Oriented mesoporous organosilica films on electrode: a new class of nanomaterials for sensing

We have recently reported the possible fabrication of highly ordered mesoporous silica thin films with mesopore channels oriented perpendicularly to the underlying substrate, by means of novel electroassisted self-assembly (EASA) method (Nature Mater. 6, 602 (2007)). Such films deposited on an electrode surface can be of great interest in sensing applications if one could introduce organo-functional groups likely to interact with target analytes in a regular environment ensuring great accessibility and fast mass transfer rates. We demonstrate here that aminopropyl-functionalized mesoporous silica films can be electrogenerated in one step by the sol-gel co-condensation route using cetyltrimethylammonium bromide as template. The orientation of the pore is maintained up to 10% aminopropyltriethoxysilane precursor in the starting sol. The presence of amine functions into the film affects its permeability to external reagents, as studied using various redox probes (Ru(bpy)3(2+), FcEtOH, I(-), Fe(CN)6(3-)), and the lack of mesostructuration was found to hinder dramatically mass transport processes. When applied to the voltammetric detection of copper(II) subsequent to open-circuit accumulation, the response of the electrode was greatly affected by the functionalization level, the optimal sensor sensitivity being defined from the best compromise between an amount of amine groups high enough while maintaining mesostructural order.