High sensitive and selective multivariate detection of Hg and Ag in real food samples via Ca, N-co-doped carbon dots based dual-mode platform.

Heavy metals adversely affect the environment, ecosystems, and human health. The effective detection and treatment of heavy metals has become a major global concern. Herein, calcium and nitrogen co-doped carbon dots (E-CDs) were developed using cheap kitchen waste eggshells as precursors, and utilized as dual-mode fluorimetric/colorimetric sensor for the multivariate detection of Hg and Ag. The E-CDs exhibited yellow emission at 420 nm excited at 567 nm, with a quantum yield of 15.49% and lifetime of 12.92 μs. The multivariate detection of Hg and Ag can be achieved selectively by distinguishing via dual-mode respectively. The limit of detection (LOD) for Hg reached 11.28 nM, while the Ag can be determined by fluorimetric/colorimetric dual-mode with LODs of 128.23 nM and 1.02 μM, respectively. Remarkably, the E-CDs integrated with a smartphone-based paper sensor supported by RGB analysis achieved the detection of Hg and Ag with LODs of 56.2 nM and 90.96 nM, respectively. Notably, the recoveries in real samples attained 96.3-105.7% with excellent environmental tolerance. Furthermore, a logic gate circuit was developed to support the potential practical intelligent application. This work highlighted a cost-effective, multi-functional sensing strategy with significant potential for monitoring heavy metal contaminants in environmental and food safety applications.