An effective method for cysteine determination based on fluorescence resonance energy system between co-doped graphene quantum dots and silver nanoparticles

Abstract

Cysteine (Cys) is a crucial amino acid. Developing a method for Cys evaluation and detection is necessary for the diagnosis of various diseases. A variety of sensors use graphene quantum dots (GQDs) for biological compound determination; however, GQDs demonstrate very poor fluorescence quantum yield. Therefore, we doped nitrogen and phosphorus into GQDs to form composite material NP-GQDs with enhanced fluorescence properties. NP-GQDs were characterized by ultraviolet-visible, fluorescence spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Then, we used NP-GQDs as donors and silver nanoparticles (AgNPs) as acceptors to design a fluorescence resonance energy transfer (FRET) system for Cys detection. Optimal conditions for sensing were investigated, and under these conditions our FRET system showed good results in Cys determination. The fluorescence intensity of NP-GQDs was quenched proportionally along with increasing Cys concentration from 0.5 to 4.5 µM and the limit of detection (LOD) was 0.1 µM. In the presence of different amino acids, the FRET system also showed excellent selectivity for the Cys detection. © 2022, Korean Institute of Chemical Engineering (KIChE).