Solvent Mediated Assembly of Nanoparticles Confined in Mesoporous Alumina

TL;DR

This study demonstrates reversible solvent-controlled self-assembly of gold nanoparticles within mesoporous alumina, revealing insights into the structural evolution, hysteresis effects, and capillary filling behavior in confined nanostructures.

Contribution

It introduces a method to reversibly control nanoparticle assembly in mesoporous templates using solvent regulation, with detailed in situ analysis of structural and thermodynamic properties.

Findings

Nanoparticles form cylindrical monolayers within pores.

Assembly is reversible with solvent removal and addition.

Capillary filling transition is significantly shifted by nanoparticles.

Abstract

The controlled self-assembly of thiol stabilized gold nanocrystals in a mediating solvent and confined within mesoporous alumina was probed in situ with small angle x-ray scattering. The evolution of the self-assembly process was controlled reversibly via regulated changes in the amount of solvent condensed from an undersaturated vapor. Analysis indicated that the nanoparticles self-assembled into cylindrical monolayers within the porous template. Nanoparticle nearest-neighbor separation within the monolayer increased and the ordering decreased with the controlled addition of solvent. The process was reversible with the removal of solvent. Isotropic clusters of nanoparticles were also observed to form temporarily during desorption of the liquid solvent and disappeared upon complete removal of liquid. Measurements of the absorption and desorption of the solvent showed strong hysteresis upon thermal cycling. In addition, the capillary filling transition for the solvent in the nanoparticle-doped pores was shifted to larger chemical potential, relative to the liquid/vapor coexistence, by a factor of 4 as compared to the expected value for the same system without nanoparticles.