Advancing Sustainable Nanotechnology: Towards the Development of a Design Framework for the Future Production of Functional and Inherently Safer Carbon Nanotubes (CNTs) and CNT-Enabled Products

Carbon nanotubes (CNTs) are an emerging class of nanomaterials that possess several attractive characteristics, including unique optical and electronic properties, significant thermal conductance, and exceptional tensile strength, which collectively contribute to their commanding market demand. Applications of CNTs can be found in nearly every industrial sector including energy, electronics, and biotechnology. As a single class of engineered nanomaterials (ENMs), CNTs comprise nearly one third of the current ENM market demand and are projected to reach ∼13,000 metric ton production volume by 2016.;The same novel properties that inspire the next generation of promising CNT-enabled applications are also a potential source of environmental and human health concern. In vitro and in vivo toxicity studies demonstrate the potential inherent CNT hazard ranging from loss of bacterial cell viability to the formation of granulomas in mammalian lung tissue. The severity of unintended consequences that could be realized upon exposure to CNTs has the potential to impart devastating impacts on the advancement of the field. This paradox that is the simultaneous realization of promising CNT applications and potential CNT implications serves as the motivation for this dissertation research.;One of the overall goals of this dissertation is to determine the efficacy of controlling CNT physicochemical properties via the addition of surface functional groups while at the same time resolving property-hazard relationships to inform future design of inherently safer CNTs and CNT-enabled products. A holistic and systematic approach to understanding the causal relationship between fundamental physiochemical properties and cytotoxicity is applied here to single- (SWNTs) and multi-walled (MWNTs) CNTs. In addition to molecular level design considerations, this research includes an evaluation of environmental and human health impacts at the product level. Results from a life cycle assessment (LCA) of a nano-enabled product currently under development elucidate the relative contribution of CNTs to the total cradle-to-use impacts of the product. In addition, the LCA study establishes a quantitative approach to evaluate the potential downstream human health benefits realized upon product implementation, which enables a tradeoff comparison with the upstream impacts.;The methods and approaches established herein are applicable across classes of nanomaterials and nano-enabled products. These research efforts are intended to provide a framework to move towards realizing a holistic understanding of nanomaterial and nano-enabled product risk across all life cycle stages and to inform future development of appropriate risk management strategies. As a result, nanotechnology has the potential to sustain its competitive edge within the consumer market and ultimately realize its intended positive impact on society and the environment without associated unintended consequences.