Switching of Dye Loading Mechanism in Electrochemical Self-Assembly of CuSCN/DAS Hybrid Thin Films

Abstract

Electrochemical self-assembly of CuSCN/4-(N,N-dimethylamino)-4'-(N'-methyl)stilbazolium (DAS) hybrid thin films has been carried out on systematic variation of bulk concentrations of [Cu(SCN)]+, DAS tosylate (DAST) and changing their flux density by angular speed of rotation of the rotating disk electrode. Switching of DAS loading mechanism dependent on the DAST concentration in the bath has been verified and quantified. The switching occurs at the concentration ratio [Cu(SCN)]+/DAST = ca. 40, above which the loading becomes diffusion limited for DAS to be occluded in the CuSCN grains, whereas the second order reaction rate of complex formation between CuSCN surface sites and DAS begins to limit the DAS loading when the relative concentration of DAST exceeds this border, resulting in a phase-separated precipitation of CuSCN and (DAS)(SCN) aggregate in unique nanostructures.