Functionalization of a porous silicon impedance sensor

A sensor device is demonstrated based on changes in the impedance within a layer of porous silicon on exposure to the target analyte. Selectivity can be obtained by attaching functional organic groups onto the porous silicon. If the target molecules do not interact with the attached functional groups, then the sensor's response varies linearly with concentration. In the event however, when strong hydrogen-bonding occurs a much larger response is recorded on exposure to low concentrations than would be expected. The hydrogen-bonding either causes increased penetration of the solvent into the porous matrix or reduces the potential drop across the solvent/porous silicon interface, i.e. reduces magnitude of the space charge capacitance in the silicon nanorods. •Impedance based porous silicon sensor demonstrated•Selectivity enhanced by functionalizing the porous silicon with active organic groups•Mechanism of improved selectivity explained in terms of hydrogen bonding