Fabrication of flower-shaped Bi2O3 superstructure by a facile template-free process

► A novel flower-shaped Bi2O3 superstructure has been successfully synthesized by calcination of the precursor, which was prepared via a citric acid assisted hydrothermal process. ► Key factors for the formation of the Bi2O3 superstructures have been proposed; a mechanism for the growth of the superstructure has been presented based on the FESEM investigation of different growth stages.