Structural investigation of a new series of azobenzene-containing self-assembled monolayers on gold

Monolayers of a new series of azobenzene-containing alkanethiols, having the structure CH3(CH2)n−1–Ph–NN–Ph–O–(CH2)mSH (where Ph denotes the benzene ring, n=4, 6, 8, 10, and 12, with m=3 and 5, abbreviated as CnACmSH) were formed on gold substrate by self-assembly process. The monolayers were characterized by contact angle measurement, electrochemical investigation and reflectance absorption infrared spectroscopy (RA-IR). Our results demonstrate that the head chains and the tail chains in the molecules have similar effect to the film structure. The orientations of alkyl chain and azobenzene groups in films are completely evaluated by RA-IR which reveal that the molecules in the SAMs tilt away gradually from the surface normal as the alkyl chains are lengthened. However, the effects of chain length on the orientation of alkyl chains and azobenzene groups are different due to their different spatial requirements.