The Synthesis of a Homologous Series of Alkyl Lumazines and their Application to the Dispersion of Carbon Nanotubes

<p>In this thesis, the synthesis of a series of alkyl lumazine surfactants (<strong>LC_n</strong>) is reported. Their application to the dispersion of both CoMoCAT and HiPco single-walled carbon nanotubes (SWNTs) is examined in detail and the thermal stability and chirality selection properties of dispersions made with these surfactants were compared both between themselves and with an alkyl flavin surfactant (<strong>FC₁₂</strong>). Lumazine alkyl chain length exhibited some control over the quality and the quantity of SWNTs dispersed. <strong>LC₁₀</strong> was deemed most appropriate for comparison with <strong>FC₁₂</strong> based on considerations of solubility and nanotube individualization. Although the lumazines were less diameter-selective than the flavins, they still appeared to favor smaller-diameter tubes (<1 >nm) as compared to the <strong>FC₁₂</strong>. The helix formed by <strong>FC₁₂</strong> on the surfaces of SWNTs is shown to be preserved in <strong>LC_n</strong> surfactants by the existence of a sigmoidal decay in SWNT fluorescence intensity upon heating SWNT dispersions, which is the same in form as the decay exhibited by <strong>FC₁₂</strong>-wrapped SWNTs. This decay, however, occurs at a slightly higher (~4°C) temperature and more sharply for <strong>LC_n</strong>. The sum total of these properties indicates that the smaller unit size of the <strong>LC_n</strong> and the lower π-π stacking ability as compared to <strong>FC₁₂</strong> enable greater flexibility in supramolecular assembly, resulting in lower selectivity and the selection of smaller SWNTs, and that the more electron-poor, lower π-π stacking lumazine forms a helix that is more cohesive than one made from flavins, yet with individual molecules that are more easily separated from the SWNT once the helix is ruptured.</p>

Name thesis:degree_name

Master of Science

Discipline thesis:degree_discipline

Chemistry

Year dc:date.available

2012

Author dc:creator

• Kopcha, William P.

Contributors dc:contributor

• Douglas Adamson; Alexandru D. Asandei
• Fotios Papadimitrakopoulos

• carbon nanotubes
• organic chemistry
• synthesis
• helix
• stability
• flavin
• lumazine

Repository record dc:identifier

https://digitalcommons.lib.uconn.edu/gs_theses/233

OAI identifier oai:identifier

oai:digitalcommons.lib.uconn.edu:gs_theses-1259