Novel Carbon Nanomaterials: Synthesis and Applications

Carbon nanotubes (CNTs) hold exceptional promise for an array of applications in numerous disciplines. Discovered in 1991 by Sumio Iijima, CNTs have been synthesized in a myriad of varieties including single-walled (SWNTs), multiwalled (MWNTs), and chemically doped, resulting in unique electronic and physical properties, as well as an innate biocompatibility towards biological organisms. Such attractive properties have been demonstrated in CNTs' implementation in applications such as electronic sensors, drug delivery vehicles, and reinforcements in composite materials. Moreover, by chemical doping, carbon nanomaterial hybrids have been formed with intrinsic morphological and physical properties differing from their un-doped counterparts.Despite successful execution in these areas, reports have been generated indicating degrees of cytotoxicity induced by carbon nanotubes. Specifically, CNTs have demonstrated asbestos-like pathogenicity, resulting in pro-inflammatory response and granuloma formation. Additionally, because CNTs are composed of sp2 hybridized carbon atoms, they possess an inherent resiliency toward degradation. In my Ph.D. studies, we have addressed multiple facets of the growing field of carbon nanomaterials. We have synthesized a nitrogen-doped carbon nanomaterial using the process of chemical vapor deposition, which we called nitrogen-doped carbon nanotube cups. These doped nanostructures can be conceptualized as stacked cups, which can be separated into individual cups through mechanical grinding. Characterized through a variety of microscopic and spectroscopic methods, we observed that the presence of nitrogen functionalities on the cups' open basal rims allows for cross-linkage, forming nanocapsules capable of encapsulating a desired cargo. We also hypothesize that the presence of nitrogen functionalities will increase their biocompatibility for drug delivery and imaging applications. To address the realm of "nanotoxicity", we have performed investigations of benign degradation methods, specifically enzymatic catalysis, to oxidize carbon nanomaterials. We have observed that incubation of carbon nanomaterials with a peroxidase-based enzyme (such as horseradish peroxidase) with low levels of H2O2 (40 µM) results in the oxidation of carbon nanomaterials to CO2 gas over ten days at room temperature. Subsequent research has elucidated the nature of interactions between carbon nanotubes and enzymatic cofactors. These studies, thus, elucidate a benign approach to degrade carbon nanomaterials, typically oxidized under harsh acidic conditions or thermal oxidation in air