Polyvinylpyrrolidone Molecular
Weight Controls Silica
Shell Thickness on Au Nanoparticles with Diglycerylsilane as Precursor
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Abstract
Several strategies have been described for the preparation
of silica-encapsulated
gold nanoparticles (SiO<sub>2</sub>–AuNP), which typically
suffer from an initial interface between gold and silica that is difficult
to control, and layer thicknesses that are very sensitive to minor
changes in silane concentration and incubation time. The silica shell
thicknesses are normally equal to or larger than the gold particles
themselves, which is disadvantageous when the particles are to be
used for biodiagnostic applications. We present a facile and reproducible
method to produce very thin silica shells (3–5 nm) on gold
nanoparticles: the process is highly tolerant to changes in reaction
conditions. The method utilized polyvinylpyrrolidone (PVP) of specific
molecular weights to form the interface between gold and silica. The
method further requires a nontraditional silica precursor, diglycerylsilane,
which efficiently undergoes sol–gel processing at neutrality.
Under these conditions, higher molecular weight PVP leads to thicker
silica shells: PVP acts as the locus for silica growth into an interpenetrating
organic–inorganic hybrid structure