Center for Functional Nanomaterials Seminar

DNA-programmed colloidal assembly offers a unique tool for controlling the range and magnitude of interparticle interaction to promote novel crystal formation. We have developed a novel swelling/deswelling technique to make sterically stable DNA-grafted micron-sized colloids, where PEG chains provide this steric stability. These particles show temperature dependent phase behavior and they also aggregate/dissociate reversibly with temperature. We find that crystals only form in a rather narrow range of temperatures and have acceptably fast nucleation and growth in a small range of grafted-DNA density. In addition, we study phase behavior of binary alloy solid solutions using these particles. A competition between DNA single-base mismatches is used to create energy penalties for the substitution of a few KBTs’. The minority species substitute into the crystal lattice when the pair interaction difference is a fraction of a KBT, however, they are excluded from the growing crystal when the pair interaction difference becomes larger. Finally, we describe the assembly of binary dispersions of DNA-particles, with different size ratios, into close-packed alloy structures such as NaCl and CsCl. Confocal microscope is used to image different slices of the fixed/solvent swapped structures to obtain the crystallography of the assembled structures.