(521a) Self-Assembly of Nanoparticles at the Liquid-Liquid Interface

Over the course of the past decade there has been what amounts to a paradigm shift in the field of self-assembling colloidal crystallization. This shift has seen the focus of research in colloidal crystallization change from an initial point where the focus of research was concerned with directing nanoscale colloidal objects of a single size and composition to crystallize into a single homogeneous crystals on a mesoscopic scale to the current state of the art, in which the field of colloidal crystallization has become advanced enough to create heterogenous mesoscopic crystals comprised of numerous individual nanoscale objects having different chemical compositions, sizes and shapes with hierarchical structure. These synthetic structures have reached the point at which they now emulate naturally occurring ionic crystal structures and may be on the verge of offering potentially revolutionary advances to nanotechnology.

The creation of such hierarchical organized materials offers insight into interesting future directions for nanoscale science and engineering. Although hierarchically ordered colloidal crystals are interesting for a vast array of applications it may be useful to eventually create nanoscale materials that mimic the advantages and complexities embodied by supramolecular chemistry: self-assembly, hierarchical ordering and spontaneous integration of heterogeneous materials. Directing nanoscale materials, and inorganic nanoparticles in particular, to self assemble with characteristics reminiscent of supramolecular chemistry, however, will require the development of new techniques and materials to address these problems.

One potential arena for the development of such novel techniques is the liquid-liquid interface. Trapping inorganic nanoparticles at the liquid-liquid interface offers the potential to selectively decorate either side of these nanoparticles by performing chemical operations on either bulk phase. The ability to create such “Janus” nanoparticles would be an important step in developing inorganic nanoparticles that mimic supramolecular chemistry.

This talk will focus on recent advances which we have made in trapping inorganic nanoparticles at the liquid-liquid interface and the selective modification of those nanoparticles. By functionalizing gold, silver or magnetite nanoparticles with a ligand having a water contact angle that is 90 degrees, these inorganic nanoparticles can be directed to assemble in to randomly ordered hexagonally close packed arrays at the liquid-liquid interface. Moreover, recent results concerning the selective functionalization of those nanoparticles either trapped at the liquid-liquid interface or through ligand specific interactions will also be discussed.