Shape-complementary co-assembly of concave nanocubes and nanospheres into binary superlattices

The controllable co-assembly of nanoparticles into binary superlattices (SLs) has attracted significant interest since it provides enhanced structural and compositional tunability, offering opportunities to engineer superlattice properties and realize multifunctionality. However, it remains challenging to develop an efficient co-assembly strategy to realize the facile construction of binary SLs with tunable compositions and structures. Here, we report the shape-complementary co-assembly of concave gold nanocubes (cGNCs) and gold nanospheres (GNSs) into highly ordered binary SLs. Micrometer-sized 2D and 3D GNS-cGNC binary SLs with a NaCl-type structure were produced when the sizes of the GNSs and cGNCs were matched, whereas 2D tetragonal and hexagonal binary SLs were obtained at varied size ratios of the GNSs and cGNCs. The unique combination of nanospheres and concave nanocubes endows the GNS-cGNC binary SLs with rich nanogaps and tips, leading to a high density of hot spots. The obtained 2D GNS-cGNC binary SLs exhibited excellent surface-enhanced Raman scattering performance, achieving a detection limit of 10^-12 M for crystal violet. Furthermore, PbS nanospheres were used as alternative convex building blocks to GNSs for co-assembly with cGNCs into a binary PbS-Au SL, and the selective etching of PbS in the binary SL produced a checkerboard SL of cGNCs. This work presents a facile and versatile shape-complementary co-assembly strategy for the construction of tunable binary SLs, opening an avenue for creating multicomponent SLs with tailored structures and properties.