First Principles Study on the Electronic Structure and Optical Properties of NCQDs/TiO2(101)

First-principles calculations based on density functional theory (DFT) were employed to investigate the binding energy, work function, electronic structure, and optical properties of carbon quantum dots (CQDs) and nitrogen-doped carbon quantum dots (NCQDs) loaded on the TiO2(101) surface. The results indicate that NCQDs exhibit stronger binding affinity to the TiO2(101) surface than CQDs. The charge transferred from CQDs to the TiO2(101) surface mainly originates from the carbon atoms located at the two ends along the a-axis of the CQDs. By contrast, the charge distribution between NCQDs and TiO2(101) is more uniform, with the Bader charges of the carbon atoms at the two ends along the a-axis in NCQDs being reduced to varying degrees compared to those in CQDs. Moreover, loading NCQDs is more favorable for the generation of photogenerated electron-hole pairs and electron transfer, whereas loading CQDs leads to the smallest band gap.