Photochemical quenching of aqueous methylene blue by N, Nb co-doped TiO₂nanomaterials under visible light: a confirmatory UV/LC-MS study

Nanodimensional un-doped, Nb doped, N doped and N,Nb co-doped TiO 2 particles have been prepared by the sol-gel procedure. Phase identification of the anatase particles was done by X-ray powder diffraction and Deby–Scherrer calculations revealed their particle sizes to range from 20 to 30 nm. The band gap energies of the samples were measured by UV–Vis-diffuse reflectance (UV-DRS) spectra. While un-doped TiO 2 showed wide optical absorption in the UV region. The co-doped TiO 2 particles exhibited narrow band gaps of ~2.7 eV, which showed absorption in the visible region. A decline in charge carrier recombination rates in the prepared samples was confirmed through photoluminescence (PL). The morphological appearances of the particles have been examined by scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) of the samples confirmed the incorporations of N and Nb into the TiO 2 matrices. The photocatalytic efficiencies of the prepared particles have been determined by the degradation of the non-biodegradable dye methylene blue (MB) under electromagnetic radiation. The co-doped sample showed superior photocatalytic activity under the visible light ( λ > 400) over the other samples. Photochemical quenching of aqueous MB was further analysed by UV/LC-MS which confirmed the attenuation of methylene blue.