Fabrication of metal nanowires in carbon nanotubes via versatile nano-template reaction

A nano-template reaction has been developed to fabricate metal nanowires using metallofullerene nanopeapods (i.e., carbon nanotubes (CNTs) encapsulating endohedral metallofullerenes) as starting materials. In this nanometer-scale reaction, the structure of resulting products should possess specific low-dimensional structures, because of their uniform starting orientation of metallofullerene molecules and the rigid restriction of reaction space by the presence of walls of CNTs. Using the nano-template reaction, we have fabricated various Gd nanowires, including a single Gd atomic chain, a one-dimensional alignment of Gd squares, and Gd nanowires that correspond to a one-dimensional segment of the bulk close-packed structure. The same reaction, in principle, can be applied to fabricate more than 20 different types of metal nanowires in the CNTs, which simply are dependent on the use of the corresponding different types of metallofullerenes as encapsulates in the CNTs. The present novel reaction will provide a wide variety of unusual low-dimensional nanowires and nanomaterials in the CNTs, which have not been synthesized via the fabrication techniques that have been reported so far.     

Modification of multi-walled carbon nanotubes with 1,4-diaminobutane dihydrochloride through heating at reflux

Carbon nanotubes (CNT) have been used to propose solutions and develop better quality products that can be applied to areas such as electronics, materials, chemistry, physics and power generation. However, the tendency of CNTs to agglomerate due to their nanometer size and low interaction with other molecules caused by their structural stability has been problematic. For this reason, the present work presents surface modification of multi-walled carbon nanotubes (MWCNTs) through heating at reflux using 1,4-diaminobutane dihydrochloride. The modification of MWCNT was analyzed by infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Termogravimetry (TGA) and scanning electron microscopy (SEM). The most significant change on MWCNTs was obtained after a 24-hour treatment with a maximum percentage of nitrogen content of 2.72%.     

Carbon nanotube reinforced polymer composites—A state of the art

Because of their high mechanical strength, carbon nanotubes (CNTs) are being considered as nanoscale fibres to enhance the performance of polymer composite materials. Novel CNT-based composites have been fabricated using different methods, expecting that the resulting composites would possess enhanced or completely new set of physical properties due to the addition of CNTs. However, the physics of interactions between CNT and its surrounding matrix material in such nano-composites has yet to be elucidated and methods for determining the parameters controlling interfacial characteristics such as interfacial shear stress, is still challenging. An improvement of the physical properties of polymer nanocomposites, based on carbon nanotubes (CNTs), is addicted to a good dispersion and strong interactions between the matrix and the filler.     

Carbon nanomaterials: controlled growth and field-effect transistor biosensors

Carbon nanostructures, including carbon nanotubes (CNTs) and graphene, have been studied extensively due to their special structures, excellent electrical properties and high chemical stability. With the development of nanotechnology and nanoscience, various methods have been developed to synthesize CNTs/graphene and to assemble them into microelectronic/sensor devices. In this review, we mainly demonstrate the latest progress in synthesis of CNTs and graphene and their applications in field-effect transistors (FETs) for biological sensors.     

The interaction of nitrogen molecules with (4, 0) single-walled carbon nanotube: electronic and structural effects

The electronic structure and energetics of (4, 0) single-walled carbon nanotubes (CNTs) interacting with nitrogen have been studied using density-functional calculations. We show that the nanotubes become covered with a stable sheath of N(2) molecules. We have constructed potential energy curves which can be used for the thermodynamic analysis of N(2) adsorption and desorption processes. Our results show that any analysis of the observed properties (for example thermodynamics, stability, and photoluminescence) of air-exposed CNTs needs to consider the N(2) adsorbed on the CNTs.     

Biomolecular Tuning of Electronic Transport Properties of Carbon Nanotubes via Antibody Functionalization

Carbon nanotubes (CNTs) are remarkable solid-state nanomaterials due to their unique electrical and mechanical properties. The electronic properties of nanotubes combined with biological molecules such as proteins could make miniature devices for biological sensing applications. In this paper, the noncovalent interaction of single-wall CNTs with antibodies is presented for its potential applications for detecting overexpressed cell surface receptors in breast cancer cells. The degree of binding of antibodies on CNTs was found to be more than 80% for an extended sampling area by confocal microscopy. The key to achieve such high degree of functionalization is due to the separation of CNTs using surfactants that leads to a high surface area to volume ratio and higher number of active sites for charge transfer that enhance binding. This paper also presents tuning of electronic transport properties of CNTs by monoclonal antibodies that are specific to insulin-like growth factor 1 receptor in breast cancer     

碳纳米管:可控制备决定未来（英文）

在过去几十年中,碳纳米管由于其优异的物理和化学性质而备受关注,被认为是一个强有力的未来明星材料.尽管基于碳纳米管的诸多产品及应用实例相继浮现,但是碳纳米管所呈现出的实际性质与理论值之间依然存在较大差异,无法达到研究者的预期,这源自于目前尚未成熟的控制制备技术.碳纳米管的可控制备技术包括结构的精细控制方法和样品的宏量制备技术,这在很大程度上决定了碳纳米管的未来发展前景.基于此,本文概述了近几十年来研究者们在碳纳米管的精细结构控制、聚合状态设计和样品宏量制备等方面的主要进展,进一步指出了碳纳米管未来的可控制备技术必须与特定化的应用紧密结合,以迎接即将来临的产业化时代.     

DNA damage induced by multiwalled carbon nanotubes in mouse embryonic stem cells

Carbon nanotubes (CNTs) have shown promise as an important new class of multifunctional building blocks and innovative tools in a large variety of applications, ranging from nanocomposite materials through nanoelectronics to biomedical devices. Because of their unusual one-dimensional hollow nanostructure and unique physicochemical properties, CNTs are particularly useful as novel drug delivery tools and imaging agents. However, such biomedical applications will not be realized if there is no proper assessment of the potential hazards of CNTs to humans and other biological systems. Although a few reports on the cytotoxicity of CNTs have been published, very little is known about the toxicity at the molecular level, or genotoxicity, of CNTs in mammalian cells. We have for the first time assessed the DNA damage response to multiwalled carbon nanotubes (MWNTs) in mouse embryonic stem (ES) cells. We found that MWNTs can accumulate and induce apoptosis in mouse ES cells and activate the tumor suppressor protein p53 within 2 h of exposure. Furthermore, we also observed increased expression of two isoforms of base excision repair protein 8-oxoguanine-DNA glycosylase 1 (OGG1), double strand break repair protein Rad 51, phosphorylation of H2AX histone at serine 139, and SUMO modification of XRCC4 following the treatment with MWNTs. A mutagenesis study using an endogenous molecular marker, adenine phosphoribosyltransferase (Aprt), showed that MWNTs increased the mutation frequency by 2-fold compared with the spontaneous mutation frequency in mouse ES cells. These results suggest that careful scrutiny of the genotoxicity of nanomaterials is needed even for those materials, like multiwalled carbon nanotubes, that have been previously demonstrated to have limited or no toxicity at the cellular level.     

Recent developments in inorganically filled carbon nanotubes: successes and challenges

Abstract

Carbon nanotubes (CNTs) are a unique class of nanomaterials that can be imagined as rolled graphene sheets. The inner hollow of a CNT provides an extremely small, one-dimensional space for storage of materials. In the last decade, enormous effort has been spent to produce filled CNTs that combine the properties of both the host CNT and the guest filling material. CNTs filled with various inorganic materials such as metals, alloys, semiconductors and insulators have been obtained using different synthesis approaches including capillary filling and chemical vapor deposition. Recently, several potential applications have emerged for these materials, such as the measurement of temperature at the nanoscale, nano-spot welding, and the storage and delivery of extremely small quantities of materials. A clear distinction between this class of materials and other nanostructures is the existence of an enormous interfacial area between the CNT and the filling matter. Theoretical investigations have shown that the lattice mismatch and strong exchange interaction of CNTs with the guest material across the interface should result in reordering of the guest crystal structure and passivation of the surface dangling bonds and thus yielding new and interesting physical properties. Despite preliminary successes, there remain many challenges in realizing applications of CNTs filled with inorganic materials, such as a comprehensive understanding of their growth and physical properties and control of their structural parameters. In this article, we overview research on filled CNT nanomaterials with special emphasis on recent progress and key achievements. We also discuss the future scope and the key challenges emerging out of a decade of intensive research on these fascinating materials.     

Effect of density variation and non-covalent functionalization on the compressive behavior of carbon nanotube arrays

Arrays of aligned carbon nanotubes (CNTs) have been proposed for different applications, including electrochemical energy storage and shock-absorbing materials. Understanding their mechanical response, in relation to their structural characteristics, is important for tailoring the synthesis method to the different operational conditions of the material. In this paper, we grow vertically aligned CNT arrays using a thermal chemical vapor deposition system, and we study the effects of precursor flow on the structural and mechanical properties of the CNT arrays. We show that the CNT growth process is inhomogeneous along the direction of the precursor flow, resulting in varying bulk density at different points on the growth substrate. We also study the effects of non-covalent functionalization of the CNTs after growth, using surfactant and nanoparticles, to vary the effective bulk density and structural arrangement of the arrays. We find that the stiffness and peak stress of the materials increase approximately linearly with increasing bulk density.     

Alignment of carbon nanotubes and reinforcing effects in nylon-6 polymer composite fibers

Alignment of pristine carbon nanotubes (P-CNTs) and fluorinated carbon nanotubes (F-CNTs) in nylon-6 polymer composite fibers (PCFs) has been achieved using a single-screw extrusion method. CNTs have been used as filler reinforcements to enhance the mechanical and thermal properties of nylon-6 composite fibers. The composites were fabricated by dry mixing nylon-6 polymer powder with the CNTs as the first step, then followed by the melt extrusion process of fiber materials in a single-screw extruder. The extruded fibers were stretched to their maxima and stabilized using a godet set-up. Finally, fibers were wound on a Wayne filament winder machine and tested for their tensile and thermal properties. The tests have shown a remarkable change in mechanical and thermal properties of nylon-6 polymer fibers with the addition of 0.5?wt% F-CNTs and 1.0?wt% of P-CNTs. To draw a comparison between the improvements achieved, the same process has been repeated with neat nylon-6 polymer. As a result, tensile strength has been increased by 230% for PCFs made with 0.5% F-CNTs and 1% P-CNTs as additives. These fibers have been further characterized by DSC, Raman spectroscopy and SEM which confirm the alignment of CNTs and interfacial bonding to nylon-6 polymer matrix.     

碳纳米管在水泥基复合材料中的分散方法研究进展

碳纳米管(CNTs)作为性能优越的新型纳米材料被广泛用于增强基体材料,但是其易团聚且难以分散,使得实现其在基体材料中的均匀分散成为研究的重点。详细介绍了CNTs在增强水泥基复合材料研究中的分散方法与分散机理,并比较了各种分散方法的优缺点。重点论述了超声时间、酸处理时间、表面活性剂种类与掺量等因素对CNTs分散效果的影响,并讨论了评价CNTs分散效果的表征方法。将CNTs均匀分散到水泥基体中,可以显著提高复合材料的各项力学性能。     

Correlation between dispersion state and electrical conductivity of MWCNTs/PP composites prepared by melt blending

Non-conductive polymers filled with conductive carbon nanotubes (CNTs) often do not show detectable conductivity due to poor dispersion of carbon nanotubes in the polymer matrix and the lack of conductive networks formed from CNTs. In this work, we attempted two ways to improve the dispersion of multi-walled carbon nanotubes (MWCNTs) in a polypropylene (PP) matrix: chemical modification of MWCNTs and addition of a master batch as a compatibilizer, followed by melt blending using a micro-compounder. The relationship between the dispersion state of MWCNTs and the electrical conductivity of the CNTs/PP composites have been investigated by controlling several factors such as CNTs modification, compatibilization by a master batch, melt mixing, and post-heat treatment. The enhanced interfacial adhesion between the CNTs and the polymer could improve the dispersion of CNTs but it could also reduce the electrical conductivity of the composites. Meanwhile, it is interestingly found that the post-heat treatment could increase the conductivity remarkably due to the connection of CNTs into networks. Thus, it is concluded that the balance between dispersion of CNTs and the formation of conductive networks plays an important role in enhancing the electrical conductivity of composites.     

Dissolution, characterization and photofunctionalization of carbon nanotubes

A simple method to disperse carbon nanotubes (CNTs) has been achieved, which gives two photofunctionalized CNTs, hydrazine nanotubes (h-CNTs) and 1,3,4-oxadiazole nanotubes (o-CNTs). Results from FTIR, ¹H NMR spectroscopy and TEM observations showed that the functionalization was successful. The modified nanotubes can dissolve in most of the nonpolar organic solvents and no precipitate was observed in the solution of the nanotubes even after 2 months. The functionalized nanotubes showed photo-electronic properties, which is due to the attachment of the function groups to them as proved by steady-state fluorescence spectroscopy. Both h-CNTs and o-CNTs showed good thermal stability below 300 °C and might be used as functional materials.     

Carbon nanotubes in the liquid phase: addressing the issue of dispersion

The inherent size and hollow geometry with extraordinary electronic and optical properties make carbon nanotubes (CNTs) promising building blocks for molecular or nanoscale devices. Unfortunately, their hydrophobic nature and their existence in the form of agglomerated and parallel bundles make this interesting material inadequately soluble or dispersible in most of the common solvents, which is crucial to their processing. Therefore, various ingenious techniques have been reported to disperse the CNTs in various solvents with different experimental conditions. However, by analyzing the published scientific research articles, it is evident that there is an important issue or misunderstanding between the term "dispersion" and "solubilization". As a result many researchers use the terms interchangeably, particularly when stating the interaction of CNTs with liquids, which causes confusion among the readers, students, and researchers. In this article, this fundamental issue is addressed in order to give basic insight to the researchers who are working with CNTs, as well as to the scientists who deal with nano-related research domains.     

Macroscopic Carbon Nanotube Structures for Lithium Batteries

Carbon nanotubes (CNTs) are regarded as one of the most promising materials to manufacture high‐performance lithium batteries. This prospect is closely related to the construction of macroscopic architectures of CNTs. The superaligned CNT (SACNT) array is a unique kind of vertically aligned CNT array. Its highly oriented feature and strong intertube force facilitate the fabrication of macroscopic SACNT structures with various forms, including unidirectional films, buckypapers, and aerogels, etc. The as‐produced SACNT macroscopic architectures are successfully introduced into lithium batteries due to their outstanding electrical and mechanical properties. Herein, an overview of the functions of macroscopic SACNTs in lithium batteries is proposed, including their applications in composite electrodes, current collectors, interlayers, and flexible full cells.     

天然有机质对纳米碳管环境行为的影响研究进展

随着纳米技术的快速发展,大量的纳米碳管(CNTs)不可避免地释放到环境中。由于其较大的憎水性表面,CNTs与有机污染物和天然有机质(NOM)强烈地相互作用。综述了NOM存在下CNTs的环境行为,包括NOM对CNTs分散特性和吸附有机污染物特性的影响。着重论述了NOM的理化性质对CNTs分散的影响,"拉拉链"或"胶束包裹"是主要的分散机制。强调应该对不同分散机制下分散的CNTs与有机污染物的相互作用给予更多的关注,提出了目前在液相环境中直接测定CNTs表面积的新思路,并对今后的研究方向进行了展望。     

Incorporation of organic groups on the surface of multi-walled carbon nanotubes using an ultrasonic tip

Multi-walled carbon nanotubes (MWCNTs) have been used to solve problems in different fields due to their mechanical, electrical and nanometric properties. However, the tendency of CNTs to agglomerate, and their poor interactions with other molecules have hindered their use. Accordingly, CNTs have been modified mainly by heating under reflux with strong acids or bases, in some cases for up to 72 h. In this study, the surfaces of MWCNTs were modified with 1,4-diaminobutane dihydrochloride (DB) and oxalic acid dihydrate (OX) using an ultrasonic tip (25 mm) at 20 kHz and a temperature of 67–80°C. Three different ultrasound times were employed: 20, 32 and 64 min. The most significant changes to the MWCNTs were observed when they were modified with DB (N 1s (11.05%) and Cl 2p (1.01%)) and OX (C 1s (74.69%) and O 1s (25.31%)) at 20 min, 68°C and 32 min, 70°C, respectively.     

碳纳米管表面修饰改性、机理研究现状及展望

碳纳米管具有优异的力学、物理性能,是理想的复合材料增强体.金属/碳纳米管复合材料已成为当今的研究热点.由于碳纳米管易团聚,与基体的相容性差,严重影响了基体和增强体之间的结合.为了增强其相容性,需对碳纳米管表面进行修饰.介绍了碳纳米管表面修饰的方法,综述了国内外的研究现状,展望了碳纳米管表面修饰的发展与应用前景.     

Carbon nanotube (CNT)-based composites as electrode material for rechargeable Li-ion batteries: A review

The ever-increasing demands for higher energy density and higher power capacity of Li-ion secondary batteries have led to search for electrode materials whose capacities and performance are better than those available today. Carbon nanotubes (CNTs), because of their unique 1D tubular structure, high electrical and thermal conductivities and extremely large surface area, have been considered as ideal additive materials to improve the electrochemical characteristics of both the anode and cathode of Li-ion batteries with much enhanced energy conversion and storage capacities. Recent development of electrode materials for LIBs has been driven mainly by hybrid nanostructures consisting of Li storage compounds and CNTs. In this paper, recent advances are reviewed of the use of CNTs and the methodologies developed to synthesize CNT-based composites for electrode materials. The physical, transport and electrochemical behaviors of the electrodes made from composites containing CNTs are discussed. The electrochemical performance of LIBs affected by the presence of CNTs in terms of energy and power densities, rate capacity, cyclic life and safety are highlighted in comparison with those without or containing other types of carbonaceous materials. The challenges that remain in using CNTs and CNT-based composites, as well as the prospects for exploiting them in the future are discussed.