Editorial Cite This: Chem. Rev. 2019, 119, 1−2
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Introduction: Chemical Sensors he chemical sensing field appears to be in an endless expansion. New methods empowered by new physics, biochemistry, materials, chemistry, or hardware abound and there is constant improvement of established methods along with new potentially disruptive technologies. The promise has always been to move away from expensive complex instrumentation to small inexpensive systems that can be operated by anyone. Classic successes are the glucose meter and home pregnancy tests, which have touched many in society. Many more high-impact applications await adoption by business, government, and individuals. It is common to see media coverage of the latest electrical device developed by electrical engineers to deliver complex chemical data from the environment. However, what the reporters tend to overlook is that the most important element of the devices is the sensor, which is primarily responsible for the quality of the information being created. Indeed, the sensor developers are often the unsung heroes. A sensory device must have a number of critical functions that must work in concert. Sampling is often overlooked, but you cannot accurately detect an analyte if it is not delivered to the transducer in a functional form. In this context fouling of a sensor by other macromolecular or reactive species can be an issue, and one advantage of chemical sensing is that the sensor interface can often be frequently refreshed or replaced. The fidelity of the transduction is often a limitation, and virtually all chemical sensors have some cross reactivity. However, unique patterns of cross-reactivity created by a diverse array of differential sensors can be used in an e-nose or e-tongue scheme to advantage. Signal gain mechanisms provided by clever measurement and chemistry are an intrinsic advantage. The stronger the signal created, the higher the sensitivity and the less likely that spurious noise would corrupt the signal. Long-term sensor stability is something that most academics are guilty of not properly evaluating. These tests take time and are often at odds with progression of our co-workers through our laboratories to new positions. The reader will find all of these issues, as well as others, addressed by the group of distinguished authors in this issue of Chemical Reviews. There are a number of new and emerging trends in chemical and biological sensor development that permeate all who work in it. It is now a cliché to mention that nanoscience is changing a field. We would argue that in the sensor field, wherein the analyte transduction interface need only be nanosize, the dramatic developments of the last decades have had profound impact. Sensor developers have access to nanomaterials created from the bottom up or top down, and materials can be assembled or analyzed by nanofabricaton and powerful imaging methods with subnanometer resolution. New generations of established sensors, such as metal oxides, are being pushed to new limits by employing nanostructured materials. One of the promises of chemical sensors is that they can be widely deployed to provide comprehensive spatial and temporal analysis of a particular problem. Such a situation
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has obvious benefit in the early detection of an infectious disease. However, diverse data accessible with chemical/ biological sensors will have implications that are hard to predict. It was not so long ago that if you said the term “big data” people would not be sure exactly what you were talking about. This era has been brought upon us by the remarkable proliferation of interconnected mobile computational devices that few of us now go anywhere without. Leveraging the big data platform to provide other societal benefits is highly dependent on the quality of the signals that are going into the system. Broadly deployed chemical and biological sensors have the potential to create future systems that can identify health risks, optimize agricultural production, and manage supply chains. We expect there are many other opportunities that await discovery. In this special issue we have strived to give broad coverage to the field of chemical sensing. Biological sensing is also covered, but it is challenging to be as comprehensive in this area. In particular, definitions of sensing can be somewhat fielddependent. Biochemists often refer to molecular probes as sensors. These chemisensors can often be instrumented and used to create a sensor device that can be characterized in terms of levels of detection, response kinetics, and reversibility. For our part, we see these molecular/biomolecular innovations as important signal transducers that can empower new generations of sensors. The diversity of interest in the chemical sensor is reflected in this special issue, with electrical methods including field effect transistors (Katz and co-workers), impedance measurements (Francis and co-workers), and electrochemical biosensors and lab on a chip schemes (Baeumner and co-workers). Sensors utilizing direct resistivity measurements can be constructed from an increasing variety of materials, and contributions cover molecularly imprinted polymers (BelBruno and co-workers), two-dimensional nanomaterials (Mirica and co-workers), conducting materials leveraging the selectivity of natural receptors (Park and co-workers), and carbon nanotubes (Swager and co-workers). Optical methods can make use of changes in color to create cross-reactive arrays that mimic olfaction (Suslick and coworkers), as well as luminescence using supramolecular complexes (Levine and co-workers). Spectroscopic methods have the advantage of providing fingerprints for different species, and transduction can be enhanced by coupling to nanoparticles in plasmonic processes (Haynes and co-workers) or by molecular interactions in NMR methods (Zhao and coworkers). With focus on achieving ultrasensitivity and multiplexing in complex biological samples, Walt and coworkers review established and emerging methods for the detection of proteins. Alas, this special issue is really just a sampling of the exciting innovations that are progressing worldwide in chemical and Special Issue: Chemical Sensors Published: January 9, 2019 1
DOI: 10.1021/acs.chemrev.8b00764 Chem. Rev. 2019, 119, 1−2
Chemical Reviews
Editorial
biological sensors. We hope that the readers, and in particular newcomers to this field, will see the abundant opportunities in the articles in this issue and further strive to make new connections that will drive sensor innovations.
George M. Whitesides. During 2011−2015, she pursued an NIH postdoctoral fellowship in the laboratory of Prof. Timothy M. Swager at the Massachusetts Institute of Technology. Katherine began her independent scientific career as an Assistant Professor of Chemistry at Dartmouth College in July of 2015. Her current research interests revolve around multifunctional materials, electroanalysis, adhesion science, and self-assembly.
Timothy M. Swager,* John D. MacArthur Professor of Chemistry Massachusetts Institute of Technology
Katherine A. Mirica, Assistant Professor Dartmouth College
AUTHOR INFORMATION ORCID
Timothy M. Swager: 0000-0002-3577-0510 Katherine A. Mirica: 0000-0002-1779-7568 Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS. Biographies
A native of Montana, Timothy M. Swager received a B.S. from Montana State University in 1983 and a Ph.D. from the California Institute of Technology in 1988. After a postdoctoral appointment at MIT he was on the chemistry faculty at the University of Pennsylvania 1990−1996 and returned to MIT in 1996 as a Professor of Chemistry and served as the Head of Chemistry from 2005−2010. Swager’s research interests are in design, synthesis, and study of organic-based electronic, sensory, high-strength, liquid crystalline, and colloid materials.
Katherine A. Mirica was born and raised in Ukraine. She received her B.S. in Chemistry in 2004 from Boston College, working in the laboratory of Prof. Lawrence T. Scott. In 2011, she earned her Ph.D. in Chemistry from Harvard University under the guidance of Prof. 2
DOI: 10.1021/acs.chemrev.8b00764 Chem. Rev. 2019, 119, 1−2
