Abstract
It is known that titanium dioxide as photocatalyst has significant drawback - limited absorption spectrum in the ultraviolet region makes it impossible to use solar energy. To expands the absorption spectrum of TiO2, the doping of impurities (metal, non-metal, etc.) were used. They affected the electronic structure and spectral characteristics of TiO2. The aim of our work was to investigate the influence of tin impurities on spectral characteristics of titanium dioxide using experimental and theoretical methods. The TiO2 powders modified by different amount of tin (Sn/TiO2) were synthesized by sol-gel method. The samples were characterized by SEM, EDX, FT-IR and UV-VIS spectroscopy. It has been found that Sn/TiO2 consists of fragmented agglomerates in the range of 5–10 mm. EDX spectroscopy prove that powders include Ti, O and Sn elements. Modification of titanium dioxide with tin leads to band gap narrowing of samples, which explains by insertion of Sn atoms into crystal lattice of titanium dioxide, because Ti4+ and Sn4+ ions radii are close. The band gap values increased with increasing of tin content. The work also analyzes the vibrational spectra of Sn/TiO2 both experimentally and theoretically. In order to interpret the results obtained, quantum chemical calculations on the spatial and electronic structures of cluster models of titanium dioxide (anatase) with inserted tin atoms using the density functional theory B3LYP method and the basis set 6-31G (d, p) were carried out and the corresponding FT-IR spectra have been simulated. By comparing the experimental and theoretical results, the influence has been analyzed of the number and arrangement of impurity tin atoms in clusters on the observed IR spectra of the samples. This makes it possible to forgive the most probable structural motives of titanium dioxide particles doped with tin atoms, as well as to establish the fact of the presence of tin atoms in the samples. Based on the comparison of the IR spectra of samples with different numbers of tin atoms, it is possible to quantify their composition.
Highlights
The goal problem of increasing the efficiency of photoactive materials, such as titanium dioxide, is the expansion of the spectral range of their sensitivity
One of the main ways to expand the spectral region of sensitivity of titanium dioxide and other photoactive solids to the long-wavelength region of the spectrum is considered to be due to their doping with another elements impurities [1,2,3]
Earlier we examined the effect of carbon and sulfur on the electronic structure and spectral characteristics of titania nanoparticles both experimentally [5] and theoretically [6]
Summary
The goal problem of increasing the efficiency of photoactive materials, such as titanium dioxide, is the expansion of the spectral range of their sensitivity. One of the main ways to expand the spectral region of sensitivity of titanium dioxide and other photoactive solids to the long-wavelength region of the spectrum is considered to be due to their doping with another elements impurities [1,2,3]. It was shown [4] that the introduction of impurities of various nature, including metal ions, leads to the appearance of stable absorption bands adjacent to the fundamental absorption edge of TiO2 and extending up to the IR absorption range Room temperature FT-IR spectra were recorded with a Perkin Elmer Spectrum One spectrometer in the spectral region of 4000–400 cm–1 with spectral resolution of 4 cm–1
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