Black Phosphorus Quantum Dots as the Ratiometric Fluorescence\nProbe for Trace Mercury Ion Detection Based on Inner Filter Effect

Abstract

In\nthis work, a novel ratiometric fluorescence sensor has been\nconstructed for the selective and sensitive detection of Hg²⁺, which is based on the inner filter effect (IFE) of tetraphenylporphyrin\ntetrasulfonic acid (TPPS) toward black phosphorus quantum dots (BP\nQDs). Highly fluorescent BP QDs were successfully synthesized from\nbulk BP by sonication-assisted solvothermal method via a top-down\nroute. In the presence of Hg²⁺, the IFE originating from\nspectral overlap between the excitation of BP QDs and the absorption\nof TPPS is inhibited and the fluorescence of BP QDs is restored. At\nthe same time, the red fluorescence of TPPS is quenched due to its\ncoordination with Mn²⁺. These phenomena result from the\nrapid coordination between Mn²⁺ and TPPS in the presence\nof Hg²⁺, which leads to the dramatic decrease of the absorption\nof TPPS. On the basis of these findings, we design a ratiometric fluorescence\nsensor for the detection of Hg²⁺. The as-constructed sensor\nreveals a good linear response to Hg²⁺ ranging from 1 to\n60 nM with a detection limit of 0.39 nM. Furthermore, the sensing\nassay is applicable to detecting Hg²⁺ in real samples.