the wire: Real-time imaging helps reveal active sites of photocatalysts<img alt="" src="/news/PublishingImages/shutterstock_613151393_760-760x507.jpg?RenditionID=1" style="BORDER:0px solid;" /><p>Nanoscale photocatalysts are small, man-made particles that harvest energy from sunlight to produce liquid fuels and other useful chemicals. But even within the same batch, the particles tend to vary widely in size, shape and surface composition. That makes it hard for researchers to tell what’s really doing the work.</p><p>A real-time imaging solution developed at Washington University in St. Louis could help, as reported in a new study in the journal <a href="">ACS Catalysis</a>.</p> <p>“The challenge in correlating single-molecule optical images with specific active sites in nanoscale catalysts is that the 10 to 25 nanometer spatial resolution provided by this technique still averages over many atoms on the surface of the catalyst — thus making it difficult to correlate reaction events with the structure of the catalyst,” said <a href="">Bryce Sadtler</a>, assistant professor of chemistry in Arts & Sciences and co-lead author of the new study.</p><p>Sadtler wanted to try imaging catalytic reactions using single-molecule fluorescence ever since he arrived at Washington University in 2014. The project got a jump-start after he was introduced to <a href="/Profiles/Pages/Matthew-Lew.aspx">Matthew Lew</a>, assistant professor in the <a href="">Preston M. Green Department of Electrical & Systems Engineering</a> in the <a href="/Pages/home.aspx">McKelvey School of Engineering</a>.</p><p>“After several discussions with Matt, we agreed that the microscopy hardware and image processing he was developing for super-resolution microscopy could provide a powerful tool to obtain structural information on the nature of the active sites in nanoscale catalysts that was previously unattainable,” Sadtler said.</p><p>For the new work reported in ACS Catalysis, the researchers imaged individual chemical reactions taking place on the surface of single tungsten oxide nanowires, a type of nanoscale photocatalyst that Sadtler’s group synthesized for the study.</p><p>They used two different chemical reporters that become fluorescent, or light up, in response to different types of reactions on the surface of the nanowires. By analyzing the spatial patterns of where these chemical reactions occur, they were able to elucidate the chemical structure of active sites on the surface of the nanowires.</p><p>The researchers found that clusters of oxygen vacancies along the nanowire surface activate adsorbed water molecules during the photocatalytic generation of hydroxyl radicals — an important intermediate in the production of chemical fuels, including hydrogen gas and methanol, from sunlight.</p> <figure class="wp-caption alignright" style="box-sizing: inherit; display: inline; margin: 0px 0px 1.5em 1.5em; float: right; max-width: 100%; padding: 0px; border: none; background-image: none; caret-color: #3c3d3d; color: #3c3d3d; font-family: "source sans pro", "helvetica neue", helvetica, arial, sans-serif; font-size: 19.200000762939453px;"><img data-attachment-id="381518" data-permalink="" data-orig-file="" data-orig-size="1806,945" data-comments-opened="0" data-image-meta="{"aperture":"0","credit":"","camera":"","caption":"ImageJ=1.52k","created_timestamp":"0","copyright":"","focal_length":"0","iso":"0","shutter_speed":"0","title":"ImageJ=1.52k","orientation":"1"}" data-image-title="ImageJ=1.52k" data-medium-file="" data-large-file="" class="size-full wp-image-381518" src="" alt="photocatalyst graphic" style="box-sizing: inherit; border-width: 0px; width: 627px; display: block; margin: 5px;"/><figcaption class="wp-caption-text" style="box-sizing: inherit; margin-bottom: 0px; font-size: 1rem; font-style: italic; line-height: 1.333; color: #626464; margin-top: 0.25em;">(Image courtesy ACS Catalysis)</figcaption></figure> <p>“While previous studies have focused on isolated oxygen vacancies, a type of defect common in metal oxides, the results reveal the significance of a structural feature — clusters of oxygen vacancies — in achieving high photocatalytic activity,” Sadtler said.</p><p>“This new insight provides a path toward designing photocatalysts with enhanced activity for sunlight-to-fuel conversion by controlling the distribution of oxygen vacancies.”</p><p>The results themselves — and the process used to uncover them — are both exciting to the researchers.</p><p>“It is always a dream to directly observe the single catalytic turnovers on the surface of solid catalysts while the catalytic transformation is going on,” said <a href="">Meikun Shen</a>, a graduate student in chemistry and first author of the new paper. “I can only speak for myself, this is my personal feeling!”</p><p>This particular imaging approach provides detailed spatial and temporal information on the catalytic process — something that is usually invisible to scientists like him, Shen explained.</p><p>“In this type of experiment, the chemical properties of the catalyst are usually hard to reveal,” Shen said. “We managed to overcome this difficulty by using two different molecules to probe either the activity or the chemical property of the same catalyst. The direct correlation we observed is unique in the research field of heterogeneous catalysis.”</p><hr style="height: 1px; background-color: #c8c8c8; border-top-width: 0px; margin-bottom: 1.5em; caret-color: #3c3d3d; color: #3c3d3d; font-family: "source sans pro", "helvetica neue", helvetica, arial, sans-serif; font-size: 19.200000762939453px;"/><p>Funding: This project received internal seed funding from Washington University’s <a href="">International Center for Energy, Environment and Sustainability</a> (InCEES).</p><p>Read more: Nanoscale Colocalization of Fluorogenic Probes Reveals the Role of Oxygen Vacancies in the Photocatalytic Activity of Tungsten Oxide Nanowires. ACS Catal. 2020, 10, 3, 2088-2099. January 8, 2020. <a href=""></a><br/></p><span> <div class="cstm-section"><h3>Matthew Lew<br/></h3><div><p style="text-align: center;"> <img src="/Profiles/PublishingImages/Lew_Matthew_5620.jpg?RenditionID=3" class="ms-rtePosition-4" alt="" style="margin: 5px;"/> </p><p></p><ul style="padding-left: 20px; caret-color: #343434; color: #343434;"><li>Electrical Systems Engineering - <span style="caret-color: #343434; color: #343434;">Assistant Professor</span><br/></li><li>Research: Builds advanced imaging systems to study biological and chemical systems at the nanoscale, leveraging innovations in applied optics, signal and image processing, design optimization, and physical chemistry.<br/></li></ul><div style="text-align: center;"> <a href="/Profiles/Pages/Matthew-Lew.aspx">View Bio</a><br/></div></div><br/></div></span>An imaging solution developed in collaboration between chemists in Arts & Sciences and engineers at the McKelvey School of Engineering reveals the role of oxygen vacancies in the photocatalytic activity of tungsten oxide nanowires. (Photo: Shutterstock)Talia Ogliore research has implications for harvesting energy from sunlight<p>​InCEES-funded research has implications for harvesting energy from sunlight<br/></p> the molecular world<img alt="" src="/news/PublishingImages/Jennifer_Dionne_TON7598-760x507.jpg?RenditionID=1" style="BORDER:0px solid;" /><p>​Directly seeing the workings of our world at nano- and molecular scale has largely remained an impossible task, left to theory and working assumptions. WashU alumna Jennifer Dionne, BS ’03, has found a way around all that. Dionne is among the first scientists to successfully focus and manipulate light beyond the known diffraction limit.</p><p>What does all this mean for the future? According to Dionne, it could mean more effective pharmaceuticals and agrochemicals, more efficient photocatalysts for clean energy and even all-optical computing schemes that mimic the way our brain computes, but at the speed of light. Ultimately, Dionne hopes her technologies will help “enable a healthier population and a healthier planet.”</p><p>Dionne’s approach helps her view intricacies of molecular structure and molecular binding, which is particularly important for creating safe agrochemicals and pharmaceuticals. Adverse molecular binding in agrochemicals can cause them to leave residues in soil and lead to colony collapse in bees and organ failure in fish, birds and larger animals. In pharmaceuticals, it can give rise to delayed efficacy or deleterious<br/>side effects. Dionne uses light to detect and sort molecules with the goal to eliminate adverse molecular binding, achieving greater precision and efficacy in pharmaceutical and agrochemical design.</p><p>Dionne is also using these light-based approaches to understand the basis of various diseases. “We’re hoping to understand how the immune system can be more effective in fighting off infection, including bacterial infections and cancer,” Dionne explains. “By visualizing reactions occurring on the nanoscale, like an immune cell fighting a pathogen or the response of a single bacterial cell to an antibiotic, we hope to develop better drugs and immune therapies.” For this work, Dionne recently received the National Institutes of Health Director’s New Innovator Award for exceptionally creative early career scientists.</p><p>Dionne also is applying photonic technology toward making more effective photocatalysts and renewable energy generation systems, with the goal of improving air and water quality and producing solar fuels.</p><p>This wide-ranging passion for discovery is nothing new for Dionne. Growing up in Rhode Island, she always sought adventure – whether doing obstacle courses with her neighbors, traveling to Australia as a junior ambassador or honing her early engineering skills at Space Academy. And at Washington University, she found her passion in science and math, and her search for knowledge was quickly taken to the next level.</p><p>“If I were to pick one thing that fostered how I am as a scientist, it would be the close-knit community WashU provided,” Dionne says. “It taught me how much you can learn by working as a team.”</p><p>The Washington University community impacted Dionne outside the classroom as well. She married Nhat Vu, BSEE ’03, one of her first-year floormates. Today, the couple has two young sons, ages 3 and 5.</p><p>During her sophomore year, she lived in the same dorm as University of Washington psychologist Kristina Olson, AB ’03, who like Dionne, became one of the few women awarded the National Science Foundation’s Alan T. Waterman Award for scientists under the age of 40. Olson won the prestigious award in 2018 (see this <a href="">article</a> in the September 2019 issue of Washington) and Dionne in 2019 — a remarkable back-to-back victory for Washington University women in the sciences.</p><p>Dionne’s light-based research will continue exploring the frontiers of molecular and nano-scale science for years to come. She says that even something as fanciful as Harry Potter’s invisibility cloak is certainly in the realm of possibility. It would involve “creating precisely arranged nanostructures that allow light to be steered around an object at every wavelength between 400 and 800 nanometers, the wavelengths corresponding to human vision.” But presently, Dionne’s focus remains the opposite — making the “invisible” visible and improving lives in a big way by observing the smallest possible scale.<br/></p><div class="cstm-section"><h4 rtenodeid="2" style="text-align: left;">WHO<br rtenodeid="3"/></h4><ul rtenodeid="4" style="text-align: left;"><li rtenodeid="5">Jennifer Dionne, BS ‘03</li></ul><h4 rtenodeid="6" style="text-align: left;">STUDIED<br rtenodeid="7"/></h4><ul rtenodeid="8" style="text-align: left;"><li rtenodeid="9">Physics, and systems science & engineering</li></ul><h4 rtenodeid="10" style="text-align: left;">LOCATION<br rtenodeid="11"/></h4><ul rtenodeid="12" style="text-align: left;"><li rtenodeid="13">Stanford, California</li></ul><h4 rtenodeid="14" style="text-align: left;">CURRENTLY<br rtenodeid="15"/></h4><ul><li rtenodeid="16" style="text-align: left;">Associate professor of materials science and engineering at Stanford University </li><li rtenodeid="17" style="text-align: left;">Director of the Photonics at Thermodynamic Limits Energy Frontier Research Center accolades</li><li><div rtenodeid="18" style="text-align: left;">2019 Alan T. Waterman Award — the National Science Foundation’s highest honor for young researchers under 40<br/></div></li></ul></div>WashU Alumna Jennifer Dionne, BS '03, has found a way to see our world on the nano- and molecular scale. Her work earned her a 2019 Alan T. Waterman Award. Photo by Tony AvelarRyan Rhea Alumna Jennifer Dionne, BS '03, is among the first scientists to successfully focus and manipulate light beyond the known diffraction limit., alumnus win IEEE best paper award<img alt="Arye Nehorai" src="/Profiles/PublishingImages/Nehorai_2017.jpg?RenditionID=7" style="BORDER:0px solid;" />Mianzhi Wang, who earned a doctorate in electrical engineering from the McKelvey School of Engineering in 2018, received the IEEE Signal Processing Society’s 2019 Young Author Best Paper Award.<div><br/></div><div>His paper, "Coarrays, MUSIC, and the Cramér Rao bound," was co-written by Arye Nehorai, the Eugene & Martha Lohman Professor of Electrical Engineering. Nehorai was Wang’s doctoral and dissertation adviser. The paper has received more than 100 citations since its publication in February 2017.<br/></div>Danielle Lacey2020-01-27T06:00:00ZMianzhi Wang, a 2018 alumnus of the McKelvey School of Engineering, won the IEEE Signal Processing Society’s 2019 Young Author Best Paper Award. named Das Family Distinguished Professor <img alt="" src="/news/PublishingImages/Sinopoli%20Das%20Distinguished.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>Bruno Sinopoli has been named the Das Family Distinguished Professor in Electrical Engineering in the McKelvey School of Engineering at Washington University in St. Louis. He was installed Jan. 16, 2020. <br/></p><p>Sinopoli is professor and chair of the Preston M. Green Department of Electrical & Systems Engineering. He is a renowned expert in cyber-physical systems and control systems. His research focuses on robust and resilient design of cyber-physical systems, networked and distributed control systems, distributed interference in networks, smart infrastructures, wireless sensor and actuator networks, adaptive video streaming applications and energy systems. He also has an interest in social engineering issues, including investigating the mechanisms of influence of people on each other. He seeks to understand these mechanisms and to further this understanding in ways that can be beneficial to humanity.<br/></p><p>"The Das family has been staunch supporters of the McKelvey School of Engineering for many years, and we are extremely grateful for their loyalty," said Andrew D. Martin, chancellor of Washington University in St. Louis. "With their shared interests in different applications of electrical engineering, Bruno Sinopoli is a natural choice for the Das Family Distinguished Professorship in Electrical Engineering."<br/></p><p>"Professor Sinopoli's research is at the intersection of control theory and cyber-physical and network-systems," said Aaron F. Bobick, dean of the McKelvey School of Engineering and the James M. McKelvey Professor. "This interdisciplinary work is dramatically relevant to the now ubiquitous deployment of computing devices controlling physical systems. In addition, I expect Bruno's leadership to continue the strong upward trajectory of the department in terms of strength and relevance.  All of us are truly grateful to Santanu, Kabita, Atanu and Arnab Das for supporting Bruno's research through this professorship."<br/></p><p>Sinopoli joined Washington University Jan. 1, 2019, from Carnegie Mellon University, where he was a professor in the Department of Electrical & Computer Engineering and co-director of the Smart Infrastructure Institute. He also had appointments in the Robotics Institute and in Mechanical Engineering.<br/></p><p>In 2010, he received the George Tallman Ladd Research Award from the Carnegie Institute of Technology at Carnegie Mellon, as well as an NSF CAREER Award, which is awarded to junior faculty who model the role of teacher-scholar through outstanding research, excellent education and the integration of education and research.<br/></p><p>He joined the faculty at Carnegie Mellon as an assistant professor in 2007. Previously, he was a postdoctoral fellow at Stanford University and the University of California, Berkeley, where he earned master's and doctoral degrees. He earned a bachelor's degree in electrical engineering from the Università di Padova in Padua, Italy.<br/></p><p>The family of Santanu Das, chairman of the board of DomaniSystems Inc. in Shelton, Connecticut, established the Das Family Distinguished Professorship in Electrical Engineering in appreciation of the world-class education he received at Washington University. Whatever professional success he achieved, Das says that his Washington University experience "made it all possible."<br/></p><p>Das came to Washington University in 1969 to pursue graduate study. His wife, Kabita, joined him in 1971. After earning a doctor of science degree in electrical engineering in 1973, he joined ITT Corp. in Columbus, Ohio, then moved to ITT's corporate research center in Shelton, Connecticut. In 1988, he and three colleagues founded TranSwitch Corp., based in Shelton, Connecticut. The international company developed and marketed innovative high-speed semiconductor solutions for telecommunications and data communications equipment markets.<br/></p><p>Das retired from TranSwitch Corp. in 2009 and now serves on the boards of six high-technology companies.  <br/></p><p>Strong supporters of education and generous donors to Washington University, the Das family also has endowed the Robert Gregory Scholars Program in the Engineering school. Das received the university's Distinguished Alumni Award in 2001. He is a member of the National Council of the McKelvey School of Engineering and the New York Regional Cabinet and was a member of the university's Board of Trustees from 2000 to 2008. <br/></p><p>Mrs. Das, who earned an undergraduate degree in education from Calcutta University, has specialized in early childhood education. <br/></p><p>Sons Atanu and Arnab studied electrical engineering at the University of Illinois at Urbana-Champaign. Atanu, who earned bachelor's and master's degrees from the University of Illinois, earned a law degree at Loyola University Chicago. He lives with his family in the Chicago area, where he is a senior patent counsel with Guntin & Gust and also is a senior lecturer in residence at Loyola University Chicago School of Law, where he teaches several intellectual property courses. <br/></p><p>Arnab, who earned a bachelor's degree in electrical engineering from the University of Illinois at Urbana-Champaign, earned a doctorate in electrical engineering from Penn State University. He is a member of the senior professional staff at John Hopkins University's Applied Physics Laboratory in Laurel, Maryland. <br/></p><SPAN ID="__publishingReusableFragment"></SPAN><p><br/></p><p><br/></p>(From left): Dean Aaron Bobick, Santanu Das, Bruno Sinopoli, Marion Crane. Photo credit: Whitney CurtisBeth Miller 2020-01-27T06:00:00ZBruno Sinopoli has been named the Das Family Distinguished Professor in Electrical Engineering in the McKelvey School of Engineering. optical resonators gives researchers control over transparency<img alt="" src="/news/PublishingImages/EITUpdate.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>In the quantum realm, under some circumstances and with the right interference patterns, light can pass through opaque media.</p><p>This feature of light is more than a mathematical trick; optical quantum memory, optical storage and other systems that depend on interactions of just a few photons at a time rely on the process, called electromagnetically induced transparency, also known as EIT.  </p><p>Because of its usefulness in existing and emerging quantum and optical technologies, researchers are interested in the ability to manipulate EIT without the introduction of an outside influence, such as additional photons that could perturb the already delicate system. Now, researchers at the McKelvey School of Engineering at Washington University in St. Louis have devised a fully contained optical resonator system that can be used to turn transparency on and off, allowing for a measure of control that has implications across a wide variety of applications.<br/></p><p>The group published the results of the research, conducted in the lab of Lan Yang, the Edwin H. & Florence G. Skinner Professor in the Preston M. Green Department of Electrical & Systems Engineering, in a paper titled <a href="">Electromagnetically Induced Transparency at a Chiral Exceptional Point</a> in the Jan. 13 issue of <em>Nature Physics</em>.</p><p>An optical resonator system is analogous to an electronic resonant circuit but uses photons instead of electrons. Resonators come in different shapes, but they all involve reflective material that captures light for a period of time as it bounces back and forth between or around its surface. These components are found in anything from lasers to high precision measuring devices.</p><p>For their research, Yang’s team used a type of resonator known as a whispering gallery mode resonator (WGMR). It operates in a manner similar to the whispering gallery at St. Paul’s Cathedral, where a person on one side of the room can hear a person whispering on the other side. What the cathedral does with sound, however, WGMRs do with light — trapping light as it reflects and bounces along the curved perimeter.</p><p>In an idealized system, a fiber optic line intersects with a resonator, a ring made of silica, at a tangent. When a photon in the line meets the resonator, it swoops in, reflecting and propagating along the ring, exiting into the fiber in the same direction it was initially headed.</p><p>Reality, however, is rarely so neat.</p><p>“Fabrication in high quality resonators is not perfect,” Yang said. “There is always some defect, or dust, that scatters the light.” What actually happens is some of the scattered light changes direction, leaving the resonator and travelling back in the direction whence it came. The scattering effects disperse the light, and it doesn’t exit the system.</p><p>Imagine a box around the system: If the light entered the box from the left, then exited out the right side, the box would appear transparent. But if the light that entered was scattered and didn’t make it out, the box would seem opaque.</p><p>Because manufacturing imperfections in resonators are inconsistent and unpredictable, so too was transparency. Light that enters such systems scatters and ultimately loses its strength; it is absorbed into the resonator, rendering the system opaque.</p><p>In the system devised by co-first authors Changqing Wang, a PhD candidate, and Xuefeng Jiang, a researcher in Yang’s lab, there are two WGMRs indirectly coupled by a fiber optic line. The first resonator is higher in quality, having just one imperfection. Wang added a tiny pointed material that acts like a nanoparticle to the high-quality resonator. By moving the makeshift particle, Wang was able to “tune” it, controlling the way the light inside scatters.</p><p>Importantly, he was also able to tune the resonator to what’s known as an “exceptional point,” a point at which one and only one state can exist. In this case, the state is the direction of light in the resonator: clockwise or counter clockwise.</p><p>For the experiment, researchers directed light toward a pair of indirectly coupled resonators from the left (see illustration). The lightwave entered the first resonator, which was “tuned” to ensure light traveled clockwise. The light bounced around the perimeter, then exited, continuing along the fiber to the second, lower-quality resonator. </p><p>There, the light was scattered by the resonator’s imperfections and some of it began traveling counter clockwise along the perimeter. The light wave then returned to the fiber, but headed back toward the first resonator.</p><p>Critically, researchers not only used the nanoparticle in the first resonator to make the lightwaves move clockwise, they also tuned it in a way that, as the light waves propagated back and forth between resonators, a special interference pattern would form. As a result of that pattern, the light in the resonators was cancelled out, so to speak, allowing the light traveling along the fiber to eek by, rendering the system transparent. </p><p>It would be as if someone shined a light on a brick wall — no light would get through. But then another person with another flashlight shined it in the same spot and, all of a sudden, that spot in the wall became transparent.</p><p>One of the more important — and interesting — functions of EIT is its ability to create “slow light.” The speed of light is always constant, but the actual value of that speed can change based on the properties of the medium through which it moves. In a vacuum, light always travels at 300,000,000 meters per second.</p><p>With EIT, people have slowed light down to less than eight meters per second, Wang said. “That can have significant influence on the storage of light information. If light is slowed down, we have enough time to use the encoded information for optical quantum computing or optical communication.” If engineers can better control EIT, they can more reliably depend on slow light for these applications.</p><p>Manipulating EIT could also be used in the development of long distance communication. A tuning resonator can be indirectly coupled to another resonator kilometers away along the same fiber optic cable. “You could change the transmitted light down the line,” Yang said.</p><p>This could be critical for, among other things, quantum encryption.</p><p>The research team also included collaborators at Yale University, University of Chicago and the University of Southern California.<br/></p><SPAN ID="__publishingReusableFragment"></SPAN><br/><div><div class="cstm-section"><h3>Lan Yang<br/></h3><div style="text-align: center;"> <strong><a href="/Profiles/Pages/Lan-Yang.aspx"><img src="/Profiles/PublishingImages/Yang_Lan.jpg?RenditionID=3" alt="Lan Yang" style="margin: 5px;"/></a> <br/></strong></div><ul style="text-align: left;"><li>Edwin H. & Florence G. Skinner Professor</li><li>Expertise: Photonics, optical sensing, microresonators, lasers, non-Hermitian physics, parity-time symmetry in photonics<br/></li></ul><p style="text-align: center;"> <a href="/Profiles/Pages/Lan-Yang.aspx">>> View Bio</a><br/></p></div></div><div class="cstm-section"><h3>Media Coverage<br/></h3><div> <strong>Photonics Media: </strong> <a href="">Tuned Resonators Allow Control of Electromagnetically Induced Transparency</a></div></div> <br/>Electromagnetically induced transparency (EIT) is "tuned" by two particles on the optical resonator. (Image: Yang Lab)Brandie Jefferson has ramifications for quantum computing, communications and more<p>​Method has ramifications for quantum computing, communications and more<br/></p>