Host dependent frequency upconversion of Yb3+/Tm3+-codoped oxyfluoride tellurite glasses

The upconversion luminescence properties of Yb3+/Tm3+-codoped oxyfluoride tellurite glasses under 980 nm excitation are investigated experimentally. The intense blue and relatively weak red emissions centered at 475 and 649 nm corresponding to the transitions (1)G(4) -> H-3(6) and (1)G(4) -> H-3(4) of Tm3+, respectively, are simultaneously observed at room temperature. The effect of PbF2 on upconversion intensity is observed and discussed, and possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Yb3+/Tm3+-codoped oxyfluoride tellurite glasses may be a potentially useful material for developing blue upconversion optical devices. (c) 2005 Elsevier B.V. All rights reserved.

Perfectly Hydrophobic Silicone Nanofiber Coatings: Preparation from Methyltrialkoxysilanes and Use as Water-Collecting Substrate

Perfectly hydrophobic (PHO) coatings consisting of silicone nanofibers have been obtained via a solution process using methyltrialkoxysilanes as precursors. On the basis of thermal gravimetry and differential thermal analysis (TG-DTA) and Fourier transform infrared spectroscopy (FTIR) results, the formula of the nanofibers was tentatively given and a possible growth mechanism of the nanofibers was proposed. Because of the low affinity between the coatings and the small water droplet, when using these coatings as substrate for collecting water vapor, the harvesting efficiency could be enhanced as compared with those from bare glass substrate for more than 50% under 25 degrees C and 60-90% relative humidity. By removing the surface methyl group by heat treatment or ultraviolet (UV) irradiation, the as-prepared perfectly hydrophobic surface can be converted into a superhydrophilic surface.