Controllable Optical Properties of Polystyrene/PNIPAM-Gold Composite Nanoparticles

The optical properties of polystyrene-gold nanoparticles are simulated to understand the role of surface coverage, particle spacing, and plasmonic coupling on the optical properties. The particles are based on recent work in synthesizing composite particles via one-step Pickering emulsion techniques. These techniques can be used to develop particles with variable gold particle surface coverage on the surface of the thermoresponsive polymer core. With careful control of the surface coverage, it can be shown through simulation that a thermoresponsive particle can dynamically control the absorption peak from that of a single gold sphere (∼520 nm) to the red-shifted absorption peak of a uniform core-shell nanoparticle of similar geometry. The optical properties are shown to reside with the bounding limits of simple gold nanoparticles and core-shell nanoparticles of similar geometry but are highly dependent on the surface coverage. Furthermore, it is demonstrated how the overall extinction of asymmetric particles can be dominated by either the core particle or the attached surface particles, depending upon the temperature state of the particle.