Photodegradation of rhodamine B in aqueous solution via SiO2@TiO2 nano-spheres

Titania coated silica spheres (SiO2@TiO2) prepared by heterocoagulation of silica and titania nano-particles were investigated as catalyst in the photodegradation of rhodamine B (RB) in aqueous solution. The silica spheres were prepared by the well-known Stöber method and titania sol by a hydrolysis–condensation reaction in acidic media. The uncoated and coated particles were characterized by zeta potential measurements, acoustic attenuation spectroscopy and scanning electron microscopy. The degradation of the dye was induced by illuminating the coated spheres in aqueous solution with artificial solar light. The spectral distribution of the applied light corresponds to the sunlight spectrum on the earth's surface. Rhodamine B was used as model dye and decomposed completely to colourless end products after illumination. The decrease in concentration of rhodamine B was monitored by UV–vis spectroscopy and the total organic carbon (TOC) was determined in order to verify the degradation mechanism described elsewhere.