Zn 1−x Mn x O (0 ≤ x ≤ 0.1) thin films were grown on sapphire substrates by pulsed laser deposition and rf magnetron sputtering methods. As a target source ceramic pellets prepared by mixing ZnO and Mn 3 O 4 powders were used. The shift of the absorption edge due to increase the energy band gap with increasing Mn content was observed in optical absorption spectra of the Zn 1−x Mn x O thin films. Magnetic susceptibility and magneto-optical Faraday rotation experiments show paramagnetic behavior and absence of ferromagnetic ordering in the studied films.
Improvement of polyvinyl alcohol stability against ultraviolet (UV) illumination is achieved by introducing cadmium sulfide (CdS) nanoparticles into the polymeric matrix. Enhancement of stability is analyzed by optical characterization methods. UV protection is achieved by diminishing the probability of photo-activated formation of defects in polymer. The sources of polymer protection are the lowering of the efficiency of polymer excitation via partial absorption of incident light by the embedded nanoparticles as well as the de-excitation of the macromolecules that have already absorbed UV quanta via energy drain to nanoparticles. Within the nanoparticles, the energy is either dissipated by conversion to the thermal energy or reemitted as visible-range photoluminescence quanta.
Participation of a polymeric media in light-emitting processes of composite nano-CdS/polyvinyl alcohol is studied by probing different absorption-emission routes via adjustment of excitation wavelengths. It is shown that the polymeric constituent of the composite contributes chiefly to the photoluminescence excitation processes via absorption and excitation transfer to the embedded CdS nanoparticles while the composite emission occurs mostly within the nanoparticles.
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