| In this paper, there are two major sections. One is about of UV excitation properties of Eu3+ in nanocrystalline cubic Y2O3, the other is about of upconversion luminescence in nanocrystalline Lu2O3:Er. The creative works are as follows:(1) The NC Y2O3:Eu was firstly prepared by fast thermal decomposition of metal nitrate solution and could be crystallized at lower temperature than by the combustion synthesis. In the preparation, Y(NO3)3 and Eu(NO3)3 were dissolved in de-ionized water and mixed in an appropriate ratio to form the precursor solution. The precursor solution was then condensed in porcelain crucible at 90℃ and was decomposed rapidly at 500℃ followed by a heat treatment at 500℃ for 1h. The particle size was determined to be ~7 nm by transmission electron microscopy.(2) The various rare earth doped oxide nanocrystalline such as Y2O3:Eu / Y2O3:Er / Gd2O3:Eu have been firstly prepared by using template. It is shown that size of the nanocrystalline can be conveniently controlled by template method.(3) Increases of emission intensities for Eu3+ at the S6 site relative to that at the C2 site have been observed as UV excitation wavelength decreases from 300 nm to 200 nm in both bulk and nanocrystalline cubic Y2O3:Eu3+. Decomposition of excitation spectra shows that the charge transfer band of Eu3+ at the S6 site lies in the high-energy side of that at the C2 site, resulting in that the energy transfer from the host prefers to the S6 site. Detailed emission and excitation spectral characteristics have been analyzed and discussed. In addition, spectral red-shift has been found in both charge transfer bands in nanocrystalline Y2O3:Eu 3+ compared to the bulkmaterial. The number ratio of S6 sites to C2 sites is also smaller in nanocrystalline Y2O3 :Eu3+ than that in the bulk one.(4) Irradiation-induced change of charge transfer band (CTB) in nanocrystalline cubic Y2O3:Eu3+was studied. It was observed that the intensity of CTB decreased after a fixed UV irradiation for a short time , then increased after irradiation for a long time. It is noticed that the intensity of CTB at the high-energy side slightly higher than before irradiation. It was attributed to the optical activated rearrangements of local environments surrounding the Eu3+ ions in the near surface of nanoparticles.(5) We investigate as a function of erbium concentration (0.1, 0.3, 1, 2, 5, 10mol%) the upconversion properties of nanocrystalline cubic Lu2O3:Er. After excitation at upconversion pumping (980 nm), red and green emissions were observed for both nanocrystalline and bulk samples in the visible region of the spectrum. The upconverted emission after 980 nm excitation revealed an enhancement of the red [4F9/2â†'4I15/2] emission with respect to the green [(2H11/2, 4S3/2)â†' 4I15/2] emission when the dopant concentration is increased. It is explained by cross relaxation of the (2H11/2, â†'4S3/2) states.(6) Blue upconversion was only observed in bulk Lu2O3:Er, assigned to the 2H9/2 - 4I15/2 transition. It was populated via a three-photon process of two mechanisms presented by us. |
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