Molecular Foundry Seminar

"Nanoparticle Stress Sensors and the Effects of Pressure and Size Scale on Atomic Structure"

Kristie Koski, Arizona State University,

Tuesday, December 8th at 1:30 pm, Room 67-3111

Abstract:

At high pressures and nanometer scales, material properties can be completely different from the properties exhibited under more ordinary conditions. Material behavior at high pressures is often uniquely influenced by the nanoparticle morphology. For example, silver noble metal nanoparticles <10 nm in diameter often possess multiply twinned grain structures allowing them to adopt shapes and atomic structures not observed in bulk materials. I will present experimental evidence that, under hydrostatic pressures up to 10 GPa, such particles exhibit a reversible, linear, pressure-dependent rhombohedral distortion unlike anything that normally occurs in bulk silver. Further, now that this behavior has been calibrated as a function of pressure, I will show how the same silver nanoparticles encapsulated inside hollow metal oxide nanospheres can act as a probe of the pressure of tiny volumes of fluid inside the hollow spheres using x-ray diffraction and diamond anvil cell techniques. Since the pressure outside the spheres is also measured, we can determine the pressure gradient across the
few-nanometer shell thickness providing unique information about the high-pressure mechanical behavior of hollow nanoshells. Finally, I will show examples of how nanoparticles with unusual morphologies can probe both the hydrostatic and non-hydrostatic environments in high-pressure experiments.