(419a) Dynamics of Reversible Nanofluidic Water Filling inside Isolated Single-Walled Carbon Nanotubes

Isolated single-walled carbon nanotubes with diameters between 0.8 and 2.5 nm offer unprecedented opportunities to study fluid filling dynamics and phase behavior under nanoscale confinement. Within this size regime of so-called single digit nanopores, fluid phase boundaries are shifted dramatically, slip flow generates huge enhancements over Hagen-Poiseuille flow, and phase separation may be vastly different than in larger nanofluidic or microfluidic conduits, or in the bulk. Here, we demonstrate that Raman spectroscopy allows unambiguous assignment of carbon nanotubes as either empty or fluid-filled at arbitrary locations along their length. Ultralong carbon nanotubes are grown on solid substrates by chemical vapor deposition, segmented into multiple segments of identical diameter by photolithography or focused ion beam etching, and characterized by Raman spectroscopy. Through dynamic spectroscopic measurement, we observe the stochastic filling and emptying of isolated, single carbon nanotubes with second and micron resolution. Analysis of the dynamics of controlled water filling and emptying inside these conduits allows us to observe wide variation in vapor diffusion coefficient, liquid nucleation rate, and liquid growth rate with sub-Angstrom changes in the confining diameter. This work, and the detailed insight it gives to the dynamics of fluid diffusion and adsorption inside nanometer-scale pores, has implications for the design of membranes, study of flow through porous media, and engineering of adsorbent materials for energy and environmental applications.