Editorial pubs.acs.org/cm
Celebrating Twenty-Five Years of Chemistry of Materials
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improvements in synthesis methods and analytical and theoretical methodology. Currently, the level of scientific sophistication and depth of understanding that characterizes research in materials chemistry is fully equal to that in any area of science, which perhaps would not have been considered the case 25 years ago. In any area of research, there are always a few topics that seem to attract particular attention. These “hot” topics have changed over our 25 years of publication and will continue to change as this field evolves. Currently receiving particular attention are nanomaterial synthesis and application, including carbon nanomaterials (nanotubes and graphene), organic electronic and optoelectronic materials, mesoporous inorganic and organic materials, catalytic and photocatalytic systems, biomedical materials, materials for batteries, electrolytic capacitors and fuel cells, and thermoelectric and multiferroic materials. The papers in this Special Issue are organized according to subject area using headings that reflect their main focus, recognizing that alternatives are possible. Within each group the order of papers is largely arbitrary although an effort was made to provide a logical progression of subtopics. Research in nanomaterials, the first groups of papers here, has been on a steady growth trajectory for about 30 years and shows no sign of slowing down. It has produced many fascinating results and covers an exceptionally wide range of materials that include elements from all over the periodic table. Applications range from energy, electronics, and manufacturing to the environment and medicine, with the last just beginning to emerge. In the section Nanoparticle Synthesis, Growth and Applications, we start with the mechanism for the growth of nanocrystals from precursor solutions and progress to the role of redox chemistry, ligands, and capping agents in determining their size, shape, and properties. Quantum size effects play an increasing role in determining the optical, magnetic, and electronic properties of nanoparticles as their size decreases, with nanoparticles in the 1−3 nm size range constituting a special class in themselves. In addition to catalysis, where the high surface area of solid catalysts in the 100 to 1 nm size range can result in enormous enhancements in reaction rates, the optical, magnetic, and electronic properties also undergo dramatic changes. In general, nanoparticles synthesized from solution are stabilized against agglomeration and sintering by ligands, which can range from small ions and molecules to polymeric groups that form a “canopy” of much larger size than the inorganic “core”. These ligands, or capping groups, play an important role in determining the resultant nanoparticle physical and chemical properties, as well as their shape and size. They have been used to facilitate incorporation of the nanoparticles into, and even covalent interaction with, polymers for use in cross-linking or mechanical reinforcement of thermoplastics. On the other hand,
his Special Issue celebrates 25 years of publication for Chemistry of Materials. It contains 66 invited peer-reviewed Perspectivesa and Reviews from an international group of authors who are experts in their fields. This Issue provides an exceptionally wide spectrum of topics that cover a range of materials types and applications, representative of the scope of materials chemistry research in the 21st century. Materials science is a relatively new discipline in academia, beginning to appear only about 40 years ago. Of course, there was work in materials development but the academic discipline itself did not exist. Many universities had metallurgy and ceramics groups or departments, and in the early 1970s they gradually morphed into integrated Materials Science and Engineering Departments. The Materials Research Society was founded in 1973 and helped to connect a broad range of disciplines. When Chemistry of Materials was introduced by the ACS 25 years ago, most chemistry research in academia had been oriented toward fundamental understanding, and little was directed toward useful materials. With a few important exceptions, polymer science was uncommonly practiced in chemistry departments. Organic chemistry was primarily aimed at reaction mechanisms and pharmaceutical chemistry, and organometallic chemistry was largely devoted to homogeneous catalysis and biochemistry. Inorganic chemists did study new materials, especially crystalline ones with interesting structures or electrical, magnetic and optical properties. At the same time, there was a lot of materials chemistry activity in industry, particularly in the area of semiconductor processing. Some chemistry development actually had a home in materials science and electrical engineering groups advancing the semiconductor industry, especially in surface science and thin film processing. There was also a great deal of work in crystal growth of materials for optical and semiconductor applications. As the importance of new materials development became apparent, things changed rapidly. Academic chemical engineering, once concentrated on large scale industrial processing, changed focus dramatically toward new materials, and chemistry departments brought in young researchers focused on generating materials of many types. A whole new area developed in a relatively short time, and it is growing at a high rate all over the world. In the brief period that materials chemistry has been recognized as a distinct area of research and development, many new materials have entered the market, along with dramatic improvements in materials processingSi-based integrated circuit manufacture, lithium batteries, fuel cells, photovoltaicswhich have revolutionized such fields as data processing and storage, and energy storage and conversion. Research on photoresists, culminating in the development of amplified photoresists in the 1980s, enabled remarkable progress in microelectronics where device dimensions are now about onetenth the wavelength of the laser source used to define them. Along with this technological development has come a greater sophistication in materials characterization, fundamental understanding, and directed material synthesis, fueled by major © 2014 American Chemical Society
Special Issue: Celebrating Twenty-Five Years of Chemistry of Materials Published: January 14, 2014 3
dx.doi.org/10.1021/cm4037988 | Chem. Mater. 2014, 26, 3−4
Chemistry of Materials
Editorial
development, OLEDs are now in use for both lighting and very high resolution TV sets. The papers listed under Organic Materials in Electronics and Photonics cover a large range of topics in this area, which reflect well the high level of activity in research and development laboratories worldwide. These topics include: self-assembly of organic functional materials for liquid crystals, organic ferroelectrics, and molecular machines; photopolymers; nonlinear optical materials; charge generation and transport in π-conjugated polymers; organic solar cells; and organic bioelectronics. The next section, entitled Surfaces, Interfaces and Coatings, deals broadly with surfaces and their role in materials science. Starting with liquids as surface materials, these papers progress to reactions on soft and hard surfaces that result in covalently attached organic groups and polymers or inorganic films which fundamentally change the properties of the substrate material and lead to unique polymer structures in heterogeneous catalytic reactions. Last, but far from least, in this Issue are Inorganic Materials, the oldest area of materials chemistry. New materials and insights continue to appear at a great rate, and there seems to be an infinite series of connections to new technologies. The papers here discuss principal concepts in the design and engineering of transition metal oxides, semiconductor alloys, metal chalcogenides, and nanocomposites with improved ferroelectric, thermoelectric, and nonlinear optical properties. Like the other papers in this Issue, the authors of these Reviews and Perspectives are among the world’s experts in their fields and have done much to advance materials chemistry over the past 25 years. We think it well justified to say that materials chemistry is one of the most important areas for the health and prosperity of Earth’s people and is also of major importance in the critical effort to reduce the threat of global warming that has been emphasized by the recently issued 2013 UN report (available at www.ipcc.ch). The future offers many opportunities for important and rewarding work. Here’s looking forward to the next quarter century.
for other applications, such as catalysis, they may need to be removed or replaced by more labile groups. For applications in electronics and optoelectronics, close packed assemblies or films of nanoparticles are typically needed. The final papers in this section deal with the formation, modification, properties, and application of such assemblies. Research on Nanostructured Carbon Materials, covered in the next group of papers, has received particular attention in recent years, including a Nobel Prize. In addition to fullerenes, carbon quantum dots, nanotubes, and graphene, mesoporous carbon structures with pores in the nanometer size range have found application in many areas of technology. These include absorbents, acoustic and thermal insulators, porous support materials for heterogeneous catalysis, and Li battery electrodes. The papers in this section describe methods for the fabrication of graphene-based electronics and discuss charge and mass transport through carbon nanotubes and graphene; the interaction of metal atoms and clusters with graphene and carbon nanotubes; and the control of porosity and nanoarchitecture in mesoporous carbon materials. Along with the mesoporous carbons, nanoporous materials span the entire range of material types from inorganic to organic and constitute a substantial fraction of the papers published in Chemistry of Materials over the past 25 years. The initial papers in the section, Nanoporous Materials, describe methods for nanomaterials synthesis with particular relevance to nanoporous materials. Later papers focus on zeolites and other mesoporous inorganic solids with controlled porosity, as well as porous metal−organic framework solids and polymers. Applications include adsorbents, membranes, chromatographic separation media, photovoltaic cells, Li-batteries, catalyst supports, and functional photonics. Energy, in all its ramifications, continues to be widely addressed and is the theme of the ACS Spring 2014 National Meeting, as well as our next group of papers on Energy Storage and Conversion. The increasing realization of the need for renewable sources has driven large investments, and the field is evolving rapidly. Research on solar energy conversion to electricity and liquid fuels from CO2 is ubiquitous. Solar cells are seen everywhere, appearing as large arrays as well as at individual homes. Cost reduction has been a focal point of work in organic solar cells that can be made with roll-to-roll production, but they still have a long way to go for large-scale applications. Ionic conduction in inorganic and polymer membranes is of critical importance in fuel cells and batteries, as well as in chemical sensors and resistive switches. After an analysis of ion transport in extremely small systems, this section focuses on polymer electrolytes for fuel cells, electrodes for Li batteries, and solar hydrogen production from water. The section on Materials Chemistry in Medicine and Biology includes papers related to drug delivery, biomimetic chemistry involving synthetic polypeptides, and the materials science of pathological crystal formation in vivo. This is one of the most rapidly growing areas of materials chemistry and has great potential for application in medicine and human health. Indeed, a number of papers in other sections relate to this subject and could have been placed here rather than their current locations. The view that organic materials were not useful in active devices was a mantra of the electronics industry for a long time, but that is changing. Organic electronics has received much research support. At this writing, the most exciting applications lie in flexible devices, including sensors aimed at medical use and efficient organic light emitting devices (OLEDs). After rapid
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Leonard V. Interrante, Editor-in-Chief of Chemistry of Materials (1989−2013) Edwin A. Chandross, Editor of Chemistry of Materials (2008−2013)
ASSOCIATED CONTENT
S Supporting Information *
The full details of the cover caption. This information is available free of charge via the Internet at http://pubs.acs.org/.
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AUTHOR INFORMATION
Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS.
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ADDITIONAL NOTE Perspectives are a new type of review paper for Chemistry of Materials, being introduced for the first time in 2014 (CM Scope and Editorial Policy document; http://pubs.acs.org/page/ cmatex/submission/reviewers.html). Unlike the CM short Reviews, Perspectives include a brief biographical sketch for the principal author(s). a
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