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In this work, BiTiO/BiTiO composite photocatalysts composed of BiTiO sub-micron-sized particles and BiTiO nanosheets with exposed {001} facets, were synthesized by a one-step molten salt method. The contents of BiTiO in the BiTiO/BiTiO composites were adjusted by the Bi/Ti molar ratio of raw materials. The structure, morphology and optical absorption properties were characterized by XRD, SEM, TEM, HRTEM and UV-Vis diffuse reflectance. Compared with pure BiTiO, the as-prepared BiTiO/BiTiO composite (for the Bi/Ti ratio ~4:3.2) exhibit more excellent photocatalytic activities in the degradation of methyl orange (MO), Rhodamine B (RhB) and mixed dyes (RhB and MO) in aqueous solutions under simulated solar light irradiation. Furthermore, for the mixed dye solution, the as-prepared composite photocatalysts show preferential decomposition of MO in comparison to RhB. To detect the reactive species, the scavenger tests for the composite photocatalysts were carried out and the results indicate that the photogenerated h would play an important role in the degradation of RhB and MO dyes. Based on the experimental results in this work, the possible photocatalytic degradation mechanism of BiTiO/BiTiO composites was also discussed. [ABSTRACT FROM AUTHOR]

Submicron BiFeO powders were successfully synthesized via a simple hydrothermal process with the assistance of mineralizer (NaOH) at 150-190°C, using FeCl and Bi(NO)⋅5HO as reactants. The effects of mineralizer concentration, reaction temperature and time on the phase evolution and crystal morphology of the resulting samples were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry and differential scanning calorimetry (TG-DSC), and vibrating sample magnetometry (VSM) were used to characterize the as-synthesized samples. The experimental results revealed that a pure BiFeO phase could be formed at a temperature ranging from 170 to 190°C for 4-20 h in the presence of 0.03-0.12 M NaOH. It was found that the mineralizer concentration, reaction temperature and time played a key role in controlling the growing speed of nuclei and formation of BiFeO crystallites. The possible formation mechanisms of submicron BiFeO powders with different morphologies were presented. The magnetization of BiFeO powders showed a weak ferromagnetic behavior at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: CoFe2−x Gd x O4 (x=0–0.25) nanoparticles were synthesized via a simple hydrothermal process at 200°C for 16h without the assistance of surfactant. The as-synthesized powders were characterized by X-ray diffraction, transmission electron microscopy, and a vibrating sample magnetometer. The X-ray diffraction results showed that the as-synthesized powders were in the pure phase with a doping amount of ≤0.25, and the peaks could be readily indexed to the cubic spinel cobalt ferrite. Transmission electron microscopy and high resolution transmission electron microscopy observations revealed that the gadolinium-doped cobalt ferrite nanoparticles were single crystal, roughly spherical, uniformly distributed, and not highly agglomerated. The room temperature magnetic field versus magnetization measurements confirmed a strong influence of gadolinium doping on the saturation magnetization and coercivity due to large lattice distortion and grain growth of small particles. [ABSTRACT FROM AUTHOR]

Abstract: SnS2 microspheres composed of submicron-sized flakes were successfully prepared via a simple surfactant-free hydrothermal reaction route at 240°C for 12h, using SnCl4 and Na2S as reactants. The powders were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The X-ray diffraction pattern confirmed that the SnS2 microspheres had a single-phase hexagonal structure. The SEM micrographs indicated that these microspheres with the size of ∼30μm in diameter were mainly constructed by self-assembly of submicron-sized SnS2 flakes. The effect of reaction temperature and the amount of mineralizer (urea) on the formation of SnS2 microspheres under hydrothermal conditions were investigated and a possible formation mechanism was preliminarily presented. [Copyright &y& Elsevier]

In this work, three-dimensional Bi 5 O 7 I microstructures were successfully fabricated by a thermal conversion of BiOI microspheres in air at temperatures ranging from 450 to 525 °C. The phase structure, morphology, and optical property of the Bi 5 O 7 I powders were characterized with respect to that of parent BiOI by XRD, SEM, XPS, TEM, and UV–vis spectroscopy, respectively. The results revealed that porous BiOI microspheres were completely transformed to porous Bi 5 O 7 I microstructures at 450 °C. The surface morphology of BiOI microspheres was gradually changed from ultrathin nanosheets to large 3D crystals of Bi 5 O 7 I by increasing the heat treatment temperature. The photocatalytic activity of the Bi 5 O 7 I powders fabricated at different heat treatment temperatures was investigated by the degradation of Rhodamine B in aqueous solution. Among the samples, the sample heat treated at 450 °C showed the highest photocatalytic activity due to its high crystalline, high surface area and porous microstructures. [ABSTRACT FROM AUTHOR]

Abstract: Submicron- and micron-sized lead iodide (PbI2) particles with well-controlled morphologies were successfully fabricated via a low-temperature hydrothermal process assisted by dodecyltrimethylammonium bromide (DTAB) as cationic surfactant. The as-synthesized powders were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–vis spectroscopy. The effects of synthesis parameters (temperature, time, pH, and surfactant amount) were systematically investigated. The obtained results showed that the submicron structure was belt-like at 100–120°C, transformed to rod-like by increasing temperature to 140°C and it became a microtube-like at 160–200°C. By changing the pH of the synthesizing solution, it was found that a pure PbI2 phase could be obtained below 7. With the addition of increasing amount of surfactant, microparticles were converted to microrods→submicron belts→microtubes. The time-dependent experimental results revealed that the dissolution–recrystallization and dissolution–recrystallization–self-oriented-attachment were considered to be the possible mechanisms for the formation of the belt- and tube-like PbI2 submicron- and micron-sized particles, respectively. The optical properties of the PbI2 particles synthesized at 100–200°C for 8h under hydrothermal conditions were also studied. [Copyright &y& Elsevier]

Abstract: YVO4:Eu3+ powders with different morphologies were fabricated by a simple hydrothermal method at 180°C for 24h in a wide pH range with the assistance of polyvinylpyrrolidone (PVP) as a nonionic surfactant. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The obtained results showed that the pH value of synthesis solution played a key role in the formation of final products with different morphologies, such as, microspheres, irregular microspheres with grain-like nanoparticles, stone-like structures with regular short nanorods, and smooth rhombohedrons. The PL measurements revealed that the emission intensity of the samples was first decreased, and then increased with increasing the pH value due mainly to the increase in crystallinity and decrease in surface defects. [Copyright &y& Elsevier]

Abstract: Nano- and micro-scaled Eu-doped yttrium orthovanadate (YVO4:Eu3+) powders had been fabricated via disodium ethylenediamine tetraacetate (Na2EDTA)-assisted morphology controllable hydrothermal method in a wide pH range at 180°C for 24h. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The results showed that the pH value of the synthesis solution played a key role in the formation of the final products with different morphologies, including ball-like micro-spheres, micro-spheres composed of submicron cubes and flower-like structures containing nano-plates. The photoluminescence measurement revealed that the luminescent properties of the samples were changed by varying their morphologies. The significant ball-like micro-spheres of YVO4:Eu3+ particles had been synthesized, and the luminescence intensity of them is the strongest one among all products. [Copyright &y& Elsevier]