Etching of carbon nanotubes by ozone--a surface area study

The oxidative etching of single walled carbon nanotubes (SWNTs) is useful for opening the end caps and the sidewalls of the nanotubes to provide access to the interior. We have studied the effect of successive treatment of SWNTs by 95% pure O(3)(g), which is a powerful and convenient oxidizing agent. The surface area of the SWNTs was measured following exposure to O(3)(g) at 300 K and also following heating to 1073 K in a vacuum to decompose the oxidized groups on the nanotubes, a procedure called etching. This O(3)-induced etching process was observed by scanning electron microscopy and by transmission electron microscopy, and the kinetics of the process was studied gravimetrically. It was found that O(3) attack occurs preferentially on the outermost geometric surface of the conglomerate sample of the nanotubes as a result of the high efficiency of O(3) to react in a few collisions with the nanotube surface. Ozone-induced etching causes the loss of pores in the 20 A diameter range as observed by nitrogen adsorption at equilibrium by density functional theory analysis.     

Efficient quenching of photoluminescence from functionalized single-walled carbon nanotubes by nitroaromatic molecules

The photoluminescence from functionalized single-walled carbon nanotubes was found to be highly sensitive to the presence of nitroaromatic compounds such as nitrobenzene, 4-nitrotoluene, and 2,4-dinitrotoluene. The strong luminescence quenching in solution was at the upper limit of diffusion-control and also showed significant static quenching contributions. Mechanistic implication of the results and potential applications are discussed.     

Nitrogen-doped carbon aerogel synthesis by solvothermal gelation for supercapacitor application

Journal of Solid State Electrochemistry - Nitrogen-doped mesoporous carbon aerogel having high surface area and high nitrogen content was synthesized by sol–gel method for supercapacitor...     

Size-controlled synthesis and characterization of quantum-size SnO2 nanocrystallites by a solvothermal route

By using ethylenediamine as both an alkali and ligand, quantum size SnO₂ nanocrystallites were synthesized with a solvothermal route. The transmission electron micrographs (TEM) were employed to characterize the morphologies of the products. The crystal sizes of the as-synthesized SnO₂ were ranged form 2.5 to 3.6 nm. The crystal structure and optical properties of the products were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, optical absorption spectra, photoluminescence and Raman spectra. Anisotropic growth of the SnO₂ nanocrystallites was observed by altering the solvent from water to ethanol. The SnO₂ nanocrystal showed apparent quantum confinement effects. Finally, the mechanism for the formation of quantum size SnO₂ was also discussed.     

Catalyst volume to surface area constraints for nucleating carbon nanotubes

In this Article, we describe a carbon nanotube formation model in which sp2 carbon hemispheres form the embryonic caps from which a nanotube can grow. This requirement leads to a single wall carbon nanotube formation window concomitant with our systematic experimental findings, which show upper and lower diameter limits. Further, the successful formation of a nucleation cap (hemisphere) is governed by catalyst particle volume to surface area considerations. Single wall carbon nanotubes are only obtained when both the nanotube formation window and the precipitating catalyst size distribution cross over. The extent to which these two windows overlap establishes the mean diameter and diameter distribution of the obtained single wall carbon nanotubes.     

Dendrimer-assisted low-temperature growth of carbon nanotubes by plasma-enhanced chemical vapor deposition

Using a shielded growth approach and N2-annealed, nearly monodispersed Fe2O3 nanoparticles synthesized by interdendritic stabilization of Fe3+ species within fourth-generation poly(amidoamine) dendrimers, carbon nanotubes and nanofibers were successfully grown at low substrate temperatures (200-400 degrees C) by microwave plasma-enhanced chemical vapor deposition.     

One-step solvothermal synthesis of single-crystalline TiOF2 nanotubes with high lithium-ion battery performance

Single-crystalline TiOF(2) nanotubes were prepared by a one-step solvothermal method. The nanotubes are rectangular in shape with a length of 2-3?μm, width of 200-300?nm, and wall thickness of 40-60?nm. The formation of TiOF(2) nanotubes is directly driven by the interaction between TiF(4) and oleic acid in octadecane to form the 1D nanorods, and this is followed by a mass diffusion process to form the hollow structures. The synthesis approach can be extended to grow TiOF(2) nanoparticles and nanorods. Compared with TiO(2), which is the more commonly considered anode material in lithium-ion batteries, TiOF(2) has the advantages of a lower Li-intercalation voltage (e.g., to help increase the total voltage of the battery cell) and higher specific capacities. The TiOF(2) nanotubes showed good Li-storage properties with high specific capacities, stable cyclabilities, and good rate capabilities.     

High surface area carbon aerogels as porous substrates for direct growth of carbon nanotubes

Novel carbon composites are fabricated through catalyzed CVD growth of carbon nanotubes directly on the inner surfaces of monolithic carbon aerogel (CA) substrates. Uniform CNT yield is obtained throughout the internal pore volume of CA monoliths with macroscopic dimensions. These composites possess large surface areas (>1000 m(2) g(-1)) and exhibit enhanced electrical conductivity following CNT growth.     

Controlled synthesis of tetragonal terbium orthophosphate nanostructures through a solvothermal route

The tetragonal TbPO₄ was controlled synthesized via a simple solvothermal route by using glycol as solvent. The structures and micromorphologies of the as-synthesized TbPO₄ have been investigated by means of X-ray powder diffraction (XRD) and field-emission scanning electronic microscopy (FE-SEM). The results showed that the tetragonal TbPO₄ are composed of square-like particles about 200 nm in diameter. The photoluminescence spectra exhibited that the emission spectra of the sample could be divided into two parts, representing the ⁵D₄ ?? ⁷F_J (J = 6, 5, 4, 3) transitions and ⁵D₃ ?? ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺.     

溶剂热合成碳纳米管

自1991年Iijima发现碳纳米管以来,碳纳米管因其独特的结构和物理化学性质而成为人们的研究热点。     

乙二胺溶剂热还原法制备碳纳米管

以乙二胺作为溶剂和碳源,用KBH4还原NiCl2得到的镍作为催化剂,于300℃制备碳纳米管。X-射线衍射(XRD)、透射电子显微镜(TEM)、选区电子衍射(SAED)和Raman光谱分析证明,产品为多壁碳纳米管,直径约为100nm,长度达几微米。该方法具有反应温度低、反应时间短、操作简便等特点。     

A route for bulk separation of semiconducting from metallic single-wall carbon nanotubes

Substantial separation of single-wall carbon nanotubes (SWNTs) according to type (metallic versus semiconducting) has been achieved for HiPco and laser-ablated SWNTs. We presently argue that stable dispersions of SWNTs with octadecylamine (ODA) in tetrahydrofuran (THF) originate from the physisorption and organization of ODA along the SWNT sidewalls in addition to the originally proposed zwitterion model. Furthermore, the reported affinity of amine groups for semiconducting SWNTs, as opposed to their metallic counterparts, contributes additional stability to the physisorbed ODA. This provides a venue for the selective precipitation of metallic SWNTs upon increasing dispersion concentration, as indicated by Raman investigations.     

Solution-processable porous graphitic carbon from bottom-up synthesis and low-temperature graphitization

It is urgently desired yet challenging to synthesize porous graphitic carbon (PGC) in a bottom-up manner while circumventing the need for high-temperature pyrolysis. Here we present an effective and scalable strategy to synthesize PGC through acid-mediated aldol triple condensation followed by low-temperature graphitization. The deliberate structural design enables its graphitization in situ in solution and at low pyrolysis temperature. The resulting material features ultramicroporosity characterized by a sharp pore size distribution. In addition, the pristine homogeneous composition of the reaction mixture allows for solution-processability of the material for further characterization and applications. Thin films of this PGC exhibit several orders of magnitude higher electrical conductivity compared to analogous control materials that are carbonized at the same temperatures. The integration of low-temperature graphitization and solution-processability not only allows for an energy-efficient method for the production and fabrication of PGC, but also paves the way for its wider employment in applications such as electrocatalysis, sensing, and energy storage.

Porous graphitic carbon was synthesized through acid-mediated aldol triple condensation followed by low-temperature graphitization. The inherent thin film processability and the low temperature requirement of the synthesis enable various potential applications.     

Functional macromolecules from single-walled carbon nanotubes: synthesis and photophysical properties of short single-walled carbon nanotubes functionalised with 9,10-diphenylanthracene

9,10-Diphenylanthracene (DPA), a well-studied organic chromophore (Phi(fl) = 0.98) that exhibits electroluminescence, has been covalently bound through 2-(ethylthio)ethylamido linkers to the carboxylic acid groups of short, soluble single-walled carbon nanotubes (sSWNTs) of 1 microm average length, and the resulting DPA-functionalised sSWNT (DPA- sSWNT) macromolecular adducts (4.6 wt % DPA content) characterised by solution (1)H NMR, Raman and IR spectroscopy and thermogravimetric analysis. Comparison of the quenching of DPA fluorescence (steady-state and time-resolved) and of the transient optical spectra of sSWNTs and DPA-sSWNTs show that the covalent linkage boosts the interaction between the DPA and the sSWNT units. DPA-sSWNTs exhibit emission in the near-IR region from 1100-1400 nm with an enhanced quantum yield (Phi = 5.7x10(-3)) compared with sSWNTs (Phi = 3.9x10(-3)).     

Electrochemical synthesis of gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode and their application

Gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode were prepared using electrochemical synthesis method. The thin films of gold Nanoparticles/multi-walled carbon nanotubes were characterized by scanning electron microscopy, powder X-ray diffraction, and cyclic voltammetry. Electrochemical behavior of adrenaline hydrochloride at gold nanoparticles/multi-walled carbon nanotube modified glassy carbon electrode was investigated. A simple, sensitive, and inexpensive method for determination of adrenaline hydrochloride was proposed.     

Efficient H2 adsorption by nanopores of high-purity double-walled carbon nanotubes

DWNT buckypaper adsorbed much more hydrogen than did a SWNT bundle. XRD measurements and GCMC simulation results suggested that the DWNT bundle is loosely packed into an hexagonal array with interstitial pores which can efficiently adsorb H2 molecules.     

One-step water-assisted synthesis of high-quality carbon nanotubes directly from graphite

At 1 atm pressure, high-quality multiwall carbon nanotubes were synthesized directly from graphite in the absence of catalyst by a one-step water-assisted method.     

A low-temperature synthesis of ultraviolet-light-emitting ZnO nanotubes and tubular whiskers

We have successfully synthesized single-crystal ZnO nanotubes and tubular whiskers by employing Zn(NO₃)₂·6H₂O, NH₃·H₂O as the starting materials in the presence of polyethylene glycol (PEG, M_w=2000) at ambient pressure and low temperature (70 °C). Characterizations are carried out by X-ray powder diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM, HRTEM) and photoluminescence (PL) measurement. The results show that the as-prepared ZnO are tubular textures, which have average cross-sectional dimensions of 200-300 nm, lengths of 2-3.5 μm, and wall thickness of 80 nm. These tubular products demonstrate a sharp ultraviolet excitonic emission peak centered at 385 nm at room temperature. A possible growth mechanism and the influence of the reaction temperature on the formation of crystalline ZnO are presented.