Solidified Fillings of Nanopores

TL;DR

This paper investigates how various gases and molecules crystallize within nanopores of silica glass, revealing adaptations in their structure due to confined geometries, including stacking faults and modified layering.

Contribution

It provides detailed diffraction patterns and insights into the structural adaptations of different molecules solidified in nanopores, highlighting the influence of confinement on crystallization.

Findings

He, Ar, and certain molecules develop stacking faults in nanopores.

Chain-like molecules show different layering behavior under confinement.

Structural principles of crystallization are altered in restricted geometries.

Abstract

We present a selection of x-ray and neutron diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chain-like n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.