Influence of the Dissolved Gas on the Interfacial Properties of Decane Surface Nanodroplets

Surface nanodroplets have received extensive attention recently due to their potential in the fabrication of functional materials with nanostructures and chemical reactions at micro- and nanoscales. Although the effect of dissolved gas in water has been realized in some important processes such as spontaneous emulsification of oil droplets in water, its roles in the wetting behavior of surface nanodroplets at the hydrophobic interface have been largely neglected. Here, we focused on the influence of dissolved gas on the interfacial properties of surface nanodroplets and characterized their morphological evolution when exposed to different air-saturated water samples. Results indicated that the morphology of surface nanodroplets barely changed in air-oversaturated cold water. However, their contact angle first decreases gradually in deionized water, increases immediately after replacement with degassed water, and eventually decreases gradually with time. Furthermore, the surface tension of nanodroplets would change similarly after the injection of degassed water. We considered these changes to be caused by the removal or reduction of the enriched gas at the substrate interface, in which the surface hydrophobicity was changed. Our findings could shed some light on the wetting behavior of nanodroplets at the hydrophobic surface in different air-saturated water samples and inspire the microscale manipulation and reaction of surface nanodroplets.