Blue or red photoluminescence emission in α-Bi2O3 needles: Effect of synthesis method

Monoclinic bismuth oxide (α-Bi2O3) has attractive optical properties and, therefore, its photoluminescence (PL) behavior has been increasingly explored. Besides this fact, the influence of synthesis methods on PL properties of α-Bi2O3 still requires research. This paper describes the influence of precipitation (PPT) and microwave-assisted hydrothermal (MAH) methods on PL properties of acicular α-Bi2O3 microcrystals. The synthesis method promoted structural modifications on α-Bi2O3, in particular PPT increased the density of oxygen vacancies significantly. As a result, the PL properties of samples were different depending on the method of synthesis. PPT samples presented their maximum PL emission at 1.91 eV (red), while MAH samples had their maximum at 2.61 eV (blue). These results indicate the possibility of controlling PL properties of α-Bi2O3 by simply choosing the adequate synthesis method.