Solute particle near a nanopore: influence of size and surface properties on the solvent-mediated forces

TL;DR

This study uses classical density functional theory to analyze how nanoparticle size and surface properties influence solvent-mediated forces near nanopores, providing insights into particle-pore interactions and phase behavior.

Contribution

It introduces a comprehensive model combining density functional theory and a capillary approach to predict nanoparticle forces considering geometry, hydrophobicity, and electrostatics.

Findings

Depletion forces depend on nanoparticle size and surface hydrophobicity.

A phase diagram predicts nanoparticle entry or rejection based on surface and electrostatic properties.

The model accounts for pore geometry and liquid filling states.

Abstract

Nanoscopic pores are used in various systems to attract nanoparticles. In general the behaviour is a result of two types of interactions: the material specific affinity and the solvent-mediated influence also called the depletion force. The latter is more universal but also much more complex to understand since it requires modeling both the nanoparticle and the solvent. Here, we employed classical density functional theory to determine the forces acting on a nanoparticle near a nanoscopic pore as a function of its hydrophobicity and its size. A simple capillary model is constructed to predict those depletion forces for various surface properties. For a nanoscopic pore, complexity arises from both the specific geometry and the fact that hydrophobic pores are not necessarily filled with liquid. Taking all of these effects into account and including electrostatic effects, we establish a phase diagram describing the entrance and the rejection of the nanoparticle from the pore.