Papers by Author: Tomas Strachowski

Abstract: Nanoparticles of wide band gap II-VI compounds doped with transition metal (TM) or rare earth (RE) ions are perspective phosphor materials and fluorescence labels for optoelectronic, biology and medical applications. The efficiency of 3d-3d and 4f-4f intra-shell transitions is shown to be enhanced in TM, RE doped nanoparticles. Two mechanisms of emission enhancement related to spin dependent interactions of free carriers with impurities are discussed. These interactions enhance the TM, RE intra-shell transitions by increasing the rate of host to impurity energy transfer. It is shown also that Al doping increases the intensity of light emission from ZnO nanoparticles.

Abstract: Time-resolved luminescence and Furje Transformation Infrared (FTIR) absorption spectroscopy for ZnO nanocrystals prepared under different chemical reactions using microwave driven hydrothermal process was studied. OH- group stretching vibration frequency is considerably different in nanocrystals studied and in single ZnO crystal. It is shown that fractions of chemicals used in synthesis process could be found in nanopowders. Luminescence at ~2.0 eV (due to defect states in ZnO crystals and nanopowders) was suppressed in nanopowders obtained by urea method.