Effects of pH on the microstructures and optical properties of Sn3O4 crystals prepared by hydrothermal method

Intermediate tin oxide (Sn3O4) crystals have been successfully synthesized through a simple one-pot hydrothermal route by employing SnCl2·2H2O and NaOH as raw materials. The crystalline structure, morphology and optical properties of Sn3O4 materials were characterized by using X-ray diffraction, field-emission scanning electron microscopy, and UV–vis absorption spectroscopy, respectively. It was found that pH value of the media had significant impacts on microstructures and optical properties of products. Products obtained from acidic media (pH=2.20) were composed of pure Sn3O4 nanosheets with grain size of 100 nm, while those prepared in alkaline conditions (pH=12.35) consisted of irregular Sn3O4 micro-flakes. Their optical band gaps were calculated to be 2.68 and 2.85 eV, correspondingly. Possible mechanism was discussed for the formation of Sn3O4 crystals in different pH.