Photocatalytic effects for the TiO2-coated phosphor materials

Research highlights: → The photocatalytic behavior of the coupling of TiO2 with phosphorescent materials. → The photobleaching of an MB aqueous solution under visible light irradiation. → The ALD TiO2-coated phosphor composite showed much higher photocatalytic reactivity. → The light emitted from the phosphors contributed to the photo-generation. - Abstract: This study investigated the photocatalytic behavior of the coupling of TiO2 with phosphorescent materials. A TiO2 thin film was deposited on CaAl2O4:Eu2+,Nd3+ phosphor particles by using atomic layer deposition (ALD), and its photocatalytic reaction was investigated by the photobleaching of an aqueous solution of methylene-blue (MB) under visible light irradiation. To clarify the mechanism of the TiO2-phosphorescent materials, two different samples of TiO2-coated phosphor and TiO2-Al2O3-coated phosphor particles were prepared. The photocatalytic mechanisms of the ALD TiO2-coated phosphor powders were different from those of the pure TiO2 and TiO2-Al2O3-coated phosphor. The absorbance in a solution of the ALD TiO2-coated phosphor decreased much faster than that of pure TiO2 under visible irradiation. In addition, the ALD TiO2-coated phosphor showed moderately higher photocatalytic degradation of MB solution than the TiO2-Al2O3-coated phosphor did. The TiO2-coated phosphorescent materials were characterized by transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photon spectroscopy (XPS).