This disclosure provides, among other things, a nanosensor comprising a substrate and one or a plurality of pillars extending from a surface of the substrate, where the pillars comprise a metallic dot structure, a metal disc, and a metallic back plane. The nanosensor comprises a molecular adhesion layer that covers at least a part of the metallic dot structure, the metal disc, and/or the metallic back plane and a capture agent bound to the molecular adhesion layer. The nanosensor amplifies a light signal from an analyte, when the analyte is specifically bound to the capture agent.