Engineering of Colloidal Nanocrystals for Multifunctional Coatings

While progress in physical deposition techniques, such as sputtering and CVD, has allowed thin film deposition techniques to generally keep pace with the performance requirements of typical optical and semiconductor applications, this performance comes at a significant cost, impacting budget, logistics, and environmental, safety, and health areas. Development of solution processing methods for the synthesis of functional inorganic materials have opened up new avenues to achieve enhanced and/or novel properties in these materials. Among significant methods, self-assembly techniques are one of the powerful, efficient, and cost effective methods to the synthesis of nanostructured films. Using these techniques and their combination with top-down fabrication processes such as lithography, materials with hierarchical feature can be produced with form and function in multiple length scales. Here our recent progress in development of engineered multifunctional nanostructured coatings using self-assembly techniques will be presented. An interfacial self-assembly process is developed to synthesize multifunctional colloidal nanocrystals and to assemble them into ordered, three-dimensional, nanoparticle films. Through control of structural parameters of nanocrystal assemblies, we are able to fabricate uniform reflective optical coatings. Quarter wave stacking of self-assembled nanocrystal films are developed for near infrared reflectors, which overcomes the harsh conditions from conventional processing (CVD, sputtering, etc) with improved functionality. Reflectivity studies show high and reproducible reflectivity over controlled wavelength windows (1-12µm). Theory modeling shows very good consistency with experimental results.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.