CAREER: Quantum Dot Degradation in Aquatic Environments

生态旅游- 1254245知识价值。随着基于纳米材料的产品的预计市场每年接近数万亿美元，这些产品及其废物的管理将不可避免地对环境健康构成挑战，特别是当纳米材料通过产品处置或工业废物流释放时。本研究计划描述量子点在受广泛化学条件影响的代表性水生环境中的命运，同时探索影响这些过程的特定降解机制和环境因素。量子点（QDs）是一种半导体纳米晶体，其核/壳结构通常小于20nm，用于荧光测量和能量应用，并且，与过去十年研究的其他金属纳米粒子一样，可能经历物理（聚集）和化学（溶解）转化，从而影响其释放到接收水体后的整体生物利用度。虽然CdSe/ZnS量子点及其浸出金属的毒性已经对各种微生物进行了密切的研究，但为了更好地预测它们的整体命运，需要更多的降解过程的机械细节，以使不同种类的量子点受到不同的水生化学反应。本提案的总体目标是确定不同类型的量子点，包括传统的和下一代的，如何在水生环境和废物流中降解。具体目标是：(1)开发一种强大、快速的分析方法，用于识别和定量QD元素的颗粒、络合和溶解形式，几乎不需要样品预处理，使用单颗粒电感耦合等离子体质谱（SP-ICPMS）和尺寸排除色谱（SEC-ICPMS）；(2)识别促进QD降解和元素释放的各种有机物质的配基。(3)确定紫外线和可见光对促进QD降解的影响；(4)评估其他可能影响QD降解的无机地球化学因素，如溶解氢、氧和硫化物；(5)确定是否可以改变QD涂层的物理化学性质以阻止QD降解。反应速率和产物分布将在含有量子点和地球化学成分的各种组合的间歇式反应器中确定。该结果将为地球化学溶液条件、溶解的有机化合物、紫外和可见光对各种量子点溶解的作用提供基础信息。这里开发的SP-ICPMS将应用于水中其他金属纳米颗粒的测量。对量子点降解过程的实验室研究将使人们更深入地了解释放到水生环境后量子点的寿命，这些信息将导致改进量子点涂层的设计。这项工作每年将为一名环境工程研究生和几名环境工程本科生提供教育。研究机会提供水质、无机合成化学和矿物学技术方面的各种实验和分析仪器培训。通过为本科生、马萨诸塞州教师和当地高中生提供实践学习机会，扩大未被充分代表群体的参与。他们的研究经验将通过支持量子点合成、反应和表征方法来整合到PI的研究计划中，并通过协助开发教育材料来指导广大受众关于环境科学和工程原理的教育计划。这些材料旨在利用基于www的多媒体模块，包括图形、视频和系统建模工具，培养系统思维教育。该教育计划的成果将通过实地考察示范和课程模块传达给当地的初中、高中和本科生。

CBET-1254245Intellectual Merit. With the projected market for nanomaterial-based products approaching in the trillions of dollars annually, management of these products and their waste will inevitably pose challenges to environmental health, particularly when nanomaterials are released through product disposal or industrial waste streams. This study is a plan to describe quantum dot fate in representative aquatic settings subjected to broad chemical conditions while exploring specific degradation mechanisms and environmental factors that influence these processes. Quantum dots (QDs) are semiconducting nanocrystals with core/shell structures often less than 20 nm and employed in fluorescent measurements and energy applications, and, like other metallic nanoparticles studied over the past decade, may undergo physical (aggregation) and chemical (dissolution) transformations that influence their overall bioavailability upon release to receiving water bodies. While the toxicity of CdSe/ZnS QD and their leached metals have been examined closely for a variety of microorganisms, more mechanistic details of their degradation processes is needed for the various classes of QDs subjected to diverse aquatic chemistries in order to better predict their overall fate.The overall goal of this proposal is to determine how different types of QDs, both conventional and next-generation, degrade in aquatic environments and waste streams. Specific objectives are (1) to develop a robust, rapid analytical procedure for identifying and quantifying QD elements in their particulate, complexed, and dissolved forms with almost no sample pre-treatment using single-particle inductively coupled plasma mass spectrometry (SP-ICPMS) and size exclusion chromatography (SEC-ICPMS), (2) to identify the ligand groups of various types of organic matter that promote QD degradation and element release, (3) to determine influence of UV and visible light in promoting QD degradation, (4) to evaluate other inorganic geochemistry factors such as dissolved hydrogen, oxygen, and sulfide that may influence QD degradation, and (5) to determine whether physicochemical properties of QD coatings can be altered to prevent QD degradation. Reaction rates and product distributions will be determined within batch reactors containing various combinations of QDs and geochemical constituents. The results will provide fundamental information on the roles of geochemical solution conditions, dissolved organic compounds, and UV and visible light exert on the dissolution of a variety of QDs. The SP-ICPMS developed here will have application to other metallic nanoparticle measurements in waters.Broader Impacts The laboratory investigations into QD degradation processes will lead to a deeper understanding of QD longevity to be expected upon release into aquatic environments, and this information will lead to improved designs of QD coatings. This work will provide education for one graduate student per year and several undergraduate students in environmental engineering. The research opportunity provides diverse experimental and analytical instrumentation training in water quality, inorganic synthesis chemistry, and mineralogical techniques. Broadened participation of underrepresented groups will be addressed by providing experiential learning opportunities through hands-on laboratory engagement to undergraduate students, Massachusetts state teachers, and local high school students. Their research experiences will be integrated into the PI's Research Program by supporting QD synthesis, reaction, and characterization methods as well as the Educational Program by assisting development of educational materials for the instruction of broad audiences about the principles of environmental science and engineering. These materials are intended to foster systems thinking education using WWW-based multimedia modules comprised of graphical, video, and systems modeling tools. The results of this Educational Program will reach local middle school, high school, and undergraduate students through field trip demonstrations and curriculum modules.