Short [N,N] Carbon Nanotubes of Uniform Diameter by Chemical Synthesis and Tests of Methods for Their Elongation

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The long term objective of this project is the development of methods to access useful quantities of uniform diameter, single-walled carbon nanotubes, all having identical sidewall structures, by chemical synthesis. Carbon nanotubes (CNTs) having [n,m] indices with n = m, the so called armchair CNTs, have been chosen as the initial objectives, because they will all be electrically conductive (metallic) and can therefore serve as nanowires in molecular scale devices. The overall strategy begins with bottom-up chemical syntheses of short, hemispherical hydrocarbon nanotubes and culminates with their elongation to full length CNTs; the diameter and rim structure encoded in the short hydrocarbon templates will dictate the diameter and sidewall structure (the [n,m] index) of the resulting nanotubes. The Chemical Synthesis Program of the National Science Foundation supports Professor Lawrence Scott of Boston College to synthesize [5,5], [6,6], and [10,10] CNTs and, in collaboration with Professor Robert C. Haddon of the University of California at Riverside, to test methods for the elongation of such templates. The enormous amplification in size resulting from such growth processes is anticipated to make useful amounts of uniform diameter armchair CNTs available from even milligram quantities of the small hydrocarbon templates. The discovery of carbon nanotubes in 1991 almost instantly inspired dreams among scientists and engineers about how these light weight, super strong, heat resistant, ultra thin nanowires could revolutionize the miniaturization of electronic devices far beyond what can currently be achieved by lithography on silicon chips. Unfortunately, not all carbon nanotubes (CNTs) are alike. Some are semiconductors, whereas others are highly conductive, like metals, with current carrying capacities up to 1000 times greater than that of copper wire. Despite two decades of extensive experimentation worldwide, however, all known preparation methods still yield mixtures of different types of CNTs that are virtually impossible to separate into their individual components in useful amounts. More controlled methods for synthesizing CNTs of predefined dimensions and chemical structure are clearly needed, and this project is focused on the development of such methods. This interdisciplinary project provides research training to graduate and undergraduate students (including women) and a postdoctoral researcher. In addition, several Ph.D. students who have won fellowships from their home countries have recently come to the laboratory of Professor Scott from Switzerland, Japan, Taiwan, and Australia to collaborate on this project for periods of three to twelve months each. The interactive and diverse research environment of this project provides an excellent setting for training and learning and for the development of a stronger, scientifically and culturally literate workforce. The broader impacts also involve disseminating research results through publications and presentations at national and international conferences.