Polypyrrole/Graphene Quantum Dot Composites as a Sensor Media for Epinephrine.

In this paper, we discuss a new biosensor for simple and rapid detection of epinephrine (EP) based on polypyrrole/graphene quantum dot (PPy/GQD) composites. Presence of amine groups on the PPy backbone leads to surface passivation of GQDs. As a result, the composites exhibit strong fluorescence emission, which can be up to three times that of pristine GQDs. In neutral to alkaline solution, the EP on the surface of PPy/GQD composites is converted to a quinone, which triggers the fluorescence quenching of PPy/GQD composites via a photoinduced electron transfer process. Hence, the concentration of EP can be effectively monitored by measuring the variation in the fluorescence signal of PPy/GQD composites. The quenched fluorescence intensity of PPy/GQDs was proportional to the concentration of EP (0.7-400 M). We used our method to determine the concentration of EP in human serum samples and obtained satisfactory results.