Spectro-ellipsometric studies of activated sol–gel thin films to detect Cu2+ ions in aqueous solutions

Thickness, refractive index n and extinction coefficient k of eriochrome cyanine R (ECR) dye doped mesostructured silica film (ECRMSSF) dip-coated on silicon wafers without prior removal of surfactant have been determined in the visible range of the spectrum by spectroscopic-ellipsometry (SE). ECRMSSF was used as sensing detection layer of Cu2+ in aqueous solutions of known pH. The dependence of optical parameters on the pH range of the aqueous phase (pH=6–8) was investigated. The detection reversibility of ECRMSSF was demonstrated. An electron paramagnetic resonance spectrum demonstrated the complexation of Cu2+ by the entrapped ECR.