Counterion distribution near a monolayer of variable charge densityK. Giewekemeyer and T. Salditt
Institut für Röntgenphysik - Friedrich-Hund Platz 1, 37077 Göttingen, Germany
received 14 February 2007; accepted in final form 21 May 2007; published July 2007
published online 19 June 2007
We study the bromide counterion distribution near a solid-supported monolayer in the case of vanishing bulk electrolyte concentration by resonant X-ray reflectivity. The surface charge density of the monolayer was varied by using different molar ratios of the cationic Di-Octadecyl-Di-methyl-Ammonium-Bromide (DODAB) and the neutral Di-Palmitoyl-Glycero-Phosphocholine (DPPC). The analysis, either based on a conventional box model with an additional counterion contribution, or based on an independent unbiased global optimization approach, yields a good agreement with the classical Poisson-Boltzmann theory for the salt-free case.
87.16.Dg - Membranes, bilayers, and vesicles.
83.85.Hf - X-ray and neutron scattering.
68.08.-p - Liquid-solid interfaces.
© Europhysics Letters Association 2007