Au/SnS2 Hybrid Quantum Dots for Surface-Enhanced Raman Scattering-Based Monitoring and Photoreduction of Hg (II) Ions

Mercury ions, one of the most toxic heavy metals, have long been a source of concern due to the serious hazards they pose to human health and the environment. Hence, developing a swift and sensitive method for monitoring these ions to the lowest detection level is critical. In this work, we develop simple surface-enhanced Raman scattering (SERS)-active gold-functionalized SnS 2 quantum dots (Au/SnS 2 QDs) that can detect and photodegrade Hg 2+ ions under visible light irradiation. Crystal violet (CV) dye is used as the indirect Raman probe for SERS detection at an excitation laser of 532 nm. The Au hybrids show enhanced SERS activity compared to that of pristine-SnS 2 owing to the dual effect of electromagnetic and chemical enhancement. The detection limit of Au/SnS 2 toward Hg 2+ is found to be 1.05 ng/mL. A “turn-off”-based SERS mechanism is explained in Au/SnS 2 QDs, in which the high affinity of Au toward Hg 2+ and the strong Lewis acid–base interaction between Hg 2+ and S 2– of SnS 2 play a pivotal role. The substrates further show self-cleaning ability by degrading both probed CV and analyte Hg 2+ under visible light irradiation with a catalytic load of 0.5 mg/mL. The reproducibility, selectivity, recovery, and stability of the SERS substrate were examined on a natural lake water sample spiked with Hg 2+ ions. The work demonstrates notable prospects in the fields of SERS and photocatalysis, paving the way for potential detection and treatment of environmental pollutants using noble metal/semiconductor hybrids.