Silver nanoparticles embedded sulfur doped graphitic carbon nitride quantum dots: A fluorescent nanosensor for detection of mercury ions in aqueous media

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2022-09, Vol.648, p.129377, Article 129377
• Main Authors: Pattnayak, Samarjit, Sahoo, Ugrabadi, Choudhury, Shubhalaxmi, Hota, Garudadhwaj
• Format: Article
• Language: English
• Subjects: Graphitic carbon nitride; Hg2+ ions; Nanosensor; Quantum dots (QDs); Silver nanoparticles (AgNPs); Static quenching
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2022.129377

Graphitic carbon nitride (gCN) quantum dots, in recent years, have captivated enormous attention in the field of sensing due to their unique optical and electronic properties. We have reported a facile synthesis of silver nanoparticles (AgNPs) embedded sulfur-doped gCN quantum dots (Ag-S-gCN QDs) using thiourea, trisodium citrate, and silver nitrate precursors. The as-prepared quantum dots with an average particle size of 3.7 nm emitted strong blue fluorescence with a relative quantum yield of 36.5%. They exhibited significant stability against photobleaching and high ionic strength. The Ag-S-gCN QDs, under optimal conditions, were employed for fast sensing of Hg2+ ions in 3 min at pH 5. The limit of detection (LOD) and limit of quantification (LOQ) were measured to be 0.13 μM and 0.43 μM, respectively, with a linear range of 0.1–0.6 μM. The average lifetime of Ag-S-gCN QDs was calculated as 7.79 ns from a time-resolved decay experiment. A static quenching mechanism was proposed from the average lifetime calculation accompanied by a redox reaction via electron transfer from metallic Ag to Hg2+ ions. A substantial amount (>85%) of Hg2+ ions in the real water samples were recovered within a relative standard deviation (RSD) of ≤ 5%. The proposed nanosensor was anticipated to open up a new avenue for convenient, efficient, sensitive, and selective sensing of potentially hazardous Hg2+ ions. [Display omitted] •Ag-S-gCN QDs were synthesized by a low-temperature thermal treatment.•The synthesized QDs emitted strong blue fluorescence upon excitation at 380 nm.•The QDs were employed for sensitive and selective detection of Hg2+ ions under optimal conditions.•The sensing performance was due to fluorescence quenching with a LOD of 0.13 μM in a linear range of 0.1–0.6 μM.•Time-resolved decay experiment established a static quenching mechanism.