Shape effects on the 2D self-assembly of lithographically fabricated nanoparticles

We fabricate and polymer ligate square, pentagonal, and hexagonal nanoplates and investigate the effect of nanoparticle (NP) shape on the self-organization of their dispersions at a liquid-air interface into two-dimensional assemblies. Hexagonal NPs assemble into interlocking hexagonal lattices, exhibiting the highest translational order with a characteristic correlation length (<i>ξ</i>_0.5) extending over nine NP building blocks. Square NP assemblies are disordered, characterized by <i>ξ</i>_0.5 averaging around three NP units, consistent with the propensity of NPs to slide and form coexisting <i>Λ</i>₁ and <i>Λ</i>₀ lattices. Pentagonal NP assemblies show six-fold coordination, but do not fully tessellate the plane, yielding anisotropic assemblies with intermediate order and <i>ξ</i>_0.5 of about seven NP units. In binary NP assemblies, mixed pentagonal and hexagonal NP assemblies with shared six-fold coordination show greater ordering in comparison to assemblies of square and hexagonal NPs.