The Significance of Multivalent Bonding Motifs and "Bond Order" in DNA-Directed Nanoparticle Crystallization

Multivalent oligonucleotide-based bonding elements have been synthesized and studied for the assembly and crystallization of gold nanoparticles. Through the use of organic branching points, divalent and trivalent DNA linkers were readily incorporated into the oligonucleotide shells that define DNA-nanoparticles and compared to monovalent linker systems. These multivalent bonding motifs enable the change of "bond strength" between particles and therefore modulate the effective "bond order." In addition, the improved accessibility of strands between neighboring particles, either due to multivalency or modifications to increase strand flexibility, gives rise to superlattices with less strain in the crystallites compared to traditional designs. Furthermore, the increased availability and number of binding modes also provide a new variable that allows previously unobserved crystal structures to be synthesized, as evidenced by the formation of a thorium phosphide superlattice.