The formation of magnetite nanoparticles on the sidewalls of multi-walled carbon nanotubes

Linear polyethyleneimine (PEI) was used as a non-covalent functionalizing agent to modify multi-walled carbon nanotubes (MWCNTs). Fe₃O₄ nanoparticles were then formed along the sidewalls of the as-modified MWCNTs through a simple solvothermal method. X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the MWCNT/Fe₃O₄ nanocomposites. Results indicated that Fe₃O₄ nanoparticles with diameters ranging from 50 to 200 nm were attached to the surface of the MWCNTs by electrostatic interaction. PEI was found to improve the electrical conductivity of the MWCNT/Fe₃O₄ nanocomposites. The magnetic saturation value of these magnetic nanocomposites was 61.8 emu g⁻¹. These magnetic MWCNT/Fe₃O₄ nanocomposites are expected to have wide applications in bionanoscience and technology.     

Preparation of Cu nanoparticles on carbon nanotubes by solution infusion method and calcining in ambient atmosphere

Copper nanoparticles were synthesized using carbon nanotubes as a template. The process involved neither pre-purification nor an additional reducing agent. This method was simple and the Cu nanoparticles were uniformly loaded on the carbon nanotubes. TEM, SEM, XRD and EDX were used to examine the morphology of the Cu particles. The diameter of the carbon nanotubes is about 70-90 nm and the size of the nanoparticles is about 50-70 nm.     

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。     

Oriented growth of magnetite along the carbon nanotubes via covalently bonded method in a simple solvothermal system

A new type of CNTs/magnetite hybrid material was prepared via covalently bonded method in a simple solvothermal system using FeCl₃ as iron source, ethylene glycol as the reducing agent, and 4-aminophenoxyphthalonitrile-grafted CNTs as templates. The magnetite nanoparticles, with the diameters of 70-80 nm, were self-assembled along the CNTs. The FTIR, UV-vis and DSC revealed that a stable covalent bond between nitriles group and iron ion promoted the oriented growth of magnetite nanoparticles along the CNTs, resulting in good dispersibility and solution storage stability. The magnetic properties measurements indicated that a higher saturated magnetization (70.7 emu g⁻¹) existed in the CNTs/magnetite hybrid material, which further enhanced the electromagnetic properties. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.     

碳纳米管承载纳米Fe_3O_4颗粒的制备(英文)

采用一种简单又经济的方法将Fe3O4纳米颗粒填充到碳纳米管中。透射电镜(TEM)、扫描电镜(SEM)及其能谱附件(EDX)和X射线多晶衍射(XRD)测试结果表明:Fe3O4纳米颗粒成功地填充到碳纳米管中。材料的磁性能测试结果表明:碳纳米管中填充Fe3O4纳米颗粒后,在常温下具有超顺磁性,其饱和磁化强度由0.35emu/g增大到了13.15emu/g。Fe3O4纳米颗粒填充的碳纳米管可望应用于工程和医学领域。     

Nickel nanoparticles decoration of ordered mesoporous silica thin films for carbon nanotubes growth

We report in situ successive depositions of nickel nanoparticles and carbon nanotubes (CNTs) on ordered mesoporous silica films used as template for the catalyst particles. The mesoporous films are synthesized by the evaporation-induced self-assembly process from tetraethyl orthosilicate derived oligomers and a di-block copolymer from dip-coating deposition method. The substrates are decorated with Ni nanoparticles through Ion Beam Deposition and posterior annealing to induce metal coalescence in the mesoporous cavities. CNTs were then grown by Chemical Vapor Deposition in the presence of an electric field. These techniques provide a simple control method producing ordered arrangements of catalyst nanoparticles and ordered nanostructures for large area applications.     

Dispersion of metal nanoparticles on carbon nanotubes with few surface oxygen functional groups

Homogeneous dispersion of metal oxide nanoparticles was achieved on carbon nanotubes (CNTs) even with a very small amount of surface oxygen functional groups (SOFGs) aided by using ethylene glycol (EG) and sodium hydroxide during the process. Similar particle size distributions were obtained for iron deposited on CNTs containing various amounts of SOFGs. We proposed that formation of hydrogen bonds between EG on the CNT surface and sodium hydroxide is likely responsible, which creates precipitating sites for iron ions on the CNT surface. This facile method is expected to find applications not only for catalysis but also in the fields such as sensors and magnetic materials in particular where a perfect sp² hybridized carbon structure is preferred.     

Percolation behaviour of polypropylene glycol filled with multiwalled carbon nanotubes and Laponite

The percolation behaviour of the hybrid composites of polypropylene glycol (PPG) filled with multiwalled carbon nanotubes (MWCNTs) and Laponite RD (Lap), or with MWCNTs and organo-modified Laponite (LapO) was studied by wide angle X-ray diffraction (XRD), microscopic image analysis, and electrical conductivity measurements. Cetyltrimethylammoniumbromide (CTAB) was used as an organo-modifier of Laponite. The Lap and LapO were found to have rather different affinity to PPG. XRD data have evidenced finite PPG integration inside Lap and complete exfoliation of LapO stacks in a PPG matrix. In PPG + MWCNT composites containing no Lap or LapO, increase of MWCNT concentration above the critical value C_p ∼ 0.4 wt% resulted in percolation. The value of the percolation threshold, C_p, was practically the same for hybrid PPG + MWCNT + Lap composites. However, it noticeably decreased (C_p ∼ 0.2 wt%) in PPG + MWCNT + LapO materials. The observed behaviour of the percolation threshold may be attributed to the effects exerted by LapO on the size of MWCNT aggregates, state of their dispersion and homogeneity of their spatial distribution.     

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.     

Preparation and optical limiting properties of carbon nanotubes coated with Au nanoparticle composites embedded in silica gel-glass

Au nanoparticle (NP) coated carbon nanotubes (CNTs) (CNTs@AuNPs) embedded in silica gel-glass (CNTs@AuNPs/silica gel-glass) were prepared by the sol-gel technique. Subsequent analysis confirmed the successful introduction of the CNTs@AuNPs to the silica gel-glass. Coating with AuNPs dramatically improved the mechanical properties of the silica gel-glass matrix, despite the higher Brunauer-Emmett-Teller (BET) specific surface area and pore volume of the CNTs@AuNPs/silica gel-glass compared with CNT/silica gel-glass. The optical limiting (OL) properties of the CNTs@AuNPs measured at a laser wavelength of 532 nm were slightly weaker after introduction into the solid-state matrix. This reduction is probably attributed to the synergistic nonlinear optical effects of reverse saturable absorption arising from the CNTs and saturable absorption from the AuNPs embedded in the silica gel-glass.     

An efficient numerical model for vibration analysis of single-walled carbon nanotubes

This paper presents a linear spring-based element formulation for computation of vibrational characteristics of single-walled carbon nanotubes (CNTs). Three-dimensional nanoscale elements and corresponding elemental equations are developed for the numerical treatment of the dynamic behaviour of single-walled CNTs, including appropriate stiffness and mass characteristics. The atomistic microstructure of nanotubes is used to assemble the elemental equations and construct the dynamic equilibrium equation. The developed elements simulate the relative translations and rotations between atoms as well as the mass of the atoms. In this way, molecular mechanics theory can be applied directly because the atomic bonds are modelled by using exclusively physical variables such as bond stretching. The modelling is regenerative and can provide simulations for different geometric characteristics of the nanotubes. Numerical results are presented that illustrates new natural frequencies and mode shapes, going beyond the usual ones for various nanotubes under different support conditions and defects. Comparisons with corresponding numerical predictions from the literature, where they are possible, show very good agreement.     

In situ-polymerization of fluorinated polyoxadiazole with carbon nanotubes in poly(phosphoric acid)

In the present work, in-situ polymerizations of fluorinated polyoxadiazole through a polycondensation reaction of A-A (hydrazine sulphate) and B-B (aromatic dicarboxylic acid) monomers with multiwalled carbon nanotubes (MWCNT) in poly(phosphoric acid) were performed in the frame of time 3 to 48 h. The effect of acid treatment in polyphosphoric acid on the CNT structure was analyzed by SEM, TGA and FTIR. Fluorinated polyoxadiazole/MWCNTs soluble in organic solvents with high molecular weights (around 200 000 g/mol) could be synthesized in 3 h. The fluorinated polyoxadiazole/MWCNTs exhibits high thermal stability with degradation temperature at about 460 °C.     

Morphology and electrochemical properties of amphiphilic viologen functionalized multiwalled carbon nanotube hybrids in Langmuir-Blodgett films

Amphiphilic viologens were electrostatically adsorbed on the surface of multiwalled carbon nanotubes (MWCNT) to form viologen-MWCNT hybrids, in which the content of viologens was about 5-10% in weight. Although both viologens and MWCNT hardly dispersed in the water-insoluble organic solvents, the as-prepared viologen-MWCNT hybrids were well dispersed in them with a strong long-term stability, the features of which provided a possibility to prepare their insoluble monolayers at the air-water interface. The surface pressure-area isotherms of these hybrids revealed that they could form stable monolayers, which were transferred on the substrate surfaces by the Langmuir-Blodgett (LB) method. Morphologies of the LB films were characterized by using scanning electron microscopy and atomic force microscopy, the images of which revealed the formation of network two- or three-dimensional films of the functionalized MWCNT. Cyclic voltammograms of the LB films revealed one or two couples of one electron transfer process corresponding to the viologen-MWCNT hybrids with the cathodic and anodic potentials closely related to the alkyl chains of the viologens.     

High-density assembly of gold nanoparticles to multiwalled carbon nanotubes using ionic liquid as interlinker

Gold nanoparticles were deposited onto the surface of carbon nanotubes through an interlinker of ionic liquid terminated with hydroxyethyl units at one end and exchangeable chloride counterions at the other end. The morphology, structure, and composition of the resulting hybrids were characterized by transmission electron microscopy and X-ray diffraction. A very high density of gold nanoparticles was homogeneously dispersed and well-separated from one another on the modified multi-walled carbon nanotubes. The optical absorption of the products was observed by UV-visible spectroscopy. The results imply that the obtained carbon nanotube-gold nanocomposites have a good application potential in catalysis, sensor, and fuel cells.     

The toxicity to plants of the sewage sludges containing multiwalled carbon nanotubes

The aim of this study was to evaluate the toxicity of sewage sludges containing multiwalled carbon nanotubes (CNTs) with an outer diameter <10 nm (CNT10) or 40-60 nm (CNT60) to Lepidium sativum (cress), Sorghum saccharatum (sorgo), Solanum lycopersicon (tomato), Raphanus sativus (radish) and Cucumis sativus (cucumber). CNTs were also incubated in sewage sludge for 7 or 31 days to determine the effect of CNT aging on sewage sludge phytotoxicity. The influence of CNTs on 4 different sewage sludges was tested. The CNTs' influence on sludge toxicity varied with respect to the CNTs' outer diameter, type of sewage sludges and the plants tested. No significant influence of CNT concentration on phytotoxicity was noted. In the case of two sludges, a positive influence of CNTs on seed germination and root growth was observed. Depending on the CNTs' outer diameter, CNT aging decreased (CNT10) or increased (CNT60) sewage sludge phytotoxicity.     

Adsorption thermodynamic and kinetic studies of trihalomethanes on multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) were purified by mixed HNO3/H2SO4 solution and were employed as adsorbents to study adsorption kinetics and thermodynamics of trihalomethanes (THMs) from chlorinated drinking water. The amount of THMs adsorbed onto CNTs decreased with a rise in temperature and high adsorption capacities were found at 5 and 15 degrees C. Under the same conditions, the purified CNTs possess two to three times more adsorption capacities of CHCl3, which accounts for a major portion of THMs in the chlorinated drinking water, than the commercially available PAC suggesting that CNTs are efficient adsorbents. The thermodynamic analysis revealed that the adsorption of THMs onto CNTs is exothermic and spontaneous.     

A synthesis of fluorescent starch based on carbon nanoparticles for fingerprints detection

A pyrolysis method for synthesizing carbon nanoparticles (CNPs) were developed by using malic acid and ammonium oxalate as raw materials. The incorporation of a minor amount of carbon nanoparticles into starch powder imparts remarkable color-tunability. Based on this phenomenon, an environment friendly fluorescent starch powder for detecting latent fingerprints in non-porous surfaces was prepared. The fingerprints on different non-porous surfaces developed with this powder showed very good fluorescent images under ultraviolet excitation. The method using fluorescent starch powder as fluorescent marks is simple, rapid and green. Experimental results illustrated the effectiveness of proposed methods, enabling its practical applications in forensic sciences.     

Investigation of the microwave-absorbing properties of Fe-filled carbon nanotubes

Carbon nanotubes encapsulated Fe nanowire composites were synthesized via pyrolyzing of ferrocene. The reflection loss (R.L.), matching frequency (f_m) and matching thickness (d_m) were calculated using the theory of the absorbing wall. The electromagnetic properties and microwave-absorbing characteristic effects by the encapsulation of metal Fe were investigated in a frequency range of 8-18 GHz. With matching thickness of 3.5 mm, the maximum reflection loss is about − 22.73 dB for the absorber. The bandwidth corresponding to the reflection loss below − 10 dB is more than 4.22 GHz. With increasing thickness, the peak value of the reflection loss shifts to a lower frequency.     

Enhanced electron emission from titanium coated multiwalled carbon nanotubes

Enhanced field emission properties and improved crystallinity of titanium (Ti) coated multiwalled carbon nanotubes (MWCNTs), prepared by microwave plasma enhanced chemical vapour deposition have been observed. Ti films of extremely low thicknesses (0.5 nm, 1.0 nm and 1.5 nm) were coated over carbon nanotubes (CNTs) and their field emission behaviour was investigated. The turn on field of Ti coated CNTs was found to be low (~ 0.8 V/μm) as compared to pristine CNTs (~ 1.8 V/μm). The field enhancement factor for Ti coated CNTs was quite large (~ 1.14 × 10⁴) as compared to pristine CNTs (~ 6 × 10³). This enhancement in electron emission is attributed to the passivation of defects and improved crystallinity of CNTs. Surface morphological and microstructural studies were carried out to investigate the growth of pristine and Ti coated CNTs. It was observed that Ti nanoclusters adsorb on the edges of MWCNTs and increase their crystallinity. This increase is directly correlated with the thickness of Ti film deposited. Micro Raman spectroscopy confirmed the improved crystallanity of Ti coated CNTs.