High-performance plasmonic refractive index sensors via synergy between annealed nanoparticles and thin films.

Plasmonic nanostructure-based refractive index (RI) sensors are the core component of biosensor systems and play an increasingly important role in the diagnosis of human disease. However, the costs of traditional plasmonic RI sensors are not acceptable to everyone due to their expensive fabrication process. Here, a novel low-cost and high-performance visible-light RI sensor with a particle-on-film configuration was experimentally demonstrated. The sensor was fabricated by transferring annealed Au nanoparticles (NPs) onto a thin gold film with polymethyl methacrylate (PMMA) as a support. RI sensitivities of approximately 209 nm/RIU and 369 nm/RIU were achieved by reflection and transmission spectrum measurements, respectively. The high sensitivity is due to the strong plasmon-mediated energy confinement within the interface between the particles and the film. The possibility of wafer-scale production and high working stability achieved by the transfer process, together with the high sensitivity to the environmental RI, provides an extensive impact on the realization of universal biosensors for biological applications.