Self-assembly and Langmuir-Blodgett (LB) film of a novel hydrogen-bonded complex: A surface enhanced Raman scattering (SERS) study

Hydrogen-bonded complexes composed of a 1,2-bis(4-pyridyl)ethylene and two fatty acids were employed for the fabrication of organized monolayers. Surface enhanced Raman scattering (SERS) spectra demonstrated that monolayer Langmuir-Blodgett (LB) film could be directly obtained at surface pressure 5 mN m ^-1 by depositing the complex with one of its hexadecoic acid molecules lost due to decomposition of hydrogen bond. For the self-assembled monolayer, SERS spectra indicated that during self-assembling process, only one part of the complex was adsorbed on silver substrate, just similar to that occurring at air/water interface due to the same reason. Increasing the molar ratio of the hexadecoic acid to the mole of 1,2-bis(4-pyridyl)ethylene in the complex solution up to 16-fold, we successfully prepared a monolayer of the complex without decomposition. Under this condition the 1,2-bis(4-pyridyl)-ethylene was inferred to adopt the adsorption flat on the substrate.