Pathway-Directed Symmetry of Binary Superlattices Crystallized from Polymer-Tethered Inorganic Nanoparticles

Crystallization of two distinct colloidal building blocks into binary nanoparticle superlattices (BNSLs) offers an innovative strategy for preparing advanced functional materials with integrated and remarkable properties, enabling various applications in optoelectronics, catalysis, and sensing. The symmetries and architectures of binary superlattices critically govern their intrinsic properties and are primarily dictated by thermodynamically stable and favorable structures. However, the construction of kinetically trapped metastable superlattices in nonequilibrium phases remains a formidable challenge. Here, we demonstrate a pathway-directed preparation of BNSLs crystallized from polymer-tethered gold nanoparticles at the two-dimensional interface, where internal symmetries and stoichiometries are readily modulated through thermodynamic and kinetic assembly pathways. Unlike the conventional hexagonal packing found in the lowest-energy state, achieving specific BNSLs with AB6 and AB, stoichiometries requires precisely steering the crystallization process into a kinetically controlled pathway. Moreover, the effective size ratio parameter is proposed to quantitatively evaluate the influence of the effective size of each constituent on the final symmetry of the BNSLs, providing guiding and significant phase diagrams of the acquired architectures. This pathway-controlled approach enables the formation of BNSLs with symmetries challenging to achieve via traditional thermodynamic control, offering possibilities for developing multifunctional superlattice materials.