Abstract: Disclosed herein are compositions including a nanosensor that is sensitive to an analyte such that the nanosensor emits a fluorescent signal upon detecting the analyte, and a catalytic agent that catalyzes a reaction in which a target substrate is converted into one or more products, such that at least one of the one or more products is the analyte. In addition, methods of using the nanosensor-catalytic agent compositions to detect a target substrate are disclosed.