Two-dimensional transition metal dichalcogenides (TMDCs) present a unique opportunity as Surface Enhanced Raman Scattering (SERS) substrates due to their superior optical properties. Here, vertically oriented tungsten disulfide (WS₂) flakes were synthesized on a silicon (Si) substrate using the pulsed laser deposition (PLD) technique. The WS₂ flakes were employed as SERS substrates for detecting low concentrations of environmental pollutants, like Rhodamine B (RhB) and Methyl Orange (MO) dyes, achieving promising enhancement factors of approximately 10⁷ with a 532 nm excitation laser. To further enhance the plasmonic activity of the vertical WS₂ flakes, silver nanoparticles (NPs) were decorated on their surface via thermal evaporation. The Ag NP-functionalized WS₂ flakes exhibited superior detection capabilities compared to pristine WS₂ flakes, achieving remarkable sensitivity at ultralow concentrations of 10⁻¹⁶ M for RhB and 10–17 M for MO dye, with enhancement factors of the order of 10⁸. The SERS performance of the WS₂-Ag substrate was also evaluated using a 633 nm laser, successfully detecting Methylene Blue (MB) dye at an ultralow concentration of 10⁻¹³ M. Prolonged exposure to RhB, MO, and MB dyes can cause cancer, neurotoxicity, and respiratory irritation. Thus, sensitive detection of these dyes at ultralow concentrations is highly crucial. A charge transfer mechanism between WS₂ and RhB dye molecules is proposed, along with the contribution of Ag NPs, to explain the enhanced detection capabilities of the nanocomposite SERS substrate.
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