Date of Graduation

2018

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Lisa A Holland

Committee Co-Chair

Jonathan W Boyd

Committee Member

Jeremy M Dawson

Committee Member

Harry O Finklea

Committee Member

Stephen Valentine

Abstract

Carboxylation of multiwall carbon nanotubes is used to enhance physical properties by improving dispersion, increasing compatibility and providing an interface for surface interaction. Accurate characterization of the multiwall carbon nanotubes surface is important as multiple applications depend on controlled functionalization. This dissertation is based on research that led to the adaption, validation and application of a capillary electrophoresis method for characterization of surface modification and interaction of carboxylated multiwall carbon nanotubes. The affinity based method uses electrostatic interaction of a selective peptide probe (WRWWWW) with multiwall carbon nanotubes to determine the degree of carboxylation. A 20% RSD in method reproducibility and repeatability was determined using within and cross day sample analysis. Method validation performed with two commercially available multiwall carbon nanotubes samples showed a significant difference in carboxylation, which was confirmed with X-ray photoelectron microscopy. In addition, the method was applied to assess the degree of carboxylation of acidified pristine multiwalled carbon nanotubes. A significant decrease in apparent dissociation constant was determined with increased acid treatment time, while no significant difference was determined using zeta potential analysis. Furthermore, capillary electrophoresis was also applied to isolate key factors that govern the interaction between multiwall carbon nanotubes and amino acids, arginine and tryptophan. For this analysis, the peptide probe was substituted with peptides containing either single or multiple amino acid substitutions or deletions. The study showed a two-fold increase in an electrostatic interaction of arginine in comparison to lysine and increased hydrophobic interaction with tryptophan chain length, revealing that both arginine and tryptophan drive peptide-carbon nanotube interactions. This method, for the first-time, allows for quantification of the individual contributions of amino acids and characterization of bulk multiwall carbon nanotubes samples with capillary electrophoresis. This research is significant to the study and development of nanotube-biomolecule applications and provides a cost-effective, rapid and simple alternative to current methods.

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