Chemically functionalized carbon nanotubes

Since their discovery, carbon nanotubes have attracted the attention of many a scientist around the world. This extraordinary interest stems from their outstanding structural, mechanical, and electronic properties. In fact, apart from being the best and most easily available one-dimensional (1D) model system, carbon nanotubes show strong application potential in electronics, scanning probe microscopy, chemical and biological sensing, reinforced composite materials, and in many more areas. While some of the proposed applications remain still a far-off dream, others are close to technical realization. Recent advances in the development of reliable methods for the chemical functionalization of the nanotubes provide an additional impetus towards extending the scope of their application spectrum. In particular, covalent modification schemes allow persistent alteration of the electronic properties of the tubes, as well as to chemically tailor their surface properties, whereby new functions can be implemented that cannot otherwise be acquired by pristine nanotubes.     

Ozonolysis of functionalized single-walled carbon nanotubes

Room temperature ozonolysis of fluorinated SWNT and phenyl-sulfonated SWNT have been studied in perfluoropolyether (PFPE) solvents. Etching at the end caps (approximately 70 nm/hour for fluorinated SWNT/PFPE suspension with 1 g/l concentration) has been demonstrated to be the dominating effect during the ozonolysis of fluorinated SWNT. Base on characterization by AFM analysis, X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy, fluorination along the SWNT sidewalls protects F-SWNT from extensive functionalization by ozonolysis. An ozone reaction with fluorinated SWNT has been found to improve its solubility in 96% sulfuric acid. This allows oxidative cutting by ammonium peroxydisulfate without defluorination. In comparison to fluorinated SWNT, phenyl-sulfonated SWNT was found to be effectively and homogeneous cut by ozonolysis in a water suspension.     

Mechanical properties of functionalized carbon nanotubes

Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization.     

功能化碳纳米管的应用研究进展

碳纳米管具有独特的管状结构和优异的性能,由于其表面活性、分散能力的制约,影响了碳纳米管的应用。从共价修饰和非共价修饰两方面,介绍了目前碳纳米管功能化修饰的方法和研究状况。从光电通信、医疗、材料等方面着重介绍了功能化修饰后的碳纳米管一些最新应用进展,展望了碳纳米管的发展与应用前景。     

Advances and prospects on biomolecules functionalized carbon nanotubes

In recent years, functionalization of carbon nanotubes (CNTs) with biomolecules such as nucleotide acids, proteins, and polymers as well as cells have emerged as a new exciting field. Theoretical and experimental studies of structure and function of bio-inspired CNT composites have made great advances. The importance of nucleic acids, proteins, and polymers to the fundamental developments in CNT-based bio-nano-composites or devices has been recognized. In particular, biomechanics, biochemistry, thermodynamics, electronic, optical, and magnetic properties of the bio-inspired CNT composites have become a new interdisciplinary frontier in life science and nanomaterial science. Here we review some of the main advances in this field over the past few years, explore the application prospects, and discuss the issues, approaches, and challenges, with the aim of stimulating a broader interest in developing CNT-based bio-nanotechnology.     

叶酸功能化碳纳米管负载布洛芬及可控释放

利用多壁碳纳米管为药物载体,采用酸化处理改进了材料表面的亲疏水性及在溶液中的分散性,叶酸改性壳聚糖修饰的碳纳米管表面,以布洛芬为模型药物,重点考察了其组装与缓释性能。研究表明,随着布洛芬药物浓度的增加,负载药物的速率加快,载药量也随之增加;温度对载药量无明显影响;叶酸改性壳聚糖修饰的碳纳米管无突释现象,是理想的药物载体;随着介质离子浓度的增大,释药速率加快,释药量增加。     

Field-effect transistors assembled from functionalized carbon nanotubes

We have fabricated field-effect transistors from carbon nanotubes using a novel selective placement scheme. We use carbon nanotubes that are covalently bound to molecules containing a hydroxamic acid functionality. The functionalized nanotubes bind strongly to basic metal oxide surfaces, but not to silicon dioxide. Upon annealing, the functionalization is removed, restoring the electronic properties of the nanotubes. The devices thus fabricated show excellent electrical characteristics.     

Biocompatibility of native and functionalized single-walled carbon nanotubes for neuronal interface

Single-walled carbon nanotubes (SWNTs) have unique mechanical, electrical, and optical properties and can be easily chemically modified; features that make them excellent candidate materials for applications as sensors and stimulators in neuronal tissue engineering. The purpose of this study was to demonstrate that SWNTs can support neuronal attachment and growth, that simple chemical modifications can be employed to control cell growth, that SWNTs do not interfere with ongoing neuronal function, and that neurons can be electrically coupled to SWNTs. Growth and attachment of the neuroblastoma*glioma NG108, a model neuronal cell, was assessed on unmodified SWNT substrates or substrates from SWNTs modified with 4-benzoic acid or 4-tert-butylphenyl functional groups using a simple functionalization method. SWNT films support cell growth, but at a reduced level compared to tissue culture-treated polystyrene. The order of viability and cell attachment was tissue culture treated polystyrene > SWNTs > 4-tert-butylphenyl-functionalized SWNTs > 4-benzoic acid-functionalized SWNTs. Decreased cell growth after culture on untreated (non adherent) polystyrene suggested that cell attachment was a critical determinant of proliferation and cell growth on SWNTs. Fluorescence and scanning electron microscopy revealed decreased neurite outgrowth in NG108 grown on SWNT substrates. We are also among the first groups to demonstrate electrical coupling of SWNTs and neurons by demonstrating that NG108 and rat primary peripheral neurons showed robust voltage-activated currents when electrically stimulated through transparent, conductive SWNT films. Our data suggest that SWNTs are flexible resource materials for tissue engineering application involving electrically excitable tissues such as muscles and nerves.     

Cytocompatibility studies of vertically-aligned multi-walled carbon nanotubes: Raw material and functionalized by oxygen plasma

It was presented a strong difference on cell adhesion and proliferation of functionalized vertically-aligned multi-walled carbon nanotube (VACNT) scaffolds compared to raw-VACNT. Biocompatibility in vitro tests were performed on raw-VACNT after superficial modification by oxygen plasma, which changes its superhydrophobic character to superhydrophilic. Two cytocompatibility tests were applied: 1) total lactate dehydrogenase colorimetric assay for the study of proliferating cells; and 2) cellular adhesion by scanning electron microscopy. Results showed that superhydrophilic VACNT scaffolds stimulate cell growth with proliferation up to 70% higher than normal growth of cell culture.     

Electrodeposition of composite materials containing functionalized carbon nanotubes

New methods have been developed for the synthesis and electrodeposition of functionalized single-walled carbon nanotubes (f-SWNTs). Polystyrene sulfonate functionalized nanotubes (PSS-f-SWNTs) and poly(ethylene imine) functionalized nanotubes (PEI-f-SWNTs) were co-deposited with cationic chitosan macromolecules. It was shown that chitosan promotes cathodic deposition of anionic PSS-f-SWNTs. The strategies for charging and electrodeposition of PEI-f-SWNTs include partial protonation of PEI in acidic chitosan solutions or formation of cationic Ag⁺–PEI complexes. The thickness of chitosan–PSS-f-SWNTs and chitosan–PEI-f-SWNTs composite films was varied in the range of up to 0.5–5 μm. The amount of f-SWNTs in the deposits was varied by controlling the SWNT concentration in the solutions. It was shown that the use of chitosan enabled co-deposition of other materials, such as hydroxyapatite (HA). The proposed method enabled the fabrication of composite films.     

Amperometric determination of hydrogen peroxide by functionalized carbon nanotubes through EDC/NHS coupling chemistry

The electrochemistry of the redox mediator Toluidine blue (TB) which was covalently linked to the carboxyl group of the multiwalled carbon nanotubes (MWNTs) by coupling reactions, in which N-hydroxysuccinimide was used to assist 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride catalyzed amidation reaction is described. The results from cyclic voltammetry (CV) and amperometry suggested that the redox mediator is linked to the surface of the MWNTs and the nanotubes showed an obvious promotion for the direct electron-transfer between the redox mediator and the electrode. A couple of well-defined redox peak of TB was observed in a phosphate buffer solution (pH 7.0). The redox mediator immobilized to MWNTs exhibits remarkable electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). The analytical applicability of the modified electrode for the determination of hydrogen peroxide was examined. A linear response in the concentration range of 6.8 x 10(-7)-3.4 x 10(-2) M (r = 0.9958) was obtained with detection limit of 3.4 x 10(-7) M for the determination of hydrogen peroxide. The modified electrode has advantages of being highly stable, sensitive, ease of construction and use.     

环氧化功能碳纳米管改性氨基PPS

聚苯硫醚（PPS）是绝缘和疏水性材料,一定程度上限制了其在某些特定领域的应用。利用氨基改性PPS（NPPS）,并利用环氧功能化多壁碳纳米管（EFMWCNTs）与NPPS共价作用形式,采用溶液共混制备了EFMWCNTs/NPPS导电复合材料。利用FTIR、XPS、XRD、FESEM、TEM、DSC、TGA和半导体粉末电导率测试仪系统表征了复合材料的结构与性能。表征结果显示:PPS的链段上引入氨基后,PPS的熔融峰和结晶峰消失。NPPS利用EFMWCNTs进一步改性后,EFMWCNTs/NPPS导电复合材料的热稳定性相比NPPS增加,原因是EFMWCNTs与NPPS之间的共价作用有效提高了EFMWCNTs在NPPS中的分散性。EFMWCNTs/NPPS复合材料的电导率随EFMWCNTs添加量增加而增加,添加10wt%的EFMWCNTs时,复合材料的电导率为6.1×10-2 S/cm。      

碳纳米管的表征和重金属阴离子吸附性能

通过化学修饰使碳纳米管表面富含各种氧功能团,利用XPS和TPD方法表征了碳纳米管表面氧功能团的化学物理特性.研究发现:对比于未修饰的碳纳米管,化学修饰后的碳纳米管对高毒性的铬酸根阴离子有很强的吸附能力;其优异的吸附能力归结于金属阴离子与纳米管表面氧功能团的相互作用.研究指出碳纳米管可以作为替代吸附材料用于处理废水中重金...     

Implementation of functionalized multiwall carbon nanotubes on magnetorheological elastomer

This work studies the effects of loading various functionalized multiwall carbon nanotubes (carboxyl, –COOH-MWCNTs) on the morphological and the field-dependent rheological properties of magnetorheological elastomers (MREs). A new type of MRE, which is reinforced by various loading from 0 to 1.5 wt% of COOH-MWCNT, is fabricated and experimentally investigated. The morphology of COOH-MWCNT and MRE with COOH-MWCNTs is characterized using field emission scanning electron microscopy and transmission electron microscopy. The results indicate that the COOH-MWCNTs are well embedded and dispersed randomly in the MRE structures. The rheological properties under different magnetic fields are evaluated using parallel plate rheometers. The influence of COOH-MWCNT content on the viscoelastic performance of the MRE is systematically investigated. It is found that when a higher content of COOH-MWCNT (up to 1.0 wt%) is added in the MRE, the MRE exhibits a higher MR effect of up to 17.5%. It is also shown that COOH-MWCNT acts as a reinforcing agent that leads to an enhancement in MR performance.     

Dispersion of functionalized multi-walled carbon nanotubes in multi-walled carbon nanotubes/liquid crystal nanocomposites and their thermal properties

A novel liquid crystal functionalized multi-walled carbon nanotubes (LC-MWNTs)/2-methyl-N,N′-bis(4′-methoxy benzoyloxy)-terephthalamide liquid crystal (LC) nanocomposite (LC-MWNTs/LC) was prepared via solution blend. The dispersion and thermal property of the nanocomposites with different loadings of LC-MWNTs (0.1-1 wt.%) were investigated using SEM, TGA and DSC. The results show that the dispersion of LC-MWNTs in LC matrix is more homogeneous than purified MWNTs. The decomposition temperature of nanocomposites exhibits obvious decrease at first and then increase with increasing concentration of LC-MWNTs, which is lower than that of LC for 0.1-0.4 wt.% LC-MWNT loadings and higher than that of LC for 0.5-1 wt.% LC-MWNT loadings. The addition of LC-MWNTs has little effects on the texture of smectic mesophase. These results illustrate the LC-MWNTs/LC nanocomposites, which have lower melting point and higher decomposition temperature than those of LC by adding adequate amount of LC-MWNTs, show a wide temperature range of mesophase and high thermostability. The increased mesophase temperature region of LC materials will be beneficial to their practical applications.     

Hydrogen peroxide vapor sensor using metal-phthalocyanine functionalized carbon nanotubes

We have developed a process for preparation of composites by blending and ultrasonification of multi-walled carbon nanotubes with metal-phthalocyanines and have used the same as very selective and sensitive sensor for detection of H₂O₂ vapors. A combination of sensors made from composites of cobalt-phthalocyanine and copper-phthalocyanine with multiwall carbon nanotubes has been found to show opposite conductivities to H₂O₂ vapors while the pair shows similar response to other chemical vapors. This unusual behavior makes this paired sensor as a reliable method to selectively identify the presence of H₂O₂ vapors with response and recovery times of few seconds. Our developed sensors work at room temperature and show resistivity in the range of 10⁴ to 10⁵ Ω cm. They can be employed for detection of H₂O₂ based explosives, to monitor levels of H₂O₂ in industrial units and other applications.     

功能化多壁碳纳米管海绵状微球制备

通过催化化学气相沉积法合成了多壁碳纳米管(MWCNTs).在相转移催化剂甲基三辛基氯化铵存在下,以高锰酸钾(KMnO4)为氧化剂在室温下对MWCNTs进行功能化处理.采用傅立叶变化红外光谱、热失重分析分析法对功能化MWCNTs进行表征.借助超声波降解法将功能化MWCNTs分散在二氯甲烷中形成悬浮液,然后将其悬浮液逐滴加至搅拌的聚乙烯醇溶液中形成海绵状微球.扫描电子显微镜(SEM)显示:形成的海绵状微球由松散缠结的MWCNTs构成,直径为50μm～150μm.该微球可望应用于轻型吸能涂料,催化剂以及电子学领域.     

Characterization of an interaction between functionalized carbon nanotubes and an enzyme

Carbon nanotubes (CNTs) did not exhibit strong interactions with Biliverdin IX beta reductase enzyme (BVRB) in water. With the use of noncovalent functionalization by the surfactant Triton X-100, the surfaces of the CNTs were changed from hydrophobic to hydrophilic. The hydrophilic surface of the CNT-Triton conjugate interacts with the hydrophilic surface of BVRB, thus creating a water-soluble complex. Results from ultracentrifugation through a sucrose gradient and gel electrophoresis show the presence of the enzyme. Raman spectroscopy confirmed that the enzyme indeed interacts with CNT-Triton conjugates.     

Quantum transport properties of chemically functionalized long semiconducting carbon nanotubes

We present a first-principles study of the electronic transport properties of micrometer long semiconducting carbon nanotubes randomly covered with carbene functional groups. Whereas prior studies suggested that metallic tubes are hardly affected by such addends, we show here that the conductance of semiconducting tubes with standard diameter is, on the contrary, severely damaged. The configurational-averaged conductance as a function of tube diameter, with a coverage of up to one hundred molecules, is extracted. Our results indicate that the search for a conductance-preserving covalent functionalization route remains a challenging issue.