RSS FeedUpcoming EventsDesigning Advanced Nanocatalysts by Looking at Atoms and Molecules on Reactive Surfaces: Nano Seminar series, March 22https://events.berkeley.edu/BNNI/event/237676-designing-advanced-nanocatalysts-by-looking-at

Clarification of the nature of active sites at both solid-gas and solid-liquid interfaces has been a long-standing question in surface chemistry, holding paramount significance in crafting innovative catalytic materials that demand minimal energy consumption. A bimetallic Pt alloy, or mixed catalyst, is an excellent platform to uncover the contentious role of the metal–metal oxide interface because the alloyed transition metal can coexist with the Pt surface layer in the form of an oxidized species on the bimetal surface during catalytic reactions. The real-time imaging of catalytically reactive atomic sites using operando surface techniques, including ambient pressure scanning tunneling microscopy, can reveal the nature of reactive sites on the catalytic surfaces.

In this talk, I present in-situ observation results of structural modulation on Pt-based bimetal catalysts and mixed catalysts and its impact on the catalytic activity. We utilized PtNi, and PtCo that includes both single crystal and nanoparticle surfaces as model catalysts, and showed the coexistence of Pt and metal oxide leads to the enhancement of catalytic activity, indicating these metal-oxide interfaces provide a more-efficient reaction path for CO oxidation. The mixed catalysts composed of Pt nanoparticles and the mesoporous cobalt oxide exhibit the enhancement of catalytic activity while Pt is encapsulated by the oxide thin layers forming the reactive metal-oxide interfaces. In addition, we address the fundamentals of the electrocatalytic process and on locating the real active sites at the solid-liquid interface by utilizing in-situ electrochemical scanning tunneling microscopy. Overall, the atomic-scale imaging of the reactive surfaces gives rise to the design rule of advanced bimetallic and mixed catalysts.

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Jeong Young Park (박정영) did his PhD in Physics at Seoul National University and postdoc at LBNL (Go Bears!) After some years as staff scientist here he returned to Korea and joined the Chemistry faculty at KAIST. Prof. Park has authored 320 peer-reviewed papers and book chapters in international journals.

 

https://events.berkeley.edu/BNNI/event/237676-designing-advanced-nanocatalysts-by-looking-at
Polar Topological Defects – Fundamentals to Applications: Nano Seminar series, April 5https://events.berkeley.edu/BNNI/event/230393-polar-topological-defects-fundamentals-to

Topological defects such as vortices and skyrmions have recently gained significant interest in solid state materials as ferroic materials (ferromagnets and ferroelectrics) have become a test-bed to realize and control these nanoscale structures. Although this phenomenon is being investigated as a pathway to energy efficient information storage, broader applications in interaction of electromagnetic waves with such features are emerging.

In the case of ferroelectrics, boundary condition engineering is used to achieve vortices, skyrmions, and merons in low dimensional epitaxial oxide heterostructures.

In this talk, I will introduce the notion that similar phenomenology but at the atomic scale can be achieved in charge density wave phases, especially nominally semiconducting chalcogenides. I will outline my group and other groups’ efforts in showing non-trivial toroidal polar topologies at the atomic level in chalcogenides with nominally empty conduction band with d-orbital character such as 1T-TiSe2, Ta2NiSe5 and BaTiS3.

Specifically, we use X-ray single crystal diffraction as a probe for high quality single crystals of a quasi-1D hexagonal chalcogenide, BaTiS3, to reveal complex polar topologies such as vortices, and head-to-head and tail-to-tail arrangement of dipoles. Recent experiments and theoretical studies on the stability and dynamics of these features, and their broad connection to low dimensional magnets, will also be discussed. Lastly, I will outline the perspective for photonic applications of polarization textures.

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Jayakanth Ravichandran did his PhD in the Ramesh lab here at UC Berkeley (Go Bears!) and postdoc with Philip Kim at Harvard. He joined the USC faculty in 2015.

https://events.berkeley.edu/BNNI/event/230393-polar-topological-defects-fundamentals-to
Dynamic Control Of Active Matter: Nano Seminar Series, April 12https://events.berkeley.edu/BNNI/event/229975-dynamic-control-of-active-matter-nano-seminar

Through the magic of ‘active matter,’ which converts chemical energy into mechanical work to drive emergent properties, biology solves a myriad of seemingly impossible physical challenges. I will present my lab’s efforts to develop new fluid mechanics models to direct the flow of matter enabled by the use of “active” molecules found within living systems.

We design 2D composite materials with tunable inclusions of lipid domains embedded within an active elastic network. These mechanoresponsive lipid inclusions enable exquisite control over the phase separation and material properties (like failure resistance) of 2D composite materials. I will also present our recent work on model predictive control and learning of many-body colloidal interactions driven by active and hydrodynamic forces.

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Sho Takatori did his PhD at CalTech and postdoc as a Miller Fellow here at UCB (Go Bears!). He joined the UCSB faculty in 2020. Awards include a Packard Fellowship and the ACS New PI.

https://events.berkeley.edu/BNNI/event/229975-dynamic-control-of-active-matter-nano-seminar
Quantum Science With Rare-Earth Ions In Crystals - Nano Seminar series, April 19https://events.berkeley.edu/BNNI/event/208842-quantum-science-with-rare-earth-ions-in-crystals-nano
Rare-earth ions in crystals, when strongly coupled with optical and superconducting resonators, form a novel platform that facilitates the exploration of quantum many-body physics and the development of light-matter interfaces for the future quantum internet. Through the utilization of a large ensemble of Ytterbium-171 ions doped into a high-cooperativity nanophotonic cavity made of yttrium orthovanadate, we have recently investigated fundamental phenomena in many-body cavity electrodynamics, unveiling a rich interplay between driven inhomogeneous emitters and cavity photons.
Moreover, we have also demonstrated the utility of local nuclear spins within the lattice as deterministic quantum resources, serving as long-lived quantum memory.
These advancements not only expand the capabilities of rare-earth ion-based platforms but also open avenues for novel applications in quantum technologies.
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Joonhee Choi did his PhD at Harvard and postdoc at Caltech at the Institute for Quantum Information and Matter (IQIM). He joined the Stanford EE faculty last year.
https://events.berkeley.edu/BNNI/event/208842-quantum-science-with-rare-earth-ions-in-crystals-nano
Printing Functional Polymers for Sustainable Earth and Habitable Mars: Nano Seminar series, April 26https://events.berkeley.edu/BNNI/event/229388-printing-functional-polymers-for-sustainable-earth

Printing technologies have the potential to revolutionize manufacturing of electronic and energy materials by drastically reducing the energy cost and environmental footprint while increasing throughput and agility. For instance, printing organic solar cells can potentially reduce energy payback time from 2-3 years to as short as 1 day! At the same time, additive manufacturing of such functional materials brings a new set of challenges demanding exquisite control over hierarchical structures down to the molecular-scale.

We address this challenge by understanding the evaporative assembly pathway and flow-driven assembly central to all printing processes. We discover a surprising chiral liquid crystal mediated assembly of achiral semiconducting polymers in an evaporating meniscus. We uncover the molecular assembly mechanism and further show that the chiral helical structures can be largely modulated by controlling printing regimes.

Such new topological states of semiconducting polymers can empower unprecedented control over charge, spin, and exciton transport, reminiscent of how Nature efficiently transfers electrons and transduces energy using chiral helical structures. The ability to control non-equilibrium assembly during printing sets the stage for dynamically modulating assembled structures on the fly.

We demonstrate this concept by programming nanoscale morphology and structure color of bottlebrush block copolymers during 3D printing. This approach holds the potential to reduce the use of environmentally toxic pigments by printing structure color. Complementing the above hypothesis-driven approach, we are pursuing data-science driven approach to drastically accelerate discovery and manufacturing of functional polymers. By linking automated synthesis, testing, and machine learning in a close-loop, we are able to optimize function highly efficiently while discovering new physical insights for transferring closed-loop optimization into hypothesis driven discovery.

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Ying Diao did her PhD at MIT and postdoc at Stanford. She won many early-career awards from NSF, Sloan, NASA, ACS, etc., and is an Advanced Materials “Rising Star”. She joined UIUC in 2015.

https://events.berkeley.edu/BNNI/event/229388-printing-functional-polymers-for-sustainable-earth