Wrinkled 2H-phase MoS2 sheet decorated with graphene-microflowers for ultrasensitive molecular sensing by plasmon-free SERS enhancement

High surface-enhanced Raman spectroscopy (SERS) activity is ordinarily derived from noble-metal nanoarrays. In recent years, certain two-dimensional (2D) inorganic materials have become suitable for SERS. However, the limits of detection (LODs) of these plasmon-free materials are insufficient for meeting the requirements of molecular analysis. Herein, the centralization of the probe molecule pre-concentration process, and enhancement of interfacial interactions between the substrate and molecules were pivotal accomplishments in the development of a hetero-substrate comprised of a wrinkled semiconducting 2H-phase MoS2 (W-MoS2) platform decorated with graphene-microflowers (GMFs), for the achievement of noble-metal-comparable SERS detection. The GMFs served as supersized molecular enrichers, creating abundant SERS 'active regions', and thus, the LOD in the adsorption equilibrium state was 5 × 10−11 M for rhodamine B (RhB), and the maximum enhancement factor (EF) was 2.96 × 107. Additionally, performance degradation of GMFs/W-MoS2 was below 6 %, following long-term detection over 50 days. The sub-nanomolar sensitivity of the GMFs/W-MoS2 substrate can be attributed to the synergistic effects of the efficacious pre-concentration of probe molecules, enhanced charge-transfer, and multiple light scattering, all of which can promote the progress of plasmon-free SERS detection.