Phase Purity Analysis and Optical Studies of Bi2O3 Nanoparticles Suitable for Photocatalytic Activity

Bismuth oxide was prepared using hydrothermal route and the er effect of pH on the phase of Bi2O3 reported. Phase pure alpha-Bi2O3 was prepared at the pH of 13 and its phase purity was confirmed from the X-ray diffraction pattern. At the pH of 10, 11 and 12 the hydrothermal synthesis yields Bi(OH)(3), (alpha,gamma,- Bi2O3) & Bi2O4 and mixture of alpha-Bi2O3 & Bi2O4, respectively. The optical band gaps were calculated from reflectance spectra using the Kubelka-Munk relation and the values decrease from 3.050(3) to 2.686(3) eV with the increase in pH value. Photoluminescence intensity decrease with the increase of pH value indicated the increase in the charge separation efficiency. In the application point of view, the photocatalytic activity of the samples was evaluated for methyl orange and among the four samples, alpha-Bi2O3 degraded 67% within 4 h. The degradation of dye was analyzed using pseudo first-order kinetics and the rate constant value was 0.0045(3) min(-1) with the correlation coefficient of 0.983.