Shape Effects on the 2D Self-Assembly of Lithographically Fabricated Nanoparticles

Abstract

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 the liquid-air interface into two-dimensional assemblies. Hexagonal NPs assemble into interlocking hexagonal lattices, exhibiting the highest translational order with a characteristic correlation length (ξ0.5) extending over nine NP building blocks. Square NP assemblies are disordered, characterized by ξ0.5 averaging around three NP units, consistent with the propensity of NPs to slide and form coexisting Λ1 and Λ0 lattices. Pentagonal NP assemblies show six-fold coordination, but do not fully tessellate the plane, yielding anisotropic assemblies with intermediate order and ξ0.5 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.