UV-VISIBLE ABSORPTION AND SECOND HARMONIC GENERATION INVESTIGATIONS ON THE H-AGGREGATION IN LANGMUIR-BLODGETT MONOLAYERS DEPOSITED UNDER DIFFERENT CONDITIONS

摘要

We investigated the aggregation status and formation mechanisms of a hemicyanine derivative (HD) in Langmuir-Blodgett (LB) monolayers prepared under different conditions by pi-A isotherm, second harmonic generation (SHG) and UV-visible absorption measurements. The HD molecules form H-aggregates in LB monolayers leading to a blue-shift of the absorption band with respect to that of the monomeric HD in the chloroform solution and reduction of hyperpolarizability beta. The H-aggregation formation mainly occurred during the compression process on the Langmuir trough. The degree of H-aggregate could be reduced and effective beta could be enhanced by raising the compressional speed and/or lowering the deposition surface pressure. [References: 13]