Highly sensitive plasmonic sensor fabricated with multilayer Ag/Si3N4/Au nanostructure for the detection of glucose in glucose/water solutions

Abstract

The surface plasmon resonance (SPR) sensors are well-known for their high sensitivity and resolution, for example in the detection of a change in the refractive index of materials due to variations in the physical conditions (e. g., temperature, relative concentration) and/or impurities. In the majority of the cases, SPR sensors are made by using a thin film of a single metal, like gold. Here, we introduce a new type of SPR sensor fabricated by using a multi-layer nanostructure Ag/Si3N4/Au. This sensor has shown excellent performance in monitoring relative concentration of glucose in glucose/water solutions. The results presented in this work show that the sensor can resolve relative concentrations of glucose in glucose/water solutions down to a limit of about a percent. The performance of the sensor is enhanced significantly by high strength of the evanescent electric fields associated with the surface plasmon resonance. Computer simulations show that the electric field at the surface of this multilayer sensor is stronger by as much as 50 % compared to the field at the surface of a gold film sensor. Additionally, the evanescent electric fields persist above the sensor surface to much longer distances with decay lengths of as large as approximately 300 nms. Strong evanescent fields with long decay lengths add to the performance of the sensor and facilitate detection of the changes in the optical properties of materials up to large distances from the sensor.