This study explores the structural diversity of binary nanoparticle superlattices (BNSLs) formed by combining semiconducting, metallic, and magnetic nanoparticles. The researchers demonstrate the formation of over 15 different BNSL structures, with at least ten previously unreported. The stoichiometry and packing symmetry of these structures are influenced by the electrical charges on the nanoparticles, which are determined by steric stabilization. The study shows that the variety of BNSL structures is stabilized by a combination of entropic, van der Waals, steric, and dipolar forces. The formation of BNSLs is driven by entropy, as demonstrated by the ability to assemble hard spheres into binary superlattices without specific energetic interactions. However, the observed BNSLs have packing densities significantly lower than the close-packed f.c.c. lattice, suggesting that entropy is not the main driving force. Instead, the opposite electrical charges on nanoparticles create specific affinities between different types of particles, leading to the formation of BNSLs rather than single-component superlattices. The study also shows that the charges on nanoparticles can be tuned by adding surfactants such as carboxylic acids and tri-n-alkylphosphine oxides. This charge tuning allows for the directed self-assembly of BNSLs with specific structures. The researchers demonstrate that the addition of different surfactants can lead to the formation of various BNSL structures, including AB, AB₂, AB₁₃, and others. The study highlights the potential of modular self-assembly at the nanoscale for creating complex structures with programmable physical and chemical properties. The ability to control the charge state of nanoparticles enables the precise engineering of BNSLs, which can be used to design metamaterials with tailored properties. The results demonstrate the importance of understanding the interplay between different forces in nanoparticle self-assembly and the potential of BNSLs for applications in materials science and nanotechnology.This study explores the structural diversity of binary nanoparticle superlattices (BNSLs) formed by combining semiconducting, metallic, and magnetic nanoparticles. The researchers demonstrate the formation of over 15 different BNSL structures, with at least ten previously unreported. The stoichiometry and packing symmetry of these structures are influenced by the electrical charges on the nanoparticles, which are determined by steric stabilization. The study shows that the variety of BNSL structures is stabilized by a combination of entropic, van der Waals, steric, and dipolar forces. The formation of BNSLs is driven by entropy, as demonstrated by the ability to assemble hard spheres into binary superlattices without specific energetic interactions. However, the observed BNSLs have packing densities significantly lower than the close-packed f.c.c. lattice, suggesting that entropy is not the main driving force. Instead, the opposite electrical charges on nanoparticles create specific affinities between different types of particles, leading to the formation of BNSLs rather than single-component superlattices. The study also shows that the charges on nanoparticles can be tuned by adding surfactants such as carboxylic acids and tri-n-alkylphosphine oxides. This charge tuning allows for the directed self-assembly of BNSLs with specific structures. The researchers demonstrate that the addition of different surfactants can lead to the formation of various BNSL structures, including AB, AB₂, AB₁₃, and others. The study highlights the potential of modular self-assembly at the nanoscale for creating complex structures with programmable physical and chemical properties. The ability to control the charge state of nanoparticles enables the precise engineering of BNSLs, which can be used to design metamaterials with tailored properties. The results demonstrate the importance of understanding the interplay between different forces in nanoparticle self-assembly and the potential of BNSLs for applications in materials science and nanotechnology.