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：该项目研究了一类新的独立式，由紧密堆积的金属纳米颗粒层组成的纳米片，每个颗粒被一层薄壳短有机分子包围，作为颗粒间的间隔物。片材可以在单个处理步骤中从溶液自组装到固体基底上，可以将其自身覆盖在基底中的开孔上，所述开孔是数百至数千个纳米颗粒，并且表现出显着的机械强度和鲁棒性，包括Young？s模数为几千兆帕斯卡。作为单层，这些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，即纳米颗粒组装体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分子来调节。独立式片材使得研究纳米级构建块的大型组件的独特材料特性而不受衬底的干扰成为可能，并且同时允许通过一系列探针（例如透射电子或扫描探针显微镜）直接实验访问单个构建块本身。结合系统的实验与弹性响应的模拟，该研究解决了一个仍然没有答案的关键问题，即引起所观察到的纳米颗粒片的大拉伸强度的详细机制。此外，还在探索新的方向，例如通过合适的颗粒形状引入机械各向异性的可能性，通过使用磁性颗粒进一步的可调谐性，以及片材作为新型谐振器的可行性。非技术总结：纳米颗粒自组装为下一代材料的设计提供了特殊的机会。该项目的重点是一类新的超薄板材，由单层金属纳米颗粒制成。在这种极限情况下，板材联合收割机具有极高的柔韧性和非同寻常的机械强度。这种组合使得设计新颖的涂层以及涉及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自然的平台，将研究与培训和外联结合起来。它将培养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推广活动，包括与一个主要的科学博物馆一起开发和原型化小规模的实践活动。

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.