Department of Applied Physics and Materials Science - Materials Science

Materials Science Research Lecture

Wednesday February 22, 2023 4:00 PM

Nanoconfined fluids in low-dimensional solid state systems: recent advances & perspective

Speaker: Matthias Kuehne, Physics, Brown University
Location: Noyes 147 (J. Holmes Sturdivant Lecture Hall)


Recent interest in one-dimensionally confined fluids, where confinement approaches molecular dimensions, has demonstrated exceptionally high fluxes from slip flow and large distortions of fluid phase boundaries. Predicting such phenomena for a given conduit dimension has been confounded by a dearth of fundamental thermodynamic measurements and analysis as a function of confinement diameter. I this talk, I present recent advances that allow us to interrogate multiple segments of the same, isolated carbon nanotube (CNT) by micro-Raman spectroscopy as a versatile platform for investigating nano-confined fluids. We further demonstrate the measurement and analysis of thermally induced, reversible fluid isobars in isolated carbon nanotubes (CNTs), spanning 0.9 to 3.3 nm in diameter. Raman radial breathing(-like) vibrational modes (RBLMs) serve as fluid sensors, which we study as a function of local CNT temperature by varying the laser excitation power and using the Raman G band shift as built-in thermometer. We disambiguate interior and exterior fluids by comparing filled and empty segments of the same CNT, as well as by a detailed elastic shell model analysis of double-walled CNTs using a Buckingham potential. The analysis allows for precise determination and study of the fluid coupling parameter which is a function of the fluid density and strength of the fluid/wall interaction, in agreement with molecular dynamics simulations. The thermodynamic analysis of isobars measured in >25 CNTs under various environmental conditions reveals a discontinuous trend with diameter for the enthalpy of adsorption of interior water as opposed to the one of an exterior fluid phase. The distinct thermodynamic properties observed in conduits differing in size by less than 2 Å suggest unique flow and fluid property regimes at precise molecular confinement diameters. Our work sets forth a new and reliable approach for studying phase change of different fluids in large numbers of isolated single digit nanopores that may inform the refinement of fluid force fields.

More about the Speaker:

Matthias Kuehne recently joined Brown University as an assistant professor of physics, following postdoctoral work in the group of Michael Strano at MIT. Matthias did his doctoral studies at the Max Planck Institute for Solid State Research in Stuttgart, Germany. His group at Brown University investigates fluidic, ionic, and electronic properties of low-dimensional materials and devices.

Series Materials Research Lecture Series

Contact: Jennifer Blankenship