Facile preparation of YAG:Ce nanoparticles by laser irradiation in water and their optical properties.

Yttrium aluminum oxide Y3Al5O12 (YAG:Ce) nanoparticles were prepared by laser ablation in liquid, and the photoluminescence (PL) properties of the nanoparticles were investigated. A pellet of YAG:Ce synthesized by co-precipitation in deionized water was irradiated with a focused laser beam to obtain a solution containing dispersed nanoparticles. The compositions and morphologies of the nanoparticles were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, and dynamic light scattering. PL and photoluminescence excitation (PLE) spectra at room temperature and low temperature were measured using a fluorescence spectrophotometer. Nanoparticles of YAG single phase as a matrix were obtained by irradiation at high laser energy density. The average particle size was approximately 9 nm, although the nanoparticles were slightly aggregated. The broad peak centered at 540 nm in the PL spectrum was asymmetrically broadened at shorter wavelength. The intensity of the PLE peak centered at 340 nm decreased with increasing energy density of the laser beam. These phenomena were related to the nanosize effect of the YAG:Ce phosphor.

Facile and Chemically Pure Preparation of YVO4:Eu(3+) Colloid with Novel Nanostructure via Laser Ablation in Water.

A YVO4:Eu(3+) colloid with an interesting nanostructure was formed by pulsed laser ablation in deionized water without any additives or surfactants. Analyses of particle morphology, composition and optical properties were accomplished by SEM, TEM, EDS PL and UV-vis. Ovoid-like particles formed by the agglomeration of numerous nanocrystals were observed by SEM and TEM, while EDS with area-mode analysis revealed that the content of dopant ion was well retained within the nanoparticles. In addition, the formation mechanism is deduced and discussed for the first time in this research. The findings of this study could provide new insights into the understanding of laser-induced oxide materials and offer an opportunity for other research groups to pursue red emitting nanophosphors with outstandingly purity.

Optical Properties of ZnO Nanoparticles Capped with Polymers.

Optical properties of ZnO nanoparticles capped with polymers were investigated. Polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) were used as capping reagents. ZnO nanoparticles were synthesized by the sol-gel method. Fluorescence and absorption spectra were measured. When we varied the timing of the addition of the polymer to the ZnO nanoparticle solution, the optical properties were drastically changed. When PEG was added to the solution before the synthesis of ZnO nanoparticles, the fluorescence intensity increased. At the same time, the total particle size increased, which indicated that PEG molecules had capped the ZnO nanoparticles. The capping led to surface passivation, which increased fluorescence intensity. However, when PEG was added to the solution after the synthesis of ZnO nanoparticles, the fluorescence and particle size did not change. When PVP was added to the solution before the synthesis of ZnO nanoparticles, aggregation of nanoparticles occurred. When PVP was added to the solution after the synthesis of ZnO nanoparticles, fluorescence and particle size increased. This improvement of optical properties is advantageous to the practical usage of ZnO nanoparticles, such as bioimaging.

Improvement of protein crystal quality by forced flow solution.

Flow experiments in growing protein crystals were conducted to clarify the influence of the solution flow on the crystal quality. Lysozyme crystals grown under various flow velocities were analyzed by using synchrotron radiation to assess the quality. As a result, the crystals grown under forced flow were of better quality than those grown in quiescent conditions.