Abstract

In this study, the structure and electronic characteristics of nitrogen-doped
anatase TiO 2 , TiO 2 (101) surface, nanocrystal, and nanocluster were investigated
using first-principles computations. Also, the influence of impurity location on
TiO 2 electronic properties was studied, which affects photocatalytic properties.
Firstly, the electronics properties of the nitrogen-doped anatase TiO 2 of the pure
host lattice are compared. The ab initio calculations were performed by using the
QuantumEspresso package. The fully optimized structure and the relaxation
introduced by the impurity were obtained by minimizing the total energy. The band
structure, the energy gap, and the density of states have been explored. GGA/PBE
in Quantum espresso was used to do calculations of the structural and electronic
structure of nitrogen-doped TiO 2 anatase as a function of dopant depth below the
(101) surface. The depth dependence of the formation energy for a few N impurity
positions was investigated, taking into account both substitutional and interstitial
sites. Asignificant advantage of interstitial positions over substitutional positions
and a mild dependence of this formation energy on depth were observed.
The length of the bonds surrounding the N-impurity also evolve smoothly with
the depth. The essential properties of the intra gap impurity states and the hole-
related spin magnetization density surrounding the N impurity are reported in
terms of electronic structure. For nanocrystals (TiO 2 ) 33 , the position of impurity
function of facets, the formation energy (E f ) of the impurity at different facets of
nanocrystals at different nitrogen concentrations for substitutional sites have been
calculated.
The formation energy of the N-doped (TiO 2 ) 33 nanocrystal at (101) facet was
low at both low (Ti 33 O 65 N 1 ) and high (Ti 33 O 64 N 2 ) concentrations. Similarly, at low
and high concentrations, the lengths of the bonds surrounding the impurity (N)

dopant varied with the different facets. Regarding the electronic properties,
different locations of nitrogen impurity in various facets have distinctly different
electronic structures. This study observed that N-doped (TiO 2 ) 33 nanocrystals
exhibit various structural and electronic properties depending on the dopant facets.
Because of these properties, the material is selectively suitable for a wide range of
purposes and applications. Finally , The electronic and optical properties of pure
and nitrogen-doped (TiO 2 ) n nanocluster were studied theoretically
and experimentally. The structural and electronic properties of pure and nitrogen-
doped TiO 2 clusters are investigated using density functional theory (DFT) with
vibration modes. We obtained the characterization using two methods based on
theories at the QuantumEspresso/PBE and Gaussian/B3LYP/6-31G(d) levels. The
properties of a single nitrogen-doped (TiO 2 ) n nanocluster were also computed in
this study. In both cases, interstitial and substitution dopings, all accessible
nitrogen at various sites was examined. Furthermore, Supersonic Cluster Beam
Deposition (SCBD) was used to create pure and nitrogen-doped TiO 2 nanoclusters.
Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-
Vis, and Raman techniques were used to characterize these nanoclusters. The
binding energies (Np, O2s, Ti 2p1/2, and Ti 2p3/2) of N-doped TiO 2 were
estimated by 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 TiO 2 cluster. The theoretical vibrational modes were
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 interstitial is more likely than substitutional. N-O
vibration modes appeared in interstitial doped TiO 2 , and each vibration was
dependent on a different cluster structure.