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Tb 3+ -and Eu 3+ -doped lanthanum oxysulfide nanocrystals (NCs) with homogeneous grain size have been prepared by a gel-network coprecipitation method using gelatin as the template and ammonium sulfate as the sulfurizing agent and a following reduction process at relatively low temperatures (750 °C) in a H 2 atmosphere. The products were characterized using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The gelatin template can act as a "nanoreactor", which is beneficial to the dispersion and size control of the coprecipitation product. The high decomposition temperature (about 482 °C) of the gelatin network is advantageous to prevent aggregation of the newly formed (LaO) 2 SO 4 NCs during calcination of the coprecipitation product. Single hexagonal phase La 2 O 2 S NCs were obtained by reduction of the (LaO) 2 SO 4 powder, and the NCs are equiaxial in shape with particle sizes ranging from 40 to 50 nm. The photoluminescence spectra and time-resolved spectra of the La 2 O 2 S:Tb(Eu) in phosphate buffer were investigated. The results show that the La 2 O 2 S:Tb NCs have a strong luminescence at 544 nm, whose intensity decreases along with decreasing particle size. Concentration quenching occurs when the Tb concentration reaches 8 mol %. The fluorescence color of the La 2 O 2 S:Eu NCs depends on the concentration of Eu 3+ ions. The red emission (at 625 nm) from 5 D 0 transition has a much longer decay time than the green emission from 5 D 1 transition of the La 2 O 2 S:Eu NCs. The Tb 3+ -and the Eu 3+ -doped La 2 O 2 S NCs have respective fluorescence lifetimes of 1.10 and 0.41 ms in phosphate buffer, allowing their potential applications in biological labeling.

High photocatalytic efficiency, easy recovery, and no biological toxicity are three key properties related to the practical application of anatase photocatalyst in water cleaning, but seem to be incompatible. Nanoparticles-constructed hierarchical anatase microspheres with high crystallinity and good dispersion prepared in this study via one-step solution processing at 90 degrees C under atmospheric pressure by using ammonium fluotitanate as the titanium source and urea as the precipitant can reconcile these three requirements. The hierarchical microspheres were found to grow via an aggregative mechanism, and contact recrystallization occurred at high additions of the FeCl(3) electrolyte into the reaction system. Simultaneous incorporation of fluorine and iron into the TiO(2) matrix was confirmed by combined analysis of X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis absorption spectroscopy. Surface structure and morphology changes of the microspheres induced by high-temperature annealing were clearly observed by field-emission scanning electron microscopy, especially for the phase-transformed particles. The original nanoparticles-constructed rough surfaces partially became smooth, resulting in a sharp drop in photocatalytic efficiency. Interestingly, iron loading has detrimental effects on the visible-light photocatalytic activity of both the as-prepared and the postannealed anatase microspheres but greatly enhances the photocatalytic activity of the as-prepared anatase microspheres under UV irradiation. No matter under UV or visible-light irradiation, the fluorine-loaded anatase microspheres and especially the postannealed ones show excellent photocatalytic performance. The underlying mechanism of fluorine and iron loading on the photocatalytic efficacy of the anatase microspheres was discussed in detail. Beyond photocatalytic applications, this kind of material is of great importance to the assembling of photoactive photonic crystal that can control light motion.

Al2O3/SiC ceramic nanocomposites were fabricated from nanocrystalline Al2O3 (10 nm in diameter) and SiC (15 nm in diameter) powders, and a theoretical model of intragranular particle residual stress strengthening was investigated. The SiC nanoparticles in the Al2O3 grains create a normal compressive stress at the grain boundaries and a tangential tensile stress in the Al2O3 grains, resulting in the “strengthening” of the grain boundaries and “weakening” of the grains. The model gives a good explanation of the experimental results of the authors and others which are difficult to be explained by the existing strengthening models, i.e. the maximum strength is normally achieved at about 5 vol% of SiC particles in the Al2O3–SiC ceramic nanocomposites. According to the model, there exists an optimum amount of SiC for strengthening, below which the grain boundaries are not fully “strengthened” and the fracture is mainly intergranular, above which the grains are “weakened” too much and the fracture is mainly transgranular, and at which the fracture is a mixture of intergranular and transgranular.