Liquid‐Phase Fabrication of Janus 2D Materials: Defect‐Rich MoS₂ Ultrathin Layers Asymmetrically Decorated with Au Nanoparticles

Asymmetrically decorated nanoparticles (NPs), also known as "Janus nanoparticles", possess at least two differently functionalized surfaces. This coexistence results in novel features that surpass the inherited benefits of the initial counterparts. Despite significant advances in spherical morphologies, research on Janus two-dimensional (2D) materials is limited, as fabrication strategies primarily focus on dry deposition techniques. To produce Janus 2D materials in large quantities, solution-based techniques are proposed. However, this approach remains largely unexplored for 2D materials other than graphene and its derivatives, and it yields Janus 2D materials in very low amounts. This study develops a liquid-phase fabrication strategy for the asymmetric decoration of MoS₂ ultrathin layers with gold nanoparticles. This approach builds on previous advances in the asymmetric functionalization of spherical nanoparticles, using SiO₂ microbeads as a masking template. Interestingly, the photoluminescence (PL) spectrum of the processed material is unusually dominated by the B exciton emission. The reported versatile method has proven to be scalable, enabling the production of 2D Janus flakes in appreciable quantities, whether as 1T or 2H-polytypes. Overall, the novel synthetic strategy is highly adaptable and can be extended to a variety of other 2D materials and functionalizing agents.