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Physical Chemistry Seminar: Professor Naomi Ginsberg, UC Berkeley

Naomi Ginsberg
Date
Tue June 4th 2024, 3:00 - 4:00pm
Location
Sapp Center Lecture Hall 114

About the Seminar 

Following and controlling formation and function of bottom-up assembled materials

Short-range-interacting particles can in principle crystallize via so-called non-classical pathways invoking a metastable liquid intermediate, yet non-equilibrium gelation often occurs before a metastable liquid can form. Using in situ X-ray scattering, we nevertheless watch electrostatically stabilized colloidal semiconducting nanocrystals self-assemble into long-range-ordered superlattices via this non-classical pathway and show how the pathway increases the rate of crystallization over that of direct crystallization from the colloidal phase. Furthermore, by mapping the phase behavior and kinetics as a function of nanocrystal density and electrostatically tuned driving force for assembly, we demonstrate a highly unusual degree of control of a nanoscale system. This control is exemplified by varying the self-assembly rate by over three orders of magnitude, along with predictive control of superlattice yield, size, and crystallinity. Most strikingly, we reveal that this non-classical pathway increases crystallinity of the superlattice simultaneously with the crystallization rate. To further elucidate the elusive nature of the short-range interactions at the nanoscale, we also study the microscopic fluctuations of colloidal suspensions and liquid droplets of the nanocrystals via free-electron laser MHz X-ray photon correlation spectroscopy (XPCS). We discover that the dynamic solvation shell of the nanocrystals suppresses self-diffusion in the liquid state, pointing to unusual hydrodynamic effects and properties that deviate significantly from those of typical liquids. We also find that laser absorption reversibly alters the growth of the ordered superlattice phase and intend to leverage this finding to infer strategies to self-assemble more common low-dielectric nanocrystals into ordered structures by driving them far from equilibrium with optical excitation.

Energy transport in these and other materials is an important emergent property to also characterize at the nanoscale, especially since the solids created often still contain nanoscale heterogeneities. Time-permitting, I will therefore also share recent advances in detecting, tracking, and discerning the spatiotemporal evolution of charge carriers, excitons, heat and ions as they interconvert and explore emerging materials’ structure and heterogeneity on multiple scales. I will share our development of sub-picosecond and single-digit nanometer sensitivity stroboscopic optical scattering microscopy (stroboSCAT) through a series of examples of increasing complexity.

About the Speaker

Naomi S. Ginsberg is a Professor of Chemistry and Physics at University of California, Berkeley and a Faculty Scientist in the Materials Sciences and Molecular Biophysics and Integrated Imaging Divisions at Lawrence Berkeley National Laboratory, where she has been since 2010. She currently focuses on elucidating electronic and molecular dynamics in a wide variety of soft electronic and biological materials by devising new electron, X-ray, and optical imaging modalities to characterize dynamic processes at the nanoscale, as a function of their heterogeneities and over a wide range of time scales. Naomi received a B.A.Sc. degree in Engineering Science from University of Toronto in 2000 and a Ph.D. in Physics from Harvard University in 2007, after which she held a Glenn T. Seaborg Postdoctoral Fellowship at Lawrence Berkeley National Lab. Her background in chemistry, physics, and engineering has previously led her to observe initiating events of photosynthesis that take place in a millionth billionth of a second and to slow, stop, and store light pulses in some of the coldest atom clouds on Earth. She is the Berkeley lead of STROBE, a multi-university NSF Science and Technology Center devoted to imaging science, a member of the Kavli Energy Nanoscience Institute at Berkeley, and the recipient of a David and Lucile Packard Fellowship in Science and Engineering (2011), a DARPA Young Faculty Award (2012), an Alfred P. Sloan Foundation Fellowship (2015), and a Camille Dreyfus Teacher-Scholar Award (2016) in addition to a series of teaching awards in the physical sciences and the campus-wide Carol D. Soc Distinguished Graduate Student Mentoring Award (2022). In 2017-18 she was a Miller Professor for Basic Research in Science at UC Berkeley and was designated a Kavli Fellow. In 2019 she was the Kroto Lecturer in Chemical Physics at Florida State University. She is the recipient of the 2020 ACS Early-Career Award in Experimental Physical Chemistry and became a Fellow of the American Physical Society in 2021.

Host: Fang Liu