Search

Here, we show that co-activation in the Gd 3+ –Eu 3+ –Sm 3+ system can generate the intense red emission from Eu 3+ ion. Gd 2 O 3 :Sm 3+ ,Eu 3+ colloidal spheres were synthesized by combining a low temperature hydrothermal process and a higher temperature of pyrolysis. Under the excitation of 380 nm near UV light, Gd 2 O 3 :Sm 3+ ,Eu 3+ emits intense red light while the reference Gd 2 O 3 :Eu 3+ emits very weak one. The calculated polarizability α b μ based on the shift (16 nm) of Eu 3+ –O 2− charge transfer band and the crystallography analysis revealed that Sm 3+ ions codoping in Gd 2 O 3 :Eu 3+ has generated a coordinating environment of Eu 3+ ions with high polarizability and low symmetry which leads to high energy transfer rate not only between Sm 3+ and Eu 3+ pairs, but also between Eu 3+ ( S 6 ) and Eu 3+ ( C 2 ) pairs, ensuring the efficient excitation of Gd 2 O 3 :Eu 3+ ,Sm 3+ . The energy migration from Sm 3+ to Eu 3+ and a corresponding feedback were also experimentally evidenced by the fluorescent decay, which is in well agreement with the theoretical calculation. In addition, the thermal stability of the photoluminescence in Gd 2 O 3 :Eu 3+ ,Sm 3+ colloidal spheres was evaluated.

Simultaneous phase- and shape-controlled NaLuF4 microcrystals co-doped with Yb3+/Er3+ have been synthesized via a facile hydrothermal method by only changing the precursor pH value. The UC emission efficiency of these obtained microparticles showed a strong phase- and shape-dependency. Under irradiation of 980 nm, the luminescence intensity of hexagonal NaLuF4 microcrystals presents an enhancement by at least 5.8 times relative to their cubic counterpart. Specially, an up to 168-fold enhancement of emission intensity from the NaLuF4 superstructures, compared with the microplates with identical hexagonal phase, was observed. Such improvement is likely to be dominated by the laser-cavity mirrors effect from the microcavities on their surface of the NaLuF4 superstructures. These results will permit a promising step to harness the upconversion phosphors in solid state lasers.

Lanthanide-doped Ba 2 LaF 7 nanocrystals have been successfully synthesized via a modified liquid–solid-solution process. The yielded nanocrystals are determined to be pure cubic Ba 2 LaF 7 phase and consist of nearly square-shaped nanoparticles with an average 14 nm in size. The Yb 3+ /Er 3+ (Tm 3+ ) co-doped Ba 2 LaF 7 nanocrystals emit bright multicolor upconversion luminescence following the excitation of 980 nm laser diode. Proposed mechanisms for the emission were analyzed based on the emission spectra and their dependence on pumping power, as well as corresponding energy level diagram.