New colorimetric and fluorometric chemosensor for selective Hg2+ sensing in a near-perfect aqueous solution and bio-imaging

Carbon dots as rapid assays for detection of mercury(II) ions based on turn-off mode and breast milk

In this research, nitrogen co-doped carbon dots were synthesized by solid thermal method with citric acid used as the precursor of carbon, and melamine as nitrogen source. Such carbon dots show high quantum yield of 44%. Furthermore, the native fluorescence of CDs can be reduced by mercury(II), while other metals had no significant influence on fluorescence intensity. During the study, the optimal parameters were selected, such as pH or time for incubation with analyte. Under the optimal conditions, quenching effect caused by mercury ions was evaluated. It was observed that with increasing mercury concentration, the fluorescence of the carbon dots decreased proportionally. The response was characterized by linearity within the range from 2 to 14 μM. Moreover, the limit of detection was 0.44 μM. It was the first time that human milk was used as a real sample to test the applicability of carbon dots. The study results demonstrated good recovery in the 74-111% range (RSD < 6%) As a novel carbon material, CDs show promise for broader applications in analyzing complicated biological samples.

Tuning the amphiphilicity of terpyridine-based fluorescent probe in water: Assembly and disassembly-controlled H g2+ sensing, removal, and adsorption of H2S

A water-soluble terpyridine-based cationic fluorescent probe (SP-TPy) was synthesized, which emerged with pH-dependent amphiphilicity, resulting in self-assembly and disassembly in aqueous media with the aggregation-induced emission (AIE) property. In neutral water (pH 7.4), a moderate sensing response to Hg²⁺ ions was given by the self-assembly of SP-TPy. However, in acidic aqueous media, the monomer of SP-TPy not only appeared to be highly selective and sensitive for Hg²⁺ ions, but also displayed highly efficient removal of Hg²⁺ ions from solution by rapid precipitation, which was attributed to the coordination-triggered reassembly of SP-TPy. The removal efficiency of SP-TPy for Hg²⁺ was found to be over 99%. Further study indicated that the precipitates were composed of various polyhedral porous frameworks, a property that was further used to adsorb H₂S gas to form HgS complexes with higher uptake capacities. In addition, SP-TPy can be efficiently regenerated and recycled using a simple treatment with acidic water after adsorption of the H₂S gas.