Magnetic orientation of single-walled carbon nanotubes or their composites using polymer wrapping

Abstract

The magnetic orientation of single-walled carbon nanotubes (SWNTs) or the SWNT composites wrapped with polymer using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEHPPV) as the conducting polymer were examined. The formation of SWNT/MEHPPV composites was confirmed by examining absorption and fluorescence spectra. The N,N-dimethylformamide solution of SWNT/MEHPPV composites or the aqueous solution of the shortened SWNTs was introduced dropwise onto a mica or glass plate. The magnetic processing of the composites or the SWNTs was carried out using a superconducting magnet with a horizontal direction (8 T). The AFM images indicated that the SWNT/MEHPPV composites or the SWNTs were oriented randomly without magnetic processing, while with magnetic processing (8 T), they were oriented with the tube axis of the composites or the SWNTs parallel to the magnetic field. In polarized absorption spectra of SWNT/MEHPPV composites on glass plates without magnetic processing, the absorbance due to semiconducting SWNT in the near-IR region in horizontal polarized light was almost the same as that in vertical polarized light. In contrast, with magnetic processing (8 T), the absorbance due to semiconducting SWNT in the horizontal polarization direction against the direction of magnetic field was stronger than that in the vertical polarization direction. Similar results were obtained from the polarized absorption spectra for the shortened SWNTs. These results of polarized absorption spectra also support the magnetic orientation of the SWNT/MEHPPV composites or the SWNTs. On the basis of a comparison of the composites and the SWNTs alone, the magnetic orientation of SWNT/MEHPPV composites is most likely ascribable to the anisotropy in susceptibilities of SWNTs.     

Coating and filling of carbon nanotubes with homogeneous magnetic nanoparticles

Magnetic multi-walled carbon nanotube (MWCNT) composites were obtained by decoration of metal oxide nanoparticles on or in carbon nanotubes. The method involved the dispersion of the carbon nanotubes in iron pentacarbonyl Fe(CO)₅ followed by vacuum thermolysis and subsequent oxidation. The magnetic iron oxide particle deposition was always homogeneous and could be controlled selectively on the outer, inner, or both surfaces of MWCNTs by using different MWCNTs. Since the hollow channels remained intact, these MWCNT based composites could find special applications in cellular delivery systems.     

Magnetic property of FePt nanoparticles encaged in carbon nanotubes

Encapsulation of FePt nanoparticles in carbon nanotubes (CNTs) was attempted using a thermal chemical vapor deposition technique with a Fe/Pt bilayer catalyst. The metal nanoparticles were encapsulated at the tip of multi-walled CNTs. A selected area electron diffraction measurement of the nanoparticles at CNT tips indicated that diffraction spots attributed to an ordered L1₀ phase. Magnetic hysteresis loops indicated existence of magnetic nanoparticles having various coercivities. From numerical fittings assuming that high and low coercivity components contributed to the hysteresis loops, the high coercivity component was estimated to reach 11.3 kOe (902 kA/m).     

Functionalization of carbon nanotubes with magnetic nanoparticles: general nonaqueous synthesis and magnetic properties

A novel approach has been developed to synthesize magnetic nanoparticle and carbon nanotube (CNT) core-shell nanostructures, such as CoO/CNTs and Mn(3)O(4)/CNTs, by the nonaqueous solvothermal treatment of metal carbonyl on CNT templates using hexane as the solvent. The morphological and structural characterizations indicate that numerous cubic CoO or tetragonal Mn(3)O(4) nanoparticles are deposited on the surfaces of the CNTs to form CNT-based core-shell nanostructures. It is revealed that the hydrophobic interaction between nanoparticles and CNTs in hexane plays the critical role for the formation of CNT-based core-shell nanostructures. A physical property measurement system (PPMS-9, Quantum Design) analysis indicates that the CoO/CNT core-shell nanostructures show weak ferromagnetic performance at 300?K due to the ferromagnetic Co clusters and the uncompensated surface spin states, while the Mn(3)O(4)/CNT core-shell nanostructures display ferromagnetic behavior at low temperature (34.5?K), which transforms into paramagnetic behavior with increasing temperature.     

纳米镍颗粒填充碳纳米管的制备与磁性能

采用自制的实验装置, 通过阳极弧放电等离子体技术成功制备了Ni纳米颗粒填充的碳纳米管, 利用高分辨透射电子显微镜(HRTEM)、 XRD、 TEM、 X射线能量色散分析谱仪(XEDS)和振动样品磁强计(VSM)等测试手段对样品的化学成分、 形态、 微观结构和磁性能进行了表征。实验结果表明, 采用本文中实验方法能获得大量被纳米金属颗粒填充的碳纳米管, 其内部填充物为面心立方(FCC)结构的纳米Ni颗粒, 外围薄层为石墨碳层。碳纳米管的外径为30~40 nm, 壁厚5~8 nm, 内部填充的纳米颗粒呈球形和椭球形, 粒径均匀, 在管腔内不连续分布。产物具有顺磁特性, 矫顽力是78 Oe, 饱和磁化强度是33 enu/g。     

Magnetic anisotropy in the films of oriented carbon nanotubes filled with iron nanoparticles

Films of carbon nanotubes oriented perpendicularly to the substrate surface and filled with iron nanoparticles have been synthesized and studied. Morphological features of these nanocomposite films lead to the appearance of an easy magnetization axis, which is perpendicular to the film plane. A method for enhancement of this effect is suggested and successfully tested.     

Decorating carbon nanotubes with Cobalt nanoparticles

A magnetic composite of multiwalls carbon nanotubes (MWNTs) decorated with Cobalt nanoparticles was synthesized successfully by a simple chemical precipitation and deoxidization method. The composite was analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The pattern of XRD indicated that MWNTs and Cobalt nanoparticles coexisted in the composite. The TEM images revealed that the Cobalt nanoparticles were distributed on the surface of the MWNTs, with the size ranging from 5 to 15 nm. The hysteresis loops of the decorated MWNTs were measured by a vibrating sample magnetometer (VSM), the ferromagnetic signature emerged with the saturated magnetization of 5.8 emu/g, and the coercive of 310 Oe.     

Determination of DNA-base orientation on carbon nanotubes through directional optical absorbance

We develop an approach for determining the orientation of DNA bases attached to carbon nanotubes (CNTs), by combining ab initio time-dependent density functional theory and optical spectroscopy measurements. The structures we find are in good agreement with the geometry of nucleosides on a (10,0) CNT obtained from molecular simulations using empirical force fields. The results shed light into the complex interactions of the DNA-CNT system, a candidate for ultrafast DNA sequencing through electronic probes.     

Vibration and orientation of diatomic molecules flowing through small carbon nanotubes

With their unique long cylindrical shape, carbon nanotubes may one-day form nozzles for nano-scale printing or flow into a chamber. Since the scale of the flowing molecules is similar to the diameter of the nanotubes, molecular vibration, orientation and density become influenced by the confinement during flow. We have studied the flow of diatomic molecules through carbon nanotube nozzles using non-equilibrium molecular dynamics simulations, in an effort to gain a greater understanding about the fundamental properties of such molecules in such a setting. The frequency of vibration of the molecules is shown to be dependent on the density inside the nanotubes and follow the same relation as an experimental micro-scale density-frequency study suggests, although only for nanotubes above a certain diameter. Meanwhile no relation is found between the frequency of vibration and the flow rate. The effect of nanotube diameter on the orientation of the molecules is also examined in detail, showing the transition between axial and radial orientation, with "pull" and "push" effects determining the orientation.     

Coated double-walled carbon nanotubes with ceria nanoparticles

Ce(OH)₃ particles with diameters of about 3–8 nm were deposited on the double-walled carbon nanotube (DWNT) bundles evenly by the chemical reaction of CeCl₃ and KOH solution. The Ce(OH)₃/DWNT films changed into CeO₂/DWNT films by heating the samples to 450 °C for 20 min. The atomic ratio of Ce/C in the CeO₂/DWNT film was about 1:35 calculating from the XPS spectra. The deposition mechanism of Ce(OH)₃ on DWNT bundles was also discussed.     

Fabrication and characterisation of multiwalled carbon nanotubes decorated by magnetic Ni nanoparticles

Abstract

Magnetic carbon nanotube (CNT) composites have been successfully fabricated by employing a microwave assisted method after sensitisation and activation. The phase structures and morphologies of the composites were characterised in detail by transmission electron microscope and X-ray powder diffraction. The results show that sensitisation and activation are absolutely necessary for a dense layer of magnetic nanoparticles obtained on the surface of CNTs. Magnetic measurements using a vibrating sample magnetometer demonstrate that the prepared composites are ferromagnetic.     

Multi-walled carbon nanotubes and metallic nanoparticles and their application in biomedicine

Interdisciplinary research has become a matter of paramount importance for novel applications of nanomaterials in biology and medicine. As such, many disciplines-physics, chemistry, microbiology, cell biology, and material science-all contribute to the design, synthesis and fabrication of functional and biocompatible devices at the nanometer scale. Since the most areas of cell biology and biomedicine deal with functional entities such as DNA and proteins, mimicry of these structures and function in the nanosize range offers exciting opportunities for the development of biosensors, biochips, and bioplatforms. In this report we highlight the potential benefits and challenges that arise in the manufacture of biocompatible nanoparticles and nano-networks that can be coupled with biological objects. Among the challenges facing us are those concerned with making the necessary advances in enabling affordability, innovation, and quality of manufactured nanodevices for rapid progress in the emerging field of bio-nanotechnology. The convergence of nanotechnology and biomedicine makes nanoscale research highly promising for new discoveries that can cost-effectively accelerate progress in moving from basic research to practical prototypes and products.     

Synthesis and properties of magnetic multi-walled carbon nanotubes loaded with Fe4N nanoparticles

High saturation magnetization (>90 emu/g) multi-walled carbon nanotubes (MWCNTs) and Fe₄N nanoparticles composite were successfully synthesized by gas nitriding at 550 °C. Almost all Fe₄N nanoparticles were evenly distributed inside the carbon nanotubes and formed a special composite microstructure. This composite microstructure shows excellent soft magnetic property, structural stability, and chemical stability at room temperature. The investigations of electromagnetic and microwave absorption performances indicate that microwave absorbing capacity of low frequency band of MWCNTs were greatly improved by addition of Fe₄N nanoparticles.     

Nickel-cobalt nanoparticles supported on single-walled carbon nanotubes and their catalytic hydrogenation activity

Single-walled carbon nanotubes were synthesized from graphite using the arc discharge technique. A nickel/yttrium/graphite mixture was used as the catalyst. After purification by sonication in a Triton X-100 solution, nickel-cobalt metal nanoparticles were deposited on the surface of the single-walled carbon nanotubes. The resulting material and/or the nanotubes themselves were characterized by physisorption, Raman spectroscopy, high-resolution transition electron microscopy and X-ray diffraction. Raman spectroscopy indicates that the nanotubes, prepared by the arc discharge technique, are semi-conducting with a diameter centering at 1.4 nm. The average nickel-cobalt particle size is estimated to be in the region of 8 nm. The catalytic activity of the material was examined for the hydrogenation of unsaturated fatty acid methyl esters obtained from avocado oil. The carbon nanotube supported nickel-cobalt particles effectively hydrogenate polyunsaturated methyl linoleate to monounsaturated methyl oleate. In contrast to a conventional nickel on kieselghur catalyst, further hydrogenation of methyl oleate to undesired methyl stearate was not observed.     

Magnetic properties and transmission electron microscopy studies of Ni nanoparticles encapsulated in carbon nanocages and carbon nanotubes

Three types of carbon nanomaterials, including bamboo-shaped carbon nanotubes with Ni encapsulated and hollow and Ni catalytic particles filled carbon nanocages, have been prepared by methane catalytic decomposition at a relatively low temperature. Transmission electron microscopy observations showed that fascinating fullerene-like Ni–C (graphitic) core–shell nanostructures predominated. Detailed examination of high-resolution transmission electron microscopy showed that the walls of bamboo-shaped carbon nanotubes with quasi-cone catalytic particles encapsulated consisted of oblique graphene planes with respect to the tube axis. The Ni particles encapsulated in the carbon nanocages were larger than that encapsulated in carbon nanotubes, but the diameters of the cores of hollow carbon nanocages were less than that of Ni particles encapsulated in carbon nanotubes, suggesting that the sizes of catalyst particles played an important role during carbon nanomaterial growth. The magnetic properties of the carbon nanomaterials were measured, which showed relatively large coercive force (H_c = 138.4 O_e) and good ferromagnetism (M_r/M_s = 0.325).     

Magnetic properties of carbon nanotubes filled with ferromagnetic metals

Carbon nanotubes (CNTs) encapsulating Fe nanowires were prepared by the chemical vapor deposition (CVD) method using ferrocene as a precursor. The influence of the addition of Pt to an Fe catalyst, which is required for growing CNTs by CVD, on the magnetic properties of the resulting CNTs was examined from the viewpoint of enhancing coercivity. Our results showed that the addition of a Pt layer on the Fe catalyst deposited on a substrate increased the coercivity of the Fe-filled CNT. This increase is due to changes in the easy magnetization axis of the Fe nanowires in the CNTs. This result indicates that the magnetic properties of the Fe-filled CNTs can be tuned by the controlling the growth conditions, which is suitable for applications in areas such as magnetic recording media and medicine.     

Facile attachment of magnetic nanoparticles to carbon nanotubes via robust linkages and its fabrication of magnetic nanocomposites

Magnetic nanoparticles were facilely attached to multi-walled carbon nanotubes (MWCNTs) by high-temperature reaction of ferric triacetylacetonate in 1-methyl-2-pyrrolidone in the presence of carboxylated MWCNTs. X-ray diffraction, transmission electron morphology and thermogravimetric analysis were used to demonstrate the successful attachment of iron oxide nanoparticles to MWCNTs. It was found that the attached nanoparticles were mainly magnetite. Investigations using Fourier transform infrared spectroscopy proved that the tight attachment was due to the robust linkages: metal-carbonyl coordination. Modified carbon nanotubes were introduced into epoxy resins to fabricate magnetic nanocomposites. Magnetic properties were analyzed by vibrating sample magnetometer.     

Glutaraldehyde mediated conjugation of amino-coated magnetic nanoparticles with albumin protein for nanothermotherapy

A novel bioconjugation of amino saline capped Fe3O4 magnetic nanoparticles (MNPs) with bovine serum albumin (BSA) was developed by applying glutaraldehyde as activator. Briefly, Fe3O4 MNs were synthesized by the chemical co-precipitation method. Surface modification of the prepared MNPs was performed by employing amino saline as the coating agent. Glutaraldehyde was further applied as an activation agent through which BSA was conjugated to the amino-coated MNPs. The structure of the BSA-MNs was confirmed by FTIR analysis. Physico-chemical characterizations of the BSA-MNPs, such as surface morphology, surface charge and magnetic properties were investigated by Transmission Electron Microscopy (TEM), zeta-Potential and Vibrating Sample Magnetometer (VSM), etc. Magnetic inductive heating characteristics of the BSA-MNPs were analyzed by exposing the MNPs suspension (magnetic fluid) under alternative magnetic field (AMF). The results demonstrate that BSA was successfully conjugated with amino-coated MNs mediated through glutaraldehyde activation. The nanoparticles were spherical shaped with approximately 10 nm diameter. Possessing ideal magnetic inductive heating characteristics, which can generate very rapid and efficient heating while upon AMF exposure, BSA-MNPs can be applied as a novel candidature for magnetic nanothermotherapy for cancer treatment. In vitro cytotoxicity study on the human hepatocellular liver carcinoma cells (HepG-2) indicates that BSA-MNP is an efficient agent for cancer nanothermotherapy with satisfied biocompatibility, as rare cytotoxicity was observed in the absence of AMF. Moreover, our investigation provides a methodology for fabrication protein conjugated MNPs, for instance monoclonal antibody conjugated MNPs for targeting cancer nanothermotherapy.     

Tuning photoresponse through size control of Cu nanoparticles deposited on multi wall carbon nanotubes

In this paper we illustrate a simple method for the production of multiwall carbon nanotubes thin films decorated with copper metal nanoparticles. The structural information obtained from the transmission electron microscopy study performed on samples differing in the quantity of deposited Copper was linked to the opto-electronic properties evaluated with photo-electrochemical measurements. The photo-response evaluated in terms of incident photon-to-charge carrier generation efficiency varied for different sized-Cu-multiwall carbon nanotubes samples across all the visible and near-ultraviolet photon energy range with respect to the response of bare carbon tubes. The photo-response from the sample covered with of 0.5 nm Cu nominal thickness, reached 10.2%, a value 2 times higher than that measured for bare carbon tubes of 5.9%. While this value decreased to 2.8% when the Cu nominal coverage thickened up to 3 nm. The increase in the photo-response found was interpreted as being the result of a remarkable charge transfer between the Cu metal nanoparticles and the carbon atoms in the tube due to the formation of a strong ionic bond at their interface. The results obtained prove that the metal nanoparticle-carbon nanotube composites have optical, electrical and structural properties that can be applied in a variety of nanoscale architectures for novel photo-electrochemical devices.     

Fe3O4纳米粒子修饰碳纳米管的制备及其磁学性能（英文）

通过FeCl2.4H2O和FeCl3.6H2O混合共沉淀,合成平均粒径为6 nm和10 nm的Fe3O4纳米粒子。然后将两种Fe3O4纳米粒子分别与经HNO3氧化处理的多壁碳纳米管(MWCNTs)置于乙醇水溶液(水和乙醇的体积比为1∶1)中,在超声波作用下制备Fe3O4/MWCNT复合材料。用高分辨透射电子显微镜、X-射线光电子能谱、振动样品磁强计、X射线衍射仪、热重分析仪对所制备的Fe3O4/MWCNT复合材料进行表征。结果表明:由6 nm和10 nm Fe3O4纳米粒子所制备的Fe3O4/MWCNT复合材料中,Fe3O4的质量分数分别为26.65%和29.3%,相应的磁饱和强度分别为16.5 emug-1和7.5 emug-1。