A comprehensive review on carbon dots and graphene quantum dots based fluorescent sensor for biothiols

Fluorescent carbon-based nanomaterials such as carbon dots (CDs) and graphene quantum dots (GQDs) owing to their high aqueous solubility, stable photoluminescence and good biocompatibility are showing greater interest in sensing of biothiols. Biothiols mainly glutathione (GSH), cysteine (Cys), homocysteine (Hcys), considered to be an important tool in the clinical diagnosis of many disorders and diseases. Therefore, the development of new probes has fascinated considerable attention since they are simple, sensitive, rapid and cost effective. Although conventional sensors have been designed and widely applied in biothiols determination, but unfortunately they present many limitations and challenges. In this review, we provide a focused outline on the most recent developments concerning fluorescent based CDs and GQDs nanosensor for detection of biothiols. The most important reaction mechanisms and strategies for detection of biothiols were outlined and compared in terms of their sensitivity and selectivity against different biothiol species and other interfering substances viz. metal ions, amino acids, etc. Future research and challenges in designing of functionalized CDs and GQDs are discussed and elucidated.