Preconcentration electroanalysis at surfactant-templated thiol-functionalized silica thin films

Surfactant-templated thiol-functionalized silica thin films have been deposited by spin-coating on glassy carbon 6 electrodes. Their permeability properties have been characterized using three solution phase redox probes (Ru(NH3)(6)(3+) Fe(CN)(6)(3-), FcMeOH) and their suitability to be applied for preconcentration electroanalysis has been studied using Ag+ as model analyte. Both the film permeability to redox probes and the performance of the modified electrodes towards Ag+ sensing were found to be dramatically influenced by the composition of the sol used for preparing the thin films, and especially its surfactant content. The best results were obtained with materials prepared from rather high surfactant concentration because they led (after template removal) to highly open mesoporous deposits with readily accessible thiol groups in the mesopore channels. The effect of various parameters on the electrode response have been investigated, including the composition of the detection medium, the accumulation time, the level of functionalization of the films and their preparation conditions, and the analyte concentration. A linear response for Ag+ was obtained in the 0.2-10 mu M concentration range.