碳纳米管在分离科学中的应用研究进展

碳纳米管(CNTs)作为一种新型纳米材料已在材料、催化、吸附分离等诸多领域得到了广泛的应用。本文对近年来CNTs在分离科学中的应用研究进展进行了简要评述,主要讨论了CNTs在固相萃取、固相微萃取、膜萃取、色谱固定相和毛细管电泳假固定相等方面的应用。     

中空纤维碳纳米管/正辛醇固-液协同微萃取机理及其应用

讨论了以中空纤维为载体的碳纳米管/正辛醇固-液协同微萃取机理,建立了中空纤维碳纳米管/正辛醇固-液协同微萃取-高效液相色谱法同时测定复杂样品中微量咖啡酸、阿魏酸和肉桂酸含量的方法.以2.5 cm长的聚偏氟乙烯中空纤维为碳纳米管正辛醇分散液载体,供相为分析物的HCl(pH 2.1)溶液,接受相为pH 12.7的NaOH溶液,在35℃下,搅拌萃取60 min,萃取液进行高效液相色谱紫外检测.在优化的实验条件下,分析物的线性范围均在0.05～50 μg/L,r＞0.9990 (n=5);检出限均为0.015μg/L;日内与日间精密度均小于9.8％(n=9),平均回收率为93.8％～115.2％;富集倍数分别为514,942和1084倍.在以中空纤维为支持体的碳纳米管/正辛醇微萃取中,碳纳米管/正辛醇分散液嵌入中空纤维管壁上的微孔中形成了碳纳米管/正辛醇固-液微萃取单元束,对苯丙烯酸类化合物起到协同萃取作用.     

固相萃取技术在食品痕量残留和污染分析中的应用

食品痕量残留和污染分析中,样品的前处理极为重要,也是其难点所在。由于食品和农产品样品的多样性和复杂性,目前还没有一种前处理技术能够适合所有情况下的所有样品。本文对近年来发展起来的新型固相萃取技术如固相微萃取、搅拌棒吸附萃取、基质固相分散萃取、分子印迹固相萃取、免疫亲和固相萃取、整体柱固相萃取、碳纳米管固相萃取等在食品痕量残留和污染分析中的应用进行了综述,对未来的发展前景作了展望。     

山药中有机氯杀虫剂的自制碳纳米管探头顶空固相微萃取/气相色谱分析

以碳纳米管为固相涂层,自制萃取探头,顶空固相微萃取/气相色谱分析山药中有机氯杀虫剂六六六和滴滴涕.对萃取温度、萃取时间、样品的稀释度及离子强度等影响萃取效率的因素进行了优化.方法的线性范围为0.5 ～6.0 μg·L-1,相关系数r>0.992 1,检出限(S/N=3)为1.98 ～12.24 ng·L-1,样品加标回收率为70% ～120%,相对标准偏差为1.76% ～18.15%.     

碳纳米管固相微萃取涂层吸附性能研究

利用空气氧化和稀酸回流纯化单壁碳纳米管,用高分辨透射电镜、拉曼光谱对碳纳米管进行了表征.在分子模拟中,非极性氢气、甲烷分子采用单点Lennard-Jones球形分子模型,流体分子与C原子之间相互作用采用虚拟原子模型.以液氮温度下碳纳米管对氮气的吸附等温线实验数据为依据,利用巨正则蒙特卡罗方法模拟得到了碳纳米管的孔径分布,主要集中在6nm.计算了常温常压下碳纳米管中甲烷及氢气的吸附等温线,298K及0.1MPa压力下,氢气的吸附量达到0.015%(质量分数),甲烷在样品中的吸附量可以达到0.5%(质量分数).模拟研究结果表明碳纳米管可以用作固相微萃取涂层材料.     

分析化学中的溶剂萃取技术

综述了近年来溶剂萃取在分析化学中应用的发展趋势。对溶剂萃取所发展的超临界流体萃取、固相萃取、固相微萃取及膜萃取方面作了重点叙述。引用文献35篇。     

新型固相微萃取膜的制备及其在生物检材中毒物提取的应用

用酰胺类化合物和气相色谱固定液制备了一种新型固相微萃取膜,对膜的性质、吸附解吸条件进行了研究;应用该类固相微萃取膜成功地分离了尿液中的吗啡、苯巴比妥以及血液中的敌敌畏,并利用气相色谱-质谱联用技术对分离后的样品进行了分析。     

氧化石墨与石墨烯的制备及其在样品前处理中的应用

石墨烯是继碳纳米管之后出现的新一代碳同素异形体,是碳原子以SP2杂化轨道组成的具有六角形蜂巢晶格结构的二维纳米材料,具有良好的化学稳定性、热稳定性和高比表面积.氧化石墨是用强氧化剂氧化鳞片石墨而获得的石墨衍生物,同样是一层状共价化合物,其表面有丰富的含氧宫能团.近年来,氧化石墨和石墨烯在有机小分子、金属离子和生物大分子分离富集方面的应用已有文献报道.该文简要介绍了氧化石墨以及石墨烯的制备方法,并详细概述了其在固相萃取、固相微萃取、磁性固相萃取、搅拌棒吸附萃取等样品前处理技术中的应用.     

新型固相微萃取膜及其在分析沙土中梯恩梯的应用

本文用酰胺类化舍物和气相色谱固定液制备了一种新型固相微萃取膜，应用该类固相微萃取膜成功地分离了沙土中炸药梯恩梯，并利用气相色谱／质谱联用技术对分离后的样品进行了分析。     

兽药残留分析中样品前处理技术研究进展

样品前处理是兽药残留分析中的关键步骤,直接影响检测的结果.近年来,出现了一些新的样品前处理技术,如固相萃取、基质固相分散萃取、固相微萃取、搅拌棒吸附萃取、膜萃取、液相微萃取、超临界流体萃取、加速溶剂萃取、分子印迹、微波辅助萃取.这些技术能够有效地减少分析过程中由样品前处理过程带来的误差,具有前处理快速、简便的优点,同时可与分析仪器联用,实现分析的自动化.本文对这些新技术的基本原理、特点及在兽药残留分析中的应用进行了综述,并对样品前处理的前景进行了展望.     

Carbon nanotubes: Solid-phase extraction

Since the first report in 1991, carbon nanotubes (CNTs) have shown great possibilities for a wide variety of processes and applications, which include their use as electrodes, sensors (gas, enzymatic, etc.), nanoprobes, electronic materials, field emitters, etc. The combination of structures, dimensions and topologies has provided physical and chemical attractive properties that are unparalleled by most known materials. Their applications have also reached the Analytical Chemistry field in which CNTs are being used as matrices in matrix assisted laser desorption ionization, stationary phases in either gas chromatography, high performance liquid chromatography or capillary electrochromatography, also as pseudostationary phases in capillary electrophoresis, etc. as well as new solid-phase extraction (SPE) materials. Concerning this last application the number of works has considerably increased in the last five years. This review article pretends to focus on the most important features and different applications of SPE using CNTs (including matrix solid-phase dispersion and solid-phase microextraction) covering articles published since their introduction up to now (September 2009).     

Application of carbon nanotubes in extraction and chromatographic analysis: A review

Carbon nanotube (CNT), a well-known carbon-based nanomaterial has drawn much attention in many application fields including chemistry in the last few decades. Many researchers and scientists have shown huge interest to improve the extraction methodologies and adopt their applications in combination with chromatography technique. With respect to this, the exceptional applications of CNTs have been introduced as extraction sorbent due to their excellent inborn physical and chemical properties. In particular, CNTs have consistently been used as adsorbents in various techniques including solid-phase micro-extraction, solid-phase extraction, micro dispersive slid phase extraction, magnetic dispersive solid phase extraction, analytes enrichment, sample fractionation and clean-up as well as support for many derivatization reactions. Many research papers have discussed the successful use of CNTs to overcome the limitations of the extraction techniques due to their excellent sorbent capacity. In addition, considering the clear need to make chromatographic technique more successful, the applications of CNTs have been reported in the literatures in details as stationary and pseudo-stationary phases for the separation and extraction of challenging compounds. Because of the higher thermal and chemical stability, CNTs have been anticipated as stationary phase modifier for chromatographic applications to avoid bleeding of the columns and enable the analysis even at very high temperature (1200 °C). In liquid chromatography CNTs have primarily been used in combination with other packing materials (silica) and sometimes incorporated in a porous polymeric monolith. Therefore, the recent utilizations of CNTs as extraction materials and stationary phases have been illustrated in the current review and a table listing the details applications of CNTs in aforementioned field is provided as well. We believe that the review will help researcher to gain vast knowledge about application of carbon nanotubes in the field of separation chemistry.     

Microenvironment Effects in Electrocatalysis: Ionic‐Liquid‐Like Coating on Carbon Nanotubes Enhances the Pd‐Electrocatalytic Alcohol Oxidation

A new catalyst consisting of ionic liquid (IL)‐functionalized carbon nanotubes (CNTs) obtained through 1,3‐dipolar cycloaddition support‐enhanced electrocatalytic Pd nanoparticles (Pd@IL(Cl^?)‐CNTs) was successfully fabricated and applied in direct ethanol alkaline fuel cells. The morphology, structure, component and stability of Pd@IL(Cl^?)‐CNTs were systematic characterized by transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), Raman spectra, thermogravimetric analysis (TGA) and X‐ray diffraction (XRD). The new catalyst exhibited higher electrocatalytic activity, better tolerance and electrochemical stability than the Pd nanoparticles (NPs) immobilized on CNTs (Pd@CNTs), which was ascribed to the effects of the IL, larger electrochemically active surface area (ECSA), and greater processing performance. Cyclic voltammograms (CVs) at various scan rates illustrated that the oxidation behaviors of ethanol at all electrodes were controlled by diffusion processes. The investigation of the different counteranions demonstrated that the performance of the IL‐CNTs hybrid material was profoundly influenced by the subtly varied structures of the IL moiety. All the results indicated that the Pd@IL(Cl^?)‐CNTs catalyst is an efficient anode catalyst, which has potential applications in direct ethanol fuel cells and the strategy of IL functionalization of CNTs could be available to prepare other carbonaceous carrier supports to enhance the dispersivity, stability, and catalytic performance of metal NPs as well.     

Carbon Nanotubes Supported Pt-Ru-Ni as Methanol Electro-Oxidation Catalyst for Direct Methanol Fuel Cells

Carbon nanotubes (CNTs) supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy (EIS), linear sweep voltammetries (LSV), and chronoamperometry (CA). The results show that the catalysts exhibit face-centered cubic (fcc) structure. The particle size of Pt-Ru-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.     

管径对碳纳米管负载铂催化剂氧还原的影响

A series of nanocatalysts consisting of acid treated carbon nanotubes (CNTs) with different diameters (8-15, 20-30, 30-50, >50 nm) supporting platinum (Pt) nanoparticles (Pt/CNTs) were synthesized via a microwave-assisted ethylene glycol method. The as-synthesized catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Their catalytic performances in the oxygen reduction reaction (ORR) were evaluated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The experimental results showed that the diameter of the CNTs influences the particle size, loading, and dispersion of Pt NPs. Furthermore, the Pt/CNTs having different CNT diameters displayed different catalytic activities in the ORR. The catalyst Pt/CNT₈, which was prepared by using CNTs with diameters ranging between 8-15 nm as the support, exhibited the highest Pt loading, catalytic activity, and stability in the ORR. The mass activity of Pt/CNT₈ was determined to be 0.188 A·mg^-1 at 0.9 V, which is folds higher than that of the commercially available JM Pt/C catalyst. After testing the stability for 5000 potential cycles, the negative shift (~7 mV) of the half-wave potential for Pt/CNT₈ was found to be significantly lesser than that for the JM Pt/C catalyst (~32 mV), indicating superior catalytic stability.     

Enhanced stability of Pt electrocatalysts by nitrogen doping in CNTs for PEM fuel cells

Electrochemical stabilities of Pt deposited on carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (CN_x) of different nitrogen contents are compared with accelerated durability tests (ADT) for the first time. Transmission electron microscopy (TEM) images reveal the different structures of CNTs and CN_x, and the decrease of Pt particle size with the nitrogen incorporation into CNTs. Based on the loss of electrochemical surface area (ESA) and TEM images, Pt/CN_x exhibited much higher stability than Pt/CNTs, and the Pt stability increases with the increase of nitrogen contents in the CN_x supports.     

Preparation and characterization of carbon nanotubes-polymer/CdSe hybrid nanocomposites through combining electrostatic adsorption and ATRP technique

This paper describes a new strategy through noncovalent functionalization of multi-walled carbon nanotubes (MWNTs) by a kind of new copolymer Polyethyleneimine-graft-Polyacrylonitrile for attaching CdSe nanoparticles onto the MWNTs to fabricate Carbon Nanotube/CdSe heterostructures. Polyethyleneimine (PEI), an amino-rich cationic polyelectrolyte, can interact with the MWNTs through electrostatic interaction. Then, CNT/PEI-g-PAN was successfully prepared by in situ atom transfer radical polymerization (ATRP), which did not introduce defects to the structure of CNTs. Thus, CdSe nanoparticles can be covalently coupled to functionalized carbon nanotubes (CNTs) in a uniform and controllable manner. Moreover, this method ensures good dispersion and high stability in any commonly used organic or inorganic solvent. In this manner, our strategy allows the attachment of various colloidal nanoparticles to CNTs, independent of their surface properties, i.e. hydrophilic or hydrophobic. TEM, XRD, EDS and FT-IR are all used to characterize the CNT/CdSe composite materials. In addition, the optical properties are investigated by UV–vis spectrum.     

Fabrication of Tiron Doped Poly-Pyrrole/Carbon Nanotubes on Low Resistance Monolayer-Modified Glassy Carbon Electrode for Selective Determination of Dopamine

In this paper, we described a novel sensor based on tiron-doped polypyrrole and carbon nanotubes (CNTs) fabricated on low resistance monolayer-modified glassy carbon electrode. First, the dodecylamine monolayer was chemically modified. Second, CNTs were controllably adsorbed onto dodecylamine. Then, tiron doped polypyrrole was electro-deposited on the CNTs film. The layer-by-layer modified electrode was sensitive to dopamine, while it made no response to even high concentration of ascorbic acid. Parameters influencing the dopamine response were optimized. High performance of the sensor was obtained, such as wide concentration range, low detection limit (3 nM), low background current, high stability, and reproducibility.     

不同结构碳纳米管的电磁波吸收性能研究

研究了单壁、多壁碳纳米管(聚团状、阵列状)以及未纯化与纯化后碳纳米管在2～18 GHz范围内的电磁波吸收性能. 通过测定不同结构碳纳米管粉体的介电常数以及磁导率, 得到损耗因子及衰减常数大小顺序为: 阵列状多壁碳纳米管>原生聚团状多壁碳纳米管>纯化聚团状多壁碳纳米管>原生单壁碳纳米管>纯化后单壁碳纳米管. 相比多壁碳纳米管, 单壁碳纳米管衰减常数随频率变化较小, 且具有较宽的吸收峰. 模拟计算和实验测试结果都表明, 碳纳米管/聚合物复合材料具有优良的电磁吸波性能.     

Significant improvements in mechanical property and water stability of chitosan by carbon nanotubes

In this work, high storage modulus and high water stability of chitosan was prepared by incorporating chitosan-grafted carbon nanotubes (CNTs-g-CS). This dramatically improved mechanical property and water stability of chitosan would broaden its biochemical and electrochemical applications. The methodology adopted here by incorporating the CNTs-g-CS allowed a high amount of CNTs incorporation in chitosan without phase separations and enabled the preparations of a durable chitosan/CNTs nanocomposite-modified electrode for biosensor uses. The CNTs-g-CS was synthesized by grafting chitosan onto the carboxylated CNTs in acetic acid-added aqueous solution at 98 °C for 24 h. Thermal gravimetric analysis showed that the content of the chitosan grafts on the CNTs was about 25 wt% of the synthesized CNTs-g-CS. As compared with the ungrafted CNTs, the CNTs-g-CS exhibited a significantly improved dispersion in the chitosan matrix, as examined by optical microscopy and scanning electron microscopy, resulting in significantly improved storage modulus and water stability of the chitosan nanocomposites as revealed by dynamic mechanical analysis and water treatments data, respectively. The storage modulus was significantly up by 134% from 6.4 GPa for the pure chitosan to 15 GPa for the chitosan nanocomposite containing 40 wt% CNTs-g-CS. The water stability of the chitosan nanocomposite films was significantly up from less than 12 h for the chitosan containing various amounts of ungrafted CNTs to at least 48 h for the chitosan containing 20, 30, and 40 wt% CNTs-g-CS.