Dr. Paul E. Sheehan, a research chemist in the Surface Chemistry Branch of the Chemistry Division at the U.S. Naval Research Laboratory (NRL), was inducted as a Fellow of the American Vacuum Society (AVS) by Dr. Steven George, 2014 AVS President, and Dr. Ellen Fisher, 2014 AVS Awards Committee Chair, at the awards ceremony during the 61st Annual AVS International Symposium and Exhibition. Sheehan was named an AVS Fellow in recognition of his exceptional contributions to the detailed understanding of sp2 carbon nanostructure properties, methods for nanoscale patterning of materials, and the basis of biological and chemical sensor performance. Sheehan has studied nanoscale phenomena and surface reactions for over two decades. He was a University Fellow at the University of North Carolina where he received a bachelor's degree in Chemistry-based Materials Science in 1993 while doing undergraduate research in the group of Prof. Royce Murray. He then studied nanomechanics at Harvard University where he received his master's degree (1995) and his doctorate (1998) in Chemical Physics under the direction of Prof. Charles Lieber. He then received a National Research Council Fellowship to pursue biosensing using magnetoelectronics at NRL under the direction of Dr. Richard Colton. In 2001, NRL hired Sheehan to pursue research focused on the use of scanning probe microscopy for the fabrication and characterization of nanostructures. In 2008, Sheehan became Head of the NRL Surface Nanoscience and Sensor Technology Section. The Section is a highly interdisciplinary team comprising about fourteen biochemists, chemists, engineers, and physicists who study nanometer scale phenomena at surfaces as well as bioelectronics for sensing and biotic/abiotic interfaces. Sheehan's current research focuses on the chemical functionalization of graphene to enhance its performance in biosensing and electronics as well as the generation of nanostructures for interfacing with biology. His research has been funded by the Navy, Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, and Defense Threat Reduction Agency. The detailed exploration of the structures formed from sp2 carbon—fullerenes, carbon nanotubes, and graphene—has been a major focus of the physical sciences over the past three decades. The generation of these structures, the testing of their theoretically predicted properties, and their application have all met with substantial success. Some of Sheehan's earliest work explored the mechanical properties of carbon nanotubes and SiC nanorods, showing that the elastic modulus of the nanotubes matched the predicted (and superlative) value of ~1 TPa. This was achieved by using a scanning probe to push on nanotubes whose ends were pinned. ISI named the publication one of the top 10 papers in materials science for that decade. With the advent of graphene research, Sheehan explored the chemistry and functionalization of this fascinating material, helping to understand how new chemistries such as fluorination impacted its electronic, mechanical, and magnetic properties. Graphene's properties are quite subtle. Sheehan and co-workers recently showed that, unlike bulk graphite fluoride, fluorination of graphene was metastable and depends highly on the underlying substrate. He had previously explored this theme of graphene's interaction with its substrate in showing that electronic conduction in graphene on SiC is in fact anisotropic due to charge scattering by the underlying step edges. They subsequently published a series of papers exploring the changes in conduction in graphene due to functionalization, most recently showing that electronic conductivity in graphene can be completely eliminated by hydrogenation and then completely restored to its pristine state by simple heating. The manipulation of matter at the nanoscale has been a dominant theme in Sheehan's career. He has written several reviews on nanolithography as well as developed several advances in scanning probe techniques to modify locally both soft and hard materials. He made significant contributions to the understanding of the mode of patterning of Dip Pen Nanolithography (DPN), where material deposits from an AFM tip onto a substrate. He showed that a water meniscus was not needed to transfer molecules from the tip to the surface as previously thought, and offered a detailed model of the mass transfer processes occurring in the system. Based on the insights gained from that effort, he went on to develop a variant of DPN called thermal DPN where a heated scanning probe controlled the flow of a molecule by varying its viscosity. More recently, he has focused on using the heat scanning probes to pattern graphene into functional devices. This could mean either using thermal DPN to write thin polymer masks for subsequent processing or by creating molecular templates. A more fundamental insight was that the heatable scanning probes could control local temperature with nanometer resolution and so induce reactions at that length scale. This led to the highly local removal of oxygen from graphene oxide to form thin nanoribbons of conducting graphene. Beyond the manipulation of matter at the nanoscale, Sheehan has had an ongoing interest in the physical phenomena undergirding sensor performance. Upon arriving at NRL, he pursued a novel approach to biodetection where a magnetic bead would be bound to a giant magnetoresistive (GMR) sensor if a target biomolecule such as DNA was present. The benefit of this approach is that magnetic interference is relatively rare in biological systems and the giant response by the GMR sensor to the presence of the magnetic bead makes this a highly sensitive and selective approach. Indeed, it remains one of the most effective means of directly detecting low concentrations of biomolecules. Work on the microfabricated sensors stimulated his interest in the effect of scaling sensor size. In 2005, he published a simple paper on the scaling of biosensors to the nanoscale, a popular undertaking at the time. The upshot was that, for many applications, mass transport made this an unwise choice. Others used the results to point out that many reported results were in fact impossible. His interest in sensing extended to biological approaches to sensing where he modeled how magnetotactic bacteria know how to swim north. With his developing interest in graphene nanostructures, he set out to understand how to use this new material to build inexpensive yet sensitive detectors for both chemical and biological agents. The fundamental insight was that graphene oxide, a very inexpensive derivative of graphene, could be readily and cheaply formed into sensors that had lower electronic noise and greater amenability to chemical functionalization than the carbon nanotube networks used to date. Efforts to fully utilize and understand these new materials continue to this day. His research has garnered other recognition and accolades too. His nanofabrication work has been widely reported in the general science and popular press, including in the New York Times, CBS's SmartPlanet, C&EN, and TV Globo Brazil. His nanofabrication work was selected as a Department of Defense R&D accomplishment in Defense Nanotechnology Research and Development Programs. One of his biosensor papers was cited as the Most Outstanding Contribution out of >1000 submissions to the Biosensors 2008 conference, the leading conference in the biosensors community. It too was highlighted in the popular press in the Economist and on National Public Radio (NPR). In 2009, Sheehan and his co-inventors received the NRL Edison Patent award for their patent on Thermal Dip Pen Nanolithography. Sheehan also has received three Alan Berman Research Publication Awards in his 13 years as a federal employee. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.
News Article | August 24, 2016
Salt, fat, and sugar aren’t the cornerstones of a healthy diet. Unfortunately, greasy, salty potato chips and gooey chocolate-chip cookies taste pretty amazing. To help us eat less salt, fat, and sugar but not sacrifice taste, a group of researchers in France want to enlist our noses. At the American Chemical Society national meeting in Philadelphia on Monday, the scientists described how adding certain scents to foods enhanced their perceived saltiness. The team also reported a new technique to identify aroma molecules that boost desirable flavors. The goal, says Thierry Thomas-Danguin of the French National Institute for Agricultural Research is to help food producers make low-salt, low-fat, or low-sugar versions of products that still taste like the originals. Often, when a healthier version of a food doesn’t taste the same as the original, consumers reject it, Thomas-Danguin says. On the one hand, the consumer might stop buying the product and change to another one with a higher amount of salt, he says. “Or they could use table salt at home, and in that case, you still don’t reduce the daily intake of sodium.” Aromas can boost flavors, because our brains construct perceptions of how a food tastes from multiple sensory inputs, Thomas-Danguin says. What we experience as a flavor depends not only on taste information from our tongues but also on scent information from our noses, as well as other sensations from nerves in our mouths. Thomas-Danguin and his colleagues have focused on aromas, such as those of ham, bacon, and sardines, that can enhance the salty flavor of foods. During a talk in the Agricultural & Food Chemistry Division, he discussed his team’s recent studies involving what he calls model foods. “In one case, it’s cheese, but not like cheese you find at the market,” he says. “It’s cheese we cook by ourselves so we can control several parameters.” In a study of model cheese, the team found that sardine and butter aromas could compensate for a reduction in salt and fat content, respectively. In another study, the team made a flan-like custard with salt concentrated in one layer and a ham aroma added to another. This custard tasted as salty as a custard with 40% more salt, according to a panel of tasters. All of these studies have used commercially available aromas. Thomas-Danguin and colleagues now want to find new ones by isolating aroma molecules from foods. To do so, they’ve developed a technique involving gas chromatography and a device called an olfactoscan that wafts odors into people’s noses. The scientists have used the method to isolate several aroma molecules from fruit juices that enhance sweetness. The researchers use gas chromatography to separate aroma molecules from the gases that sit above juice, also known as the headspace. Instead of an analytical device sitting at the end of the chromatograph, the scientists ask a panel of people to sniff the aroma molecules coming out of the machine and associate them with a specific flavor. After further tests, including adding the aroma molecules back to the juice one at a time, the team settles on compounds that enhance the flavor they’re targeting. Besides continuing to find ways to enhance flavors via aromas, Thomas-Danguin and his team plan to further study the mechanisms behind how our brains process sensory information to construct our experiences of flavors.
Graphene, an atomically thin sheet of carbon, has been intensively studied for the last decade to reveal exceptional mechanical, electrical, and optical properties. Recently, researchers have started to explore an even more surprising property—magnetism. Theories and experiments have suggested that either defects in graphene or chemical groups bound to graphene can cause it to exhibit magnetism; however, to date there was no way to create large-area magnetic graphene which could be easily patterned. Now, scientists from the U.S. Naval Research Laboratory (NRL) have found a simple and robust means to magnetize graphene using hydrogen. This research has been published in Advanced Materials, January 20, 2015. The NRL scientists placed the graphene on a silicon wafer and then dipped it for about a minute into cryogenic ammonia with a bit of lithium. The group had recently shown that this is a quick and gentle method to add hydrogen atoms. They now see that the added hydrogen make the surface ferromagnetic. Because this method is so effective at adding hydrogen, one has to be careful about the length of exposure. Dr. Keith Whitener, NRL's Chemistry Division, explained: "This method of hydrogenation gives us access to a much wider range of hydrogen coverage than previous methods allowed, and too much hydrogen actually destroys the magnetism." However, once made, the magnetic graphene was of exceptional quality. Dr. Paul Sheehan, NRL's Chemistry Division, noted that "I was surprised that the partially hydrogenated graphene prepared by our method was so uniform in its magnetism and apparently didn't have any magnetic grain boundaries." Interestingly, the NRL group showed that the magnetic strength could be tuned by removing hydrogen atoms with an electron beam. The impact of the electrons can break the chemical bond between the graphene and the hydrogen, removing the hydrogen from the surface. Without the hydrogen, the graphene is no longer magnetic. As a result, by carefully controlling the path of the electron beam one can write magnetic patterns into the graphene (Figure). "Since massive patterning with commercial electron beam lithography system is possible, we believe that our technique can be readily applicable for current microelectronics fabrication," says Dr. Woo-Kyung Lee, materials research scientist in the Chemistry Division at NRL and project lead. Large arrays of magnetic features were quickly made, which would be particularly useful in applications from information technology to spintronics. The questions now facing the researchers are how fine the patterning of hydrogen can be and for how long the ferromagnetism can be stable. If those questions are answered, this technique could lead to a storage medium with a single hydrogenated-carbon pair storing a single magnetic bit of data, a roughly greater than million-fold improvement over current hard drives. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.
Ji Z.,Chemistry Division |
Doorn S.K.,Los Alamos National Laboratory |
Sykora M.,Chemistry Division
ACS Nano | Year: 2015
Polyclic aromatic hydrocarbons also called Graphene Molecules (GMs), with chemical composition C132H36(COOH)2 were synthesized in situ on the surface of transparent nanocrystalline indium tin oxide (nc-ITO) electrodes and their electronic structure was studied electrochemically and spectro-electrochemically. Variations in the potential applied onto the nc-ITO/GM electrodes induce only small changes in the observed current, but they produce dramatic changes in the absorption of the GMs, which are associated with their oxidation and reduction. Analysis of the absorption changes using a modified Nernst equation is used to determine standard potentials associated with the individual charge transfer processes. For the GMs prepared here, these were found to be E1,ox0 = 0.77 ± 0.01 V and E2,ox0 = 1.24 ± 0.02 V vs NHE for the first and second oxidation and E1,red0 = 1.50 ± 0.04 V for the first reduction. The charge transfer processes are found to be nonideal. The nonideality factors associated with the oxidation and reduction processes are attributed to strong interactions between the GM redox centers. Under the conditions of potential cycling, GMs show rapid (seconds) color change with high contrast and stability. An electrochromic application is demonstrated wherein the GMs are used as the optically active component. © 2015 American Chemical Society. Source
The U.S. Naval Research Laboratory's (NRL's) Dr. John N. Russell, Jr., head of the Surface Chemistry Branch of the Chemistry Division, was honored at the annual American Vacuum Society (AVS) awards ceremony with the top Societal honor, AVS Honorary Membership. Russell was recognized for his "outstanding scientific contributions and service to the Society." The award was a complete surprise to Russell. He attended the ceremony to witness the AVS Fellow induction of Dr. Paul Sheehan, whom he nominated. As the awards ceremony drew to an end, all of the present honorary members were asked to stand and be recognized. Then it was announced that someone would receive the Honorary Membership Award. The award is given irregularly, so there is never a guarantee that anyone will be so recognized at the ceremony. The Honorary Membership Award consists of a plaque and lifetime AVS membership without dues, and free registration for the annual AVS International Symposium and Exhibition for the rest of the honorary member's life. Dr. Richard Colton, former superintendent of NRL's Chemistry Division, nominated Russell for the award. Until it was revealed at the awards ceremony, only the awards committee, the AVS board of directors, a few AVS staff, and Dr. Barry Spargo, acting superintendent of NRL's Chemistry Division, knew about the award, that is until he conscripted Dr. Kathy Wahl, head of the Molecular Interfaces and Tribology Section, and Russell's wife, Kathleen Russell, to ensure Russell attended the AVS awards ceremony. It is AVS custom to announce a new honorary member through a slow reveal introduction. Using photographs from the awardee's childhood to the present, the details about the life and accomplishments of the awardee are presented to the audience. Russell said, "Once I saw the first childhood picture, I knew they were honoring me. I had to quickly think about what I would say when they called me to the stage. But, I was in such a daze that I was uncharacteristically without words. When I returned to my seat, my wife was sitting in my chair. I did not know she was at the ceremony. She deserves the recognition as much as me. I also am very fortunate that NRL has been very supportive of my endeavors on behalf of the greater scientific community. " A member society of the American Institute of Physics, the American Vacuum Society is an interdisciplinary scientific professional society that fosters an international community of scientists, engineers, and instrument manufacturers, who strive to promote research and communicate knowledge in the important areas of surface, interface, vacuum, and thin film science/technology for the advancement of humankind. As Head of NRL's Surface Chemistry Branch, Russell directs a highly interdisciplinary research program in surface chemistry and physics in support of current and future Navy technologies. The major research topics of the branch encompass a broad scope of fundamental to applied surface problems. They range from 3-D nanoarchitectural materials for energy storage, to lubrication and low-wear coatings, to surface (bio)adhesion, to chemical vapor deposition of electronic materials, to nanomanufacturing of devices and chemical/biological sensors. Russell's research at NRL initially focused on identifying and measuring fundamental surface reaction processes important for the chemical vapor deposition of wide band-gap electronic materials such as diamond and aluminum nitride, and then the surface functionalization of hybrid organic/semiconductor materials for sensor and electronic devices. Presently he and his collaborators are examining the biodegradation chemistry of polymer coatings and surfaces. Russell earned a bachelor's degree (cum laude) in Chemistry in 1981 from Dickinson College, and his doctorate in Physical Chemistry in 1987 from the University of Pittsburgh. After a Postdoctoral Fellowship at the Corporate Research Laboratory of Exxon Research and Engineering Company, he joined the NRL research staff in 1989. In 1999 he became the Head of the Functional Materials Section and since 2005 he has been the Head of the Surface Chemistry Branch. Russell has authored more than 50 peer-reviewed scientific research papers, which have been cited more than 3,300 times. He holds one U.S. patent. Russell has given numerous invited and plenary presentations about his research at universities, and international conferences. In 2013 he began a part-time detail at the Chemical and Biological Defense Department of the Defense Threat Reduction Agency where he is engaged in developing surface science programs within the chemical defense research portfolio. Russell has served in numerous leadership roles in the American Vacuum Society, which have included President (2008), member of the Board of Directors (2003-2005; 2007-2009), AVS Symposium and Exhibition Chair (2007), AVS Surface Science Division Chair (2006), and AVS Awards Trustee (2011-13, Chair 2013). He has significantly shaped and influenced the operations of the AVS. As AVS President he led a reorganization of the Society's governing structure, which was codified in changes to the Constitution and By-Laws of the Society. He also was instrumental in many changes to the policy and procedures of the Society. During his Presidency, the Society moved from rented to owned office space in lower Manhattan. He engaged in a review of the Society's research journals, which resulted in new policies for editor reviews, journal operations, and editorial directions. He also instituted a chair succession plan for the International Symposium, which still is the practice. As Awards Committee Chair, he completely revamped the awards selection process, even redesigning the physical awards that are presented to awardees. As Professor Joseph Greene, University of Illinois and Secretary of the AVS Board of Directors noted after the ceremony, "There are very few things that the AVS does today that were not initiated by John Russell." Russell also has held leadership positions in the American Chemical Society (ACS), including member and Chair of the ACS Joint-Board Council Committee on Publications (2005-13; Chair 2008-10), member of the ACS Colloid and Surface Chemistry Division Executive Committee (2000-16), and Chair/member of several special ACS taskforces and committees. Russell has been an elected representative to the ACS Council, the legislative body of the American Chemical Society (2004-09; 2011-13), and currently serves as an Alternate Councilor (2014-16). He also was a member of the editorial boards of the Encyclopedia of Colloid and Surface Chemistry (2004-present), and Chemical and Engineering News (2008-13; Chair 2008-10). He received the NRL Chemistry Division Young Investigator Award (1992), and the NRL Berman Research Publication Award (1997). In 2008 he was inducted into the Berwick (PA) Area High School Academic Hall of Fame. In honor of his research accomplishments and scientific leadership, Russell has been elected a Fellow of both the American Vacuum Society (2006) and the American Chemical Society (2010). About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.