The Refractive Index Sensing Performance of Au and Ag Nanoparticles Under Different Surrounding Environment

Benefiting from the sensitive response to the change of surrounding environment, localized surface plasmon resonance sensors have wide applications for the detection of bio-/chemical species. Traditionally, the sensitivity research of localized surface plasmon resonance sensors mainly focused on the morphologies and materials of sensor structures. Instead, the effect of environmental refractive index on sensitivity of a gold (Au) nanoparticle sensor is theoretically investigated in this work. The results show that when few free targets are adjacent to the sensor, a better sensing performance can be achieved as the refractive index increases from 1.00 to 1.10. However, when a target layer is closely covered on the Au nanoparticle, a 0.1 decrease in environmental refractive index can lead to a significant improvement in sensitivity. The similar results can be also obtained on a silver (Ag) nanoparticle. This work provides new understandings for advanced sensing applications of surface plasmon resonance sensors. Better refractive index sensing performance is achieved as environmental refractive index increases when Au/Ag nanoparticles are facing few free targets. However, when the nanoparticles are closely covered by target layers, the decreased environmental refractive index can lead to significant improvement in sensitivity. The environmental refractive index-dependent sensing performance provides new understandings for advanced sensing applications of surface plasmon resonance sensors.image