Synergistic Resonance‐Enhanced Plasmon‐Free SERS in Few‐Layer Manganese Phosphorus Trichalcogenide

Abstract Surface‐enhanced Raman scattering (SERS) is widely employed due to its ultra‐high sensitivity, non‐destructive nature, and ability to provide label‐free molecular fingerprint information. In this work, a novel semiconductor‐based SERS substrate, 2D metal phosphorus trichalcogenides (2D‐MPTs) is proposed, and a new “synergistic resonance” effect is introduced to maximize chemical mechanism (CM)‐driven SERS performance via alloy engineering. By precisely tuning the energy levels of Mn _1−x Ni _x PS ₃ (0 ≤ x ≤1) alloys, the optimized Mn _0.73 Ni _0.27 PS ₃ substrate demonstrates remarkable SERS sensitivity, with an enhancement factor of 1.4 × 10 ⁵ and a detection limit as low as 1.0 × 10 ⁻⁹ mol L ⁻¹ for rhodamine 6G (R6G). This outstanding performance is attributed to the synergistic contribution of: i) strong adsorption capability and efficient charge transfer (CT) between the semiconductor substrate and analytes, and ii) maximized excitation‐resonance‐facilitated CT coupled with molecular‐resonance‐facilitated CT. Overall, this work advances the understanding of CM and offers a pathway for designing highly effective semiconductor SERS substrates.