Silver Nanoparticles Embedded Sulfur Doped Graphitic Carbon Nitride Quantum Dots for Fluorescence Sensing of Mercury Ions in Aqueous Media

Abstract

Graphitic carbon nitride (gCN) quantum dots, in recent years, have captivated immense interest in the field of sensing due to their unique optical and electronic properties. Here, we present a facile synthesis of silver nanoparticles embedded sulfur doped gCN quantum dots (Ag-S-gCN QDs) from thiourea, trisodium citrate, and silver nitrate by a low-temperature thermal treatment. The synthesized Ag-S-gCN QDs, with an average size of 3.7 nm, emitted strong blue fluorescence with a high relative quantum yield of 36.5 %. They exhibited significant stability against photobleaching and high ionic strength. The aforementioned quantum dots, under optimal conditions, were employed for fast, sensitive, and selective sensing of Hg2+ ions in distilled water as well as real water samples. A static quenching mechanism was established from the average lifetime calculation via a time-resolved decay experiment. The presence of silver nanoparticles resulted in a redox reaction with Hg2+ ions via electron transfer from metallic Ag to Hg2+ ions. Moreover, the proposed sensor was anticipated to open up a new avenue for convenient, sensitive, and selective sensing of potentially hazardous Hg2+ ions with substantial results.