High-sensitive Detection of Caffeine by a Gold-deposited Glass Rod SPR Sensor Using Graphene Oxide Overlayer

Abstract

A simple SPR sensor consisting of a gold-deposited glass rod with a diameter of 2 mm coated with a graphene oxide (GO) overlayer was developed. The concentrations of the GO aqueous dispersions were 0.5 and 5 mg mL⁻¹, and these solutions were used to fabricate two types of sensors by immersing the gold-deposited glass rod sensor for 15 minutes and then drying in air to form a coating layer. The response property of the GO-coated sensors was evaluated using the ethanol aqueous solutions and the sensitivity of the sensor coated with 5 mg mL⁻¹ was slightly improved compared to the unmodified one. On the other hand, the sensitivity to the dilute caffeine aqueous solution was greatly improved. It was found that the sensor with five layers of GO showed the best response and it was possible to detect lower concentrations than the caffeine contained in common beverages. On the other hand, the sensitivity decreased when the number of layers exceeded 5, and the enhancement effect of GO was almost lost at 10 layers. In this study, the gold-deposited glass rod SPR sensor coated with GO showed high sensitivity to caffeine. It was found that this sensor has potential as a new sensor for food analysis.