Optical studies and chiral purification of single -walled carbon nanotubes

by McDonald, Timothy J., Ph.D., COLUMBIA UNIVERSITY, 2007, 156 pages; 3266639

Abstract:

Single-walled carbon nanotubes (SWNTs) are candidates for energy, photonic, and electronics applications. However, many fundamental questions remain about SWNT optical properties, such as an explanation for the low apparent nanotube quantum yield and the absolute potential of energy levels. Also, many proposed ideas require separation by type. To address these issues, a spectrometer for detection of SWNTs photoluminescence (PL) with tunable excitation was developed. The instrument offers rapid, robust, and sensitive detection, and was used to perform low-temperature PL measurements and confirm predictions that SWNT recombination kinetics are influenced by multiple excitonic bands, including a dark lower state. Toward the goal of obtaining a single nanotube type, the spectrometer's speed advantage has allowed for the study the kinetics of PL quenching as isolated nanotubes rebundle in suspension. Temperature dependent studies of the rebundling kinetics were used to determine the relative binding strength of each nanotube structure to various aqueous surfactant molecules. A strong binding for a single nanotube type to a particular surfactant molecule was found. This selectivity was utilized to chemically oxidize all but that nanotube type, and a novel separation technique was proposed. Optical emission from SWNTs confirms the first complex of SWNTs and hydrogenase, such that the nanotubes remain stably suspended, the hydrogenase remains active, and the two are in intimate electrical contact. In addition to their utility in artificial photosynthesis schemes and in replacing platinum in fuel cells, these complexes can be utilized to unambiguously measure the absolute potential of the electronic levels of SWNTs for the first time.

AdviserMichael J. Heben
SchoolCOLUMBIA UNIVERSITY
Source TypeDissertation
SubjectsPhysical chemistry; Condensed matter physics; Materials science
Publication Number3266639

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