Contraction and Expansion of Stimuli-Responsive DNA Bonds in Flexible Colloidal Crystals*

Abstract

DNA surface ligands can be used as programmable “bonds” to control the arrangement of nanoparticles into crystalline superlattices. Due to their highly tunable structure and sequence-specific interactions, nucleic acids have emerged as powerful surface ligands to direct the assembly of nanoparticles into one-, two-, and 3D colloidal crystals. To evaluate the effect of nanoparticle size on the ability of ethanol (EtOH) to modulate DNA bonds, crystals were similarly prepared using 15 nm diameter spherical programmable atom equivalents (PAEs). While in situ small-angle X-ray scattering experiments indicate that the superlattice undergoes a similar phase transition in response to EtOH, the crystallinities of the contracted phases are reduced compared to those of the 30 nm PAEs. All-atom molecular dynamics simulations were performed to gain additional insight into the mechanism of the EtOH-induced superlattice contraction.