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Multidentate Ionic Surfactant Mediated Extraction and Dispersion of Gold Nanoparticles in Organic Solvents
journal contribution
posted on 2014-08-05, 00:00 authored by Sangbum Han, Ramjee BalasubramanianResorcinarenes
with three different quaternary ammonium headgroups were synthesized
and evaluated for their ability to stabilize gold nanoparticles in
organic and aqueous medium. Aqueous dispersions of citrate stabilized
gold nanoparticles of dimensions up to 29 nm could be extracted into
organic solvents by resorcinarenes functionalized with tetrapyridinium
tetrabromide (1), tetratrimethylammonium tetrabromide
(2), and tetratributylammonium tetrabromide (3). Such nanoparticles were characterized by TEM, EDS, UV–vis,
and IR. Their long-term dispersion stability varied significantly
and depended on the nature of the resorcinarene headgroup, and in
particular nanoparticles extracted by resorcinarene 1 were stable for several weeks. Nanoparticles passivated by resorcinarenes 1 and 2 were also stable in the presence of thiourea
for several hours in both aqueous and organic medium. This is notable
as thiourea is known to result in the instantaneous aggregation of
citrate stabilized nanoparticles. Remarkably nanoparticles stabilized
by resorcinarenes 1 and 2 could be precipitated
and redispersed in chloroform without any visible aggregation. The
critical parameters controlling the extraction of the nanoparticles
into the organic phase have also been evaluated. The resorcinarene
surfactant mediated facile phase transfer of gold nanoparticles described
here can be readily applied for the stabilization of other citrate
stabilized mono- and bimetallic nanoparticles, thus providing opportunities
to disperse and stabilize relatively larger nanoparticles in organic
solvents using ionic surfactants opening up new applications.