Synthesis of carbon quantum dot-surface modified P25 nanocomposites for photocatalytic degradation of p-nitrophenol and acid violet 43

Abstract

A new efficient and stable visible light driven photocatalyst, carbon quantum dots (CQDs)-surface modified P25 nanocomposite, was successfully prepared by chemical adsorption of CQDs onto the surface of TiO₂ nanoparticles and then used for water treatment. The photocatalyst was characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectrometry, thermogravimetric analysis, and UV-vis spectrometry. After the modification of titanium dioxide with carbon quantum dots, the UV-vis wavelength response range extended from 390 nm to 420 nm by accelerating the photogenerated electron transfer from carbon quantum dots to titanium dioxide, and the band gap decreased from 3.08 eV to 2.87 eV. In addition, a blue shift of binding energy was observed, namely, 0.6 eV for Ti_2p1/2 and 0.7 eV for Ti_2p3/2. Furthermore, compared with pure titanium dioxide, after irradiating for 2.5 h, the photodegradation ratio of acid violet 43 and p-nitrophenol have been enhanced from 60% to 93% and from 89% to 96%, respectively. Moreover, after five cycle times, the stability of the photocatalyst has been maintained due to the strong interaction between carbon quantum dots and titanium dioxide.