SWNT Amplification: A Route to Specific Structure Nanomanufacturing

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The objective of this study is to determine the feasibility of transforming the synthesis of single walled carbon nanotubes (SWNTs) from a process resulting in a mixture of tubes with different electronic properties (due to a range of diameter/chirality), to a scaleable, high yield, and efficient manufacturing process that allows for the formation of SWNTs of a particular diameter and hence electronic property. Such a process must allow for a high rate of production, be robust to system changes, and reliable. The most promising route to accomplish this goal is the process of SWNT amplification. In an analogous process to polymerase chain reaction (PCR) amplification of DNA, a single SWNT is attached to catalyst precursor forming a SWNT-cat. The catalyst precursor is reduced to form a metal nanoparticle creating intimate contact between the tube and particle. A growth gas is then introduced to begin growth of the SWNT. The resulting SWNT can be cut and the cycle repeated until the quantity of the desired SWNT is reached. The single (or small sample of) SWNT with a particular chirality would be grown into a large volume. In spite of the successful demonstration of SWNT-cat synthesis and growth there are several issues that must be addressed before large-scale SWNT amplification can succeed: (a) the percentage of SWNTs that are converted to SWNT-cat is low (50%), (b) the percentage of SWNT-cat that grows is low, (c) the average increase in length of the SWNT from SWNT-cat is low (300 nm), (d) the separation of individual seed SWNTs is limited to enrichment, and (e) the recycling and amplification of the grown SWNTs has not been demonstrated. Our initial results have demonstrated that the principle of SWNT amplification is possible, but in order to ascertain the viability of the process two of the key steps in this process must show potential for improvement: (a) chemical approaches to SWNT activation to allow binding of a catalyst particle, and (b) understanding of the requirements for activity of a pre-formed catalyst particle. The most important technical challenge facing the world in the 21st century is providing sustainable and universally available energy. In addition to conservation and evolutionary improvements in existing technologies, a solution to the global energy problem will require revolutionary new technology. With a projected increase in the global population from 6.5 billion in 2004 to over 10 billion in 2050 there will be a need for 30-60 tera watts of energy per year. The key technical component of a highly efficient power grid is power cables (quantum conductors) with which to rewire the electrical transmission grid and enable continental, and even worldwide, electrical energy transport. One material that offers a potential technical solution for low loss power cables is the armchair SWNT. If SWNT amplification can be moved from a demonstration of individual steps to a complete process then the ability to manufacture quantum wire conductors can be a reality. Through this project the graduate students will gain a cross-disciplinary education in nanotechnology. Each will be encouraged to participate at one national or international meeting. Through the Baker Institute for Public Policy at Rice the PI is actively involved in energy programs and energy policy. This interaction will allow students to become involved across a broad intellectual program with members of government, industry and academia. Rice University has significant expertise in the sidewall functionalization of SWNTs and the Barron Research Group has an active interaction with the groups of the Carbon Nanotube Laboratory.