The measurement and interpretation of fluctuations in electrochemical systems: The electrocrystallisation of silver and the voltage-gated alamethicin induced channel conductance in lipid bilayers

Abstract

The analyses of fluctuations due to the voltage-gated alamethicin induced channel conductance in lipid bilayers and due to the electrolystallisation of silver are developed further. For the first system it is shown that it is possible to decompose the experimentally observed compound system (many pores) into the behaviour of the elementary system (a single pore) together with a time-dependent trigger rate; the elementary system is confined by an upper and lower reflecting state and the edge and bulk energies of the pore are shown to be independent of time. For the second system it is shown that lattice formation takes place at the edges of circular growth centres randomly nucleated in space on the substrate electrode. Measurements of quantities related to the second moment of the time dependent reaction rate (together with measurements of the mean rate) lead to independent estimates of the rates of nucleation and of crystal growth, of the mean lifetime of growth centres and of the form of the mean current-time transient due to the growth of single centres. At low overpotentials and long times nucleation follows a Poisson distribution; at short times and at higher overpotentials nucleation has the character of a delayed renewal process. Other complex and as yet unexplained changes with time of the rates of nucleation (and of crystal growth) are observed at long times at higher overpotentials.