Surface energy fluctuation effects in single crystals of DNA-functionalized nanoparticles.

Surface  energy is a fundamental material property that determines important functions such as catalytic, sensing, and imaging properties. Over the past century, various experimental studies and models including the broken bond theory and Wulff construction have been developed to analyze surface  free energies. However, it remains a challenge to measure or predict thermal fluctuation effects on surface  energies. In particular, crystals of functionalized building blocks, such as self-assembling proteins and DNA-functionalized nanoparticles, assembled via the specific surface interactions of the building blocks, are highly sensitive to thermal fluctuations. In the case of DNA-functionalized nanoparticles, it has been shown that the crystals are formed as a result of thermally active hybridizations. We show here that the surface  energy along different planes can be obtained from the ratio of hybridization events. The surface  energy fluctuations in these systems are shown to bear a nearly linear correlation with the fluctuations in DNA hybridization events in the bulk. We further demonstrate that short DNA chains and high DNA loading increase the volume density of the DNA sticky ends. The relationship between thermally active hybridizations and surface  energy found here can be used to aid the design of single crystals of functionalized colloids with active surface groups.