A comparative study of Fe (II) doped chiral L/D-methionine carbon dots (MCDs) as a “Turn-on” fluorescent probe for the sensitive detection of L – cysteine

Chiral carbon dots have prominently influenced in the field of chemical, biological, and medicinal research. Comparing to achiral carbon dots, chiral carbon dots exhibit unique characteristics in biosensing application. In this perspective, we have developed bright blue, fluorescent L and D-Methionine Chiral carbon dots (MCDs) using a simple microwave assisted process for effective sensing of L-Cysteine. L-Cysteine plays a vital role in balancing the physiological redox in the body. These MCDs can be complexed with Fe2+ ions to create an energy transfer quenching system due to distinctive N and S functional group distribution on their surface. However, L-Cysteine attaches to Fe2+ ions in a competitive manner, leads to recovery of MCDs fluorescence. As a result, a "turn-on" fluorescent sensing platform based on L and D-Methionine-CDs has been developed for the rapid identification and detection of L-Cysteine. The probe shows good selectivity and sensitivity with coexisting biomolecules and ions. From comparative PL studies, D- MCDs are more responsive than L-Meth CDs towards the detection of L-cysteine with LOD of 0.71 µM and 0.94 µM respectively. The chiroptical properties were evaluated and the probe extends its practical application in paper strip and in biological matrix such as human blood serum with satisfactory recoveries in the range 85-104%.