EAPSI: Stimuli-responsive capsules from polymer-covered gold nanorods

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'Smart' materials that respond to external stimuli, such as a change in temperature, pH, ionic strength, light exposure, or electric field, are the subject of a large body of research for applications that range from artificial muscles to sensors to the delivery of therapeutics. This project will investigate the stimuli-responsive behavior of oil-in-water droplets stabilized by polymer-covered gold nanorods (rod-shaped nanometer-sized gold particles, Au NRs), which are responsive to temperature, salt concentration, and light. Dr. Hongwei Duan, an expert in assemblies composed of polymer-covered particles, at Nanyang Technological University in Singapore will served as the host for this research. Placing special materials, such as Au NRs and polymers, at the oil-water interface of these droplets will afford new materials that hold great promise as highly functional, responsive systems.Assembling polymer-nanoparticle composites into two- or three-dimensional structures affords properties distinct from the individual components that are broadly interesting for chemistry, physics, engineering, and biology. This project will involve the incorporation of salt- and temperature-responsive zwitterionic polymers onto Au NRs. The versatility of polymer chemistry lends itself to easily combine stimuli-responsive functional groups with moieties that facilitate cross-linking and binding to gold into the same polymer, while Au NRs are ideal components of smart materials due to their biocompatibility and inherent ability to convert light into heat. The nanocomposites will be assembled at the oil-water interface, on droplets, and subsequently cross-linked into mechanically robust capsules. The response of these assemblies to external stimuli (i.e. salt, temperature, and light) will be studied by optical microscopy and by surface enhanced Raman scattering (SERS). To demonstrate the utility of these capsules for encapsulation, the uptake and release of a dye will be monitored. This NSF EAPSI award is funded in collaboration with the National Research Foundation of Singapore.