Functionalization of multi-walled carbon nanotubes and its application in preparing the 3D graphene/carbon nanotubes hybrid architectures

A facile strategy for the preparation of water-dispersible multi-walled carbon nanotubes (MWCNTs) in aqueous solution for the preparation of the three-dimensional (3D) graphene/carbon nanotube (G/CNT) hybrid architectures is proposed, where MWCNTs were functionalized by simultaneous radiation-induced graft polymerization of acrylic acid under the γ-ray (denoted as MWCNT-g-PAA) for improving its dispersibility. The stability of the aqueous solution of MWCNT-g-PAA in water is highly improved. We also use the MWCNT-g-PAA fabricating three-dimensional cylindrical graphene/carbon nanotube (G/CNT) hybrid architectures by a simple one-step hydrothermal process. We found that the as-prepared MWCNTs-g-PAA showed a very good dispersibility in GO solution with different concentration ratio and a promising precursor for preparing the graphene/CNT hybrid materials.     

A biosensor based on Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes and graphene oxide for polyphenol detection

Abstract

The use of nanomaterials allows the design of ultrasensitive biosensors with advantages in the detection of organic molecules. Catechol and catechin are molecules that occur naturally in fruits, and their presence in products like dyes and wines affects quality standards. In this study, catechol and catechin were measured at the nanoscale by means of cyclic voltammetry. The oxidation of Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes (Lac/CN_x-MWCNT) and on graphene oxide (Lac/GO) was used to measure the concentrations of catechol and catechin. Nitrogen-doped multiwalled carbon nanotubes (CN_x-MWCNT) were synthesized by spray pyrolysis and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). Covalently bonded hybrids with laccase (Lac/CN_x-MWCNT and Lac/GO) were generated. Catalytic activity of free enzymes determined with syringaldazine yielded 14 584 UmL^?1. With Lac/CN_x-MWCNT at concentrations of 6.4 mmol L^?1 activity was 9326 U mL^?1, while enzyme activity measured with Lac/GO at concentration of 6.4 mmol L^?1 was 9 234 U mL^?1. The Lac/CN_x-MWCNT hybrid showed higher stability than Lac/GO at different ethyl alcohol concentrations. The Lac/CN_x-MWCNT hybrid can measure concentrations, not previously reported, as low as 1 × 10^?8 mol L^?1 by measuring the electric current responses.     

A biosensor based on Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes and graphene oxide for polyphenol detection

The use of nanomaterials allows the design of ultrasensitive biosensors with advantages in the detection of organic molecules. Catechol and catechin are molecules that occur naturally in fruits, and their presence in products like dyes and wines affects quality standards. In this study, catechol and catechin were measured at the nanoscale by means of cyclic voltammetry. The oxidation of Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes (Lac/CN_x-MWCNT) and on graphene oxide (Lac/GO) was used to measure the concentrations of catechol and catechin. Nitrogen-doped multiwalled carbon nanotubes (CN_x-MWCNT) were synthesized by spray pyrolysis and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). Covalently bonded hybrids with laccase (Lac/CN_x-MWCNT and Lac/GO) were generated. Catalytic activity of free enzymes determined with syringaldazine yielded 14 584 UmL⁻¹. With Lac/CN_x-MWCNT at concentrations of 6.4 mmol L⁻¹ activity was 9326 U mL⁻¹, while enzyme activity measured with Lac/GO at concentration of 6.4 mmol L⁻¹ was 9 234 U mL⁻¹. The Lac/CN_x-MWCNT hybrid showed higher stability than Lac/GO at different ethyl alcohol concentrations. The Lac/CN_x-MWCNT hybrid can measure concentrations, not previously reported, as low as 1 × 10⁻⁸ mol L⁻¹ by measuring the electric current responses.     

Effects of gamma irradiation for sterilization on aqueous dispersions of length sorted carbon nanotubes

There is currently great interest in the potential use of carbon nanotubes as delivery vessels for nanotherapeutics and other medical applications. However, no data are available on the effects of sterilization methods on the properties of nanotube dispersions, the form in which most medical applications will be processed. Here we show the effects of gamma irradiation from a ⁶⁰Co source on the dispersion and optical properties of single-wall carbon nanotubes in aqueous dispersion. Samples of different length-refined populations were sealed in ampoules and exposed to a dose of approximately 28 kGy, a level sufficient to ensure sterility of the dispersions. In contrast to literature results for solid-phase nanotube samples, the effects of gamma irradiation on the dispersion and optical properties of the nanotube samples were found to be minimal. Based on these results, gamma irradiation appears sufficiently non-destructive to be industrially useful for the sterilization of nanotube dispersions.     

多壁碳纳米管/氧化石墨烯/硅橡胶复合薄膜湿敏性能研究

采用化学修饰的多壁碳纳米管(o-MWCNTs)与Hummers法制备的氧化石墨烯(GO)超声混合,加入室温硫化硅橡胶(RTV),利用溶液共混法制备具有湿敏特性的o-MWCNTs/GO/RTV复合薄膜。借助于透射电子显微镜(TEM)、红外吸收光谱(FT-IR)等分析手段分别对化学修饰的多壁碳纳米管及氧化石墨烯进行表征,并对基于o-MWCNTs/GO/RTV的复合薄膜的湿敏性能及湿敏机理进行了探讨。结果表明,混酸处理后的碳纳米管端口打开,侧壁和开端处产生羧基和羟基等官能团,有利于水分子的吸附,同时也有利于与GO表面的基团作用,形成三维的纳微米结构,提高了碳纳米管与硅橡胶基体的相容性,使所制备的o-MWCNTs/GO/RTV复合薄膜灵敏度提高。当相对湿度在23%~87%的范围,m(GO)∶m(o-MWCNTs)=1∶3时,o-MWCNTs/GO/RTV复合薄膜的湿滞为5%RH,灵敏度为0.3152/%RH,响应时间和恢复时间分别为4和27 s。     

碳纳米管的剪切研究

将碳纳米管放入浓硫酸和浓硝酸(3∶1)的混合溶液中,通过长时间超声处理剪切碳纳米管,TEM观测确认,碳纳米管被剪断,长度由1μm以上减小到300nm以下。     

Functionalized graphene oxide and multi-walled carbon nanotubes in hexadecyl trimethyl ammonium bromide and chitosan matrix as metal-free catalyst for enhanced oxygen reduction reaction

The development of new catalysts for high-performance and cost-effective oxygen reduction is crucial in the commercialization of fuel cells. Herein, we demonstrate the use of a novel metal-free catalyst, hexadecyl trimethyl ammonium bromide (CTAB)-functionalized graphene oxide (GO) and multi-walled carbon nanotubes (MWCNT) in CTAB and chitosan matrix (CTAB/GO/MCWNT/CS), which exhibits a significant synergistic catalytic effect on oxygen reduction reaction. Compared with commercially available Pt/C catalysts, enhanced electrocatalytic activity, improved long-term operational stability, and excellent tolerance to methanol in alkaline fuel cells were observed for the novel composite catalyst.     

Flexible field emission of nitrogen-doped carbon nanotubes/reduced graphene hybrid films

The outstanding flexible field emission properties of carbon hybrid films made of vertically aligned N-doped carbon nanotubes grown on mechanically compliant reduced graphene films are demonstrated. The bottom-reduced graphene film substrate enables the conformal coating of the hybrid film on flexible device geometry and ensures robust mechanical and electrical contact even in a highly deformed state. The field emission properties are precisely examined in terms of the control of the bending radius, the N-doping level, and the length or wall-number of the carbon nanotubes and analyzed with electric field simulations. This high-performance flexible carbon field emitter is potentially useful for diverse, flexible field emission devices.     

Growth of aligned carbon nanotubes on ALD-Al2O3 coated silicon and quartz substrates

The smooth surface of the amorphous Al₂O₃ film on either silicon or quartz, coated by atomic layer deposition (ALD), was changed to rough surface by annealing in either air or hydrogen at high temperature (745°C) due to the formation of nanosized pinholes and micrometre pimples during the crystallisation of the amorphous Al₂O₃. The rough surface makes the growth of long carbon nanotubes (CNTs) by chemical vapour deposition impossible. Nevertheless, we were able to develop new catalyst recipes for successful growth of vertically aligned CNTs on ALD-Al₂O₃ coated silicon and quartz substrates. The lengths of the CNTs reached 90?µm on silicon substrates and 180?µm on quartz substrates. Furthermore, it is observed that the adhesion of CNTs on silicon substrates is much stronger than that on quartz substrates.     

Emerging transparent electrodes based on thin films of carbon nanotubes, graphene, and metallic nanostructures

Transparent electrodes are a necessary component in many modern devices such as touch screens, LCDs, OLEDs, and solar cells, all of which are growing in demand. Traditionally, this role has been well served by doped metal oxides, the most common of which is indium tin oxide, or ITO. Recently, advances in nano-materials research have opened the door for other transparent conductive materials, each with unique properties. These include CNTs, graphene, metal nanowires, and printable metal grids. This review will explore the materials properties of transparent conductors, covering traditional metal oxides and conductive polymers initially, but with a focus on current developments in nano-material coatings. Electronic, optical, and mechanical properties of each material will be discussed, as well as suitability for various applications.     

Paraffin-based shape-stable phase change materials with graphene/carbon nanotube three-dimensional network structure

A novel kind of paraffin-based shape-stable phase change materials (SSPCMs) was prepared by introducing paraffin into reduced graphene oxide (rGO)/carbon nanotubes (CNTs) aerogel via vacuum-assisted impregnation method. The effects of ratio of rGO to CNTs in 3D network structure on morphology, structure and property of paraffin-based SSPCMs were investigated. The rGO/CNTs 3D network structure with high thermal conductivity, served as thermally conductive skeleton together. In particular, CNTs was used as a secondary heat conductive filler, which could be well dispered in the SSPCMs to conduct heat synergistically. The SSPCMs exhibited high thermal conductivity and excellent shape-stability. And the thermal conductivity of SSPCMs can be regulated by adjusting the ratio of rGO to CNTs in aerogels. These results indicate that 3D rGO/CNTs aerogels have advantages as thermally conductive skeleton, and can endow phase transition materials with stable shape, so as to realize the application of phase change materials in the field of heat dissipation.     

单壁碳纳米管制备研究新进展

碳纳米管由于具有独特的结构和奇异的物理、化学性质而倍受人们的青睐，并逐渐展示出巨大的应用前景。简要介绍了碳纳米管的结构、性质和应用，并详细评述了单壁碳纳米管制备的新进展。     

石墨烯多壁碳纳米管/超高分子量聚乙烯导电复合材料的制备及性能

为了比较超高分子量聚乙烯(UHMWPE)在单一填充和混合填充时, 复合材料导电性的差别。在超声和肼的作用下, 通过对氧化石墨烯(GO)、 多壁碳纳米管(MWCNTs)和超高分子量聚乙烯水/乙醇分散液减压蒸馏及热压制备了隔离型MWCNTs/UHMWPE、 石墨烯(GNS)/UHMWPE和MWCNTs-GNS/UHMWPE导电复合材料。经SEM、 TEM测试发现, 导电填料分散于UHMWPE颗粒表面, 热压后形成隔离结构。隔离型的MWCNTs/UHMWPE和GNS/UHMWPE复合材料均表现出较低的导电逾渗(0.148%和0.059%, 体积分数,下同), 但MWCNTs/UHMWPE复合材料的电导率(2.0×10^-2 S/m, 1.0%, 质量分数, 下同)明显高于相同填料含量下的GNS/UHMWPE复合材料。 MWCNTs-GNS/UHMWPE复合材料表现出了更低的逾渗(0.039%) 和较高导电性能(1.0×10^-2 S/m, 1.0%), 其拉伸强度和断裂伸长率随填充剂含量的增加呈现出先上升后下降的趋势。     

Buffered internal stresses in diamond-like carbon films reinforced with single-walled carbon nanotubes

Diamond-like carbon (DLC) films reinforced with single-walled carbon nanotubes (SWCNTs) were fabricated by sputter-deposition of DLC onto a few monolayers of spray-coated SWCNTs on glass substrates. The thickness-averaged internal stress was reduced by 1.5 GPa by incorporation of SWCNTs into 10-nm-thick DLC films. Stress analysis indicates that the internal stress is reduced by 1.8 GPa at the SWCNT-DLC nanocomposite layer and decreases exponentially as a function of film thickness. Microscopy reveals significant cracking and delamination in 150-nm-thick DLC films, while the SWCNT-reinforced films remain essentially intact. The results demonstrate that SWCNTs in DLC films influence the early stage of DLC film growth and act as an effective stress-buffering layer near the boundary between the film and substrate.     

Hybrid metal-based carbon nanotubes: Novel platform for multifunctional applications

Combining objects with diverse properties has often the advantage of giving rise to novel functionalities. In this scenario, metal-filled and decorated carbon nanotubes (m-CNTs) represent a class of hybrid carbon-based nanostructured materials with enormous interest for application in several fields, ranging from nanoelectronics and spintronics to nanomedicine and magnetic data recording. The present review will provide the reader with an overview of state-of-the-art hybrid architectures based on m-CNT systems, methods currently employed for their fabrication, the set of their unique properties and how they can be applied toward novel devices with multifunctional properties for a broad range of applications.     

反应温度对碳纳米管的影响

本文利用化学气相沉积( CVD)法,以乙烯为碳源气体,二茂铁为催化剂,在二氧化硅上制备出一系列碳纳米管,并通过拉曼光谱和扫描电子显微镜( SEM)对其形貌、结构和组分进行表征,分析反应温度对碳纳米管的影响.研究发现:当反应温度为860℃时,有均匀的碳纳米管薄膜生成,其管径和长度分别达到104 nm和95 μm,同时结构缺陷少,非碳管杂质较少,纯度较高.     

碳纳米管的制备和吸附特性研究

采用CVD法制备了碳纳米管,并用TEM、BET吸附和~(129)Xe NMR对碳纳米管的表面和内部结构进行了表征.通过BET吸附和~(129)Xe NMR的结果对比分析,可以推断碳纳米管并非全部是中空的,而是被许多隔膜分隔成多个锥帽形空腔,这些隔膜一般为无定形碳,五元环或七元环.经过纯化后的碳纳米管具有优异的吸附性能,有望作为新一代的储氢材料.     

Effects of amino group on the properties of carbon nanotubes

The surfaces of multi-walled carbon nanotubes were grafted with amino functional groups by reacting acyl-chloride-functionalized carbon nanotubes (CNTs) with hexamethylene diamine, which improves the surfactivity of CNTs. The dispersity, surface morphology, and thermogravimetry of acid-treated and amino-functionalized CNTs were investigated. Amino-functionalized CNTs were added into epoxy resin to analyze the effects of amino functional groups on the properties of resin composites. It was found that the properties of CNTs, such as morphology and scale, were not affected by amino functional groups, but the dispersity in water was highly improved. Amino-functionalized CNTs are better dispersed in resin matrix, and the mechanical properties of composites are improved significantly, whereas the conductivity of composites is not enhanced as expected.     

碳纳米管对中间相炭微球制备的影响

以中温煤沥青和碳纳米管为原料进行热缩聚反应,制备出含有碳纳米管的中间相炭微球,采用扫描电子显微镜(SEM)、激光粒度仪和X射线衍射(XRD)等分析手段对其形貌及结构进行了表征。研究了添加碳纳米管对中间相炭微球形貌、粒径、产率、微晶结构及热缩聚工艺的影响。结果表明添加碳纳米管能够促进小球成核,阻止小球的融并长大,使炭微球的粒径减小,分布均匀,但过多的碳纳米管会导致球形度变差及中间相沥青产率的降低;碳纳米管的存在使石墨片层尺寸减小,石墨化程度降低;碳纳米管经过酸煮处理后,可以获得球形度更好、含有更大比例碳纳米管的中间相炭微球。