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

点击翻译按钮获取中文摘要

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.