基于原子转移自由基聚合法制备多壁碳纳米管/Ag复合材料

在多壁碳纳米管(MWNT)表面键接可用于原子转移自由基聚合(ATRP)的引发剂,并以此引发甲基丙烯酸缩水甘油酯(GMA)在MWNT表面的ATRP.利用红外光谱(FT-IR)、核磁共振(<'1>H-NMR)和透射电镜(TEM)对接枝聚合物MWNT的结构和外观形貌进行了研究.接枝在MWNT表面的PGMA与过量的乙二胺发生开...     

Selective Formation of Metal Nanoparticles on the Sidewalls of Carbon Nanotubes

Pt and Au nanoparticles spontaneously form on the sidewalls of single-walled carbon nanotubes (SWNTs) and multiwall carbon nanotubes (MWNTs) in a selective manner. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies reveal that metal ions are first absorbed on the sidewalls of carbon nanotubes (CNTs) and then are reduced by ethanol. This mechanism is tentatively proposed and discussed.     

Preparation of water-soluble multi-walled carbon nanotubes by polymer dispersant assisted exfoliation

Water-soluble multi-walled carbon nanotubes (MWNTs) with a high solubility of 29.2?mg?ml(-1) were obtained by polymer dispersant hydrolyzed poly(styrene-co-maleic anhydride) (HSMA) assisted exfoliation and centrifugation. The MWNTs were exfoliated and dispersed in aqueous solution by non-covalent modification with polymer dispersant of HSMA. Characterizations of HSMA-coated MWNTs were conducted via transmission electron microscopy (TEM), UV-vis and fluorescence spectroscopy, and thermal gravimetric analysis (TGA). The as-prepared HSMA-coated MWNTs showed good dispersibility and stability in water.     

化学气相沉积法制备多壁碳纳米管

以带程序升温装置的管式电阻炉为实验装置,采用化学气相沉积法,在一定的工艺条件下裂解二茂铁与双鸭山精煤的混合物制备出多壁碳纳米管.采用透射电镜、Raman光谱以及X射线衍射技术对碳纳米管产物进行表征,同时研究了碳纳米管的生长机理.     

多壁碳纳米管在硫酸溶液中的γ辐射剪切

在硫酸溶液中系统地研究了γ辐射法剪切多壁碳纳米管,以及影响碳管长度的反应条件,详细讨论了多壁碳纳米管的剪切机理.采用透射电子显微镜(TEM)、傅立叶变换红外光谱(FT-IR)、紫外可见分光光度计(UV-Vis)和Raman光谱对短多壁碳纳米管进行了分析与表征,分析了多壁碳纳米管浓度与其对UV270nm吸光度的关系,得出了多壁碳纳米管质量浓度与其对UV270nm吸光度的线性回归方程.结果表明,γ辐射和硫酸氧化作用在剪切多壁碳纳米管的过程中存在协同效应.随着辐射剂量和酸浓度的增加,剪切后的碳管长度不断缩短.当辐射剂量增加到200kGy、酸浓度为5mol/L时,短多壁碳纳米管长度为200～300nm.辐射剪切的方法在碳纳米管外侧及末端引进C-OH、-COOH等官能团,从而对MWNTs的石墨型结构造成微弱损伤.另外,制备的短多壁碳管在水中可以均匀分散2周而不出现沉淀.     

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.     

Synthesis and thermoelectric power of nitrogen-doped carbon nanotubes

We have previously shown that high-purity multiwalled carbon nanotubes (pristine MWNTs) can be prepared from a mixture of xylene-ferrocene (99 at% C:1 at% Fe) inside a quartz tube reactor operating at approximately 700 degrees C. In a similar process, approximately 3 g of melamine (C3H6N6) was introduced during the growth of MWNTs to prepare nitrogen-doped nanotubes. The structural and electronic properties of nitrogen-doped MWNTs were determined by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and thermopower measurements. The individual nitrogen-doped nanotube exhibits a bamboo-like structure and comprises 6-16 tube walls, as evidenced by HRTEM studies. The EELS measurements yielded an average nitrogen content of approximately 5 at% in the doped tubes. The thermoelectric power data of nitrogen-doped MWNTs remained negative even after exposure to oxygen for an extended period of time, suggesting that nitrogen doping of MWNTs renders them n-type, consistent with scanning tunneling spectroscopic studies on similar nanotubes.     

Effects of high-energy ball milling on the morphology and the field emission property of multi-walled carbon nanotubes

The effects of grinding time in a vibration mill on the morphology and the field emission property of multi-walled carbon nanotubes (MWNTs) were studied using XRD, Raman spectra and high-resolution transmission electron microscopy (HRTEM). The results show that the closed ends of MWNTs are partly broken when ground for 4 h. The number of broken ends increases with grinding time. The field emission measurement results indicate that the presence of Fe particles can improve the field emission property of ground MWNTs.     

pH-controlled carbon nanotube aggregation/dispersion based on intermolecular i-motif DNA formation

In this work, we report a new strategy to manipulate the aggregation and dispersion of carbon nanotube in solution via formation of intermolecular i-motif (four-stranded C-quadruplex) structures in a pH dependent manner. Firstly, single-stranded (ss) DNAs containing two stretches of cytosine (C)-rich domains are covalently linked to carbon nanotubes. At pH 8.0, DNAs are at random coil state, which enhance the dispersion of multi-wall carbon nanotubes (MWNTs) in water; after changing pH to 5.0, the intermolecular i-motif structures formed by the C-rich ssDNAs on neighboring carbon nanotube could drive the MWNTs aggregate. This process is reversible and the transition process has been verified by circular dichroism (CD) spectroscopy, gel electrophoresis and transmission electron microscopy (TEM). Considering the mechanical properties of carbon nanotube, this finding will benefit many application research fields, such as artificial muscle, functional nano-devices and so on.     

Multi-walled carbon nanotubes coated with rare earth fluoride EuF3 and TbF3 nanoparticles

EuF₃ and TbF₃ were successfully coated on the multi-walled carbon nanotubes (MWNTs) via the intermediate of noncovalent hydrophobic interactions of the MWNTs surface with sodium dodecyl sulfate (SDS). They were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The nanoparticle sizes of rare earth fluorides on MWNTs are less than 10 nm. The photophysical properties of the composites were investigated, which indicated the rare earth fluorides/MWNTs composites exhibited the optical transitions within the 4f shell of the rare earth ions.     

Synthesis of nano-carbon (nanotubes,nanofibres, graphene) materials

In the present study, we report the synthesis of carbon nanotubes (CNTs) using a new natural precursor: castor oil. The CNTs were synthesized by spray pyrolysis of castor oil-ferrocene solution at 850°C under an Ar atmosphere. We also report the synthesis of carbon nitrogen (C-N) nanotubes using castor oil-ferrocene-ammonia precursor. The as-grown CNTs and C-N nanotubes were characterized through scanning and transmission electron microscopic techniques. Graphitic nanofibres (GNFs) were synthesized by thermal decomposition of acetylene (C₂H₂) gas using Ni catalyst at 600°C. As-grown GNFs reveal both planar and helical morphology. We have investigated the structural and electrical properties of multi-walled CNTs (MWNTs)-polymer (polyacrylamide (PAM)) composites. The MWNTs-PAM composites were prepared using as purified, with ball milling and functionalized MWNTs by solution cast technique and characterized through SEM. A comparative study has been made on the electrical property of these MWNTs-PAM composites with different MWNTs loadings. It is shown that the ball milling and functionalization of MWNTs improves the dispersion of MWNTs into the polymer matrix. Enhanced electrical conductivity was observed for the MWNTs-PAM composites. Graphene samples were prepared by thermal exfoliation of graphite oxide. XRD analysis confirms the formation of graphene.     

Synthesis of carbon nanotubes at low temperature by filament assisted atmospheric CVD and their field emission characteristics

Multiwalled carbon nanotubes (MWNTs) were synthesized using a hot filament assisted chemical vapor deposition (CVD) at the atmospheric pressure at a substrate temperature of 550 °C. The size of nanotubes was controlled by changing the size of catalyst particles. The structure and composition of these nanotubes were investigated using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The electron field emission current of MWNTs was also measured. It was found that the nanotubes with smaller the diameter had higher the emission current levels though synthesis conditions except catalyst particles were the same. These as-grown MWNTs had emission current densities of 6.5 mA/cm² and 2.5 mA/cm² at 1 V/μm for 5-8 nm and 20 nm size carbon nanotube samples, respectively. The results indicated that the MWNTs synthesized had low emission threshold voltages and high emission current levels that are favorable properties for field emission-based display device applications.     

Nitrogen-Doped Carbon Nanotubes Produced by Solar Energy

Both single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs) are produced using a solar reactor working under nitrogen atmosphere. Samples were studied by transmission electron microscopy (TEM), Raman spectroscopy and electron energy loss spectroscopy (EELS). The produced MWNTs exhibit the typical morphologies observed for nitrogen-doped MWNTs synthesized with other methods and EELS measurements point out the presence of substituted nitrogen within the tubes. The doping level is not uniform and the maximum value reaches 11 at.%.     

Biocompatibility and toxicological studies of carbon nanotubes doped with nitrogen

In this report, we compare the toxicological effects between pure carbon multiwalled nanotubes (MWNTs) and N-doped multiwalled carbon (CNx) nanotubes. Different doses of tubes were administered in various ways to mice: nasal, oral, intratracheal, and intraperitoneal. We have found that when MWNTs were injected into the mice's trachea, the mice could die by dyspnea depending on the MWNTs doses. However, CNx nanotubes never caused the death of any mouse. We always found that CNx nanotubes were far more tolerated by the mice when compared to MWNTs. Extremely high concentrations of CNx nanotubes administrated directly into the mice's trachea only induced granulomatous inflammatory responses. Importantly, all other routes of administration did not induce signs of distress or tissue changes on any treated mouse. We therefore believe that CNx nanotubes are less harmful than MWNTs or SWNTs and might be more advantageous for bioapplications.     

Effect of multi-wall carbon nanotubes on the mechanical properties of natural rubber

Multi-walled carbon nanotubes (MWNTs) were used to prepare natural rubber (NR) nanocomposites. Our first effort to achieve nanostructures in MWNTs/NR nanocomposites were formed by incorporating carbonnanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubess can be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. The properties of the nanocomposites such as tensile strength, tensile modulus, tear strength, elongation at break and hardness were studied. Mechanical test results show an increase in the initial modulus for up to 12 times in relation to pure NR. In addition to mechanical testing, the dispersion state of the MWNTs into NR was studied by transmission electron microscopy (TEM) in order to understand the morphology of the resulting system. According to the present study, application of the physical and mechanical properties of carbon nanotubes to NR can result in rubber products which have improved mechanical, physical and chemical properties, compared with existing rubber products reinforced with carbon black or silicone.     

A green route to water soluble carbon nanotubes and in situ loading of silver nanoparticles

A green approach has been developed to synthesize water soluble multi-walled carbon nanotubes (MWNTs). Ag nanoparticles have been loaded on the as-synthesized MWNTs via the in situ solution method. The strategy is based on the introduction of hydroxyl and carboxyl groups through a mild modification of MWNTs via polycondensation of citric acid and D-sorbitol, improving the water solubility of MWNTs, giving rise to preferred sites of Ag nucleation, and providing mild in situ reducing agents. The modification of MWNTs and loading of Ag nanoparticles on MWNTs were demonstrated by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscopy.     

Antimicrobial activity of functionalised carbon nanotubes against pathogenic microorganisms

Carbon nanotubes represent one of the best examples of novel nanostructures, exhibit a range of extraordinary physical properties, strong antimicrobial activity and can pierce bacterial cell walls. This investigation handles the antimicrobial activity of functionalised multiwall carbon nanotubes (F‐MWNTs) as an alternative antimicrobial material compared to the commercial antibiotics. Antibacterial activities of F‐MWNTs are investigated through two different kinds of bacteria, E. coli and S. aureus. The results demonstrate that the best concentration of F‐MWNTs for the maximum inhibition and antibacterial functionality is 80 and 60 μg/ml for E. coli and S. aureus, respectively. The transmission electron microscope reveals the morphological changes damage mechanism for the cellular reliability on these microorganisms. F‐MWNTs are capable of biologically isolating the cell from their microenvironment, contributing to the development of toxic substances and placing the cell under oxidative stress leading to cellular death. The efficiency of F‐MWNTs is compared with the common antibiotics and shows an enhancement in the inhibitory effect with percentages reaches 85%. To account for the bactericidal performance of F‐MWNTs towards these pathogens, the dielectric conductivity and the bacterial growth measurements are conducted. The present study endeavour that F‐MWNTs could be exploited in biomedical devices and altering systems for hospital and industrial cleaning applications.Inspec keywords: antibacterial activity, biomedical materials, microorganisms, cellular biophysics, toxicology, nanomedicine, multi‐wall carbon nanotubes, transmission electron microscopy, electrical conductivity, permittivityOther keywords: F‐MWNTs, pathogenic microorganisms, antimicrobial activity, bacterial cell walls, functionalised multiwall carbon nanotubes, antibacterial activity, E. coli, S. aureus, antimicrobial material, physical properties, transmission electron microscopy, morphological changes, damage mechanism, cellular reliability, microenvironment, toxic substances, oxidative stress, cellular death, bactericidal performance, dielectric conductivity, bacterial growth measurements, biomedical devices, C     

两亲性嵌段共聚物改性的多壁碳纳米管的制备

通过对碳纳米管进行表面改性制得具有引发ATRP反应活性的碳纳米管(MWNT-Br),以MWNT-Br作引发剂经过两次ATRP反应将聚乙烯基吡咯烷酮(PVP)和聚甲基丙烯酸特丁酯(PtBMA)先后接枝到多壁碳纳米管表面制得两亲性嵌段共聚物接枝的碳纳米管(MWNT-PVP-b-PtBMA),用红外光谱、热失重和透射电镜对两亲性碳纳米管进行了表征.并考察了修饰前弱亲油性的纯碳纳米管、酸化后亲水性的碳纳米管和修饰后两亲性碳纳米管这3种碳纳米管在水和氯仿形成的两相体系中的分散情况,观察到所制备的两亲性碳纳米管能够均匀分散在油水两相界面上.     

Pt/MWNTs催化剂的制备及其性能

以多壁碳纳米管为载体，用液相还原法制备了Pt／MWNTs催化剂，通过XRD、TEM等技术对催化剂进行了表征，并将所制催化剂组装成燃料电池，以H2、O2为反应气，测试了催化剂的性能，结果显示Pt／MWNTs催化剂具有优良的电催化活性。     

多壁碳纳米管表面等离子体有机聚合改性

采用等离子体聚合技术在多壁碳纳米管(MWNTs) 表面聚合苯乙烯( Styrene) 、吡咯( Pyrrole) 有机膜。高分辨电镜( HRTEM) 分析显示MWNTs 内外表面均生成纳米级厚度的有机膜, 其中外壁表面厚约7 nm , 内壁表面厚约1～3 nm。将经过表面有机膜处理的MWNTs 添加到聚苯乙烯中, 制备出多壁碳纳米管/ 聚苯乙烯(MWNTs/ PS) 复合材料。扫描电镜(SEM) 对MWNTs/ PS 复合材料分析表明, 覆膜的MWNT 在复合材料中的分散得到改善。通过力学拉伸试验测试了MWNTs/ PS 复合材料断裂强度和弹性模量与MWNTs 含量的关系, 证明了经有机覆膜处理的MWNTs 与PS 形成的复合材料的整体强度得到显著提高。