Photoswitchable adsorption of a Gemini surfactant containing Azobenzene group on the silica surface

Developing a method to control the adsorption/desorption of molecules at interfaces is of major importance in various interfacial processes. Herein, we report an Azobenzene-based Gemini surfactant (GAS), which can selectively adsorb onto the silica surface while about one-half of the adsorbed surfactants tend to be detached from the surface upon UV irradiation. The adsorption/desorption of the surfactant on the surface can be reversibly adjusted by using Vis or UV light alternately. The absorbed mass of the surfactant on the surface remains stable after two cycles of irradiation with Vis/UV light. The effect of light irradiation on the performances of the surfactant, such as surface activity, wetting, foaming and flotation power was investigated. A twostep adsorption mechanism of the surfactant on the surface was proposed based on the results of quartz-crystal microbalance with dissipation monitoring (QCM-D). Our study can provide insights into the unique properties of the photosensitive surfactant and its reversible adsorption/desorption process on the solid surfaces.

Automated summary

We report a Gemini surfactant based on azobenzene (GAS) that selectively adsorbs onto the silica surface and approximately half of the adsorbed surfactants tend to detach from the surface under UV irradiation. The adsorption/desorption of the surfactant on the surface can be reversibly adjusted using visible or UV light alternately. The study investigates the effect of light irradiation on the surfactant's performances and proposes a two-step adsorption mechanism on the surface based on the results of quartz-crystal microbalance with dissipation monitoring (QCM-D).