Serine and histidine-functionalized graphene quantum dot with unique double fluorescence emission as a fluorescent probe for highly sensitive detection of carbendazim

Abstract

The application of graphene quantum dots has been focused on fluorescence detection, but poor functionality and low luminous efficiency limit its many applications. The study reports synthesis of serine and histidine-functionalized graphene quantum dot (Ser-GQD-His) via one-step simple pyrolysis. The resulting Ser-GQD-His offers an unique double fluorescence emission. Ultraviolet-light excitation at 360 nm produces one strong blue fluorescence with the quantum yield of 28.6 %. While visible-light excitation at 485 nm produces one stronger yellow fluorescence with the quantum yield of 51.2 %. The Ser-GQD-His was used as an optical probe for fluorescence detection of carbendazim coupled with DNA recycling amplification. By target-induced DNA recycling, one carbendazim molecule can lead to the formation of many G-quadruplex/hemin DNAzymes. The formed DNAzymes catalyze oxidation of phenylenediamine into 2,3-diaminophenazine (DAP) and achieves to a significant signal amplification. Meanwhile, the interaction of DAP with Ser-GQD-His leads to a fluorescence quenching process of Ser-GQD-His and fluorescence enhancement of DAP. This further enhances the detection signal. The ratiometric fluorescence signal increases linearly with increasing carbendazim in the range from 1.0 × 10−16 to 1.0 × 10−9 M with the limit of detection of 6.1 × 10−17 M. The proposed method exhibits a higher sensitivity and selectivity compared with reported methods.