Аннотация:Plasmonic nanosensors (PNS) have seen a momentous leap in the recent decade as a powerful tool in analytical applications. PNS involve designing of plasmonic nanoparticles (PNPs) which have found their important role in various chemi-sensors and biosensors owing to their surface plasmon resonance (SPR) extinction. These PNS offer benefits such as excellent selectivity, sensitivity, on-site detection ability, portability, rapid sensing, and improved performance of devices. The PNPs act as transducer materials and are explored for their sensitive readouts in various assay techniques. These PNPs exhibit unique physical–chemical and size-dependent properties and play different roles in different types of optical sensors. As a colorimetric sensor, SPR transduces a signal by facilitating change in intensity and spectral position in response to analyte. In plasmon-enhanced fluorescence assay, SPR concentrates the incident electromagnetic field and modulates fluorescence emission. In surface-enhanced Raman scattering, plasmons amplify the Raman signal for ultrasensitive detection. This chapter summarizes the recent research progress in plasmonic optical sensors, giving an emphasis on the physical basis of plasmon properties and how these principles guide the design of sensors. In addition, this chapter provides comprehensive information on different PNPs, synthesis modes, and the features of different shapes and materials in sensing applications using different spectroscopic techniques. This chapter also addresses the future trends and perspectives of PNS and its applications in health care, space, food safety, and environmental monitoring sectors.