CAREER: Imaging and Understanding the Kinetic Pathways in Shape-Anisotropic Nanoparticle Self-Assembly

非技术摘要：材料科学的一个新兴主题是理解和设计表现出生物体特征的人工材料：适应性和进化的功能行为。例子包括图案化的超小天线，其在不同的太阳位置上调制局部电磁场强度，或汽车“皮肤”，其优化车辆在不同环境中的空气动力学。在固态和材料化学计划的支持下，主要研究者的NSF CAREER赠款专注于破译纳米尺寸的构建块自组织和重组成这种自适应材料的规则。选择这些构建块是因为它们具有微型化的独特潜力，以及它们组织成的结构所决定的集体性质。该项目的关键创新有两个方面。首先，一种新型的成像工具将被用来跟踪和录像的积木运动的飞行在原子分辨率。其次，将分析所获得的运动以解释这些构建块之间的串扰。所获得的基本理解也可以应用于由微小基本物体组成的其他系统，例如对人类健康至关重要的生物分子，或者创造可以实现廉价和清洁的可再生能源的新材料。该项目为本科生和研究生提供培训。一个“三M实验室”，包括模块化实验室演示，一个移动的游戏应用程序，和电影被用作一个平台，广泛传播给公众。技术摘要：主要研究者的长期目标是将无生命的材料转化为有生命的，能够重新配置其结构和属性的需求。从纳米级构建块设计可重构材料的关键挑战在于理解它们自组装的动力学途径。这些途径定义了构建块如何相互作用并组装成靶向结构，即构建块纳米级相互作用-靶向结构关系。然而，动力学途径与构建块如何在溶剂中连续扩散和翻滚相关，这在性质上是时空变化的和纳米级的。因此，充分了解这些途径需要具有高时空分辨率的真实空间，原位表征，这是现有的非原位和集成方法所不能提供的。因此，本CAREER提案的研究目标是解决这一挑战，并量化各向异性金纳米颗粒（NP）模型系统中自组装和结构重构的相互作用和动力学途径。所提出的方法是联合收割机的紧急液相透射电子显微镜（TEM）与自动电影分析方法在PI的小组开发的量化NP自组装的动力学。具体而言，本研究将（i）使用具有纳米和毫秒分辨率的低剂量液相TEM捕获代表性各向异性NP的自组装轨迹，（ii）基于这些轨迹的高通量统计分析，从这些轨迹中提取迄今为止的物理参数，例如NP-NP相互作用势和自组装动力学途径，以及（iii）量化不同刺激，例如温度和溶剂极性，影响具有可重构聚合物冠的NP系统中的相变动力学，从而朝向完全自下而上适应其结构和功能的系统移动。该奖项反映了NSF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 Abstract:An emerging theme in materials science is to understand and design artificial materials exhibiting the features of living organisms: adaptive and evolving functional behaviors. Examples include patterned ultra-small antennas that modulate local electromagnetic field strengths upon different sun positions, or automotive "skins" that optimize the aerodynamics of vehicles in varying environments. With support from the Solid State and Materials Chemistry program, the Principal Investigator's NSF CAREER grant is focused on deciphering the rules upon which nanometer-sized building blocks self-organize and reorganize into such adaptive materials. These building blocks are chosen due to the unique potential for miniaturization and the collective properties determined by the structures they organize into. The key enabling innovations of this project are two-fold. First, a novel imaging tool will be used to trace and videotape the building block motions on the fly at up to atomic resolution. Second, the obtained motions will be analyzed to interpret the crosstalk among these building blocks. The obtained fundamental understanding can also be applied to other systems composed of tiny elementary objects such as biological molecules which are critical for human health, or to create new materials that can achieve cheap and clean renewable energy. The project provides training to both undergraduate and graduate students. A "tri-M lab" including Modular lab demos, a Mobile game app, and Movies is utilized as a platform for broad dissemination to the general public.Technical Abstract:The Principal Investigator's long-term goal is to transmute inanimate materials into animate ones, capable of reconfiguring their structure and property on demand. The key challenge in designing reconfigurable materials from nanoscale building blocks lies in understanding the kinetic pathways of their self-assembly. These pathways define how building blocks interact and assemble into targeted structures, i.e. the building block nanoscale interaction-targeted structure relationship. However, the kinetic pathways are associated with how building blocks continuously diffuse and tumble in a solvent, which is both spatiotemporally varying and nanoscopic in nature. Thus, fully understanding these pathways requires real-space, in-situ characterization with high spatiotemporal resolution, which is not offered by existing ex-situ and ensemble methods. The research objective of this CAREER proposal is thus to address this challenge and to quantify the interactions and kinetic pathways governing self-assembly and structural reconfiguration in model systems of anisotropic gold nanoparticles (NPs). The proposed approach is to combine the emergent liquid-phase transmission electron microscopy (TEM) with automated movie analysis methods developed in the PI's group to quantify the dynamics of NP self-assembly. Specifically, this research will (i) capture the self-assembly trajectories of representative anisotropic NPs using low-dose liquid-phase TEM with nanometer and millisecond resolution, (ii) extract from these trajectories hitherto physical parameters, such as NP-NP interaction potentials and self-assembly kinetic pathways, based on high-throughput statistical analysis of these trajectories, and (iii) quantify how diverse stimuli, such as temperature and solvent polarity, affect phase transition dynamics in systems of NPs with reconfigurable polymer coronas, moving towards systems that adapt their structure and functions entirely from the bottom-up. This approach will help establish a quantitative building block-nanoscale interaction-targeted structure relationship for predictive materials design.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.