  Metal nanostructures are key elements in nanooptics owing to their strong
resonant interaction with light through local plasmonic charge oscillations.
Their ability to shape light at the nanoscale have made them important across a
multitude of areas, including biosensing, energy conversion and ultrathin flat
metaoptics. Yet another dimension of avenues is foreseen for dynamic
nanoantennas, ranging from tuneable metalenses for miniaturized medical devices
to adaptable windows that control radiation flows in and out of buildings.
However, enabling nano-optical antennas to be dynamically controllable remains
highly challenging and particularly so for traditional metals with fixed
permittivity. Here we present state-of-the-art conductive polymers as a new
class of organic plasmonic materials for redox-tuneable nano-optics. Through
experiments and simulations, we show that nanodisks of highly conductive
polymers can provide clear optical extinction peaks via excitation of dipolar
localised surface plasmon resonances. Resonance frequencies redshift with
increasing nanodisk aspect ratio, in agreement with analytical calculations
based on dipolar polarizability theory. We furthermore demonstrate complete
switching of the optical response of the organic nanoantennas by chemical
tuning of the polymer's redox state, which effectively modulates the material
permittivity between plasmonic and non-plasmonic regimes. Our results thereby
show that conductive polymer nanostructures can act as redox-tuneable plasmonic
nanoantennas, based on bipolaronic charge carriers rather than electrons as in
conventional metals. Future directions may investigate different polymers and
geometries to further widen the plasmonic spectral range (here around 0.8 to
3.6 {\mu}m) as well as different ways of tuning.
