유기 형광 물질의 물-공기 계면에서의 응집 현상 연구

Abstract

π-conjugated organic molecules opens up new applications such as nanoscale biological and optoelectronic devices and can be controlled optoelectrical properties easily. Cyano distyrylbenzene derivatives are one example of organic fluorescent molecule and are appeared that ‘unit aggregate’ and the extended array in films. They are characterized by intense color, photochemically induced cis-trans isomerization and π delocalization. Molecular layer of (2Z,2'Z)-2,2'-(1,4-phenylene)bis(3-(4-butoxyphenyl)acrylonitrile), DBDCS based organic fluorescent molecule was studied at the air-water interface and onto solid substrates as Langmuir-Blodgett film. To investigate the aggregation behavior of molecule, surface pressure measurements (surface pressure-surface area isotherm, compression-expansion cycle), atomic force microscopy (AFM), scanning tunneling microscopy (STM), photoluminescence (PL) spectroscopy, and X-ray reflectivity (XRR) are used. These results show that DBDCS molecules change their conformation differently depending on light conditions. Under both conditions, molecules form large domains at the onset point of surface pressure. As surface pressure increases, molecular layer in the dark shows sheet-type structure and maintain their arrangement by π-π stacking and intermolecular interaction (hydrogen bonding, dipole-dipole interaction), whereas disordered structure can observed under UV light due to cis-trans isomerization of molecule.