Special Issue Preface pubs.acs.org/JPCC
Preface of Richard P. Van Duyne Festschrift and his dedication to mentorship. We highlight several of his most notable contributions to science below. Surface-Enhanced Raman Scattering. In 1974, Rick and his student David L. Jeanmaire were performing Raman spectroelectrochemistry of pyridine on roughened silver electrodes and noticed a significant enhancement in the intensity of the Raman signals. They estimated that the signals were 105−106 times larger than expected for this surface-bound species. Remarkably, in this original work they postulated that the roughened silver surface was causing a localized enhancement of the electric fields in the Raman process, leading to the intense inelastic scattering signals. This phenomenon, known as the electromagnetic enhancement effect in surface-enhanced Raman scattering (SERS), is now widely accepted as the dominant mechanism for the SERS process. Since the initial discovery, Rick has been instrumental in studies conclusively identifying the mechanism and maximum enhancements of the SERS process, including developing substrates for reproducible SERS measurements, extending SERS to the single-particle and single-molecule regimes, and broadly applying SERS to numerous sensing applications. Early studies from the Van Duyne group made the link between SERS and the localized surface plasmon resonance (LSPR) in nanostructured noble metal substrates. For this work, Rick and his colleagues developed several new substrates with tunable plasmon resonances that showed optimal enhancement for SERS. The simplest of these, known as metal film over nanospheres (or FONs), used metal deposited on a selfassembled layer of polymer or silica nanospheres assembled into a (roughly) hexagonal close-packed array to create a nanoscale roughened surface. Rick and his lab also invented a technique known as nanosphere lithography (NSL), wherein this same nanosphere layer was used as a deposition template to produce highly ordered arrays of nanotriangles. These substrates led to remarkable advances in the SERS community due to their uniformity, reliability, low cost, and simple control over the LSPR through judicious choice of nanopshere diameter, metal thickness, and metal deposition angle. The substrates were also instrumental in enabling a number of SERS sensing experiments, while allowing exploration of the fundamental relationships between SERS enhancement and nanoparticle properties including the complex relationship between SERS enhancement, excitation wavelength, and plasmon resonance as well as the distance dependence of the SERS phenomenon. More recent work by the group has included a series of papers on pushing the limits of detection of the SERS technique to the single-particle and single-molecule levels. Single-particle measurements have helped to characterize the structure of highly enhancing plasmonic regions, known as hot spots, and provided new insight into both structural and plasmonic features in nanoparticle aggregates that enable SERS detection down to the single-molecule limit. Moreover, the bianalyte approach
Photo by Lingxuan Peng
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t is our great pleasure to dedicate this special issue of The Journal of Physical Chemistry C to Professor Richard P. Van Duyne. Rick is best known for his work in the field of plasmonics, most notably in the discovery of surface-enhanced Raman scattering (SERS), but he has also made significant contributions to electrochemistry, biosensing, surface science, nanophotonics, and more. In his career to date, Rick has mentored more than 80 graduate students, 40 postdocs, 35 undergraduate students, and 11 high school teachers and has been a tireless champion of women in science, evidenced by the large number of women from his lab that have gone on to academic careers. Rick was born in 1945 in Orange, New Jersey. After finishing his B.S. at Rensselaer Polytechnic Institute in 1967, he moved to the University of North Carolina to work in the lab of Charles N. Reilley. There, Rick completed his Ph.D. in 1971, working on low-temperature electrochemistry and double potential step chronocoulometry. Rick then moved to Northwestern University in 1971 to begin his independent career, where he has remained for more than four decades. Rick is currently the Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern, with additional courtesy appointments in Applied Physics and Biomedical Engineering. He has won a number of prestigious awards, including the Earle K. Plyler Prize for Molecular Spectroscopy (American Physical Society), Ellis R. Lippincott Award (Optical Society of America), Charles N. Reilley Award (Society for Electroanalytical Chemistry), Sir George Stokes Award (Royal Society of Chemistry), E. Bright Wilson Award in Spectroscopy (American Chemical Society), Charles Mann Award in Applied Raman Spectroscopy (Society of Applied Spectroscopy), and the Theophilus Redwood Award (Royal Society of Chemistry). Rick was elected to the American Academy of Arts and Sciences in 2004, the National Academy of Sciences in 2010, and the American Institute for Medical and Biological Engineering in 2016. He is a Fellow of the American Association for the Advancement of Science, American Physical Society, Society of Applied Spectroscopy, and the Royal Society of Chemistry. Rick’s career has been defined by his research creativity, his interdisciplinary science, his collaborative spirit, © 2016 American Chemical Society
Special Issue: Richard P. Van Duyne Festschrift Published: September 22, 2016 20483
DOI: 10.1021/acs.jpcc.6b01795 J. Phys. Chem. C 2016, 120, 20483−20485
Special Issue Preface
The Journal of Physical Chemistry C
calculations to help explain the experimental results and assist in the design of optimized LSPR sensing platforms. By coupling appropriate capture layers to an LSPR sensor, the Van Duyne group has also demonstrated a number of highly sensitive and selective chemical and biological sensors. Select highlights include substrate binding to cytochrome P450, detection of calcium with a calmodulin sensor, and selective detection of adsorbed gases. Of particular note is work done to detect a biomarker for Alzheimer’s disease, wherein an antibody is immobilized on the surface of the nanoparticle array which can then capture an Alzheimer’s-specific antigen. A second antibody is then introduced and captured by the antigen, allowing a sandwich structure to be assembled on the sensor surface, leading to enhanced LSPR response from the NSL array. Tip-Enhanced Raman Scattering. In the past decade, the Van Duyne group has begun intense research on tip-enhanced Raman spectroscopy (TERS). In TERS, a sharp plasmonic tip is brought close to a sample and enhances only the region directly under the tip. When the tip is scanned over the surface, TERS can easily provide nanoscale chemical imaging information. Rick originally became interested in the potential of using scanning probes as SERS substrates a number of years ago with a scanning probe Raman microscope built and used as early as 1996. He and his group have made substantial progress in this arena in recent years through both ambient and ultrahigh vacuum TERS experiments. Using the isotopologue approach described above, they demonstrated single-molecule TERS in ambient conditions in 2012, and in collaboration with Lasse Jensen, developed a new model to explain the well-known intensity fluctuations associated with single-molecule Raman. More recently, Rick and his group have studied electrochemical reactions at the single-molecule level using changes in the TERS spectrum as a readout of the redox state of the molecule. The group has also developed a state-of-the-art ultrahigh vacuum TERS system, allowing for substrate and sample preparation to be performed in situ in order to maintain the ultimate cleanliness for single-molecule TERS studies. These studies have enabled spectral analysis of vibrational modes that serve as signatures for the adsorption geometry of molecules on pristine surfaces, which has important implications for understanding molecule−surface interactions for catalysis. Future work from the Van Duyne group in the TERS field is focused on coupling TERS with ultrafast Raman processes to follow chemical reaction dynamics at the ultimate limits of space and time. Outreach, Mentoring, and Collaboration. In addition to his research output, Rick has been a strong supporter of outreach activities throughout his career. At Northwestern, he brings undergraduate students and teachers into his lab for hands-on research experiences in plasmonics and nanoscience. To date, a remarkable 39 undergraduates have participated in these programs, many of whom have gone on to advanced degrees and careers in chemistry and nanoscience, as well as 11 local teachers. Rick is also a member of Chicago’s Museum of Science and Industry Advisory Council and helped to create an exhibit on nanoscience in 2006, which is still open to the public. Rick is also a founding member of the All Scout Nano Day at Northwestern University, a yearly event in which local Boy Scout and Girl Scout troops learn about nanoscience through experiments and lab tours. One of Professor Van Duyne’s greatest contributions to science has been in the training and mentoring of a tremendous number of scientists, many of whom have gone on to successful careers in industry, academic research, and teaching. To date, he
developed by the Van Duyne and Etchegoin groups has been widely adopted by the community as the best metric for proof of reaching this ultimate limit of detection. Throughout all of these experiments, Rick’s close work with his Northwestern University colleague George C. Schatz has led to numerous publications, which brought together Rick’s experimental results and George’s theoretical predictions, leading to a comprehensive picture of the SERS mechanism. The Van Duyne group has also extended the SERS phenomenon to chemical and biological sensing, investigating diverse molecules such as cytochromes, porphyrins, myoglobin, chemical warfare agents, and Anthrax markers. A dominant theme in the SERS sensing work by the Van Duyne group is in the selective detection of glucose in vivo. A real-time implantable glucose sensor would eliminate the need for frequent blood draws by diabetics and would provide rapid and quantitative information on blood glucose levels. The Van Duyne group has conclusively shown that a SERS glucose sensor has the required sensitivity and selectivity for a successful glucose monitoring device. Key to this work was the development of a glucosespecific capture layer on the SERS substrates, which has enabled continuous, quantitative in vivo detection of glucose in rats for weeks. In recent years, the Van Duyne group has demonstrated that spatially offset SERS can be used beyond the complexity of in-blood sensing to do molecular detection though highly scattering media such as bone. Also in recent years, Rick’s attention has turned to using SERS for art conservation, in collaboration with the Art Institute of Chicago. By exploiting the high sensitivity and minimally invasive nature of SERS, Rick’s group has been able to identify trace amounts of dyes in classic works of arts, allowing art restoration specialists to clarify how the paintings appeared in their original form. This work also allows for art authentication, by allowing rapid identification of dyes associated with specific periods of time. This work has not only led to multiple scientific publications but also been highlighted in the mainstream media, such as The New York Times, serving as a powerful illustration of the importance of science to real-world problems. Localized Surface Plasmon Resonances and Sensing. The NSL technique described above also provided useful substrates for LSPR sensing, an active area of research in the Van Duyne group since the late 1990s. Because the frequency of the LSPR is highly sensitive to the dielectric properties of the surrounding medium, changes in this environment can be monitored with extremely high precision by monitoring spectral shifts in the LSPR spectrum. As with SERS, Rick and his group have performed a series of fundamental and applied studies in the field of LSPR sensing. Early work on NSL arrays showed how nanoparticles with different height, size, and shape changed the sensitivity of the LSPR to the local environment, while the use of selfassembled monolayers of varying thickness allowed the distance dependence of the LSPR sensitivity to be probed. This platform was also used to show that coupling between electronic resonances of molecules and plasmon resonances of metallic nanostructures could yield extremely large (or extremely small) LSPR shifts, based on tuning the resonance overlap. This fundamental LSPR work was later extended to the singlenanoparticle level, where correlated spectral and structural studies allowed subtle effects such as shape heterogeneity, tip curvature (in structures such as nanoprisms), and internal crystallinity to be correlated with the sensing ability of various plasmonic structures. Collaborations with George Schatz continued to guide these studies by providing corresponding 20484
DOI: 10.1021/acs.jpcc.6b01795 J. Phys. Chem. C 2016, 120, 20483−20485
Special Issue Preface
The Journal of Physical Chemistry C has had a remarkable 83 graduate students and 42 postdoctoral scholars during his career at Northwestern University. A number of graduates from his lab have gone on to impressive academic careers and have continued to broaden the field of plasmonics and nanoscience, including several contributions in this special issue. He has been a tireless advocate for women in science. In recognition of his mentoring efforts, Rick was the co-recipient of the 2005 Nobel Laureate Signature Award for Graduate Education from the ACS. Rick has also been a generous collaborator, working with colleagues at both Northwestern and outside the university. He has a longstanding collaboration with George Schatz (generating an impressive 69 joint publications) and has also worked with Tamar Seideman (11 joint publications), Mark Ratner (9 joint publications), Mark Hersam (13 joint publications), James Ibers (25 joint publications), Chad Mirkin (10 joint publications), and Peter Stair (11 joint publications) at Northwestern. Rick is currently PI of an AFOSR MURI grant that reaches across multiple institutions to study nanoscale electrochemistry and is a member of an NSF Center for Chemical Innovation on Chemistry at the Space-Time Limit (CaSTL). His commitment to working with a wide range of scientists has kept the Van Duyne research program at the leading edge of science, and he continues to produce impressive numbers of publications every year. This enviable career, including long hours, intense deadlines, and much travel, has been supported and enabled by Rick’s wife, Jerilyn Miripol, a poet, writer, and writing therapist, who inspires him to push his own creative limits.
Christy L. Haynes Renee R. Frontiera Katherine Willets
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DOI: 10.1021/acs.jpcc.6b01795 J. Phys. Chem. C 2016, 120, 20483−20485
