Magneto-plasmonic polymer hybrid microparticles with tunable morphology and integrated property

Magneto-plasmonic hybrid microparticles composed of binary nanoparticles (NPs) provide an effective platform for integrating distinct physical properties into a single colloidal entity. Here, we report a facile emulsion-confined co-assembly strategy to construct gold-magnetite (Au-Fe₃O₄) hybrid microparticles with tunable morphologies by manipulating the molecular weight (MW) of polystyrene (PS) ligands and the properties of the surfactant. When the PS ligand on Au NPs is short (2 kDa), the morphology is strongly governed by surfactant charge, resulting in a transition from Janus to Fe₃O₄-core/Au-shell (Fe₃O₄-in-Au) structures as the surfactant changes from cationic to anionic. Increasing the PS MW induces a morphology shift toward Au-core/Fe₃O₄-shell (Au-in-Fe₃O₄) structures, irrespective of the surfactant type. Furthermore, these binary hybrid microparticles exhibited shape-dependent behavior in both optical absorption and T₂-weighted magnetic resonance imaging (MRI) performance. This shape-dependent control provides an alternative route for designing multifunctional magneto-plasmonic colloids.