Fabrication of porous beta-Bi2O3 nanoplates by phase transformation of bismuth precursor via low-temperature thermal decomposition process and their enhanced photocatalytic activity

Direct phase transformation of bismuth complex nanoplates to beta-Bi2O3 ones was induced by low-temperature annealing at 250 degrees C. The beta-Bi2O3 nanoplates showed a nanoporous structure, which retained the tetragonal framework of the original bismuth complex nanoplates while releasing gas molecules produced during thermal decomposition, thereby enabling the formation of nanoporous structures extending through the nanoplate surfaces. The sizes, structures, optical properties, and composition distributions of the synthesized bismuth-organic complex and porous beta-Bi2O3 nanoplates were characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy, infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, and x-ray diffraction. The porous beta-Bi2O3 nanoplates prepared by low-temperature annealing at 250 degrees C for 3, 5, and 7 h showed photocatalytic activities for the photodegradation of methylene blue. The porous beta-Bi2O3 nanoplates annealed for 7 h showed the best photocatalytic activity. To confirm the nanoplate photocatalyst cytotoxicity, cell viability tests were performed by treating HEK293 normal kidney cells with the porous beta-Bi2O3 nanoplates.