Controlling the Growth of Branched Carbon Nanotubes

1. Controlling the Growth of Branched Carbon Nanotubes Wenzhi Li, Florida International University, DMR 0548061 Branched carbon nanotubes (carbon nanotube junctions) have been identified as promising materials for applications in nanoelectronic devices due to their nonlinear electrical properties. Nanotube junctions can be synthesized by the chemical vapor deposition (CVD) technique. In the CVD process, the formation of the nanotube junctions is extremely sensitive to the concentration of hydrocarbon vapor. In this project, thiophene (C4H4S) has been used as carbon source to grow nanotubes on Co catalyst nanoparticles, and the influence of the concentration of C4H4S vapor on the structure of the nanotubes has been investigated. It is found that nanotube junctions grow when the C4H4S concentration is in the range of 0.76-1.5%. Otherwise, carbon fibers are produced at higher C4H4S concentrations and Co9S8 nanowire-filled nanotube form at lower concentrations. Transmission electron microscopy images of (a) carbon fibers, (b) branched nanotube, (c) Co9S8 nanowire-filled nanotube, and (d) hollow nanotubes grown at various thiophene (C4H4S) vapor concentrations at 3.0, 1.5, 0.51, and 0.37 vol.%, respectively. Li, Pandey, Liu, J. Phys. Chem. B 110, 23694 (2006);Du, Li, Liu, Ding, Wang, http://pubs.acs.org/cgi-bin/download.pl?jp0740292/Q3aN

2. Controlling the Growth of Branched Carbon Nanotubes Wenzhi Li, Florida International University, DMR 0548061 Education and Outreach: Two graduate students (Bimal Pandey and Tao Zhang) contributed to the project. Tao Zhang has just graduated with master degree. Two undergraduate students (Ramona Valenzuela and Richard Galvez) carried out their independent study and McNair project in the PI’s lab and they contributed to the research project. Collaborating with the FIU “Physics Learning Center” and the “Center for High Energy Physics Research & Education Outreach,” the PI has given lab tours and demonstrated his research results to about 50 high school students and teachers. Undergraduate student Ramona Valenzuela is involved in a research project in the PI’s lab. Following is a news published on newspaper Miami Herald on May 13, 2007. “Coral Park High seniors Ankur Shah and Charlie DeVivero, both 18, spent last summer in a lab at Florida International University, researching the uses of carbon nanotubes. The rolled sheets of graphite, about a single atom thick, have a host of uses, such as in building tiny electronic devices, said Ankur, who will attend Stanford. The commitment that drove Ankur and Charlie to spend their summer in a lab instead of on the beach helped boost their performance in challenging college-level.” High school students Charlie DeVivero (left, now enrolled at MIT) and Ankur Shah (right, now enrolled at Stanford) were doing summer research in the PI’s lab.