Electrochemical tuning the optical properties of crystalline colloidal arrays composed of poly(3,4-ethylenedioxythiophene) coated silica particles

Abstract

The position and height of the reflection peak of a hydrogel-encapsulated crystalline colloidal array composed of silica particles with a coating of poly(3,4-ethylenedioxythiophene) (PEDOT) could be varied through electrochemical means. This optical tuning was achieved by altering the complex refractive index of the PEDOT shell through a manipulation of its redox state, specifically the absorption characteristics. A mediated electron transfer system was employed to ferry charge from the electrodes of the cell to the isolated particles for both the oxidation and reduction processes. The mediators diffused between the electrode surfaces and the PEDOT-coated particles to accomplish (de)doping of the entire colloidal array. The reflected peak from an ordered array exhibited a significant drop in height during a typical reduction process, dropping to 40% of its original height, though the peak height could be reinstated by re-oxidizing the particles with an imposed bias shift to the cell.