Theoretical and experimental investigation of the electronic and optical properties of pure and interstitial nitrogen -doped (TiO2)n cluster

Abstract

The structural and electronic properties of pure and nitrogen-doped TiO2 nanoclusters are investigated using density functional theory with vibrational modes. We performed numerical simulation using two methods based on theories at the Quantum Espresso/PBE and Gaussian/B3LYP/631G (d) levels. The properties of a single nitrogen-doped (TiO2)n nanocluster are also computed in this study. In both cases, interstitial and substitutional Nitrogen doping at all accessible sites was examined. For the experiment, Supersonic Cluster Beam Deposition (SCBD) was used to create pure and nitrogen-doped TiO2 films of nanocluster assemblies. Atomic force microscopy, X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and Raman techniques were used to characterize these samples. The binding energies (Np, O2s, Ti 2p1/2, and Ti 2p3/2) of N-doped TiO2 were estimated using XPS spectral results. The UV–Vis measurement confirmed the previously stated reasoning about the quantum size effect on the band gap of the pure and nitrogen doped TiO2 nanocluster. The theoretical vibrational modes frequencies are calculated using the B3LYP/6-31G (d) functional via the Gaussian16 code's implementation algorithm. The good agreement between simulation and experimental results implies that a significant advantage of interstitial over substitutional positions. N–O vibration modes appeared in interstitial doped TiO2, and each vibration was dependent on a different cluster structure.