EAGER: CAS-MNP: Mapping the structure–property relationships of micro- and nanoplastics by in-situ nanoscopic imaging and simulation

非技术总结：这个合作项目结合实验和模拟来了解微塑料和纳米塑料，这是人类肉眼看不见的微小塑料碎片，已被证明无处不在地存在于食物链和环境中。因此，微塑料和纳米塑料对人类健康、生态系统和食物的不可预测的影响引起了人们的关注。例如，在淡水、咸水鱼类和空气中都可以发现体积较大的微塑料，其浓度很高，形状各异，如碎片、泡沫和颗粒。在水中发现的纳米塑料（小于100纳米）可能对人类健康特别令人担忧，因为它们的大小属于活细胞可以吸收的小颗粒。微塑料和纳米塑料不能使用基于统计平均的传统工具包进行彻底检查。正是由于这些原因，本提案的研究目标是引入和使用液相透射电子显微镜（TEM）。这将包围一个纳米水族馆，里面的水含有微塑料和纳米塑料，以记录它们的运动、相互作用和动态聚集的电影，然后与理论相关联，为预测建模提供信息。要获得的基本理解与可持续性相关（例如，通过分离，收获和回收微塑料和纳米塑料的塑料升级回收），并可能适用于其他系统，如地质颗粒（砂，粘土）。除了跨学科的学生培训之外，这个项目的教育目标是为科学界提供以前无法获得的实验和建模数据，这些数据可能被应用于其他地理区域的不同微和纳米塑料。“水中的塑料”示范和讲座将推广到K-12学生和公众。由三名共同项目负责人组成的多元化团队还将积极鼓励妇女和少数民族从事科学事业。技术概述：这项实验模拟合作的研究目标是了解微观和纳米塑料在水中或在前所未有的纳米分辨率分离膜存在下的结构（例如，组成，大小，形状），胶体相互作用和聚集动力学之间的基本关系，从而实现有效的策略，以最大限度地减少微和纳米塑料在生态系统中的足迹。这种塑料颗粒的一般不规则性和高分散性导致在理解结构如何编码其性质和相行为（如絮凝成大聚集体或重沉积物）的原理方面存在知识空白，需要弥合这些知识空白以促进它们的去除。该研究项目旨在通过聚合物合成和表征、纳米成像和胶体模拟的综合努力来填补这一空白。通过使用低剂量液相透射电子显微镜（TEM）和扫描透射电子显微镜（STEM）的特殊显微镜套件，以纳米和毫秒分辨率实时成像液体中的微和纳米塑料，将获得新的认识。从(i)绘制模型和现实生活中的微塑料和纳米塑料的纳米级结构，以及这些结构如何与单粒子和成对水平上的胶体间相互作用电位相关联开始，本项目将继续（ii）阐明相互作用电位如何影响微塑料和纳米塑料的聚集动力学。最终将进行（iii）调查实际相关的环境变化对结构和相行为的影响，特别是在分离膜存在的情况下，以便了解基本的吸附和渗透动力学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARY:This collaborative project combines experiments and simulation to understand micro- and nanoplastics, which are tiny pieces of plastics invisible to human eyes that have been shown to be ubiquitously present in the food chain and the environment. Micro- and nanoplatics thus pose major concerns on their unpredictable impact on human health, ecosystem, and food. For example, micro-plastics, the larger-sized population of the plastic pieces, are found in freshwaters, saltwater fish, and air, at high concentrations and in various shapes such as fragments, foam, and pellets. Nanoplastics (smaller than 100 nanometers are found in water and could be particularly worrisome for human health because their sizes fall into a regime of small grains that living cells could incorporate. Micro- and nanoplastics cannot be thoroughly examined using the conventional toolkits based on statistical averaging. It is for these reasons that the research goal of this proposal is to introduce and use liquid-phase transmission electron microscopy (TEM). This will enclose a nano-aquarium with water containing micro- and nanoplastics to record movies of their motion, interactions, and aggregation on the fly, and then be correlated with theory to inform predictive modeling. The fundamental understanding to be obtained is relevant to sustainability (e.g., upcycling of plastics by separating, harvesting, and recycling of micro- and nanoplastics) and may apply to other systems such as geological grains (sands, clays). In addition to interdisciplinary student training, the educational goal of this project is to provide previously inaccessible experimental and modeling data to the scientific community that could potentially be applied to different micro- and nanoplastics in other geographic regions. "Plastics in water" demonstrations and lectures will be developed for outreach to K-12 students and the general public. The diverse team of three co-PIs will also actively encourage women and minorities to pursue scientific careers.TECHNICAL SUMMARY:The research goal of this experimental‒simulation collaboration is to understand the fundamental relationships among the structure (e.g., composition, size, shape), colloidal interactions, and aggregation dynamics of micro- and nanoplastics in water or in the presence of separation membranes at unprecedented nanometer resolution, thereby enabling efficient strategies to minimize the footprint of micro- and nanoplastics in the ecosystem. The generic irregularity and high dispersity of such plastic particles has resulted in a knowledge gap in understanding the principles of how structure encodes their properties and phase behaviors (such as flocculation into large aggregates or heavy sediments) which needs to be bridged in order to facilitate their removal. This research project aims to fill this gap through an integrated effort of polymer synthesis and characterization, nanoimaging and colloid simulation. New understanding will be obtained by using the special microscopy suite of low-dose liquid-phase transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) to image the micro- and nanoplastics in liquids at nanometer and millisecond resolutions in real time. Starting with (i) mapping the nanoscale structures of model and real-life micro- and nanoplastics and how the structures relate with the intercolloidal interaction potential on the single particle and pairwise level, this project will continue with (ii) elucidating how the interaction potential affects the aggregation dynamics of micro- and nanoplastics. It will ultimately be followed by (iii) investigating the effects of environmental variations of practical relevance on structure and phase behaviors, especially in the presence of separation membranes so as to understand the fundamental adsorption and penetration dynamics..This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.