Light Enhanced Electron Transduction and Amplified Sensing at a Nanostructure Modified Semiconductor Interface

Visible and UV light are demonstrated to significantly enhance the sensing properties of an n‐type porous silicon (PS) extrinsic semiconductor interface to which TiO 2 and titanium oxynitride (TiO 2‐ x N x ) photocatalytic nanostructures are fractionally deposited. The acid/base chemistry of NH 3 , a moderately strong base, and NO 2 , a moderately strong acid, couples to the majority charge carriers of the doped semiconductor as the strong acid (TiO 2 ) enhances the extraction of electrons from NH 3 , and the more basic TiO 2‐ x N x decreases the efficiency of electron extraction relative to the untreated interface. In contrast, NO 2 and a TiO 2 or TiO 2‐ x N x nanostructure‐decorated PS interface compete for the available electrons leading to a distinct time dependent electron transduction dynamics as a function of TiO 2 and TiO 2‐ x N x concentration. Only small concentrations of TiO 2 and its oxynitride and no self‐assembly are required to enhance the response of the decorated interface. With light intensities of less than a few lumens/cm 2 ‐sterad‐nm, responses are enhanced by up to 150% through interaction with visible (and UV) radiation. These light intensities should be compared to the sun's radiation level, ≈500 lumens/cm 2 ‐sterad‐nm suggesting the possibility of solar pumped sensors. The observed behavior in these systems is largely explained by the recently developed Inverse Hard/Soft Acid/Base (IHSAB) concept.