Deposition of TTF derivative on carboxyl terminated self-assembled monolayers

Oxygen-substituted tetrathiafulvalene (TTF) derivatives of bis(ethlenedioxy)tetrathiafulvalene (BEDO-TTF) were deposited on COOH-terminated alkylsilane self-assembled monolayers (SAMs). The BEDO-TTF molecules were effectively attached on the COOH-terminated SAMs. A formation of mixed valence state (MVS), which is a characteristic conducting phase of TTF, was observed by Fourier transform infrared spectroscopy. Such MVS formation is estimated to be brought about by an appearance of charge-transfer complex of (BEDO-TTF)2(COO⋯H⋯OOC) through a chemical reaction with COOH group of the surface. Atomic force microscopy images revealed the existence of many small islands on the surface. It is expected that the first layer of BEDO-TTF molecules are absorbed onto COOH group of the surface through the reaction, then the first layer stimulates a crystallization of BEDO-TTF above it, giving rise to the islands formation.