Abstract:

The self assembly behavior of inclusion complex of 4- N (2' -meraptoethyl) carboxylamino-azobenzene (Azo) with β-cyclodextrin (β-CD) on gold surface have been studied. X-ray photoelectron spectroscopy (XPS ) results suggested that the monlayers of Azo β-CD inclusion complex was formed on gold surface by self-assembly. The molar ratio of azobenzene and β-CD on gold surface was estimated to be 1: 1 by XPS. The apparent electrochemical rate constant (Kobs) of Azo SAM decreases with increasing assembling time that is attributed to increasing packing-density of Azo in the monolayer. The close packed structures in Azo SAM restrict the conformation change of azobenzene units in the film so tha it leads to a decrease of its electrochemical activity. In contras, the Kobs of complex SAM changes slightly with the assembling time. After an assembling time of 76 h, the Kobs of complex SAM is two order of magnitude larger than that of Azo SAM. The higher electrochemical activity of azobenzene groups in the complex SAM than that in Azo SAM suggests that the Azo moieties are separated by β-CD in the complex SAM. 

Key words: Azobenzene derivative, Self-assemblde monolayer(SAM), β-cyclodextrin, Inclusion complex