C. H. Ferreira

Probing Si and Ti based sol-gel matrices by fluorescence techniques

The photophysical behavior of several probes incorporated in sol-gel–derived matrices (both monoliths and thin films) has been studied using steady-state and time-resolved fluorescence, along with fluorescence anisotropy to study the matrix structure and to elucidate probe-matrix interactions. The probes studied include laser and solvatochromic dyes along with porphyrins and phthalocyanines. It was found that spectral shifts, time-resolved decays, and quantum yields depend on the type of matrix and its preparation conditions combined with the drying time and the nature of retained solvent, which can be added to act as an anticracking agent. The differences between the results in the TiO2 matrix, where electron transfer is most probably present, and SiO2 are shown.

Medidas preventivas na gestão integrada do risco de inundação em Portugal: o planeamento participativo e o papel das comunidades locais

Na medida em que todas as obras da UC Digitalis se encontram protegidas pelo Codigo do Direito de Autor e Direitos Conexos e demais legislacao aplicavel, toda a copia, parcial ou total, deste documento, nos casos em que e legalmente admitida, devera conter ou fazer-se acompanhar por este aviso. Medidas preventivas na gestao integrada do risco de inundacao em Portugal: o planeamento participativo e o papel das comunidades locais

Optical characterization of photoactive multilayers

Abstract The optical characterization (refractive index, absorption coefficient and thickness) of organic photoactive layers for photovoltaic cells is reported. Absorption efficiencies of solar-energy conversion devices based on multilayered arrangements of organic and semiconducting oxide films have been determined, since they are a determinant factor in the overall conversion yield. The films were prepared by vacuum sublimation and magnetron sputtering techniques.