(749a) Diverse Colloidal Crystals from DNA-Grafted Spheres Via Self-Assembly

DNA-grafted colloids are advantageous in making different structure colloidal crystals through self-assembly. In our lab, diverse crystal structures including CsCl, CuAu, NaCl, NiAs, Cu3Ti, NbP, α-IrV, intermedium between different crystal types and partially transformed crystals are prepared through a slowly quenching method, in which temperature goes down as 0.4 degree per hour. Specifically, we coat certain type DNA on to the polystyrene (PS) beads of various sizes through a swelling and deswelling method. At the same time, another type DNA is coated on to another batch of PS particles that the two type DNA on each particle species could be bond via linker. The DNA type on certain kind PS particles could be either pure or some combinations of the two. We mix two type particles at a certain volume ratio, heat them 5 degrees above the melting temperature of the DNA strands, and then slowly quench them. After the quench, we get nice crystals with good crystallinity which can be observed under optical microscope. By changing the stoichiometry of the two type particles, particle size ratios, as well as the composition of DNA strands on each type particles, we are able to explore new ways of making diverse structure colloidal crystal and get multiple types of crystals in the same sample. Furthermore, the transformation patterns and paths between some crystal types are discussed and mechanisms are well studied. To analyze the crystal structures and measure the exact lattice spacing and bond angles, crystallography can be studied via confocal microscopy.