Preparación y caracterización de materiales mesoestructurados

Resum

Mesoporous materials, such as colloidal crystals, have been prepared by arrangement of silica (0.5 ¿m) and polystyrene particles (1 ¿m). Three methods were studied. First, it is described the electrophoresis method. A vertical electrical field, applied to an ITO coated glass, was used to get structures and it was recognized that there is a top voltage to get ordered deposits. Second, a new method that combines a horizontal electrical field with vertical deposition is studied. The substrate was tilted and put into a chamber with controlled temperature. The experiment was monitored with a CCD camera to calculate the rates of evaporation. In this case, the samples showed different kind of structures that were characterized. Third, the formation of colloidal crystals by spin-coating has been studied. A variety of substrates was used, such as glass, ITO coated glass, gold, chromium and PDMS. It was possible to get samples with 4-5 layers of particles with square and hexagonal packing. Different solvents were studied: acetone, ethanol, 2-butanone etc¿ By laser diffraction it was recognized that these crystals show orientational but not translational order. Different characterization techniques were used: optical and scanning electro microscopy, atomic force microscopy, laser diffraction and Fourier analysis. Finally, the filling of voids was studied by electrochemistry.