Past Colloquia

A Brief (but Amazing!) History of how Photovoltaics Became the Dominant New Electric Power Source in the US

World use of photovoltaic (PV) solar electricity has been increasing at an average annual exponential growth rate >35% since about 2000. Not surprisingly, during this same time, the percentage of US-consumed energy (~100 Quadrillion BTUs total) derived from PV has increased from ~0.001% in 2004, to ~1% at the end of 2018. Indeed, if these trends continue, PV could produce ~25% of all energy consumed in the US by as early as 2030. Combining this with the rapidly decreasing energy costs for large grid-tied PV systems (presently <2.5¢/kWh for long-term power purchase agreements) largely explains why PV-derived energy is – even now – a main source of new US and world electric energy. Although the majority of this PV-derived energy is presently generated by crystallinebased Si module technologies, because of combined efficiency, production, cost, and other advantages, an ever-increasing amount of PV energy is being produced from polycrystalline thin-film (TF) materials. These TF PV technologies owe much of their rapidly advancing success to improved understanding in related materials synthesis, while applying these advancements to industry, in turn, has relied on design innovations of related vacuum-process equipment. This talk will briefly overview the present state of TF PV technologies, taking into consideration both the present dominance of crystalline Si PV, and evolving trends in TF PV. Several examples where keen understanding of vacuum processes in laboratory-scale devices has fostered successful utilization of advanced vacuum technology in the commercial TF PV industry will be presented. The talk will also suggest some areas where further advancements in vacuum-process and equipment innovation could yield potentially even lower-cost TF PV technologies.

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Solubility, stability, and transparency in the refractive proteins of the vertebrate eye lens

The crystallin proteins of the vertebrate eye lens are highly soluble, remaining in solution at a concentration upwards of 400 mg/mL despite a lack of protein turnover and frequent exposure to UV light. These proteins, which are strongly conserved in all vertebrates, are mostly expressed during early development and must remain in solution for a lifetime.  Extremely soluble proteins are the flip side of the protein aggregation problem, providing useful case studies for probing the molecular basis of solubility. Understanding how crystallins stay in solution, even at high concentrations and in the face of photodamage and chemical modification provides insight into how to prevent protein deposition diseases. An equally fascinating question is how these proteins interact with light to provide the refractive power of the lens.  I will present data from a range of biophysical techniques, including NMR spectroscopy, X-ray crystallography, mass spectrometry, and light scattering to illustrate how crystallins resist post-translational modification due to aging, UV light damage, and even gamma irradiation.

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Proteome-wide Ligand and Target Discovery in Cells

Advances in DNA sequencing and editing technologies have revolutionized our understanding of the molecular basis of many human diseases. However, many disease-relevant genes encode proteins that are poorly characterized and/or are considered “undruggable”, hindering our understanding of disease mechanisms and translating this knowledge into new therapies. Chemical probes offer a valuable way to directly interrogate the function and disease-relevance of proteins and can also serve as valuable leads for drug development, yet most proteins in the human proteome lack small-molecule ligands that can serve as probes. More generally, the boundaries, if any, on the ligandability, and therefore potential druggability, across native proteomes remains poorly understood. In this seminar, I will describe our lab’s efforts to develop powerful chemical proteomic strategies to broadly map ligandable proteins directly in cells, and how this information can be advanced into useful chemical probes to investigate protein function.

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Manipulating Phonons at the Nanoscale: From Materials Design to Phononic Devices

The development of phononics —the discipline that investigates phonon transport and aims at engineering devices with the same functionalities as electronic or photonic ones — has been hindered by the inherently challenging nature of phonon manipulation. An effective and flexible control of phonon propagation would require expanding the phonon toolbox to include all the elemental building blocks that make it possible to switch and modulate signals. In this talk I will describe two complementary approaches to this problem. At first, I will discuss the potential of crystal phase engineering, an emerging field in nanoscience that consists of the design of materials with tailor-made properties by growing and juxtaposing ad hoc crystal phases of the same material. Next, I will discuss the possibility of a fully electromagnetic control of the phonon flux, which can be continuously modulated by an externally applied electric field in polar materials or magnetic fields in magnetic materials, revealing the mechanisms by which experimentally accessible fields can be used to tune the thermal conductivity, even at room temperature. These findings open the way to a fully-electric control of phonon transport that can be exploited for the design of thermal transistors and pave the way to signal processing with phonons.

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Synthesis and Intercalation Chemistry of Two-Dimensional (2D) Materials

Two-dimensional materials are currently being investigated for their unique properties which can undergo dramatic changes as the they approach atomic thicknesses. The most studied 2D materials are elements like graphene and germanene or binary compounds like transition metal dichalcogenides (TMDs). This presentation will focus on two of our current projects which focus on synthesizing and the intercalation of different metals and molecules into these layered materials. The first project focuses on a novel phase of WS2 with a monoclinic structure which is being studied as a topological superconductor. This phase can only be produced after intercalation of the hexagonal phase with potassium and subsequent removal of the K+ ions. The second project focuses on more complex metal oxyhalides which form robust two-dimensional metal oxide sheets separated by halide van der Waals regions. These materials have a variety of physical, electronic, and magnetic properties that can be easily tuned through changes in the halide (Cl, Br, or I) or using simple intercalation chemistry where ions (Li, Na, K, Rb, and Cs) are inserted between the metal oxide layers. The intercalation reactions give rise to dramatic changes in the optical and electronic properties of these compounds which were investigated by resistivity measurements, absorption and Raman spectroscopy, X-ray diffraction (XRD), and electron microscopy (SEM &TEM). By studying the underlying intercalation reactions, we can improve our knowledge of the reaction kinetics and the limiting factors in these reactions which will lead to novel materials with a broader range of intercalation species.

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Advanced Scanning Electrochemical and Spectroelectrochemical Methods for Analyzing Surfaces of Catalytic Electrode Materials 

Ultrasensitive electrochemical and optical imaging approaches are critical for realizing local chemical information particularly for systems such as sustainable energy harvesting and conversion. We are interested in developing electrochemical and spectroelectrochemical techniques for ultrasensitive quantitative analysis of catalytic surfaces and localized redox activities with improved spatial and spectral and temporal resolutions. Examples of scanning electrochemical microscopy based on ultramicroelectrodes, nanoelectrodes, and optical fiber electrodes, and optical imaging techniques will be discussed in this seminar. These techniques help understand fundamental aspects of an electrochemical process, such as local heterogeneities in catalytic reaction and stability issues of functional low-dimension metallic and semiconductor electrode materials with synergistic functions for sunlight harvesting, conversion, and storage into chemical fuels. These studies will provide insights into developing unique catalytic and photonic properties of nanostructured electrode materials for the efficiency and selectivity of the solar-to-fuel conversion.

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Manufacturing Forensics at 3M: The Confluence of Analytical Chemistry, Material Science, and Process Technology

Everyone loves a “who done it” forensics story, ripe with twists and turns, drama, and surprise discoveries.  Chris will describe the application of this same line methodology applied to manufacturing at 3M—Manufacturing Forensics.  Making complex and unique products often comes with unique materials and processing challenges, many of which cannot be solved with engineering alone.  Analytical chemistry is foundational to finding the root cause of many of these problems.  Chris will show multiple examples where hard core analytical chemistry was developed and applied to unique material, product, and processing challenges, many with twists, turns, and drama to hopefully keep you on the edge of your seat!

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Adventures in Nanoscale Electrochemistry

Solid-electrolyte interfaces play a central role in electrochemical systems for energy conversion/storage, catalysis, and sensing. Understanding the structure-function relationships which control the performance of these systems is a broad goal of the electrochemistry community, but it is challenging to establish these relationships experimentally. Electrochemical interfaces are fundamentally complex, exhibiting site-to-site variations in reactivity which make the interpretation of data produced using traditional, “bulk” analytical techniques problematic. A key focus of the Hill Laboratory at UW has been the development of “single entity” analytical techniques which can probe discrete active sites within these complex interfaces, generating more detailed insights to help guide the design of improved practical systems. These techniques employ electrolyte-filled pipets to locally address a surface of interest, effectively providing spatial control over any interfacial chemical process with resolutions down to ~10 nm. Here, I will give an overview of my lab’s work which spans studies of electrocatalysis at individual metal nanocrystals, the synthesis and manipulation of individual nanoparticles at electrochemical interfaces, and carrier transport within well-defined, μm-scale crystals of 2D semiconducting materials.

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Advanced Bipolar Membranes: Design Principles and Applications in Electrochemical Technology 

Bipolar membranes (BPMs) consist of an anion-selective ionomer membrane laminated with a cation-selective ionomer membrane. They have applications across electrochemical technology. BPMs generate pH gradients under an applied bias by driving water dissociation (WD) into protons and hydroxide at the interface between the two different ionomers. In BPM water electrolysis, this feature enables devices that operate proton reduction in locally acidic conditions where the kinetics are fast and water oxidation in locally basic conditions where efficient earth-abundant catalysts are stable. In electrodialysis, BPMs can be used to economically generate acid and base from brine on demand, which is critical for many industrial processes including water treatment. Alkaline solutions generated by BPM electrodialysis can further be used in CO2 capture schemes from the air or ocean. As the predominant H+/OH- ion flow is out from the center of the BPM, their use in CO2 electrolysis devices mitigates unwanted cross-over of reactants or products.  

I will present progress in designing advanced BPMs with a focus on understanding and optimizing the WD catalyst integrated between the anion- and cation-selective layers. We systematically studied ~40 metal and metal oxide nanoparticle interlayers and discovered that the local pH is a critical, but previously unrecognized, variable affecting WD kinetics. Combining WD catalysts efficient in acidic and basic conditions into catalyst bilayers nearly eliminates the WD overpotential in BPM water electrolyzers operating at 20 mA cm-2 and enables BPM operation at 0.5 A cm-2 with a total applied electrolysis potential of ~ 2 V. By thinning the cation-selective ionomer layer, water transport to the BPM junction is improved, leading to current densities > 3 A cm-2. These values are substantial improvements over the state of the art and have the potential to lower operating costs (due to higher BPM voltage efficiency) and capital cost (due to higher current density) of the applications introduced above. Ongoing efforts to provide a detailed chemical and physical understanding of the water-dissociating junction in BPMs will be outlined.

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Droplet Like It’s Hot: How Chemistry Changes in Tiny Volumes

How is chemical reactivity different in sub-microliter volumes compared to bulk, continuous phases? For centuries, chemists have assumed that chemical reactivity is similar in the ocean as it is in a lysosome despite volume differences spanning nearly 40 orders of magnitude. While measurement science techniques exist to probe reactivity in small volumes, they suffer in their ability to characterize femtoliter (10^-15 L) or smaller nanodroplets, one at a time. This talk will detail our group’s efforts in developing nanoelectrochemical methods to study reactivity in water micro- and nanodroplets. We will demonstrate the heterogeneous growth of a new phase does not depend on the water nanodroplet size, but the heterogeneous nucleation kinetics can be enhanced in such complex environments due to localized surface concentration supersaturation. Due to rapid mass transfer within nanodroplets, we will demonstrate the possibility of electrosynthesizing high entropy alloy nanoparticles at room temperature. Finally, we will demonstrate that homogeneous enzymatic reaction rates are accelerated in water nanodroplets and that the rate is inversely proportional to the nanodroplet size. The talk will end with a future outlook on the role such experiments can play in understanding how nature takes advantage of nanoconfinement in the genesis and propagation of life.

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Roadmap to Commercialization of Ionic Liquid Extraction Technologies Including Roadblocks, Detours, and Areas Under Construction

There will be common challenges to scaling up any ionic liquids separations technologies which require very large volumes of ionic liquid. Some of these challenges will be illustrated in this presentation which chronicles my personal motivation and journey into the extraction of chitin from shrimp shell from discovery to current commercialization efforts. The road being taken from discovery in an academic laboratory, through attempts to navigate the scaling up to commercial scale using the vehicle of a faculty startup company is rewarding, but fraught with roadblocks, detours, and unexpected challenges. The differences in ‘technically feasible’ and ‘commercially viable’ are not always evident from the beginning of the journey, however, one wonders what achievements we miss as a Society because it was assumed to not be commercially viable.