WS2 Nanosheets Modified with Ag Nanoparticles as Visible-Light Photocatalysis for Hot-Electron-Mediated Plasmonic Charge Transfer in the Degradation of Textile and Pharmaceutical Waste

Two-dimensional (2D)-layered nanostructures integrated with plasmonic nanostructures have drawn huge attention for their potential applications in environmental remediation and water detoxification. In this study, silver (Ag) nanoparticles attached with a few layers of tungsten disulfide (WS2) nanosheets were synthesized using liquid-phase exfoliation followed by a hydrothermal method for water remediation applications. The attachment of Ag nanoparticles (∼42 nm) over the WS2 layers enables the effective band gap narrowing and reduction in recombination rate in WS2 due to the generation of a Schottky junction formation at the interface of Ag and WS2 layer, which is beneficial in boosting the photodegradation performance. In addition, improved visible-light absorption owing to the surface plasmon resonance effect significantly contributes to improving the photocatalytic activity of Ag-WS2 nanohybrids. The optimized Ag-WS2 nanohybrid (0.5 mg/mL) exhibited boosted photodegradation capability, effectively decomposing 10 μM of methylene blue (MB), 10 μM of methyl orange (MO), and 1 mg/mL of oxytetracycline hydrochloride (OTC-HCl) within 60, 40, and 60 min sequentially, which correspond to 3.2, 4.0, and 3.4 times higher photocatalytic activity than pristine WS2 nanosheets. First-principles density function theory ensures that Ag nanoparticle attachment has a significant shift in the electronic structures and improves the effective charge transfer, which are in good agreement with the experimental results. Although few studies have examined plasmonic-WS2 nanohybrids for photocatalysis, this study demonstrates the optimization in plasmonic content loading, in-depth exploration of charge transfer mechanisms, and their direct correlation with photodecomposition performance, which is essential to achieving advancement in this field.