Synthesis of Sm-doped TiO2 nanotubes and analysis of their methylene blue-removal properties under dark and UV-irradiated conditions

Abstract

TiO2 nanotubes (TNTs) have received much attention over the past decade because of their unique nanostructure and physicochemical properties; in particular, TNTs can be applied in photocatalysis. In this study, degradation of methylene blue (MB) by samarium (Sm)-doped TNTs synthesized by a soft chemical process was investigated. Transmission electron microscopy revealed TNTs had diameters of approximately 10 nm and lengths of several hundreds of nanometers. MB degradation with and without ultraviolet irradiation revealed that all Sm-doped TNTs could adsorb organic molecules and were photocatalytically active. MB adsorption by Sm-doped TNT was better than by undoped TNT. Adsorption isotherm analysis showed that amounts of MB adsorbed increased on increasing the amount of Sm dopant. Introduction of Sm3+ as dopant was important for formation of oxygen vacancies in the TNTs, which enhanced molecular adsorption but did not contribute to photoreactivity because of charge state and carrier recombinations in Sm-doped TNTs. © 2012 Springer Science+Business Media B.V.