Effect of anchoring groups on electrochemical self-assembly of ZnO/xanthene dye hybrid thin films.

Three xanthene dyes with different anchoring groups, eosin Y (EY), dicarboxy-eosin Y (CEY) and sulfonated eosin Y (SEY) were employed to electrodeposit ZnO/dye hybrid thin films to study the effect of anchoring groups on the electrochemical self-assembly (ESA) of hybrid thin films. The adsorption stabilities of the dyes in oxidized form were in the order, CEY >> EY > SEY, as evaluated by Langmuir isothermal adsorption experiments. The reduction potential of dyes, the dependence on Zn(2+) concentration that reflects stabilities of complexes between reduced dyes and Zn(2+) ion, and the diffusion coefficients of dyes were determined by electrochemical measurements. These properties of the dyes were considered as the key parameters to dominate ESA of hybrid thin films which were actually prepared with these dyes by potentiostatic electrolysis at -0.8 and -1.0 V (vs. SCE) representing ESA with dyes in oxidized and reduced forms, respectively, and were analyzed for their chemical composition and structural features.