About the Seminar
"Single Molecule Probes and Single Particles Probed"
I will describe two projects in which we characterize complex systems – supercooled liquids and conjugated polymer aggregates – through single molecule or single particle fluorescence imaging. First, in supercooled liquids – systems that display behaviors consistent with the presence of heterogeneous dynamics – we investigate the time scales over which heterogeneities persist using “ideal” single molecule fluorophores. We show that two supercooled liquids, one composed of small molecules and one of polymers, are ergodic down to the glass transition temperature. These studies also reveal the range of time scales over which, for example, fast molecules become slow and vice-versa as well as how these time scales vary with temperature. While in supercooled liquids single molecule fluorophores serve as guest reporters of the surrounding host, to interrogate conjugated polymers we have developed single molecule and single particle techniques using emission from the molecules of interest themselves. First, we employ super-resolution techniques to localize individual emitters along prototypical single conjugated polymers, revealing that molecules with compact conformation have distinct photophysical properties from those with extended conformation. Towards understanding photophysical behavior of such molecules in the context of their environment as it exists in devices, we develop a multi-modal approach in which we can elicit and monitor bottom-up growth of aggregates from single chains. Real time monitoring of the aggregates during growth demonstrates that aggregate assembly occurs through multiple mechanisms that have distinct and strong impact on the evolution of physical and optical anisotropy of the aggregates.
About the Speaker
Laura Kaufman graduated summa cum laude from Columbia University in 1997 with a B.A. in Chemistry and English. She earned her Ph.D. in Chemistry in 2002 from the University of California, Berkeley. There, Laura worked on multi-dimensional Raman spectroscopy of simple liquids in the laboratory of Professor Graham R. Fleming. She went on to do postdoctoral work at Harvard University under the guidance of Professors X. Sunney Xie and David A. Weitz, where she used CARS microscopy to study colloidal glasses and cell migration in three-dimensional environments. Laura has been named a NYSTAR Young Investigator, a Beckman Young Investigator, a Camille Dreyfus Teacher Scholar, and a Lenfest Distinguished Faculty Member. Her laboratory is highly interdisciplinary and focuses on the dynamics of complex, crowded systems. In particular, the laboratory studies heterogeneous dynamics in supercooled liquids with single molecule imaging, exciton diffusion in conjugated polymers at the single molecule and aggregate level with single molecule spectroscopy, the mechanical properties and structure of biopolymer gels using rheology and microscopy, and cancer cell invasion in tissue approximations of tailored architecture.