Organic plasmonics: PEDOT nanoparticles are getting closer to the visible range

Abstract

Most plasmonic materials use metallic nanoparticles (NPs) of gold or silver. Plasmonic behaviors are also possible to achieve in several organic materials such as carbon dots or conductive polymers (CPs). Here, we report the synthesis of poly(3,4-ethylenedioyothiophene) (PEDOT) arrays of NPs well organized on a surface by the combined use of e-beam lithography and electropolymerization. The as-grown NPs show plasmonic behavior, with small variations in localized surface plasmon resonance (LSPR) between 1200 and 1300 nm related to the differences in their diameters (90 nm, 120 nm, and 150 nm). The properties of the arrays were chemically tuned by treatment with acetic acid to enhance their conductivity, leading to a tremendous 300 nm blue shift of their optical extinction. The PEDOT NP array after this secondary doping shows an unprecedented LSPR maximum at 960 nm, close to the visible range.