Hydrothermal synthesis of CeO2 nano-octahedrons

CeO₂ nano-octahedrons were synthesized with a facile hydrothermal synthesis process where Ce(NO₃)₃·6H₂O and urea were used as a cerium resource and mineralizer respectively and no surfactant or template was applied. The effects of synthesis parameters such as reaction temperature, reaction time, as well as the dosages of Ce (NO₃)₃·6H₂O and urea were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were conducted to characterize the crystalline and morphology of the obtained CeO₂ powders. The optimal reaction condition to prepare the CeO₂ of the desired fluorite structure was established. The possible mechanism of synthesis of CeO₂ with a nano-octahedron morphology was illustrated.     

纳米晶MnFe2O4的水热法合成及其磁性能

采用水热法制备了软磁材料MnFezO4纳米晶,借助XRD、IR、SEM和VSM对产物进行了表征,着重研究了水热条件如温度和时间等对MnFe2O4纳米晶的形成及其结构和磁性能的影响。结果表明水热温度较低时的产物晶化度和纯度低,表现出较差的磁性能,温度为120℃的产物其饱和磁化强度为15．34emu／g,剩磁比为0．08,矫顽力为8lOe,而在200℃下水热产物饱和磁化强度为51．49emu／g,剩磁比达到0．14,矫顽力为121Oe。     

Vanadium dioxide nanobelts: Hydrothermal synthesis and magnetic properties

VO₂ (B) nanobelts were prepared by a hydrothermal method at 180 °C using V₂O₅·nH₂O sol and H₂C₂O₄·2H₂O as starting agents. The obtained nanobelts have diameters ranging from 50 to 100 nm in width, 20-30 nm in thickness with lengths up to 1.5 μm. Measurements of the static magnetic susceptibility provide evidence for two phase transitions at T₁ = 225 K and T₂ = 290 K, respectively. Below T₁, the data suggest the presence quasi-free as well as of strongly antiferromagnetic correlated spins associated to V⁴⁺-ions.     

Solvothermal route to S-deficient CoS nanoplates and their cathodoluminescence and magnetic properties

A facile solvothermal method was developed to fabricate CoS nanoplates using ethylenediamine as solvent. The microstructure characterizations indicate that the CoS nanoplates have well-crystalline hexagonal phase and regular hexagonal or pentagonal shape. The XPS and ICP-AES measurements confirm the chemical composition of nanoplates is S-deficient CoS0.921. Cathodoluminescence spectra of both a large area of the nanoplates and individual nanoplate show broad emission bands centered at 615 nm. Magnetic measurements including magnetization dependence of temperature and magnetic hysteresis loops reveals that the CoS nanoplates exhibit room-temperature ferromagnetic behavior. It is found that intrinsic point defects mainly as V(s), Co(i) and/or the complex defects of V(s) and Co(i) should be responsible for both the broad emission band and the unique ferromagnetism.     

Hydrothermal synthesis and optical properties of Pb2+ doped ZnO nanorods

Single-crystalline Pb²⁺ doped ZnO nanorods were synthesized by a hydrothermal method in the presence of cetyltrimethyl ammonium bromide (CTAB). The obtained Pb²⁺ doped ZnO nanorods were in diameters of ∼150 nm and in lengths of ∼3 μm. The nanorods grow along the [011¯0] direction. The Pb²⁺ doped ZnO nanorods show violet and blue emission bands centered at 415, 438 and 467 nm, respectively. The possible growth mechanism of the Pb²⁺ doped ZnO nanorods was also discussed.     

Co^2＋掺杂ZnO纳米线的制备与光学特性的研究

在十六烷基三甲基溴化铵表面活性剂辅助下,通过水热合成法制备了Co2 掺杂ZnO纳米线.纳米线的直径为100～160nm,长度约为10μm.纳米线沿(001)方向生长.Co2 掺杂ZnO纳米线紫外-可见(UV-vis)吸收光谱曲线,显示掺杂的ZnO纳米线在200～300nm波段之间都有很强的紫外吸收,在波长360～370nm处显示很好的激子吸收,与体相的激子吸收峰(373nm)相比产生了蓝移.纳米线分别在385、409、433、462和495nm波段表现出发光特性,简略的讨论了其发光机制.     

Hydrothermal synthesis of magnetic reduced graphene oxide sheets

We demonstrated an environmental friendly and efficient route for preparation of magnetic reduced graphene oxide composite (MN-CCG). Glucose was used as the reducing agent in this one-step hydrothermal method. The reducing process was accompanied by generation of magnetic nanoparticles. The structure and composition of the nanocomposite was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, thermal gravimetric analysis, atomic force microscopy and transmission electron microscopy. It was found that the prepared MN-CCG is highly water suspendable and sensitive to magnetic field.     

Hydrothermal synthesis and optical properties of CuS nanoplates

CuS nanoplates have been successfully prepared in the presence of cation surfactant cetyltrimethylammonium bromide (CTAB) by hydrothermally treating the solution of CuCl₂·2H₂O and Na₂S·9H₂O at 180 °C for 24 h. The as-prepared CuS nanoplates are of hexagonal phase and are single crystal. The thickness and edge length of the nanoplates are about 15 nm and 60 nm, respectively. The products was characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, photoluminescence measurements and ultraviolet-visible light spectrophotometer. The influences of synthetic parameters, such as reaction time and CTAB, on the morphologies of the products have been investigated.     

Hydrothermal synthesis of different 3D SnO2 nanostructures and their gas-sensing properties

Different morphologies of 3D SnO₂ nanostructures, including sphere-like, net-like, and flower-like, have been successfully synthesised via a facile hydrothermal method. The products were characterized by X-ray diffraction and scanning electron microscopy. The possible growth mechanism of different SnO₂ nanostructures was discussed in detail. We found that the citric acid and PEG play significant roles in synthesizing the flower-like and net-like nanostructures. Furthermore, the gas-sensing properties of the samples were investigated towards the reducing ethanol gas. The results indicate that the flower-like and net-like SnO₂ show larger gas sensing properties than sphere-like SnO₂.     

硫化锑单晶纳米带的水热制备、表征及性能研究

运用水热法大量制备出了高长径比的硫化锑(Sb2S3)纳米带。十六烷基三甲基溴化铵(CTAB)作为形貌控制剂在纳米带的形成过程中起了至关重要的作用,运用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和高分辨透射电镜(HRTEM)等对所得产物进行了系统的表征,结果表明制备出的Sb2S3纳米带是沿[001]晶面方向生长的,带的宽度在1μm以内,长度可达几十个微米。对Sb2S3纳米带的生长机理和光学性质进行了初步的讨论和研究。     

Hydrothermal synthesis of different SnO2 nanosheets with CO gas sensing properties

In this work, 2D SnO₂ nanosheets were synthesized via a polyvinylpyrrolidone (PVP)-assisted hydrothermal method. X-ray diffraction and scanning electron microscopy were used to examine the chemical composition and nanostructures. It was found that the concentration of PVP played a critical role in governing the assembly process of nanostructures. Further, their gas-sensing performances were investigated comprehensively. The nanosheet-III structures were found to show the most superior gas-sensing properties due to their largest specific surface and fashionable assembly.     

Hydrothermal synthesis,characterization and properties of SnS nanoflowers

Novel tin (II) sulfide (SnS) nanoflowers were successfully synthesized via a simple thioglycollic acid (TGA)-assisted hydrothermal process at 250 °C. X-ray diffraction, scanning electron microscopy and energy-dispersive spectrometry were employed to characterize the structure, morphology and chemical composition of the product, the results of which reveal that the product is composed of well crystallized orthorhombic SnS nanoflowers. The band gaps were obtained by analyzing UV-vis absorption spectrum; herein, the direct and indirect optical band gaps are 1.53 and 1.43 eV, respectively. Furthermore, we discussed critical factors (e.g., TGA, SnCl₂/Na₂S mol ratio of the reactants, hydrothermal temperature, and sulfur source) for hydrothermal formation of the SnS nanoflowers.     

层状LiMnO_2的水热合成

采用X射线衍射的方法系统研究了由Mn2O3和LiOH作为反应物时,正交层状LiMnO2的水热合成条件.结果表明,在200℃温度下,Mn3+与Li+的摩尔比小于等于1∶10,反应2 h以上可获得纯的产物.Rietveld分析表明,产物为正交层状结构,空间群为Pmnm,晶胞参数为a=566(3),b=5.751(2),c=2.808(1);晶体结构中,在2a位置有2%~3%的Li+、Mn3+占位无序.对200℃温度下,Mn3+与Li+的摩尔比为1∶10,反应2 h合成的正交层状LiMnO2的电化学性能测试表明,在0.1C的电流下,循环3次后放电容量可达175 mAh.g-1.     

Hydrothermal synthesis of TiO2 nanofibres

TiO₂ nanofibres were synthesized by the hydrothermal method. The result shows that the growth of TiO₂ nanofibres is sensitive to the concentration of NaOH and the heating temperature.     

Hydrothermal synthesis and gas sensing properties of different titanate nanostructures

Anatase TiO₂ nanoparticles and other three different morphologies of titanate nanostructures such as nanotubes, nanosheets and nanowires were successfully prepared by hydrothermal method. The structures and morphologies of the final products were characterized with field-emission scanning electron microscopy (FE-SEM). Phase analysis was carried out using X-ray diffraction (XRD). A novel formation mechanism from anatase TiO₂ nanoparticles to titanate nanowires is proposed based on FE-SEM. The gas sensing properties to ethanol were also investigated. The results indicate that nanotubes, nanosheets, nanowires show much less resistance and larger response than nanoparticles.     

Hydrothermal synthesis and optical properties of zinc silicate hierarchical superstructures

A simple hydrothermal method has been developed for fabricating hemimorphite zinc silicate, Zn₄Si₂O₇(OH)₂·H₂O (ZSO). Three-dimensional ZSO hierarchal superstructures are deposited on the Si substrate. The product is characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscope. The characterization results of the sample show individual ZSO hierarchical architectures are assembled by many well-aligned and highly ordered rod bundles. The morphologies of the rod bundles within the ZSO hierarchal superstructures can be conveniently controlled, by selecting the different reactant concentrations, with excellent reproducibility. The luminescence spectra showed that the ZSO hierarchical superstructure had a stronger emission peak at 436 nm and a weaker emission peak at 418 nm.     

Hydrothermal synthesis and electrochromic properties of potassium tungsten oxide nanorods

Hexagonal K2W4O13 nanorods have been synthesized by hydrothermal treatment of the WO3 x H2O precipitate at 180 degrees C in the presence of K2SO4. The K2W4O13 nanorod single crystals of approximately 12 nm in diameter and tens to few hundreds nm long with the principal axis along the (001) direction were obtained when hydrothermal treatment was conducted in the presence of sufficient amount of K2SO4 while shorter nanorods with the same preferred orientation were obtained when less amount of K2SO4 was employed. On the other hand, square platelets of approximately 100 nm wide were obtained when prepared in the absence of the K2SO4. The important role of K2SO4 on morphological control of the hydrothermal products was explained based on selective adsorption of the sulfate ions on the crystal planes parallel to the (001) direction retarding the growth of these faces. The nanorod film showed satisfactory electrochromic property and can be used as a promising material in electrochromic application.     

Hydrothermal synthesis and photoluminescence properties of cerium-doped cadmium tungstate nanophosphor

The present paper reports synthesis and photoluminescence studies of cadmium tungstate (CdWO₄) and cerium-doped cadmium tungstate. The samples were synthesised by low cost and low temperature hydrothermal method and characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence analysis. XRD pattern reveals that the CdWO₄ has monoclinic wolframite structure. The FTIR spectrum of cerium-doped CdWO₄ exhibits broadband below 700 cm^?1 which is due to the δ (Ce–O–C) mode. The TEM images show that size of particle is approximately 60–120 nm in both samples. A broad intense peak was observed at 474 nm when the samples were excited with 263 nm. A broad intense peak was observed at 475 nm when the samples were excited with 600 nm. The intensity of the 474 nm peak decreases with increase in cerium doping concentration. The observation of 475 nm peak when excited with 600 nm is upconversion luminescence. This upconversion emission is due to energy transfer upconversion process involving Cd²⁺ ions and [WO₆]^6? ions. Ce³⁺ ion is responsible for the peak shift of 6 nm.     

CdWO4纳米棒的制备及光致发光性能

以Na2WO4.2H2O和CdCl2.2.5H2O为主要原料,以表面活性剂十二烷基苯磺酸钠(SDBS)为添加剂,水热反应合成了CdWO4纳米棒。用XRD、TEM、EDS、SAED等对产物进行了表征,初步探讨了CdWO4纳米棒的形成机理,测试了CdWO4纳米棒的光致发光(PL)谱。结果表明:产物为长0.8～1.5μm,直径40～120nm的CdWO4纳米棒;SDBS对CdWO4纳米棒的形成起了关键作用,浓度为0.01mol/L条件下制备的CdWO4纳米棒的长径比最大;随着Cd-WO4纳米棒长径比的增大,其PL光谱增强。