Investigation of Freestanding Nanoparticle Sheets

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。技术摘要：该项目研究一种新型的独立超薄薄片，由紧密堆积的金属纳米颗粒层组成，每个颗粒被一层短有机分子的薄壳包围，这些有机分子充当颗粒间的间隔物。这些片材可以在从溶液到固体基板的单一加工步骤中自组装，可以覆盖基板上直径数百到数千个纳米颗粒的开口，并显示出非凡的机械强度和坚固性，包括几十亿卡的杨氏S模数。作为单分子层，这些薄片是可以由纳米颗粒构建块制造的最薄的结构。该项目利用了这样一个事实，即纳米颗粒组件的性质可以通过改变单个颗粒的大小、形状和类型以及独立地通过改变间隔物分子来调节。独立的薄片使研究大型纳米级积木组件的独特材料特性成为可能，而不受衬底的干扰，同时允许通过一系列探针(如透射电子或扫描探针显微镜)直接实验访问各个积木本身。将系统的实验和弹性响应的模拟相结合，这项研究解决了一个仍然没有答案的关键问题，即产生超薄纳米颗粒片材观察到的高抗拉强度的详细机制。此外，还探索了新的方向，如通过合适的粒子形状引入机械各向异性的可能性，通过使用磁性粒子进一步调谐的可能性，以及将薄片作为新型谐振器的可行性。非技术摘要：纳米粒子自组装为下一代材料的设计提供了特殊的机会。这个项目的重点是一种新的超薄薄板，由单层金属纳米颗粒制成。在这种超薄的极限下，薄片将极大的灵活性与非凡的机械强度结合在一起。这种组合使设计新型涂层以及涉及1000万或更多颗粒的自由悬浮单层膜成为可能。该项目还提供了一个将研究与培训和外联相结合的天然平台。它将培训一名博士后和一名研究生掌握重要的纳米科学知识，并向本科生介绍前沿科学。一个独特的组成部分是一套外联活动，其中包括与一家大型科学博物馆一起开发和制作小规模动手活动的原型。

This Award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). TECHNICAL SUMMARY:This project investigates a new class of free-standing, ultrathin sheets comprised of layers of close-packed metallic nanoparticles, each particle surrounded by a thin shell of short organic molecules that act as inter-particle spacers. The sheets can be self-assembled in a single processing step from solution onto a solid substrate, can drape themselves over open holes in the substrate that are hundreds to thousands of nanoparticles across, and exhibit remarkable mechanical strength and robustness, including Young?s moduli of several GigaPascal. As monolayers these sheets are the thinnest structures that can be fabricated from nanoparticle building blocks. The project exploits the fact that the properties of nanoparticle assemblies can be tuned by varying the size, shape and type of the individual particles and, independently, by varying the spacer molecules. Free-standing sheets make it possible to investigate the unique material properties of large assemblies of nanoscale building blocks without interference from a substrate, and at the same time allow for direct experimental access, via a range of probes such as transmission electron or scanning probe microscopies, to the individual building blocks themselves. Combining systematic experiments with simulations of the elastic response, the research addresses a key issue that is still unanswered, namely the detailed mechanisms giving rise to the observed large tensile strength of ultrathin nanoparticle sheets. In addition, new directions are pursued, such as the possibility of introducing mechanical anisotropy through suitable particle shapes, further tunability through the use of magnetic particles, and the feasibility of the sheets as novel resonators.NON-TECHNICAL SUMMARY:Nanoparticle self-assembly offers special opportunities for the design of next-generation materials. This project focuses on a new class of ultra-thin sheets, fabricated from single layers of metal nanoparticles. In this ultrathin limit, the sheets combine extreme flexibility with unusual mechanical strength. This combination makes it possible to design novel coatings as well as freely suspended monolayer membranes involving 10 million or more particles. The project also provides a natural platform for integrating research with training and outreach. It will train one postdoc and one graduate student in vital nanoscience know-how, and introduce undergraduates to forefront science. A unique component is a set of outreach activities that include the development and prototyping of small-scale, hands-on activities with a major science museum.