Plasmene nanosheets assembled from "plasmonic molecules".

Entropy-driven drying-mediated self-assembly of plasmonic nanocrystals (termed "plasmonic atoms") has emerged as a general strategy for fabricating plasmene nanosheets from a wide range of monodisperse nanocrystals. However, extending this approach to binary systems remains challenging due to the complex nanoscale interactions between dissimilar nanocrystal shapes. Here, we introduce a combined enthalpy- and entropy-driven strategy to achieve an orderly mixed two-dimensional (2D) binary nanoassemblies from complementary reacting polymer-ligated nanocrystals. Using nanocubes and nanospheres as model systems, "plasmonic molecules" were first synthesized via enthalpy interactions of different nanocrystals through stoichiometric reactions between complementary grafting polymers. This was followed by an entropy-driven, slow-drying-mediated assembly of "plasmonic molecules". This led to well-controlled binary plasmenes without phase separation. This method could be extended to a diverse range of other building block shapes and size scales. Our methodology indicates a new pathway for 2D nanocrystal assemblies with well-controlled mixing at nanoscale precision.