CAREER: Understanding Nanoparticle Adhesion to Guide the Surface Engineering of Supporting Structures

这项教师早期职业发展（Career）计划资助支持金属纳米颗粒的基础研究，金属纳米颗粒是一类直径可小至10个原子的材料，广泛用于催化等先进技术。使用这些纳米颗粒面临的一个关键挑战是，它们会因颗粒粗化而失去功能；一种平均粒径随着时间的推移而增大，从而降低其性能的现象。这项资助旨在减轻这种粗糙化，从而提高性能，从而推进知识，以保持这些关键材料技术的全球领先地位，并帮助国家繁荣的发展。通过使用稳定支撑材料来对抗粗化，但目前这些材料大多是通过耗时且昂贵的试错测试找到的。本研究旨在通过阐明颗粒粗化对支撑表面结构的依赖关系，从而实现新的、更好的稳定支撑材料的合理设计。该基金开发了新的方法来测量纳米颗粒在各种条件下在明确定义的表面上的附着和稳定性，从而使表面的合理工程能够优化纳米颗粒的性能和寿命。最终，更稳定的纳米粒子将导致人类和环境健康、清洁能源和更高效的制造方面的重大进步。教育活动包括与匹兹堡大学教育学院和当地一所小学合作，为6至8年级的学生创建并在全国范围内传播表面工程课程单元，并为教师提供专业发展培训模块。纳米颗粒的粗化主要有原子扩散（奥斯特瓦尔德成熟）和颗粒迁移聚并两种机制；两者都被假设成指数依赖于纳米颗粒与其衬底之间的粘附强度。该研究将利用透射电子显微镜的原位粘附测试来研究这种联系，从而能够直接测量粘附能，同时对单个纳米颗粒进行亚纳米级材料表征。研究目标是建立将表面化学、结晶度和形貌与纳米颗粒粘附和颗粒粗化率联系起来的结构-功能关系。中心假设是基材表面可以合理修饰以调整附着力，从而控制颗粒粗化的速度。所开发的知识将提高金属纳米颗粒在氧化物载体上的应用性能，特别是：用于检测污染物和作为疾病生物传感器的等离子体传感器；改进太阳能转换的纳米光子学；多相催化，它为美国国民生产总值的三分之一的生产链做出了贡献。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。

This Faculty Early Career Development (CAREER) Program grant supports fundamental research on metal nanoparticles, a class of materials that can be as small as 10 atoms in diameter and are widely used in advanced technologies such as catalysis. A critical challenge in the use of these nanoparticles is their loss of functionality via particle coarsening; a phenomenon in which the average particle size increases over time, thus degrading their performance. This grant seeks to mitigate such coarsening allowing for improved performance, thus advance knowledge to sustain global leadership in these critical materials technologies and aid in the development of national prosperity. Coarsening is countered through the use of stabilizing support materials, but at present these materials are mostly found through time-consuming and costly trial-and-error testing. The present research seeks to enable the rational design of new and better stabilizing support materials by elucidating the dependence of particle coarsening on the supporting surface structure. The grant develops new approaches to measure the attachment and stability of nanoparticles on well-defined surfaces under various conditions, enabling the rational engineering of surfaces to optimize the performance and lifetime of the nanoparticles. Ultimately, more stable nanoparticles will lead to significant advances in human and environmental health, clean energy, and more efficient manufacturing. Educational activities include collaborates with the University of Pittsburgh's School of Education and a local elementary school to create and nationally disseminate surface engineering focused curricular units for 6th-to-8th-grade students and professional development training modules for teachers. Nanoparticle coarsening occurs by two mechanisms, atomic diffusion (Ostwald ripening) and particle migration and coalescence; both are hypothesized to depend exponentially on the strength of adhesion between the nanoparticle and its substrate. The research will investigate this link using in situ adhesion tests in a transmission electron microscope, thus enabling direct measurements of adhesion energy with simultaneous sub-nm-scale materials characterization for individual nanoparticles. The research objective is to establish structure-function relationships that link surface chemistry, crystallinity, and morphology to nanoparticle adhesion and the rate of particle coarsening. The central hypothesis is that the substrate surface can be rationally modified to tune adhesion, and thus control the rate of particle coarsening. The knowledge developed will improve performance in applications of metal nanoparticles on oxide supports, specifically: plasmonic sensors for detection of pollutants and as biosensors for disease; nanophotonics for improved conversion of solar energy; and heterogeneous catalysis, which contributes to the production chain of one-third of the US gross national product.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.