Nonlinear optics, molecular layers

Finally, feasibility studies have clearly demonstrated that S-layer technologies have a great potential for nanopatteming of snrfaces, biological templating, and the formation of arrays of metal clusters, as required in nonlinear optics and molecular electronics. 

On a conceptual level, the ideal format for thin-film materials for nonlinear optics is the Langmuir-Blodgett film. Molecularly engineered chrom-ophores with large hyperpolarizabilities can, in principle, be incorporated at high concentration, with well-defined orientations into films having thicknesses defined by molecular resolution. Extremely large resonantly enhanced values of have been reported in LB films several layers thick (30, 3i) thus the considerable promise of this approach is established. 

Van Cott KE, et al. 2002. Layer By layer deposition and ordering of low molecular weight dye molecules for second order nonlinear optics. Angew Chem Int Ed 41(17) 3236 3238. 

Both quantum functional materials and molecular devices are considered to be the ultimate functional materials. The former shows a novel property which is specific to the structure and the latter represents the smallest possible functional material. Their properties are closely related to optical and photonic functions. The former shows a quantum size effect, a photoluminescence shift to higher energy which depends on layer thickness, which gives us an idea of a nonlinear optical system. Porphyrin arrays connected with molecular wires show a hole carrier photoconductivity or a photoswitching and a photo-information storage, which suggests an idea of a photoactive neuron model. In this paper, conjugated polymer superlattices and porphyrin arrays connected with molecular wires are described. 

The wealth of information obtained on the general principles of crystalline bacterial cell surface layers, particularly on their structure, assembly, surface, and molecular sieving properties have revealed a broad application potential. Above all, the repetitive physicochemical properties down to the subnanometer-scale make S-layer lattices unique self-assembly structures for functionalization of surfaces and interfaces down to the ultimate resolution limit. S-layers that have been recrystallized on solid substrates can be used as immobilization matrices for a great variety of functional molecules or as templates for the fabrication of ordered and precisely located nanometer-scale particles as required for the production of biosensors, diagnostics, molecular electronics, and nonlinear optics [2,3,6]. 

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