Covalently modified high purity carbon nanodots for enhanced detection of arsenic

Covalent functionalization is always known for superior colloidal stability, improved selectivity, fluorescence stability, and prevents aggregation of molecules, which reflects higher sensitivity and is preferred over non-covalent interactions. Herein, we have demonstrated one-step covalent functionalization of high-purity carbon nanodots (CNDs) with ligands such as glutathione (GSH) and cysteine (CYS) for the enhanced specificity towards arsenic detection. An improved detection limit of 0.26 ppt and 1.7 ppb for As (III) with GSH and CYS functionalized CNDs was observed while comparing with previous non-covalent thiol-based probes with a linear and non-linear Stern-Volmer plot meant for both static and dynamic quenching processes. The arsenic fluorescent probe was thoroughly characterized with spectroscopic and morphological studies. Further, an attempt was also made to develop a paper analytical device (PAD) for instrument free arsenic detection in water, and the real-world application is demonstrated by analyzing the tap water and groundwater samples from arsenic arsenic-affected area.