Surface-enhanced Raman effect on MoS₂–WS₂ composite structures

The extensive application of SERS requires a reduction in complexity and difficulty in substrate preparation. Here, the study proposes a simple yet effective technique for the synthesis of few-layered MoS₂–WS₂ composite structures and highlights the potential of these nano-composites as low-cost SERS substrates. A highly fluorescent dye, Rhodamine 6G (R6G) has been employed as a probe. A better enhancement ability was observed for the MoS₂–WS₂ nano-composite structures and a series of R6G signature peaks can be detected even down to 10^–7 M concentration. The presence of surface roughness due to the formation of multiple inter- and intra-flake heterojunctions may provide a larger contact area between the substrate and the probe. Hence, the improved enhancement is probably due to the higher adsorption of the R6G molecules on the nano-composites and the effective charge transfer between them. Additionally, the detection ability of the MoS₂–WS₂ composite structures was sustained over a long period after storing the same at room temperature. The study provides a new incentive for metal-free low-cost SERS sensing by engaging 2D materials.