RESUMO
Luminescent Eu3+ and Er3+ doped SnO2 powders have been prepared by Sn4+ hydrolysis followed by a controlled growth reaction using a particle's surface modifier in order to avoid particles aggregation. The powders so obtained doped with up to 2 mol% rare earth ions are fully redispersable in water at pH > 8 and present the cassiterite structure. Particles size range from 3 to 10 nm as determined by Photon Correlation Spectroscopy. Rare earth ions were found to be essentially incorporated into the cassiterite structure, substituting for Sn4+, for doping concentration smaller than 0.05 mol%. For higher concentration they are also located at the particles surface. The presence of Eu3+ ions at the surface of the particles hinder their growth and has therefore allowed the preparation of new materials consisting of water redispersable powders coated with Eu(3+)-beta diketonate complexes. Enhanced UV excited photoluminescence was observed in water. SnO2 single layers with thickness up to 200 nm and multilayer coatings were spin coated on borosilicate glass substrates from the colloidal suspensions. Waveguiding properties were evaluated by the prism coupling technique. For a 0.3 microm planar waveguide single propagating mode was observed with attenuation coefficient of 3.5 dB/cm at 632.8 nm.
Assuntos
Cristalização/métodos , Medições Luminescentes/métodos , Metais Terras Raras/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Compostos de Estanho/química , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Pós , Refratometria , Propriedades de SuperfícieRESUMO
Os Fatores de Proteçäo Solar (FPS) de vários produtos comerciais brasileiros, estrangeiros e um produto padräo FDA foram determinados in vitro por duas técnicas de transmissäo ótica simples. Os produtos solares foram aplicados sobre uma nova pele artificial biológica (Biofill). Os resultados estäo de acordo com os valores FPS determinados in vivo. A técnica e o material do substrato podem conduzir a um novo protocolo padräo para a determinaçäo in vitro rápida e segura dos valores FPS dos moderadores solares
