Development of a multi-functional SPR sensing system using a square glass rod with two gold-deposited adjacent faces

A multi-functional sensing system based on surface plasmon resonance (SPR) phenomenon using a square glass rod with two gold-deposited adjacent faces was developed in this work. This sensor system consists of a unpolarized light-emitting diode, a gold-deposited square glass rod, a polarizing beam splitter, and two photodiodes. The SPR responses of two adjacent faces are independently and simultaneously measured with a polarizing beam splitter and two PDs. The response property of the gold-deposited face was confirmed using methanol solutions of ethylene glycol. The response curve of the sensor of the 45 nm gold-deposited face was compared with the theoretical curve calculated using multi-layer Fresnel equations. It was confirmed that the experimental curve is similar to the theoretical one. An evaluation was carried out on the square glass rod, which has an unmodified face and Teflon AF2400 coated gold-deposited face as multi-functional sensor. It was confirmed that this sensor can simultaneously measure the ethanol concentration in the glucose mix solution and refractive index of the sample from the calibration curve. Since this sensor can measure multiple components simultaneously, expected applications to various fields include medical diagnosis, food analysis, and environmental monitoring.