Electrochemical Switching of Plasmonic Colors Based on Polyaniline-Coated Plasmonic Nanocrystals.

Plasmonic color generation has attracted much research interest because of the unique optical properties of plasmonic nanocrystals that are promising for chromatic applications, such as flat-panel displays, smart windows, and wearable devices. Low-cost, monodisperse plasmonic nanocrystals supporting strong localized surface plasmon resonances are favorable for the generation of plasmonic colors. However, many implementations so far have either a single static state or complexities in the particle alignment and switching mechanism for generating multiple displaying states. Herein, we report on a facile and robust approach for realizing the electrochemical switching of plasmonic colors out of colloidal plasmonic nanocrystals. The metal nanocrystals are coated with a layer of polyaniline, whose refractive index and optical absorption are reversibly switched through the variation of an applied electrochemical potential. The change in refractive index and optical absorption results in the modulation of the plasmonic scattering intensity with a depth of 11 dB. The electrochemical switching process is fast (∼5 ms) and stable (over 1000 switching cycles). A device configuration is further demonstrated for switching plasmonic color patterns in a transparent electrochemical device, which is made from indium tin oxide electrodes and a polyvinyl alcohol solid electrolyte. Our control of plasmonic colors provides a favorable platform for engineering low-cost and high-performance miniaturized optical devices.