Langmuir-Blodgett films on non-centrosymmetric azobenzene dyes for non-linear optical applications

The preparation and characterization of Langmuir-Blodgett films containing 4-(N-hydroxyalkyl)amino-4′-nitroazobenzene dyes (with alkyl≡hexyl and dodecyl) are discussed in this paper. High quality films of these hydroxyalkyl-substituted aminoazobenzenes have not been obtained in pure form. Instead, monolayer films of these dyes in mixtures with stearic acid have been prepared on glass and fused quartz substrates. Centrosymmetric and non-centrosymmetric multilayer films of the dye/ stearic acid systems have also been built up on glass and quartz. Molecular ordering of the non-centrosymmetric azobenzene dyes in the films is indicated by polarized electronic absorption spectroscopy and by second-harmonic generation from the films.