Seminar:

 Due to the size- and shape-dependent properties, nanomaterials such as nanoparticles have been successfully fabricated for multi-dimensional (D) ordered assemblies for the development of ‘artificial solids’ (e.g., metamaterials) with potential applications in nanoelectronics and nanophotonics. Synthesis and assembly of nanomaterials have been relied on specific chemical or physical forces such as van der Waals interactions, dipole-dipole interaction, chemical reactions, and DNA-templating, etc. In this presentation, I will discuss our recent discovery that an external stress can be utilized to engineer nanomaterial assemblies and to fabricate new nanomaterial architectures without relying on these specific forces. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle arrays can be manipulated to reversibly shrink, allowing fine-tuning of interparticle separation distance to interrogate collective physical properties, such as surface plasmon resonance. Moreover, beyond a threshold pressure, nanoparticles are forced to contact and sinter, forming new classes of chemically and mechanically stable 1-3D nanostructures that cannot be manufactured by current top-down or bottom-up methods. Depending on the orientation of the initial nanoparticle arrays, 1-3D ordered nanostructures (Au, Ag, CdSe, etc) including nanorod, nanowire, nanosheet, and nanoporous network can be fabricated. Guided by computational simulations, we are able to rationalize the necessary stress for predictable nanostructures. Exerting stress-dependent control over the structure and property provides a unique and robust system to understand collective chemical and physical characteristics of nanomaterials.  This method mimics embossing and imprinting manufacturing processes and opens exciting new avenues for large-scale fabrication of novel active nanomaterials during applying and releasing of stress.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.