A biocompatible chitosan-based nanosensor for dual-functional detection and removal of mercury ion and its application in living cells and environmental systems.

Chitosan has been widely utilized due to its biodegradable, environmentally friendly, and extensive resources properties. The modification of chitosan has garnered significant attention as a promising approach for detecting and removing heavy metal contaminants. Herein, we presented a novel dual-functional fluorescent nanoprobe Nano-NAP for the effective detection and absorption of Hg, which could be conveniently fabricated by self-assembling a small-molecule Hg fluorescent probe into a carrier of chitosan-based fluorophore (CS-MeO). The resulting Nano-NAP demonstrated commendable ratiometric fluorescent response to Hg with the advantages of high selectivity, minimal interference, low detection limit (0.22 μM) and good pH stability. Given the excellent optical response, the Nano-NAP has been successfully applied in the practical measurement of Hg ions in soils, seafood and actual water samples. What's more important, we have further developed a convenient and portable detection platform based on smartphone-compatible test paper strips for on-site and quantitative detection of Hg levels. Furthermore, the visualization of Nano-NAP toward Hg in living cells has also been accomplished, which showed the robust fluorescent imaging behavior and highlighted its broad potential in biosystem applicability. Finally, the Nano-NAP based hydrogel was made and employed as an efficient Hg adsorbent in the absorption of Hg in aqueous solution.