Rational Design of High-Purity Carbon Nanotube Dispersions Through Acute and Full Life-CycleToxicity Studies

University Of Florida, Gainesville FL

Investigators

Abstract

Proposal Title: Rational Design of High-Purity Carbon Nanotube Dispersions through Acute and Full Life-Cycle Toxicity Studies Principal Investigator: Kirk Ziegler Institution: University of Florida Proposal No: CBET- 0853347 This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The dramatic increase in production rates of single-walled carbon nanotubes (SWNTs) and the anticipated widespread use of SWNTs in commercial and industrial applications suggest that these manufactured nanomaterials will inevitably enter the environment including the biosphere. In addition, there is a growing concern because of the currently unknown environmental and human health impacts of SWNTs. Besides the toxicity issues common to all nanomaterials, the environmental and human health implications of SWNTs are complicated by the presence of impurities, such as the transition metal catalyst, and aggregation state. These issues are also important problems to resolve in most SWNT applications. Challenges still remain in purifying and dispersing SWNTs without detrimentally affecting the unique size-related characteristics such as strength, elasticity, high adsorption capacity, and controllable conductivity. Future applications of nanotubes will be limited unless new approaches are developed to overcome these issues without impacting the unique properties of SWNTs. Their long term goal is to develop stable, high-purity, SWNT dispersions based on large-scale processes that minimize the risks to the environment and human health. They hypothesize that the environmental and human health impacts of engineered SWNTs can be reduced or eliminated through intimate coupling of toxicity testing and manufacturing during the production process. Environmentally benign manufacturing is an important goal for the emerging nanomaterial industries, ensuring that risks to human health and the environment are minimal. Indeed, nanotube processing has a tremendous opportunity to evolve as a "green" process, benefiting from the experience of previous industrial enterprises. To test the hypothesis, engineering, chemistry, and toxicology will be integrated into a preemptive experimental approach. If necessary, toxicity assessments will dictate refinement of the SWNT purification and dispersion processes to reduce their potential hazard. This novel feedback feature intimately couples manufacturing with toxicity tests of produced SWNTs evaluated after each of the following key production steps: (1) synthesis and dry powder production (baseline toxicity); (2) purification; and (3) dispersion. This work may provide a purification process which can achieve high purities and high yields of SWNTs without causing damage to the tubular structures while simultaneously minimizing risks to the environment. Aside from the benefits of developing an environmental-friendly manufacturing process, this work will enable and accelerate nanotube applications impacting energy technologies, materials science, nanoelectronic, bionanotechnology, and medical fields. A recent framework established by DuPont and Environmental Defense encourages the evaluation of toxicity effects at the design stage of nanomaterials so new, environmental-friendly processes can be developed. The successful completion of this project will help identify the mechanisms by which SWNT dispersions affect aquatic organisms. It is expected that this fundamental information will help reduce/eliminate the potential negative impacts of SWNTs. An additional objective of this project is to disseminate the lessons learned from this research and develop an educational program targeting undergraduate students, especially from underrepresented groups. Nanotechnology is a new frontier for the scientists and engineers of the 21st century. NSF estimates that 2 million workers will be needed to support future nanotechnology industry needs. However, the decreasing enrollment of U.S. students in science, technology, engineering, and mathematics (STEM) degrees make it challenging to prepare the needed workforce. The PIs are currently developing modules for a sequence of two undergraduate courses aimed at integrating nanotechnology and its environmental, societal, and health implications into the current undergraduate curricula. These courses will, therefore, be used as a vehicle to integrate their exciting research findings into new educational materials.