Phase transitions of low-density amorphous ice confined at nanotube interfaces studied using Cryo-EM*

Recent interest in confinement effects on water touches on diverse areas, ranging from chemical sensing and filtration to modeling of celestial water. Many studies report changes in water behavior when constrained inside carbon nanotubes (CNT) and/or boron nitride nanotubes (BNNT) such as straining of bonds, variance in phases, and transport properties. Our goal is to quantify the dynamics of water at the BNNT interface using in situ characterization at cryogenic temperatures in an aberration-corrected environmental scanning transmission electron microscope (ESTEM) equipped with a K-2 camera and Raman spectrometer. Water is hyper-quenched to liquid nitrogen temperatures below 100 K to allow for the formation of low density amorphous (LDA) ice, a phase of ice similar in structure to liquid water. High resolution images of interactions are then acquired while preserving the overall integrity of the original water structure. Furthermore, Raman spectroscopy was employed to measure the vibrational modes of ice to characterize the phase transitions. We will present a comparison of the structural evolutions of LDA ice with and without the presence of BNNT. Confinement effects of LDA ice inside nanotubes will be discussed.