A general route towards well-defined magneto- or fluorescent-plasmonic nanohybrids

Abstract

Herein, we present a general route towards defined nanohybrids, comprised of a fluorescent quantum dot (QD) or superparamagnetic iron oxide (Fe₂O₃) nanocrystal core and a tuneable corona of plasmonic gold or silver nanoparticles (NPs), adhered by a cross-linked poly(isoprene)-b-poly(ethylene glycol) diblock copolymer (PI-b-PEG) matrix. To this end, the PEG-terminus of the amphiphilic polymer was acylated with lipoic acid (LA), which, as is known, forms quasi-covalent Au–thiol- or Ag–thiol-bonds. Surprisingly, by variation of the ratio of the different NPs, inverse core/satellite structures bearing QDs or Fe₂O₃ around a metallic NP core were obtained. Furthermore, gold NPs or even closed gold shells were grown by in situ reductive deposition of Au³⁺ ions on Fe₂O₃ NP seeds. Finally, in order to demonstrate the scope of the method, ternary nanohybrids, composed of QDs, Fe₂O₃ and Au NPs, were accomplished. All magneto-plasmonic and fluorescent-plasmonic materials were thoroughly characterized by absorption and emission spectroscopy, TEM and TEM-EDX. Antibody conjugation to these novel nanohybrids proved their practical utility in a prototype immunoassay.