Metastable β-Bi(2)O(3) Nanoparticles with Potential for Photocatalytic Water Purification Using Visible Light Irradiation

Photocatalytic studies under visible light irradiation using nanosized β-Bi(2)O(3) are reported. β-Bi(2)O(3) nanoparticles are prepared starting from the well-defined bismuth oxido cluster [Bi(38)O(45)(OMc)(24)(DMSO)(9)]⋅2 DMSO⋅7 H(2)O (OMc=O(2)CC(3)H(5)) using a straightforward hydrolysis and annealing protocol. Powder X-ray diffraction studies, transmission electron microscopy, diffuse reflectance UV/Vis spectroscopy and nitrogen adsorption measurements (using the Brunauer–Emmett–Teller (BET) theory) are used for the characterization of the as-prepared β-Bi(2)O(3). By time-dependent annealing, the crystallite size can be controlled between (17±2) nm and (45±5) nm with BET surface areas of 7 to 29 m(2) g(−1). The indirect band gap of the as-prepared β-Bi(2)O(3) amounts to (2.15±0.05) eV. The decomposition rates for rhodamine B (RhB) solutions are in the range of 2.46×10(−5) to 4.01×10(−4) s(−1) and depend on the crystallite size, amount of catalyst and concentration of RhB. Photocorrosion experiments have shown the formation of Bi(2)O(2)CO(3) after several catalytic cycles. However, the catalyst can be recycled to phase-pure β-Bi(2)O(3) nanoparticles by annealing for one hour under argon atmosphere at 380 °C. Furthermore, the photocatalytic activity of as-prepared β-Bi(2)O(3) nanoparticles for the decomposition of phenol, 4-chlorophenol, 2,4-dichlorphenol, 4-nitrophenol, triclosan and ethinyl estradiol is demonstrated.