Chunrui Wang

Raman scattering, far infrared spectrum and photoluminescence of SnS2 nanocrystallites

Abstract The optical property of SnS2 nanocrystallites has been investigated by Raman scattering, far infrared spectrum and photoluminescence at room temperature. The Raman and far infrared spectrum of the SnS2 nanocrystallites have a shift in comparison with that of the SnS2 single crystals. The shift is mainly attributed to nanosize effect. The intralayer and interlayer force constant of SnS2 nanocrystallites have been calculated by using a linear chain model. The photoluminescence of SnS2 nanocrystallites is reported for the first time.

Growth of belt-like SnS crystals from ethylenediamine solution

Tin (II) sulfide crystal belts, with tens of micrometers in width, several millimeters in length and several micrometers in thickness, was successfully grown in ethylenediamine (en) via a solvothermal route at low temperature. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), induced-coupled plasma (ICP), X-ray photoelectron spectra (XPS). The vibrational property of the as-prepared SnS belt was examined by Raman spectra. The possible growth mechanism of SnS crystal belts was discussed, which revealed that the solvent (en) was crucial in the formation of belt-like SnS crystals.

Magnetotransport properties in La1−xCaxMnO3 (x=0.33, 0.5) thin films deposited on different substrates

Magnetotransport properties of La1−xCaxMnO3 (x=0.33, 0.5) thin films on different substrates are systematically studied. Due to the different lattice-substrate mismatch between films and substrates, compressive, and tensile epitaxial strain can be induced, respectively. The structure distortion induced by the strain with different sign influences the transport property and magnetoresistance. The tensile strain induces an increase of resistivity and magnetoresistance, while the resistivity peak temperature decreases. Compressive strain leads to a contrary behavior. The microstructure of films is also dominated by the lattice-substrate mismatch strongly. The inhomogeneities and different mixed domain structure induce the broadening of magnetic transition in films on SrTiO3 and NdGaO3, and a sharp increase in magnetoresistance in La0.67Ca0.33MnO3 films with increasing field. In addition, the low temperature metal–insulator transition in the resistivity of La0.5Ca0.5MnO3 film on LaAlO3 also indicates the samp...

Blue-light emission of nanocrystalline CaS and SrS synthesized via a solvothermal route

Abstract CaS and SrS nanocrystallites have been successfully synthesized via a solvothermal route by the reaction between XCl 2 (X=Ca, Sr) and sulfur at relatively lower temperature for the first time. XS (X=Ca, Sr) nanocrystallites are efficient emission luminescence in comparison with that of bulk materials at room temperature. The emitted light of CaS and SrS nanocrystallites is yellow–green and blue, respectively.

Fabrication of BiTeI submicrometer hollow spheres

BiTeI submicrometer hollow spheres with diameters of 200–300 nm have been synthesized by an iodine transport hydrothermal method without the use of template materials or surfactants. The preparation was carried out in an autoclave in the temperature range 190–200 °C with Bi2Te3 and I2 as reactants. X-Ray powder diffraction patterns and transmission electron microscopy images show that the product is BiTeI with a hollow sphere structure. The sphere wall is composed of BiTeI nanoparticles with an average diameter of 5 nm and a thickness of ca. 10 nm. A possible growth mechanism for the hollow structure is proposed. The first excitonic peak of the BiTeI hollow spheres is considerably blue shifted in comparison with the band gap of the bulk material, which can be attributed to quantum confinement effects.

A γ-irradiation reduction route to nanocrystalline CdE (E=Se, Te) at room temperature

Abstract Nanocrystalline CdE (E=Se, Te) has been successfully synthesized by employing chalcogenites (Na 2 SeO 3 and K 2 TeO 3 ) as chalcogen sources via γ-irradiation route in the presence of ammonia at room temperature. In the procedures, SeO 3 2− and TeO 3 2− anions were gradually reduced to release Se 2− and Te 2− in the irradiation field, and then the reduced Se 2− or Te 2− was combined with Cd 2+ ions to produce CdE. The final products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).

Hydrothermal preparation of luminescent PbWO4 nanocrystallites

Abstract Lead tungstate (PbWO 4 ), an important inorganic scintillator, was synthesized via a mild hydrothermal reaction route. X-ray diffraction (XRD) and a transmission electron microscope (TEM) were used to characterize the products. The effects of solvents, reagents, reaction temperature, and time on the formation of the PbWO 4 nanocrystalites were investigated. The examination of photoluminescence (PL) property of the as-prepared samples revealed that the PL of the as-prepared PbWO 4 nanocrystalites was strongly dependent on the preparation conditions.

Preparation and Photoluminescence of CaS:Bi, CaS:Ag, CaS:Pb, and Sr1 − x Ca x S Nanocrystallites

CaS:Bi, CaS:Ag, CaS:Pb, and Sr 1-x Ca x S nanocrystallites were synthesized via a solvothermal method at a relatively low temperature. The method is more environmentally friendly than traditional preparations (very little sulfur-based gases are formed and the method does not involve toxic H 2 S or CS 2 ). Additionally, it is simple, convenient and produces a good yield. The products with an average diam of 30-100 nm were stable at humid air. The emission color of Sr 1-x Ca x S nanocrystallites varied from blue (SrS) to red (Sr 0.6 Ca 0.4 S). The emitted light of CaS:Bi, CaS:Ag and CaS:Pb nanocrystallites are blue, red, and blue, respectively.

Alkali metal substitution effects in Mg1-xAxB2 (A = Li and Na)

Abstract We report the alkali metal substitution effects on the structure and superconductivity of Mg 1− x A x B 2 (A=Li and Na) compounds. X-ray diffraction results show that nearly single phase Mg 1− x A x B 2 can be obtained for x ⩽0.15 Li and x ⩽0.2 Na substitution. The lattice parameters a and c decrease with Li substitution. As substituted by Na, both a and c show an increase at low Na concentration, then decrease with substitution at higher Na concentrations. The change of a with Li and Na substitution is explained by two overlapping effects: ion size and an increase of in-plane coupling upon hole doping. The tendency of c -axis contraction in Mg 1− x Li x B 2 is consistent with theoretical prediction. The T c decreases when Li concentration is increased, while the change of T c upon Na substitution is not apparent.

A hexane solution deposition of SnS2 films from tetrabutyltin via a solvothermal route at moderate temperature

SnS2 films have been deposited on glass and alumina plate substrates by the reactions between an organotin precursor [tetrabuyltin, (CH2CH2CH2CH3)4Sn] and carbon disulfide in n-hexane at the temperature range 180–200 °C for 10–40 h. The reaction system was oxygen free and applied at a moderate temperature. The films so prepared were characterized by techniques of X-ray diffraction, Scanning electron microscopy, Raman and Mossbauer spectroscopies. The films deposited on glass as well as on alumina plate have an average thickness of 30 μm, but have different rose-like morphologies, which are influenced by both the anisotropic growths of crystals and the different substrate structures. Photoluminescence measurements show that the films have an emission peak at approximately 590 nm.