Solvothermal synthesis and photoluminescence properties of BiPO4 nano-cocoons and nanorods with different phases

Hexagonal phase BiPO4 nano-cocoons and monoclinic phase BiPO4 nanorods have been synthesized in the mixed solvents of glycerol and distilled water with the volume ratio of 2:1 at 200 °C. The solvothermal evolution process from hexagonal phase BiPO4 nano-cocoons to monoclinic phase BiPO4 nanorods was observed by varying the reaction time from 1 to 3 h. In the hydrothermal condition at 160 °C, the similar phase transformation from hexagonal phase BiPO4 to monoclinic phase BiPO4 was also observed, accompanying with a morphology transformation from nanorods to octahedron-like microcrystals. It was found that the volume ratio of glycerol to water in the solvothermal condition had a great impact on the shapes of products, while it had no influence on the formation of different phases. The fluorescence spectra of hexagonal phase BiPO4 nano-cocoons and monoclinic phase BiPO4 nanorods were also studied.