Study on morphologies of Co microcrystals produced by solvothermal method with different solvents

Cobalt microcrystals with different sizes and morphologies were fabricated via a facile solvothermal method. The effects of different solvents on the sizes and morphologies are investigated separately. Flowerlike cobalt with around tens of microns in diameter is obtained in ethanol. Meanwhile, of microdisks and octadecahedra with the edge lengths about several microns are fabricated in ethylene glycol and glycerol, respectively. Reduction potential and viscosity rank of the solvents play the important roles in controlling the sizes and morphologies of cobalt. Moreover, room-temperature magnetic measurement shows that the magnetic properties of cobalt microcrystals depend on their morphologies.     

Morphology-controlled synthesis of silver nanostructures via a solvothermal method

Silver nanostructures have been synthesized by a simple solvothermal method in the presence of poly(vinylpyrrolidone) (PVP). Typically, different exotic agents (NaOH, KBr, NaCl) are added into the reaction system. The anions (OH⁻, Cl⁻, Br⁻) from these agents can combine Ag⁺ to form silver salt colloids (AgOH, AgBr and AgCl), decreasing the concentration of free Ag⁺ in the initial formation of silver seeds. However, different release rates of Ag⁺ from these colloids to the solution in the subsequent reaction may play different roles in the growth of silver seeds. The as-prepared silver nanostructures were characterized by UV–vis absorption spectrum, X-ray diffraction (XRD) and field emission scanning electron microscope (FSEM). It is found that silver nanostructures with various shapes can be obtained by the addition of different exotic agents. Finally, our work provides a simple route to synthesize silver nanostructures with controllable morphologies.     

Fabrication of ZnS/ZnO hierarchical nanostructures by two-step vapor phase method

A simple two-step vapor phase method is presented to fabricate ZnS/ZnO hierarchical nanostructures in bulk quantities. That is ZnS nanobelts were first synthesized and then used as substrate for growth of ZnO nanorod arrays. Investigation results demonstrate that the polar surfaces of ZnS nanobelts could induce a preferred asymmetric growth of ZnO nanorods on the side surfaces. But it is believed that if the local concentration of ZnO was high enough, ZnO nanorods could also grow symmetrically on the top/bottom surface of the ZnS nanobelts. The optical property of the products was also recorded by means of photoluminescence (PL) spectroscopy.     

Characterization of copper sulfide nanostructured spheres and nanotubes synthesized by microwave-assisted solvothermal method

Copper sulfide nanostructured spheres and nanotubes were successfully synthesized, using a microwave-assisted solvothermal method, by the decomposition of [Cu(CH₃CSNH₂)₂]Cl₂ complexes, formed by the reaction of CuCl₂·2H₂O and CH₃CSNH₂ in ethylene glycol at different pH values, and identified by CHNS/O and FTIR analyses. The decrease in bonding energy of N-H revealed the coordination of copper ions and thioacetamide molecules. It was specified that nitrogen atoms of thioacetamide molecules were used to form Cu-thioacetamide complexes. XRD, SEM, TEM and SAED analyses show that the products were hexagonal CuS spheres in an extremely low pH solution, and hexagonal CuS nanotubes at a pH 13. Their Raman spectra show sharp peaks at 473 cm^− 1, identified as the S-S stretching mode of S₂ ions at the 4e sites.     

Microemulsion-mediated solvothermal synthesis of ZnS nanowires

Uniform and high-aspect-ratio ZnS nanowires with length up to several micrometers and diameter of 30–50 nm are synthesized by a facile and low-cost microemulsion-mediated solvothermal method. Moreover, ZnS nanorods and bamboo-leaf-like ZnS nanostructures were also obtained by modulating the reaction parameters. Especially, hollow bamboo-leaf-like ZnS nanostructures formed by radiating those bamboo leaves with electron beam. A reasonable mechanism to the formation of the as-prepared one-dimension zinc blend ZnS nanocrystals is also discussed.     

Ferromagnetic CrTe nanostructures with high coercivity synthesized by chemical solution method

正Nanoscale magnetic materials have been extensively investigated due to both their unique properties and great potential for many important technological applications,including spin-based electronics,recording media,permanent magnets and magneto-caloric refrigeration.Recently nanoparticles of transition metal chalcogenides such as Fe3Se4 have     

One-dimensional cadmium sulfide (CdS) nanostructures by the solvothermal process: Controlling crystal structure and morphology aided by different solvents

Cadmium sulfide (CdS) nanowires and nanorods with different aspect ratios were successfully synthesized by the solvothermal method aided with various solvents, namely ethylenediamine, ethanolamine and triethylene tetraamine. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that, highly pure CdS nanostructures were crystallized with different structures and preferable growth orientations depending on solvent nature. Field emission electron microscope (FE-SEM) images showed that the aspect ratio of CdS nanostructures depends upon the dielectric constant and boiling temperature of solvents. CdS nanostructures with the highest aspect ratio in the form of nanowire were obtained using ethylenediamine, whereas CdS nanorods were produced in the presence of ethanolamine and triethylene tetraamine solvents. The absorption edge of CdS nanowires and nanorods showed a blue shift compared with that of bulk CdS due to an increase in their band gap energies.     

MgO nanostructures synthesized by thermal evaporation

MgO nanostructures with various morphologies were fabricated by thermal evaporation through controlling the growth temperature and gas flow, including MgO polyhedral shells, nanotubes, cubes and nanowires. MgO polyhedral shells and nanotubes were fabricated when H₂ was introduced to the system in the beginning of the thermal process, MgO cubes and nanowires were fabricated when Ar/O₂ was introduced. MgO polyhedral shells and MgO cubes were collected in the lower temperature zone, while MgO nanotubes and nanowires were collected in the relative higher temperature zone. The growth mechanism was proposed based on the crystal structure and analysis of growth conditions.     

Investigation of ZnO nanorods synthesized by a solvothermal method, using Al-doped ZnO seed films

ZnO nanorods were successfully grown on common glass substrates using a simple solvothermal method via the precursors of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and Hexamethylenetetramine (C₆H₁₂N₄) with equal molar concentration at 0.01 mol/l, 0.025 mol/l, 0.05 mol/l, and 0.075 mol/l. The ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning electron microscopy, UV-Vis absorption spectrophotometer and photoluminescence (PL) spectrometer. XRD results indicated that all the ZnO nanorods were preferentially grown along [0 0 0 1] direction (c-axis). With an increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the diffraction intensity of ZnO nanorod along c-axis also increased. Scanning electron microscopy images showed that the well-faceted hexagonal ZnO nanorods were grown vertically from the common glass substrates. In addition, with the increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the exciton band of ZnO nanorods determined by UV-Vis absorption spectra gradually became narrow and the intensity of exciton band also remarkably augmented. Photoluminescence spectra showed that with the increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the position of emission peak of ZnO nanorod blue-shifts towards shorter wavelength in UV region and the luminescence intensity remarkably enhances in visible emission range (470-630 nm).     

混合溶剂热法合成KTa0.6Nb0.4O3铁电陶瓷粉体的研究

以Nb2O5和Ta2O5为前驱反应物,KOH为矿化剂,采用异丙醇和水为反应介质的混合溶剂热法,成功地合成了四方相、钙钛矿结构的KTa0.6Nb0.4O3陶瓷粉体.XRD、SEM、TEM以及FT-IR等研究结果表明:在混合溶剂热合成过程中,反应溶剂(水/异丙醇)、矿化剂KOH的摩尔浓度和反应温度是影响KTN粉体结构和形貌的关键因素.在KOH浓度1～2M,异丙醇:水=80:20、反应温度250℃,时间8h合成条件下,得到了晶粒形状呈规则的立方体,边长分布约为100～300nm的KTN陶瓷粉体.     

Large-scale synthesis of CuS hexaplates in mixed solvents using a solvothermal method

Large-scale covellite CuS hexaplates were successfully synthesized by the 200 °C solvothermal reactions of CuCl₂.2H₂O and (NH₄)₂S in C₂H₅OH-H₂O mixed solvents containing HCOOH as a pH stabilizer, including different amounts and molecular weights (MWs) of polyethylene glycol (PEG). By using XRD and SAED, CuS (hcp) was detected. XRD peaks of the product, synthesized in a solution containing 5 g PEG6000 and 1.5 ml HCOOH for 5 h, are in accordance with those of the simulation and database. The (110) peak shows the preferential growth, corresponding to the hexaplates, characterized using SEM, TEM and HRTEM. CuS hexaplates with the (100) and (010) lattice planes at an angle of 120° were detected on the flat surface, and the (002) lattice plane on the edge. UV-vis absorption edge was detected at 610 nm (2.03 eV), and the PL emission at 361 nm (3.43 eV). Phase and morphology formations were also explained according to the experimental results.     

The superhydrophilicity of Al–TiO2 nanometer sized material synthesized using a solvothermal method

This study focuses on the surface properties of nano-sized Al–TiO₂ synthesized by a solvothermal method. The results indicate that the Al/TiO₂ particles, which are below 25 nm in size, exhibited a uniformly spherical anatase structure. The results of XRD and FT-Raman spectra showed that the Al ion was well incorporated into TiO₂ anatase framework. The Al-incorporated TiO₂ exhibited a larger (195–299 m²/g) area compared with that formed by pure TiO₂ (45 m²/g). In addition, the XPS spectra showed that Al–TiO₂ possessed a higher hydrophilic property than pure TiO₂ did. Consequently, these results of characterization supported our proposition that super-hydrophilicity was enhanced in Al–TiO₂ than that in pure TiO₂, it resulted from the contact angle below 1° for water droplets under 365 nm radiations.     

水热法合成高发光强度ZnS:Cu,Al纳米荧光粉研究

采用水热法直接合成了高发光强度的ZnS:Cu,Al纳米荧光粉.XRD和TEM测试结果表明,合成纳米晶为纯立方相结构,球形纳米晶尺寸约15nm,尺寸分布窄,分散性好.首次系统地研究了不同[S2-]/[Zn2+]和[Al3+]/[Cu2+]比值对清洗样品和不清洗样品的光致发光(PL)光谱的影响.实验结果表明,激活剂浓度不变而改变[S2-]/[Zn2+]摩尔比时,发光强度显著变化,同时未清洗样品的PL强度均比清洗样品的强,且未清洗样品强度增强的比值在低的[S2+]/[Zn2+]时更显著.这说明其发光机理为紫外光激发材料表面的发光中心,即PL强度决定于纳米材料的表面态,此外掺杂的激活剂摩尔比同样对PL光谱有影响.在我们的实验中,用343nm紫外光激发时,n[S2-]:n[Zn2+]=3,n[Al3]:n[Cu2+]=2时未清洗样品的发光最强,此时于室内照明条件下可观察到明亮的绿光.     

Growth of dandelion-shaped CuInSe2 nanostructures by a two-step solvothermal process

CuInSe(2) (CIS) nanodandelion structures were synthesized by a two-step solvothermal approach. First, InSe nanodandelions were prepared by reacting In(acac)(3) with trioctylphosphine-selenide (TOP-Se) in 1-octadecene (ODE) at 170?°C in the presence of oleic acid. These InSe dandelions were composed of polycrystalline nanosheets with thickness < 10 nm. The size of the InSe dandelions could be tuned within the range of 300 nm-2 μm by adjusting the amount of oleic acid added during the synthesis. The InSe dandelion structures were then reacted with Cu(acac)(2) in the second-step solvothermal process in ODE to form CIS nanodandelions. The band gap of the CIS dandelions was determined from ultraviolet (UV) absorption measurements to be ～ 1.36 eV, and this value did not show any obvious change upon varying the size of the CIS dandelions. Brunauer-Emmett-Teller (BET) measurements showed that the specific surface area of these CIS dandelion structures was 44.80 m(2) g(-1), which was more than five times higher than that of the CIS quantum dots (e.g. 8.22 m(2) g(-1)) prepared by using reported protocols. A fast photoresponsive behavior was demonstrated in a photoswitching device using the 200 nm CIS dandelions as the active materials, which suggested their possible application in optoelectronic devices.