Femtomolar‐Level Molecular Sensing of Monolayer Tungsten Diselenide Induced by Heteroatom Doping with Long‐Term Stability

Abstract Surface‐enhanced Raman scattering (SERS) is a sensitive, fast, and nondestructive technology to detect trace amounts of molecules. The development of ultrasensitive and environmentally stable noble‐metal‐free SERS substrates is crucial for practical applications but still very challenging. In this contribution, an in situ substitutional doping strategy to synthesize Re‐doped WSe₂ (Re‐WSe₂) with different doping levels is reported. By increasing the Re content to ≈50 at%, the Re‐WSe₂ alloy inherits the 1T″ phase of the ReSe₂ lattice. Furthermore, Nb atoms are doped into the 1T″ Re‐WSe₂ alloy to further modulate its electronic structure. The as synthesized 1T″ Nb, Re‐WSe₂ demonstrates a femtomolar‐level molecular sensing capability with a detectable concentration of 5 × 10^–15 m and the corresponding enhancement factor is 2.0 × 10⁹, which is superior to that of most non‐noble‐metal SERS substrates and comparable or even superior to that of noble‐metal substrates to the best of the authors’ knowledge. More importantly, the as‐synthesized 1T″ Nb, Re‐WSe₂ exhibits excellent air‐stability over a long term (≈6 months) and selective detection capability in the mixed molecular solution, which are essential for their practical applications. The work provides a new strategy for the rational design of noble‐metal‐free SERS substrates to achieve ultrasensitive molecular sensing.