The NSF BRIGE proposal is a 2-year seed-funding program designed to give new PIs the opportunity to obtain preliminary results to build up future proposals. This NSF BRIGE proposal aims to lay the groundwork for a NSF CAREER proposal that experimentally investigates the phononic crystal properties nanocrystal superlattices. The goals of this 2-year proposal are to: (i) Measure the thermal conductivity of colloidal nanocrystal superlattices. (ii) Simulate the phononic crystal properties of these superlattices. (iii) Obtain preliminary phonon spectroscopy results on these superlattices. (iv) Outreach to the community via the Science is Fun program in the CSSS and other activities Colloidal nanocrystals are inorganic nanoparticles with organic ligands on their surface. These nanocrystals can self-assemble into periodic arrays using the van der Waals interactions between the ligand molecules. In analogy to the atomic lattice of a crystal, these nanocrystal assemblies are termed nanocrystal superlattices. These superlattices are best known for their optical and electronic properties, however their thermal properties are unexplored. The PI believes that these superlattices will be a new class of extremely thermally-insulating materials. In addition, these superlattices will also be a new class of phononic crystal with unprecedented high frequency phonon band gaps. The low thermal conductivity of these superlattices should arise due to: (i) a large interfacial density, (ii) a large acoustic mismatch between the inorganic nanoparticle cores and ligand matrix, and (iii) phonon filtering resulting from the phononic crystal nature of the superlattice. Phononic crystals are artificially structured materials with periodic variations in acoustic impedance. This periodicity results in a phononic band gap, which forbids the propagation of elastic waves in a particular energy range. The phononic crystal is analogous to the well-known photonic crystal, which uses periodic variations in refractive index to create a photonic band gap. Fundamentally the phononic band gap arises from wave interference, which requires that the crystals lattice constant be comparable to the phonon wavelength. Due to the small ~10 nm periodicity of these superlattices, the phononic band gap should be in the 100+ GHz range, which is two orders of magnitude hire than any other three dimensional phononic crystal.
|Effective start/end date||9/1/12 → 8/31/15|
- National Science Foundation (NSF): $175,000.00