Surfactants are key components in many products and processes where their surface-active properties are needed, and in such applications, the surfactant-surface interaction dynamic could be critical. Here we show how the surfactant interaction with surfaces can be analyzed in a time-resolved manner at the nanoscale.
Monitoring and quantification of surfactant adsorption to a surface
In several products and processes, such as in detergents and cleaning agents, in pharmaceutical formulations, in oil recovery, CMP, as well as in mining, the surfactant-surface interaction dynamic is critical to the application. It is therefore relevant to understand these processes at the nanoscale. In this study, QSense QCM-D, which is a surface-sensitive real-time technology, was used to characterize the surfactant adsorption. Two different surfactants were analyzed, Triton-X and ßOG. The focus of the QCM-D measurements was to analyze:
the surfactant adsorption dynamics
the amount of surfactant adsorbed, and
the stability of the surfactant-surface interaction
The surface interaction dynamics differ between the two surfactants
The results, Figure 1, show that both Triton X-100 and ßOG adsorb to the surface. However, the time to saturation differs between the two, and Triton X-100 reaches saturation faster that ßOG even though the concentration was lower. The results also show that ßOG forms a thicker layer than the Triton X-100 and that more ßOG than Triton X-100 remains at the surface after rinse.
Figure 1. Time-resolved thickness change as the surfactants, Triton X-100 and ßOG, adsorb to the sensor surface.
Key takeaways from the time-resolved surface interaction analysis:
Triton X-100 reaches saturation faster than βOG
βOG forms a soft film
Triton X-100 forms a rigid film
βOG forms a thicker layer than Triton X-100
In several products and processes, the surfactant-surface interaction dynamic is important and therefore relevant to understand at the nanoscale. QCM-D analysis provides information on surfactant-surface interaction processes under a variety of different substrate- and experimental conditions. Via this quantification of the surfactant-surface interaction, conclusions can be drawn regarding the suitability of surfactants in different applications.
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QCM-D is designed to detect minute variations in frequency, f, and dissipation, D. Here we have compiled a checklist that will help you optimize the reproducibility of your QCM-D measurements by minimizing unintentional changes of the recorded parameters.