Colloidal Stability of Self-Assembled Monolayer-Coated
Gold Nanoparticles: The Effects of Surface Compositional and Structural
Heterogeneity
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Abstract
Surface
heterogeneity plays an important role in controlling colloidal
phenomena. This study investigated the self-aggregation and bacterial
adsorption of self-assembled monolayer coated gold nanoparticles (AuNPs)
with different surface compositional and structural heterogeneity.
Evaluation was performed on AuNPs coated with (1) one ligand with
charged terminals (MUS), (2) two homogeneously distributed ligands
with respectively charged and nonpolar terminals (brOT) and (3) two
ligands with respectively charged and nonpolar terminals with stripe-like
distribution (OT). The brOT particles have less negative electrophoretic
mobility (EPM) values, smaller critical coagulation concentration
(CCC) and larger adsorption rate on <i>Escherichia coli</i> than that of AuNPs with homogeneously charged groups, in good agreement
with DLVO predictions. Although the ligand composition on the surface
of AuNPs is the same, OT particles have less negative EPM values and
faster rate of bacterial adsorption, but much larger CCC compared
to brOT. The deviation of OT particles from brOT and MUS in their
self-aggregation behavior reflects the effects of surface heterogeneity
on electrical double layer structures at the interface. Results from
the present study demonstrated that, besides chemical composition,
organization of ligands on particle surface is important in determining
their colloidal stability