Three dimensional carbogenic dots/TiO2 nanoheterojunctions with enhanced visible light-driven photocatalytic activity

Functional carbogenic quantum dots (C-dots) were synthesized by a pyrolysis approach with strong visible light absorption and high photoluminescence. The novel three dimensional (3D) hierarchical C-dots-TiO2 (C-TiO2) heterojunctions were obtained by assembling the C-dots with end carboxylic acid groups on the surface of 3D TiO2 nanorod spheres, and confirmed by scanning electron microscopy and transmission electron microscopy analyses. The prepared C-dots show strong adsorption of rhodamine B (RhB) and very low activity in the photocatalytic degradation of RhB under visible light irradiation. The prepared 3D C-TiO2 composites show enhanced visible light absorption and higher surface area with the increase of C-dot ratios. The highest photocatalytic activity is obtained at the carbon weight percent of 3.6%, and the corresponding apparent first-order rate constant of 0.00616 min−1 which is 1.8 times of that by the pure 3D TiO2 sphere. The mechanism shows that C-dots play an important role in the donation of excited electron to the conduction band of TiO2 under visible light irradiation.