Vertically-aligned 1T/2H-MS2 (M = Mo, W) nanosheets for surface-enhanced Raman scattering with long-term stability and large-scale uniformity

Two-dimensional (2D) materials have recently attracted abundant interest as cost-effective surface-enhanced Raman scattering (SERS) substrates for precise molecular monitoring. However, the challenge of large-area substrate production with high stability and uniformity still imposes unavoidable barrier of 2D materials for practical applications. In this work, we show that large-scale MS2 (M = Mo, W) vertical nanosheets with mixed 1T/2H phases on metal foils as SERS substrates can be fabricated by a simple and low-cost route. We find that the detection limits of MoS2 and WS2 can be up to 5 x 10(-8) M for Rhodamine 6G (R6G), which are much lower than those of most semiconductor SERS substrates. Moreover, the recyclable and scalable substrates provide excellent uniformity and reproducibility on the whole substrates (3 x 4 cm(2)), and the Raman signals keep unchanged after 30 days. The excellent SERS performance is contributed by the high content of 1T phase and 1T-2H heterostructures that significantly improve the charge transfer process, and rich edges that enable sufficient interaction with the interested molecules. Our findings offer potential candidates for practical applications in the food security field and provide insight to design novel SERS substrates.