Rotational diffusion current of multi-charged redox species by means of Monte Carlo simulation

Abstract

Multi-charged redox species such as dispersed metal nanoparticles and latex particles have exhibited diffusion-controlled currents, which may be caused by not only the conventionally translational diffusion but also by the rotation of the species or random orientation toward the electrode. Rotational diffusion was here taken into account by use of the multiple redox-charged model particle which moves back and force in thin layer cell as well as rotates clockwise and counterclockwise by means of the Monte Carlo simulation. The steady-state current was smaller than the current which might flow if all the charge were to transfer at infinite rotational speed. The current values had a linear relation with the -1/2 powers of the number of the charge per particle. This relation was in accord with the experimental results of the partial charge transfer reaction of the ferrocene-immobilized latex suspension

Dissociation kinetics at polyacrylic latex-coated electrodes

“…However, the redox reaction is sometimes blocked by a loss of freedom of the redox sites on the latex. For example, ferrocenyl latexes have been partially oxidized at electrodes by geometrical restriction of a reaction zone [29][30][31][32] or rotational diffusion [33,34]. Geometrical hindrance of the polyaniline latex has given rise to unpredicted behavior such as oscillation currents [35], discrete currents independent of the latex concentration [36], and the irreversible waves due to the electric percolation [37].…”

Size-dependent efficiency of electron transfer at suspended ferrocenyl jumbo particles

“…9), all the redox electrons per particle for a < 60 nm can react without hindrance. The value À0.47 reminds us of the relation, n cv / n uv = k 1 a À0.5 + k 2 for the current controlled by rotational diffusion as well as translational diffusion of jumbo redox particles obtained by the Monte Carlo simulation [18]. Since the simulation has been based on the assumption of surface-localized redox charge rather than the volumetric distribution, the application to the present latex is not reasonable.…”

“…Furthermore, an essential problem lies in the concept of which reaction actually occurs [17], R n M O n + ne À or n(R M O + e À ) even in equilibrium. More complications can be included in currents owing to not only translational diffusion of particles but also rotational diffusion [18], partial electron transfer of the redox sites on the particle surface in contact with an electrode [9,10], detachment of redox sites from particles [9], and charge transport within particles. They ought to depend not only on size of particles but also distribution of redox sites within one particle.…”

Voltammetric determination of concentrations of ferrocene-included nitrobenzene droplets in water

“…From the electrochemical viewpoint, oil droplets containing redox species resemble suspended redox latex particles such as hydrogen ion in polystyrene latex [43], polyaniline-coated polystyrene [44][45][46], ferrocenyl derivatives on polystyrene [47,48], and polyacrylic acid-polystyrene latex [49]. Redox latex particles react at electrodes by releasing redox moieties [43,47], propagating redox reactions in the latex particles [44][45][46], letting redox moieties diffuse in the latex particles [48] or contacting the spherical surface with electrodes [49,50]. In contrast, droplets including redox species cannot react at an electrode until they are adsorbed.…”