▎ 摘　　要

Industrial pollutants are one of the many contributing factors towards deterioration of nature, urging the scientific community around the globe to look for ways in which they can be eliminated. In this regard, we have developed and optimized an efficient photocatalytic system comprising of liquid exfoliated graphene quantum dots (GQDs) and TiO2, by carrying out a thorough study with different morphologies of TiO2; namely, nanotubes, nanorods and nanoparticles. The nanocomposites were duly characterized using various techniques such as FT-IR, TGA, FESEM, UV-vis spectroscopy etc. Among the as-prepared range of nanocomposites, the photocatalyst containing 2 wt% of GQDs and TiO2 nanotubes was found to exhibit a higher degradation efficiency of 96.7 % towards methylene blue (MB) under visible light irradiation of 120 min. Further, we have also repeated the photocatalytic study of this nanocomposite up to four cycles to understand the reusability of the photocatalyst. Band gap of GQDs, pristine TiO2 and the nanocomposite determined from Tauc plot was found to be 2.26, 2.92 and 2.86 eV respectively. We also underline that the "metal-free" GQDs, synthesized via our approach, play the role of a photosensitizer by providing an edge of extending the visible light absorption in the case of nanocomposites via enhanced electron-hole (e-h) separation and lowering of band gap.