Kinetics of Sodium Dodecyl Sulfate Adsorption on and Desorption from Self-Assembled Monolayers Measured by Surface Plasmon Resonance

Abstract

By use of a flow cell in conjunction with surface plasmon resonance, experimental results are obtained for the intrinsic kinetics of sodium dodecyl sulfate (SDS) adsorption on and desorption from self-assembled monolayers (SAMs) on gold. When the flow of the bulk surfactant solution in the flow cell is increased, conditions are reached where the surface kinetics are rate controlling and mass transfer limitations in the bulk solution are negligible. The SDS adsorption and desorption rates increase with the bulk surfactant concentration in the monomer regime. At and above the critical micelle concentration of SDS, the adsorption and desorption rates become nearly constant. It is shown that SDS needs to be recrystallized to remove minute impurities. The results suggest that the SDS monomers play a dominant role in adsorption and desorption on SAMs. Sodium dodecyl sulfate has a greater affinity for hydrophobic SAMs than for charged, hydrophilic SAMs. The data also suggest that the kinetics of adsorption and s...