Kornelius Nielsch Max-Planck-Institute of Microstructure Physics
Oliver Hayden IBM Research GmbH
Hirotaka Ihara Kumamoto University
Deli Wang University of California-San Diego
U1: Inorganic Nanotubes I
Tuesday PM, April 18, 2006
Room 2002 (Moscone West)
9:30 AM - U1.1
Fabrication of Inorganic Tubular Structures Using Lipid Nanotube as a Template in Aqueous Solution.
Ji Qingmin 1 , Iwaura Rika 1 , Kogiso Masaki 1 , Jung Jong Hwa 2 , Shimizu Toshimi 1 2 Show Abstract
1 Nanoarchitectonics Research Center (NARC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan, 2 CREST, Japan Science and Technology Agency (JST), Tsukuba, Ibaraki, Japan
The use of organic materials for the generation of inorganic materials with well-defined structures has received increasing attention over the last decade. Especially, the fabrication of tubular architectures with a nanometer-sized hollow cylinder is challenging from the viewpoint of their potential applications in natural science and materials science fields. Surfactant-mediated or organogel-templated fabrication provides a typical method as a wet process to form isolated tubular structures. However, surfactant-mediated fabrication always produces silica structures. Organogel-templated fabrication always occurs in organic solvents in the presence of only a small amount of water. Here we describe the aqueous sol-gel transcription from a lipid nanotube template into different inorganic nanotubes of silica, titania, tantalum oxide and vanadium oxide, which proceeds in water containing no solution catalysts. A secondary ammonium hydrochloride of a peptidic lipid proved to form nanotube structures by self-assembly in water. Using the self-assembled nanotube as a template, we carried out the sol-gel transcription to silica in the aqueous dispersion in the absence of solution catalysts. The gradual solidification to a gel phase, after adding TEOS, evidenced the occurrence of the sol-gel transcription. Transmission electron microscopy (TEM) image clearly indicated that the gel is composed of abundant nanotube assemblies with uniform size, i.e., 20-nm wall thickness, 200-nm inner diameters, and 10-30-μm tube lengths. After removal of the organic template by calcination, we obtained a replicated silica tube with a uniform shape and dimensions of 200-nm diameters and 8-nm wall thickness. Compared with silica precursors, titania, tantalum and vanadium precursors have higher reactivity to water or moisture. Therefore, the fabrication of well-defined transition metal oxide structures is generally carried out in organic solvents. However, by freezing the aqueous dispersion to form an iced lipid nanotube template, we succeeded in the sol-gel transcription to transition metal oxide nanotubes from the aqueous dispersion. We found that in this frozen state, the sol-gel reaction of the inorganic precursors has proceeded gradually. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray (EDX) analysis proved that the obtained nanotubes are composed of titania, tantalum oxide, or vanadium oxide respectively. Reference1.Q. Ji, R. Iwaura, M. Kogiso, J. H. Jung, K. Yoshida and T. Shimizu, Chem. Mater., 2004, 16, 250.2.Q. Ji and T. Shimizu, Chem. Commun., 2005, 4411.
9:45 AM - U1.2
Layer-by-layer Assembled Magnetic Polyelectrolyte Hollow Tubes.
Daeyeon Lee 1 , Robert Cohen 1 , Michael Rubner 2 Show Abstract
1 Chemical Engineering Department, MIT, Cambridge, Massachusetts, United States, 2 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Magnetic polyelectrolyte hollow tubes are prepared based on layer-by-layer (LbL) assembly of polyelectrolytes and iron oxide (Fe3O4) nanoparticles. Track-etched polycarbonate membranes were used as templates to assemble hollow tubes with poly(allylamine hydrochloride) (PAH) and sodium (polystyrene sulfonate) (PSS). Additional layers of PAH and 8 nm citrate-coated Fe3O4 nanoparticles were assembled in the interior of these tubes and then the membrane templates were dissolve to produce nanocomposite hollow tubes. The polyelectrolyte multilayers comprised of PAH and SPS were assembled at a high pH condition which allows a high concentration of free amine groups to be available after the assembly. This approach overcomes the problem of irreversible aggregation in creating colloidal hollow structures via LbL assembly which is often observed during LbL deposition of partially charged weak polyelectrolytes onto spherical particles. Scanning electron microscopy and transmission electron microscopy confirmed that nanocomposite hollow tubes were created successfully. Magnetic properties of the magnetic polyelectrolyte tubes were characterized by SQUID magnetometer, and the tubes retained the superparamagnetic properties of Fe3O4 nanoparticles. It is demonstrated that these nanocomposite hollow tubes can be utilized to separate and release anionic dye molecules triggered by changes in the pH condition of solutions. Also the availability of free amine groups within the tube walls allows for further chemistry such as metallization of hollow tubes via electroless plating.
10:00 AM - **U1.3
Metallic Nanorods and Their Use as Templates for Hollow Nanotubes.
Catherine Murphy 1 Show Abstract
1 Dept. of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, United States
Gold and silver nanorods can be made with controllable aspect ratios, by a seed-mediated growth procedure in water, at room temperature. The presence of a directing surfactant is critical for the production of anisotropic nanoparticles. The directing surfactant exists as a bilayer on the metal nanorod long faces. This can be displaced by polymerization reactions that yield soft shells, or hard shells (silica) around the nanorods. Subsequent dissolution of the inner metal core yields hollow nanotubes. Partial dissolution of the inner metal core yields "peas in a pod" structures which have potentially interesting optical properties.
10:30 AM - **U1.4
Molecular Design and Assembly of Mono- and Multicomponent Nanotubes and Tube-Encapsulated Nanowire Devices
Nina Kovtyukhova 1 , Tom Mallouk 1 Show Abstract
1 Chemistry, Penn State University, University Park, Pennsylvania, United States
This presentation summarizes our progress in the synthesis and characterization of inorganic and composite inorganic/organic nanotubes and wire-in-tube nanostructures, and considers perspectives of their application as building blocks for self-assembling logic and memory circuits. Our strategy is based on shaping established thin-film devices, such as p-n heterojunction and Schottky diodes, insulating layers, and thin film transistors, into tube-encapsulated nanowire structures. This has been achieved by combining template electrochemical synthesis with wet adsorption methods for making thin-film devices. We have recently demonstrated the applicability of two layer-by-layer assembly techniques to template membranes with cylindrical pores and to metal nanowire substrates [1-4]. A variety of building blocks, such as semiconductor particles, short individual single-walled carbon nanotubes, polymers, and molecular precursors, can be alternately adsorbed one-layer-at-a-time inside the membrane pores and/or around metal wires. Important advantages of this strategy are (i) the possibility of organizing chemically and geometrically different blocks within a single nanostructure, (ii) technologically simple, inexpensive and scaleable synthesis of relatively uniform nanowire devices with excellent control over their length and diameter, (iii) precise control over thickness of the electroactive tube-shell, which is easy achievable by varying the number of adsorption cycles and by washing between adsorption steps in order to remove weakly bound particles or molecules. Importantly, the electrical characteristics of the tube-encapsulated nanowire devices are similar to those of large area planar thin film devices. This means that molecular organic and nanoparticle components can be introduced into the wire-in-tube structures without qualitative changes in their electrical, and most probably, chemical properties. References1. N. I. Kovtyukhova et al. J. Phys. Chem. B, 2001, 105, 8762-8769.2. N. I. Kovtyukhova, T. E. Mallouk, T. S. Mayer, Adv.Mater. 2003, 15, No 10, 780-785.3. N.I. Kovtyukhova, B.K. Kelley, T.E. Mallouk, J. Am. Chem. Soc., 2004, 126, 12738-12739.4. N.I. Kovtyukhova, T.E. Mallouk, Adv. Mater. 2005, 17, 187-192.
11:30 AM - U1.5
Electrical Conductance of Stand-Alone Metal Oxide Nanotubes
Jiyoung Kim 1 , Bongki Lee 1 , Dongkyu Cha 1 , Moon Kim 1 , Sanghee Won 2 , HyunJung Shin 2 , Jaegab Lee 2 , MyungMo Sung 3 Show Abstract
1 Electrical Engineering, The Univ. of Texas at Dallas, Richardson, Texas, United States, 2 Advanced Materials Engineeering, Kookmin University, Seoul Korea (the Republic of), 3 Dept. of Chemistry, Kookmin University, Seoul Korea (the Republic of)
Low dimensional inorganic nanostructure materials, such as TiO2 tubes, have been attracted lots of attentions for a wide range of potential applications including nano-sensors and integrated systems. Unfortunately, there are only a few papers regarding the electrical conduction mechanism of the metal oxide nanotubes. In particular, it is expected to be observed unique quantum size effects in the oxide nanotubes because electrons should be confined in ultra-thin tube-wall. Localized electron status in the oxide tubes, which is an important factor to decide electronic conduction of the oxide, would be significantly different due to severe deformation of the lattice resulting from extremely large curvature of the tube. We, therefore, need to precisely control the geometrics of the nanotubes, such as wall-thickness, diameter and stacking layers. It has been successfully demonstrated that with atomic level accuracy metal oxide nanotubes have been made by a use of atomic layer deposition (ALD) on nano-templates with self-assembled monolayer (SAM) treatments. In addition, this vapor phase approach enhances uniformity, repeatability and variety of stacking materials and sequences of the tube-walls. Various metal oxide (TiO2, ZrO2 etc) nanotubes will be prepared with 20 – 200 nm of diameter and 5 – 20nm of wall-thickness. In this study, we fabricate devices of stand-alone nanotubes by direct patterning the probing pads inside of vacuum chamber of focused ion beam (FIB) system. We observe that TiO2 nanotubes with diameter of 200nm show Ohmic contacts with the Pt pads. I-V measurement shows that the current linearly increases as the voltage increases from 0 to 3.2 V. However, the TiO2 nanotubes show failure at 5.2 V and then completely break down at 6.2 V. It is confirmed by SEM that hard-breakdown occurs. The resistivity of TiO2 tube is roughly 1 ohm/cm which is much higher than that of stoichiometric TiO2 bulk. It is possibly due to reduction of oxide tube surface by electron and ion beams. Pt interconnections as well as pads are formed between the tube and e-beam patterned probing pad. The reduced oxide surface is expected to be activated to adsorb detecting chemical and biological species and to enhance modulating the conductance. The relation between tube materials and sensing species will be also evaluated in this project. In addition, metal-insulator transition (MIT) phenomena of TiOx nanotubes will be investigated related with their geometric factors (diameter and wall-thickness) which may affect significantly on interaction of electron and phonon due to non-uniform stress distribution in the tubes. We will comparatively study characteristics of the nano-devices fabricated by conventional E-beam lithography method. This research was supported by a grant (code #: M105KO010026-05K1501-02611) from 'Center for Nanostructured Materials Technology' under '21st Century Frontier R&D Programs' of the Ministry of Science and Technology, Korea
11:45 AM - U1.6
Synthesis and Electrochemical Properties of InVO4 Nanotube Arrays
Ying Wang 1 , Guozhong Cao 1 Show Abstract
1 Materials Science and Engineering, University of Washington, Seattle, Washington, United States
InVO4 belongs to the family of orthovanadates with attractive properties as Li intercalation electrodes, and thus has potential applications in lithium secondary batteries and electrochromic windows. A capillary-enforced template-based method is described for the preparation of InVO4 nanotube arrays. InVO4 sol was synthesized using the sol-gel route from vanadium oxoisopropoxide and indium nitrate with ethanol as the solvent. Nanotube arrays of InVO4 were prepared by filling the sol into pores of polycarbonate membranes and sintering at high temperatures. Nanotube arrays annealed at 500°C consist of mixed monoclinic (InVO4-I) and orthorhombic (InVO4-III) phases, while InVO4 nanotube arrays of pure orthorhombic phase are obtained by annealing at 600°C. The third type of InVO4 nanotube arrays (InVO4/acac) are obtained from the sol with the addition of acetylene acetone (acac) followed by sintering at 500°C. Scanning electron microscopy (SEM) characterizations indicate that the nanotubes are well-aligned, perpendicular to substrate surface, of 10 micron long and 200 nm in diameter. For comparison purposes, InVO4 films were prepared by drop casting from the same sol. Electrochemical measurements were carried out in a standard three-electrode cell with 1M-LiClO4/propylene carbonate as electrolyte and the samples were cycled between 0.4 and -2.8 V versus Ag/Ag+. Chronopotentiometry results reveal that InVO4 film electrode delivers a capacity around 560 mAh/g at the specific current of 100 mA/g, while all three types of nanotube arrays demonstrate higher capacity than the film does. Specifically, at the specific current of 100 mA/g, InVO4 nanotube arrays of pure orthorhombic phase and nanotube arrays of mixed monoclinic and orthorhombic phases have similar capacities around 610 mAh/g, and InVO4/acac nanotube arrays deliver the capacity of 725 mAh/g, the highest among the three, due to the amorphization in the crystalline structure. This difference of capacities between nanotube arrays and films is more pronounced at higher discharge rate, e.g. nanotube arrays can achieve five times higher capacity than films do at a specific current of 500 mA/g. Such enhanced lithium-ion intercalation properties are ascribed to the large surface area and short diffusion distance offered by nanostructures. In addition, nanotubes can operate as electrolyte-filled channels for faster transport of the ions to the intercalation sites. Therefore, InVO4 nanotube arrays are the promising candidates for the electrode materials in lithium batteries with high power density and charge/discharge rates, and in electrochromic window with fast switching rate.
12:00 PM - U1.7
Synthesis and Characterization of Ceria Oxide Nanotubes.
Wei-Qiang Han 1 , Lijun Wu 1 , Xianqin Wang 2 , Yimei Zhu 1 , Jose Rodriguez 2 Show Abstract
1 Center for Functional Nanomaterials, Brookhaven National Lab, Upton, New York, United States, 2 Department of Chemistry, Brookhaven National Laboratory, Upton, New York, United States
12:15 PM - U1.8
Metal Dichalcogenide Nanotubes from Single Source Precursors.
Bruce Parkinson 1 , Manashi Nath 1 , Anna Chick 1 , Shannon Riha 1 , David Seley 1 Show Abstract
1 Department of Chemistry, Colorado State University, Fort Collins, Colorado, United States
The formation of nanotubules and other nano-structures from layered metal dichalcogenides has been beautifully demonstrated by Tenne and other researchers . Most of the synthesis methods produce nanotubules in conjunction with other nano-structures such as fullerenes, nanoparticles, nanowires etc. Since one-dimensional nanostructures of these materials have a wide range of possible applications, it would be interesting to design synthesis methods that produce nanotubules or nanowires as the sole or major product. The use of a template-assisted synthesis along with a single source precursor seems to be a suitable choice for achieving this goal. We have successfully synthesized a variety of dichalcogenide nanotubules (MS2, M=Mo, W and Re) from single source precursors, such as the ammonium thiometallate, or molybdenum diethyldithiocarbamate complexes, decomposed inside the pores of an anodic aluminium oxide membrane. Since many diethyldithiocarbamate complexes vaporize or sublime at fairly low temperatures, this opens up a wide range of possible reaction schemes which can be designed to grow nanotubes by chemical vapor deposition (CVD) on substrates prepatterned with gold or other meal nanoparticles. The attachment of the metal tip to the semiconductor nano-stucture also provides new functionalities such as the formation of natural anchor points for forming designed architectures by self-assembly on suitable substrates or for wiring them into functional circuitry. Hence, we decomposed a molybdenum diethyldithiocarbamate complex inside the pores of an alumina membrane with or without previously coating with gold. The precursor was deposited inside the pores of the membrane by sublimation. High yield of nanotubes and nanowires were obtained by this method. The nanotubes obtained from bare alumina membranes were mostly open at one end, thin-walled and grew out in oriented clusters. The nanotubes and nanowires obtained from the Au-coated alumina membrane were uniformly tipped with the Au cluster at one end. The Au clusters were mostly spherical with diameters in the range of 70-100 nm while that of the MoS2 nanostructures were in the range of 40-80nm with lengths of few micrometers. Decomposition of the ammonium thiometallates inside the pores of bare alumina membrane yielded nanotubules with diameters in the range of 50-200nm. In some cases holey tubes were obtained where the nanotube walls contained several regularly spaced holes along the length of the tube. We are presently directing our efforts towards carrying out measurement of the electrical properties of individual nanotubes. References:1. R. Tenne, L. Margulis, M. Genut, G. Hodes,. Nature, 360, 1992, 444; R. Tenne, Angewandte Chem. Intl. Ed., 42, 2003, 5124.
12:30 PM - U1.9
Growth of Vertically Aligned Boron Nitride Nanotubes on Substrates.
Jiesheng Wang 1 , Ming Xie 1 , Vijaya Kayastha 1 , Yoke Khin Yap 1 , Zhiyong Fan 2 , Jia Lu 2 , Zhengwei Pan 3 , David Geohegan 3 Show Abstract
1 , Michigan Technological University, Houghton, Michigan, United States, 2 , University of California-Irvine, Irvine, California, United States, 3 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
High growth temperatures (>1100 °C), low production yield, and impurities have prevented research progress and applications of boron nitride nanotubes (BNNTs) in the past ten years. Here, we show that BNNTs can be grown on substrates at 600 °C . These BNNTs are vertically aligned on the substrate surface, constructed of high-order tubular structures, and can be used without purification. BNNTs are structurally similar to carbon nanotubes (CNTs) and exhibit extraordinary mechanical properties. BNNTs possess uniform electronic properties that are insensitive to their diameters and chiralities. Theoretically, their band gaps (~5eV) are tuneable and can even be eliminated by transverse electric fields through the giant dc Stark effect. In addition, BNNTs demonstrate high oxidation resistance up to 800 °C, excellent piezoelectricity, and present potential material for room temperature hydrogen storage. However, growing BNNTs is challenging. In the last ten years, BNNTs were grown by arc discharge, laser ablation, substitution reactions from carbon nanotubes, ball-milling, and chemical vapor deposition (CVD), at temperatures from 1100 to 3000 °C. These BNNTs were dominated by impurities including amorphous boron nitride (a-BN) powders and other solid-state by-products. It is impossible to use these techniques to directly grow BNNTs on substrates for device fabrication. We grow BNNTs directly on substrates at 600 °C by a plasma-enhanced pulsed-laser deposition (PE-PLD) technique. Scanning electron microscopy (SEM) indicates that multiple BNNTs grown from adjacent Fe catalyst particles tend to form vertical bundles. Long and straight tubular structures were detected by transmission electron microscopy (TEM). These BNNTs are found to have square-like cross-section caps, which are typical for high-quality BNNTs. Tunneling spectroscopy indicates that their band gap ranges from 4.4 to 4.9 eV. Details of these results and a phase selective growth mechanism will be discussed in the meeting.Y.K.Y acknowledges supports from the Michigan Tech Research Excellence Fund, Army Research Office (W911NF-04-1-0029), CNMS at ORNL, and NSF CAREER Award (0447555).. Yap et al., Bulletin of the American Physical Society Vol 50, No. 1, Part 2 (March 2005) page 1346-1347 paper W25 3.
U2: Inorganic Nanotubes II
Tuesday PM, April 18, 2006
Room 2002 (Moscone West)
2:30 PM - **U2.1
Synthesis and Transport Studies of Transition Metal Oxide Core-Shell Nanowires and Nanotubes.
Chongwu Zhou 1 Show Abstract
1 , University of Southern California, Los Angeles, California, United States
We will present a generic nonequilibrium synthesis technique to produce novel transition metal oxide (TMO) core-shell nanowires and nanotubes, including YBa2Cu3O6.66, La0.67Ca0.33MnO3, PbZr0.58Ti0.42O3 and Fe3O4. Key to our success is the growth of vertically aligned single-crystalline MgO nanowires, which worked as excellent templates for epitaxial deposition of the desired transition metal oxides and led to high-quality core-shell nanowires. Transport studies on ultrafine La0.67Ca0.33MnO3 nanowires have revealed the remarkable persistence of metal-insulator transition and magnetoresistance down to nanometer scale. In addition, we have also demonstrated a wet etching technique to selectively remove the inner cores of the core-shell nanowires and leave behind clean single crystalline Fe3O4 nanotubes. Intriguing magnetoresistance has been observed with these nanotubes at low and elevated temperatures. Our technique will enable various in-depth studies such as phase transition in nanoscale oxides and may pave the way for novel applications of these fascinating materials.
3:00 PM - **U2.2
Iridium Oxide Nanotubes as High Sensitivity Chemo/Biosensors ,
Fengyan Zhang 1 , Shaidi Dayeh 2 , Robert Barrowcliff 1 , Sheng-Teng Hsu 1 , Deli Wang 2 Show Abstract
1 PTL, sharp labs of america, Camas, Washington, United States, 2 Department of electrical and computer engineering, university of california at san diego, San Diego, California, United States
1D semiconductor nanowires and nanotubes have been extensively studied as very attractive and versatile building blocks for the ‘bottom-up’ assembly of electronic and photonic systems, a wide range of nanostructures, including group IV, III-V, and II-VI materials have been demonstrated reproducible fabrication of a number of nanodevices including field effect transistors, photodetectors, light-emitting-diodes, and sensors. Metallic nanowires could play a very important role as nanoscale interconnects but have been less studied. Herein we report the synthesis of Iridium oxide (IrO2) nanotubes MOCVD with (methycycpentadienyl-1,5-cyclooctadiene) iridium as the precursor. It was found that the IrO2 nanowires growth is self-mediated that have diameters of 150-180 nm and length of 2 microns. The diameter of nanotube and wall thickness are very uniform along the axial growth direction from SEM and LRTEM studies. HRTEM image and electron diffraction pattern reveal single crystal IrO2 nanotubes have rutile structure with the growth direction along <001>. The IrO2 nanotubes are metallic conductive with measured resistivity around 300 - 400 microohm-cm. The IrO2 nanotubes are biocompatible and the usage as pH sensor and biosensor will be discussed.
3:30 PM - **U2.3
VLS Nanowire Growth Dynamics and Vertical Nanowire Devices.
Erik Bakkers 1 , M. Borgstrom 1 , O. Wunnicke 1 , A. Helman 1 , W. van den Einden 1 , M. A. Verheijen 1 Show Abstract
1 Electronic Materials and Devices, Philips Research Laboratories, Eindhoven Netherlands
Semiconducting nanowires are one of the most promising materials for the monolithic integration of high-performance semiconductors with silicon technology. For the fabrication of optical or electrical devices, local variations in the electronic structure of the wire, such as hetero junctions, are required. Ultimate control over the growth rates of segmented nanowires is desired since the opto-electronic properties of the sections critically depend on their dimensions in the nanometer regime. We have studied the Vapor-Liquid-Solid (VLS) growth dynamics of GaP and GaAs in heterostructured GaP-GaAs nanowires. The wires containing multiple GaP-GaAs junctions were grown by the use of metal-organic vapor-phase-epitaxy (MOVPE) and the lengths of the individual sections were obtained from transmission electron microscopy (TEM). The wires have been grown on ‘inert’ SiO2 surfaces, such that material deposition at the substrate surface is suppressed. This enables to study the catalytic action of the metal particle. The growth kinetics have been studied as a function of temperature and the partial pressures of the precursors. We have also studied the competitive reaction, i.e. growth of a thin film on the sidewalls of the nanowires, which occurs at elevated temperatures and results in tapered nanowires. We were able to study this reaction in detail since the hetero structures offer a precise internal ‘time reference’, such that exposure times at specific positions on the wires could be accurately determined afterwards with TEM. In addition, we have grown III-V nanowires epitaxially on silicon substrates and fabricated basic vertical nanowire devices. Some first preliminary electrical characteristics of vertical gate-around field-effect transistors will be shown.
4:15 PM - U2.4
Coaxial ALD of High-κ Dielectrics and Metals on Functionalized SWNTs.
Damon Farmer 1 , Roy Gordon 2 Show Abstract
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Dept. of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Inherent deposition properties such as low temperature processing and sub-nanometer thickness precision makes atomic layer deposition (ALD) an ideal method for nondestructively covering single-walled carbon nanotubes (SWNTs) with very thin, uniform high-κ dielectrics and/or metals. The problem in using ALD for this purpose is that the SWNT surface is chemically inert to ALD precursor molecules, which eliminates the possibility of radially isotropic, coaxial deposition. Here, a gas-phase, physical functionalization technique has been used to make the SWNT surface chemically susceptible to ALD precursors. SWNTs are exposed to 50 alternating pulses of nitrogen dioxide (NO2) gas and trimethylaluminum (TMA) vapor. Electrically probing SWNTs during the functionalization procedure reveals that the desorption of NO2 from the SWNT surface is hindered by the presence of TMA. The result is that the nanotube surface is covered with a uniform monolayer that is stable at room temperature. The thickness of this coating appears to be self-limiting at a monolayer for up to 200 cycles. The stability of this monolayer is then reinforced by 0.5 nm of ALD Al2O3 deposited at 25°C, resulting in a uniform coating of aluminum oxide less than 1 nm thick. The resulting coated tube remains intact after heating to higher temperatures (200–300°C), at which temperatures it can be further coated with a variety of materials, including high-κ dielectrics (such as Al2O3, HfO2, or LaAlO3), and/or metals (such as WN, Ru, or Cu). The diameters of the resulting nanowires are highly uniform, and can be controlled to any predetermined thickness.
4:30 PM - U2.5
Atomic Layer Deposition of Ruthenium in Nanoporous Templates.
Mihaela Daub 1 , Mato Knez 1 , Kornelius Nielsch 1 , Ulrich Goesele 1 Show Abstract
1 , Max-Planck-Institute for Microstructure Physics, Halle Germany
Noble metals are often desirable in integrated circuits or in various microelectronic applications, like capacitor electrodes in random access memories or gate metal in future MOSFETs. In this context, atomic layer deposition is offering perfect control of the growth using self-limiting surface reactions, with precise film thickness and excellent conformability on high aspect ratio structures. Thin films of noble metals (e.g. Ru, Pd, Pt) deposited by atomic layer deposition (ALD) have already been produced in the past. However, in these cases, oxygen was used as the second precursor in the deposition process. We present highly conformal and uniform Ru nanotubes obtained from RuCp2 (Ruthenocene) and hydrogen as ALD precursors. The Ru deposition was performed onto the pore walls of self ordered or perfectly ordered porous alumina membranes with pore diameters ranging from 40 to 180 nm. The aspect ratio (pore length/diameter: 10-1000) and the physical properties of the tubes as a function of the deposition temperature and other parameters were investigated by means of SEM and TEM. Ru nanotubes were also obtained with ruthenocene and air as ALD precursors and their properties compared with the properties of Ru nanotubes using the metal precursor with hydrogen.Acknowledgement: This work was supported by the German Federal Ministry for Education and Research (BMBF), project number 03N8701.
4:45 PM - U2.6
Enhanced Field Emission and Morphology of Atomic Layer Deposition ZnO Coated Carbon Nanotubes.
Joshua Green 1 , Lifeng Dong 1 , Timothy Gutu 1 , John Conley 2 , Jun Jiao 1 , Yoshi Ono 2 Show Abstract
1 Department of Physics, Portland State University, Portland, Oregon, United States, 2 IC Process Technology Group, Sharp Labs of America, Camas, Washington, United States
Due to purge separation of precursor pulses and self limiting surface reactions, atomic layer deposition (ALD) offers highly conformal deposition, creating the potential for many interesting nanostructure coating applications. In this work, ALD was used to coat multiwall carbon nanotubes (CNTs) with a thin conformal layer of ZnO. Although scanning and transmission electron microscopy revealed no significant changes in the internal structure of the CNTs, annealing of the ZnO coated CNTs resulted in the agglomeration of ZnO into ball-shaped single crystalline nanoparticles attached to the sidewalls of the CNTs. CNTs are well known to be excellent field emitters. It was found that the electron field emission properties of these ZnO coated nanotubes are much improved over uncoated CNTs and over ZnO nanowires. The diameter of the ZnO nanoparticles is approximately equal to the diameter of the multiwall CNTs. It is proposed that the ZnO nanoparticles serve as additional emission sites, resulting in an effective geometric enhancement of the field emission properties and demonstrating how ALD can be used to engineer the surface properties of nanostructures.
5:00 PM - U2.7
Synthesis, Characterization and Physical Properties of Transition Metal Silicide Nanowires.
Song Jin 1 , Andrew Schmitt 1 , Lei Zhu 1 , Yipu Song 1 , Jeannine Szczech 1 Show Abstract
1 , University of Wisconsin-Madison, Madison, Wisconsin, United States
5:15 PM - U2.8
Molybdenum Sulfide as Electrochemical Ultracapacitors
Jia Mei Soon 1 , Kian Ping Loh 1 Show Abstract
1 Department of Chemistry, National University of Singapore, Singapore Singapore
Concerns over global warming issues and natural resources depletion have fueled current research in the direction of renewable energy sources over the last decade. Electrochemical ultracapacitors , , are ideal candidates for energy storage devices in high-power applications for storing electricity when it is available and retrieving when it is needed. Using the single source precursor Mo(IV)-tetrakis(diethylaminodithiocarbomate) we deposited nanoporous thin films and nanotubules of MoS2 via chemical vapor deposition. Portions of each specimen were fluorinated at room temperature using XeF2 to form a MoFx-MoS2 composite. The four samples, MoFx-MoS2 and MoS2 thin film; as well as MoFx-MoS2 and MoS2 nanotubules, were tested for their electrochemical ultracapacitance properties. The as-deposited MoS2 thin film exhibited good ultracapacitance properties of 8.0F/g. In spite of the larger surface area of the MoS2 nanotubules compared to the thin films, it is interesting to note that the ultracapacitance of the thin film is twice that of the nanotubules due to the large number of reactive basal edges on the nanoporous thin films. Fluorination significantly reduces the ultracapacitance of both nanoporous thin film and nanotubular MoS2 by two orders of magnitudes due to enhanced hydrophobicity of the surface after fluorination, as analyzed by rheology study. Deposition of RuO2 nanoparticles onto the non-fluorinated MoS2 thin film improves its ultracapacitance by more than two times while retaining the original morphology of the nanoporous MoS2 thin film.*author to whom correspondence should be addressed: firstname.lastname@example.org M. Nakayama, A. Tanaka, Y. Sato et al.; Langmuir 21, 5907 (2005) T-C Liu, W. G. Pell, B. E. Conway; J. Electrochem. Soc. 6, 1882 (1998) S. L. Roberson, D. Finello, R. F. Davis; J. Appl. Electrochem. 29, 75 (1999) H. Zhang, K. P. Loh, C. H. Sow et al.; Langmiur 20 (16), 6914 (2004)
5:30 PM - U2.9
Nanotubes in Low Temperature Spray Deposited Nanocrystalline HgSe: I thin films.
Ranga Rao Arnepalli 1 , Viresh Dutta 1 Show Abstract
1 Centre for Energy Studies, Indian Institute of Technology, Delhi, New Delhi, New Delhi, India
5:45 PM - U2.10
Modifying Magnetic Properties of Nanotubes by Doping with Magnetic and Nonmagnetic Elements.
Yuan Ping Feng 1 , Rongqin Wu 1 , Hui Pan 1 , Guowen Peng 1 , Jianyi Lin 1 , Alfred Huan 2 Show Abstract
1 Physics, National University of Singapore, Singapore Singapore, 2 , Nayang Technological University, Singapore Singapore
Carbon and other types of nanotubes have attracted much attention because of their potential applications. Physical properties of nanotubes, as well as other nanostructures, can be further modified by chemical binding of atoms, molecules or molecular groups. Our recent work on first principles studies of magnetic properties of functionalized carbon and other types of nanotubes will be presented. Effects of carbon doping of BN nanotubes, OH functionalization of carbon nanotube, and Mn-doping of B2O nanotubes on the magnetic properties of the nanotubes will be discussed. Carbon substitution for either boron or nitrogen in BN nanotubes was found to induce magnetization. Band structure calculation revealed a spin polarized, dispersionless band near the Fermi energy. The magnetization can be attributed to the carbon 2p electron. Magnetism was also found in OH-functionalized single-wall carbon nanotube, when two functional OH groups are close to each other. The magnetic moment increases with decreasing tube-tube distance. A possible mechanism for the magnetism of OH-functionalized SWCNT is the electron-electron interaction induced by the flat bands near the Fermi level. Manganese doping of single-wall B2O nanotube was also investigated. It was found that the bridge site above the axial B-B bond is the most energetically favorable site when the Mn atom is adsorbed outside the (3,0) B2O nanotube. The magnetic moment of the Mn-doped nanotube is similar to that of the free Mn atom. The atop oxygen site, however, is the most stable site if the Mn atom is inside the tube. In this case, the Mn atom is seven-coordinated and the nanotube is significantly distorted, leading to the largest binding energy among all adsorption sites and a smaller magnetic moment.
Kornelius Nielsch Max-Planck-Institute of Microstructure Physics
Oliver Hayden IBM Research GmbH
Hirotaka Ihara Kumamoto University
Deli Wang University of California-San Diego
U3: Fluidic Transport Through Tubes
Wednesday AM, April 19, 2006
Room 2002 (Moscone West)
9:00 AM - U3.1
Gated Chemical Transport and Enhance Flow through Carbon Nanotube Membranes
Bruce Hinds 1 , Mainnak Majumder 1 , Nitin Chopra 1 Show Abstract
1 Chemical and Materials Engineering, Univ. of Kentucky, Lexington, Kentucky, United States
A promising architecture for ion-channel mimetics is a composite membrane structure containing vertically aligned carbon nanotubes, with inner core diameters of 7 nm, passing across a polystyrene matrix film. Plasma oxidation during the fabrication process introduces carboxylic acid groups on the CNT tips that are modified using carbodiimide mediated coupling between carboxylic acid on the CNTs and accessible amine groups of the functional molecule. The entrances to CNT’s cores were thus functionalized with aliphatic amines of different lengths, charged dye molecule and an aliphatic amine elongated by spacers containing poly-peptides. The transport through the membrane of two differently sized but equally charged molecules, ruthenium bi-pyridine [Ru-(bipy)3+2] and methyl viologen [MV+2], was studied in a U-tube permeation cell with flux quantified by UV-vis Spectroscopy. Relative selectivity of the permeates was seen to vary from 1.9 to 3.6 as a function of tip-functionalization chemistry. Anionic charged functional groups are seen to sharply increase flux of cationic permeates. This effect is reduced at higher solution ionic strength consistent with shorter Debye screening length. Using a hindered diffusion to model observed selectivities was consistent only with a geometry of only CNT tip functionalization, not along the length of CNT core. Biologically active desthiobiotin was also shown to be reversibly coordinated to stretavidin, showing a reduction in ionic flux through CNT. Pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 ORDERS OF MAGNITUDE FASTER than conventional Newtonian flow. There are also experimental indications of the ordering of polar solvents inside CNT pores. Dual functional CNTs (that is different functionality at each end of a CNT) have also been produced by reacting each side of the membrane with different functional solution, then subsequent removal of polymer matrix.
9:15 AM - U3.2
Fast Mass Transport Through Sub-2nm Carbon Nanotubes
Jason Holt 1 , Hyung Gyu Park 1 , Aleksandr Noy 1 , Olgica Bakajin 1 Show Abstract
1 Biosecurity and Nanosciences Laboratory, Lawrence Livermore National Laboratory, Livermore, California, United States
We report gas and water flow measurements through microfabricated membranes with sub-2 nm aligned carbon nanotubes as pores. The measured gas flow exceeds predictions of the Knudsen diffusion model by at least an order of magnitude. The measured water flow rate exceeds values calculated from continuum hydrodynamics models by two to three orders of magnitude and agrees with flow rates extrapolated from molecular dynamics simulations. The gas and water permeabilities of these nanotube-based membranes are orders of magnitude higher than those of commercial polycarbonate membranes, despite having an order of magnitude smaller pore size. These properties should enable more energy-efficient nanoscale filtration, as well as fundamental studies of mass transport in confined environments.
9:30 AM - U3.3
Atomistic Simulations on Transport of Water inside Nanotubes of Varying Hydrophobicity and Size.
Daejoong Kim 1 , Artit Wangperawong 1 , Eric Darve 1 Show Abstract
1 Mechanical Engineering, Stanford University, Stanford, California, United States
9:45 AM - U3.4
Inorganic Nanotube Nanofluidics for Single Molecule Detection and Manipulation
Rong Fan 1 , Rohit Karnik 2 , Arun Majumdar 2 3 , Peidong Yang 2 3 Show Abstract
1 Department of Chemistry, University of California at Berkeley, Berkeley, California, United States, 2 Department of Mechanical Engineering, University of California, Berkeley, California, United States, 3 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Inorganic nanotubes represent a new class of one-dimensional nanostructures towards multi-functionalities and complexities. A nanowire-template approach has been developed to synthesize high quality inorganic nanotubes that are mechanically robust and free of pinholes. Vertically aligned silica nanotube arrays were synthesized through a controlled oxidation-etching approach using silicon nanowires as templates. These nanotubes were integrated with microfluidic channels to create nanofluidic systems for single DNA molecule sensing. These nanofluidic devices are unique in their high aspect ratio and exhibit different DNA translocation mechanisms from biological nanochannels, e.g. ion channel proteins. Transient changes of ionic current indicate single molecule translocation events. Ionic current crossover was observed with the change of the buffer solution ionic strength, which is indicative of the interplay of electrostatic effect and geometric effect. Furthermore, single molecule manipulation and controlled delivery can be realized in nanotube nanofluidic systems assisted with external electrostatic control. Moreover, complex nanofluidic circuits have been created in a custom-designed fashion through a self-assembled VLS growth process. These multiplexed nanofluidic circuits can be used to simultaneously perform genomic-sized polynucleotide sorting, and trapping, manipulating or delivering individual biomolecules. This work represents the first time that inorganic nanotubes were utilized as functional components in complex nanofluidic systems. These systems represent a novel platform for studying single molecule biology and biophysics, and presage their potential in the large-scale integration of nanofluidic systems.
10:00 AM - **U3.5
Roger Koeppe 1 Show Abstract
1 Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, United States
Gramicidin channels are mini-proteins which catalyze the passive transport of monovalent cations across lipid bilayer membranes at rates approaching 10 million ions per second. Two tryptophan-rich subunits associate by means of transbilayer dimerization to form the conducting channels. Respective subunits are tethered to the bilayer/solution interface through hydrogen bonds that involve the indole NH groups with water and the phospholipid backbone. The channel’s permeability characteristics are particularly well-defined: ions and water move through a pore whose wall is formed by the peptide backbone; gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. The channel structure is known at atomic resolution. Given the plethora of available experimental information for both the wild-type and amino-acid-substituted channels, gramicidin channels provide important insights into the microphysics of ion permeation through bilayer-spanning channels.
10:30 AM - **U3.6
Synthetic Multifunctional Pores.
Stefan Matile 1 Show Abstract
1 Department of Organic Chemistry, University of Geneva, Geneva Switzerland
The general objective of the concept of synthetic multifunctional pores is to combine molecular translocation with molecular recognition and catalysis . Todays synthetic multifunctional pores are rigid-rod beta-barrels, i.e., barrel-stave supramolecules composed of para-oligophenyls as “staves” and beta-sheets as “hoops.” Design strategies for the construction of pores that either close (blockage) or, more recently, open response to chemical stimulation are available (ligand-gating) , voltage-sensitive rigid-rod push-pull beta-barrels as well . Recent highlights concerning the practical application of synthetic multifunctional pores concern catalysis as well as multicomponent sensing in complex matrixes. An illustrative and timely example for the latter topic is sugar sensing in soft drinks, with synthetic multifunctional pores serving as “universal” transducers of chemical reactions into color . Beyond the classical rigid-rod beta-barrel [1-3], transmembrane rigid-rod π-stack architecture will be introduced for the creation of ligand-gated ion channels  as well as for ligand- and voltage-sensitive photoinduced electron transfer across bilayer membranes.1. Sakai N., Mareda J. and Matile S., Acc. Chem. Res., 38, 79-87 (2005).2. Gorteau V., Perret F., Bollot G., Mareda J., Lazar A.N., Coleman A.W., Tran D.H., Sakai N. and Matile S., J. Am. Chem. Soc., 126, 13592-13593 (2004).3. Litvinchuk S., Sordé N. and Matile S. J. Am. Chem. Soc., 127, 9316-9317 (2005).4. Talukdar P., Bollot G., Mareda J., Sakai N. and Matile S. J. Am. Chem. Soc., 127, 6528-6529 (2005).Acknowledgement: This research is supported by the Swiss NSF.
U4: Bioinspired and Organic Tubes I
Wednesday PM, April 19, 2006
Room 2002 (Moscone West)
11:30 AM - **U4.1
Self-Assembly of Biomimetic and Bioactive Nanostructures
Samuel Stupp 1 Show Abstract
1 Materials Science & Engineering, Department of Chemistry, and Feinberg School of Medicine, Northwestern University, Evanston, Illinois, United States
Self-assembly directed by covalent structure and environment generates the functionally sophisticated supramolecular structures of biology. A contemporary challenge is to achieve this type of self-assembly with synthetic molecules to create organic objects that emulate proteins. This lecture describes the self- assembly of peptide-based molecules into high molar mass one-dimensional nanostructures that can serve as bioactive nanostructures to signal cells or to sense the presence of biological analytes. One form of these nanostructures involves the self-assembly of peptide amphiphiles on carbon nanotubes.
12:00 PM - **U4.2
Tubular Assemblies Prepared from Cyclic Peptides Composed of β-Amino Acids.
Shunsaku Kimura 1 Show Abstract
1 Dept. of Material Chemistry, Kyoto University, Kyoto Japan
Cyclic tri- and tetra-β-peptides (CTPs) having cyclohexane or pyranose rings were synthesized. Various spectroscopic measurements and computational geometry optimization revealed that these compounds take planer conformation with all amide groups vertically orientated to the ring plane in one direction. The CTP with cyclohexane rings forms a regular rod-like structure in solution as revealed by transmission electron microscopy, and the electron diffraction analysis showed that the rod is composed of tubular assemblies formed by intermolecular hydrogen bondings among the amide groups. The CTP with pyranose rings also forms a tubular assembly. Notably, the surface of the assembly provides binding sites for lectins.
12:30 PM - **U4.3
Conformation-Controlled Inversion, Propagation, and Memory of Supramolecular Chirality
Hicham Fenniri 1 2 Show Abstract
1 National Institute for Nanotechnology, University of Alberta, Edmonton, Alberta, Canada, 2 Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
A remarkable level of control over supramolecular chirality (SC) has been achieved under the effect of an asymmetric molecular input using the sergeant and soldier effect, molecular recognition, chiral memory, circularly polarized light, chiral vortex forces, redox- and photo-switches, and photoinduced electron transfer. The ability to control SC allowed for the design of sensors, chiral cholesteric phases, catalysts, asymmetric synthesis of materials with electromagnetic and optoelectronic applications, information storage, display systems and photochromic materials, and for the design of materials with unique chiral light-emitting and non-linear optical properties. However, for SC inversion to occur in both natural and synthetic systems, the symmetry of the molecular input must also be inverted. Here we introduce supramolecular atropisomerism (chiromerism) as a novel property of supramolecular systems whose chiroptical properties can be reversibly and controllably driven in mirror-image directions upon self-assembly of conformers of a single, homochiral molecular module. Extensive physical and computational studies led us to the conclusion that the solvation free energy of the self-assembling module determines its conformational states, which in turn control the SC output. We have also shown that the resulting supramolecular atropisomers (chiromers) are not only thermodynamically stable, but they can also memorize and propagate their chirality in an achiral environment. These results underscore the fundamental role of achiral environmental chemical/physical factors in determining SC, and establish that absolute molecular chirality does not necessarily determine SC. SC should thus be viewed as the result of a supramolecular chain reaction whose pathways could be rationalized by invoking the Curtin-Hammett principle in the context of supramolecular systems.
U5: Bioinspired and Organic Tubes II
Wednesday PM, April 19, 2006
Room 2002 (Moscone West)
2:30 PM - **U5.1
Supramolecular Nanotube Hosts for Encapsulation of 10-nm-Scale Objects.
Toshimi Shimizu 1 2 Show Abstract
1 Nanoarchitectonics Research Center (NARC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan, 2 SORST, Japan Science and Technology Corporation (JST), Tsukuba, Ibaraki, Japan
Lipid nanotubes (LNTs) with 10-100-nm-scale hollow cylinders have been again receiving much interest due to their resemblance to multi-wall carbon nanotubes in size dimensions, their unique shapes, and prospective technological applications. Though a limited number of synthetic lipid molecules have been well documented to self-assemble into tubular structures, there have been no definitive guiding principles to manipulate the nanotube morphologies. Discrete, organic, hollow cylinder architectures are also of great interest in nanomaterials science due to the continuing interest in nano-space-specific fundamental phenomena. Here we describe chiral self-assembly of synthetic glycolipid molecules into uniform hollow cylinder structures in approximately 100% yields. Optimization of the introduction position of a cis-double bond in the unsaturated hydrocarbon chains enabled us to get such uniform nanotubes among a series of glucopyranosylamide lipids. In addition, we have succeeded in the confined organization of gold nanocrystals or ferritin at room temperature by filling a vacant glycolipid nanotube hollow cylinder with aqueous solutions of hydrogen tetrachloroaurate or ferritin, respectively.[4,5] The lipid N-(11-cis-octadecenoyl)-beta-D-glucopyranosylamine 1 proved to produce the nanotubes with the narrowest distribution of outer diameters (av. = 200 nm, s.d. = 23 nm) among several lipid homologues synthesized. To get a one-dimensional vacant LNT hollow, we removed the water filled in the LNT hollow cylinder of 1. An aqueous solution of hydrogen tetrachloroaurate (III) was immersed into the LNT hollow cylinder by capillary action and the aurate anion was then photochemically reduced to Au(0) by UV irradiation in the confined nanospace. We confirmed that the present LNTs can keep their tubular structures without any destruction even after the lyophilization process. TEM images revealed that the gold nanocrystals of 3-10 nm well generated in the one-dimensional nano-space of the LNT. The EDX spectroscopy and the SAED pattern revealed the exact presence of Au nanocrystals with a fcc phase in the LNT. By applying the similar methodology, we next tried to encapsulate ferritin (12 nm) within the LNT from 1. The TEM and EDX revealed that ferritins are well encapsulated in the hollow cylinder. We were able to see ferrihydrite cores as black dots. Thus, the hollow cylinder of the LNT from 1 provides an effective, supramolecular nanotube host for the confined organization of 10-nm-scale objects.References a) T. Shimizu et al., Chem. Rev. 105, 1401 (2005). b) J.M. Schnur, Science, 262, 1669 (1993).  a) G. John et al., Adv. Mater., 3, 715 (2001). b) J.H. Jung et al., J. Am. Chem. Soc., 124, 10674 (2002). S. Kamiya et al., Langmuir, 21, 743 (2005). a) B. Yang et al., Chem. Commun., 500 (2004). b) B. Yang et al., Chem. Mater., 16, 2826 (2004). H. Yui et al., Chem. Lett., 34, 232 (2005).
3:00 PM - U5.2
Self-Assembled Lipid Tubules: Synthesis, Characterization, and Ordered Arrays.
Yue Zhao 1 , Nidhi Mahajan 1 , Jiyu Fang 1 Show Abstract
1 , University of Central Florida, Orlando, Florida, United States
The rolling of lipid bilayer sheets into hollow cylindrical tubules have emerged as a group of interesting supramolecular nanostructures. The hollow cylindrical shape and the crystalline molecular order of the bilayer walls make lipid tubules attractive as a template for the synthesis of inorganic materials, a substrate for the helical crystallization of proteins, and a controlled release system for drug deliver. Here, we image the molecular orientation order in the lipid tubules using liquid crystals as an optical amplification probe. We find that the organization of the molecular tilt azimuth in the lipid tubules can induce an azimuthal orientation in the liquid crystals. A modulated tilt state of the lipid tubules is observed after liquid-crystal optical amplification. Atomic force microscopy studies show that the modulated tilt can induce nanoscale ripples with a periodicity of ~ 200nm for the tubules with the diameter in the range from 200 nm to 650 nm. The angle of the ripples with respect to the equator of the tubule shows a bimodal distribution with centers at ~ 28° and ~ 5 °. We develop a method that combing surface patterning and moving contact line to produce 2-D ordered arrays of parallel aligned lipid tubules on substrates. The patterned and aligned tubules are used as templates for synthesizing silica films with specific morphologies and patternes. References:1. Y. Zhao, N. Mahajan, R. Lu, J. Y. Fang, “Liquid-Crystal Imaging of Molecular-Tilt Organization in Self-Assembled Tubules of Chiral Phospholipids” Proceedings of the National Academy of Sciences USA 2005, 102, 7438. 2. N. Mahajan, J. Y. Fang, “Two-Dimensional Ordered Arrays of Aligned Lipid Tubules on Substrates with microfluidic networks” Langmuir 2005, 21, 3153.
3:15 PM - U5.3
Self-assembled Lipid Nanotube: Inner Diameter and Surface Control by Using Wwedge-shaped Bipolar Amphiphiles.
Mitsutoshi Masuda 1 2 , Toshimi Shimizu 1 2 Show Abstract
1 Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, 2 CREST, Japan Science and Technology Agency, Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan
Lipid nanotubes with different inner- and outer membrane surfaces are intriguing nano-architectures applicable to the specific modification of internal and external surfaces, selective filling of nanomaterials into the hollow cylinder , controlled release, and creation of templates for the fabrication of inorganic nanomaterials . The most direct way to construct an unsymmetrical lipid membrane is to make use of the asymmetry of heteroditopic 1,omega-bipolar amphiphiles having headgroups differing in size or properties, that is, “unsymmetrical bolaamphiphiles”. The wedge-shape of the lipids also affords us to control inner diameter of the self-assembled nanotubes. So far, there have been no reliable approaches for controlling their diameters until now. Here we would like to present the lipid nanotubes self-assembled from the unsymmetrical bolaamphiphile, and control of the inner diameter and inner/outer surfaces of them .Unsymmetrical bolaamphiphiles 1(n) (n = 12, 14, 16, 18, and 20) self-assembled in water to form lipid nano- and microtubes. The nanotubes were separated by centrifugation and examined by TEM and X-ray diffraction (XRD) to study the molecular packing within the tubular membranes. TEM observation revealed that the nanotubes have hollow cylinder structures up to several hundred micrometers long with 30-43-nm outer diameters and 14-29-nm inner diameters. By comparing the membrane stacking periodicity obtained from XRD analysis of the tubes with the molecular packing within single crystals , we found that the nanotubes consist of an unsymmetrical monolayer lipid membrane, in which the molecules are packed in parallel. This suggests that the inner surface of the nanotubes is covered with carboxy headgroups and the outer surface with 1-glucosamide headgroups. The inner diameters of the lipid nanotubes could be controlled in the range of 17.7 to 22.2 nm in steps of ~1.5 nm/2 carbons by varying the oligomethylene spacer length. References N. Kameta, M. Masuda, H. Minamikawa, N.V. Gotev, J.A. Rim, J.H. Jong, and T. Shimizu, Adv. Mater., in press. T. Shimizu, M. Masuda, and H. Minamikawa, Chem. Rev. 105, 1401 (2005). M. Masuda and T. Shimizu, Langmuir, 20, 5969 (2004). M. Masuda, K. Yoza, and T. Shimizu, Carbohydr. Res., 340, 2502 (2005).
4:00 PM - **U5.4
Template Wetting – A Construction Kit for 1D Nanostructures.
Martin Steinhart 1 , Markus Geuss 5 1 , Olaf Kriha 3 , Klaus Rademann 5 , Petra Goering 1 , Andreas Greiner 3 , Joachim Wendorff 3 , Ralf Wehrspohn 4 , Elke Hempel 2 , Ulrich Goesele 1 , Thomas Thurn-Albrecht 2 Show Abstract
1 , Max-Planck-Institute of Microstructure Physics, Halle Germany, 5 Department of Chemistry, Humboldt-University, Berlin Germany, 3 Department of Chemistry, Philipps-University, Marburg Germany, 4 Department of Physics, University of Paderborn, Paderborn Germany, 2 Department of Physics, Martin-Luther-University, Halle Germany
A plethora of functional materials has been formed into non-carbon nanotubes and nanorods by means of porous templates. The properties of the one-dimensional nanoobjects depend to a great extent on their internal mesoscopic fine structures, but little is known on the underlying physico-chemical phenomena governing the generation of these features. Wetting ordered porous alumina with polymeric melts and solutions allows not only realizing new nanotube architectures, but enables also a systematic investigation of structure formation processes inside the pores. Polymer nanotubes with a longitudinal gradient in composition have been prepared by face-to-face wetting, where different polymeric solutions simultaneously infiltrate porous alumina from the two opposite template surfaces. One-dimensional composite structures containing a block copolymer rod segment and a homopolymer tube segment can be prepared in such a way that the length of both segments is adjustable. Based on an X-ray analysis, we show how coherent kinetic control over the crystal orientation in macroscopic ensembles of nanotubes and nanorods inside porous alumina templates wetted by partially crystalline polymers is attained. We have identified two clear limiting cases. If the entities inside the template pores are crystallized in the presence of a connecting surface film, crystallization will start in this film. Exclusively those crystals grow along the template pores that have their dominant growth direction aligned with the long axes of the pores, resulting in large arrays of the nanostructures with uniform crystal orientation. In the absence of a surface film, crystallization is separately initiated within each pore by homogeneous nucleation, and any crystal orientation allowing the growth of the lamella crystals along the pores appears statistically. As an example of structure/property relationships thus arising, the native polarization and domain structure of ferroelectric polymer nanotubes as well as their local poling on the 100-nm scale are discussed. We believe that the concepts presented here are of general validity and potentially useful to control mechanical, electronic or piezoelectric properties of 1D nanostructures made of polymeric or even more generally organic materials. They might be components of bio-inspired adhesive structures, sensors, and nano-actuator arrays.
4:30 PM - U5.5
Gas Storage in Aromatic Nanochannels.
Roberto Simonutti 1 , Piero Sozzani 1 , Silvia Bracco 1 , Angiolina Comotti 1 , Lisa Ferretti 1 , Michele Mauri 1 Show Abstract
1 Materials Science, University of Milan-Bicocca, Milan, Mi, Italy
The application of the principles of self-assembly and crystal engineering permits the shaping of nanoscale environments lined with specific receptors for absorbing gases and vapors. We could obtain novel nanochannels held together by a network of weak van der Waals interactions that fabricate the zeolite-like host structure and cooperatively stabilize the in-diffusing gases. The molecular crystal can store at low pressure large amounts of carbon dioxide and methane selectively over nitrogen, oxygen and hydrogen. Carbon and proton Magic Angle Spinning NMR spectroscopy could recognize the specific interactions that contribute to the overall stabilization. The impressive upfield shifts caused by the aromatic ring currents on gas molecules at the van der Waals close contacts provide a tool for measuring the intermolecular distances, proving the formation of CH-π interactions and understanding the preferred topology of the gases interacting with the fully aromatic nanochannels. This provides one of the rare detailed description of gas molecules trapped into crystals. Also, the open nanochannels can be explored by the hyperpolarized xenon gas. In fact, the sensitivity of 129Xe NMR can be strongly enhanced by hyperpolarization (HP), a recent technique that, exploiting spin-exchange optical pumping, produces such a remarkable xenon nuclear polarization that a significant xenon signal can be detected by a few scans and minor amount of material. Anisotropic xenon signals are observed demonstrating the squeezing of the xenon atoms into the aromatic nanochannels. Furthermore, in the narrow nanochannels of porous crystals xenon atoms cannot bypass each other realizing a particular case of one-dimensional diffusion, called single-file diffusion. HP 129Xe NMR in the Continuous-Flow set-up made it possible to monitor single-file diffusion over a time-scale of tens of seconds.Reference: P. Sozzani, S. Bracco, A. Comotti, L. Ferretti, R. Simonutti “Methane and Carbon Dioxide Storage in a Porous van der Waals Crystal” Angew. Chem. Int. Ed., 2005, 44, 1816-1820 (VIP paper).
4:45 PM - U5.6
Relation Between Structure and Physical Properties for Conjugated Polymer Nanowires Prepared by the Template Method.
Jean-Luc Duvail 1 , Patrice Retho 1 , Yunze Long 1 , Vincent Fernandez 1 , Philippe Molinie 1 , Guy Louarn 1 , Olivier Chauvet 1 Show Abstract
1 , Institut des Materiaux, Nantes France
5:00 PM - U5.7
Microtubular Structure Composed of Self-assembled Nanofibrous Aggregates from Mono-alkylated L-Glutarimide Derivative.
Yoshiko Kira 1 , Hirotaka Harada 1 , Makoto Takafuji 1 , Hirotaka Ihara 1 Show Abstract
1 Department of Applied Chemistry and Biochemistry, Kumamoto University, Kumamoto Japan
U6: Composites of Carbon Nanotubes I
Wednesday PM, April 19, 2006
Room 2002 (Moscone West)
5:15 PM - U6.1
Metal-insulator Transition in DNA-functionalized Single-wall Carbon Nanotubes.
Vadim Puller 1 , Slava Rotkin 1 Show Abstract
1 Physics Department, Lehigh University, Bethlehem, Pennsylvania, United States
5:30 PM - U6.2
Reversible Control of Carbon Nanotube Microstructure Using Poly(acrylic acid).
Jaime Grunlan 1 2 3 , Lei Liu 3 2 , Yeon Seok Kim 1 2 Show Abstract
1 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Polymer Technology Center, Texas A&M University, College Station, Texas, United States, 3 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States
Single-walled carbon nanotubes (SWNTs) are an exciting material due to their small size, high modulus, and high intrinsic conductivity. As a result, nanotubes hold significant promise for imparting electrical conductivity, mechanical strength, and thermal conductivity to polymeric materials. Despite this potential, the ability to stabilize nanotubes in solution remains a significant hurdle to their widespread use. This has led to significant research efforts on the use of stabilizing agents and chemical modification of the nanotubes to impart solubility. Once stabilized, these nanotubes lend themselves to chemical modification, spectroscopic study, and/or incorporation into ink-based systems. Nanotube suspensions are currently being studied for use in drug and gene delivery applications. Solid films of SWNT-filled polymers are being studied for a variety of uses including thermal management, humidity sensing, and corrosion resistance. The present work demonstrates a method to control the microstructure of carbon nanotubes in aqueous solution and dry composite films using poly(acrylic acid). As the pH of an aqueous mixture containing 1 wt% PAA and 0.1 wt% SWNT is raised from 2 to 9, a significant increase in viscosity is observed that suggests improved exfoliation of nanotube bundles. Drying these mixtures into composite films reveals heavy aggregation of SWNTs at low pH and a well-dispersed network at high pH. These results are due to the de-protonation that occurs with PAA as pH increases, which enhances its ability to hydrogen bond and interact with SWNTs. Trends in mechanical properties and electrical conductivity confirm this idea of increasing polymer-nanotube interaction with pH. Additionally, these microstructural changes are fully reversible by simply reducing pH. This behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Many of the relationships uncovered here could be applied to other types of hydrophobic nanotubes and nanowires.
5:45 PM - U6.3
Chemical Vapor Deposition of Carbon Nanotube-Reinforced Polymer Composites.
Chi-Hwa Wu 1 2 , David Harding 1 2 Show Abstract
1 Laboratory for Laser Energetics, University of Rochester, Rochester, New York, United States, 2 Department of Chemical Engineering, University of Rochester, Rochester, New York, United States
Multiwalled carbon nanotube (MWNT)- reinforced polymer composite films were synthesized at low temperature by a two-step process using (i) microwave-assisted electron-cyclotron-resonance chemical vapor deposition (ECR-CVD) to make a MWNT mat at 450 °C on a catalyst-coated substrate with gas mixture of methane and hydrogen, and (ii) chemical vapor infiltration (CVI) of polymers into the nanotube mat. In this study, parylene and glow-discharge polymerization (GDP) polymers were utilized to infiltrate the nanotube mat at temperature below 200 °C. Sequentially depositing MWNT and then infiltrating with polymer requires low temperature for sustaining the polymer matrix. By taking advantages of the ECR-CVD system, e.g. high plasma density at low growth temperature, it is possible to prepare such composite films and a fully-dense material. A strong interfacial adhesion between the carbon nanotubes and the polymer matrix is a major factor that determines the reinforcement performance of such nanocomposites. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies showed that nanotubes embedded with the polymer matrix enhance interfacial adhesion by simple mechanical attaching or interlocking. The feasibility of making nanotube-reinforced composite depends on the processing parameters, including the effect of polymer vapor infiltration and the volume density of the nanotube mat. Characterizations of these composite films have been conducted and it was found that a fully-dense composite film was synthesized using a 40 vol.% MWNT mat vapor-deposited with parylene polymer, while the GDP polymer was found less than 3 μm infiltration with the same mat. In addition, the mechanical behaviors of these composites, including hardness and elastic modulus, were investigated using nano-indentation.
U7: Poster Session: Organic and Inorganic Nanotubes
Thursday AM, April 20, 2006
Salons 8-15 (Marriott)
9:00 PM - U7.1
Comparison of Piezoelectric and Carbon Nanotube-Based Actuators.
Hossein Golnabi 1 , Mahmod Ghorannevis 1 , Masoud Golnabi 1 Show Abstract
1 Plasma Physics Research Center, Islamic Azad University, Tehran Iran (the Islamic Republic of)
9:00 PM - U7.10
Carbon Nanotube – Polymer Composites as Field Emission Cathodes.
David Carey 1 , Richard Smith 1 , Ravi Silva 1 , Robert Murphy 2 , Werner Blau 2 , Jonathan Coleman 2 Show Abstract
1 Advanced Technology Institute, University of Surrey, Guildford United Kingdom, 2 School of Physics, Trinity College Dublin, Dublin Ireland
Carbon nanotubes have significant potential as large area cathodes for field emission displays. The use of carbon nanotube – polymer composites offers an important route to control the nanotube content and the properties of the cathode as a whole. Arc discharge multiwall carbon nanotubes have been incorporated into PmPV, a derivative of the conjugated polymer PPV. By successive dilutions of nanotube concentration, a range of samples with nanotube mass fractions up to 7 % was prepared and the resultant composites spin cast to form nanotube-polymer cathodes. Large area electron field emission characterisation was made as a function of nanotube mass fraction using phosphor coated anodes where electron emission at low applied electric fields was observed. From the resultant emission site maps and threshold electric fields, the transport and emission of electrons is discussed. Surrounding each nanotube is a polymer coating that acts as a tunnel barrier and the fluctuation induced tunnelling between the nanotubes in a disordered percolation network is shown to play an important role. Factors affecting the potential use of carbon nanotube – polymer composites for field emission based displays are also discussed.
9:00 PM - U7.11
Developments in Nanomanipulation for Field Emission from Carbon Nanotubes.
Richard Smith 1 , David Carey 1 , David Cox 1 , Ravi Silva 1 Show Abstract
1 Advanced Technology Institute, University of Surrey, Guildford United Kingdom
Field emission (FE) based devices using carbon nanotubes, such as displays and high current density microwave sources are beginning to emerge. It is well known that the fraction of nanotubes emitting in such devices can be quite low and in some cases below 10%. Most measurements techniques, such as current-field characterisation using phosphor coated anodes, tend to reflect the density of emitting nanotubes with the lowest local threshold fields for emission. An alterative method is to measure the FE characteristics using local probe electrodes attached to high precision manipulators. We show that by performing such measurements within a scanning electron microscope, complementary electrical and structural information about the nanotube can be obtained. In a two terminal arrangement, by varying the position of the anode electrode, information about local electric field and field enhancement factor can be obtained. By incorporating a third electrode and using a focussed ion beam system to produce a circular aperture, a gate electrode can be produced to provide three terminal characterisation. We show that such an arrangement is able to characterise an individual carbon nanotube. Estimates of the anode field screening factor due the presence of the metallic gate and the gate transparency factor can be obtained. Methods for local probe measurements for nanotubes are also discussed.
9:00 PM - U7.12
Catalytic Growth of Single-Walled Carbon Nanotubes: Effect of Catalyst Composition and Synthesis Parameters.
Elena Mora 1 , John Pigos 1 , Toshio Tokune 1 , Avetik Harutyunyan 1 Show Abstract
1 , Honda Research Institute, Columbus, Ohio, United States
The growing interest to use carbon single-walled nanotubes (SWNTs) for fundamental science and applications demands a reasonably pure and homogeneous (diameter, chirality) material. To achieve this, it is necessary to have a full understanding of the effect of the catalyst composition and the synthesis parameters on the growth of the tubes.In this work, a series of catalysts (Fe, Fe/Mo and their corresponding oxides), supported on alumina, were examined for the growth of SWNTs using chemical vapor deposition method (CVD) with methane gas under different conditions. To discuss the growth mechanism, experimental results from calorimetric measurements of the catalysts melting points, in situ mass spectrometer studies of the gases evolved during the synthesis, and thermogravimetrical and Raman measurements of the synthesized materials were used. The findings support a growth mechanism based on the liquefaction of the catalyst particles due to carbon diffusion into the nanoparticles [1,2] and termination of the process caused by the formation of stable carbide phases and amorphous carbon.The presence of Mo in the composition was found to modify the characteristics of the Fe catalyst by improving the efficiency of the hydrocarbon decomposition, assisting the carbon-induced liquefaction and affecting the catalyst “lifetime”. Consequently, the growth of SWNTs was observed to initiate earlier and prolong for longer times, resulting in higher yields. Moreover, results point to the formation of an alloy between both metals (Fe and Mo). On the other hand, the use of metal oxides catalyst particles was found surprisingly to exhibit similar catalyst activity as the reduced forms. However, it was observed earlier  that higher temperatures were required to initiate the nucleation and growth of the nanotubes.Finally, the effect of the carbon feedstock on the synthesis was analyzed. We found that the hydrocarbon (methane) flow rate has a dramatic impact on the catalyst activity, “lifetime” and efficiency of nanotubes formation. Particularly, the increase of the flow rate up to 15 cm3min-1mg-1Fe increased the resulted carbon concentration and decreased the period of time that the catalyst was active. Meanwhile, a flow rate of 220 cm3min-1mg-1Fe decreased the catalyst “lifetime” by almost 10 times, and assisted the formation of amorphous carbon and/or stable Fe carbide solid phases resulting in an early termination of the growth.1. A. R. Harutyunyan, E. Mora, T. Tokune, Appl. Phys. Lett. 86, 153113, 2005.2. A. R. Harutyunyan, E. Mora, T. Tokune, Appl. Phys. Lett. 87, 051919, 2005.3. A. R. Harutyunyan, B. K. Pradhan, U. J. Kim, G. Chen, P. C. Eklund, Nano Letters 2, 525, 2002.
9:00 PM - U7.13
Ab-Initio Modeling of Contact Formation in Carbon Nanotube Devices.
Karthik Ravichandran 1 , Wolfgang Windl 1 , Leonardo Fonseca 2
1 Materials Science & Engineering, The Ohio State University, Columbus, Ohio, United States, 2 Center fo