophilic dangling bond on the surface show distinguished humidity response both in static and dynamic examinations. Sandia Octahedral Molecular Sieves (SOMS) wires were synthesized using niobium pentoxide as the precursor in concentrated sodium hydroxide solution. The electrophoresis method was further utilized to align the SOMS micro-wires on substrate. The static and dynamic humidity responses of SOMS and aligned SOMS wires were examined by I-V behaviors in RH0% ~ RH100%. The high sensitivity linear dependence relation between current/resistance response and relative humidity were observed. In I-RH diagram, the slopes are 0.06 with standard error 0.007 and 0.11 with standard error 0.012 for SOMS and aligned SOMS wires, respectively. In the dynamic measurement, changing of the humidity of detecting chamber were reached by turning on and off the valve connected the chamber and the humid gas (RH70%) storage tank and were examined by the I-t behaviors. The response time was 28~35 seconds and recovery time was 12~15 seconds. The sensitivity maintain 90% after more than 10 cycles in between RH0% and RH70%, which indicates the moisture detectors have good humidity response, recovery time and reproducibility. In summary, SOMS and aligned SOMS micro-wires with high sensitivity and quick response to moisture, can be produced easily through a nature-friendly mass production process, making them a prominent candidate for humidity detector.
9:00 AM - GG6.14
Intrinsically Safe, Sensitive and Low-Powered CO Micro-Sensor Based on Meso-Structured Low-Temperature CO Oxidation Catalyst
Gengnan Li 1 Liang Li 1
1East China University of Science and Technology Shanghai ChinaShow Abstract
With the rapid development of micro-electro-mechanical systems (MEMS), many micro-machining ways were well developed and used, which made the micromation, low power consumption and intelligence of sensors possible. Carbon monoxide, one of the most common and widely distributed air pollutants, is harmful to atmosphere and human health. During the development of MEMS CO catalytic combustion micro-sensor, it was found that the sensitivity and selectivity were all very low when traditional high temperature catalyst was used. Combustible gases other than CO also respond at that temperature. In order to solve above problem, highly stable low-temperature CO oxidation catalyst under ambient condition was developed and introduced into the structure of micro-sensor. The CO oxidation process could be carried out at relative low temperature and thus promote the selectivity effectively. In addition, the resulting product become intrinsically safe instead of explosion-proof security products as traditional catalytic combustion sensor be. On the other hand, the sensitive materials (CO oxidation catalyst) were fabricated into meso-structure. The loaded amount of catalyst and contacted area between CO and the catalyst will be greatly enhanced, and much higher sensitivity could be obtained. Here, we reported a facile self-assembly approaching using P123 as template and in-suit reduction process to obtain meso-structured Mn3O4 supported Pd catalyst. The resulting materials displayed large surface area and high dispersion of palladium species, and showed much enhanced catalytic activities and stability for low-temperature CO oxidation under ambient condition. Complete CO conversion could be achieved at as low as -10 oC over 5.3 wt% Pd loaded catalyst and the catalyst exhibited no detectable deactivation even after 30 hours of reaction at 35 oC when 4.0 vol% H2O was introduced into the feed gas. After applied on micro-heater chip, at the working temperature 80 oC, the intrinsically safe, sensitive and low-powered CO micro-sensor could be easily achieved.
GG4: Nanomaterials for Hig