Core/Shell ZnO/TiO[sub.2], SiO[sub.2]/TiO[sub.2], Al[sub.2]O[sub.3]/TiO[sub.2], and Al[sub.1.9]Co[sub.0.1]O[sub.3]/TiO[sub.2] Nanoparticles for the Photodecomposition of Brilliant Blue E-4BA

The synthesis and characterization of ZnO/TiO[sub.2], SiO[sub.2]/TiO[sub.2], Al[sub.2]O[sub.3]/TiO[sub.2], and Al[sub.1.9]Co[sub.0.1]O[sub.3]/TiO[sub.2] core/shell nanoparticles (NPs) is reported. The NPs were used for photocatalytic degradation of brilliant blue E-4BA under UV and visible light irradiation, monitored by high-performance liquid chromatography and UV-vis absorption spectroscopy. The size of the NPs ranged from 10 to 30 nm for the core and an additional 3 nm for the TiO[sub.2] shell. Al[sub.2]O[sub.3]/TiO[sub.2] and Al[sub.1.9]Co[sub.0.1]O[sub.3]/TiO[sub.2] showed superior degradation under UV and visible light compared to ZnO/TiO[sub.2] and SiO[sub.2]/TiO[sub.2] with complete photodecomposition of 20 ppm dye in 20 min using a 10 mg/100 mL photocatalyst. The “Co-doped” Al[sub.1.9]Co[sub.0.1]O[sub.3]/TiO[sub.2] NPs show the best performance under visible light irradiation, which is due to increased absorption in the visible range. DFT-calculated band structure calculations confirm the generation of additional electronic levels in the band gap of γ-Al[sub.2]O[sub.3] through Co[sup.3+] ions. This indicates that Co-doping enhances the generation of electron–hole pairs after visible light irradiation.