Preparation And Properties Of SnO₂ Nanocomposite

Tin oxide?SnO₂? is a n-type semiconductor with a wide band gap?Eg=3.6 eV? and it has been widely used in gas sensors, dye-based solar cells, photodetectors and lithium batteries due to its good physical and chemical stability, electrical and optical properties. Also, SnO₂ is an excellent photocatalyst for dye waste water and a host material for rare- earth ions.SnO₂ is selected as the object in the studies. SnO₂ and its nanocomposites were synthesized by hydrothermal method and precipitation method. The structure, morphology, photocatalytic and luminescence properties were characterized and analyzed respectively. The main research contents and results are as follows:?1? Nano-sized SnO₂ particles were synthesized by hydrothermal method using SnCl2×2H2O as raw materials and tartaric acid as complexing agents. The phase structure, morphology and optical absorption properties of the as-synthesized SnO₂ were characterized by X-ray powder diffraction, scanning electron microscope, UV-Vis spectrophotometer and fluorescence spectrophotometer. To investigate the photocatalytic activity of the product, Acid Red B was used as simulated dye wastewater. The results indicate that the samples synthesized at different hydrothermal temperature are all tetragonal phase SnO₂ with space group P42/mnm and cell parameters a=b=0.4738 nm,c=0.3187 nm. SnO₂ obtained at 160 ? shows excellent photocatalytic activity,the particles are nearly spherical in shape, and the size is about 13²3 nm. When the dosage of nano-SnO₂ is 20 mg/50 m L, UV light is used as irradiation source and reaction time is 50 min, the degradation rate can reach to 97.1%. And the degradation of dye Acid Red B can be considered as the first-order reaction.?2? A ZnO-SnO₂ nanocomposite was prepared by the precipitation method employing NH3×H2O as the precipitant. Acid Red B was used as simulated dye wastewater to investigate the photocatalytic activity of the samples. The results indicate that the samples are all consisted of hexagonal phase ZnO and tetragonal phase SnO₂ under different calcination temperature and Zn/Sn. The particles are mainly spherical except for a small amount of short column, and the particle size is about 70¹00 nm. When the calcination temperature is 600 oC and the mole ratio of Zn/Sn is 2:1, the synthesized sample has a band gap energy of 3.40 eV. The degradation rate for Acid Red B is nearly 100% illuminated with UV light for 120 min. Due to the difference in the energy band for two compounds, photo-generated electrons and holes can be separated effectively in ZnO-SnO₂ nanocomposite, thus photocatalytic efficiency is improved obviously.?3? Orange-red-emitting phosphors SnO₂:Eu nanoparticles were synthesized by hydrothermal method followed by calcination process. SnO₂:Eu samples obtained with different calcination temperature and time are all tetragonal phase with space group P42/mnm when pH=1. The particles are nearly spherical, and the average size is about 100 nm. The excitation spectrum is composed of a broad band ascribed to the direct optical transition from valence band to conduction band of SnO₂. The emission spectrum is consisted of a strong peak and several weak peaks, and the main peak is located in 589 nm, corresponding to the 5D0?7F1 magnetic dipole transition of Eu³⁺. The SnO₂:xEu phosphors present excellent orange-red-emitting properties when the concentration?x? of Eu³⁺ is 0.09, pH=1, calcination temperature and time are 900 oC and 3 hours, respectively.