Weichao Yu

Polymer-controlled growth of Sb2Se3 nanoribbons via a hydrothermal process

Abstract Sb 2 Se 3 nanoribbons have been prepared by a hydrothermal process at 180°C for 20xa0h. X-ray diffraction pattern indicates that the product was orthorhombic Sb 2 Se 3 phase with lattice constants a =11.747, b =11.799 and c =3.987xa0A. Field emission scanning electron microscope images show that nanoribbons have diameters in the range of 25–100xa0nm and lengths up to ∼30xa0μm. High-resolution transmission electron microscopy image reveals that the nanoribbon was of single crystal and grew along the [0xa00xa01] direction. The peak of absorption appeared at 727xa0nm in the UV-vis spectrum. A possible mechanism on the formation of the nanostructures was also discussed.

Solvothermal synthesis of Sb2S3 nanowires on a large scale

Sb2S3 nanowires with high aspect ratios have been successfully prepared on a large scale using SbCl3 and Na2S as starting materials in ethylene glycol at 200°C for 10 h. Field emission scanning electron microscopy images and transmission electron microscopy images show that the nanowires have diameters in the range of 20–100 nm and lengths up to 50 μm. Diffuse reflection spectrum indicates that the as-prepared Sb2S3 nanowires have obvious quantum size effects. The effects of reaction parameters on the growth of nanowires were discussed. A possible mechanism on the formation of the Sb2S3 nanowires was proposed.

Surfactant-aided solvothermal synthesis of dinickel phosphide nanocrystallites using red phosphorus as starting materials

Abstract A surfactant-aided solvothermal synthesis route has been proposed to produce well-dispersed dinickel phosphide nanocrystallites by using nickel dichloride and nontoxic red phosphorus as starting materials. It was found that the polymeric surfactant polyacrylamide played a crucial role in the reaction dynamic process. X-ray powder diffraction pattern indicated that the products were hexagonal phase with cell constants a =0.5846xa0nm, c =0.3368xa0nm, which was also confirmed by electron diffraction (ED) pattern. The transmission electron microscopy (TEM) was used to study morphologies of the final products. It was interesting that the average size of dinickel phosphide crystallites decreased from 200 to 20xa0nm with temperature increasing from 120°C to 180°C. The photoluminescence (PL) of the as-prepared samples was investigated at room temperature. The results demonstrated that the emitted light of Ni 2 P nanocrystallites is ultraviolet (peak at 346xa0nm), which indicated that dinickel phosphide nanocrystallites were potential luminescent materials.

Dendritic growth of PbS crystals with different morphologies

Abstract PbS dendritic crystals with different morphologies have been successfully prepared via a solvothermal process. TEM observations show that the as-prepared PbS dendrites exhibit cross-like morphology for primary arms and fishbone shape for secondary arms. The reactive precursors and solvents have much influence on the growth behavior of PbS dendrites. The possible growth mechanisms are briefly discussed, while the orthogonal growth of PbS dendrites are assigned to 〈1xa00xa00〉 directions.

Shape-controlled synthesis of BaWO4 crystals under different surfactants

BaWO4 crystals with different morphology, such as olive-like, flake-like, and whisker-like structure have been successfully prepared through a hydrothermal process in the presence of different surfactants—C17H33COOK, C19H39COOK, and C25H51COOK, respectively. X-ray powder diffraction (XRD) shows that the crystals have been well crystallized. The observation results of scanning electron microscopy (SEM) on the obtained samples have revealed that the selection of surfactants and the concentration of the starting materials can highly affect the morphology and size of BaWO4 crystals.

Structural, optical, and electrical properties of indium tin oxide films with corundum structure fabricated by a sol–gel route based on solvothermal reactions

Abstract This article reports on the fabrication of the Sn-doped In 2 O 3 (ITO) films with corundum structure by a sol–gel route, using InCl 3 ·4H 2 O, SnCl 4 and de-ionized water as starting materials. Based on the hydrolysis of In 3+ and Sn 4+ in a solvothermal system using ethylenediamine as solvent, the aqueous sol was prepared, and acted as the precursor of the ITO films. The films were coated on quartz glass by the dip coating process, and annealed in air in the range of 350–750 °C. The structure, morphology, and composition of the films were investigated by X-ray powder diffraction, electron diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectrometer, indicating that the films were composed of ITO nanoparticles with corundum structure. The spectral transmittance of the films was measured in the wavelength range of 250–950 nm using an UV–vis spectrophotometer. The electrical resistivity of the films was measured by the four-probe method at room temperature. It was found that the optical and electrical properties of the films were affected significantly by the annealing temperature in the range of 350–580 °C due to the improvement of the crystallinity of the films with increasing temperature, and became stable when the annealing temperature was higher than 580 °C. The 6.8 at.% Sn-doped film annealed at 680 °C had high transmittance above 78% in wide visible range with maximum of 83% at 875 nm wavelength, and showed the lowest resistivity of 2.0×10 −2 Ωxa0cm.

Growth of single-crystal PbS nanorods via a biphasic solvothermal interface reaction route

Abstract Rod-like PbS nanocrystals were synthesized via a novel biphasic solvothermal interface reaction route at 140–160°C. The as-prepared nanorods have diameters of 30–160xa0nm and lengths of up to several micrometers, which yield typical aspect ratios of 10–70. The possible mechanism is briefly discussed for the growth of the rod-shaped PbS nanocrystals. The observations of transmission electron microscopy are in good agreement with the proposed template-aggregation-growth mechanism for PbS nanorods.

Preparation, characterization and optical properties of terbium oxide nanotubes

Tb2O3 nanotubes were fabricated by calcination of the precursor Tb(OH)3 nanotubes prepared by a template-assisted hydrothermal route. The oxide nanotubes have outer diameters ranging from 80 to 100 nm, wall thickness of about 30 nm, and lengths up to several micrometers. The optical absorption spectrum shifted to high energy and became broad, more lines were observed in the emission bands in comparison with the bulk. Surface effects were found to account for these novel optical properties.

The synthesis of hollow CdS nanospheres packed with square subunits

Abstract Hollow CdS nanospheres packed with square subunits were fabricated via microwave irradiation and pentaerythriol. The products were characterized with XRD, TEM, HRTEM, EDX and UV–vis spectrum. The results indicate that pentaerythriol is necessary in the formation of square subunits with high degree of crystallinity. A possible growth mechanism was proposed.

Single-source precursor route to carbon nanotubes at mild temperature

Abstract Carbon nanotubes were synthesized via a single-source precursor route at 500xa0°C, using iron carbonyl both as carbon source and catalyst. The X-ray power diffraction pattern indicates that the products are hexagonal graphite. Transmission electron microscope (TEM) images of the sample reveal carbon nanotubes with an average inner (outer) diameter of 30 nm (60 nm). High-resolution TEM indicates that fabrication of the carbon nanotube walls was composed of ca. 40 graphene layers. The Raman spectrum shows two strong peaks at 1587 and 1346 cm−1, corresponding to the typical Raman peaks of graphitized carbon nanotubes. This method avoids the separation of raw material from solvent and simplifies the operation process. At the same time, the research provides a new route to large-scale synthesis of carbon nanotubes.