Uniform ceria nanocrystals with good crystallinity and high surface areas were prepared by a facile alcohothermal method with the addition of bases (KOH or NaOH), using Ce(III) or Ce(IV) salt as a starting material. The as-prepared nanocrystals were characterized by means of powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), nitrogen adsorption, thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and ultraviolet and visible spectroscopy (UV-vis). The ceria crystals had controllable sizes from 2.6 to 6.9 nm estimated by the PXRD line broadening analysis. TEM and HRTEM micrographs showed that the as-prepared ceria nanocrystals have a relatively high degree of crystallinity and low degree of conglomeration under high base concentrations. BET specific surface areas of the as-synthesized ceria nanocrystals were very high (103-238 m 2 g -1 ). XPS spectra indicated that the cerium in the nanocrystals was predominantly tetravalent. UV-vis spectra revealed that both the direct and indirect band gap energies of the as-prepared ceria nanocrystals showed a pronounced blue-shifting due to the quantum confinement effect compared to bulk ceria. And the dielectric confinement effect on the band gap energies was also discussed. The as-prepared ceria nanocrystals supported on γ-Al 2 O 3 exhibited a rather lower conversion temperature (559 K) for CO oxidation to CO 2 than that of bulk catalysts prepared by the coprecipitation method. Finally, a hydrolytic alcohothermal mechanism for the preparation of ceria nanocrystals was forwarded.

Pure hexagonal-phased Y 1-x BO 3 :Eu x (x ) 0-0.30) nanocrystals with different particle sizes were prepared by a facile sol-gel pyrolysis process, and their photoluminescence spectra evidently showed a size-dependent characteristic because the ratio of the red emission transition ( 5 D 0 f 7 F 2 ) to the orange emission transition ( 5 D 0 f 7 F 1 ) (R/O) was much higher in the smaller particles. Both XRD patterns and IR spectra demonstrated that the lattices of YBO 3 :Eu nanocrystals were distorted and that as the particle size became smaller, the lattices became more distorted. Studies on the charge transfer (CT) bands indicated that Eu 3+ ions can be excited preferentially by different excitation sources in both the bulk and the nanocrystals, suggesting that at least two different types of intrinsic luminescent sites, site 1 and site 2, coexist in YBO 3 :Eu. Site-selective excitation spectra also revealed that a particular site, site 3, existed concurrently in the nanocrystals. Site 2, the site with relatively inferior symmetry of the intrinsic sites, was identified to be of C 1 symmetry. Meanwhile, for the nanosized samples, Eu 3+ ions exhibited enhanced R/O values in both sites 2 and 3, which might be ascribed to the distorted lattices, and thus displayed the observed superior color chromaticity. A pronounced energy transfer between site 2 and site 3 in the nanocrystals was also observed while Eu 3+ concentration was increased to the quenching concentration, which indicated that site 3 may be a disordered surface site surrounding the interior sites.

Thermal treatment of Zn(NH3)(4)2+ precursor in ethanol solvent led to the formation of the tubular ZnO which exhibited strong ultraviolet photoluminescence around 385 nm at room temperature; TEM images showed the hollow tubules with approximately 450 nm in diameter and approximately 4 microns in length were built up by ZnO polycrystals.