28 Apr
2015
28 Apr
'15
10:06 a.m.
Please post and forward to your group(s).
Joint Seminar: Physical Chemistry and Center for Excitonics
Navigating Space-Time with Ultrafast Exciton Photolithography or Scintillating Near-fields
to Follow Dynamic Processes in Molecular Materials
May 5, 2015 at 4:30pm/ rm: 4-370
Naomi Ginsberg
University of California/Department of Chemistry and Physics
[nsginsberg]
abstract:
A cross-cutting theme in my research group is to examine dynamic processes in
spatially-heterogeneous condensed phase molecular materials over a wide range of time
scales. I will share recent results in multiple areas, all underpinned by the strong
correlation between physical structure and the optical properties of materials. Our
investigations often require tailoring the spatial and temporal resolution of our
measurement approaches. I will explain how by measuring the ultrafast electronic
properties of heterogeneous, ‘printed’ semiconducting films of small organic molecules we
infer the much slower dynamics by which complex nanoscale structural motifs in the films
emerge when they self-assemble in an evaporating solvent. These studies reveal the
generation of non-equilibrium nanoscale structures that arise from coupling the dynamics
of fundamental phase transformation processes of solute crystallization with solvent
evaporation. They also pinpoint the challenges associated with developing high carrier
mobility materials for printed plastic electronics.
The migration of Frenkel excitons, tightly-bound electron-hole pairs, in organic and
hybrid organic-inorganic semiconducting films is critical to the function of many next
generation optoelectronic devices. While these materials can exhibit a high degree of
structural heterogeneity on the nanoscale, traditional measurements of exciton diffusion
lengths are performed on bulk samples. Since both the characteristic length scales of
structural heterogeneity and the reported bulk diffusion lengths are typically smaller
than the optical diffraction limit, I will describe how we adapt far-field
super-resolution fluorescence imaging to determine in-situ exciton diffusivities and to
uncover the correlations between the structural and energetic landscapes that the excitons
explore. Motivated by the need to observe the dynamics of biomolecular interactions on
their characteristic length scales, I will also show how we have appropriated the
nanoscale resolution of electron microscopy and the near-field luminescence properties of
scintillating oxide films to non-invasively image soft materials that cannot be
interrogated directly with a damaging electron beam. In addition to focusing on soft
materials in organic electronics and biology, I will also demonstrate this new imaging
modality applied to plasmonic nanostructures.
bio:
Naomi Ginsberg received a B. A. Sc. from the University of Toronto (Engineering Science)
(2000) and a Ph.D. from Harvard University with the Physics – Hau group (2007). From
2007 – 2010, she was a Postdoctoral Fellow in the Physical Biosciences Division-Fleming
group at the Lawrence Berkeley National Laboratory. Awards include UC Berkeley
Department of Chemistry Teaching Award (2013), DARPA Young Faculty Awardee (2012), Packard
Fellow for Science and Engineering (2011), and Cupola Era Endowed Chair in the College of
Chemistry (2010-2012). Her group focuses on visualizing ultrafast energy flow in natural
and artificial light harvesting systems and on combining electron and optical microscopies
to facilitate high-resolution studies of living things and molecular interactions in
solution. Naomi’s background in chemistry, physics, and engineering has led her to
observe coherent and previously obscured energy transfer in light harvesting complexes
from plants, to develop polarization techniques in ultrafast multidimensional spectroscopy
to extract structure from electronically-coupled systems, to slow, stop, and store light
pulses in some of the coldest atom clouds on Earth, and to discover, follow, and
understand the interactions of superfluid nonlinear excitations.
