Structural investigation of Langmuir-Blodgett films on self-assembly modified Au substrates

To improve the homogeneity and stability of single-layer azobenzene LB films on gold, self-assembled monolayers (SAMs) of terminally substituted alkyl thiol, HS(CH2)(2)-X(X=NH2, OH, COOH and CH2SO3Na, respectively), were used to modify the substrates before LB film deposition. It was found that single-layer C8C3 LB films on these modified substrates were more uniform and stable. Reflecion-Absorption (RA) FTIR measurements on these films indicated that at the LB/SAMs interface, ionic bonds, have formed for the modification with -NH2 while hydrogen bonding occurred for modifications with -OH, -COOH and -SO3Na, respectively. It can be concluded that the ionic or hydrogen bonding at the LB/SAM interface is responsible for the improvement in homogeneity and stability. It was believed that the less defected films after the time aging were most probably due to the ionic bond and hydrogen bonding mentioned above.