Mon, Jan. 9, 2017, 3:15pm - 4:15pm
Frick Chemistry Laboratory, Taylor Auditorium
Phase Transitions and Adsorption at the Atomic and Nanoscale: From Storing and Separating Gases to Manipulating Light
Phase transitions are powerful tools for the design of advanced materials, as small changes in an external signal can lead to large changes in a material’s structure and properties. This is true, for instance, in the design of high-performance adsorbents for the storage and separation of small gas molecules. Improved gas storage and separation processes are critical to the success of many emerging technologies, but progress has been hindered by several fundamental challenges inherent to adsorption in rigid, inert materials. With their high structural and chemical tunability, metal-organic frameworks offer opportunities to circumvent these challenges through the synthesis of new materials featuring productive phase transitions that can be induced by changes in external gas pressure and temperature. Indeed, it will be shown that adsorption-induced phase transitions are directly responsible for record-breaking methane storage and carbon dioxide capture performance in two series of responsive metal-organic frameworks.
Just as responsive metal-organic frameworks lead to new ways of manipulating gas molecules at the atomic scale, responsive nanoparticle superlattices offer new opportunities for manipulating light at the nanoscale. In particular, collective interactions between precisely placed plasmonic nanoparticles in dynamic architectures can manipulate light in unique ways that are both fundamentally interesting and practically useful. Due to their highly tunable structure and sequence-specific interactions, nucleic acids are a powerful class of nanoparticle surface ligands that can be used to program the crystallization of colloidal nanoparticles into structures with precisely defined spacing and symmetry, both in solution and on surfaces. Moreover, nucleic acid bonds between nanoparticles are intrinsically responsive and undergo phase transitions in response to small changes in dielectric constant that allow the distance between nanoparticles to be rapidly tuned. When combined with the DNA-mediated adsorption of nanoparticles in porous supports, this dynamic structural control affords unique plasmonic architectures that function as responsive metamaterials.