Effects of annealing temperature on the crystal structure, optical and photocatalytic properties of Bi2O3 needles

•α-Bi2O3 needles were successfully synthesized via a co-precipitation method.•ESR, XPS and PL results confirmed the presence of oxygen vacancies within the crystal structure.•Green and red emissions were observed in the PL spectra.•The oxygen vacancies increased with an increase in annealing temperature.•Catalytic oxidation of RhB dye occurred by using the α-Bi2O3 in the presence of UV–Vis light.