Effect of pH, surface charge and counter-ions on the adsorption of sodium dodecyl sulfate to the sapphire/solution interface

► Increasing pH reduces adsorption but does not alter the thickness of the adsorbed layer. ► Different crystal faces show different adsorption that is correlated with the surface charge. ► Adsorbed layers of SDS are thinner than a bilayer of extended chains and are highly hydrated. ► Cesium dodecyl sulfate forms dense layers, well below the critical micelle concentration.