Symposium: Chemistry at the Nanometer Scale edited by
Symposium: Chemistry at the Nanometer Scale
K. W. Hipps
Physical Chemistry at the Nanometer Scale
Washington State University Pullman, WA 99163
K. W. Hipps Department of Chemistry, Washington State University, Pullman, WA 99163-4630;
[email protected] The summer of 2003 saw the inception of a new educational activity sponsored by the Petroleum Research Fund of the American Chemical Society—the PRF Summer Schools. The articles that follow represent a portion of the material covered at the school on “Physical Chemistry at the Nanometer Scale” (PC@nm) at Washington Sate University (WSU) in August of 2003. Nanotechnology was born with a brilliant lecture by Richard Feynman, “There Is Plenty of Room at the Bottom” (1). Nanotechnology is concerned with materials and systems Symposium: Chemistry at the Nanometer Scale Getting Physical with Your Chemistry: Mechanically Investigating Local Structure and Properties of Surfaces with the Atomic Force Microscope William F. Heinz and Jan H. Hoh
695
Electron Tunneling, a Quantum Probe for the Quantum World of Nanotechnology K. W. Hipps and L. Scudiero
704
Electrochemistry at Nanometer-Scaled Electrodes John J. Watkins, Bo Zhang, Henry S. White
712
Electrochemical Fabrication of Metallic Quantum Wires Nongjian Tao
720
Single-Molecule Electronic Measurements with Metal Electrodes Stuart Lindsay
727
Nanotribology: Rubbing on a Small Scale J. Thomas Dickinson
734
Other Articles on Nanotechnology in This Issue Communicating Science to the Public through a University–Museum Partnership Amy C. Payne, Wendy A. deProphetis, Arthur B. Ellis, Thomas G. Derenne, Greta M. Zenner, Wendy C. Crone
743
Chemistry, Creativity, Collaboration, and C60: An Interview with Harold W. Kroto Liberato Cardellini
751
Template Synthesis and Magnetic Manipulation of Nickel Nanowires Anne K. Bentley, Mohammed Farhoud, Arthur B. Ellis, George C. Lisensky, Anne-Marie L. Nickel, Wendy C. Crone
765
Nanopatterning with Lithography Christy L. Haynes, Adam D. McFarland, Richard P. Van Duyne, Hilary A. Godwin
768A
Preparation of Dppe-Stabilized Gold Nanoparticles Keenan E. Dungey, David P. Muller, Tammy Gunter
769
Supercritical Fluid Facilitated Growth of Copper and Aluminum Oxide Nanoparticles Geoffrey L. Williams, Jason K. Vohs, Jonathan J. Brege, Bradley D. Fahlman
771
Growth Kinetics and Modeling of ZnO Nanoparticles 775 Penny S. Hale, Leone M. Maddox, Joe G. Shapter, Nico H. Voelcker, Michael J. Ford, Eric R. Waclawik 779 Surface pKa of Self-Assembled Monolayers Penny S. Hale, Leone M. Maddox, Joe G. Shapter, J. Justin Gooding
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whose structures and components exhibit novel and significantly improved physical, chemical, and biological properties, phenomena, and processes because of their nanometer size. Articles on nanotechnology can be found in this Journal (2–5). A Chemical and Engineering News article proclaimed, “Nanotechnology is the next big thing. In fact […it] is nothing short of the next industrial revolution” (6). If even a fraction of these expectations are to be realized, a huge new technical work force will be needed. This workforce must be trained in the principles that govern material and devices composed of small collections of atoms or molecules. Even more critical is the development of the fundamental science that forms the foundation upon which the technology may be built. PC@nm focussed on the basic physical chemistry that must provide the essential foundation from which nanotechnology may arise. In that context, PC@nm was a school on nanoscience, not nanotechnology. Future undergraduate curricula will include more on nanoscience. Nanoscience will find its way into the chemistry classroom as specific courses focussing on such issues as self-assembly and nanoscale properties, and as motivational examples of fundamental principles such as molecular orbital theory, electronic conduction, single atom and molecule reactivity, and friction on the molecular scale. The articles presented here will help instructors generate these courses and lectures and will help motivate students to learn the discipline. A goal of PC@nm was to help generate the teachers and researchers who will provide the critical needs of manpower development for, and fundamental research on, processes at the nanometer scale. In particular, we focussed on the interface between physics, chemistry, materials science, and biophysics. Outstanding scientists from all of these disciplines presented both the fundamentals and the exciting frontiers of their specialties. Another goal was to communicate both the basic scientific principles and the excitement associated with nanoscale science. This was a school on the fundamental behaviors that are unique to the nanoscale and on the techniques and instrumentation required to measure and to influence them. Our audience was, in part, scientists who had not yet chosen, or were in the process of changing, research focus area. We welcomed those who teach undergraduate chemistry in order to influence the topics covered. The students represented a mix of graduate students, postdoctoral candidates, faculty from non-Ph.D.-granting institutions, and faculty from Ph.D.-granting institutions. The school was an intense experience, typically requiring attendance of nine hours of lecture per day, for seven days. On the eighth day small group instrument demonstrations were arranged. Compared to other forms of educational activities (classes, seminars, professional meetings, etc.), the students ranked the effectiveness of this summer school as higher than other activities except semester-long classes. Thus, the density of learning was high. Virtually every participant rated the summer
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Symposium: Chemistry at the Nanometer Scale
school concept as an excellent venue that PRF should continue to support. In order to expand the impact of PC@nm, many of the lecturers have prepared articles covering essential features of their presentations at the school. Just as the summer school inspired students to create lectures, courses, and textbook material based on nanoscience, we hope these articles will do the same for the wider chemistry community. Because each 4000 word article is material selected from six to eight hours of lecture, there is much that is necessarily omitted. We have worked hard to fill some of this void with pertinent references to the literature. In other cases, entire topics have been omitted (such as near-field optical microscopy). Despite these omissions, we believe that this group of articles will be an invaluable aid to students and educators seeking an introduction to the exciting and growing field of nanometer-scale science. Many of these articles both introduce new techniques and identify fundamental properties essential for understanding nanometer-scale phenomena. The article by Heinz and Hoh (pp 695–703) introduces the atomic force microscope (AFM), a powerful and versatile tool for probing the chemistry, material properties, and dynamics of interfaces at the nanometer scale in virtually any environment. The reader is introduced to all the key elements of the AFM and to the concepts determining image attributes. Data acquisition, image interpretation, and force measurement are all discussed. This article will serve as an excellent introduction to the field of AFM for the starting graduate student or for the undergraduate instructor wishing to include nanometer-scale microscopy in physical, analytical, or biochemistry courses. Because the scanning tunneling microscope (STM) has been previously introduced in this Journal, the article by Hipps and Scudiero (pp 704–711) concentrates on the essentials of the tunneling process and its application to spectroscopy with single-molecule spatial resolution. Inelastic and elastic tunneling spectroscopy are introduced, and orbital mediated tunneling spectroscopy (OMTS) is given special emphasis. Connections are made between the nanoscale method of OMTS and the microscale methods of ultraviolet photoelectron spectra and electrochemistry. The residence time of the electron during the OMTS process is discussed in some detail. An understanding of the concepts behind the spectroscopy will require the quantum mechanical skills introduced in undergraduate physical chemistry. For upper-level undergraduate and graduate students, the concepts and most of the references cited should be accessible. The pictures of molecules and the electronic pathways through molecules have proven very motivational for freshman students at WSU. White and coauthors (pp 712–719) introduce the exciting world of electrochemistry on the nanometer scale. They clearly enunciate the benefits and difficulties associated in making measurements on this scale. Moreover, this article contains a clear and concise introduction to the nuts and bolts of making and using nanometer-scale electrochemical electrodes. Besides the obvious benefits of updating instructors and graduate students on a frontier area in electrochemistry, the information contained in this article can be easily integrated into upper-level and graduate-level electrochemistry courses. Other articles in this series focus on nanometer-scale structures and their properties. Tao (pp 720–726) introduces metallic quantum wires. He provides a wonderful introduction to the essential physics of electron transport through 694
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metal wires only a few atoms in diameter. This material should be presented in modern solid-state chemistry courses. Tao also describes how to fabricate metal nanowires using electrochemical methods and discusses important future applications. This is qualitative enough to be appropriately added as enrichment material to a freshman class and should be an essential part of any upper-level nanotechnology lectures. Lindsay (pp 727–733) introduces single-molecule electrical conduction. The process of transferring electrons from one metal electrode to another via an intervening molecule differs from electrochemically or optically induced electron transfer in important ways. Lindsay discusses the key difficulty in these measurements—making contacts to a molecule—and introduces methods that allow reliable and reproducible contacts to be made. The issue of the residence time of an electron on the molecule, which was discussed by Hipps in the context of OMTS, is again important to our understanding of how a single-molecule wire behaves. While electrical conductivity is presently more the domain of the physicist and engineer (and therefore will spark their interest when presented in the chemistry classroom), the growing need for single molecules with particular electronic-transport properties makes this a subject that is rapidly becoming one centered squarely in the chemists’ domain. Changing the viewpoint from nanoscale electronic processes to nanoscale mechanical ones, Dickinson (pp 734–742) introduces nanotribology. Nanotribology is the study of friction, wear, and lubrication between a single asperity of nanometer dimensions and a solid surface. This is an area of extreme importance for any future nanotech devices in which one component moves against another. If we are to realize one of Feynman’s nano-robots that travel through the body making repairs, we will first have to solve a number of nanotribology problems. As nanotechnology grows in importance, classical topics currently presented in undergraduate physical chemistry such as viscosity and diffusion will be replaced or augmented with their nanometer-scale equivalent— nanotribology. Dickinson’s article provides a concise and citation rich introduction to this important area. Acknowledgments I gratefully thank the American Chemical Society Petroleum Research Corporation for providing support to the summer school where this work was presented. I also thank the National Science Foundation for their support of equipment used in the summer school and for supporting my research that made my offering this school possible. Literature Cited 1. Given on December 29, 1959 at the annual meeting of the American Physical Society. A transcript may be found at http:// www.zyvex.com/nanotech/feynman.html (accessed Jan 2005). 2. Heinhorst, S.; Cannon, G. J. Chem. Educ. 1999, 76, 1472. 3. Smestad, G. P.; Grätzel, M. J. Chem. Educ. 1998, 75, 752. 4. Chanteau, S. H.; Ruths, T.; Tour, J. M. J. Chem. Educ. 2003, 80, 395. 5. Campbell, D. J.; Olson, Joel A.; Calderon, Camilo E.; Doolan, P. W.; Mengelt, E. A.; Ellis, A. B.; Lisensky, G. C. J. Chem. Educ. 1999, 76, 1205. 6. Chem. Eng. News 2004, 82 (15), 17–22. Chem. Eng. News 2000, 78 (18), 41–47.
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