Institution: Yale University
Proposal No: CBET- 0854373
This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
The objective of this study is to develop the fundamental understanding necessary to design carbon nanotubes with reduced risk to human health and the environment. Knowledge to support this goal will be gathered through biotoxicity testing of well-characterized pristine and functionalized carbon nanotubes, both single-walled carbon nanotubes, SWCNTs, and multi-walled carbon nanotubes, MWCNTs. The modified CNTs will then be evaluated for stability under representative environmental conditions, and those CNTs that undergo a transformation in environmental conditions will be reevaluated for toxic characteristics. Completion of the proposed work will involve the following tasks: (i) synthesis of CNTs, (ii) surface functionalization of CNTs, (iii) characterization of CNTs, (iv) evaluation of CNT biotoxicity, (v) characterization of environmental transformations of CNTs in aquatic systems, (vi) aggregation of CNTs, (vii) analysis of the impacts of changes resulting from environmental conditions on toxicity, and (viii) consideration of policy implications. They will synthesize well-defined SWCNTs and MWCNTs. In addition to the testing of pristine CNTs, they will test a range of functionalizations that result in CNTs with enhanced solubility and a range of polarities. These include amino, hydroxyl, carboxy, sulfonate, alkyl, and pyrrolidinyl functionalized CNTs, as well as fluorinated SWCNTs, the most densely functionalized CNTs known to date. Careful characterization of the synthesized and functionalized CNTs is critical for the formation of meaningful conclusions from the biotoxicity studies. They will use advanced characterization tools to obtain information about the CNT purity and physical and chemical properties, including Raman, FTIR, and Near IR fluorescence spectroscopy; TEM, TGA, and zeta potential measurement. They will then test the biotoxicity of the pristine and functionalized CNTs to gain insights into the role of CNT chemical and physical properties on their toxicity. Once released into the aquatic environment, functionalized CNTs will undergo chemical and physical transformations. They will investigate the stability of the chemical functionalizations under environmental conditions and the impact of these transformations on CNT biotoxicity. Finally, the implications of the results for policies regarding the design of safer CNTs will be discussed. The results from this study will provide information on (i) surface modifications to CNTs that result in reduced or no toxicity, and (ii) the stability of these modifications in environmental conditions for long-term protection of human health and the environment. Ultimately, the information will be used to design the next generation of CNTs.
Current research demonstrates the potential for an increase in the recruitment and retention of women and underrepresented groups in science and engineering courses and majors when the type of issues this project is focused on are introduced into the curriculum. It is anticipated that similar trends will be observed at Yale University, which already graduates the highest percentage of female undergraduate engineering students in the country. While this project will serve as a source of research opportunities for undergraduate and graduate students as well as be integrated into existing courses at Yale, they also have a unique and innovative contribution to broaden the impacts of this project. Together with staff and associated students at Yale?s Peabody Museum of Natural History, the project team will be working to develop an age appropriate module for their School Programs for grades 7-12 on sustainability to include components on green product design and environmentally benign manufacturing. Through this experience, these students would gain a better understanding of the challenges associated with designing and developing products and processes that meet environmental, economic, and social goals as well as the role of consumers in the system.
