Highly stable and uniform colloidal silver quantum dots stabilized with (N,S,O) donor ligand: Selective sensing of Hg(II)/Cu(II) and I- ions and reduction of nitro-aromatics in water

The present paper showed the role of ligand in the effective stabilization of colloidal silver-quantum dots (Ag-QDs) and their applications for the colorimetric detection of metal ions/anions. Furthermore, the Ag-QDs have been explored to reduce nitroaromatics, industrial waste and pollutants. The donor atoms such as (N,S,O) present on ligands have been found to stabilize the Ag-QDs in the colloidal state effectively, and the pendant alkyl chain governs their uniform dispersion. The QDs (size ti 5 nm) are highly stable and can be kept in the colloidal state without aggregation for months under ambient conditions. The Ag-QDs showed naked-eye colorimetric sensing of Hg(II)/Cu(II) and I- ions selectively over other ions at very low concentrations. The colorimetric change has been attributed due to cation and anion-mediated aggregation of QDs. Furthermore, these QDs have also been found effective for reducing various nitroaro-matics into valuable amines in a very short time and showed first-order kinetics with the calculated rate of 0.1352 min -1. The Hammett plot suggests that the reaction rate depends on the groups present at the para-position to the nitro group with a negative slope of -1.291 which indicates that the reaction is pro-ceeding via the formation of a cationic intermediate. The results described in this paper will be the pio-neer in the field of designing of new ligands for the effective stabilization of metal nanoparticles in the colloidal state without altering their activity.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

The paper presented the role of ligands in stabilizing colloidal silver-quantum dots (Ag-QDs) and their applications in colorimetric detection of metal ions/anions. The Ag-QDs were also used for reducing nitroaromatics and showed selective colorimetric sensing of Hg(II)/Cu(II) and I- ions. The results suggest that the ligands with donor atoms effectively stabilize the Ag-QDs and the pendant alkyl chain governs their dispersion, while the colorimetric change is attributed to ion-mediated aggregation of QDs.