Control over in-channel mesostructure orientation through AAM surface modification.

The synthesis of mesostructured silica from a tetrahydrofuran (THF) based sol-gel was carried out in the channels of an anodic alumina membrane (AAM) using the evaporation induced self-assembly (EISA) method. The effect of channel surface chemistry on the orientation of the in-channel hexagonal mesostructure was studied by treating the channel walls. A variety of channel-surface modifications have been performed, including oxygen plasma treatment, atomic layer deposition (ALD) of pure alumina, and deposition of a hydrophobic monolayer. The in-channel mesostructures were characterized using transmission electron microscopy (TEM) and energy filtered TEM (EFTEM). It was found that these modifications control the concentration of anions at the channel surfaces, and consequently the orientation of the hexagonal mesostructure. Namely, high anion concentration at the channel surface induces the formation of the desired vertically aligned columnar hexagonal phase. A model to understand the effect of anions at the channel wall on the competition between mesostructure phase transformation and silica condensation is proposed. Finally, this study demonstrates that by judiciously modifying the chemistry at the channel walls the formation of desired orientations can be induced.

Direct quantification of ordering at a solid-liquid interface using aberration corrected transmission electron microscopy.

We have used aberration corrected in situ transmission electron microscopy to study the interface between liquid Al and different sapphire facet planes, including quantitative analysis of the degree of residual contrast delocalization, ensuring that the experimental contrast perturbations can be associated with density perturbations in the liquid. The results confirm that the liquid is ordered at the interface, and the degree of ordering varies as a function of the sapphire facet planes, with a decreasing degree of order according to (0006) >(1210) >(1012) ≥ (1014).