Thiol functionalisation of gold-coated magnetic nanoparticles: Enabling the controlled attachment of functional molecules

Gold-coated magnetite nanoparticles (Fe₃O₄-Au_coat NPs) have recently become the focus of research efforts which exploit the novel nano-architecture of these nanoparticles as platforms for magnetically controlled biomedical and analytical applications. To effectively utilise the Fe₃O₄-Au_coat NPs, thiol molecules can be bound onto the gold coating to provide a predictable surface for controlled attachment of functional molecules. Herein we present a facile process by which thiols with different moieties are attached to Fe₃O₄-Au_coat NPs. Dynamic light scattering and zeta-potential measurements were performed to study the effect of different thiols on the aggregation stability and surface charge of the Fe₃O₄-Au_coat NPs. The controlled attachment of an electroactive osmium complex is then demonstrated via voltammetric measurements. This work highlights importance of thiol molecule selection in enabling the fabrication of functional Fe₃O₄-Au_coat NPs.