Ratiometric fluorescent detection of Hg²⁺ using dual-emissive carbon dots in an immiscible system

A facile one-pot hydrothermal method was established to simultaneously prepare blue and yellow emissive carbon dots (BCDs and YCDs) in an immiscible system. This method eliminated the need for complex purification steps. The resulting BCDs and YCDs exhibited uniform sizes and excellent fluorescence properties. A ratiometric fluorescent probe based on B/YCDs was designed for the rapid and selective detection of Hg²⁺ with a detection limit of 15 nM. The probe was capable of reliable detection in real water samples with recoveries of 92.42 ~ 110.02%. To further enhance practicality, we incorporated fluorescent papers and hydrogels for visual Hg²⁺ detection, making it ideal for on-site applications. Additionally, a smartphone-based sensing platform, integrating RGB value analysis, was also developed for accurate Hg²⁺ detection. This work represents a significant advancement in the field by providing a user-friendly and cost-effective approach for sensitive on-site detection of hazardous mercury pollution.