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.     

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.     

Effect of niobium promoter on iron-based catalyst for Fischer-Tropsch reaction

Niobium-promoted Fe/CNTs catalysts were prepared using a wet impregnation method.Samples were characterized by nitrogen adsorption,H2-TPR,TPD,XRD and TEM.The Fischer-Tropsch Synthesis(FTS) was carried out in a fixed-bed microreactor at 220 ℃,1 atm and H2/CO=2 for 5 h.Addition of niobium into Fe/CNTs increased the dispersion,decreased the average size of iron oxide nanoparticles and the catalyst reducibility.Niobium-promoted Fe catalyst resulted in appreciable increase in the selectivity of C5+ hydrocarbons and suppressed methane formation.These effects were more pronounced for the 0.04%Nb/Fe/CNTs catalyst,compared to those observed from other niobium compositions.The 0.04%Nb/Fe/CNTs catalyst enhanced the C5+ hydrocarbons selectivity by a factor of 67.5% and reduced the methane selectivity by a factor of 59.2%.     

Recent developments and applications of screen-printed electrodes in environmental assays—A review

Screen-printed electrodes (SPEs), which are used as economical electrochemical substrates, have gone through significant improvements over the past few decades with respect to both their format and their printing materials. Because of their advantageous material properties, such as disposability, simplicity, and rapid responses, SPEs have been successfully utilised for the rapid in situ analysis of environmental pollutants. This critical review describes the basic fabrication principles, the configuration designs of SPEs and the hybrid analytical techniques based on SPEs. We mainly overview the electrochemical applications of SPEs in environmental analysis over the past 3 years, including the determination of organic compounds, heavy metals and gas pollutants.     

Synthesis and characterization of magnetic Fe/CNTs composites with controllable Fe nanoparticle concentration

Fe/CNTs composites, with different concentrations of Fe nanoparticles (NPs) on carbon nanotube (CNT) surfaces, were successfully fabricated via a facile solvothermal method. The lengths of CNTs are up to 10 μm and the mean diameter of the Fe nanoparticles is about 25 nm. The structures, composition and magnetic properties of the Fe/CNTs were characterized by XRD, FTIR, FE-SEM, TEM and PPMS. We found that the concentrations of Fe nanoparticles depositing on the CNTs could be controlled by adjusting the initial mass ratio of ferrocene to CNTs. The Fe/CNTs composites display good ferromagnetic properties at room temperature, with a saturation magnetization of 125 emu/g-Fe and a coercivity of 276 Oe. The Curie temperature of the sample is about 1038 K, slightly lower than that (1043 K) of the bulk iron.     

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.     

处理方法对多壁碳纳米管结构及负载Ru催化剂氨分解反应活性的影响

分别用H2O2、强碱（NaOH、KOH）和HNO3处理CNTs。以处理后的CNTs为载体、通过浸渍RuCl3水溶液结合高温H2还原制备Ru/CNTs催化剂,并将其应用在氨分解催化反应中。利用XRD、TPR、TPD-MS表征手段研究了Ru在CNTs表面的分散、还原性能及CNTs表面化学基团,探究催化剂结构-性能间构效关系。结果表明,强碱及双氧水处理CNTs,为其表面引入了数量适宜的羧基、酸酐、酚等官能团,而传统硝酸处理则引入了大量的羧基、酸酐、酯、内酯、酚、醌和羰基等官能团,对CNTs本征结构性质影响很大。经强碱及双氧水处理CNTs上负载Ru后所得催化剂的效果明显优于传统硝酸处理CNTs上负载Ru催化剂。本研究为CNTs的新型处理方法、表面化学官能团分析、提高Ru/CNTs催化分解氨活性提供了新的思路。     

Exposure to nanoscale particles and fibers during machining of hybrid advanced composites containing carbon nanotubes

This study investigated airborne exposures to nanoscale particles and fibers generated during dry and wet abrasive machining of two three-phase advanced composite systems containing carbon nanotubes (CNTs), micron-diameter continuous fibers (carbon or alumina), and thermoset polymer matrices. Exposures were evaluated with a suite of complementary instruments, including real-time particle number concentration and size distribution (0.005–20 μm), electron microscopy, and integrated sampling for fibers and respirable particulate at the source and breathing zone of the operator. Wet cutting, the usual procedure for such composites, did not produce exposures significantly different than background whereas dry cutting, without any emissions controls, provided a worst-case exposure and this article focuses here. Overall particle release levels, peaks in the size distribution of the particles, and surface area of released particles (including size distribution) were not significantly different for composites with and without CNTs. The majority of released particle surface area originated from the respirable (1–10 μm) fraction, whereas the nano fraction contributed ~10% of the surface area. CNTs, either individual or in bundles, were not observed in extensive electron microscopy of collected samples. The mean number concentration of peaks for dry cutting was composite dependent and varied over an order of magnitude with highest values for thicker laminates at the source being >1 × 10⁶ particles cm⁻³. Concentration of respirable fibers for dry cutting at the source ranged from 2 to 4 fibers cm⁻³ depending on the composite type. Further investigation is required and underway to determine the effects of various exposure determinants, such as specimen and tool geometry, on particle release and effectiveness of controls.

贵金属纳米粒子修饰碳纳米管的研究

碳纳米管具有独特的一维管状结构和优异的电、光、热和力学性能,是药物和纳米催化剂的理想载体。将具有独特光、电、磁和催化性能的贵金属纳米粒子负载在碳纳米管的表面,形成的碳纳米管/贵金属纳米粒子复合物不仅兼有两种纳米材料的优异性能,还可能产生新的特性,在催化、储能、燃料电池、电子器件和传感器等领域均有广阔的应用前景。本文主要从共价修饰和非共价修饰两种策略出发,综述了贵金属纳米粒子修饰碳纳米管的制备方法和研究进展。其中用天然高分子包覆的碳纳米管表面具有很好的贵金属配位结合能力,得到的纳米复合物具有良好的水分散性和生物相容性,在载药、生物传感器和肿瘤诊断治疗等生物领域具有明显的优势。     

大孔径碳纳米管的制备

采用共沉淀-凝胶法制备Ni—Cu—Al催化剂,以甲烷为气源利用化学气相沉积法制备内径为25-50nm的大孔径碳纳米管,研究了催化剂制备条件、反应温度以及反应气流速对碳纳米管和碳产率的影响。结果表明,甲烷流速为480～500mL／min,甲烷裂解温度为973K,在823K空气气氛下焙烧的催化剂用于制备碳纳米管得到的产量大于10g／次。