DNA-functionalized nanoparticles (NPs), also known as “programmable atom equivalents” (PAEs), can be assembled into deliberately designed colloidal crystals with control over phase symmetry, lattice parameter, and crystal habit by leveraging the sequence-specific recognition of their oligonucleotide ligands. Recent studies have shown that a novel phenomenon, colloidal crystal metallicity, emerges when there is a large size disparity (e.g., 1.4 nm vs 10 nm) between NPs functionalized with complementary DNA. Here, the smaller NPs behave as electron equivalents (EEs) and can roam through and stabilize the sublattice defined by the larger PAEs. However, studying how DNA architecture (e.g., EE valency) affects the properties of colloidal crystals has been challenging, as there is inherent polydispersity in the number of DNA strands on these NPs. Here, we present a strategy to synthesize colloidal crystals using well-defined molecular entities functionalized with a precise number of DNA strands, ranging from two to eight. When these molecular EEs are assembled with complementary AuNP-based PAEs, three distinct “metallic” phases can be obtained. We found that the thermal stability of these colloidal crystals is dependent on EE valency, while their lattice symmetry is controlled by the total number of EE sticky ends on the PAEs. In addition, when compared to Au-EEs, molecular EEs diffuse across the solution-superlattice interface faster, highlighting their delocalized nature and electron-like character in colloidal crystals. Taken together, this work introduces the concept of defined valency in EEs and provides a new route to study colloidal crystal metallicity.

Colloidal crystal engineering using electron equivalents with defined valency

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.