Light-Induced ChargeTransfer in Self-Assemblies: Applications for Nonlinear Optical Materials

Lise Meitner Position M 598 Light-Induced Charge Transfer in Self-Assemblies Dusan VELIC 09.10.2000 Nonlinear optical materials are of great importance for electro-optical industry. However, question of their versatility, stability and high efficiency is still open. The aim of the project is to prepare a new class of supramolecular surface structures which generate optical second-harmonic output. The structure consists of an inclusion complex, where a guest molecule is placed into a "bucket" of a host molecule which is attached through the S-Au bond on gold surface, forming self-assembled monolayer-like film. The guest molecules are proposed to be push-pull p-electron systems, like stilbenes and julolidinyls, with high values of susceptibility which is responsible for generating the optical output. The host molecules are proposed to be thiolated cyclodextrins providing required protective and stabilizing "bucket" on the surface for the guest. The self-assembling processes of inclusion and monolayer formation are monitored by second-harmonic generation, which is simply a measurement of the doubled frequency of incoming laser light. This technique serves also as a direct diagnostic tool for the quality of nonlinear optical signal due to the resonantly enhanced surface second-harmonic generation. To achieve the maximum of this frequency doubled light, the optimal complex will be tailored based on the experimental and theoretical investigations. However, this application attempt must be seen more in a conceptual way where we propose a novel synergic structure, where one component allows the surface attachment and another component allows optical response. The guest-host inclusion should be then a new motive which does not rely on specific inorganic, organic, or polymeric nonlinear optical materials, but provides a flexible nanostructure for variety of species to form crystalline-like films. This inclusion surface structure might then represent a novel approach in preparation of nonlinear optical materials.