Adsorption Dynamics of Surface-Modified Silica Nanoparticles at Solid–Liquid Interfaces

Understanding the adsorption dynamics of nanoparticles
at solid–liquid
interfaces is of paramount importance to engineer nanoparticles for
a variety of applications. The nanoparticle surface chemistry is significant
for controlling the adsorption dynamics. This study aimed to experimentally
examine the adsorption of surface-modified round-shaped silica nanoparticles
(with an average diameter of 12 nm), grafted with hydrophobic (propyl
chains) and/or hydrophilic (polyethylene glycol chains) agents, at
an aqueous solution–silica interface with spherical soda-lime
glass beads (diameter of 3 mm) being used as adsorbents. While no
measurable adsorption was observed for solely hydrophobic or hydrophilic
nanoparticles, a considerable level of adsorption was detected for
nanoparticles comprising both hydrophobic and hydrophilic agents.
Various kinetic models were employed to model the adsorption dynamics
of the responsive nanoparticles. The results demonstrated that the
mixed diffusion-kinetics models could predict the dynamics better
than the adsorption diffusion models, indicating that the dynamics
is controlled by a combination of liquid film diffusion, intra-particle
diffusion, and mass action. Additionally, the adsorption of the surface-modified
silica nanoparticles onto a mineral silica surface was examined using
molecular dynamics simulations. The interaction energy for nanoparticles
comprising both hydrophobic and hydrophilic agents was evaluated to
be more favorable than that of solely hydrophobic or hydrophilic nanoparticles.