Measurement of the rate of transfer of a probe molecule through a surfactant layer at the water:oil interface using TF-MuSR

Project Details


Molecular transfer across interfacial layers is a rapid process that cannot generally be measured by laboratory-based fast reaction techniques (stopped flow, temperature-jump). To date experimental techniques have largely been based around slow mass transfer measurements using diffusion cells. The approach here does not exclusively quantify the interfacial transfer but measures rates that include transfer through diffusion layers close to the interface [Steytler, D. C.; Towey, T. F.; Robinson, B. H.; Atay, N. Z., Mechanisms of solute interfacial transfer in Winsor-II systems. Langmuir 2001, 17, (2), 417-426.]. With judicial choice of system and "probe molecules", TF-MuSR offers a unique opportunity to directly probe interfacial transfer dynamics and energetics. By choosing a suitable probe (muon capture) molecule that exhibits balanced partitioning between oil and water, a dispersed oil:water system can be used with a "spin-quencher" in one of the liquid phases. The muon-electron hyperfine interaction can then be monitored for which the width of the signal gives the probe lifetime for crossing the interface. Combined with temperature variation, energetic parameters can also be extracted using this approach.
To provide the large interfacial area, we propose to employ a well characterised water-in-oil (w/o) micro-emulsion stabilised by bis(2-ethyl hexyl) sodium sulphosuccinate (Aerosol OT) [2]. The system comprises thermodynamically stable nanodroplets of water-in-oil for which the droplet size can be controlled through the water-to-surfactant molar ratio (w)
Effective start/end date20/10/0819/02/10


  • Engineering and Physical Sciences Research Council: £25,562.00