Electrochemical Modulation of the Optical Properties of Poly (3,4- ethylenedioxythiophene) (PEDOT)-Coated Core-Shell Silica Spheres in a Hydrogel- Stabilized Matrix

摘要

An intrinsically conductive polymer poly (3,4- ethylenedioxythiophene) (PEDOT)1 has been used to generate a polymerized self-assembled crystalline colloidal array (PCCA). Nanometer sized silica particles with a thin PEDOT shell were synthesized and formed a self-assembled crystalline colloidal array. 2 These colloidal particles are isolated in the hydrogel networks and not in contact with the conductive support; chemical modification of the redox states of the particles must be performed by electrogenerated oxidative/reductive mediators. The use of mediated electron transfer systems for the development of biosensors has been extensively examined. 3 This same process can be applied to these isolated PEDOT coated silica particles. Mediators can diffusionlly shuttle electrons between the electrode and the PEDOT coating. Mediators can diffusionlly shuttle electrons between the electrode and the PEDOT coating. Fundamentally, at reductive potentials the mediator would be selectively reduced at the surface of the electrode and then diffuse to the doped PEDOT to under go rapid electron transfer and de- dope the PEDOT and then subsequently diffuse back to the electrode surface to be reduced again. This same process would then occur at oxidative potentials in order to re-dope the PEDOT. The redox cycle of PEDOT-coated silica particles in aqueous solution are typically from - 700 mV to +400 mV vs a Ag/AgCl/Cl (sat) reference electrode with a switching potential at about -100 mV between the doped and dedoped state. Selection of the redox mediator requires that the electrogengerated oxidant or reductant must have a potential that is at least 200 mV greater than PEDOT. Coupling the intrinsic absorbance changes caused by switching the oxidation states of PEDOT-coated core-shell silica particles with the Bragg diffraction of a self-assembled colloidal array could lead to interesting optical properties. This work examines the intrinsic absorbance changes caused by switching the oxidation states of synthesized PEDOT-coated core-shell silica particles (150 nm diameter) that were suspended in a colloidal solution and subsequently locked into a hydrogel matrix.