Calculation of the electronic absorption spectrum of a nanocluster (TiO₂)₁₅ doped with a nitrogen atom

At the initial stage of the formation of titanium dioxide nanoparticles, clusters of ( TiO ₂) _n are formed, which, due to their unique electronic structures, may have an increased reactivity in comparison with large nanoparticles. The quantum chemical calculation of the equilibrium geometry of clusters ( TiO ₂)₁₅ and Ti ₁₅ O ₂₉ N ₁ of the rutile modification was performed using the density functional theory methods. Using the nonstationary density functional theory in the TD DFT/B3LYP/6-31G(d) approximation, the electronic absorption spectra of clusters in vacuum and aqueous medium are calculated. The Ti ₁₅ O ₂₉ N ₁ cluster doped with a nitrogen atom is characterized by the presence of absorption bands with wavelengths mainly in the visible region of the spectrum (430-780 nm) and a significant decrease in the E_gap energy gap between the lower vacant and higher occupied molecular orbitals in comparison with ( TiO ₂)₁₅. The influence of the position of the nitrogen atom in the central TiO ₆ fragment of the Ti ₁₅ O ₂₉ N ₁ cluster on the E_gap value, the shift of the electronic absorption spectrum and the maximum strength of the f_{maxoscillator among 30 electronic transitions is shown. It has been found that when taking into account the aquatic environment, the positions of the absorption bands in the electronic spectra shift to the region of shorter wavelengths. For transitions with the highest oscillator strength, the presence of an aqueous medium leads to a significant increase in the fmax value.}

cluster, titanium dioxide, density functional theory, energy gap, electronic absorption spectrum