Influence of diameter and chirality of single-walled carbon nanotubes on their fate and effects in the aquatic environment

单壁碳纳米管（SWNTs）已成为高性能纳米材料，具有广泛的应用，包括电子、光学、医疗和结构复合技术。由于它们在大规模工业生产中的预期作用，毫无疑问，单壁碳纳米管最终将进入我们的水生环境。与其他纳米颗粒相比，swnt的不同寻常的物理化学特性——特别是它们非常大的长宽比和复杂的胶体行为（如聚集）——阻碍了对其胶体稳定性和运输行为的有意义的理论预测。此外，关于SWNT结构特性（如直径和电子结构）对其在水生系统中的命运、运输和生物相互作用的影响的基础研究完全缺乏。因此，目前还没有可靠的方法来基于可测量的纳米材料的物理性质来预测纳米碳纳米管在自然水生环境中的命运和影响。本课题旨在从根本上了解单壁碳纳米管的结构特性对其在自然水生环境中的命运和生物行为的影响。该研究设计包括系统评估鱼类（日本medaka）对半导体SWNTs的聚集、沉积、有机化合物吸附和摄取/毒性，这些SWNTs具有一系列电子结构（随之产生的直径和手性变化）。这些研究将是完全新颖的，因为文献中没有关于基本结构特性对swnt的环境命运和影响的基础研究报告。提出的研究将涉及以下目标。(1)利用密度梯度超离心，通过直径/手性分离半导体swcnts；(2)利用最先进的动态光散射、石英晶体微天平和常规柱流输运实验，研究粒径/手性分选的SWNT组分的聚集和沉积动力学与有机质浓度和离子强度的关系；(3)采用常用顶空分配法测定SWNT直径/手性对有机污染物吸附的影响；(4)利用近红外荧光光谱和显微镜技术评估日本medaka鱼对直径/手性分类的SWNTs的吸收、生物分布和毒性效应。该研究将通过系统地了解结构特性对SWNT命运、运输和生物行为的影响，填补科学文献中的一个关键空白。本研究的结果可能导致水环境中swnt的结构-性质关系，允许对其命运，运输和影响进行先验预测，因此符合NSF为变革性研究设定的定义。预期的研究成果和收益包括实现系统分离手性碳纳米管的技术；完全理解电子结构对胶体稳定性、沉积和吸附性能的影响；SWNT电子结构在生物吸收和毒性作用中的作用；最后，增加了对水环境中表面结构对纳米材料行为和效果影响的知识基础。基础科学理解的增加将最终导致结构-活性关系，由此我们可以建立策略来评估纳米材料在环境中的风险，就像目前可能的分子环境污染物一样。拟议的活动将产生关键知识，以更好地理解商业上重要的一类纳米材料对环境的影响。申请的大部分资金用于培养新兴和跨学科研究课题的博士生。这项研究将通过教学和探索带来发现和理解。它为学生提供教育、指导，并在一个对我们的社会具有直接和至关重要的新颖和高度相关的领域进行研究。这个项目有可能通过与两所少数民族院校的学生交流活动，让少数民族学生参与进来。计划通过会议报告和同行评议出版物传播研究成果。

0933484SalehSingle-walled carbon nanotubes (SWNTs) have emerged as high-performance nanomaterials with numerous applications, including electronic, optical, medical, and structural composite technologies. Because of their anticipated role in large-scale industrial production, there is little doubt that SWNTs will ultimately find their way into our aquatic environment. The unusual physicochemical characteristics of SWNTs compared to other nanoparticles -- particularly their very large aspect ratio and complex colloidal behavior (e.g. aggregation) in aqueous solutions -- preclude meaningful theoretical predictions of their colloidal stability and transport behavior. Furthermore, there is a complete lack of fundamental studies on the effects of SWNT structural properties (e.g. diameter and electronic structure) on their fate, transport and biological interactions in aquatic systems. Consequently, there exist no reliable methods to predict the fate and implications of SWNTs in natural aquatic environments based on measurable physical properties of these nanomaterials. The purpose of this proposal is to fundamentally understand the effect of structural properties of SWNTs on their fate and biological behavior in the natural aquatic environment. The study design involves systematic evaluation of aggregation, deposition, organic compound sorption, and uptake/toxicity in fish (Japanese medaka) for semiconductive SWNTs for a range of electronic structures (with consequent variation in diameter and chirality). These studies will be fully novel, as there are no fundamental studies reported in the literature examining the effect of basic structural properties on environmental fate and implications of SWNTs. The research proposed will address the following aims. (1) Fractionation of semiconductive SWNTs by diameter/chirality using density gradient ultracentrifugation; (2) examination of aggregation and deposition kinetics of diameter/chirality-sorted SWNT fractions as a function of organic matter concentration and ionic strength using state-of-the-art dynamic light scattering, quartz crystal microbalance, and conventional column-flow transport experiments; (3) determination of the effect of SWNT diameter/chirality on organic contaminant adsorption using common headspace-partitioning methods; and (4) assessment of the uptake, bio-distribution, and toxic effects of diameter/chirality-sorted SWNTs in Japanese medaka fish after waterborne- or dietary exposure using near-IR fluorescence spectroscopy and microscopy. The proposed research will fill a critical gap in the scientific literature by providing a systematic understanding of the effects of structural properties on SWNT fate, transport and biological behavior. Results of this study may lead to structure-property relations for SWNTs in aquatic environments, allowing a priori predictions of their fate, transport and effects and therefore meets the definition set forth by the NSF for transformative research. The expected research outcomes and benefits include implementation of techniques to systematically separate chiral SWNTs; a complete understanding of the effects of electronic structure on colloidal stability, deposition, and sorptive properties; role of SWNT electronic structure on biological uptake and toxic effects; and finally an increased knowledge-base on the influence of surface structure on the behavior and effects of nanomaterials in the aquatic environment. This increase in basic scientific understanding will ultimately lead to structure-activity relationships from which we may build strategies to assess risks of nanomaterials in the ambient environment, as is currently possible for molecular environmental contaminants. The proposed activity will generate critical knowledge to better understand the environmental implication of a commercially important class of nanomaterial. The majority of requested funds are directed toward the training of doctoral students in an emerging and interdisciplinary research topic. This research will lead to discovery and understanding through teaching and exploration. It provides for student education, mentoring, and research in a novel and highly relevant area that is of immediate and critical importance to our society. This project has potential to involve minority students through student exchange activities with two minority institutions. Dissemination of the research results is planned through conference presentations and peer-reviewed publications.