Structure and Photoluminescent Properties of ZnO Encapsulated in Mesoporous Silica SBA-15 Fabricated by Two-Solvent Strategy

The two-solvent method was employed to prepare ZnO encapsulated in mesoporous silica (ZnO/SBA-15). The prepared ZnO/SBA-15 samples have been studied by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm, and photoluminescence spectroscopy. The ZnO/SBA-15 nanocomposite has the ordered hexagonal mesostructure of SBA-15. ZnO clusters of a high loading are distributed in the channels of SBA-15. Photoluminescence spectra show the UV emission band around 368 nm, the violet emission around 420 nm, and the blue emission around 457 nm. The UV emission is attributed to band-edge emission of ZnO. The violet emission results from the oxygen vacancies on the ZnO–SiO2interface traps. The blue emission is from the oxygen vacancies or interstitial zinc ions of ZnO. The UV emission and blue emission show a blue-shift phenomenon due to quantum-confinement-induced energy gap enhancement of ZnO clusters. The ZnO clusters encapsulated in SBA-15 can be used as light-emitting diodes and ultraviolet nanolasers

An effective geometrical approach to the structure of colloidal suspensions of very anisometric particles

International audienceWe show in the present letter that the organization of colloidal suspensions of very anisometric repulsive particles can be understood on the basis of simple geometrical considerations. Using a large set of rod-like and plate-like particles, we first evidence that the experimental inter-particle distances can be accurately predicted from geometrical constraints. We then show that the experimental static structure factors can be satisfactorily fitted using an effective Percus-Yevick structure factor. The fit parameters are then interpreted in terms of the co-excluded volumes of effective ghost particles, which further supports the geometrical representation previously developed

A merit synthesis of well-ordered two-dimensional mesoporous niobium silicate materials with enhanced hydrothermal stability and catalytic activity

10.1021/jp811334rJournal of Physical Chemistry C113187743-774