Facile synthesis of Au nanoparticles supported on polyphosphazene functionalized carbon nanotubes for catalytic reduction of 4-nitrophenol

Carbon nanotubes (CNTs) functionalized with cyclotriphosphazene-containing polyphosphazenes (PZS) were found to cause the facile immobilization of Au nanoparticles on the surface. The PZS functional layers not only improved the dispersion of CNTs in aqueous solution but also used as a platform for subsequent immobilization of Au nanoparticles. The functionalized CNTs and the Au@PZS@CNTs nanohybrids were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrometer, X-ray diffraction, thermogravimetric analysis, Atomic absorption spectrum, and X-ray photoelectron spectroscopy. The results showed that the PZS layers with thickness of about 25 nm were formed uniformly on CNT surfaces by polycondensation between hexachlorocyclotriphosphazene and 4,4′-sulfonyldiphenol, and that high density of homogeneously dispersed spherical Au nanoparticles with average size of 6 nm was immobilized on their outer surface. Meanwhile, the catalytic activity and reusability of the Au@PZS@CNTs nanohybrids were investigated by employing the reduction of 4-nitrophenol into 4-aminophenol by NaBH₄ as a model reaction.     

Decoration of carbon nanotubes with nearly monodisperse MFe2O4 (MFe2O4, M = Fe, Co, Ni) nanoparticles

Magnetic monodisperse ferrite MFe₂O₄ (M = Fe, Co, Ni) nanoparticles have been successfully deposited on carbon nanotubes (CNTs) by in situ high-temperature hydrolysis and inorganic polymerization of metal salts and CNTs in polyol solution. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometry (EDS) and vibrating sample magnetometer (VSM) investigations were used to characterize the final products. The influencing factors for formation of CoFe₂O₄ nanoparticles along CNTs have also been discussed briefly. The main advantage of this synthetic strategy is that it is beneficial for the fabrication of magnetic CNTs with a compact layer of nanoparticles and could be extended to prepare series of ferrite/CNTs nanocomposites via the substitution of metal cations.     

Microwave-assisted synthesis of pt nanocrystals and deposition on carbon nanotubes in ionic liquids

In this work, a simple, fast and efficient route is presented for the metal (such as Pt, Rh, etc.) nanocrystal synthesis and deposition on carbon nanotubes (CNTs) in ionic liquids (ILs) via microwave heating. In this method, inorganic salts (such as H2PtCl6.4H2O, RhCl3.2H2O, etc.) dissolved in ILs, 1,1,3,3-tetramethylguanidinium trifluoroacetate or 1,1,3,3-tetramethylguanidinium lactate, were reduced to metal nanoparticles by glycol with the aid of microwave heating, and the produced metal nanoparticles could be decorated on CNTs in the presence of CNTs in ILs. The resulting nanomaterials were characterized by means of transmission electron microscopy and X-ray diffraction. It was demonstrated that the homogeneously dispersed Pt nanocrystals with the size of 2-3 nm were obtained using H2PtCl6.4H2O as precursor, and they deposited on CNTs with the similar size when CNTs was present in ILs. This technique also can be extended to fabricate other noble metal nanocrystals (including Rh, Au, etc.) and corresponding CNT composites.     

Preparation of ultrafine chalcopyrite nanoparticles via the photochemical decomposition of molecular single-source precursors

The synthesis and characterization of ultrafine CuInS2 nanoparticles are described. Ultraviolet irradiation was used to decompose a molecular single source precursor, yielding organic soluble approximately 2 nm sized nanoparticles with a narrow size distribution. UV-vis absorption, 1H and 31P{1H} NMR, and fluorescence spectroscopies and mass spectrometry were used to characterize decomposition of the precursors and nanoparticle formation. The nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy energy dispersive X-ray spectroscopy, powder X-ray diffraction (XRD), electron diffraction, inductively coupled plasma analysis, UV-vis absorption spectroscopy, and fluorescence spectroscopy. They have a wurzite-type crystal structure with a copper-rich composition. The hypsochromic shift in their emission band due to quantum confinement effects is consistent with the size of the nanocrystals indicated in the HRTEM and XRD analyses.     

Deposition of platinum nanoparticles on carbon nanotubes by supercritical fluid method

Carbon nanotube-supported platinum nanoparticles with a 5-15 nm diameter size range can be synthesized by hydrogen reduction of platinum(ll) acetylacetonate in methanol modified supercritical carbon dioxide. X-ray photoelectron spectroscopy and X-ray diffraction spectra indicate that the carbon nanotubes contain zero-valent platinum metal and high-resolution transmission electron microscopy images show that the visible lattice fringes of platinum nanoparticles are crystallites. Carbon nanotubes synthesized with 25% by weight of platinum nanoparticles exhibit a higher activity for hydrogenation of benzene compared with a commercial carbon black platinum catalyst. The carbon nanotube-supported platinum nanocatalyst can be reused at least six times for the hydrogenation reaction without losing activity. The carbon nanotube-supported platinum nanoparticles are also highly active for electrochemical oxidation of methanol and for reduction of oxygen suggesting their potential use as a new electrocatalyst for proton exchange membrane fuel cell applications.     

Solvent-free microwave-assisted synthesis of tenorite nanoparticle-decorated multi-walled carbon nanotubes

Copper-decorated carbon nanotubes (CNTs) have important applications as precursors for ultra-conductive copper wires. Tenorite-decorated CNTs (CuO-CNTs) are ideal candidates and are currently developed using laborious processes. For this reason, we have developed a facile and scalable method for the synthesis of CuO-CNTs from copper acetate. It was found that the optimal loading of copper acetate onto the CNTs was 23.1 wt% and that three 1-minute microwave treatments were sufficient for the decomposition of copper acetate to copper oxide. The loading of copper oxide onto the nanotubes was confirmed using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. The materials were characterised using X-ray diffraction and scanning electron microscopy.     

Preparation and characterization of γ-MnO2/CNTs nanocomposite

A layer of manganese dioxides (γ-MnO₂) was adsorbed upon carbon nanotubes (CNTs) surface by using a chemical deposit process. The morphologies of the MnO₂/CNTs composite were characterized using transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and laser Raman spectroscopy (RS). It is found that the adsorbed layer belongs to the γ-MnO₂ nanoparticles in the size of about 10 nm, and coated homogeneously around the CNTs. It is expected that this γ-MnO₂/CNTs composite will be applied to make supercapacitors.     

Continuous synthesis of carbon nanotubes using a metal-free catalyst by CVD

This study demonstrates the first example of the use of a metal-free catalyst for the continuous synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD). In this paper silica nanoparticles produced from the thermal decomposition of PSS-(2-(trans-3,4-Cyclohexanediol)ethyl)-Heptaisobutyl substituted (POSS) were used as catalyst and ethanol was served as both the solvent and the carbon source for nanotube growth. The POSS/ethanol solution was nebulized by an ultrasonic beam. The tiny mists were continuously introduced into the CVD reactor for the growth of CNTs. The morphology and structure of the CNTs have been investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The obtained CNTs have a multi-walled structure with diameters mainly in the size range from 13 to 16 nm. Detailed investigations on the growth conditions indicate that the growth temperature and POSS concentration are important for achieving high-quality nanotubes, and that the existing of small amount of water in ethanol is effective to remove amorphous carbon species during the formation of CNTs. The mass production of CNTs without any metal contaminant will provide a chance for investing and understanding the intrinsic properties of CNTs and applications particularly in nanoelectronics and biomedicines.     

Sonochemical-assisted synthesis and characterization of CeO<Subscript>2</Subscript> nanoparticles and its photocatalytic properties

In the present study, cerium oxide (CeO₂) nanoparticles were prepared through sonochemical-assisted method, using (NH₄)₂Ce(NO₃)₆, hydrazine and ethylenediamine as precursors. Also, the effects of concentration of precursors as well as reaction time on the morphology and size of nanoparticles were investigated. The synthesized CeO₂ nanoparticles were characterized by X-ray diffraction patterns, energy-dispersive X-ray spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and diffuse reflectance spectroscopy. The results indicate that the estimated particle size of synthesized CeO₂ nanoparticles is about 20–30 nm. Furthermore, photocatalytic activities of CeO₂ nanoparticles were investigated by degradation of methylene blue under UV-light irradiation.     

Facile carbothermal reduction approach to hybrid platinum-carbon nanotubes composite for electrocatalytic oxidation of ethanol

We have provided an effective, environmentally benign approach for the synthesis of hybrid platinum-carbon nanotubes (Pt-CNTs) composite via a CNTs-guided carbothermal reduction. The materials were characterized by transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results revealed that CNTs acted as both support and reducing agent, and therefore the Pt nanoparticles with an average particle size of 3.5 nm could uniformly disperse onto the surface of CNTs. Moreover, as-fabricated Pt-CNTs exhibited the enhanced electrocatalytic activity and stability for ethanol oxidation in both acidic and alkaline media, in comparison to that prepared by electrochemical deposition. This approach greatly enlarges the practical application areas of hybrid Pt-CNTs composite materials.     

Facile synthesis of superparamagnetic Fe-doped ZnO nanoparticles in liquid polyols

A facile polyol process was established to prepare superparamagnetic Fe-doped ZnO nanoparticles in a liquid polyol using Fe(acac)₃ and Zn(acac)₂ as precursors and triethylene glycol as the solvent. Scanning electron microscopy (SEM) images showed that as-prepared nanoparticles are uniform in size. X-ray diffraction (XRD) analysis revealed that the nanoparticles are of wurtzite structure without an impure phase. The successful doping of the Fe element into the ZnO host was evident by XRD lines shifting and energy dispersive X-ray spectroscopy (EDS) results. Magnetization measurements demonstrated that the Fe-doped ZnO nanoparticles were superparamagnetic at room temperature.     

Fabrication of PtNi bimetallic nanoparticles supported on multi-walled carbon nanotubes

Platinum/nickel bimetallic nanoparticles supported on multi-walled carbon nanotubes (xPtNi/CNTs) were synthesised. The fabrication process includes the chemical modification on the graphene surface of CNTs by acid treatment and the subsequent deposition of Pt or PtNi bimetallic nanoparticles with different compositions of Pt (x = 100, 90, 80 and 70 wt%). The deposition was carried out using ethylene glycol as a reducing agent in the polyol method or using poly(amidoamine) dendrimer as a platform and sodium borohydride as a reducing agent to load the metal nanoparticles on the CNT surface. The structures of the produced PtNi/CNT nanoparticles were investigated by ultraviolet absorption spectra, X-ray diffraction (XRD) and the composite ratio consisting of 70 wt% of metal content and 30 wt% of CNTs was confirmed by the thermogravimetric analysis. The morphology and the phase identification of the produced PtNi/CNT nanoparticles were investigated by high-resolution scanning electron microscope, transmission electron microscope and XRD measurements. It was observed that the deposited Pt and PtNi bimetallic nanoparticles on the surface of CNTs had average particle sizes of 2–16 nm, when they were prepared from the polyol method. On the other hand, the PtNi/CNT nanoparticles prepared by using a dendrimer as an intermediate had a smaller particle size and more uniform size distribution of the quantum dot size ranged from 2 to 4 nm.     

Synthesis and characterization of large area well-aligned carbon nanotubes by ECR-CVD without substrate bias

Large area, well-aligned carbon nanotubes (CNTs) were synthesized on porous silicon by electron cyclotron resonance chemical vapor deposition (ECR-CVD). No bias was applied on the substrate in this experiment. CH₄ and H₂ were used as source gases and Fe₃O₄ nanoparticles as the catalyst. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), and Raman spectrum were used to evaluate the structure and composition. The results show that these CNTs have varying outer diameters from 10 to 90 nm and uniform length over 10 μm. They display hollow tubular and chain structures. The possible formation mechanism of aligned CNTs is discussed.     

Solvothermal synthesis of necklace-like carbon nanotube/ceria composites

The necklace-like carbon nanotube (CNT)/ceria composites have been synthesized by a simple solvothermal method. The composites are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction as well as X-ray photoelectron spectroscopy. It is found that the necklace-like nanostructures are a hybrid of face-centered cubic ceria and CNTs, and these beaded ceria particles with a diameter of 80-120 nm are distributed discontinuously along the axis of CNTs. A possible formation mechanism has been suggested to explain the formation of necklace-like CNT/ceria composites, which indicates that this synthesis route is promising and may be extended to fabricate other beaded nanoparticles along CNTs.     

嵌段聚合物模板合成ZnS纳米粒子及其表征

以嵌段聚合物羟基化SBS（SBS-OH）为模板,乙酸锌和硫化钠为前驱物,制备了ZnS纳米粒子。采用紫外-可见吸收光谱（UV-Vis）、荧光光谱（PL）、广角X射线衍射（WAXD）及透射电子显微镜（TEM）对ZnS纳米粒子进行了表征。结果表明,SBS-OH可以在ZnS纳米粒子的生长过程中,起到较好的模板作用,随SBS-O...     

Preparation of conductive polypyrrole-palladium composite nanospheres by inverse microemulsion polymerization

Conductive polypyrrole-palladium (PPy-Pd) composite nanospheres of about 50 nm in diameter, containing dispersed Pd metal nanoparticles of about 2-4 nm in size, were prepared in a 1-step oxidative polymerization of pyrrole by Pd(NO3)2. Pyrrole was oxidized by Pd(NO3)2 in an inverse microemulsion polymerization system, yielding PPy nanospheres and elemental Pd nanoparticles simultaneously. Palladium nanoparticles were uniformly dispersed in the nanospheres of PPy chains. The latter also exhibited an enhanced effective conjugation. The chemical composition of the PPy-Pd composite nanospheres was characterized by X-ray photoelectron spectroscopy and FTIR spectroscopy. The crystalline structure of the Pd nanoparticles was deduced from X-ray diffraction patterns. The morphology of the composites was revealed by scanning and transmission electron microscopy.     

Low temperature synthesis of ZnSe nanoparticles

Synthesis of thioglycerol capped zinc selenide nanoparticles with a relatively narrow size distribution by a simple and inexpensive low temperature (~ 80 °C) wet chemical method is reported here. Main advantage of this method is the use of non-toxic precursors. The size of the nanoparticles can be varied easily by changing the concentration of the capping agent. The extracted nanoparticles remain stable under normal atmospheric conditions and can be redispersed in suitable solvents. The sharp absorption features obtained in the UV-Visible absorption spectra reveal the formation of monodispersed ZnSe nanoparticles. The nanoparticles were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, UV-Visible absorption spectroscopy, photoluminescence and transmission electron microscopy.     

A simple and facile method to synthesize Co3O4 nanoparticles from metal benzoate dihydrazinate complex as a precursor

This report describes the novel synthesis of cobalt oxide (Co₃O₄) nanoparticles from corresponding metal benzoate dihydrazinate complex as a precursor followed by thermal decomposition. Transmission electron microscopy (TEM) revealed nearly uniform nanoparticles with an average particle size of around 20 nm. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) demonstrated that the nanoparticles were composed of pure cubic phase polycrystalline Co₃O₄. The nanoparticles were also confirmed by Raman spectroscopy. In principle, this simple and inexpensive synthetic procedure can be employed to prepare other transition metal oxide nanoparticles.     

In situ prepared polypyrrole–Ag nanocomposites: optical properties and morphology

Polypyrrole–silver (PPy–Ag) nanocomposites with various silver contents have been synthesized via a kinetically favorable one-step chemical oxidative polymerization process. The oxidant, ammonium persulfate, was used to oxidize pyrrole monomer for growing chains of PPy. And AgNO₃ was used as a precursor for metallic silver nanoparticles. The detailed characterization techniques, UV–Vis–NIR, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy (TEM), have been used to reveal electronic environment, structure, and morphology of composites as well as as-synthesized PPy. The synthesis environment prior to polymerization has also been investigated by absorption spectroscopy. The TEM images of PPy–Ag nanocomposites reveal that silver nanoparticles are deeply embedded into the polymer matrix in addition to surface adsorption. It is observed that the size distribution of inorganic nanoparticles (ca. 4–10 nm, depending on the metal ion concentrations) as well as structural morphology is altered by the initial concentrations of silver ions.     

The improvement of methanol oxidation using nano-electrocatalysts

ABSTRACT

In this study, a nano-scale perovskite LaMnO₃ (LaMnO₃NPs) was synthesised by a rapid microwave-assisted co-precipitation method and characterised by X-ray powder diffraction, Fourier transform infrared, scanning electron microscopy and energy dispersive X-ray techniques. A modified glassy carbon electrode with Pt nanoparticles (PtNPs), functionalised multi-walled carbon nanotubes (CNTs) and LaMnO₃NPs as multifunctional catalyst was prepared and furthermore, its catalytic activity toward methanol oxidation was investigated. Based on the electrochemical studies, the PtNPs–CNTs–LaMnO₃NPs nanocomposite showed considerable activity for methanol oxidation in comparison to PtNPs, PtNPs–CNTs and PtNPs–LaMnO₃NPs. The results displayed the adding of CNTs and LaMnO₃NPs into PtNPs catalyst and the use of a more porous matrix of chitosan can improve the anode performance for methanol oxidation. The transition metals presence at catalyst structure caused to catalyse the methanol dehydrogenation. The decreasing the poisoning rate of the PtNPs with intermediates and by-products of anodic reaction was observed due to the bi-functional effect electrical and oxygen ion conductive perovskite. Direct methanol fuel cell (DMFC) was designed, assembled and tested with suggested PtNPs–CNTs–LaMnO₃NPs nanocomposites as anodic catalyst at variety conditions. The effect of experimental factors such as temperature and methanol concentration on DMFC performances was investigated and optimised.