Optically functional surfaces

It is beyond the scope of this Chapter to discuss all kinds of various coating techniques, properties of the supports, properties of the coatings and the various fields of application of the composites in catalysis, separation techniques, materials science, colloid science, sensor technology, biocompatible materials, biomi-metic materials, optics etc. The scope had to be restricted to the fundamental properties of ultrathin organic layers on solid supports followed by some examples, outlining the benefit of the tailored functional surfaces such as SAM and polymer brushes for catalysis. 

Figure 6. Optical transmittance change at 660 nm as a function of various DMMP concentrations for the optical waveguide surface coated with the PEM polymer film.

A full set of optical functions consists of reflectivity R and absorption coefficients, p, the imaginary 82 and real 81 parts of the dielectric function 8, the absorption and refraction indices k and n, the product of the integral joint density of states (DOS) function and the transition probability, equal within constant factor to the effective number of valence electrons n E) participating in the transitions to given energy level A the effective dielectric coefficient Sef, and the characteristic electron energy functions for volume (-Imc ) and surface (-Im(l+8) ) losses. 

With ellipsometry the polarization state of reflected radiation rather than just its intensity, is experimentally determined. Ellipsometry is not so much another experimental technique but a more thorough variety of the traditional ones, whether external or internal reflection. Two results per resolution element, namely the ellipsometric parameters (cf. Eq. 6.4-17) and A, are derived independently from the measurements. These can further be evaluated for the two optical functions of the medium behind the reflecting surface or other two data of a more complex sample. In any case there is no information necessary from other spectral ranges as it is for Kramers-Kronig relations. In comparison to the conventional reflection experiment, ellipsometry grants more information with a more reliable basis, e.g. since no standards are needed. 

ELECTRONIC AND OPTICAL TRANSDUCTION OF PHOTOISOMERIZATION PROCESSES AT MOLECULAR-AND BIOMOLECULAR-FUNCTIONALIZED SURFACES... 

The exciting prospect of incorporating optical functions into Si integrated circuitry has led to the great interest in porous Si. Besides investigations of the physical properties, the mechanism of pore propagation has also been studied (see e.g. [31]). On the other hand, there is little information about pore initiation on the flat surface of a Si single crystal. A detailed discussion of these effects is beyond the scope of this chapter. 

Microstructured Polymer Surfaces with Complex Optical Functions for Solar Applications... 

Abstract In solar applications microstructured polymer surfaces can be used as optically functional devices. Examples are antireflective surfaces, dayUghting, sun protection systems, concentrator photovoltaic modules and light trapping structures in organic solar cells. The examples and the principles of function of the respective microstmctures are described in detail. The suitability of different manufacturing methods is discussed. Two of them, ultraprecision machining and interference lithography are described. For the latter experimental results are shown. Finally, the opportunities and the risks of the shown approaches are discussed. 

Electronic and Optical Transduction of Photoisonierization Processes at Molecular- and Bimolecular-Functionalized Surfaces... 

Despite the consistent picture of a controlled protein monolayer formation by molecularly specific "recognition" reactions deduced from the optical data we were still concerned about the limited optical resolution. In order to further enhance the special resolution euid to observe the binding of streptavidin to a functionalized surface (eventually) with molecular resolution we performed atomic force microscopic (AFM) studies at a membrane/solution-interface. In Fig.6 the experimental situation is schematically sketched. Prior to the protein injection a lipid monolayer with coexisting fluid and ordered domains deposited onto a condensed monolayer on the mica substrate has to be imaged by scanning the tip across the membrane surface. It is well-known that a fluid membrane can not stand the load of the tip (even at a reduced force) so that we expect a height contrast between the two areas of about a monolayer thickness... 

A method has been developed for the prediction of thermal conductivity as a function of temperature, porosity, material skeleton thermal conductivity, thermal conductivity of the gas in the porous, mechanical load on the porous material, radiation, and optical and surface properties of the material s particles [105]. The method produced satisfactory results for a wide range of materials (quartz sand, powdered Plexiglas, perlite, silica gel, etc.). 

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