Composite-walled magnetic microcapsules at the water-toluene interface by ligand polymerization

The liquid-liquid interface has been exploited as a platform for devising gold and iron oxide nanoparticle (NP)-decorated composite microcapsules (MCs) by cross-linking between -OH groups of poly(ethylene glycol) (PEG) attached to the iron oxide (Fe3O4) nanoparticle surface and starch attached to the gold (Au) nanoparticle surface in the presence of terephthaloyl chloride as a cross-linker. These nanoparticle-decorated capsules form a shell of both types of nanoparticles with water as the minor phase and toluene as the major phase. The morphology of these capsules has been characterized by optical, transmission, and scanning electron microscopy images, and the polymerization reaction has been established by UV-vis and FTIR spectroscopic studies. The magnetic behavior of the capsules has been illustrated by using an external magnetic field to tailor the magnetic control of the capsules. The encapsulated phase was impregnated with dye molecules of three different sizes, viz., fluorescein isothiocyanate and its dextran conjugates, to investigate the permeability of the capsule wall by fluorescence spectroscopy. Interestingly, the microcapsules exhibit size-selective permeability across the capsule wall that points to their plausible applications in controlled encapsulation and release.