A Fluorescent Sensor Based on P-Doped Biomass Carbon Quantum Dots for Selective Detection of Hg²⁺

The pollution problem caused by mercury ions (Hg 2+ ) is becoming increasingly serious, and it is imperative to establish a methodology that is tailored to the precise identification of Hg 2+ . Phosphorus-doped biomass carbon quantum dots (P-BCQDs) with cyan fluorescence were synthesized via a hydrothermal approach, utilizing willow leaves as the carbon precursor and sodium pyrophosphate as a modifying agent. The morphology and optical properties of P-BCQDs were analyzed, and the results showed that P-BCQDs had a spherical structure, uniform dispersion, and particle size at 2.0±0.5 nm. Based on the principle that P-BCQDs bind to Hg 2+ to burst the fluorescence, the P-BCQDs have an optimal time of 2 min for the detection of Hg 2+ , and the optimal pH = 7, with c Hg2+ ranging from 0–20 μ mol/L. The linear relationship was achieved with the detection limit of 9 nmol/L. The spiked recovery experiments were conducted in actual water samples. The recoveries exhibited a range of 95.0% to 105.0%, accompanied by Sr ranging from 1.6% to 2.8%, which indicated that the proposed methodology is applicable for the quantification of Hg 2+ .