Three way electron transfer of a C–N–S tri doped two-phase junction of TiO2 nanoparticles for efficient visible light photocatalytic dye degradation

Abstract

C–N–S tridoped TiO₂ nanoparticles were synthesized by a sol–gel method using thiourea as a compound source of carbon (C), nitrogen (N) and sulphur (S). 15 wt% of thiourea has been used for effective dopants with different annealing temperatures (300, 400, 500 and 600 °C). X-ray diffraction results show that tridoping with C–N–S could effectively restrain the phase transformation of anatase to rutile at a higher annealing temperature (600 °C). The size–strain plot method indicates that the crystallite size decreases from 32 to 9 nm with the addition of dopants. Fourier transform infrared analysis shows that the peaks observed at 1384, 1128 and 1051 cm⁻¹ are attributed to the N–H bond, bidentate S–O coordination to Ti⁴⁺ and the Ti– O– C bond. A UV-Vis study reveals that C–N–S tridoped TiO₂ is redshifted compared to pure TiO₂. From the photoluminescence spectra the band edge emission is redshifted with different excitation wavelengths (280–320 nm). Enhancement of Rhodamine B dye degradation is observed for C–N–S tridoped TiO₂ nanoparticles (99% at 180 minutes) compared with undoped TiO₂ under visible light irradiation.