Each day’s plenary sessions brought all meeting attendees together for key events. All times below are in Pacific Time (GMT -7).
Thursday, August 20: Plenary Sessions
Annelise Barron, Chair of the User Executive Committee
Jeffrey Neaton, Associate Laboratory Director for the Energy Sciences Area
Kristin Persson, Director of the Molecular Foundry
Applications of emerging technology to challenges in chemistry
Jeannette M. Garcia
Senior Manager of Quantum Applications, Algorithms, and Theory
Almaden Research Center, IBM
The focus of this talk will be on technologies that are emerging to tackle challenges in plastics sustainability, energy storage, and simulation in chemistry. I will discuss new technological tools being developed at IBM that are impacting research directions in these important areas. I will highlight examples of industrial research where computational approaches to chemistry are combined with experiments to gain new insights.
User Highlights (Parallel Sessions)
Advancing Equitable Access to Safe Drinking Water Through Technological Innovation
Katya Cherukumilli, University of Washington
Over 200 million people worldwide are at risk of developing crippling bone deformities and mottled enamel by drinking water with fluoride levels exceeding international standards (1.5 ppm F–). Fluoride contamination has been reported in arid regions across India, East Africa, Middle East, China, Mexico, and Argentina. The Rift Valley and India account for over 40% of the global population exposed to toxic fluoride concentrations. Conventional water remediation techniques including adsorbent and membrane-based filters have not been successfully implemented in low-income settings. The recently developed Scalable and Affordable Fluoride Removal process (SAFR) is reliant on bauxite, a globally abundant and aluminum-rich mineral ore. SAFR has the potential to be locally affordable, culturally appropriate, technically robust, and operated and maintained with minimal skilled labor. Despite its lower surface area and fluoride adsorption density, bauxite ($0.03/kg) has proven to be a cost-competitive alternative to industrially refined activated alumina ($2/kg). Material characterization studies probing the bulk and surface properties of global bauxite ores elucidate key factors governing fluoride adsorption. Recent pilot studies in East Africa and India demonstrated challenges with processing bauxite in resource-constrained settings and informed the design of flow-through column filters optimized for the use of regenerable granular bauxite media.
Strain-driven phase transitions in 2D van der Waals based devices
Stephen Wu, University of Rochester
As transistors continue to scale down in size, physical limitations from nanoscale field-effect operation begin to cause undesirable effects that are detrimental to the further advancement of computing. We explore an alternative to conventional field-effect transistor operation by using dynamic strain engineering on 2D van der Waals materials to induce electronic/structural phase transitions. In this talk, we focus on challenges in achieving dynamically controllable strain in 2D-bonded materials and how these challenges can be overcome in a scalable on-chip device. We introduce one implementation of such a device using both static thin film stress capping layers and ferroelectric oxide gate-dielectrics. Here, MoTe2 can be reversibly switched with electric-field induced strain between the 1T’-MoTe2 (semimetallic) phase to a semiconducting MoTe2 phase in a three-terminal field effect transistor geometry. With support from the Molecular Foundry, we explore 2D strain engineering through theory to identify new phases in MoTe2 that are sensitive to strain, as well as providing collaborative input into a multiscale computational model of dynamic strain engineering in 2D systems. This work will eventually build up an atoms-to-devices model of strain control in 2D materials. Using this implementation as a starting point, other phase transitions in 2D materials may be explored using this ‘straintronic’ device concept, which may enable low-power, high-speed, non-volatile, gate-controllability over a wide variety of exotic states of matter.
Miniaturized Lasers using Plasmonic Nanoparticle Lattices
Jun Guan, Northwestern University
Miniaturized lasers are important for fundamental studies of light-matter interactions and applications in on-chip photonic integration. Plasmonic nanoparticle lattices supporting surface lattice resonances can provide optical feedback for directional lasing emission at room temperature. This talk describes how integrating quantum dots (QDs) with plasmonic lattices enables engineering of lasing emission properties. Conformal coating of CdSe-CdS core-shell QD films on Ag nanoparticle lattices results in the formation of hybrid waveguide-surface lattice resonance modes. Either radially or azimuthally polarized lasing beams can be realized by leveraging the sidebands of these hybrid modes at nonzero wavevectors. By controlling which high-symmetry point (Δ, Γ or M) of the lattice overlaps with the QD gain, we demonstrate manipulation of the lasing emission angles. Our QD-plasmon lasers provide controllable polarization patterns and emission directions, which enables opportunities for quantum-optical technologies and commercial photonic devices.
10:05 AM – 10:15 AM
In Pursuit of the Perfect Plastic
Geoffrey W. Coates
Tisch University Professor in the Department of Chemistry and Chemical Biology
Society depends on polymeric materials more now than at any other time in history. Although synthetic polymers are indispensable in a diverse array of applications, ranging from commodity packaging and structural materials to technologically complex biomedical and electronic devices, their synthesis and disposal pose important environmental challenges. The focus of our research is the development of sustainable routes to polymers that have reduced environmental impact. This lecture will focus on our research to transition from fossil fuels to renewable resources for polymer synthesis, as well as the development of polymeric materials designed to bring positive benefits to the environment.
User Highlights (Parallel Sessions)
Atomic Electron Tomography: Capturing the Structure and Dynamics of Materials at 4D Atomic Resolution
Jianwei (John) Miao, UCLA
Crystallography has been fundamental to the development of many scientific fields. By measuring the 3D arrangement of atoms with high precision, coupled with quantum mechanical calculations such as density functional theory, we can understand and engineer new materials with applications from electronics and energy conversion to disease fighting drugs. But the limitation of this powerful technique is that we can only know the periodically averaged structure. Crystallography is blind to defects and aperiodicities in the atomic arrangements, which are often crucial to a material’s performance. Although cryo-electron microscopy can determine the 3D structure of biomolecules at near-atomic resolution, it requires the averaging of many copies of the biomolecules with identical or similar conformations. The development of powerful ultra-high resolution imaging methods such as scanning probe microscopy and aberration-corrected electron microscopy allow us to see individual atoms without the constraint of periodic averaging. However, seeing atoms is not the same as knowing their 3D coordinates with sub-angstrom resolution, which is required for accurate prediction of properties using quantum mechanics.
We are now on the cusp of a solution to this problem. By combining the atomic resolution electron imaging methods with powerful tomographic reconstruction, it is now possible to obtain the 3D atomic structure of crystal defects and non-crystalline systems. Many challenges had to be overcome for atomic electron tomography (AET) to succeed, but over the past years several such structures have begun appearing heralding a revolution in structure science that may be comparable to that of x-ray crystallography a century ago. Here, we review the major advances and the interdisciplinary science enabled by this groundbreaking methodology that is expected to transform our understanding of structure-function relationships in materials science, chemistry, condensed matter physics, nanoscience and nanotechnology in the 21th century.
Assembly-associated trans-to-cis amide bond isomerization with peptoid B28 nanosheets
Anant Paravastu, Georgia Tech
We employed solid-state nuclear magnetic resonance (NMR) measurements to reveal hypothesized isomerization of backbone amide bonds within nanosheets of Peptoid B28. Peptoids are peptide analogs in which sidechains branch from backbone amide nitrogen atoms instead of α-carbons. Like peptides, peptoids are sequence-defined heteropolymers that can adopt well-defined 3-dimensional structures. Peptoid B28 assembles into nanosheets, with extended molecular conformations promoted by sidechains that alternate between hydrophilic and hydrophobic and brickwork-like arrangement of oppositely charged blocks. Our measurements provide direct evidence for a long-standing hypothesis: sidechain branching at the amide nitrogen makes cis amide bond conformations accessible by lowering the energy gap between trans and cis. We measured distance-dependent 13C-13C magnetic dipolar couplings within samples that were isotopically labeled at pairs of adjacent α-carbon sites. Interestingly, results reveal that backbone amide bond isomerization depends on self-assembly and position within the molecular assembly.
Rational design of conjugated polymers for deformable electronics through thin film mechanics and neutron scattering
Xiaodan Gu, University of Southern Mississippi
The past few decades have witnessed a dramatic advance in organic electronic devices. There are growing interests in making stretchable organic electronic devices that bend, twist, stretch, and conform to any surface. Artificial skin is a great example that can be potentially used for restoring lost limbs. In recent years, many efforts have been devoted to pushing the boundaries between chemical engineering and chemistry towards materials with excellent charge transport. However, an important quantity of devices built from these materials suffers from mechanical stress, which limits their use for wearable electronics or implantable neuroelectronics. Little is known about how to control the modulus and failure model of the conjugated polymer thin film. Therefore, it is now important to consider the mechanical robustness of the materials and develop new strategies to obtain new materials that can tolerate extreme environmental conditions.
In this talk, I will cover our recent findings on new design rules to control the mechanical property of conjugated polymers. I will first discuss our new methodology to measure thin-film mechanics and fractures in a strongly confined thin film state close to the real-world conditions. Through precisely controlled glass transition temperature for conjugated polymers, we can predict, control and manipulate the modulus of the conjugated polymers. This was also supported by molecular dynamics simulation. Neutron scattering for conjugated polymers provided unique information on the chain conformation and chain rigidity, thus can be correlated with molecular entanglement, consequently failure mechanism. Application of the new materials as active materials in organic field-effect transistors (OFETs) will also be discussed.
11:05 AM – 1:00 PM
Break, Virtual Poster Fair, and Networking Clusters
Molecular Foundry User Town Hall
Panelists from the Molecular Foundry and User Executive Committee leadership teams will be available to field questions from the User Community.
2:30 PM – 4:00 PM
Break, followed by a Guided Virtual Tour of the Molecular Foundry
Friday, August 21: Plenary Session
Presentation: New Foundry Capabilities
Super-Resolution Microscope: Behzad Rad
Electron Beam Lithography: Stefano Cabrini
Quantum SPLEEM: Andreas Schmid
Emerging Capabilities in Machine Learning: Mary Scott
NSRC Recapitalization: Major Items of Equipment: Jim Ciston
Announcement: Outstanding Staff Award
Student Research Paper Award Winner Talk
Design Principles for Trap-Free CsPbX3 Nanocrystals: Enumerating and Eliminating Surface Halide Vacancies with Softer Lewis Bases
David Nenon, UC Berkeley
We introduce a general surface passivation mechanism for cesium lead halide perovskite materials (CsPbX3, X = Cl, Br, I) that is supported by a combined experimental and theoretical study of the nanocrystal surface chemistry. A variety of spectroscopic methods are employed together with ab initio calculations to identify surface halide vacancies as the predominant source of charge trapping. The number of surface traps per nanocrystal is quantified by 1H NMR spectroscopy, and that number is consistent with a simple trapping model in which surface halide vacancies create deleterious under-coordinated lead atoms. These halide vacancies exhibit trapping behavior that differs among CsPbCl3, CsPbBr3, and CsPbI3. Ab initio calculations suggest that introduction of anionic X-type ligands can produce trap-free band gaps by altering the energetics of lead-based defect levels. General rules for selecting effective passivating ligand pairs are introduced by considering established principles of coordination chemistry. Introducing softer, anionic, X-type Lewis bases that target under-coordinated lead atoms results in absolute quantum yields approaching unity and monoexponential luminescence decay kinetics, thereby indicating full trap passivation. This work provides a systematic framework for preparing highly luminescent CsPbX3 nanocrystals with variable compositions and dimensionalities, thereby improving the fundamental understanding of these materials and informing future synthetic and post-synthetic efforts toward trap-free CsPbX3 nanocrystals.
9:50 AM – 3:00 PM
Break, followed by Symposia Sessions A and B