Nanostructured plasmonic sensors.

Surface plasmons (SPs) are coherent oscillations of conduction electrons on a metal surface excited by electromagnetic radiation at a metal-dielectric interface. The growing field of research on such light-metal interactions is known as ‘plasmonics’.1-3 This branch of research has attracted much attention due to its potential applications in miniaturized optical devices, sensors, and photonic circuits as well as in medical diagnostics and therapeutics.4-8 Plasmonics is also a highly active area due, in part, to recent advances in nanofabrication methodologies.9-12 These methodologies have led to the realization of metal nanostructures composed of nanoparticles (NPs),13 nanoholes,14 and other components15 with precisely controlled shapes, sizes, and/ or spacings.16,17 Such exquisite synthetic control in combination with advances in theory and the emergence of quantitative electromagnetic modeling tools has provided a better understanding of the optical properties of isolated and electromagnetically coupled nanostructures of various sizes and shapes. In addition to control over the geometry and optical properties of nanostructures,18,19 various strategies for modifying the surfaces of these materials make it possible to effect the selective binding and detection of specific targets for chemical and biological sensing.20,21