"Turn-on-off" Fluorescent Probes Based on Carbon Nanoparticles for Hypochlorite and Fe Detection.

The identification of ClO and iron ions in water medium is a difficult task and has been one of the hot issues in analytical chemistry. For this objective, we synthesized carbon nanoparticles (CNPs) through a solvothermal reaction between 1, 3, 5-trimesic acid and o-phenylenediamine, which served as a sequential fluorescent probe for ClO and Fe ions. The obtained CNPs were spherical particles with a diameter of 26.5 nm, exhibiting excellent fluorescence stability under a wide pH range, high ionic strength, and UV irradiation. Interestingly, the fluorescence of CNPs was selectively enhanced in the presence of ClO, and the resultant enhanced emission was extremely quenched by Fe. In view of this, a "turn-on-off" fluorescent probe was established, which possessed wonderful sensitivity and selectivity for quantitative analysis of ClO and Fe, with corresponding detection limits of 0.15 µM and 0.088 µM, respectively. In addition, the practicality and viability of the developed probe were validated by quantifying ClO and Fe in tap water and river water.