Grafted silicas in electroanalysis: Amorphous versus ordered mesoporous materials

This work reports the enhanced response of electrodes modified with ordered mesoporous silica-based materials, as compared to corresponding amorphous materials, in case of open-circuit accumulation and voltammetric detection of a target analyte. Several porous silica samples grafted with either thiol or ammonium groups, displaying high surface areas with various structural characteristics and different pore sizes, have been examined with respect to their ability to concentrate Hg-II species. Better accessibility to the binding sites and faster diffusion processes in the interior of grafted silicas have been observed for the ordered samples prepared by micelle-templating because they contain channels of regular size, which are less tortuous than the irregular pore systems in amorphous materials. When applied in electrochemical detection of Hg-II after preconcentration, the ordered solids gave rise to voltammetric signals higher by more than one order of magnitude in comparison to the amorphous organically-modified silicas. This rather new class of materials, which can be easily produced as ordered organic-inorganic hybrids, is expected to improve the performance of silica-modified electrodes in various fields of electroanalysis.