大面积多壁碳纳米管薄膜光电响应实验

为了研究大面积多壁碳纳米管(MWNTs)的光电响应特性,利用剥离技术和旋涂法制备了大 面积MWNTs薄膜器件;采用532nm激光作为激励光源,当激光照射薄 膜器件不同位置时,测试其光电流和光电 压。实验结果表明,激光诱导产生的光电流/电压与光照位置有关,当光照位置在器件两端 时,光电流、光电压 最大,两端的光电流分别为0.04μA、－0.06μA和光电压分别为0.04mV、－0.06mV; 当激光照射在器件几 何中心时,光电流、光电压趋于0。分析表明,光热电效应是光电流、电压产生和变化的主 要原因。     

PPy-MWNTs复合材料制备条件与结构性能的关系

探讨聚吡咯/多壁碳纳米管(PPy/MWNTs)纳米复合材料的原位化学制备。利用FT-IR、XRD、元素分析对不同复合比例的材料组成进行分析;经SEM对复合材料形态、管径等进行表征,认为水/醇介质有利于获得管状的核-壳结构复合材料;研究氧化剂、掺杂酸等因素对复合材料电导率的影响。     

Ag/MWNTs-羊毛抗菌功能化纤维的结合机理研究

以自制Ag/MWNTs抗菌剂为功能材料,采用紫外光辐照的方法制备了抗菌Ag/MWNTs-羊毛纤维。运用场发射扫描电镜、傅里叶红外光谱仪等对样品的形貌和结构进行了表征,同时表征了抗菌处理前后羊毛纤维的品质特征。研究结果表明羊毛纤维与具有良好抗菌功能的Ag/MWNTs抗菌剂紧密复合并通过偶联剂的架桥作用,在羊毛纤维表面形成以价键形式结合的抗菌层。与原羊毛相比,抗菌Ag/MWNTs-羊毛纤维长度较长,细度变细,卷曲回复率较高。     

Conducting polymer coated carbon surfaces and biosensor applications

This review article focuses on several approaches in the characterization and modification of carbon surfaces with electrocoated thin films which has been realized by recent progress in experimental methods. Electropolymerization and electrocopolymerization of π-conjugated polymers (pyrrole, carbazole, N-vinylcarbazole and aniline) onto carbon surfaces are reviewed with 348 references. Particular emphasis is placed on the recent nanoscale surface characterization techniques applied to the resulting electrocoated polymers onto carbon fibers (i.e., scanning electron microscopy (SEM), cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), focused ion beam-secondary ion mass spectroscopy (FIB-SIMS), Fourier transformed infrared spectroscopy (reflectance-FTIR), and Raman spectroscopic measurements).     

碳纳米管/环氧树脂复合材料力学性能影响因素的研究

本文研究了碳纳米管在环氧树脂中的分散方式及碳纳米管长度对环氧树脂复合材料力学性能的影响,并对单壁与多壁碳纳米管分别制备的环氧树脂复合材料的力学性能进行了分析探讨。本实验条件如下:搅拌时间为8h时复合材料的冲击强度、拉伸强度和弯曲强度分别可比1h时增加41%、22%和38%;超声波处理时间为4h时复合材料的冲击强度、拉伸强度和弯曲强度分别可比处理1h时增加143%、30%和45%,但超声波处理时间不宜过长,否则会破坏碳纳米管表面,导致性能下降。短碳纳米管在环氧树脂中的分散性较好,对环氧树脂复合材料的增强效果较好。长碳纳米管对提高复合材料的韧性有利。与长度为50μm时相比,碳纳米管长度为2μm时制备的环氧树脂复合材料的拉伸强度和弯曲强度高49.2%和45.3%,但断裂伸长率低33%。与单壁碳纳米管相比,多壁碳纳米管与环氧树脂的界面结合力更好,更适于做环氧树脂增韧材料。相同实验条件下多壁碳纳米管/环氧树脂复合材料的冲击强度、断裂伸长率和拉伸强度较单壁碳纳米管/环氧树脂复合材料可分别提高31%、24%和28%。     

小分子壳聚糖非共价修饰多壁碳纳米管及其在水中的稳定性研究

采用溶液共混法制备了多壁碳纳米管-壳聚糖(MWNTs-CS)复合物,用透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FT-IR)和紫外可见分光光度计(UV-VIS)对产物进行了表征和分析,讨论溶液温度和pH值对MWNTs-CS稳定性的影响.研究表明,壳聚糖成功地修饰到碳纳米管表面,部分缠绕MWNTs,而MWNTs本身结构没有发生改变,并且MWNTs-CS在水中的溶解性得到了很大的提高.随着溶液温度的增加和pH值的减少,壳聚糖可以从MWNTs-CS上释放.在溶液温度为20℃以及pH值为10时,壳聚糖的修饰效率较高.     

Thermal behaviour of multi-walled carbon nanotube/polymer composites using lattice Boltzmann method

A three-dimensional computational model was developed to study the thermal behaviour of multi-walled carbon nanotube (MWNT)-polymer composites. A lattice Boltzmann algorithm has been introduced to tackle the conjugate heat transfer among different phases. The model was validated by comparing with the theoretical solutions and simulation results. The effects of the orientation, volume fraction and diameter of MWNTs on the effective thermal conductivity (λ_e) of composites were quantified. It is found that the effective thermal conductivity of the composites weakens with the variation of MWNTs orientation angle, and the decrease extent deduces gradually. Moreover, with the same orientation angle, the λ_e of the composites increases with the volume fraction of MWNTs. It also indicates that MWNTs with a small diameter at a constant volume fraction can promote the thermal conductivity of the composites more efficiently than that with a larger diameter.     

Delivery of small interfering RNAs in human cervical cancer cells by polyethylenimine-functionalized carbon nanotubes

Carbon nanotubes are capable of penetrating the cell membrane and are widely considered as potential carriers for gene or drug delivery. Because the C-C and C=C bonds in carbon nanotubes are nonpolar, functionalization is required for carbon nanotubes to interact with genes or drugs as well as to improve their biocompatibility. In this study, polyethylenimine (PEI)-functionalized single-wall (PEI-NH-SWNTs) and multiwall carbon nanotubes (PEI-NH-MWNTs) were produced by direct amination method. PEI functionalization increased the positive charge on the surface of SWNTs and MWNTs, allowing carbon nanotubes to interact electrostatically with the negatively charged small interfering RNAs (siRNAs) and to serve as nonviral gene delivery reagents. PEI-NH-MWNTs and PEI-NH-SWNTs had a better solubility in water than pristine carbon nanotubes, and further removal of large aggregates by centrifugation produced a stable suspension of reduced particle size and improved homogeneity and dispersity. The amount of grafted PEI estimated by thermogravimetric analysis was 5.08% (w/w) and 5.28% (w/w) for PEI-NH-SWNTs and PEI-NH-MWNTs, respectively. For the assessment of cytotoxicity, various concentrations of PEI-NH-SWNTs and PEI-NH-MWNTs were incubated with human cervical cancer cells, HeLa-S3, for 48 h. PEI-NH-SWNTs and PEI-NH-MWNTs induced cell deaths in a dose-dependent manner but were less cytotoxic compared to pure PEI. As determined by electrophoretic mobility shift assay, siRNAs directed against glyceraldehyde-3-phosphate dehydrogenase (siGAPDH) were completely associated with PEI-NH-SWNTs or PEI-NH-MWNTs at a PEI-NH-SWNT/siGAPDH or PEI-NH-MWNT/siGAPDH mass ratio of 80:1 or 160:1, respectively. Furthermore, PEI-NH-SWNTs and PEI-NH-MWNTs successfully delivered siGAPDH into HeLa-S3 cells at PEI-NH-SWNT/siGAPDH and PEI-NH-MWNT/siGAPDH mass ratios of 1:1 to 20:1, resulting in suppression of the mRNA level of GAPDH to an extent similar to that of DharmaFECT, a common transfection reagent for siRNAs. Our results indicate that the PEI-NH-SWNTs and PEI-NH-MWNTs produced in this study are capable of delivering siRNAs into HeLa-S3 cells to suppress gene expression and may therefore be considered as novel nonviral gene delivery reagents.     

Fundamentals, processes and applications of high-permittivity polymer-matrix composites

There is an increasing need for high-permittivity (high-k) materials due to rapid development of electrical/electronic industry. It is well-known that single composition materials cannot meet the high-k need. The combination of dissimilar materials is expected to be an effective way to fabricate composites with high-k, especial for high-k polymer-matrix composites (PMC). This review paper focuses on the important role and challenges of high-k PMC in new technologies. The use of different materials in the PMC creates interfaces which have a crucial effect on final dielectric properties. Therefore it is necessary to understand dielectric properties and processing need before the high-k PMC can be made and applied commercially. Theoretical models for increasing dielectric permittivity are summarized and are used to explain the behavior of dielectric properties. The effects of fillers, fabrication processes and the nature of the interfaces between fillers and polymers are discussed. Potential applications of high-k PMC are also discussed.     

Cytotoxicity of Phenol Red in Toxicity Assays for Carbon Nanoparticles

To explore the novel properties of carbon nanoparticles (CNPs) in nanotoxicity assays, the adsorption of phenol red (a pH indicator for culture medium) by multi-walled carbon nanotubes (MWNTs) and three kinds of carbon blacks (CBs) with nanosize, and its effects on cytotoxicity were studied. Results indicated that the phenol red adsorbed and delivered into cells by CBs was responsible for the toxicity to Hela cells in the medium without serum. The cellular uptake of phenol red was verified using ¹²⁵I-labeling techniques. The size-dependent cytotoxicity of CBs was found to closely correlate to adsorption of phenol red, cellular uptake of phenol red-CB complexes and the amount of phenol red delivered into the cells by CBs. Although the CBs were either nontoxic or slightly toxic, as vehicles of phenol red, they played an essential role in the cytotoxicity induced by phenol red. However, MWNTs showed an intrinsic cytotoxicity independent of phenol red. The implications associated with these findings are discussed.