Carbon Dot-Based Ratiometric Fluorescent Probe Platform for Visual Quantitative Determination of Hg²⁺

Determination of Hg 2+ is crucial as its high toxicity poses a potential serious threat to food and the environment. Therefore, it is urgent to explore a portable, cost-effective, and visual approach to monitor Hg 2+ . Herein, ratiometric-constructed dual-emissive carbon dots (P-R-CDs) with dual emissions at 440 and 575 nm were fabricated by blue CDs and orange CDs for visual quantitative detection of Hg 2+ . The vivid colorimetric sensing can be achieved by quantitative quenching blue emission with Hg 2+ and relative stable orange emission. Consecutive fluorescent color transformation with elimination of blue emission by Hg 2+ embodied visible distinguishable determination of Hg 2+, with a detection limit of 2.9 nM. Furthermore, a smartphone-supported visual sensing platform was established for the determination of Hg 2+ by capturing and identifying the RGB value of the variation precisely. The smartphone assistant detection greatly promoted the effectiveness of detection and provided promising on-site application in real samples. The recoveries in real water and food samples revealed the excellent environmental tolerance of P-R-CDs, which represented a prospective application utility for quantitative monitoring of Hg 2+ in food and the environment.