Dynamic- and Light-Switchable Self-Assembled Plasmonic Metafilms

Abstract

Large-area dynamic switchable plasmonic metafilms composed of a network of gold nanoparticles (Au NPs) and the thermo-responsive polymer poly(N-isopropylacrylamide) (PNIPAM) are self-assembed by casting Au@PNIPAM core-shell nanoparticles. These dense plasmonic films present an unusual optical behaviour arising from the macroscale effective medium response of the film and the microscopic interactions of the gold nanoparticles. Such intensely-coloured plasmonic metafilms can be thermally actuated on large areas via direct heating, allowing extraction of how the effective dielectric permittivity of this metamaterial is tuned. By contrast, local plasmonic heating by illuminating the Au NPs in these metafilms enables sub-second and highly reversible contraction of the plasmonic metafilms, capable of pumping water. This work provides an paradigm for switchable metafilms and metasurfaces that can be harnessed for different applications such as sensing, imaging optics, and image displays.