Effects of halide ions on the acceptor phase in spontaneous chemical oscillations in donor/membrane/acceptor systems.

The effects of halide ions on the acceptor phase in the chemical oscillation in donor/membrane/acceptor systems were examined. The transfer of cetyltrimethylammonium (CTA(+)) ions from the donor phase and their adsorption and desorption at the membrane/acceptor interface led to spontaneous, nonlinear oscillations of the electric potential. Chloride ions stabilized the adsorption of CTA(+) ions and gave rise to a large-amplitude, long-interval, and a long relaxation-time constant. On the contrary, iodide ions, which are more hydrophobic than chloride ions, demonstrated opposite results. This mechanism was proposed based on the simultaneous time-resolved measurements of the interfacial tensions at both the donor/membrane and membrane/acceptor interfaces and observation of the convective flow due to Marangoni instability.