Megan L’Heureux

s inaugural Emerging Leader in Atomic Spectroscopy Award is highlighted.

George Chan, a project scientist at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California, has won the inaugural Emerging Leader in Atomic Spectroscopy Award, which is presented by 

 magazine. This new annual award recognizes the achievements and aspirations of a talented young atomic spectroscopist, selected by an independent scientific committee. The award will be presented to Chan at the 2017 European Winter Conference on Plasma Spectrochemistry (EWCPS), where he will give a plenary lecture.

 created this award as a way to recognize and encourage leaders of the next generation of atomic spectroscopists. Chan’s work thus far in his early career includes shining examples of achievements in inductively coupled plasma–atomic emission spectroscopy (ICP-AES), laser-induced breakdown spectroscopy (LIBS), laser-ablation molecular isotopic spectrometry (LAMIS), and ambient ionization mass spectrometry. He is indeed a standout in the field.

	Chan received his Bachelor of Science degree, with 1st Class Honor and a chemistry major, from the University of Hong Kong in 1997. He then worked as a teaching assistant in the Department of Chemistry at the University of Hong Kong from 1997 to 1999 with Associate Professor Wing-Tat Chan, while pursuing his master’s degree. Chan completed his master’s degree in 2000, with a thesis titled “Investigation of Matrix Effects on Excitation Conditions of Dry Inductively Coupled Plasma Using Laser Ablation.”

	During those studies, Chan had two stints, in 1998 and 1999, as a visiting scientist in the Advanced Laser Technologies Group at LBNL, where his advisor had previously done postdoctoral work. At LBNL, Chan began working with Richard Russo, a senior scientist.

	“Chan spent a summer at LBNL and it was immediately clear that he was a talented student,” said Russo. “He quickly learned our instrumentation and was able to perform experiments on dual laser ablation that led to several publications. He did the research and wrote the manuscripts-amazing work, and on par with the upper-level PhD students.” As a result, Russo decided to invite Chan back for a second summer in 1999 for another three months.

	Chan gained a few years of professional experience before taking on his next academic challenge. From 2000 to 2001, he worked as an associate consultant in the Chemistry and Metallurgy Division at the Hong Kong Productivity Council in Hong Kong, and from 2001 to 2002, he worked as a research assistant in the Department of Chemistry at the University of Hong Kong.

	Chan maintained close contact with his former advisor, Wing-Tat Chan, over the years. “From my point of view, Chan never really left. Before he went to the United States, he visited the laboratory frequently and advised students in the group on their research and careers,” said Wing-Tat Chan. “He managed to come back to Hong Kong almost every year during his PhD study and therefore still knows the group well. He is the big brother to several generations of my research students.”

	In 2002, Chan went to the United States to pursue his doctorate at Indiana University, in Bloomington, Indiana, under Professor Gary M. Hieftje. Chan completed his PhD in 2007, with a thesis titled “Fundamental Mechanisms and Diagnostic Tools for Interference Effects in Inductively Coupled Plasma-Atomic Emission Spectrometry.” Chan stayed at Indiana for postdoctoral work, and in 2008, he was promoted to assistant scientist, and remained there until 2012.

	Hieftje noted that Chan came to his laboratory following guidance from Russo. “Russo was previously a graduate student in my research group and I took it as the strongest sort of compliment that he would urge Dr. Chan to join us,” said Hieftje. “After performing brilliant doctoral research, Dr. Chan stayed on in my research operation, first as a postdoctoral associate and later as an assistant scientist, which is a faculty position, but oriented toward research rather than teaching.”

	In 2012, Chan left Indiana University for a position as a project scientist in the energy technologies area (formerly the environmental energy technologies division) at LBNL, where he remains today. “When Chan was looking to leave Indiana University for a career position, the timing was perfect in that we had funding at LBNL for a position that would accommodate him,” said Russo, adding that Chan took a risk in accepting the role, because it was a temporary research position. “Since that time, about three years ago, we have been able to secure funding to create a more permanent position for Chan at LBNL,” Russo said.

	In that role, Chan has been successful in obtaining funding from the Department of Energy (DOE) for several of his proposals. “The DOE is great for supporting next-generation scientists for National Nuclear Security Administration (NNSA) and other programs,” Russo said.

	“Chan is one of the key scientists in the LBNL laser spectroscopy group,” said Russo, noting that Chan has already published several excellent manuscripts and received many invited lectures related to his research there. “I learn tremendously from him. One of the greatest parts of my job is being around, and learning from, talented young scientists like Chan.”

	Though young, Chan has already made significant contributions to analytical chemistry and atomic spectroscopy. One of Chan’s most significant contributions to the field of atomic spectroscopy has been his work on matrix effects and excitation processes in ICP, where he discovered several new phenomena and mechanisms. One breakthrough was his discovery that matrix elements having low second ionization potentials produce the strongest matrix effect, even though it had been widely reported in the literature that elements with low first ionization potentials produced the strongest effects. He also found that another critical parameter that governs the severity of the matrix effect is the presence or absence of low-lying energy levels in the doubly charged matrix ion; this behavior showed a very strong correlation with Penning ionization. This work cleared up some confusion in the ICP community about the importance of Penning ionization.

	Chan also explained, for the first time, that charge transfer and matrix interferences in the ICP can be linked together. He then showed how to exploit plasma-related matrix effects to study charge transfer in the ICP. With his novel procedure, candidate charge transfer levels can be easily and rapidly screened and identified. Chan also provided experimental evidence that state-selective charge transfer exists even in the atmospheric-pressure ICP. These pioneering findings provide a crucial step in understanding fundamental mechanisms in the ICP.

	Chan’s colleagues have taken notice of this groundbreaking research. Michael Webb, an associate professor at the University of North Carolina in Wilmington, said he was impressed by Chan’s contributions to understanding and correcting for matrix effects in ICP and other atomic spectroscopy techniques. “ICP is sometimes viewed as a solved problem because it has been so successful and because it is a relatively old technique,” said Webb. “The reality is that there is still reason to improve on even such an established technique, and Chan has shown that there is still room to do so.”

	Chan’s research interests also include practical aspects of analytical atomic spectrometry. For example, Chan developed diagnostic tools to flag the presence of interferences so that immediate remedial work can be undertaken by an analyst. His developed matrix-effect indicator and method for interference compensation do not require the addition of external reagents to the sample or any prior knowledge about the content of the sample. In addition, they can be readily adopted on commercial ICP-AES spectrometers, can be easily automated, can be used during an analysis with no time penalty, and require no extra input or sample treatment by the analyst.

	Steven Ray, the Winkler Assistant Professor of Chemistry at the State University of New York at Buffalo, said that Chan’s work developing this diagnostic tool is a great example of his ability to take an observation from a fundamental study and turn it into a practical purpose. “In Chan’s development of the spatially resolved emission maps as a flag for matrix effects in the ICP (and now elsewhere), he was able to use an observation from his fundamental studies of the ICP to devise a system that can immediately indicate the presence of a nonspectroscopic matrix effect in an analysis (something that still plagues ICP-AES analyses),” he said.

					George Chan and a member of the Horiba French research team during the installation of the Horiba instrument in the laboratory in Bloomington, Indiana, in 2005.
					Photo courtesy of Jean-Michel Mermet.

	Hieftje considers Chan’s studies into methods for detecting the presence of matrix interferences to be his most important work so far. Many elemental determinations by ICP emission spectrometry yield erroneous results because of the unrecognized presence of matrix interferences, Hieftje explained, and that such interferences arise when other constituents in a sample affect the emission intensity of the target analyte. “To avoid such errors, most experienced analysts must resort to time-consuming and error-prone methods, such as internal standardization, matrix matching, or standard additions,” he said. “With Dr. Chan’s invention, based on the spatial behavior of analyte emission, the existence of an interference can be readily detected and, if it is present, a location in the ICP can be found where the errors are minimal or absent.”

	Chan’s research interests also extend into optical isotopic analysis. Chan investigated the potential advantages of using multiple emission lines in the isotopic analysis of uranium by LIBS. His work also revealed that the primary factor dictating analytical precision is not the magnitude of an isotope shift but rather the signal-to-background ratio. Recently, he combined femtosecond-laser filamentation with LAMIS and demonstrated the first remote isotopic analysis with laser filamentation. This study combines existing knowledge about isotopic shifts in emission lines with modern-day technology (computers and a femtosecond laser) to further advance the analytical capability of optical spectrometry for isotopic analysis at potentially remote distances.

	Russo thinks Chan’s work is just beginning in these optical isotopic areas, noting that Chan is quick to let people know that he is an “optical” spectroscopist, not a mass spectrometrist. “Chan understands the fundamental physics and chemistry of optical transitions in atomic and molecular spectroscopy, and the practical issues with spectroscopic measurements,” said Russo. “He has done marvelous work showing the use of optical spectra for isotopic analysis. This is a new field and one I think where Chan will continue to make significant contributions.”

	Chan has also made noteworthy contributions to the characterization of fundamental mechanisms in plasma sources used in ambient ionization mass spectrometry. Although ambient ionization mass spectrometry is widely used, the processes for generating the key reagent ions in the ionization sources are not yet fully understood. Chan’s paper on this topic altered the thinking about the underlying mechanism of reagent-ion generation in plasma-based ambient ionization sources; before his work, it was thought that metastable helium atoms were the only important species in these sources. Since its publication in 2011, this work has already been cited 60 times and has the highest rate of citation of any of his published works (currently 10 citations/year).

	Jacob Shelley, an assistant professor and the Alan Paul Schulz Career Development Professor of Chemistry at Rensselaer Polytechnic Institute, cited Chan’s work in ambient ionization mass spectrometry as one of his greatest contributions so far. Shelley explained that this work was done while they were both working in Professor Hieftje’s lab and in collaboration with Professor Graham Cooks’s group at Purdue University. They used a variety of optical spectroscopic approaches to better understand ionization mechanisms of a helium dielectric-barrier discharge (the so-called “low-temperature plasma probe”) for use in mass spectrometry. While examining data obtained during those collaborative visits, Chan noticed some odd trends in the Boltzmann plots for N

 emission in the plasma. Digging deeper in the plasma-physics literature and the data they had, Chan postulated a series of mechanisms that involve helium dimer ion (He

) serving as an energy carrier from the plasma into the open atmosphere, which leads to reagent-ion formation. “To this day, it is one of the most beautifully crafted and presented studies I have seen,” said Shelley. “I am fortunate to have worked with him along the way.”

	To date, Chan has published 51 papers and presented 55 talks at scientific conferences, including 14 invited lectures and 41 contributed oral presentations. He was also awarded a patent in 2010 with Professor Hieftje for their work with ICP–AES (1).

	Ray commented that the works Chan has published in fundamental spectrochemistry in the ICP and other plasma systems have resulted in a fundamental understanding that has led to better practical utility of analytical measurement systems. “This represents a significant contribution in itself, and also one that will be long-lasting,” he said.

	Professor Kay Niemax, a Wilhelm-Ostwald-Fellow at the Federal Institute for Materials Research and Testing (BAM) in Berlin, Germany, said that despite the fact that Chan is still at the beginning of his career, he is already considered one of the leading experts in plasma spectrochemistry. “In that field he has published excellent papers documenting his manifold interests and capabilities,” said Niemax. “His publications on matrix effects and their corrections in element analysis by inductively coupled plasma-optical emission spectroscopy (ICP–OES) are considered the best research papers in that particular field.”

	Chan has also been the recipient of many prestigious awards, fellowships, and grants over the years. A few of those include the 

 Atomic Spectroscopy Award (2013 and 2004), the Society for Applied Spectroscopy’s (SAS) Graduate Student Award (2006), the Kraft Fellowship from Indiana University (2006), and the Felix Haurowitz Award from Indiana University (2005)-just to name a few.

	Chan’s friends and colleagues appreciate more than just his outstanding work, referring to him as brilliant, hard-working, creative, and enthusiastic. He was also called a modest and congenial partner who is able to work alone or in a team setting.

	“He is knowledgeable, insightful, innovative, skillful, and always curious of everything related to science,” said Wing-Tat Chan. “George Chan is already recognized as one of the top scientists in analytical atomic spectroscopy.”

	Ray said that Chan is famous for being a hard worker, who loves to work off-hours on many occasions because it permits him the opportunity to focus completely on his measurements. But because “nobody can work 24/7,” Ray said, Chan built a custom autosampler system by taking apart an old dilution device and hacking the computer software for a commercial ICP-AES instrument. “He even went so far as to solder wires to specific keys on his keyboard to automate his measurements,” said Ray. “He called his creation ‘virtual George.’ So, if he couldn’t be in the lab, at least ‘virtual George’ could be there!”

	Gerardo Gamez, an assistant professor in the Department of Chemistry and Biochemistry at Texas Tech University, echoed Ray’s sentiments, adding that Chan does not set foot in the laboratory without a plan. Gamez also remembered “virtual George” in this context-as a tool that also allowed Chan to use his time well, by freeing him up from pushing the buttons in a long series of repetitive experiments so that he could spend more time analyzing data. “Chan does not leave any rock unturned with respect to data analysis,” said Gamez. “He is very meticulous in this sense and I think it is these characteristics, together with his determination, that have allowed him to make sense of very complex problems.”

	Wing-Tat Chan had a similar story to share about Chan’s combination of a systematic approach and innovative thinking. Chan’s final year undergraduate project involved the investigation of combining a capacitively coupled plasma (CCP) with graphite furnace atomic absorption spectrometry (GFAAS), making use of the CCP to reduce the matrix effects in the AAS measurement. The instrument he was using was designed to be operated as either a conventional GFAAS or as a furnace atomic plasma excitation (emission) spectrometer (FAPES). The instrument documentation was sparse, with minimal descriptions of the hardware. Chan, a third-year undergraduate student at the time, probed the instrument using various methods to understand the implementation of background correction of the instrument and studied the plasma behavior versus furnace temperature and in the presence of water and metal ions. “He is systematic and methodological,” said Wing-Tat Chan. The project also demonstrated Chan’s ability to improvise. At the beginning of the project, the instrument was in disrepair, and a cone for the furnace interface was badly worn out. When Chan was waiting for the replacement cone to arrive (it took a few weeks for the overseas order), he came up with the idea of using a stainless steel cap for a teacup that was commonly available in local sundry markets. “The cap was eventually not needed, but his ability to improvise and innovate was abundantly demonstrated,” said Wing-Tat Chan.

	Jean-Michel Mermet, a retired research director with the Centre National de la Recherche Scientifique (CNRS) at the University of Lyon, and later a scientific advisor with Horiba-Jobin-Yvon, is equally impressed by Chan’s talents. Mermet said that Chan exhibits an excellent ability to combine fundamental studies and instrumentation. “Very quickly, with his very efficient analytical mind, he can understand what is interesting in the results of an experiment and what deserves further experiments to gain a better understanding of the various mechanisms involved in ICP-AES or LIBS,” said Mermet. “He is able to develop any instrumentation he may need to facilitate his research. Not only can he produce a huge amount of work, but he can also extract the useful information from it. Moreover, he may suggest very innovative concepts, such as those related to diagnosis and compensation for matrix effects. He is certainly one of the most brilliant researchers that I ever met.”

					George Chan and Steven Ray during a social event at Pittcon 2009.
					Photo courtesy of Jean-Michel Mermet.

	Chan also has interests and hobbies outside of the laboratory, and several people commented on his love of photography. “Chan takes beautiful photos of scenery and people that show his ‘other side’-as an artist,” said Wing-Tat Chan. Hieftje also commented on Chan’s love of spicy food, specifically hot buffalo wings that he favors whenever he is back in Indiana for a visit.

	With the number of accomplishments Chan has achieved so far in his young career, the future looks very bright for him-no matter which path he chooses going forward. His friends and colleagues agree.

	Webb foresees Chan starting his own research group, probably at an academic institution, soon. Niemax agreed.

	“George is a brilliant scientist with the strong desire and persistence to study and understand physical and chemical processes in detail. Therefore, I see his future in academia or scientific institutions that adopt basic science on their own,” said Niemax. “I am convinced that the scientific community can expect further important contributions from him, which will advance our knowledge in science.”

	Shelley had similar comments regarding Chan’s abilities, and expects that Chan’s interests and passion will soon lead to him becoming a professor at a top (“R1”) research institution, where he will mentor and teach outstanding students while exploring novel areas of optical spectroscopy and help pioneer precise isotope ratio measurements obtained with optical-spectroscopic means (the LAMIS technique described by Rick Russo and others at LBNL). “I was fortunate enough to be an indirect student of Chan’s for a few years and learned an enormous amount in that time,” he said. “Because of that, I am certain he will produce extremely intelligent, hard-working, and successful students in addition to the high caliber research he is already known for.”

	Russo has similar ideas in mind for Chan, but admits that he is a little biased and would prefer that Chan continue to work with him at LBNL. “I think many universities, laboratories, and industries would find him highly valuable. My preference would be for him to stay at LBNL and become one of the recognized scientists working with the laser spectroscopy team, and the greater laboratory,” said Russo. “However, I believe that his opportunities are completely open-both in terms of what research he decides to pursue and where he decides to reside.”

	Ray thinks that we are seeing Chan blossom as he expands his interests into other types of atomic spectroscopy, such as LIBS. “He can apply his deep understanding of spectrochemical phenomena to a wide range of problems in spectroscopy. Really, the sky’s the limit for Chan,” he said.

	As for the Emerging Leader in Atomic Spectroscopy Award that Chan is receiving this year, his friends and colleagues could not be happier for him. Shelley and Gamez both said there is no one more deserving of this inaugural award other than Chan. “It also sets a very high bar for future winners of this prize,” concluded Shelley.

	An in-depth interview with George Chan focused on his research, challenges, and accomplishments, will be published in the February 14, 2017, edition of our newsletter, 

. Another recent interview with Chan about his work with spatial heterogeneity can be found here: 

www.spectroscopyonline.com/what-icp-spatial-heterogeneity-reveals-about-interference-icp-aes-0

	2018 Emerging Leader in Molecular Spectroscopy: Now Accepting Nominations

	For information about how to nominate someone for the 2018 award, please see the call for nominations on our website: 

www.spectroscopyonline.com/emerging-leader-atomic

		G.C.-Y. Chan and G.M. Hieftje, U.S. Patent 7,768,639, 3 August 2010. 

magazines in Iselin, New Jersey. Direct correspondence about this article to: 

Articles

The winner of Spectroscopy's inaugural Emerging Leader in Atomic Spectroscopy Award is highlighted.

The 2017 Emerging Leader in Atomic Spectroscopy Award

’s inaugural Emerging Leader in Molecular Spectroscopy Award is highlighted.

	Matthew J. Baker, a senior lecturer in chemistry at the University of Strathclyde, in Glasgow, has won the inaugural Emerging Leader in Molecular Spectroscopy Award, which is presented by 

 magazine. This new annual award recognizes the achievements and aspirations of a talented young molecular spectroscopist, selected by an independent scientific committee. The award will be presented to Baker at the SciX 2016 conference in September, where he will give a plenary lecture and be honored in an award symposium.

 created this award as a way to recognize and encourage leaders of the next generation of molecular spectroscopists. The achievements that Baker has already made at this early stage of his career make it clear that he is indeed a standout in the field. His work also makes the future of the field look very bright.

	An Early Focus on Biomedical Applications of Vibrational Spectroscopy

	At Strathclyde, Baker leads interdisciplinary research rooted in fundamental studies to advance the use of analytical chemistry to real-world problems, particularly in biomedical and clinical applications. His main focus is the development of spectroscopic and spectrometric molecular pathology techniques, disease diagnosis, and detection of pathogenic bacteria and toxic chemicals. 

					Baker in his lab holding a slice of brain tissue.

	Baker’s focus on the use of vibrational spectroscopy for biomedical use was already well underway during his studies for his master’s degree in chemistry, which he received in 2004 from the University of Manchester Institute of Science and Technology (UMIST). Through his research on using Fourier transform infrared (FT-IR) microspectroscopy and multivariate analysis for diagnosing prostate cancer, he was able, for the first time, to correlate FT-IR spectra with the Gleason score (a measure of the microscopic appearance of a prostate tumor) and the clinical stage of the tumor at the time of biopsy.

	Peter Gardner, a professor of Analytical and Biomedical Spectroscopy at the University of Manchester, taught Baker in his first and final years at the university and was his academic advisor during his year in industry. “I supervised his final year project, so I guess I can claim to have set him off on his path to using IR spectroscopy,” said Gardner. “Although I was not his PhD supervisor, he did work in my lab for a period of time and did his first work on blood serum, which now forms a major part of his research.”

	Baker’s doctoral studies also focused on cancer diagnosis under the supervision of Dr. Nick Lockyer-in tissues and cells-but in this case using time-of-flight (TOF) secondary ion mass spectrometry (MS) combined with multivariate analysis and pattern recognition. He received his PhD from the Department of Chemical Engineering and Analytical Science at the Manchester Interdisciplinary Biocentre at the University of Manchester, and his thesis was a collaboration with the Paterson Cancer Research Institute.

	In 2011, Baker received a PGCert (postgraduate certificate) in International Studies from Staffordshire University. The certification covered international relations in the 20th century and diplomacy and the global world, which helped Baker understand the international arena he was working in. 

	After receiving his PhD in 2007, Baker held numerous fellowships and research positions. First, he received a Life Sciences Interface fellowship from the UK’s Engineering and Physical Sciences Research Council (EPSRC). This fellowship focused on biomedical applications of vibrational spectroscopy, mass spectrometry, and imaging and took him from the Manchester Interdisciplinary Biocentre in the UK, to the Robert Koch Institute in Berlin, Germany, and to Harvard Medical School in Boston, Massachusetts. During the same period, he had research fellowships at the Robert Koch Institute and at Harvard Medical School and Brigham & Women’s Hospital (also in Boston). At the Robert Koch Institute, he used vibrational spectroscopy combined with multivariate analysis-pattern recognition for the analysis of prostate cancer tissue; at Harvard medical School, he focused on multi-isotope imaging MS for the analysis of prostate cancer cell lines, prostate cell lines, and stem cells.

	Rohit Bhargava, a professor at the University of Illinois who is well known for his research on biomedical imaging using vibrational spectroscopy, praised Baker’s early studies on prostate tissue imaging. “This careful work spanning tissues, cell culture, and modalities permitted new insight and capabilities in using spectroscopy for understanding and typing prostate cancer,” he said. 

	Baker also had a stint as a visiting academic at the Centre for Biospectroscopy at Monash University in Melbourne, Australia, where he conducted research funded by the Royal Society of the UK to develop spectroscopic-based four-dimensional (4D) imaging molecular histopathology. 

	From 2010 to 2012, Baker also took on two roles with a somewhat different focus. In a position in the Detection Department at the UK’s Ministry of Defense, he was responsible for the technical leadership of research areas concerning spectrometry and spectroscopy for the detection of toxins and chemical and biological agents of interest. And in a research fellowship with the Optoelectronics Research Centre at the University of Southampton, he investigated the fabrication of nanostructured surfaces for surface-enhanced Raman spectroscopy (SERS) and their combination with specific recognition elements for biological detection and trace analysis.

	In 2012, Baker returned to academia, becoming a senior lecturer in toxicology and analytical chemistry with the Division of Chemistry School of Forensic and Investigative Sciences at the University of Central Lancashire. In 2014 he moved to his current role as a senior lecturer in chemistry in the Department of Pure and Applied Chemistry and Centre for Forensic Science at the University of Strathclyde. He is also currently a visiting fellow at the Universite de Reims Champagne-Ardenne in France with Professor Ganesh Sockalingum, where he teaches a seminar and develops research in bacterial and disease detection for the security and defense applications. 

	Since June 2013, Baker has also been an honorary fellow at the Royal Preston Hospital in Lancashire, which is part of the Teaching Hospitals National Health Service (NHS) Trust and Walton Centre NHS Trust. In this position, Baker is developing novel diagnostic methods based on spectroscopy for the clinical environment. Since October 2014, he has also been a visiting academic with the School of Forensic and Investigative Sciences at the University of Central Lancashire.

	Though young, Baker has already made significant contributions to analytical chemistry and molecular spectroscopy. In particular, Baker is doing pioneering work to advance the use of vibrational spectroscopy for clinical diagnostics. He has developed an accurate, reproducible, and repeatable method to diagnose and differentiate brain tumors via spectroscopic analysis of body fluids such as serum and plasma, and he is currently expanding this approach using novel light sources to enable rapid, high-throughput imaging. 

	“Baker used attenuated total reflection (ATR) mode and conventional FT-IR spectroscopy to demonstrate that body fluids can be used as ‘liquid biopsies,’ which is very impressive,” said Sergei Kazarian, a professor of Physical Chemistry at Imperial College London. “Differentiation of the severity of brain cancer using this approach appears very promising.” 

	Bhargava agreed. “Baker and his group have made impressive progress in this area and this is an emerging contribution that is exceptional,” he said.

	“Baker probably has the largest molecular spectroscopic study at the moment on serum diagnostics,” added John Chalmers, a consultant at VS Consulting.

	Nick Lockyer, who cosupervised Baker during his PhD and has collaborated on several research efforts with Baker, agreed that Baker’s greatest contribution to molecular spectroscopy so far is “developing clinical applications of vibrational spectroscopy, particularly for biofluids.”

	Baker has also contributed key papers to the field; organized, chaired, and developed clinical spectroscopy sessions at the SciX conference; co-organized a Faraday Discussion of the Royal Society of Chemistry on “Advanced Vibrational Spectroscopy for Biomedical Applications;” cowritten a concise physics e-book for the Institute of Physics; and guest edited three journal issues. Baker recently joined the editorial advisory board for 

, a journal of the Royal Society of Chemistry. To date, Baker has also published 53 papers, one book (

), and given 54 conference presentations.

	Recently, Baker coinstigated and coformed the UK Clinical Infrared and Raman Spectroscopy (CLIRSPEC) network, from which the nonprofit International Society for Clinical Spectroscopy has emerged, which has the specific aim to translate promising vibrational spectroscopy methods into the clinic. He is also a member of Raman4Clinics, a European consortium focused on the use of Raman spectroscopy in the clinic. In addition, Baker developed the successful CLIRSPEC Summer School, now in its second year, to provide an interdisciplinary education to a broad range of students interested in clinical spectroscopy. 

	“Much of the success of the CLIRSPEC summer school was because of Baker’s enthusiasm and organizational skills,” said Kazarian, who is on the management committee of CLIRSPEC and teaches in the summer school.

	Chalmers agreed. “The summer school initiative is an excellent example of Baker’s drive to engage with students in the bio-arena and advance their molecular spectroscopic understandings and developments,” he said.

	Baker is also a member of a number of professional groups including Chartered Chemist (CChem) with the Royal Society of Chemistry, Fellow of the Royal Society of Chemistry (FRSC), International Society for Clinical Spectroscopy, Infrared and Raman Discussion Group, British Association for the Advancement of Science (BA), Evidence Base (a database of specialists organized by the Sense about Science charity), and the Chartered Society for Forensic Science (MCSFS). In 2015, Baker also developed and held the world’s first Twitter poster conference, now in its second year.

	Baker has received significant funding for his work-54 grants so far. A few examples include the Global Exchange Programme (GEP) Award that Baker received in July 2006, which enabled him to undertake a period of study on MS imaging of model cell membranes at Pennsylvania State University. In November 2007, he received a Prostate Cancer Charity Research Grant that provided £15,000 for research with Peter Gardner of the Manchester Institute of Biotechnology into novel ways of diagnosing prostate cancer. In 2015, Baker was awarded a Royal Society International Exchanges Scheme grant for £5,990 in collaboration with Professor Rohit Bhargava for “Developing Discrete Frequency Infrared (DF-IR) Spectroscopy and Imaging.” In addition, Baker also received an Arts and Humanities Research Council (AHRC) Early Career Research Grant in collaboration with Dr. David Robinson (UCLan Archaeology) and Dr. Jennifer Perry (California State University) for £234,500 for research looking at portable spectroscopy for ancient Native American rock art analysis. To date, Baker has been awarded more than £1.5M in principal investigator funding and more than £3M in project team funding.

					Baker speaking at the SPEC 2016 conference in Montreal, Canada, where he announced that he will host SPEC 2018 in Glasgow from June 10–15, 2018. Photo taken by Sergei Kazarian.

	Baker also received the British Neuro Oncology Society Best Presentation Award in 2015 at the society’s annual meeting, the Departmental Physical Chemistry Prize in 2004 for the best undergraduate in physical chemistry, and a scholarship in 2000 in which he received £18,000 as a university scholarship from Universal Products Ltd. to help fund university studies.

					Baker on a mountain walk during the CLIRSPEC Summer School. Photo taken by Sergei Kazarian.

	Baker’s friends and colleagues are impressed with more than his work.

	Bhargava said that one of Baker’s most impressive qualities is his leadership. “He is working tirelessly to help the spectroscopy community. Whether it’s by organizing influential methods papers, entire conferences, or societies, his impact is already being felt,” he said. “This is truly exceptional for a young scientist. He should be commended for these contributions that go well beyond just research.”  

	In addition, Kazarian said, Baker has a very friendly and engaging personality. “This trait is very important in collaborative projects and in life in general too,” he said. He noted that Baker’s positive approach to his life and work extends to having a large spectroscopic tattoo on his arm that at first glance appears to be an interferogram. “As I recall, what Baker said to me is that it is a second derivative of an infrared spectrum of his blood serum,” he said. “Having a spectroscopic tattoo is an unusual but creative form of public outreach!”

	Where is Baker headed next? Based on the accomplishments he’s achieved so far in his career, the future looks very bright for Baker. His friends and colleagues agree. “Baker’s vision is to introduce serum spectroscopy for diagnosis and monitoring into clinics and outpatient departments, and he is moving toward this with multiple collaborating partners,” said Michael Jenkinson. Jenkison is a clinical senior lecturer and honorary consultant neurosurgeon at the University of Liverpool and has collaborated on various projects with Baker on brain tumor research, including developing serum monitoring of glioma response to treatment. 

	“Baker is an enthusiastic and talented researcher with great ambition to develop and deliver serum spectroscopy into routine clinical practice,” Jenkinson added.

	Gardner agreed. “Baker is going to go far. He has boundless energy,” he said. “Baker will continue developing the serum IR technology. His company will expand and he hopefully will bring a product to market.” Baker is currently setting up ClinSpec Diagnostic Ltd., a prospective spin out from the University of Strathclyde supported by the Scottish Enterprise High Growth Spin Out program. 

	Bhargava said Baker is one of the most insightful, energetic, and capable young spectroscopists in the world today. “He has a wealth of expertise and is working hard on relevant problems,” said Bhargava. “If all goes well, his methods may make the transition to clinical practice, which would be very exciting.”

	Lockyer agreed. “Baker has always been very ambitious and has quickly developed an international reputation is his field,” he said. “I have no doubt his career will go from strength to strength.”

	“I expect Baker to continue great research, but I also think he would develop and demonstrate his leadership in organizing and leading large research programs and I hope to collaborate with him on that,” said Kazarian.

	“Baker’s dynamic and enthusiastic work ethic and his research and academic contributions lead me to believe he will undoubtedly gain a professorship within the next 4–5 years,” added Chalmers. “Baker is truly well-deserving of this award you have honored him with and will be a shining example to future awardees.”

	An in-depth interview with Matthew Baker focused on his research, challenges, and accomplishments, will be published in the September 19, 2016 edition of our newsletter, The Wavelength.

	2017 Emerging Leader in Molecular Spectroscopy: Now Accepting Nominations

	For information about how to nominate someone for the 2017 award, please see the call for nominations on our website: www.spectroscopyonline.com/view/call-nominations-2017-emerging-leader-molecular-spectroscopy. 
	 

 magazines in Iselin, New Jersey. Direct correspondence about this article to: meg.l’heureux@ubm.com

Matthew J. Baker, the winner of Spectroscopy’s inaugural Emerging Leader in Molecular Spectroscopy Award, is passionate about solving clinical problems with vibrational spectroscopy.

The 2016 Emerging Leader in Molecular Spectroscopy Award

's celebration of 30 years covering the latest developments in materials analysis, we asked a panel of experts to assess the current state of the art of Raman spectroscopy and to try to predict how the technology will develop in the future. 

	Sir C.V. Raman discovered Raman spectroscopy in the late 1920s, which is where the nomenclature comes from (1). In the eight decades since that discovery, Raman spectroscopy has had plenty of time to mature, yet users continue to find new application areas for the technique. In celebration of this 30th year of 

, we asked a panel of Raman experts about the current state of Raman spectroscopy-including the various advanced subsets of Raman such as stimulated Raman scattering (SRS), coherent anti-Stokes Raman scattering (CARS), and tip enhanced Raman scattering (TERS)-including recent advances, ongoing challenges, and possible future developments. This article is part of a special group of six articles covering the state of the art of key techniques, also including infrared (IR) spectroscopy, near-infrared (NIR) spectroscopy, inductively coupled plasma–mass spectrometry (ICP-MS), laser-induced breakdown spectroscopy (LIBS), and X-ray fluorescence spectroscopy.

	We started by asking our experts what they considered the most important development in Raman spectroscopy or its instrumentation in the last 5–10 years. The answers covered a variety of advances and specialized application areas, making it clear that Raman continues to break through its limitations and find new ways to support the fields of research and industries where it is used.

	Dennis J. Walls, a senior research associate at DuPont, is excited about the progress in SRS and CARS that has made Raman imaging more practical in terms of speed and applicability. “Developments in coherent Raman scattering microscopy approaches such as SRS and CARS microscopy offer exciting potential in biological imaging applications,” Walls said. He also mentioned the importance of TERS. “I also am excited about the potential for sub-diffraction limited microscopic approaches like TERS, which are now crossing boundaries of spatial resolution that have previously not been accessible with normal Raman microscopy.”

	Zachary D. Schultz, an associate professor of chemistry and biochemistry at the University of Notre Dame, agrees that TERS is an important development. “The understanding of the relationship between plasmon resonances and Raman signal enhancements has rapidly advanced in the last decade,” Schultz said. “This is evident in the increased interest in surface-enhanced Raman scattering (SERS) for applications and the emergence of TERS for sub-diffraction imaging.” Schultz explained that recent work has taken advantage of this understanding, demonstrating the reproducibility and quantitative capabilities of SERS and TERS. “It is really becoming possible to talk about using Raman to investigate individual molecules,” Schultz concluded.

	Heinz W. Siesler, a professor at the University of Duisburg-Essen, said that handheld Raman was the most important recent advance. Gary Johnson, a research Chemist at Intertek, agreed. “I am very interested in the development of compact, portable instruments that have the capability to obtain spectra equivalent to the performance of benchtop systems,” Johnson said. This is valuable, he said, because there are a lot of potential applications of Raman spectroscopy for which it is impractical to bring samples into a laboratory.

	John A. Reffner, a professor at John Jay College of Criminal Justice in New York, said that solid-state lasers and the development and application of optical filters for Rayleigh scattering rejection have had the greatest impact on Raman instrumentation.

	From a different perspective, Juergen Popp, a professor of physical chemistry at Friedrich-Schiller University Jena and the Leibniz Institute of Photonic Technology Jena, said that the most important recent advances have been developments in instrumentation that have pushed Raman spectroscopy further into life sciences and biomedicine. “This development was certainly triggered by the technical progress made in spectrometer, detector (charge-coupled device [CCD]), and filter (notch filter) technology,” said Popp. “These technological advancements made Raman spectroscopy accessible for a broad circle of users because of the availability of commercially available and fairly easy-to-use Raman setups, in particular, confocal Raman microscopes.” The availability of confocal Raman microscopes allowed for label-free molecular characterization of biological cells and tissue with a spatial resolution in the submicrometer range, he said. “This paved the way for medical Raman spectroscopy, that is, Raman spectroscopic clinical diagnosis,” he said.

	These advances wouldn’t have been possible, he noted, without the simultaneous achievements in statistical Raman data analysis-that is, the development of innovative chemometric strategies to analyze Raman spectra of biological specimens. “In other words, I consider the development of innovative chemometric approaches to qualitatively and quantitatively analyze Raman images with respect to utilizing the Raman signatures for diagnostic purposes as one of the most important aspects in biomedical Raman spectroscopy,” he said.

	Despite these important advances, however, fluorescence background response still limits the use of Raman spectroscopy for many applications of interest. In light of this, we asked our panel the following questions: How much of a problem is this in your work? What tools do you have to eliminate it? Are there any additional developments anticipated that could lead to significant improvements in dealing with this problem in the near future?

	All of our panelists agreed that fluorescence is a common problem in their work. Walls said that fluorescence is one of the “major factors that limits applications for Raman spectroscopy” to the varied analyses that come through his laboratory.

	Reffner agreed. “Fluorescence creates an uncertainty that limits the reliability of using Raman for analysis of some samples,” he said.

	Johnson said he runs into this problem frequently, particularly with industrial samples and materials that contain natural products. Schultz agreed that background signals are still a problem. “In SERS and TERS, the metals often provide some fluorescence quenching, but molecules distant from the nanostructures can still cause problems,” said Schultz.

	Most of our panelists said they use excitation wavelength selection to mitigate the problem of fluorescence.

	Popp’s main focus lies in the application of Raman spectroscopic approaches for biomedical diagnosis, so he primarily uses excitation wavelengths in the NIR region (mostly 785 nm) to avoid the excitation of fluorescence. Siesler agreed that NIR excitation is the best approach. “The recently patented sequentially shifted excitation (SSE) technique (2) might possibly help to suppress fluorescence, but I have not had the opportunity to test it yet,” he said.

	Walls said that he also uses NIR excitation at 785 nm to avoid fluorescence, but even then, many classes of samples remain outside of the scope of application for Raman spectroscopy because of fluorescence background issues. “Alternatively, excitation at 1064 nm can address some of these samples,” he said.

	Another approach that Popp’s laboratory is pursuing is the use of excitation wavelengths in the deep ultraviolet (UV) at 244 nm. “The application of deep UV wavelengths also avoids fluorescence since most fluorophores do not show fluorescence below 250 nm,” he said. He noted that this deep UV approach is especially powerful for mineralogical studies. “Furthermore, I think shifted excitation Raman difference spectroscopy is a powerful approach to eliminate fluorescence.”

	Johnson mentioned photobleaching as an alternative that is sometimes effective, but otherwise he agreed that 785-nm or near-infrared 1064-nm lasers were the best tools to eliminate the fluorescence problem.

	Finally, Reffner said that SERS is showing “real progress in reducing the fluorescence problem while amplifying the Raman scattering.”

	A few of our panelists suggested some future developments that might help to solve the fluorescence interference problem. Schultz explained one possible approach: rapidly switching the laser frequency over a small wavelength range. This technique would change the Raman signal but not the fluorescence. “Incorporating this or similar ideas into commercial instruments may resolve the fluorescence background problem at some future time,” he said. He added that the advent of NIR cameras and array detectors makes Raman possible with excitation wavelengths that do not cause fluorescence. “These new technologies are helping to resolve this problem,” Schultz concluded.

	Walls said that continued advances in the incorporation of the 1064-nm excitation source in dispersive instruments would allow practical data collection (from the standpoints of time and laser power) and would be an important advance.

	Popp said that a technical improvement to avoid fluorescence interference could be the development of fast detectors to separate fluorescence and Raman scattering in time. “One example of this is superconducting nanowire single-photon detectors” he said.

	Recent reports of the successful use of Raman spectroscopy for important biomedical applications are quite exciting. These applications include imaging for disease diagnosis, including significant improvements for endoscopic probes, and identification of microorganisms. We asked our panelists for their opinions about the practicality of implementing these technologies in the clinical environment.

	Siesler said that the implementation of these technologies as routine tools would likely be very slow. “The promises in various ads are too optimistic,” he said.

	Popp had a more positive outlook on the work being done in this area, which is the focus of his research group. He has observed an enormous increase in the development and application of Raman-based approaches to address biomedical questions. “The ability to obtain specific chemical information label-free makes Raman spectroscopy attractive for many applications in clinical diagnostics of bodily fluids, pathogens, cells, and tissue biopsies,” he said. “I am absolutely convinced that Raman spectroscopy might be the solution for many clinical challenges that have unmet medical needs, for example, in the early detection of cancer.”

	As another example, Popp mentioned the significant progress made toward the application of Raman spectroscopy as a point-of-care test for the fast identification of pathogens (such as sepsis-causing pathogens) and the determination of their antibiotic resistances. “Overall, I am sure that a few years from now we will see the first Raman approaches as standard diagnostic or therapeutic tools in daily clinical practice,” he said.

	Schultz agrees that nonlinear Raman techniques have a lot of potential in the biomedical imaging community. “The label-free, video-rate images that are obtainable may have a tremendous impact on identifying cancerous tissue or other abnormalities,” he said.

	“In respect to identifying microorganisms, rapid assays based on SERS are really starting to make an impact,” Schultz said. He explained that applications identifying tuberculosis, flu viruses, and other pathogens have all been demonstrated already. “Handheld Raman instrumentation may make these assays highly portable and inexpensive,” he said. Schultz also said that work with high-throughput detection with moving fluids, such as chromatography, flow injection analysis, and microfluidic approaches, is another important advance for clinical environments. “I think Raman has an important future in the biomedical community,” he concluded.

	Johnson added a caution, however, noting that the primary challenge in applying Raman to clinical use lies in data analysis and interpretation. “Considerable care is needed to avoid misdiagnosis, especially when using chemometric methods that don’t rely on well-defined spectral features,” he said.

	Many problems at the frontiers of materials science require spatial resolution that is outside of the diffraction-limited regime. Sub-diffraction-limited approaches like TERS seem to offer the potential to bridge this gap, but currently the approach does not appear to be practical because of the difficulty in preparing tips. So we asked our panelists if they thought TERS-like approaches to Raman imaging would someday become more practical.

	“This remains an important opportunity for Raman spectroscopy that could be put to work today with practical instrumentation offerings and a ready source of appropriate tips,” said Walls. “In addition to biological systems, the increasing importance of structural organization at the nanoscale in materials science calls for characterization approaches that can operate in this size regime.”

	Schultz said he was not sure if the difficulty is really preparing tips. “I think the biggest obstacle to TERS is false expectations,” he said. “Many TERS tips perform exactly as expected; however, the observed signal enhancement from a single nanostructure on a single or small number of molecules, or in complex samples, is not always that large.”

	Schultz added that the advances in commercial TERS instruments is helping practicality, but also increasing frustration when people cannot get the expected result. “I think TERS has significant potential and will be an important technique, but it will also have its limitations,” Schultz said. “As the technique matures, people will better appreciate what it can and cannot do.”

	Popp mentioned several examples that show how TERS-like approaches are becoming more practical, such as in the characterization of single viruses and in protein analysis. “TERS has made a lot of progress within the last few years, especially with respect to practical life science or biomedical applications,” he said. “I am convinced that the difficulties in preparing reproducible TERS tips will be overcome soon.”

	SERS approaches offer the potential to increase the sensitivity of Raman spectroscopy in a wide range of systems. We asked our panel if SERS-based solutions have become easier for nonexperts to apply, and whether SERS is likely to become more universally applicable in the near future.

	All agreed that the lack of reproducible substrates-and having them commercially available-is the biggest obstacle to more widespread use of SERS.

	“One commercial supplier recently discontinued a SERS substrate product,” lamented Schultz. “A few other products have emerged as possibilities, but the development of a robust high-enhancement substrate would facilitate use by nonexperts,” he said.

	Siesler agreed. “Once commercial substrates are available, SERS will become more universally applicable.”

	Several panelists noted that there are many efforts underway to try to address this challenge. “Recent advances in producing colloids with reproducible size and morphology are helping to address this problem,” said Reffner.

	Popp agreed. “One of the most promising approaches in my opinion is the usage of colloidal silver or gold nanoparticles, which are easy to prepare together with microfluidic chips,” he said.

	Despite the reproducibility problem, Popp thinks that lab-on-a-chip SERS concepts are very promising, particularly for drug and metabolite monitoring. “The routine analytical application of SERS comes down to the availability of reproducible SERS substrates,” he said. “Once such SERS substrates are available, SERS-based solutions will be easy to apply-even for nonexperts-making them universally applicable.”

	Johnson is less optimistic. “I see SERS as a method that works well for very specific types of samples, but not so much as a general analytical technique,” he said.

New Areas for Raman: Applications and Challenges

	Most people consider Raman spectroscopy a mature technique, but it is still being applied to new areas-in addition to fields like clinical diagnoses and medical imaging discussed above. So we asked our panel what new applications are emerging for Raman and what challenges are involved with those applications.

	New application areas for Raman spectroscopy range from art conservation, forensics, and homeland security, to nutrition, health, and agriculture.

	Reffner said that a growing segment of Raman applications resides in field-portable Raman spectrometers, which are currently being used in homeland security and forensic applications.

	Schultz also mentioned the increased use of Raman in the forensics field. “I think Raman will continue to see increased use in applications where the samples are sensitive to chemical modification,” he said. “The art community has seen increasing use of Raman for restoration, conservation, and forgery detection.”

	Schultz also explained that advances in Raman instrumentation are making it a highly affordable method. “Mass spectrometry (MS) may still provide better absolute molecular identification, but Raman is holding its own and seems to provide complementary information where MS has trouble,” he said.

	Walls would like to see the role of Raman spectroscopy expand for applications in high growth areas like industrial biosciences, nutrition, and health. “One example is our interest in expanding the role of Raman microscopy in the analysis of agricultural plant systems to support the development of crop protection chemicals,” he said. “A key attribute needed will be the sensitivity to detect low levels of the analytes of interest in complex (and potentially fluorescent) backgrounds. Ideally, these measurements would be performed without disturbing the viability of the plant.”

	Popp believes that Raman is one of the most important spectroscopic methods. “In my view, it is not exaggerated to say that Raman spectroscopy has become an indispensable analytical method for an extremely broad area of applications,” he said.

Application Challenges and How to Overcome Them

	Even though Popp considers Raman a rather mature technique, he still believes it faces challenges. “The great challenge faced in using linear Raman spectroscopy for almost all applications is its intrinsically low scattering cross section-that is, low sensitivity very often leading to rather long acquisition times,” he said.

	Techniques like SERS, resonance Raman, and nonlinear Raman effects like CARS or SRS try to address this problem by enhancing the Raman signal. “These nonlinear Raman approaches have seen a renaissance mainly because of the recent progress made in the development of high intensive ultrashort laser sources,” said Popp. “The implementation of these nonlinear Raman phenomena in laser scanning microscopes has resulted in powerful biomedical imaging approaches that show great potential to complement established clinical pathological diagnostic tools.”

	Schutlz believes that biggest challenge for Raman lies in creating large databases of reference spectra that can be searched to identify molecules, as can be done today with gas chromatography (GC)–MS. “The challenge here is still the variances between spectra with different SERS strategies, and there is currently some debate about TERS signals,” he said. “If this can be resolved, I think Raman could compete with GC–MS characterization.”

	The challenges that Walls foresees in areas like industrial biosciences, nutrition, and health applications include fluorescence, sensitivity, and the ability to differentiate a meaningful analyte signal from a complex background response.

	Next we asked our experts what types of new automation or spectral processing could help in their work. The majority of answers addressed software improvements.

	Johnson would like to see the integration of image analysis routines into Raman instrument software that is used for mapping applications. “Particle count and size distribution as well as more sophisticated three-dimensional (3D) imaging applications would be beneficial too,” he said.

	Walls touched upon the need for libraries, similar to what Schultz cited as a main challenge earlier. “For those of us who use Raman spectroscopy for the identification of unknown species, the availability of larger, more-comprehensive electronic libraries would significantly impact the effectiveness of these efforts,” he said. Most vendors are starting to incorporate chemometrics data reduction approaches within their software, he said, and the continued expansion of these efforts will be helpful in his work.

	Finally, we asked our experts what future developments in Raman spectroscopy or its instrumentation can be expected in the coming years.

	According to Schultz, SRS is an area that should be watched closely in the next few years, because the sensitivity associated with this nonlinear technique is impressive. There are still instrumentation challenges with this technique, however. “In SRS, you have to measure the difference in the laser intensity at the Raman frequency of interest before and after the sample, which typically requires expensive lock-in amplifiers and stable laser sources,” he said. “This also often limits the spectral range and resolution.” A potential solution, he suggested, would be a lock-in array detector. “If we had lock-in arrays with 1024 channels like modern array detectors used for Raman, SRS may provide some additional advances,” he concluded.

	Popp thinks that the greatest potential for Raman lies in medical diagnostics. A key next step, he explained, is transferring Raman spectroscopy from ex vivo to in vivo applications by implementing Raman spectroscopy into endoscopic setups. “In this context, within the next few years we will see the development of various other novel Raman fiber probes for in vivo tissue screening of internal organs like the colon, stomach, or aorta,” he said. “These developments will utilize advances in fiber technology (for example, fiber Bragg gratings, waveguide optics, and imaging fiber arrays) and easy-to-operate fiber laser approaches.”

	Reffner said that the advantage of Raman spectroscopy to record low energy rotational and vibration spectra is a promising area to develop.

	The future development of capable, less expensive, and even portable instrumentation piques Walls’s interest. With continued refinement and technology advances, he said, these developments will foster growth into new applications across a wide range of application areas. “These developments, along with more powerful ‘expert user’ driven software interfaces, will catalyze the growth of Raman technology into the hands of nonspecialists in spectroscopy in an increasingly diverse range of technical applications,” he predicted.

	Raman spectroscopy is an invaluable technique for a wide array of application areas. It’s safe to say that this technique has a strong foothold on the future, no matter what new application areas come its way.

	I would like to extend a special thank you to Fran Adar of Horiba and Dennis J. Walls of Dupont for their assistance with the questions and panelist recommendations.

http://en.wikipedia.org/wiki/Raman_spectroscopy

	(2) J. Cooper, M.F. Abdelkader, and K. Wise, US patent 8,570,507 B1, 29 October 2013.

In honor of Spectroscopy's celebration of 30 years covering the latest developments in materials analysis, we asked a panel of experts to assess the current state of the art of Raman spectroscopy and to try to predict how the technology will develop in the future.

Analysis of the State of the Art: Raman Spectroscopy

's celebration of 30 years covering the latest developments in materials analysis, we asked a panel of experts to assess the current state of the art of laser-induced breakdown spectroscopy (LIBS), and to try to predict how technology will develop in the future. 

	Laser-induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy that uses a highly energetic laser pulse as the excitation source (1). Although the spectral analysis of laser-produced spark emission dates back to the invention of the pulsed laser in 1960, the pursuit of this phenomenon for analytical chemistry applications and the coining of the term "LIBS" did not happen until the early 1980s (2). We asked a panel of experts to share their views about the current state of LIBS, including recent and expected future developments, ongoing challenges, and the applications where it can be used. This article is part of a special group of six articles covering the state of the art of key techniques, also including inductively coupled plasma–mass spectrometry (ICP-MS), X-ray fluorescence (XRF) spectroscopy, infrared (IR) spectroscopy, near-infrared (NIR) spectroscopy, and Raman spectroscopy.

	We started by asking our panelists what they considered the most important advance in LIBS or its instrumentation in the last 5–10 years. Vassilia Zorba, a staff scientist at Lawrence Berkeley National Laboratory, said it's hard to pin down only one important advance in LIBS during the past decade. "Significant progress has been made in instrument components, data processing algorithms, and extending its capabilities to isotopic analysis," she said.

	Other panelists agreed that quite a few developments had come together in recent years. "The combination of the improvement of LIBS hardware, including the three major components of LIBS setup, the deeper understanding to the mechanism of laser-induced plasma and its emission, as well as the development of quantitative modeling, are the most important advancements," said Zhe Wang, an associate professor at Tsinghua University

	"Commercially available LIBS instruments for many market applications are now available as a result of a perfect storm," said Rick Russo, a senior scientist at Lawrence Berkeley National Laboratory and president and CEO of Applied Spectra. "This storm includes advances in fundamental science, lasers, detectors, data analysis algorithms, and the success of ChemCam."

	ChemCam, the LIBS instrument currently exploring Mars on the Curiosity rover, was top of mind for several other panelists, as well. "Integrating a LIBS system into the Mars Rover would have to rank on the list of milestones in this field," said Ishan Barman, an assistant professor in the Departments of Mechanical Engineering and Oncology at Johns Hopkins University.

	Vincent Motto-Ros, an associate professor at the Light and Matter Institute at Lyon University, said ChemCam exemplifies the advances that have been made in LIBS instrumentation, particularly to develop systems adapted for specific applications. "A lot of effort has been made in the last few years in the development of compact (handheld) designs, LIBS platforms for laboratory analysis, and LIBS systems dedicated to operate in harsh conditions," said Motto-Ros.

	Barman was also impressed by the development of handheld devices. "A major advance, which has happened gradually, has been the translation of a large, unwieldy laboratory bench setup into a portable, briefcase-sized device that can be deployed in a variety of field applications," said Barman.

	Several panelists remarked on the importance of data analysis and computerized chemometric techniques for rapid sample identification. "The integration of that chemometric software with the analytic hardware has pushed the technique to true real-time analysis," said Steven J. Rehse, an associate professor in the Department of Physics at the University of Windsor."We can now objectively and rapidly identify, sort, classify, or discriminate a wide variety of targets ranging from hazardous materials to gemstones, geological samples, alloys, and pathogens on the basis of a LIBS spectrum that is acquired in under 1 second."

Zorba agreed. "Chemometric analysis has gone from limited to routine use in LIBS in the last decade, and will continue to be a significant step toward data interpretation and classification," she said. "Recent developments in calibration-free LIBS have also been an encouraging step toward eliminating the need for calibration standards."
	Other panelists said that the most important advances were in lasers. Zorba explained that femtosecond lasers have been increasingly used in LIBS during the past 10 years, thanks to the development of more stable and user-friendly systems.
	
	
	Matthieu Baudelet, a research assistant professor at the University of Central Florida, said that the compactness of the new diode pumped sources allow for high repetition rate analysis (100+ Hz) for both laboratory instrumentation and handheld systems with the very compact low energy kilohertz systems. "Fiber lasers are showing a great stability and ruggedness that allows for robust implementation in harsh environments, such as conveyor belts in mining and sorting facilities," he said.
	
	
	Zorba added that the development of laser ablation molecular isotopic spectrometry (LAMIS) stands out as a significant new   technology for extending LIBS from a largely elemental analysis tool to a real-time isotopic one.

	Next, we asked our panelists about some of the key challenges or questions that spectroscopists developing or using LIBS currently face, in terms of current limitations of LIBS, limits to the understanding of how it really works, or difficulties using it (such as for specific types of application). We also asked which of those challenges are likely to be addressed in the coming years and how progress might be made.

	Motto-Ros said that LIBS is subject to comparison with other analytical techniques such as X-ray fluorescence (XRF) or inductively coupled plasma (ICP)-based technologies and that such comparisons tend to slow down adoption. "An observation that I find very disturbing is that despite more than 50 years of existence, it is still rare to find a LIBS instrument used for routine analyses in analytical laboratories," he said. "We have to change that."

	Richard R. Hark, the H. George Foster professor in the Department of Chemistry at Juniata College and Chief Scientist at Synergos Global Security, LLC, cited the need to improve our understanding of the factors that affect the physics of ablation and the chemistry that occurs in the plasma that is subsequently formed. "Such an understanding will enhance the utility of the LIBS method for qualitative and quantitative analysis," he said.

	Rehse agreed. "As a physicist, the inability to predict and calculate from first principles what the plasma emission spectrum will be from an arbitrary analyte atom in an arbitrary medium (commonly called the 

) remains a problem," he said. Motto-Ros echoed the point. "Efforts must continue on fundamental investigations of the laser-induced plasma," he said.

	Zorba agreed, noting that several aspects of the laser-material interaction remain unknown. "Particularly in the femtosecond-time regime, nonlinear processes (such as multiphoton absorption) and the distinction between thermal and nonthermal processes hamper an a priori prediction of optical and thermal diffusion lengths," she said. "These parameters are critical toward defining laser sampling parameters (ablated material mass), plasma conditions, and resulting LIBS emission."

	A closely related problem is the so-called "matrix effect"-the fact that the signal from a specific analyte atom can depend on the sample matrix. "Spectroscopists who use LIBS know that parameter optimization for specific analytes in a particular matrix is both challenging and essential," added Hark.

	"The matrix effect makes the preparation of high-quality standards important," said Rehse. "It also makes it more difficult to sample highly heterogeneous samples like complex minerals or complicated powders like dirt or soil."

	Wang noted that for practical quantitative analysis, the most important issue is to provide consistent analytical results. "Because of uncertain laser-sample interaction, unstable plasma and surrounding gas interaction, the inhomogeneous spatial distribution, and uncontrolled temporal revolution, it is very difficult for LIBS to provide such a stable spectral signal even using multi-pulse analysis and averaging a large number of spectra to remove the random noise," he said. "Reducing the variation between groups from the same sample is the overwhelming important issue that must be solved for LIBS to realize quantitative analysis and large-scale commercialization."

	Hark also noted that reproducibility between instruments is another potential challenge. "Unlike other analytical techniques like Fourier transform infrared (FT-IR) or UV–visible spectroscopy, LIBS spectra obtained on different instruments using the same experimental parameters are not necessarily identical," said Hark. "Further work has to be done to make LIBS spectra interchangeable."

	Rehse cited another aspect of variability in LIBS measurements. "The pulse-to-pulse variation in plasma properties caused by laser shot repeatability issues is another challenge," he said.

	Russo feels the concerns about matrix effects and lack of reproducibility are overblown. "Like all analytical methodologies, LIBS requires standards for quantitative analysis," he said, adding that so-called "standardless" LIBS calibration methods eventually will be developed to meet specific applications. "And similar to any atomic spectroscopic approach, knowledge of spectral interferences and matrix effects is important for getting the best performance."

	He acknowledged that getting good analytical performance requires knowledge of the plasma temporal and spatial properties, as well as of the sample, and that a set of parameters has to be established for a particular sample material to give optimum performance. "Once the optimum method is established, precision and accuracy are repeatable and reliable," he said.

In honor of Spectroscopy's celebration of 30 years covering the latest developments in materials analysis, we asked a panel of experts to assess the current state of the art of laser-induced breakdown spectroscopy (LIBS), and to try to predict how technology will develop in the future.

Megan L’Heureux

Articles

The 2017 Emerging Leader in Atomic Spectroscopy Award

The 2016 Emerging Leader in Molecular Spectroscopy Award

Analysis of the State of the Art: Raman Spectroscopy

Analysis of the State of the Art: LIBS