Synthesis and non-linear optical properties of some organic self-assembled films on hydroxylated substrate surfaces

Abstract

Films of some small molecules on hydroxylated silica surfaces have been prepared successfully by the self-assembly technique, using the condensation of the CHO group of 4-substituted benzaldehyde with the NH₂ group of 4-substituted aniline derivatives. Second-harmonic generation (SHG) was observed in all the monolayers of the chromophores and changed with different π-electron systems. The maximum χ⁽²⁾ 7.9 × 10^–10 esu and the orientation angles of the chromophore dipoles of all the films were 33–38 °. This method is capable of generating multilayer films. For a Z-type multilayer, the SHG signal increases quadratically with the number of chromophore layers. The films have high structural stability.