Study of carbon nanotubes and functionalized-carbon nanotubes as substrates for flow injection solid phase extraction associated to inductively coupled plasma with ultrasonic nebulization: Application to Cd monitoring in solid environmental samples

A research was performed to evaluate the capabilities of carbon nanotubes (CNTs) and modified CNTs to serve as sorbents for preconcentrating Cd together with on-line ultrasonic nebulization (USN)-inductively coupled plasma optical emission spectrometry (ICPOES). Three different carbon nanotubes sustrates namely, carbon nanotubes (CNTs), oxidized-carbon nanotubes (ox-CNTs) and l-alanine-carbon nanotubes (ala-CNTs) were studied systematically and the main factors influencing the preconcentration and determination of Cd were examined thoroughly. The CNTs evaluated showed dissimilar adsorption behaviors leading to increasing preconcentration factors when used in the proposed on-line solid phase extraction (SPE) system as follows: CNT < ala-CNT < ox-CNT. Aiming to achieve the best analytical performance, ox-CNTs were used as they enable quantitative retention of Cd at pH 7.0 and instantaneous elution of the analyte with 10% HNO₃. Under optimal conditions, the adsorption capacity on ox-CNTs was found to be 130 μmol g^?1 and the detection limit (3σ) achieved was 1.03 μg L^? 1. The precision of the method expressed as the relative standard deviation (RSD) turned to be 3.0%. The flow injection method involving use of ox-CNTs as sorbent and USN-ICPOES for detection was successfully applied to the determination of Cd in different kinds of environmental samples.     

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     

Direct Determination of Bacterial Cell Viability Using Carbon Nanotubes Modified Screen‐printed Electrodes

For the early detection of bacterial infection, there is a need for rapid, sensitive, and label‐free assays. Thus, in this study, nanostrucured microbial electrochemical platform is designed to monitor the viability and cell growth of S. aureus. Using multi‐walled carbon nanotube modified screen‐printed electrodes (MWCNTs/SPE), the cyclic voltammetric measurements showed only one irreversible oxidation peak at 600 mV vs Ag/AgCl that accounts for the viable and metabolically active bacterial cells. The assay was optimized and the secreted metabolites, in the extracellular matrix, were directly detected. The peak current showed a positive correlation with viable cell numbers ranging from OD_{600 nm} of 0.1 to 1.1, indicating that the activity of live cells can be quantified. Consequently, responses of viable and non‐viable cells of S. aureus to the effects of antibiotic and respiratory chain inhibitors were determined. Thus, the proposed nanostructure‐based bacterial sensor provides a reasonable and reliable way for real‐time monitoring of live‐dead cell functions, and antibacterial profiling.     

Synthesis of Higher Alcohols from Syngas over Alkali Promoted K-Co-Mo Catalysts Supported on Multi-walled Carbon Nanotubes

A series of carbon nanotubes-supported K-Co-Mo catalysts were prepared by a sol-gel method combined with incipient wetness impregnation.The catalyst structures were characterized by X-ray diffraction,N₂ adsorption-desorption,transmission electron microscopy and H₂-TPD,and its catalytic performance toward the synthesis of higher alcohols from syngas was investigated.The as-prepared catalyst particles had a low crystallization degree and high dispersion on the outer and inner surface of CNTs.The uniform mesoporous structure of CNTs increased the diffusion rate of reactants and products,thus promoting the reaction conversion.Furthermore,the incorporation of CNTs support led to a high capability of hydrogen absorption and spillover and promoted the formation of alkyl group,which served as the key intermediate for the alcohol formation and carbon chain growth.Benefiting from these characteristics,the CNTs supported Mo-based catalyst showed the excellent catalytic performance for the higher alcohols synthesis as compared to the unsupported catalyst and activated carbon supported catalyst.     

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.     

Synthesis,stereocomplex crystallization and properties of poly(l‐lactide)/four‐armed star poly(d‐lactide) functionalized carbon nanotubes nanocomposites

Functionalized carbon nanotubes (F‐CNTs) were synthesized through the nucleophilic substitution reaction between four‐armed star poly(d ‐lactide) (4PDLA) and acryl chloride of carbon nanotubes and were characterized using Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and thermogravimetric analysis. The results indicated that the 4PDLA was successfully grafted onto carbon nanotubes, and it contained 45.5 wt% of 4PDLA. Poly(l ‐lactide) (PLLA) nanocomposites with different F‐CNTs content were prepared by solution casting. Optical microscopy and scanning electron microscopy results showed that F‐CNTs were uniformly dispersed in the nanocomposites. Crystallization behavior and crystal structure of PLLA nanocomposites were investigated using differential scanning calorimetry, polarizing microscope and X‐ray diffraction. The results found that poly(lactide) stereocomplex crystal could be formed between PLLA and F‐CNTs. F‐CNTs played different roles in the process of solution casting and melting crystallization. Polarizing microscope also revealed that crystallization temperature had a significant effect on the nucleation and spherulites growth of PLLA. Thermal stability and mechanical properties of the nanocomposites were also investigated by thermogravimetric analysis, dynamic mechanical analysis and tensile testing. These results demonstrated that the addition of F‐CNTs obviously improved thermal stability and tensile strength of PLLA. The results showed that PLLA/F‐CNTs would have potential values in engineering fields. Copyright © 2015 John Wiley & Sons, Ltd.     

尼龙/碳纳米管复合材料研究进展

碳纳米管(CNTs)由于其独特的结构,较高的长径比,较大的比表面积,且具有超强的力学性能和良好的导热性,已经证明是塑料的非常优异的导电填料,聚合物基碳纳米管复合材料可望应用于材料领域的多个方面,尤其在汽车、飞机及其它飞行器的制造等军事和商业应用上带来革命性的突破。本文介绍了碳纳米管的结构形态和碳纳米管的制备、纯化、修饰方法及聚合物基碳纳米管复合材料的制备、性能,并综述了近几年来尼龙/碳纳米管复合材料的研究进展及应用前景。     

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.     

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.