Bromide-doped polypyrrole microcapsules modified with gold nanoparticles

Micrometer sized polypyrrole capsules were prepared through the photochemical deposition of polymer onto the surface of aqueous droplets dispersed in bromoform. Scanning electron microscopy and transmission electron microscopy analyses demonstrate that the microcapsules are ca. 550 nm in diameter and contain an empty hollow region surrounded by a ca. 40 nm thick polymer shell. The XPS data reveal that the polymeric shell consists of polypyrrole doped with bromide anions, likely originating from the decomposition of bromoform during the photopolymerization reaction. The incorporation of gold nanoparticles inside the capsule allows for the ultrasound-triggered rupture of the structure. This phenomenon was applied to liberate encapsulated Rhodamine 6G to the external solution. This finding is very promising for possible applications in controlled drug delivery.