Superstructure of silver crystals in a caged framework for plasmonic inverse sensing

Abstract Lowering the limit of detection is key to the design of sensors. Conventional transducers generate a signal proportional to the concentration of the molecule, but low concentrations are still difficult to detect with confidence. Here we present an inverse sensor that induces a signal that is larger when the target molecule is less concentrated. Each sensor consists of a micro-pot reactor with an inner volume for storing the reactants and the cage walls, over which many silver hotspots are spread, working as optical antenna to produce amplification of the signal. The aim is to attain inverse sensitivity during the enzymatic reaction, where reduction of the silver occurs. We demonstrate the sensitivity and robustness of this approach by detecting glucose concentrations down to 10-12 M.