Quantum confinement effects in luminescence of rare earth (III) ions - doped semiconductor nanocrystals

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Recently quantum confinement effect has been known in various semiconductor-nanocrystals. Host dependence is investigated in luminescence of CdS and ZnS nanoparticles doped with rare earth (III) ions embedded in the porous hosts of sol-gel SiO_2 glasses and silica nanotubes MCM41. Particles of 10nm in diameter are directly observed by TEM spectroscopy. Rare earth (III) ions and complexes - doped sol-gel glasses show crystal field splitting characteristics of thermal annealing conditions. Energy transfer between Eu^<3+> and rare earth (III) ions is restricted by trap -limited energy transfer processes in SiO_2 xerogel and sol-gel glasses. CPL spectra are found to be quite useful to analyze the chiroptical structures of some optical active metal complexes in the hosts. Nanoparticles of (Zn, Cd) S:RE(III) (RE=Tb^<3+>,Eu^<3+> etc) embedded in SiO_2 and MCM41 are prepared in various conditions to measure time resolved luminescence spectra, lifetimes and their temperature dependence. In comparison to red emission of bulk crystals, yellow band luminescence due to surface defects is dominant in SiO_2:CdS glasses. Nanoparticles in MCM41/CdS:Eu^<3+> represent the presence of pico-seconds lifetime, shortening of sub-ms lifetime components in small particles, and spectral blue shifts of 0-2 transitions. Strong non-linear optimal effects due to quantum confinement effect are also found in CdS/ZnS doped-ZrO_2 thin films using Z-scan method and femto-second laser spectroscopy system.