Electron microscope visualization of multiphase fluids contained in closed carbon nanotubes

Aqueous multiphase fluids trapped in closed multiwall carbon nanotubes are visualized with high resolution using transmission electron microscopy (TEM). The hydrothermally synthesized nanotubes have inner diameter of 70 nm and wall thickness 20 nm, on average. The nanotubes are hydrophilic due to oxygen groups attached on their wall surfaces. Segregated liquid inclusions contained in the nanotubes under high pressure can be mobilized by heating. A resistive heating stage is utilized to heat a thin membrane inside a nanotube, causing the membrane to evaporate slowly and eventually pinch off. Focused electron beam heating is employed as a second means of thermal stimulation, which results in localized heating. With the latter method, gas/liquid interface motion is observed inside the thin channel of a carbon nanotube. Experiments like the ones presented herein may help understand the dynamics of fluids contained in nanoscale channel