Dual-response fluorescent carbon dots for Ag⁺ and Hg²⁺ detection study in actual samples and biological systems

It is important to be capable of achieving highly selective detection of Ag⁺ and Hg²⁺ because their excessive concentrations may pose a serious threat to human health and lead to a variety of diseases. Herein, a new type of orange fluorescent carbon dot with an emission wavelength of 590 nm was synthesized by a hydrothermal method using 1,2,4-triaminobenzene dihydrochloride and ethylenediamine as raw materials. The synthesized orange carbon dots have high affinity for Hg²⁺ and Ag⁺ ions, which can be selectively detected by fluorescence quenching with the detection limits of 0.37 nM and 0.65 nM, respectively. Moreover, the carbon dots have good fluorescence stability for the rapid detection of Ag⁺ and Hg²⁺ over a wide pH range. Importantly, the addition of EDTA reversibly restored the fluorescence intensity of the mixed solution of carbon dots and Hg²⁺, but not the fluorescence intensity of the Ag⁺-containing probe solution, which allowed for a clear distinction between Hg²⁺ and Ag⁺. In addition, the carbon dots have good biocompatibility and low toxicity to MCF-7 cells, which can be used for cell imaging and intracellular ion detection.