Estudo teórico-experimental das propriedades ópticas estruturais de nanocristais de dióxido de titânio puros e dopados com íons de manganês

Abstract

Titanium dioxide (TiO2) is a semiconductor that presents absorption and emission in the ultraviolet region, photostability, catalytic and osseointegrating properties that allow its use in various technological and medical applications, such as catalysts, photovoltaic devices and osseointegrating agents. The incorporation of transition metal ions (MT) in semiconductors generates magneto-optical properties that can be tuned as a function of the dopant concentration. Few works in the literature study the structural and optical properties of MT-doped TiO2. Therefore, in order to understand how the physical and chemical properties can be influenced as a function of the dopant concentration, in this work we synthesized and characterized nanocrystals (NCs) of TiO2 doped with increasing concentrations of manganese ions (Mn2+) by the method of chemical precipitation. Structural properties were investigated using X-Ray Diffraction (XRD) and Raman Spectroscopy. Optical properties were investigated using Optical Absorption Spectroscopy (AO) and application of the Crystal Field Theory (CCT) model. In the XRD and Raman spectra diffraction patterns, the XRD diffraction patterns and the bands corresponding to the characteristic vibrational modes of TiO2 NCs in the anatase phase were observed, respectively, not being altered with the doping concentration. In the AO spectra, the absorption band characteristic of TiO2 NCs was observed and that with increasing doping there was a red shift, which is related to the strong sp-d exchange interaction, confirming the incorporation of Mn2+ ions in the NCs. of TiO2. In the application of TCC and with the aid of Tanabe-Sugano diagrams, it was shown that Mn2+ ions were substituted for those of Ti4+ in tetrahedral and octahedral sites of TiO2 nanocrystals, depending on the doping concentration. Therefore, based on these results, the successful growth of pure and Mn2+-doped TiO2 NCs in the anatase phase was confirmed and that, depending on the concentration, it is possible to tune the site where the Mn2+ ions are, strongly altering the optical properties.