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 TiO 2 nanoclusters are investigated using density functional theory (DFT) 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 (TiO 2 ) 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 TiO 2 lms of nanocluster assemblies. Atomic force microscopy (AFM), 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 TiO 2 were estimated using XPS spectral results. The UV-Vis measurement con rmed the previously stated reasoning about the quantum size effect on the band gap of the pure and nitrogen doped TiO 2 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 signi cant advantage of interstitial over substitutional positions. N-O vibration modes appeared in interstitial doped TiO 2 , and each vibration was dependent on a different cluster structure.

Role of N Doping in the Reduction of Titania Nanostructures

“…Moreover, they investigated N-doping of Ti 9 O 18 and Ti 28 O 56 nanoclusters and found that the interstitial N formation energy is lower than that of substitutional N. Additional theoretical calculations predicted a decreasing of the band gap due to the presence of nitrogen, in agreement with results from UV–vis spectroscopy. 27 Combining the density functional theory (DFT) calculations and extended X-ray absorption fine structure (EXAFS) techniques, Ceotto et al 28 studied the nitrogen location in nanocrystalline N-doped TiO 2 and concluded that, at a low concentration of N-doping, N atoms substitute O atoms, whereas at higher N-doping concentrations, oxygen vacancies appear.…”