Near-infrared light-driven photoelectrochemical sensor for mercury (II) detection using bead-chain-like Ag@Ag2S nanocomposites

Abstract A near-infrared (NIR) light-driven photoelectrochemical (PEC) sensing platform was established for the quantitative assay of Hg2+ using Ag@Ag2S nanocomposites. Ag2S quantum dots (QDs) with the bead-chain-like nanostructure were fabricated simply via one-step oil-bath route to be further deposited with metallic Ag through the photo-reduction method to yield Ag@Ag2S nanocomposites. It was found that Ag@Ag2S-based sensor could present more than twice larger PEC responses than the Ag2S-based one, due to the synergetic combination of metallic Ag with the surface plasmon resonance (SPR) effects and Ag2S QDs with the NIR-light-irradiated PEC properties. More importantly, the developed PEC sensor could display the photocurrent responses that are selectively inhibited in the presence of Hg2+ by forming Ag-Hg amalgam to accelerate the recombination of photo-induced electron-hole pairs. Under NIR light, it can detect Hg2+ in the concentrations linearly ranging from 0.0010 to 5.0 nM, with a limit of detection of about 0.50 pM. This work may guide a promising combination of Ag2S of NIR QDs with metallic Ag of SPR effects for designing various PEC sensing platforms for the complex environmental monitoring of different heavy-metal ions like Hg2+.