Thursday, November 12, 2015: 8:45 AM
Canyon B (Hilton Salt Lake City Center)
Inter-particle interactions between nano- and micro-particles can be tuned by DNA functionalization of the particles to guide their assembly into complex two- and three-dimensional structures. Most studies, so far, have focused on realizing novel three-dimensional structures based on nanoparticle assembly, whereas progress on the rational design of DNA-mediated interactions to create useful two-dimensional structures of micron-sized particles has been rather slow. We have developed a comprehensive design strategy based on statistical mechanics and molecular simulation to guide the 2D assembly of micro-particles into diverse crystal structures. Our approach combines the knowledge about inter-particle interactions with lattice energy predictions as well as detailed molecular dynamics simulations to arrive at a structural ordering diagram, constructed as a function of variables related to DNA sequence and composition. To test these predictions, laboratory experiments have been performed with 1.5 um silica particles, functionalized with single-stranded DNA using silanization and cyanuric chloride chemistry. To modulate the relative attractive iner-particle interactions, particles were functionalized by a tailored mixture of two different, partially complementary DNA strands (αDNA and βDNA). We demonstrate that attractive interaction strength can be tuned by controlling particle 'flavoring' via control of the ratio of βDNA with respect to αDNA (Φβ). As a result, using optical microscopy, we observe particles arranged in square, pentagonal and hexagonal structures, which are also compositionally ordered in desirable honeycomb and Kagome lattices. Our approach can be easily extended to enrich the diversity of two-dimensional crystal structures that can be formed using DNA-mediated assembly, and also can be used to provide a more fundamental understanding of nanoparticle assembly in three dimensions.