INDEX template effects

A possibility to consider polyciystalline platinum surface as some combination of low index surfaces or as some disordered single crystalline surface surely caimot be immediately concluded from the values of zero charge potentials exclusively. Experiments with some intermediate model systems more or less reduceable to simple additive combinations of several planes, or of terraces and steps, are of increasing interest. Microfacetted electrodes, various types of nanoparticles prepared by precise non-electrochemical techniques, non-coalesced electrodeposited particles, " and single platinum microspheres deposited on micro-electrodes, as well as highly ordered templated electrdeposits can be considered as most ordered real platinum materials helpful to discover stractural effects at atomic level. However they all are still too simple to compare with, to say, platinized platinum, and attempts to electrodeposit the dispersed metallic multilayers of more and more ordered type ° are also relevant. 

On this basis, a rapid and nondestructive method, ellipsometric porosimetry (EP), has been developed in which adsorption-desorption isotherms are determined from the variations of film refractive index efr induced by the change of partial pressme of a solvent above a film. The setup combines a pressure-controlled chamber (conventional gas volumetric characterization devices) and a classical eUipsometer thus, HeS is determined for each vapor pressure and is a direct measme of the adsorption isotherm. A typical example is shown in Figure 33.3a for a Si02 templated with CTAB thin film (Martinez Ricci, M.L., Fuertes, M.C., Violi, I.L., Grosso, D., and Soler lUia, G.J.AA., Rational design of mesoporous films for synthesis of responsive Bragg reflectors (unpublished).). The refractive index increases from eff (630 nm) = 1.21, for a large fraction of air inside micropores and/or mesopores within the silica nanostructure, to (630 nm) = 1.37 when pores are saturated with water. The steep increase at intermediate vapor pressures is associated with the capillary condensation inside pores. The hysteresis in the desorption branch is due to the presence of water in the necks that join pores, whose effective radii are smaller than the pore radius. 

The fine-tuning of the effective refractive index with the template, temperature, and rate of thermal treatment or growing mixed MTFs opens new opportunities for the design of low- materials, that is, eff < 1.2 valuable for many apphcations, such as waveguide claddings or optical resonators [36]. 

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