Optical Behavior of ZnS:Cu Microcrystals Embedded in Porous Silica Gels
Emission and excitation spectra of ZnS:Cu microcrystals trapped in porous silica xerogels are presented. This system is characterized by intense, long-lived green emission at room temperature. It was observed that this emission was greatly reduced after compressing the xerogel samples.
Optical centers of cerium in silica glasses obtained by the sol-gel process
Abstract A spectral-luminescent study of Ce-containing silica gel-glasses doped at the sol stage and by impregnating porous xerogels with activator chloride salt solutions has been performed. The influence of the degree of doping and redox conditions of vitrification on the activator charge state and the content of hydroxyl ions and chlorine in the glass is considered. The preservation of the glass phase composition and the non-linear increase in the visible absorption intensity with increasing activator concentration from 5 × 1017 to 3.0 × 1020 ions/cm3 are noted. It is concluded that there are two main types of optical centre. It is assumed that they represent Ce(III) oxygen complexes whose nearest surrounding includes quadruply charged (the first type) and triply charged (the second type) ions of cerium. Evidence has been obtained in favor of the superexchange excitation transfer to the central ion of Ce(III) oxygen complexes from photoreduced to the triply charged state of the same ion name of Ce(IV) oxygen complexes.
Use of laser scanning confocal microscopy for morphological taxonomy and the potential for digital type specimens (e-types)
The use of laser scanning confocal microscopy (LSCM) for creating taxonomic descriptions of copepods is investigated. A new technique is described, which employs a contour filter to process digital LSCM images, allowing taxonomic information to be quickly and accu- rately distilled into a simple illustration. LSCM allows the imaging of whole specimens, which can be rotated and viewed from any angle—a major benefit over light microscopy. Using this tech- nique, it is suggested that taxonomic descriptions can be rapidly produced in a fraction of the time required to produce similar descriptions using traditional light microscopy and hand drawing techniques. Good staining of specimens is, however, essential to produce accurate descriptions and more research is required in this area. The use of LSCM for morphological taxonomy shows great potential, not only for producing taxonomic descriptions, but also providing a comple - mentary adjunct to traditional type specimens in the form of 3D digital 'e-types' deposited in recognised international databases.