Trapping Proteins within Gold Nanoparticle Assemblies: Dynamically Tunable Hot-spots for Nanobiosensing

The combination of stimuli-responsive materials with localized surface plasmon resonance nanotransducers provides new leverages in hot spot-based nanosensing. We introduce a simple and effective biodetection method based on the hydro-responsive property of (3-aminopropyl)-triethoxysilane (APTES). Gold nanoparticles were adsorbed onto hydro-responsive APTES thin film. The exposure of the film surface to an aqueous solution results in opening inter-particle gaps, allowing analyte binding. A subsequent drying of the sensor surface closes the gap by bringing the nanoparticles to the initial position, thereby trapping the analyte in the most sensitive regions (electromagnetic hot spots). In this reversible configuration, the generation and tuning of the hot spots are independent from both the presence of the analyte and the functionalization of the nanoparticles, which yields highly resolved coupled plasmon bands and provide a general and flexible nanosensing modality. Furthermore, the intensity of the hot spots can be easily and reversibly tuned to obtain pico-molar sensitivity.