2 research outputs found
Gold Nanoparticle Layers on Polystyrene Microspheres of Controlled Structure and Electrokinetic Properties
Formation
of positively charged gold nanoparticle layers on polystyrene
microparticles (PSMs600) was studied using the electrokinetic and
the concentration depletion methods based on atomic force microscopy
(AFM) and scanning electron microscopy (SEM) imaging. Primarily, the
dependence of electrophoretic mobility of microparticles on the gold
nanoparticle concentration in the suspension was measured. These results
were quantitatively interpreted in terms of the three-dimensional
electrokinetic model. This allowed to derive a formula for calculating
the coverage of nanoparticles under in situ conditions whose validity
was confirmed by direct SEM imaging of deposited gold nanoparticles
(AuNPs). Additionally, the maximum coverage of gold nanoparticles
for various ionic strengths was determined using a concentration depletion
method based on AFM imaging of residual particles deposited on the
silica substrate. The maximum coverage increased with ionic strength
attaining a value of 0.35 for the ionic strength of 3 × 10<sup>–3</sup> M. This effect was attributed to the decreasing range
of lateral electrostatic interactions among deposited particles. The
electrokinetic properties of the gold nanoparticle layers were also
evaluated in pH cycling experiments that confirmed their stability.
Beyond significance to basic science, the new data acquired in this
work confirm the feasibility of preparing gold nanoparticle layers
on polymer microparticles characterized by a controlled structure,
coverage, and electrokinetic properties
Monolayers of Poly(styrene/α-<i>tert</i>-butoxy-ω-vinylbenzyl-polyglycidol) Microparticles Formed by Controlled Self-Assembly with Potential Application as Protein-Repelling Substrates
The kinetics of the self-assembly
of poly(styrene/α-<i>tert</i>-butoxy-ω-vinylbenzyl-polyglycidol)
microparticles
on poly(allylamine hydrochloride)-derivatized silicon/silica substrate
was determined by direct AFM imaging and streaming potential (SP)
measurements. The kinetic runs acquired under diffusion-controlled
transport were quantitatively interpreted in terms of the extended
random sequential adsorption (RSA) model. This allowed confirmation
of a core/shell morphology of the microparticles. The polyglycidol-rich
shell of thickness equal to 25 nm exhibited a fuzzy structure that
enabled penetration of particles into each other resulting in high
coverage inaccessible for ordinary microparticles. The SP measurements
interpreted by using the 3D electrokinetic model confirmed this microparticle
structure. Additionally, the acid–base characteristics of the
microparticle monolayers were determined for a broad pH range. By
using the streaming potential measurements, human serum albumin (HSA)
adsorption on the microparticle monolayers was investigated under
in situ conditions. It was confirmed that the protein adsorption was
considerably lower than for the reference case of bare silicon/silica
substrate under the same physicochemical conditions. This effect was
attributed to the presence of the shell diminishing the protein/microparticle
physical interactions