Collaborative Research: Diameter and Chirality Control and Regrowth of Single-Walled Carbon Nanotubes

Yale University, New Haven CT

Investigators

Abstract

PROPOSAL NUMBER: 0828771 (collaborative with 0828824) PRINCIPAL INVESTIGATOR: Pfefferle, Lisa (Papadimitrakopolous, Fotios) INSTITUTION: Yale University (U. Connecticut) Collaborative Proposal: Diameter and Chirality Control and Re-growth of Single-Walled Carbon Nanotubes Intellectual Merit: Synthesizing useful quantities of uniform (n,m) identity single-walled carbon nanotubes (SWNT) is a serious challenge, necessary for advanced electronic applications and a major limitation facing high-end SWNT applications. An attractive route involves the isolation of small batches of the given SWNT, followed by cutting into "seeds", achieving effective tube end catalyst templating, and regrowth from the ends maintaining the original (n,m)-chirality. Recent exciting methodologies involving molecular manipulation and templating propose to address this separation and regrowth challenge, but these are inherently complex and difficult to scale, and it is not clear whether seed chirality is maintained and whether regrowth preferentially favors certain species. We have developed preliminary data that it is feasible to reactively template the growth catalyst on the SWNT ends, offering the potential for substantial easing of the complexity of the catalyst templating process with a more effective and scalable process. By loading catalyst on the inside of shortened SWNT "seeds", and adding reactant (e.g. H2) at proper conditions, we are producing SWNT "seeds" with catalyst templated for effective lengthening in a regrowth process with the bulk identity distribution maintained. Two effective templating reagents include hydrogen through methanation or COB2B through reverse disproportionation. Temperature is key, and depends on the reagent/catalyst pair and also on the tube identity. This approach makes chemical sense as it mimics the SWNT growth process itself. We present proof of principle of gas phase regrowth of dispersed SWNT seeds. Advantages include process scalability, fidelity and reduced post-processing for lower defect rate. Regrowth also will be probed using P13PC-enriched SWNT seeds, with given (n,m)-abundance profiles, to establish whether P12PC-enriched regrowth is initiated at the seed-tips and chirality is maintained. We will investigate the regrowth process as a function of different diameter, chirality and metallicity of SWNT, produced by: (i) our previously demonstrated synthesis of narrow-diameter distribution SWNT and (ii) SWNT fractionated by the co-PI according to type, diameter and chirality. We have demonstrated the ability to produce SWNT samples with different (n,m)-abundances, narrow diameter distribution and mean diameter varying from 0.6 to 1.7 nm. The proposed effort combines complementary expertise of the PI in nanotube synthesis and the extensive specialization of the co-PI in nanotube separation and quantitative (n,m)-characterization using photoluminescence and tunable-laser resonance Raman spectroscopy. This combined expertise will allow exploring the mechanism of our regrowth process along with optimization. Mechanism studies will also take advantage of the PIs work on X-ray absorption analysis of SWNT growth catalysts under reaction conditions. Broader Impacts: Chemical production of specific (n,m) SWNT would revolutionize the SWNT device industry. The method to be explored is inexpensive, requires little post processing and would put good quality SWNT in the hands of many more researchers. SWNT also provides an exciting material for interesting undergraduates in research: our activities include developing a lab-based course involving students from local non-PhD granting institutions, involving participation in a research project on water remediation and the interaction of SWNT with microbes. Students will see how SWNT are made, participate in functionalization for water solubility, and do experiments in their home lab to assess SWNT toxicity to a target microbe. This will be linked to the Co-PIs involvement in a Connecticut-wide course development in Nanotechnology for undergraduates. This includes developing UConn's "Nanovan-Project", where an AFM microscope is loaded into a van and driven to high schools for live demonstrations including a SWNT demonstration.