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Heteroaggregation Approach for Depositing Magnetite Nanoparticles onto Silica-Overcoated Gold Nanorods
journal contribution
posted on 2017-12-11, 18:05 authored by Brian
S. Chapman, Wei-Chen Wu, Qiaochu Li, Niels Holten-Andersen, Joseph B. TracyHydrophobic, oleylamine-stabilized
magnetite nanoparticles (Fe3O4 NPs) dispersed
in hexanes can assemble into
dense coatings on the surface of silica-overcoated gold nanorods (SiO2-GNRs) dispersed in ethanol by mixing. In this nonaqueous
heteroaggregation process, Fe3O4 NPs are destabilized
when ethanol is added, resulting in core/satellite Fe3O4-SiO2-GNRs within a few minutes. The composition
of the solvent mixture allows tuning of the polarity and driving forces
toward aggregation. At the optimal 2:1 volume ratio of hexanes:ethanol,
heteroaggregation to form Fe3O4-SiO2-GNRs occurs quickly, while avoiding homoaggregation of Fe3O4 NPs or SiO2-GNRs. Fe3O4-SiO2-GNRs retain the longitudinal surface plasmon resonance
of the gold nanorod cores and are magnetically responsive and separable.
The Fe3O4 NPs remain bound on the surface of
the Fe3O4-SiO2-GNRs during multiple
cycles of magnetic extraction and redispersion. Oleylamine ligands
on the Fe3O4 NPs render the Fe3O4-SiO2-GNRs dispersible in nonpolar solvents. Functionalization
of the outer Fe3O4 surface with poly(ethylene
glycol) catechol (PEG-catechol) for PEGylation results in PEG-Fe3O4-SiO2-GNRs that disperse in water.
In comparison with seeded growth or use of molecular cross-linkers
to form multifunctional nanoparticles, heteroaggregation approaches
are potentially quite general, simple, and efficient. The ability
to continuously adjust the solvent polarity is expected to allow tuning
of the heteroaggregation process for many different types and sizes
of NPs.
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gold nanorod coresFe 3 O 4 surfaceoleylamine-stabilized magnetite nanoparticlessilica-overcoated gold nanorodsnonaqueous heteroaggregation processform multifunctional nanoparticlesSilica-Overcoated Gold Nanorods Hydrophobicform Fe 3 O 4Fe 3 O 4GNRsurface plasmon resonanceDepositing Magnetite NanoparticlesPEG-Fe 3 O 4Fe 3 O 4 NPsSiO 2
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