Toward Self-Assembly of Nanoparticles on Polymeric Microshells: Near-IR Release and Permeability

We present a novel approach to construct hollow polymeric microcontainers that can be remotely addressed using a low-power near-infrared laser to release encapsulated materials. Microshells possessing walls with aggregates of gold nanoparticles are found to release encapsulated materials upon near-IR irradiation, while shells containing the same amount of nonaggregated gold nanoparticles did not release their contents. The permeability of thermally shrunk microcapsules to dextran molecules is the lowest for shells containing nonaggregated nanoparticles and the highest for microcapsules with no nanoparticles. The wall thickness, roughness, influence of concentration of encapsulated materials, and general shrinking behavior of the microcapsules are studied. Aggregation of nanoparticles increases the absorption coefficient in the near-infrared part of electromagnetic spectrum. The temperature increase upon near-infrared laser illumination for different gold nanoparticle distributions is simulated. Important implications of this approach are expected in development of drug delivery systems as well as in temperature- and light-sensitive materials and membranes.