Controlling Phases of Isotropic DNA-grafted Nanoparticle Assembly through Tuning Pair Interactions

Theoretically, complex isotropic pair potentials can yield complex periodic structures, but due to limited practical methods to engineer pair potentials, experimental realization remains challenging. DNA can direct self-assembly in a tailorable manner by leveraging complementary base pairing and repulsive polymeric effects, presenting a material well-suited to encoding designed pair potentials. We utilize a double-linker approach to DNA-grafted NP assembly; linkers have a non-complementary spacer and a hybridization sequence that is complementary to the linker of a paired particle. Complementary regimes drive attraction causing DNA shells to hybridize at an encoded distance (r_att) prescribed by shell length and location of the hybridization regime. Non-complementary regimes drive particle repulsion, the range of which (r_rep) is prescribed by shell length alone. Computational simulations show that isotropic pair potentials are effectively approximated with the parameter: r_rep/r_att. By fixing either linker length or hybridization regime location and altering the other, we achieve a range of r_rep/r_att values, and we validate, via small-angle x-ray scattering, structural evolution from body-centered cubic to simple cubic crystals to weakly ordered cubic diamond-like networks.