The quenching of the PL is connected with the oxygen vacancies in the TMO structure, in particular, the intensity lowering for the near band edge emission at 3.06 eV (405 nm) and the free exciton emission at 2.92 eV (424 nm) is interpreted by the non-radiative Auger recombination. Examination of PL spectra revealed that they are strongly dependent on the phase composition and Mn concentration in TMO compounds. All measurements were carried out at room temperature. The photo-luminescence (PL) in TMO was excited by the UV laser pulses (337.1 nm). The morphology, structural and optical properties of TMO samples were investigated using standard XRD, SEM, EDS, XRF, TGA, FT-Raman and UV–vis absorption spectroscopic techniques. Titanium-manganese mixed oxides TiO2 /MnOx (TMO) were prepared by chemical precipitation of manganese hydroxide on pure nanocrystalline rutile TiO2 particles with subsequent thermal treatment at different temperatures. An increased number of surface defects in A/PTZ can essentially increase the nonradiative charge recombination, and therefore may considerably enhance the photoactivity of the dark-blue TiO2 in the visible range of the spectrum. The photoluminescence spectra show that the photo-luminescence originating from Ti3+ and states for A/PTZ is stronger than for A-TiO2, but the excitonic photoluminescence of A/PTZ is quenched. The doping of A-TiO2 with PTZ causes a noticeable redshift of the absorption edge and a significant narrowing of the band gap by 0.24 and 0.49 eV for direct and indirect electronic transitions, respectively. The UV-vis absorption spectrum of A/PTZ exhibited an increase in absorption in the visible region (> 400 nm). + radical cations and reduced Ti3+ species as well as extra oxygen vacancies (VO) in the TiO2 matrix.The appearance of new bands in the Fourier transform IR spectrum indicated the formation of PTZ We found that the mixing and interaction of PTZ and A-TiO2 leads to the intense dark-blue color of PTZ-doped A-TiO2 (A/PTZ). We studied the effect of the phenothiazine (PTZ) surface doping on the structural and optical properties of nanocrystalline titanium dioxide powder with a single anatase phase (A-TiO2). The influence of TiO2 crystal structure and calcination temperature of the samples on the PL spectra and optical absorbtion is discussed. PL bands at 3.03 eV and 3.26 eV, attributed to the emission of free excitons near the fundamental absorption edge of rutile and anatase, respectively. PL bands within 3.0-3.3 eV attributed to indirect and direct allowed transitions due to electron-hole recombination. The exciton peak at 2.91 eV is attributed to the recombination of self-trapped excitons in anatase or to the free exciton in rutile, respectively. PL bands, including the peaks at 2.71-2.81 eV in the anatase and rutile arise due to exciton recombination in the TiO2 lattice oxygen vacancies. It is concluded that the processes of absorption and emission of light near the edge of the forbidden zone occur with the participation of the same electronic transitions. For the first time for nanocrystalline TiO2 a features in the high-resolution PL spectra, including the exciton band and interband transitions were registered. PL was studied at room temperature when excited by intense UV (3.68 eV) by a nitrogen laser. Nanocrystalline TiO2 samples were synthesized in the form of pure anatase or rutile and studied by X-ray diffraction, X-ray fluorescence, Raman spectroscopy, optical absorption and photoluminescence (PL). The optical absorption and photoluminescence of nanocrystalline TiO2 samples of anatase and rutile were investigated at room temperature.
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