Showing papers in "Nano Letters in 2002"
TL;DR: In this paper, a soft solution-phase approach to the large-scale synthesis of uniform nanowires of bicrystalline silver whose lateral dimensions could be controlled in the range of 30−40 nm, and lengths up to ∼50 μm.
Abstract: This paper describes a soft, solution-phase approach to the large-scale synthesis of uniform nanowires of bicrystalline silver whose lateral dimensions could be controlled in the range of 30−40 nm, and lengths up to ∼50 μm. The first step of this procedure involved the formation of platinum nanoparticles by reducing PtCl2 with ethylene glycol heated to ∼160 °C. Due to their close match in crystal structure and lattice constants, these platinum nanoparticles could serve as seeds for the heterogeneous nucleation and growth of silver that was produced in the solution via the reduction of AgNO3 with ethylene glycol. When surfactants such as poly(vinyl pyrrolidone) (PVP) were present in this solution, the silver could be directed to grow into uniform nanowires with aspect ratios as high as ∼1000. Measurements of transport property at room temperature indicated that these nanowires were electrically continuous with a conductivity of approximately 0.8 × 105 S/cm.
1,499 citations
TL;DR: In this article, a hybrid pulsed laser ablation/chemical capor deposition (PLA-CVD) process was proposed for the synthesis of semiconductor nanowires with longitudinal ordered heterostructures.
Abstract: Heterojunction and superlattice formation is essential for many potential applications of semiconductor nanowires in nanoscale optoelectronics. We have developed a hybrid pulsed laser ablation/chemical capor deposition (PLA-CVD) process for the synthesis of semiconductor nanowires with longitudinal ordered heterostructures. The laser ablation process generates a programmable pulsed vapor source, which enables the nanowire growth in a block-by-block fashion with a well-defined compositional profile along the wire axis. Single-crystalline nanowires with longitudinal Si/SiGe superlattice structure have been successfully synthesized. This unique class of heterostructured one-dimensional nanostructures holds great potential in applications such as light emitting devices and thermoelectrics.
1,057 citations
TL;DR: In this article, a sol−gel approach for the coating of superparamagnetic iron oxide nanoparticles with uniform shells of amorphous silica is described, which can be applied to particles contained in a commercial ferrofluid (e.g., the EMG 304 of Ferro-fluidics) and those synthesized through a wet chemical process.
Abstract: This paper describes a sol−gel approach for the coating of superparamagnetic iron oxide nanoparticles with uniform shells of amorphous silica. The coating process has been successfully applied to particles contained in a commercial ferrofluid (e.g., the EMG 304 of Ferrofluidics) and those synthesized through a wet chemical process. The thickness of silica coating could be conveniently controlled in the range of 2−100 nm by changing the concentration of the sol−gel solution. Fluorescent dyes, for example, 7-(dimethylamino)-4-methylcoumarin-3-isothiocyanate (DACITC) and tetramethylrhodamine-5-isothiocyanate (5-TRITC), have also been incorporated into the silica shells by covalently coupling these organic compounds with the sol−gel precursor. These multifunctional nanoparticles are potentially useful in a number of areas because they can be simultaneously manipulated with an externally applied magnetic field and characterized in situ using conventional fluorescence microscopy.
1,019 citations
TL;DR: In this article, a vapor phase approach to the facial synthesis of cupric oxide (CuO) nanowires supported on the surfaces of various copper substrates that include grids, foils, and wires was described.
Abstract: This paper describes a vapor-phase approach to the facial synthesis of cupric oxide (CuO) nanowires supported on the surfaces of various copper substrates that include grids, foils, and wires. A typical procedure simply involved the thermal oxidation of these substrates in air and within the temperature range from 400 to 700 °C. Electron microscopic studies indicated that these nanowires had a controllable diameter in the range of 30−100 nm with lengths of up to 15 μm by varying the temperature and growth time. Electron diffraction and high-resolution TEM studies implied that each CuO nanowire was a bicrystal divided by a (111) twin plane in its middle along the longitudinal axis. A possible mechanism was also proposed to account for the growth of these CuO nanowires.
971 citations
TL;DR: In this article, the authors proposed that self-ordering of porous alumina with any interpore distance is possible if the applied potential and pH value of the electrolyte, which mainly determines the pore radius, match the 10% porosity rule.
Abstract: Transmission electron microscopy analysis of self-ordered porous alumina obtained by electrochemical anodization shows that self-ordering requires a porosity of 10%, independent of the specific anodization conditions. This corresponds to a volume expansion of alumina to aluminum of about 1.2. We propose that self-ordering of porous alumina with any interpore distance is possible if the applied potential, which mainly determines the interpore distance, and the pH value of the electrolyte, which mainly defines the pore radius, match the 10% porosity rule.
965 citations
TL;DR: In this article, gate-dependent electrical transport measurements show that the GaN NWs are n-type and that the conductance of NW−FETs can be modulated by more than 3 orders of magnitude.
Abstract: Field effect transistors (FETs) based on individual GaN nanowires (NWs) have been fabricated. Gate-dependent electrical transport measurements show that the GaN NWs are n-type and that the conductance of NW−FETs can be modulated by more than 3 orders of magnitude. Electron mobilities determined for the GaN NW FETs, which were estimated from the transconductance, were as high as 650 cm2/V·s. These mobilities are comparable to or larger than thin film materials with similar carrier concentration and thus demonstrate the high quality of these NW building blocks and their potential for nanoscale electronics. In addition, p−n junctions have been assembled in high yield from p-type Si, and these n-type GaN NWs and their potential applications are discussed.
931 citations
TL;DR: The streptavidin/biotin system is used to investigate the adsorption behavior of proteins on the sides of single-walled carbon nanotubes (SWNTs) and the results have implications to the nanotube biocompatibility 11 issue and specificity of potential bioelectronic devices based on nanot tubes.
Abstract: The interface between biological molecules and novel nanomaterials is important to developing new types of miniature devices for biological applications. Here, the streptavidin/biotin system is used to investigate the adsorption behavior of proteins on the sides of single-walled carbon nanotubes (SWNTs). Functionalization of SWNTs by coadsorption of a surfactant and poly(ethylene glycol) is found to be effective in resisting nonspecific adsorption of streptavidin. Specific binding of streptavidin onto SWNTs is achieved by co-functionalization of nanotubes with biotin and protein-resistant polymers. Recent years have witnessed a significant interest in biological applications of novel solid-state nanomaterials. 1-6 The unique physical properties of molecular- or nanoscale solids (dots or wires) when utilized in conjunction with the remarkable biomolecular recognition capabilities could lead to miniature biological electronics and optical devices including probes and sensors. Not only could these devices exhibit advantages over existing technology in size but also in performance. Several issues are important regarding nanomaterial/biosystems. One of them is biocompatibility, especially for in-vivo applications of implantable bioelectronic devices. Another is specificity that requires biofunctionalization of nanomaterials for recognition of only one type of target biomolecule in solution and rejection of others. Central to tackling these issues is surface functionalization of nanomaterials and elucidating the interfaces and interactions between nanomaterials and biosystems. Single-walled carbon nanotubes (SWNTs) are novel molecular scale wires exhibiting useful properties for various potential applications including miniature biological devices. For instance, nanotubes can be used as electrodes for detecting biomolecules in solutions, similar to commonly used conventional carbon based electrode materials. Also, the electrical properties of SWNTs are sensitive to surface charge transfer and changes in the surrounding electrostatic environment, undergoing drastic changes by simple adsorptions of certain molecules or polymers. 7-10 SWNTs are therefore promising for chemical sensors for detecting molecules in the gas phase and biosensors for probing biological processes in solutions. Nevertheless, significant effort is required in order to understand interactions between nanotubes and biomolecules and how to impart specificity and selectivity to nanotube-based bioelectronic devices. Motivated by the biological application prospects of solidstate nanomaterials, this work investigates (1) nonspecific binding (NSB) of proteins to SWNTs, (2) functionalization of nanotubes for resisting nonspecific interactions, and (3) enabling specific binding of proteins to functionalized nanotubes. We find that streptavidin nonspecifically binds to as-grown SWNTs and show that prevention of NSB of streptavidin on SWNTs is achieved by coating nanotubes with a surfactant and poly(ethylene glycol), PEG. Selective binding of streptavidin is introduced by co-functionalization of SWNTs with PEG and biotin. The results have implications to the nanotube biocompatibility 11 issue and specificity of potential bioelectronic devices based on nanotubes. In an earlier communication, we have shown that protein binding to SWNTs is reliably enabled via a noncovalent sidewall functionalization scheme. 5 In this manner, a variety
887 citations
TL;DR: In this paper, a general approach that generates nanoscale hollow structures of metals by reacting solutions of appropriate salt solutions with solid templates of a more reactive metal is described, which are completely converted into soluble species during the replacement reaction.
Abstract: This paper describes a general approach that generates nanoscale hollow structures of metals by reacting solutions of appropriate salt solutions with solid templates of a more reactive metal. Typical examples include Au3+, Pt2+, and Pd2+ salts and nanoparticles or nanowires of silver. The morphology, void space, and wall thickness of these hollow structures are all determined by the solid templates, which are completely converted into soluble species during the replacement reaction. Both electron microscopy and diffraction studies indicate that single crystalline hollow structures of metals can also be obtained when the templates are single crystals. These metallic hollow structures, having well-controlled sizes and shapes, are expected to find use in a number of applications that involve nanoscale encapsulation, drug delivery, plasmon photonics, and calorimetric sensing.
882 citations
TL;DR: In this paper, the authors used live plants for the fabrication of nanoparticles and found that the Au nanoparticles are in a crystalline state and showed defects such as twins in the crystal structure and icosahedral nanoparticles were found.
Abstract: In modern nanotechnology one of the most exciting areas is the interaction between inorganic quantum dots and biological structures. For instance gold clusters surrounded by a shell of organic ligands covalently attach to proteins or other biological substances and can be used for labeling in structural biology. In the present report we show the possibility of using live plants for the fabrication of nanoparticles. Alfalfa plants were grown in an AuCl4 rich environment. The absorption of Au metal by the plants was confirmed by X-ray absorption studies (XAS), and transmission electron microscopy (TEM). Atomic resolution analysis confirmed the nucleation and growth of Au nanoparticles inside the plant and that the Au nanoparticles are in a crystalline state. Images also showed defects such as twins in the crystal structure, and in some cases icosahedral nanoparticles were found. X-ray EDS studies corroborated that the nanoparticles are pure gold. This is the first report on the formation of gold nanoparticl...
845 citations
TL;DR: A variety of novel hierarchical nanostructures with 6-, 4-, and 2-fold symmetries have been successfully grown by a vapor transport and condensation technique.
Abstract: A variety of novel hierarchical nanostructures with 6-, 4-, and 2-fold symmetries have been successfully grown by a vapor transport and condensation technique. It was found that the major core nano...
836 citations
TL;DR: A simple synthetic route for the preparation of high quality CdSe/ZnSe core/shell nanocrystals without the use of any pyrophoric organometallic precursors is presented in this article.
Abstract: A simple synthetic route for the preparation of high-quality CdSe/ZnSe core/shell nanocrystals without the use of any pyrophoric organometallic precursors is presented. Effective surface passivation of monodisperse CdSe nanocrystals is achieved by overcoating them with a ZnSe shell, applying zinc stearate as a zinc source. The resulting core/shell nanocrystals exhibit high room temperature photoluminescence efficiencies (60−85%) in organic solvents as well as in water after functionalization with mercaptoundecanoic acid (MUA).
TL;DR: In this article, the growth of one-dimensional semiconductor nanocrystals, nanowhiskers, is reported, in which segments of the whisker with different composition are formed, illustrated by InAs whiskers containing segments of InP.
Abstract: We report growth of one-dimensional semiconductor nanocrystals, nanowhiskers, in which segments of the whisker with different composition are formed, illustrated by InAs whiskers containing segments of InP. Our conditions for growth allow the formation of abrupt interfaces and heterostructure barriers of thickness from a few monolayers to 100s of nanometers, thus creating a one-dimensional landscape along which the electrons move. The crystalline perfection, the quality of the interfaces, and the variation in the lattice constant are demonstrated by high-resolution transmission electron microscopy, and the conduction band off-set of 0.6 eV is deduced from the current due to thermal excitation of electrons over an InP barrier.
TL;DR: In this article, a simple procedure for dispersing as-produced nanotubes powder in aqueous solutions of Gum Arabic is described, and a stable dispersion of full-length, well separated, individual tubes is formed.
Abstract: Single-wall carbon nanotubes pack into crystalline ropes that aggregate into tangled networks due to strong van der Waals attraction. Aggregation acts as an obstacle to most applications, and diminishes the special properties of the individual tubes. We describe a simple procedure for dispersing as-produced nanotubes powder in aqueous solutions of Gum Arabic. In a single step, a stable dispersion of full-length, well separated, individual tubes is formed, apparently due to physical adsorption of the polymer.
TL;DR: The lifetime of Eu3+ at a doping concentration of 5% were 7.7 ± 0.2 ms, indicative of very high quantum yields as mentioned in this paper, and the probability of nonradiative decay for ions at or near the surface and ions in the core of the particles.
Abstract: Nanoparticles of LaF3 doped with Ln3+ (Ln = Eu, Er, Nd, and Ho) have been prepared that are dispersible in organic solvents. From the spectrum of Eu3+ it has been concluded that the dopant ion occupies a La3+ site. The luminescence decays are fitted biexponentially. A given possible explanation for this is a different probability of nonradiative decay for ions at or near the surface and ions in the core of the particles. The lifetimes of Eu3+ luminescence at a doping concentration of 5% were 7.7 ± 0.2 and 2.9 ± 0.2 ms, indicative of very high quantum yields. The particles doped with Er3+, Nd3+, and Ho3+ are promising materials for polymer-based optical components, because they show luminescence in the telecommunication window (i.e., Er3+ at 1530 nm, Nd3+ at 1330 nm, and Ho3+ at 1450 nm).
TL;DR: The first use of electrospun nanofibrous membranes as highly responsive fluorescence quenching-based optical sensors for metal ions (Fe3+ and Hg2+) and 2,4-dinitrotoluene (DNT) was reported in this article.
Abstract: The first use of electrospun nanofibrous membranes as highly responsive fluorescence quenching-based optical sensors for metal ions (Fe3+ and Hg2+) and 2,4-dinitrotoluene (DNT) is reported. A fluorescent polymer, poly(acrylic acid)−poly(pyrene methanol) (PAA−PM), was used as a sensing material. Optical chemical sensors were fabricated by electrospinning PAA−PM and thermally cross-linkable polyurethane latex mixture solutions. These sensors showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures.
TL;DR: Exploration of the phase diagram of the lamellar to phospholipid−detergent mixed micelle transition reveals that self-assembly proceeds from the mixed micellar phase, and a homogeneous and monodisperse population is formed.
Abstract: Nanoparticulate phospholipid bilayer disks were assembled from phospholipid and a class of amphipathic helical proteins termed membrane scaffold proteins (MSP). Several different MSPs were produced in high yield using a synthetic gene and a heterologous expression system and purified to homogeneity by a one-step purification. The self-assembly process begins with a mixture of the phospholipid and MSP in the presence of a detergent. Upon removal of detergent, 10-nm diameter particles form containing either saturated or unsaturated phospholipid. The ratio of components in the initial mixture was found to be crucial for formation of a monodisperse population of nanoparticles. Exploration of the phase diagram of the lamellar to phospholipid−detergent mixed micelle transition reveals that self-assembly proceeds from the mixed micellar phase. In this case a homogeneous and monodisperse population is formed. In contrast, particle formation from the detergent−phospholipid lamellar phase results in altered size, y...
TL;DR: Truncated triangular silver nanoplates have been synthesized in large quantities using a solution phase method in the presence of cetyltrimethylammonium bromide micelles.
Abstract: Truncated triangular silver nanoplates have been synthesized in large quantities using a solution phase method in the presence of cetyltrimethylammonium bromide micelles. The obtained particles have an average edge size of 68 nm, thickness of 24 nm, and the degree of truncation of 0.35. They are single crystals, with a (111) lattice plane as the basal plane. The aqueous solution of these particles displays a clear red color due to a strong in-plane dipole plasmon resonance peaked at 552 nm. These particles can self-assemble into chainlike nanostructures through either partial or close stacking of neighborhood nanoplates.
TL;DR: In this article, a mixture of nanoprisms and nanospheroids was synthesized by boiling AgNO3 in N,N-dimethyl formamide, in the presence of poly(vinylpyrrolidone).
Abstract: Polygonal (mainly triangular) silver nanoprisms were synthesized by boiling AgNO3 in N,N-dimethyl formamide, in the presence of poly(vinylpyrrolidone). Although during the synthesis, a mixture of nanoprisms and nanospheroids is formed, the latter can be removed through careful centrifugation. The UV−visible spectra of the nanoprisms display an intense in-plane dipolar plasmon resonance band, as well as weak bands for in-plane and out-of-plane quadrupolar resonances. The nanoprisms are also stable in other solvents, such as ethanol and water, and solvent exchange leads to strong shifts of the in-plane dipole plasmon band.
TL;DR: In this paper, the enhancement of luminescence of (CdSe)ZnS core−shell quantum dots on gold colloids as a function of semiconductor nanocrystal−metal nanoparticle distance was studied.
Abstract: We have studied the enhancement of luminescence of (CdSe)ZnS core−shell quantum dots on gold colloids as a function of semiconductor nanocrystal−metal nanoparticle distance. Using a layer-by-layer polyelectrolyte deposition technique to insert well-defined spacer layers between gold colloids and quantum dots, a distance-dependent enhancement and quenching of quantum dot photoluminescence has been observed. The maximum enhancement by a factor of 5 is achieved for a 9-layer spacer (≈11 nm). The efficient quantum dot excitation within the locally enhanced electromagnetic field produced by the gold nanoparticles is evidenced by the observation of the surface plasmon resonance in the photoluminescence excitation spectrum of (CdSe)ZnS nanocrystals.
TL;DR: In this paper, high performance field effect transistors made from semiconducting single-walled carbon nanotubes (SWNTs) were fabricated using chemical vapor deposition to grow the tubes, annealing to improve the contacts, and an electrolyte as a gate.
Abstract: We have fabricated high performance field-effect transistors made from semiconducting single-walled carbon nanotubes (SWNTs). Using chemical vapor deposition to grow the tubes, annealing to improve the contacts, and an electrolyte as a gate, we obtain very high device mobilities and transconductances. These measurements demonstrate that SWNTs are attractive for both electronic applications and for chemical and biological sensing.
TL;DR: In this article, a single-walled nanotube transistor is used to construct a nonvolatile charge-storage memory element operating at room temperature, which can be reversibly written, read, and erased at temperatures up to 100 K.
Abstract: A high-mobility (9000 cm2/V·s) semiconducting single-walled nanotube transistor is used to construct a nonvolatile charge-storage memory element operating at room temperature. Charges are stored by application of a few volts across the silicon dioxide dielectric between nanotube and silicon substrate, and detected by threshold shift of the nanotube field-effect transistor. The high mobility of the nanotube transistor allows the observation of discrete configurations of charge corresponding to rearrangement of a single or few electrons. These states may be reversibly written, read, and erased at temperatures up to 100 K.
TL;DR: In this article, high quality InP nanocrystals without any size sorting were synthesized in a noncoordinating solvent by strictly controlling the reaction parameters, which is much faster, less expensive, and "greener" than any current methods.
Abstract: High quality InP nanocrystals without any size sorting were synthesized in a noncoordinating solvent by strictly controlling the reaction parameters. This synthetic method is much faster, less expensive, and “greener” than any current methods for the synthesis of high quality InP nanocrystals. Fatty acids with well-defined chain lengths as the ligands, a noncoordinating solvent, and a thorough degassing process are critical factors for the formation of high quality InP nanocrystals. The growth of nearly monodisperse InAs nanocrystals through a similar scheme was also observed.
TL;DR: In this article, the authors showed that these core−shell particles could be assembled into long-range ordered lattices (or photonic crystals) over large areas that exhibited optical properties different from those crystallized from silica colloids.
Abstract: Gold nanoparticles have been coated with amorphous silica to form spherical colloids with a core−shell structure The thickness of silica shells could be conveniently controlled in the range of tens to several hundred nanometers by changing the concentration of the sol−gel precursor or the coating time These core−shell colloids could serve as the building blocks to fabricate photonic devices In one demonstration, we showed that these core−shell particles could be assembled into long-range ordered lattices (or photonic crystals) over large areas that exhibited optical properties different from those crystallized from silica colloids Transmission spectra of these crystals displayed both features that correspond to the Bragg diffraction of a periodic lattice and the plasmon resonance absorption of gold nanoparticles Reflectance spectra taken from these crystals only showed peaks caused by Bragg diffraction In another demonstration, these core−shell colloids were assembled into chains of different config
TL;DR: In this article, the plasmon absorption band of Ag−Au nanoparticles shifts linearly to the red with increasing Au content, and the authors concluded that the nanoparticles are alloys, rather than core−shell composites.
Abstract: Gold−silver alloy nanoparticles were synthesized via reduction of varying mole fractions of HAuCl4 and AgNO3 by sodium borohydride in the presence of sodium citrate as a capping agent, in water. Solution concentrations were adjusted to avoid the precipitation of AgCl during the course of the reaction. The plasmon absorption band of Ag−Au nanoparticles shifts linearly to the red with increasing Au content. Due to the direct dependence of the metal salt ratio to the shift of the absorbance peak and the lack of an apparent core−shell structure in transmission electron microscope images, it is concluded that the nanoparticles are alloys, rather than core−shell composites.
TL;DR: Characterizations and bioactivities show that the conjugate samples indeed contain both carbon nanotubes and BSA proteins and that the protein species are intimately associated with the nanot tubes.
Abstract: Carbon nanotubes are functionalized by bovine serum albumin (BSA) proteins via diimide-activated amidation under ambient conditions. The nanotube-BSA conjugates thus obtained are highly water-soluble, forming dark-colored aqueous solutions. Results from characterizations using atomic force microscopy (AFM), thermal gravimetric analysis, Raman, and gel electrophoresis show that the conjugate samples indeed contain both carbon nanotubes and BSA proteins and that the protein species are intimately associated with the nanotubes. Bioactivities of the nanotube-bound proteins are evaluated using the total protein micro-determination assay (the modified Lowry procedure). The results show that the overwhelming majority (∼90%) of the protein species in the nanotube-BSA conjugates remain bioactive.
TL;DR: The immunocomplexes can be considered as a prototype of NP superstructures based on biospecific ligands, while the competitive FRET inhibition can be used in an immunoassay protocol.
Abstract: Complementary bioconjugates based on antibody−antigen interactions were synthesized from luminescent CdTe nanoparticles (NPs). Antigen (bovine serum albumin) was conjugated to red-emitting CdTe NPs, while green-emitting NPs were attached to the corresponding anti-BSA antibody (IgG). The NP bioconjugates were characterized by native and SDS−PAGE electrophoresis, gel-permeation HPLC, and circular dichroism. Antigen−antibody binding affinity was evaluated by enzyme-linked immunosorbent assay (ELISA). The formation of BSA−IgG immunocomplex resulted in the Forster resonance energy transfer (FRET) between the two different NPs: the luminescence of green-emitting NPs was quenched whereas the emission of the red-emitting NPs was enhanced. The luminescence recovered when the immunocomplex was exposed to an unlabeled antigen. The immunocomplexes can be considered as a prototype of NP superstructures based on biospecific ligands, while the competitive FRET inhibition can be used in an immunoassay protocol.
TL;DR: In this paper, high-ordered TiO2 single-crystalline nanowire arrays have been fabricated within the pores of anodic aluminum oxide (AAO) template by a cathodically induced sol−gel method.
Abstract: Highly ordered TiO2 single-crystalline nanowire arrays have been fabricated within the pores of anodic aluminum oxide (AAO) template by a cathodically induced sol−gel method. Raman spectra confirmed that the nanowires are composed of pure anatase TiO2. TEM investigations indicated that these nanowires have a uniform tetragonal single-crystal structure. Finally, a possible growth mechanism of the TiO2 nanowires is discussed.
TL;DR: In this article, the strength of silica aerogel monoliths was improved by cross-linking the nanoparticle building blocks of preformed silica hydrogels with poly(hexamethylene diisocyanate).
Abstract: In the quest for strong lightweight materials, silica aerogels would be very attractive, if they were not fragile. The strength of silica aerogel monoliths has been improved by a factor of over 100 through cross-linking the nanoparticle building blocks of preformed silica hydrogels with poly(hexamethylene diisocyanate). Composite monoliths are much less hygroscopic than native silica, and they do not collapse when in contact with liquids.
TL;DR: In this paper, single and multiwalled carbon nanotubes dispersed in nematic liquid crystal (LC) solvents are found to be orientationally ordered by the nematic matrix, and procedures for the preparation of monolayer and multilayer nanotube films with organization controlled using well-established methods of LC alignment, including grooved surfaces, magnetic fields, and patterned electrodes.
Abstract: Single- and multiwalled carbon nanotubes dispersed in nematic liquid crystal (LC) solvents are found to be orientationally ordered by the nematic matrix. Procedures are demonstrated for the preparation of monolayer and multilayer nanotube films with organization controlled using well-established methods of LC alignment, including grooved surfaces, magnetic fields, and patterned electrodes. LC alignment should be possible with other nanometer-sized building blocks, offering a general route for controlled assembly of organized nanomaterials and devices.
TL;DR: In this paper, the authors showed that multiwalled nanotubes (MWNTs) annealed at 2200 to 2800 °C are more air stable than as-produced MWNTs.
Abstract: Thermogravimetric analysis (TGA) has demonstrated that multiwalled nanotubes (MWNTs) annealed at 2200 to 2800 °C are more air stable than as-produced MWNTs, diamond, graphite, and annealed diamond. The annealed MWNTs are similar in stability to annealed graphite. Defect sites along the walls and at the ends of the raw MWNTs facilitate the thermal oxidative destruction of the nanotubes. Thermal annealing removes these defects, thereby providing MWNTs with enhanced air stability.