CAREER: Quantum Dot Degradation in Aquatic Environments

CBET-1254245智力优点。随着纳米材料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。这项研究是一项计划，以描述量子点的命运在代表性的水生环境受到广泛的化学条件，同时探索特定的降解机制和环境因素，影响这些过程。量子点（QD）是具有核/壳结构的半导体纳米晶体，通常小于20 nm，并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颗粒一样，可能会发生物理（聚集）和化学（溶解）转变，这些转变会影响其释放到接收水体时的整体生物利用度。虽然CdSe/ZnS量子点的毒性及其浸出的金属已被仔细检查了各种微生物，其降解过程的更多的机制细节是需要为各种类别的量子点进行不同的水生化学，以更好地预测其整体future.The总体目标的建议是要确定如何不同类型的量子点，无论是传统的和下一代，在水生环境和废物流中降解。具体目标是（1）开发一种稳定、快速的分析方法，用于使用单粒子电感耦合等离子体质谱法鉴定和定量颗粒、络合和溶解形式的QD元素，几乎不需要样品预处理（SP-ICPMS）和分子排阻色谱法（SEC-ICPMS），（2）鉴定促进QD降解和元素释放的各种类型有机物的配体基团，（3）确定UV和可见光在促进QD降解中的影响，（4）评估可能影响QD降解的其他无机地球化学因素，例如溶解的氢、氧和硫化物，以及（5）确定是否可以改变QD涂层的物理化学性质以防止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反应器内确定。这些结果将提供有关地球化学溶液条件、溶解的有机化合物以及紫外和可见光对各种量子点溶解的作用的基本信息。这里开发的SP-ICPMS将应用于其他金属纳米粒子测量在沃茨。更广泛的影响-实验室调查到QD降解过程将导致更深入的了解QD寿命预期释放到水生环境中后，这些信息将导致改进的QD涂层设计。这项工作将提供教育，每年一名研究生和几名本科生在环境工程。该研究机会提供了水质，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。代表性不足的群体的广泛参与将通过向本科生、马萨诸塞州教师和当地高中生提供实践实验室参与的体验式学习机会来解决。他们的研究经验将通过支持QD合成，反应和表征方法以及通过协助开发教育材料以指导广大受众了解环境科学和工程原理的教育计划来融入PI的研究计划。这些材料的目的是促进系统思维教育使用基于WWW的多媒体模块组成的图形，视频和系统建模工具。该教育计划的成果将通过实地考察演示和课程模块传达给当地的初中、高中和本科学生。

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.