Self-assembly of versatile tubular-like In(2)O(3) nanostructures

Versatile indium oxide tubular nanostructures (well-aligned nanotube arrays, flower-like tubular structures, and square nanotubes) were fabricated by a facile and reliable chemical vapor deposition (CVD) technique, taking advantage of the self-assembly property and substrate-induced epitaxial growth mechanism. The technique has a few advantages, such as low growth temperature, nonexistence of catalyst, template-free synthesis, direct bonding to the semiconductor substrates, etc. This strategy might extend the approach of synthesizing desirable nanostructures of other important low-melting metal oxides for potential applications.     

水热合成氧化铁纳米结构及机理分析

利用硝酸铁与油酸钠反应所得的化合物在高温水热条件下分解制备多种氧化铁纳米结构.研究了水热反应温度、反应时间和热处理工艺对于产物结构的影响,并且探讨了产生各种纳米结构的机理.在高温较短反应时间下,可以制得直径为15nm,长度为3μm的纳米线结构,延长反应时间至25h,得到边长为15nm的氧化铁四方颗粒.将含有羟基氧化铁相的氧化铁纳米线在不同温度下进行热处理,得到了直径为15nm,长度为1μm的氧化铁纳米线和直径为1～3μm的氧化铁微米球.     

Proline-derived in situ synthesis of nitrogen-doped porous carbon nanosheets with encaged Fe2O3@Fe3C nanoparticles for lithium-ion battery anodes

The homogeneous incorporation of heteroatoms into two-dimensional C nanostructures, which leads to an increased chemical reactivity and electrical conductivity as well as enhanced synergistic catalysis as a conductive matrix to disperse and encapsulate active nanocatalysts, is highly attractive and quite challenging. In this study, by using the natural and cheap hydrotropic amino acid proline—which has remarkably high solubility in water and a desirable N content of ~12.2 wt.%—as a C precursor pyrolyzed in the presence of a cubic KCl template, we developed a facile protocol for the large-scale production of N-doped C nanosheets with a hierarchically porous structure in a homogeneous dispersion. With concomitantly encapsulated and evenly spread Fe₂O₃ nanoparticles surrounded by two protective ultrathin layers of inner Fe₃C and outer onion-like C, the resulting N-doped graphitic C nanosheet hybrids (Fe₂O₃@Fe₃C-NGCNs) exhibited a very high Li-storage capacity and excellent rate capability with a reliable and prolonged cycle life. A reversible capacity as high as 857 mAh•g^–1 at a current density of 100 mA•g^–1 was observed even after 100 cycles. The capacity retention at a current density 10 times higher—1,000 mA•g^–1—reached 680 mAh•g^–1, which is 79% of that at 100 mA•g^–1, indicating that the hybrids are promising as anodes for advanced Li-ion batteries. The results highlight the importance of the heteroatomic dopant modification of the NGCNs host with tailored electronic and crystalline structures for competitive Li-storage features.

     

Simple synthesis of urchin-like In2S3 and In2O3 nanostructures

Without the assistance of any surfactant and template, urchin-like In₂S₃ microspheres constructed with nanoflakes of about 15–30 nm thickness were synthesized via the hydrothermal reaction of indium trichloride and thioacetamide in 6.25 vol.% acetic acid aqueous solution at 80 °C for 6–24 h. The as-synthesized nanostructured In₂S₃ could be completely transformed into In₂O₃ when subjected to heating in air at 600 °C for 5 h. The resultant In₂O₃ consisted of urchin-like microsphere built up by 20–30 nm thickness nanoflakes and 20–40 nm nanoparticles. X-ray diffraction, field emission scanning electronic microscope and energy dispersive X-ray spectroscopy have been used to characterize the In₂S₃ and In₂O₃ nanostructures obtained.     

Non-aqueous synthesis of water-dispersible Fe3O4-Ca3(PO4)2 core-shell nanoparticles

The Fe(3)O(4)-Ca(3)(PO(4))(2) core-shell nanoparticles were prepared by one-pot non-aqueous nanoemulsion with the assistance of a biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO), integrating the magnetic properties of Fe(3)O(4) and the bioactive functions of Ca(3)(PO(4))(2) into single entities. The Fe(3)O(4) nanoparticles were pre-formed first by thermal reduction of Fe(acac)(3) and then the Ca(3)(PO(4))(2) layer was coated by simultaneous deposition of Ca(2+) and PO(4)(3-). The characterization shows that the combination of the two materials into a core-shell nanostructure retains the magnetic properties and the Ca(3)(PO(4))(2) shell forms an hcp phase (a = 7.490 ?, c = 9.534 ?) on the Fe(3)O(4) surface. The magnetic hysteresis curves of the nanoparticles were further elucidated by the Langevin equation, giving an estimation of the effective magnetic dimension of the nanoparticles and reflecting the enhanced susceptibility response as a result of the surface covering. Fourier transform infrared (FTIR) analysis provides the characteristic vibrations of Ca(3)(PO(4))(2) and the presence of the polymer surfactant on the nanoparticle surface. Moreover, the nanoparticles could be directly transferred to water and the aqueous dispersion-collection process of the nanoparticles was demonstrated for application readiness of such core-shell nanostructures in an aqueous medium. Thus, the construction of Fe(3)O(4) and Ca(3)(PO(4))(2) in the core-shell nanostructure has conspicuously led to enhanced performance and multi-functionalities, offering various possible applications of the nanoparticles.     

SiO2包覆Fe2O3纳米粒子的制备和性能

在近球形α-Fe2O3颗粒的悬浮液中,以正硅酸乙酯(TEOS)为硅源,氨水和尿素为催化剂,合成了Fe2O3-SiO2核-壳粒子.应用TEM.XRD对Fe2O3-SiO2核-壳粒子结构进行了测定.研究了TEOS.氨水的浓度对核-壳粒子结构的影响.UV-Vis吸收光谱表明,SiO2壳层消除了Fe2O3纳米粒子的表面悬挂键,产生增强的激子发射,使得核-壳粒子的吸收峰发生蓝移.根据带边吸收峰的波长计算出核-壳粒子中Fe2O3的禁带宽度为2.25 eV.     

Synthesis of Fe(2)O(3)/TiO(2) nanorod-nanotube arrays by filling TiO(2) nanotubes with Fe

Synthesis of hematite (α-Fe(2)O(3)) nanostructures on a titania (TiO(2)) nanotubular template is carried out using a pulsed electrodeposition technique. The TiO(2) nanotubes are prepared by the sonoelectrochemical anodization method and are filled with iron (Fe) by pulsed electrodeposition. The Fe/TiO(2) composite is then annealed in an O(2) atmosphere to convert it to Fe(2)O(3)/TiO(2) nanorod-nanotube arrays. The length of the Fe(2)O(3) inside the TiO(2) nanotubes can be tuned from 50 to 550?nm by changing the deposition time. The composite material is characterized by scanning electron microscopy, transmission electron microscopy and diffuse reflectance ultraviolet-visible studies to confirm the formation of one-dimensional Fe(2)O(3)/TiO(2) nanorod-nanotube arrays. The present approach can be used for designing variable one-dimensional metal oxide heterostructures.     

Synthesis and characterisation of In(OH)3 and In2O3 nanoparticles by sol-gel and solvothermal methods

Indium hydroxide nanostructures were synthesised by sol-gel and hydrothermal processes from indium acetate and sodium hydroxide as precursors and polyvinyl alcohol, polyvinyl pyrrolidone or polydimethylsiloxane as stabilisers. Calcination of the In(OH)₃ nanostructures at 500°C in air yielded In₂O₃ nanoparticles. The morphology, crystallinity and thermal behaviour of the obtained products of each method were investigated by X-ray diffraction, scanning electron microscopy and thermal gravimetry analysis and differential thermal analysis.     

Facile synthesis of capped γ-Fe2O3 and Fe3O4 nanoparticles

Facile methods for the selective preparation of capped iron oxide nanoparticles (γ-Fe₂O₃, Fe₃O₄) are described. The magnetic oxides are obtained via oxidative transformation of an iron hydroxide gel using H₂O₂ or (NH₄)₂S₂O₈ solutions as oxidants. Capping with oleic or other aliphatic acids is established simultaneously in one step by adding a toluene solution of the capping agent and refluxing the resulting biphase system. The method is simple, soft and affords nanoparticles of γ-Fe₂O₃ or Fe₃O₄ of controlled size depending on the reaction conditions. The capped nanoparticles are readily soluble in organic or aqueous media according to the nature of the sheath surrounding the surface of the particles, providing stable and high concentration ferrofluids.     

In situ grown Fe3O4 particle on stainless steel:A highly efficient electrocatalyst for nitrate reduction to ammonia

NH3 is an essential feedstock for fertilizer synthesis.Industry-scale NH3 synthesis mostly relies on the Haber-Bosch method,however,which suffers from massive C...     

Multi-walled carbon nanotubes-supported Fe(naph)3 nanoparticles to prepare polyacetylene/multi-walled carbon nanotubes nanocomposites

Carbon nanotubes (CNTs) are a promising candidate for preparing conductive polymer/CNT nanocomposites. CNTs are also an alternative to conventional catalyst support. This report studies multi-walled carbon nanotubes (MWNTs) supported-Fe(naph)₃ nanoparticles to prepare polyacetylene (PA)/MWNT nanocomposites with core–shell structure. The XPS spectra and HRTEM images demonstrate the Fe(naph)₃ nanoparticles successfully deposited on the walls of MWNTs and partially transformed to γ-Fe₂O₃ nanoparticles after heated at 100 °C for 2 h. XRD analysis indicates the formation of PA on the walls of MWNTs. Structural analysis using HRTEM shows that PA/MWNT nanocomposites exhibit core–shell structure. TGA data reveals the stability of PA grown on the exterior walls of MWNTs has been improved. The growth mechanism of PA/MWNT nanocomposites can be explained by a heterogeneous process. The conductivity of the nanocomposites was studied by a four-probe approach and a relatively high conductivity was observed.     

Bonding MnO2/Fe3O4 shell-core nanostructures to catalyze H2O2 degrading organic dyes

Shell-core nanostructures with both high catalytic activation and recyclability have been becoming hot property in nano-catalysis. By respectively using co-precipitation method, sol-gel method, and homogeneous precipitation method we manufactured shell-core nano-particles of Fe3O4 core and MnO2 shell. The Bonding mechanism of the composite is discussed in detail, and the efficiency and nature of the particles to degrade methyl orange by catalyzing H2O2 is also demonstrated. We show that by using homogeneous precipitation method one can obtain morphologically uniform nano-particles of about 5-6 nm MnO2 shell and 13-14 nm Fe3O4 core. The characteristic peak of Fe3O4 in the Infrared spectra of the composite particles was blue shifted, and a novel peak appears at 775.68 cm(-1) referring to occurrence of new bond. X-ray Photoelectron Spectroscopy analysis showed that the bonding energy of Fe2p and Ols was increased due to the combination of the MnO2 shell and the Fe3O4 core, suggesting a new bond of Fe-O-Mn occurred in the composite. The MnO2 shell has abundant hydroxyl radicals and exhibits high chemical activity in catalyzing H2O2 and degrading methyl orange with a degree of greater than 95%. On the other hand, the shell-core nanostructures are super-paramagnetic, and the saturated magnetization reaches 33.5 eum/g, which is sufficient for the catalyst to be recycled.     

Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

The assembly of superparamagnetic Fe₃O₄ nanoparticles on submicroscopic SiO₂ spheres have been prepared by an in situ reaction using different molar ratios of Fe³⁺/Fe²⁺ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO₂ as core and Fe₃O₄ nanoparticles as shell depend on the molar ratio of Fe³⁺/Fe²⁺.     

Synthesis of magnetite (Fe3O4) nanoparticles without surfactants at room temperature

Iron oxide nanoparticles in the interval of 4–43 nm were synthesized by a colloidal method at room temperature, without use of surfactants and using precursors like FeCl₃·6H₂O and FeCl₂·4H₂O; deionizated water free of dissolved oxygen and ammonia solution (29% vol.) and using several aging times (2, 5 and 10 min). A detailed study by X- ray diffraction (XRD), Conventional Transmission Electron Microscopy (CTEM), High-Resolution Transmission Electron Microscopy (HRTEM) and electron diffraction patterns showed that with a reaction time less than 5 min nanoparticles of magnetite phase (Fe₃O₄) were synthesized, and with a bigger time of reaction the lepidocrocite phase (FeO(OH)) was identified. The minor particle average size measured was 6 nm in the sample, 0.0125 M with 2 min of aging time (0.0125M2 m). In addition it was possible to obtain a narrow nanoparticle size dispersion from 4 to 10 nm for small aging times.