Layer-by-Layer Interdigitated CuS/Au₂S Heteronanoplates by Selectively Blocking the Pathway of Cation Exchange Reaction

Cation exchange reactions (CERs), recognized as a promising postsynthetic modification strategy, have garnered significant interest for generating thermodynamically unfavorable structural features, such as heterointerfaces. The formation of these heterointerfaces, which exhibit physicochemical properties distinct from those of their individual components, relies on precise control over the diffusion pathways of externally introduced cations as they migrate from the surface into the crystal interior. However, achieving regiospecific modulation of cation diffusion to rationally design heterointerfaces remains a formidable challenge. Herein, we synthesized layer-by-layer interdigitated {CuS/Au₂S}@IrS₂ heteronanoplates (L-Au₂S HNPs), in which Au₂S and CuS are alternately stacked at the atomic scale, using Cu_1.81S@IrS₂ nanoplates (CSIS NPs) as a starting template. This distinct structural arrangement was realized through a two-step CER with Au cations and a phase transformation process from Cu_2-xS to CuS. Experimental results indicate that S-S bonds within phase-converted CuS crystals act as diffusion barriers during subsequent CER, restricting the migration of Au cations into specific CuS layers. Furthermore, theoretical calculations suggest that the expansion of the anion sublattice within channels containing diffused Au cations induces compressive strain in adjacent CuS layers, thereby impeding further Au incorporation. Expanding this synthetic strategy to construct atomic-layer-level stacked heteronanostructures across a broader range of materials could unlock new opportunities for developing advanced materials with unprecedented optical and catalytic properties.