低维Bi2Fe4O9晶体的控制生长及其光催化性能研究

Low-dimensional Bi₂Fe₄O₉ nanosheets and microrods have been selectively prepared by a solvothermal method, from which the growth of the Bi₂Fe₄O₉ crystals can be controlled by the variation of reaction conditions. Structure determination showed that the nanosheets are mainly exposed by {001} facets while the microrods are exposed by {110} facets. Ab- sorption spectra revealed that there are two bandgaps observed for both nanosheets (at 1.9 and 1.55 eV) and microrods (1.7 and 1.45 eV), and they both would be available for the sunlight photocatalysis e ciently due to the intensive absorption ability in a wide region. Photocatalytic investigation demonstrated that the overall photocatalytic performance of the microrods is prior to that of the nanosheets due to the variation of bandgaps and exposed facets. The present report provides a useful alternative strategy for the controlling growth of nanostructures and/or microcrystals besides the present demonstration of the Bi₂Fe₄O₉ crystals with diflerent bandgaps and facets that would be able to tune the corresponding photocatalytic ability selectively.     

Flowerlike PtCl4/Bi2WO6 composite photocatalyst with enhanced visible-light-induced photocatalytic activity

Flowerlike PtCl₄/Bi₂WO₆ composite photocatalyst was successfully synthesized through a simple two-step method involving a template-free hydrothermal process and the following impregnation treatment. The samples were fully characterized by the study of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis absorption spectra. The results indicated that the doping of Pt species did not affect the crystal structure and the morphology of Bi₂WO₆ photocatalyst, but it had great influences on the photocatalytic activity of Bi₂WO₆ towards rhodamine-B (RhB) degradation. Besides, the Pt species was found to be present as PtCl₄ in the composite samples, and also an optimal Pt species content on the surface of Bi₂WO₆ photocatalyst was discovered with the highest photocatalytic ability. The improved photocatalytic performance could be ascribed to the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs. Meanwhile, a possible mechanism for RhB photocatalytic degradation over PtCl₄/Bi₂WO₆ catalyst was also proposed.     

Preparation, electronic structure, and photocatalytic properties of Bi2O2CO3 nanosheet

Bi₂O₂CO₃ nanosheet with a thickness of less than 20 nm was synthesized via hydrothermal and solvothermal process. The properties of the as-prepared nanosheet were characterized by X-ray diffraction, scanning electron microscopy, and diffuse reflectance spectra. The electronic structure was investigated using first-principle calculations. Application of the as-prepared Bi₂O₂CO₃ nanosheet in photocatalysis was also studied.     

Novel nanostructures of β-Ga2O3 synthesized by thermal evaporation

In this study, we report the novel β-Ga₂O₃ nanostructures synthesized by the thermal evaporation of Ga droplet in the presence of Au catalysts at 900 °C. The morphology and structure of the products were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The single-crystalline β-Ga₂O₃ nanosheets have lateral dimensions up to several tens of microns. Large arrays of column-like layered crystal β-Ga₂O₃ structures that consisted of many nanosheets were formed on the Au-coated silicon substrate under the suitable vapor concentration. These novel β-Ga₂O₃ nanostructures are expected to have potential application in functional nanodevices.     

Synthesis and performance of core-shell structured ZnO/In2O3 composites in situ growth

Core-shell structured ZnO/In₂O₃ composites were successfully synthesized via situ growth method. Phase structure, morphology, microstructure and property of the products were investigated by X-ray diffraction (XRD), TG-DTA, field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), transmission electron microscope (TEM) and photoluminescence (PL). Results show that the core-shell structures consist of spindle-like ZnO with about 800 nm in length and 200 nm in diameter, and In₂O₃ particles with a diameter of 50 nm coated on the surface of ZnO uniformly. HMTA plays an important role in the formation of core-shell structures and the addition of In₂O₃ has a great effect on PL spectrum. Possible mechanism for the formation of core-shell structures is also proposed in this paper.     

Fabrication and characterization of Bi2Te3 nanoplates via a simple solvothermal process

Bi₂Te₃ nanoplates have been successfully obtained by a novel solvothermal method in the presence of hexadecyltrimethylammonium bromide (CTAB). Various techniques such as X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), and Fourier transform infrared spectrometry (FT-IR) have been used to characterize the obtained products. The results show that the as-synthesized samples are rhombohedral-structured Bi₂Te₃ single-crystal nanoplates about 70–200 nm in diagonal and 30 nm in thickness, and the growth direction is perpendicular to c-axis. The existence of CTAB is vital to the formation of the plate-like morphology. In addition, the reaction solvents also have important influence on the shape-control of final products.     

Low-temperature growth and properties of flower-shaped - Ni(OH)2 and NiO structures composed of thin nanosheets networks

Flower-shaped β- Ni(OH)₂ structures composed of thin nanosheet networks have been synthesized via the simple aqueous solution route by using nickel chloride and ammonium hydroxide at 65 C in 4 h. The general morphological observations revealed that the flowers are composed of thin nanosheets which were connected to each other in such a manner that they form network-like morphologies. Moreover, single-crystalline flower-shaped NiO structures composed of thin nanosheets were also obtained by thermal decomposition of flower-shaped β- Ni(OH)₂ structures. The shape of nanosheet networks in β- Ni(OH)₂ was sustained after thermal decomposition to NiO however, some broken nanosheets were also observed from the flower-shaped structures of NiO. The as-prepared products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA).     

Preparation of Bi2S3 thin films with a nanoleaf structure by electrodeposition method

Nanoleaf-like Bi₂S₃ thin films were deposited on indium tin oxide (ITO) glass using Bi(NO₃)₃ and Na₂S₂O₃ as precursors by a cathodic electrodeposition process. The as-deposited thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and photoluminescence spectrum (PL). The influence of precursor solution mole concentration ratios [Bi(NO₃)₃]/[Na₂S₂O₃] on the phase compositions, morphologies and photoluminescence properties of the obtained thin films were investigated. Results show that a uniform Bi₂S₃ thin film with nanoleaf structure can be obtained with the precursor solution concentration ratio [Bi(NO₃)₃]/[Na₂S₂O₃] = 1:7. The as-prepared thin films exhibit blue-green photoluminescence properties under ultraviolet light excitation. With the increase of concentration ratios [Bi(NO₃)₃]/[Na₂S₂O₃] in the deposition solution, the crystallizations and PL properties of Bi₂S₃ thin films are obviously improved.     

Influences of Bi2O3 on microstructure and magnetic properties of MnZn ferrite

MnZn ferrites were prepared by conventional oxide ceramic process. The effects of Bi₂O₃ on microstructure and magnetic properties of MnZn ferrites were investigated by means of characterizing the fracture surface micrograph, composition of grain boundary, magnetic properties and density by scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDS), B-H analyzer and Archimedes method, respectively. The results indicate that Bi₂O₃ mainly segregates and concentrates in the grain boundary regions, promotes solid-state reaction and grain growth, reduces porosity and enhances density. Optimum addition of Bi₂O₃ increases the permeability and saturation magnetic induction, meanwhile ensures the well frequency stability of permeability.     

Template-free synthesis of ZnV2O4 hollow spheres and their application for organic dye removal

Hollow ZnV₂O₄ spheres with the shell aggregated by small nanoparticles were successfully synthesized through a facile one-pot template-free solvothermal method. The as-prepared product was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller N₂ adsorption-desorption analyses. The formation of ZnV₂O₄ hollow spheres was based on flowerlike intermediate products supported reduction-dissolution-aggregation process at the expense of consumption of all the flowerlike products. The obtained ZnV₂O₄ hollow spheres showed a good adsorption capacity of methylene blue (MB) organic dye, which might be attributed to their special structural feature with large surface area. The adsorption kinetics and isotherm of MB on ZnV₂O₄ hollow spheres were also studied.     

Fabrication of chain-like Mn2O3 nanostructures via thermal decomposition of manganese phthalate coordination polymers

A novel manganese coordination polymer [Mn(Pht)(H₂O)]_n as a precursor was obtained by chemical precipitation involving an aqueous solution of anhydrous manganese acetate and phthalate anion as a potential O-banded ligand. Fourier transform infrared (FT-IR) results proved that phthalate anions coordinate to metal cations as a chelating bidentate ligand, making polymeric structure. The Mn₂O₃ nanostructures have been prepared via thermal decomposition of as-prepared manganese phthalate polymers as precursor in the presence of oleic acid (OA) and triphenylphosphine (TPP) as a stabilizer and capping. Different approaches such as FT-IR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to characterize the products. TEM images and XRD analysis indicated that the as-synthesized chain-like Mn₂O₃ has a crystal phase of cubic syngony with a mean size of ∼40 nm.     

Effect of calcination temperature on the structure and hydroxylation activity of Ni0.5Cu0.5Fe2O4 nanoparticles

Nanocrystalline Ni_0.5Cu_0.5Fe₂O₄ was synthesized by sol-gel method with varying calcination temperature over the range of 500-1000. The powders obtained were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, thermal analysis (TG-DTG-DTA) of the precursor was carried out. The study reveals the simultaneous decomposition and ferritization process at rather low temperature (280-350). For the crystalline structure investigated, single cubic spinel is gained when the precursor was decomposed at 800-1000, whereas separated crystal CuO formed when calcination temperature is below 800. The increase of calcination temperature favors the appearance of Fe_B³⁺, Cu_A²⁺ and O on the spinel surface. The hydroxylation activity is relative to the amount of Cu_B²⁺ species on the spinel surface. The lattice oxygen species on the spinel surface are favorable for the deep oxidation of phenol.     

Formation of highly textured (1 1 1) Bi2O3 films by anodization of electrodeposited bismuth films

Highly textured bismuth oxide (Bi₂O₃) thin films have been prepared using anodic oxidation of electrodeposited bismuth films onto stainless steel substrates. The Bi₂O₃ films were uniform and adherent to substrate. The Bi₂O₃ films were characterized for their structural and electrical properties by means of X-ray diffraction (XRD), electrical resistivity and dielectric measurement techniques. The X-ray diffraction pattern showed that Bi₂O₃ films are highly textured along (1 1 1) plane. The room temperature electrical resistivity of the Bi₂O₃ films was 10⁵ Ω cm. Dielectric measurement revealed normal oxide behavior with frequency.     

Photoelectrocatalytic degradation of organic contaminants at Bi2O3/TiO2 nanotube array electrode

In the current work, TiO₂ nanotube array was prepared via electrochemical anode method. Then the Bi₂O₃ nanoparticles were deposited onto the TiO₂ nanotube array via dip-coating method from an amorphous complex precursor. The crystal structures were characterized via X-ray diffraction analysis. Their surface textures were observed via electron-scanning microscope. The prepared composite array electrode exhibited high photoelectrocatalytic activities towards degrading organic contaminants under visible light irradiation. High photoelectrocatalytic activities were also exhibited under UV light irradiation. The catalytic mechanism was discussed based on the analysis of electrochemical and degradation kinetics results. It is suggested a P (Bi₂O₃)-N (TiO₂) junction was formed to increase the catalytic activates. The stability of the electrode materials was confirmed finally.     

SrBi2Ta2O9/Bi4Ti3O12复合铁电薄膜的制备与特性研究

采用溶胶凝胶工艺在p-Si衬底上制备了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合铁电薄膜. 研究了SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂复合薄膜的微观结构与生长行为、铁电性能和疲劳特性. 研究表明: Si衬底Bi₄Ti< 关键词： 2Ta₂O₉')" href="#">SrBi₂Ta₂O₉ 4Ti₃O₁₂')" href="#">Bi₄Ti₃O₁₂ 复合铁电薄膜 溶胶凝胶工艺     

Hierarchical ZnO/Bi2O3 nanostructures: synthesis, characterization, and electron-beam modification

Two types of ZnO/Bi₂O₃ nanonecklace heterostructures were fabricated using the vapor-phase transport (VPT) method for the first time. These hierarchical structures were well characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) attached. The growth mechanism of the novel structures were proposed based on these characterizations. Electron-beam irradiation was found to be a powerful and controllable tool in further tailoring such ZnO/Bi₂O₃ nanonecklace heterostructures. In addition, photoluminescence (PL) emission from the hierarchical nanostructures showed enhancement comparing to the pure Bi₂O₃ powder.     

Bi2Ti2O7/Si薄膜的制备及C-V特性研究

采用化学溶液分解法(CSD)在Si衬底上制备了Bi₂Ti₂O₇薄膜.X射线双晶衍射和原子力显微镜检测表明,所制备的薄膜主要为Bi₂Ti₂O₇相的多晶材料.同时还研究了AuBi₂Ti₂O₇/n-Si(100)结构的电容电压(C-V)特性,结果表明,在Bi₂Ti₂O关键词： C-V特性 2Ti₂O₇薄膜')" href="#">Bi₂Ti₂O₇薄膜 电荷迁移     

Catalytic performance of Mn3O4 and Co3O4 nanocrystals prepared by sonochemical method in epoxidation of styrene and cyclooctene

A simple sonochemical method was developed to synthesis uniform sphere-like Co₃O₄ and Mn₃O₄ nanocrystals. Epoxidation of styrene and cyclooctene by anhydrous tert-butyl hydroperoxide over the prepared Co₃O₄ and Mn₃O₄ nanocatalysts was investigated. The results of conversion activity were compared with bulk Co₃O₄ and Mn₃O₄. Under optimized reaction conditions, the nanocatalysts showed a superior catalytic performance as compared to the bulk catalysts. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area, were used to characterize and investigate the nanocatalysts.     

Growth of β-Ga2O3 nanorods by ammoniating Ga2O3/V thin films on Si substrate

This paper reports that/3-Ga2O3 nanorods have been synthesized by ammoniating Ga2O3 films on a V middle layer deposited on Si（111） substrates. The synthesized nanorods were confirmed as monoclinic Ga2O3 by x-ray diffraction,Fourier transform infrared spectra. Scanning electron microscopy and transmission electron microscopy reveal that the grown β-Ga2O3 nanorods have a smooth and clean surface with diameters ranging from 100 nm to 200 nm and lengths typically up to 2μm. High resolution TEM and selected-area electron diffraction shows that the nanorods are pure monoclinic Ga2O3 single crystal. The photoluminescence spectrum indicates that the Ga2O3 nanorods have a good emission property. The growth mechanism is discussed briefly.     

A novel chemical synthesis and characterization of Mn3O4 thin films for supercapacitor application

Mn₃O₄ thin films have been prepared by novel chemical successive ionic layer adsorption and reaction (SILAR) method. Further these films were characterized for their structural, morphological and optical properties by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), field emission scanning electron microscopy (FESEM), wettability test and optical absorption studies. The XRD pattern showed that the Mn₃O₄ films exhibit tetragonal hausmannite structure. Formation of manganese oxide compound was confirmed from FTIR studies. The optical absorption showed existence of direct optical band gap of energy 2.30 eV. Mn₃O₄ film surface showed hydrophilic nature with water contact angle of 55°. The supercapacitive properties of Mn₃O₄ thin film investigated in 1 M Na₂SO₄ electrolyte showed maximum supercapacitance of 314 F g⁻¹ at scan rate 5 mV s⁻¹.