Electrochemical event of single redox latex particles

The steady-state diffusion-controlled current of polyaniline-coated polystyrene latex particles suspended in water contained a periodic wave with a typical frequency of 14 Hz. The latex particles were monodispersed spheres, 2.6 mum in diameter. They were composed of cores of polystyrene on which a 0.4 mum thick redox active polyaniline film was coated, From the polyaniline layer of one particle, 5 x 10(10) electrons were transferred in the electrode reaction. The polyaniline showed the same electrochemical behavior as the conventionally electrodeposited polyaniline. The oxidation current of the suspension was controlled by diffusion. Although the oxidation current contained noise from the electric power source, its Fourier transformation exhibited a clear band, indicating that the particles had collided with the electrode at a given frequency, governed by thermal fluctuation, to be oxidized. The frequency had a linear relationship with the concentration of latex. It was invariant to the electrode potential and temperature. The redox charge involved at one frequency was 3 x 10(7) electrons from the polyaniline on one particle. The observation of a given frequency can be explained by collision of a particle with the electrode due to the redox diffusional flux, the oxidation of the partial charge, rebounding of the particle, a gain in the rebounding velocity from a decrease in the diffusional flux by oxidation, and collision again with the electrode without a loss of the velocity against friction.