17. Switchable Optical Nano-antennas from Conducting Polymers

Suraya Kazi, Akchheta Karki, Shangzhi Chen, Magnus Jonsson*

Our group recently introduced conducting polymers as a new category of materials for dynamically tuneable nanooptics.^[1,2,3] In brief, we showed that conducting polymer nanostructures can strongly interact with light at specific wavelengths through plasmonic resonances, acting as optical nanoantennas. The plasmons originate from mobile polaronic charge carriers in the polymer network, which leads to negative permittivity as for conventional metals. The plasmonic resonance nanostructures could then be reversibly turned on/off by varying the redox state of the material, which modulates the density and mobility of the charge carriers and thereby switches the permittivity between negative (metallic) to positive (dielectric).^[2] Such dynamic character, in addition to biocompatibility and flexibility, inherent to conducting polymers cannot be achieved in conventional metallic plasmonic nanostructures due to fixed permittivity. We typically fabricate the nanoantennas by deposition of a thin film of the conducting polymer using vapor phase polymerization, which is then structured into arrays of nanodisks using colloidal lithography. As examples of characterization techniques, we use ellipsometry, UV-vis spectroscopy, four-point probe measurements, and atomic force microscopy to determine permittivity, extinction spectra, conductivity, and geometry of the materials and nanostructures, respectively. Redox-tunable conducting polymer nano-antennas have potential for applications such as smart windows, reflective displays and not least dynamic metaoptics including flat lenses, holograms etc.^[1,2]

Reference:

1. Chen, S. et al.Conductive polymer nanoantennas for dynamic organic plasmonics.  Nanotechnol. 15, 35–40 (2020).
2. Karki, A. et al.Electrical tuning of plasmonic conducting polymer nanoantennas.  Mater. 34, 2107172 (2022).
3. Karki, A. et al.Doped semiconducting polymer nanoantennas for tunable organic plasmonics. Commun Mater 3, 48 (2022).