TEMPERATURE-DEPENDENCE OF THE LATERAL DIFFUSION OF ACRIDINE-ORANGE ATWATER HYDROCARBON INTERFACES/

The temperature dependence was investigated for the lateral diffusion of acridine orange at the interface of water and an octadecylsiloxane (C-18) monolayer on silica and at the interface of water and liquid n- dodecane. Fluorescence recovery after pattern photobleaching was used to measure the lateral diffusion coefficient. The data revealed very d ifferent activation parameters for lateral diffusion at the two interf aces. For the water/dodecane interface, the activation enthalpy for la teral diffusion is consistent with stronger ordering of water at the i nterface compared to bulk water. For the water/C-18 interface, a large entropic barrier is observed, indicating that the path for diffusion is restricted by high-energy adsorption sites. Further, the activation enthalpy is 5-fold lower than that of the water/dodecane case, indica ting that transport to the unfavorable sites is not rate-limiting.