Three-dimensional mesoporous silica networks with improved diffusion and interference-abating properties for electrochemical sensing

Abstract

One of the key issues of electrochemical sensing in complex matrices is the presence of interferents which can foul the electrode and block the access to the active surface. A possible strategy to promote selectivity is based on the use of interference-abating layers, which can however significantly hamper the sensor response by limiting the analyte diffusion. Here, hard template mesoporous silica films with pore size in the 20–75 nm range and tuneable thickness, deposited onto conductive ITO substrates, were prepared and studied from the physicochemical (FE-SEM, SEM, AFM, water contact angle determinations, UV–vis spectroscopy) and the electrochemical (CV, EIS) point of view. Pore size dependent diffusion phenomena were observed, giving rise to enhanced electrochemical performance for 20–40 nm pores despite the presence of an insulating layer at the electrode surface. The tuneable morphology of the samples together with the wetting properties were found to be pivotal for the understanding of the electrochemical behaviour. The best performance was obtained for the samples with the 20-nm porosity and the highest film thickness. These results were also confirmed by EIS data elaboration, able to provide quantitative measurements about the mass transport resistance of the pores. The modified electrodes were tested for dopamine detection in the presence of a large interfering protein (mucin). The porous and charged network allowed the interfering macromolecule to be excluded, preventing the electrode biofouling and enhancing the performances of the device towards dopamine detection.