Effects of Neodymium on the Properties of Ni‐B/CNTs Amorphous Alloy Catalyst

Neodymium is used as a promoter of Ni‐B/CNTs amorphous alloy catalyst to modify its catalytic properties. Ni‐B/CNTs and Ni‐Nd(5wt%)‐B/CNTs catalysts were prepared by the impregnation chemical reduction method. Their catalytic performances were examined in acetylene selective hydrogenation, which is a crucial step in industrial polymerization processes, with the aim of the complete elimination of alkynes from alkene feedstocks. Experiments showed that the latter exhibited higher acetylene hydrogenation activity but lower ethylene selectivity. Catalysts were characterized by ICP, CO‐chemisorption, XPS, XRD and H₂‐TPD techniques. On the basis of characterizations, the modification of Nd on Ni‐B/CNTs catalyst was related to its geometric and electronic effects.     

MnS hollow microspheres combined with carbon nanotubes for enhanced performance sodium-ion battery anode

MnS as anode material for sodium-ion batteries (SIBs) has recently attracted great attention because of the high theoretical capacity, great natural abundance, and low cost. However, it suffers from inferior electrical conductivity and large volume expansion during the charge/discharge process, leading to tremendous damage of electrodes and subsequently fast capacity fading. To mitigate these issues, herein, a three-dimensional (3D) interlaced carbon nanotubes (CNTs) threaded into or between MnS hollow microspheres (hollow MnS/CNTs composite) has been designed and synthesized as an enhanced anode material. It can effectively improve the electrical conductivity, buffer the volume change, and maintain the integrity of the electrode during the charging and discharging process based on the synergistic interaction and the integrative structure. Therefore, when evaluated as anode for SIBs, the hollow MnS/CNTs electrode displays enhanced reversible capacity (275 mAh/g at 100 mA/g after 100 cycles), which is much better than that of pure MnS electrode (25 mAh/g at 100 mA/g after 100 cycles) prepared without the addition of CNTs. Even increasing the current density to 500 mA/g, the hollow MnS/CNTs electrode still delivers a five times higher reversible capacity than that of the pure MnS electrode. The rate performance of the hollow MnS/CNTs electrode is also superior to that of pure MnS electrode at various current densities from 50 mA/g to 1000 mA/g.     

Synthesis of Heterocyclic Compounds Catalyzed by Metal/Metal Oxide‐Multiwall Carbon Nanotube Nanocomposites

Metal/metal oxide‐decorated multiwalled carbon nanotubes (MWCNTs ) have been found to be effective over various catalysts because of the synergistic, hybrid, physical, and chemical properties of such nanotubes. These properties make them highly active catalytic tools with excellent chemoselectivity, low catalyst loading, and high recyclability of the catalyst. Here, we discuss some recent findings related to the following topics: (1) synthesis of metal/metal oxide‐decorated MWCNTs , (2) characterization techniques of heterogeneous nanocomposites, and (3) application of these metal/metal oxide nanocomposites for the synthesis of heterocyclic compounds. This review emphasizes the main requirements for developing new nanocomposites for the synthesis of pharmaceutically important heterocycles.     

Theoretical studies on the geometrical and electronic structures of supramolecule bis(2,2′-bipyridine)-5-amino-1,10-phenanthroline ruthenium(II)/functionalized SWCNT dyads

Functionalization of carbon nanotube (CNT) with multiple redox and photo active entities is one of the extensive processes due to its importance in building molecular or supramolecular electronic devices, solar energy storage and conversion systems. Thus, to have better understanding about structural aspects and correct electronic structure of these large systems, the quantum studies have gained increased popularity. In present study, we have investigated the structural and electronic properties of functionalized CNTs (fCNTs) with [Ru(bpy)₂(5-NH₂-1,10-phen)]⁺², (Ru-bpy-phen)⁺², supramolecule based on DFT calculations. Main attention has been applied to obtain stable configuration, binding energies and effect of functionalization on electronic behavior of the selected supramolcule. We also evaluate the effect of nanotube’s diameter and chirality on electronic properties of considered supramolecule. Calculated binding energies show that interaction between the (Ru-bpy-phen)⁺² and the host CNTs depends on the tube diameter while the chirality doesn’t affect significantly on the binding nature of respected complex. We have also investigated the influence of non-local dispersion interactions (vdW) and temperature on the stability and electronic structure of the considered system. Results obtained from the ab initio MD simulations showed that increasing the temperature can affect the distance between C and N atoms in the linkage position. The charge analysis indicates the existence of remarkable charge transfer between (Ru-bpy-phen)⁺² as donor and fCNTs as acceptor moieties in the isolated molecule. In the presence of vdW forces and at higher temperature, the charge transfer was decreased but the direction of transferred charge remains unchanged.     

Electrocatalytic reduction of NAD+ at glassy carbon electrode modified with single-walled carbon nanotubes and Ru(III) complexes

A simple procedure was developed to prepare a glassy carbon electrode modified with carbon nanotubes and Ruthenium (III) complexes. First, 25 μl of dimethyl sulfoxide–carbon nanotubes solutions (0.4 mg/ml) was cast on the surface of the glassy carbon electrode and dried in air to form a carbon nanotube film at the electrode surface. Then, the glassy carbon/carbon nanotube-modified electrode was immersed into a Ruthenium (III) complex solution (direct deposition) for a short period of time (10–20 s for multiwalled carbon nanotubes and 20–40 s for single-walled carbon nanotubes). The cyclic voltammograms of the modified electrode in aqueous solution shows a pair of well-defined, stable, and nearly reversible redox couple, Ru(III)/Ru(II), with surface-confined characteristics. The attractive mechanical and electrical characteristics of carbon nanostructures and unique properties and reactivity of Ru complexes are combined. The transfer coefficient (α), heterogeneous electron transfer rate constants (k _s), and surface concentrations (Γ) for the glassy carbon/single-walled carbon nanotubes/Ru(III) complex-, glassy carbon/multiwalled carbon nanotubes/Ru(III) complex-, and glassy carbon/Ru(III) complex-modified electrodes were calculated using the cyclic voltammetry technique. The modified electrodes showed excellent catalytic activity, fast response time, and high sensitivity toward the reduction of nicotinamide adenine dinucleotide in phosphate buffer solutions at a pH range of 4–8. The catalytic cathodic current depends on the nicotinamide adenine dinucleotide concentration. In the presence of alcohol dehydrogenase, the modified electrode exhibited a response to addition of acetaldehyde. Therefore, the main product of nicotinamide adenine dinucleotide electroreduction at the Ru(III) complex/carbon nanotube-modified electrode was the enzymatically active NADH. The purposed sensor can be used for acetaldehyde determination.     

SiO2 coated Fe3O4 magnetic nanoparticle dispersed multiwalled carbon nanotubes based amperometric glucose biosensor

A new type of amperometric glucose biosensor based on silicon dioxide coated magnetic nanoparticle decorated multiwalled carbon nanotubes (Fe₃O₄@SiO₂/MWNTs) on a glassy carbon electrode (GCE) has been developed. MWNTs have been synthesized by catalytic chemical vapour decomposition (CCVD) of acetylene over rare earth (RE) based AB₃ alloy hydride catalyst. The as-grown MWNTs have been purified and further functionlized. Functionalized MWNTs have been decorated with magnetic Fe₃O₄ nanoparticles which have been uniformly coated with biocompatible SiO₂ using a simple chemical reduction method. The characterization of magnetic nanoparticle modified MWNTs have been done by X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), energy dispersive X-ray analysis (EDX) and UV-vis spectroscopy. Amperometric biosensor has been fabricated by the deposition of glucose oxidase (GOD) over Nafion-solubilized Fe₃O₄@SiO₂/MWNTs electrode. The resultant bioelectrode retains its biocatalytic activity and offers fast and sensitive glucose quantification. The performance of the biosensor has been studied using cyclic voltammetry and amperometry and the results have been discussed. The fabricated glucose biosensor exhibits a linear response from 1 μM to 30 mM with an excellent detection limit of 800 nM indicating the potential applications in food industries.     

Preparation of Uniform Ni-B Amorphous Alloy Catalyst on CNTs and its Performance for Acetylene Selective Hydrogenation

Carbon nanotubes (CNTs) are severely bundled and essentially insoluble in solvent. These properties are generally considered as a significant barrier toward the practical uses of CNTs. Therefore, the functionalization and solubilization of CNTs have recei…     

Improvement of field emission properties from screen‐printed CNTs cathodes by heat treatment in a C2H2/H2 gas mixture

We developed a posttreatment method for the screen‐printed carbon nanotubes (CNTs) cathode to improve its field emission characteristics. The treatment was carried out at 500 °C and 20 kPa for 20 min in the atmosphere of C₂H₂/H₂ (volume ratio 1:2). After the treatment, the field emission characteristics were greatly improved. The turn‐on field lowered from 5.0 to 1.6 V/µm, and the emission current density increased from 2 × 10^?4 to 1.0 mA/cm² at the electric field of 2.6 V/µm. In the mean time, the emission site density and uniformity were significantly increased. Scanning electron microscope images revealed that a new top layer of CNTs film has re‐grown on the surface of the printed CNTs cathode during the treatment. This new re‐grown CNTs layer contributes to the drastic enhancement of field emission from the printed cathode. This heat‐treatment technique is very promising for practical application of CNTs in field emission display. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of carbon nanotubes by catalytic vapor decomposition (CVD) method: Optimization of various parameters for the maximum yield

This paper describes an effect of flow rate, carrier gas (H₂, N₂ and Ar) composition, and amount of benzene on the quality and the yield of carbon nanotubes (CNTs) formed by catalytical vapour dcomposition (CVD) method. The flow and mass control of gases and precursor vapors respectively were found to be interdependent and therefore crucial in deciding the quality and yield of CNTs. We have achieved this by modified soap bubble flowmeter, which controlled the flow rates of two gases, simultaneously. With the help of this set-up, CNTs could be prepared in any common laboratory. Raman spectroscopy indicated the possibilities of formation of single-walled carbon nanotubes (SWNTs). From scanning electron microscopy (SEM) measurements, an average diameter of the tube/bundle was estimated to be about 70 nm. The elemental analysis using energy dispersion spectrum (EDS) suggested 96 at.wt.% carbon along with ca. 4 at.wt.% iron in the as-prepared sample. Maximum yield and best quality CNTs were obtained using H₂ as the carrier gas.      

碳纳米管/聚乙烯复合材料薄膜紫外线透过性能的研究

阳光中的紫外线是引起高分子材料老化的最主要因素,高分子材料被紫外线照射后发生一系列的光化学反应,导致材料变色、变脆、透明度下降和力学性能降低,缩短了其使用寿命,长期以来,围绕紫外光对高分子材料老化作用的问题,科学工作者进行了广泛的观测和研究。结果表明,在高