Facile synthesis and purplish blue luminescence of the binary mixed valence compound Bi4O7 microcrystals

• Pure mixed valence compound Bi4O7 was synthesized by a facile chemical strategy.
• The reaction temperature and pH value play the vital role in phase transformation.
• Bi4O7 transformed from Bi2O4 with the increase of temperature in the synthesis.
• The luminescence of product shows a broad band purplish blue emission.

We presented a facile chemical strategy to synthesize the pure mixed valence compound Bi(III,V)4O7 microcrystals. Our results indicated that Bi4O7 microcrystals could transformed from Bi2O4 with the increase of temperature in the hydrothermal synthesis. The reaction temperature and the pH value of solution play the vital role in the phase transformation. The luminescent behavior of the product was investigated and there exists a broad band emission from 400 to 475 nm in the visible region, which corresponds to the purplish blue light. Therefore, the Bi4O7 can be used as a potential candidate for the purplish blue light emitters.