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In this work, the influence of oxygen partial pressure on structural, morphological, and optical properties of TiO2 thin films grown on fused quartz substrate at different oxygen partial pressure by pulsed laser deposition were examined. X-Ray diffraction (XRD) patterns show the formation of TiO2 anatase phase deposited at high oxygen pressure. Atomic Force Microscopy (AFM) reveals that surface roughness of the films increases with oxygen pressure. Variation of surface morphology of films with increasing oxygen partial pressure was studied by AFM. It is observed that energy band gap of the films increases from 3.27 eV to 3.52 eV with the increase of oxygen pressure and is attributed to the decrease of oxygen defects. TiO2 thin films exhibited blue emission under the excitation of 320 nm wavelength. De-convoluted photoluminescence (PL) peaks showed that defect states are responsible for visible emission in TiO2 thin films. The intensity of PL emission associated with oxygen vacancies decreases with increasing oxygen pressure. Photometric characteristic analysis shows that the films deposited 1x10-4 mbar oxygen pressure exhibited intense blue emission with high luminescence efficacy of radiation. [ABSTRACT FROM AUTHOR]

TiO2:Dy3+ powders without any secondary phases have been prepared by solid-state reaction through the optimization of synthesis conditions, doping amount and subsequently through a purification step. The maximum dysprosium solubility was found at 0.43 mol% in the range 800-900°C. The Rietveld refinement was performed to calculate the amount of phases and lattice constants. The effect of synthesis conditions and doping on strain and crystallite size is also discussed. Room temperature photoluminescence of TiO2:Dy3+ shows blue and yellow color emission. It is shown that yellow emission can be enhanced with the reduction of the pyrochlore phase Dy2Ti2O7. [ABSTRACT FROM AUTHOR]

The incorporation of CdS nanoparticles (NPs), as prepared through colloidal methods using reverse micelles, within diureasil hybrid organic–inorganic sol–gel matrices was investigated. Several experimental conditions, namely the influence of capping agent 3-mercaptopropyltrimethoxysilane (MPTMS) or the use of tetraethoxysilane (TEOS), were studied in order to assure the preservation of the original optical properties of colloidal CdS NPs after the incorporation of the NPs within the solid diureasil hybrid matrix. The diureasil matrix is based on a siliceous network cross linked through urea bonds to poly(oxyethylene)/poly(oxypropylene) (PEO/PPO) chains. The influence of the Cd 2+ /S 2− molar ratio of the NPs in the stability and dispersion of the NPs within the diureasil matrix was also investigated. The obtained CdS doped hybrid matrix was characterized by absorption, steady-state and time-resolved photoluminescence (PL) spectroscopy and by transmission electron microscopy (TEM). The stability of the CdS NPs within the hybrid matrix showed to be dependent on the Cd 2+ /S 2− molar ratio used in the synthesis of the NPs. The use of MPTMS proved to be crucial in the preservation of the original optical properties of the colloidal CdS NPs after the incorporation of the NPs within the hybrid matrix. The effect of MPTMS was in turn influenced by the Cd 2+ /S 2− molar ratio employed in the synthesis of the CdS NPs. The use of MPTMS was less effective when Cd 2+ /S 2− molar ratio equal to 0.5 was used. In the absence of MPTMS or TEOS larger NPs size distribution and clustering of the CdS NPs were obtained after the transfer of the NPs into the hybrid matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] In situ synthesis of CdSe nanoparticles within a hybrid ureasilicate matrix. [•] Influence of Cd/MPTMS and Cd/Se molar ratios in optical properties of nanocomposites. [•] Absorption and PL spectra of doped xerogels show features of quantum size effect. [•] PL decay profiles of doped xerogels showed to be dependent on the Cd/Se molar ratio. [ABSTRACT FROM AUTHOR]