Mechanical Properties of Freestanding Nanoparticle Sheets

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TECHNICAL SUMMARY:The project investigates a new class of ultrathin sheets that are self-assembled from metal nanoparticles, each particle being surrounded by a thin shell of short organic molecules that act as inter-particle spacers. As close-packed monolayers these sheets are the thinnest structures that can be fabricated from nanoparticle building blocks. The sheets exhibit remarkable mechanical strength and robustness, including Young's moduli of several GigaPascal, and can be draped over openings hundreds to thousands of particles wide. The resulting freestanding membranes provide special opportunities for investigating nanomechanical properties, making it possible to investigate large assemblies of nanoscale building blocks without interference from a substrate, while at the same time allowing for direct experimental access, via a range of probes such as electron or scanning probe microscopies, to the individual building blocks themselves. Combining systematic experiments with simulations of the elastic response, the project addresses questions that are of fundamental relevance also for systems with atoms as building blocks, such as how the overall mechanical response is affected by defects in the particle arrangement. Additional directions to be pursued include assessing the feasibility of using the sheets as mechanical resonators and sensors in the MHz range, and the possibility of folding the nanoparticle sheets into three-dimensional structures. The project will train one postdoc and one graduate student in vital nanoscience know-how. A set of outreach activities includes the development and prototyping of hands-on activities with a major science museum.NON-TECHNICAL SUMMARY:Nanoparticle self-assembly offers special opportunities for the design of next-generation materials. This project investigates a new class of ultrathin sheets, assembled from metal nanoparticles. As one-particle-thin layers, these sheets are the thinnest structures that can be fabricated with nanoparticles. A special feature is that they combine extreme flexibility with unusual mechanical strength. This combination makes it possible to design novel coatings as well as new types of self-assembled, nanomechanical resonators and sensors. The project provides a natural platform for integrating research with education and outreach. It will train one postdoc and one graduate student in vital nanoscience know-how, and introduce undergraduates to forefront science. A special component is a set of outreach activities that include the development and prototyping of hands-on activities with a nearby major science museum.