Advanced Characterization and Optical Properties of Single-Walled Carbon Nanotubes and Graphene Oxide

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dc.contributor.advisorWeisman, R. Bruceen_US
dc.creatorNaumov, Anton Viatcheslavovichen_US
dc.date.accessioned2013-03-08T00:37:05Zen_US
dc.date.available2013-03-08T00:37:05Zen_US
dc.date.issued2011en_US
dc.description.abstractPhotophysical, electronic, and compositional properties of single-walled carbon nanotubes (SWCNTs) and bulk nanotube samples were investigated together with graphene oxide photoluminescence. First, we studied the effect of external electric fields on SWCNT photoluminescence. Fields of up to 10 7 V/m caused dramatic, reversible decreases in emission intensity. Quenching efficiency was proportional to the projection of the field on the SWCNT axis, and showed inverse correlation with optical band gap. The magnitude of the effect was experimentally related to exciton binding energy, as consistent with a proposed field-induced exciton dissociation model. Further, the electronic composition of various SWCNT samples was studied. A new method was developed to measure the fraction of semiconducting nanotubes in as- grown or processed samples. SWCNT number densities were compared in images from near-IR photoluminescence (semiconducting species) and AFM (all species) to compute the semiconducting fraction. The results provide important information about SWCNT sample compositions that can guide controlled growth methods and help calibrate bulk characterization techniques. The nature of absorption backgrounds in SWCNT samples was also studied. A number of extrinsic perturbations such as extensive ultrasonication, sidewall functionalization, amorphous carbon impurities, and SWCNT aggregation were applied and their background contributions quantified. Spectral congestion backgrounds from overlapping absorption bands were assessed with spectral modeling. Unlike semiconducting nanotubes, metallic SWCNTs gave broad intrinsic absorption backgrounds. The shape of the metallic background component and its absorptivity coefficient were determined. These results can be used to minimize and evaluate SWCNT absorption backgrounds. Length dependence of SWCNT optical properties was investigated. Samples were dispersed by ultrasonication or shear processing, and then length-fractionated by gel electrophoresis or controlled ultrasonication shortening. Fractions from both methods showed no significant absorbance variations with SWCNT length. The photoluminescence intensity increased linearly with length, and the relative quantum yield gradually increased, approaching a limiting value. Finally, a strong pH dependence of graphene oxide photoluminescence was observed. Sharp and structured excitation/emission features resembling the spectra of molecular fluorophores were obtained in basic conditions. Based on the observed pH-dependence and quantum calculations, these spectral features were assigned to quasi-molecular fluorophores formed by the electronic coupling of oxygen-containing addends with nearby graphene carbon atoms.en_US
dc.format.extent188 p.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.callnoTHESIS PHYS. 2011 NAUMOVen_US
dc.identifier.citationNaumov, Anton Viatcheslavovich. "Advanced Characterization and Optical Properties of Single-Walled Carbon Nanotubes and Graphene Oxide." (2011) Diss., Rice University. <a href="https://hdl.handle.net/1911/70369">https://hdl.handle.net/1911/70369</a>.en_US
dc.identifier.digitalNaumovAen_US
dc.identifier.urihttps://hdl.handle.net/1911/70369en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectApplied sciencesen_US
dc.subjectPure sciencesen_US
dc.subjectSingle-walled carbon nanotubesen_US
dc.subjectGraphene oxideen_US
dc.subjectPhotoluminescenceen_US
dc.subjectNanomaterialsen_US
dc.subjectNanoscienceen_US
dc.subjectOpticsen_US
dc.titleAdvanced Characterization and Optical Properties of Single-Walled Carbon Nanotubes and Graphene Oxideen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentPhysicsen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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