Weihua Di

Size-dependent excitation spectra and energy transfer in Tb3+-doped Y2O3 nanocrystalline

Nanocrystal Y2O3 powders with different grain sizes and various doping concentrations of Tb3+ were prepared by an autocombustion reaction. The size and surface effects on the 4f-5d transitions and energy transfers between Tb3+ ions were studied by using x-ray diffraction, transmission electron microscopy, fluorescent spectra, and luminescent decay. It was found that the excitation spectra are composed of two parts: one is the contribution from the Tb3+ at/near the nanoparticle surfaces; another is from the Tb3+ inside the nanoparticles. The study on the concentration quenching and luminescent decay indicated that the energy transfers depopulating the D53 and D54 level were assigned to the mechanisms of electric dipole-dipole and exchange interaction, respectively. The size confinement greatly affects the energy transfer quenching the emission from the D53 level, but slightly affects the energy transfer quenching the emission from the D54 level.

Nanocrystalline CePO4:Tb as a novel oxygen sensing material on the basis of its redox responsive reversible luminescence

This work reports for the first time on a new finding of luminescent CePO(4):Tb nanocrystals providing a novel oxygen sensing material on the basis of the redox responsive reversible luminescence in an oxidizing/reducing atmosphere. The origin of the luminescence quenching/recovery of nanocrystalline CePO(4):Tb was clearly demonstrated, from the surface chemistry of nanocrystals and the fluorescence decay dynamics of Tb(III). Our present work represents a preliminary demonstration of the feasibility of using nanocrystalline CePO(4):Tb as a novel oxygen sensing material since it yields several advantages including surfactant-free synthesis, dual detection functioning, rapid response, high sensitivity and good reproducibility.

Experimental demonstration of the relationship between the OH− content and photoluminescence in Tb-doped YPO4∙2H2O

Tb-doped YPO4∙2H2O was synthesized via a simple wet-chemical route. Both the crystallinity of samples and the concentration of OH− adsorbed at the surface were experimentally controlled by adjusting the reaction time. An abnormal phenomenon that photoluminescence efficiency decreases with the increase of crystallinity demonstrates enormously adverse effect of OH− on photoluminescence, especially, as the OH− content reaches a critical value, the luminescent efficiency decreases more drastically. This strong dependence of photoluminescence on the OH− content indicates that to control the OH− content in a limited range or to reduce the OH− effect as much as possible is an efficient way to improve photoluminescence efficiency.

A facile template-free route to fabricate highly luminescent mesoporous gadolinium oxides

This work first demonstrates a simple template-free approach for the preparation of nanoporous rare earth oxides with well-defined mesopores, large pore size and specific surface area, and high photoluminescence quantum yield.

Fluorescence lifetime and quantum efficiency of Y2O3:Eu nanocrystals

Bulk Y2O3: Eu (1% in molar ratio) powders and nanocrystals with different particle size were prepared by chemical self-combustion, all of them exhibits cubic structure. Fluorescent decay curves at room temperature and 10k, excitation and emission spectra were measured. The dependence of fluorescence lifetime on the particle size and temperature were discussed. Meanwhile, the quantum efficiency of 5D0 level of europium ion occupying C2 site was estimated.