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

Abstract

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 airoversaturated 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.

Decrease in the Surface Tension of Nanobubble Dispersion in Water: Results of Surface Excess of Bulk Nanobubbles at Interfaces

“…It is known that dissolved gas acts as a surfactant and that surface tension is reduced with more soluble gas. , Lee et al demonstrated that surface tension of water decreased considerably by increasing the DO content to 46 ppm. Geng et al proposed the mechanism of decrease in surface tension of oil nanodroplets in water, which is analogous to gas-filled NBs. These facts indicate that the influence of dissolved gas is not negligible under extremely high DO level conditions.…”

Mechanism of the Decrease in Surface Tension by Bulk Nanobubbles (Ultrafine Bubbles)

“…One possible explanation for the discrepancy is that bulk nanobubbles are a special kind of Janus particles, like chemically modified Janus particles, which reduce surface tension of water much more significantly than normal Janus particles . With regard to the influence of dissolved gases in the liquid, it has been known that any solutes could reduce the surface tension of water by increasing the translational entropy at the liquid’s surface, which results in the decrease in free energy of the liquid’s surface per unit area, equivalent to surface tension. , Accordingly, gases dissolved in liquid water reduce surface tension, as experimentally reported. − However, according to the experiments, − a considerable reduction in surface tension occurs only under the very high supersaturation of gases in liquid water. In the Tuziuti et al experiment, surface tension was measured for liquid water containing bulk nanobubbles under an almost saturated condition of air.…”

Effects of Nanobubbles on Photochemical Processes of Levofloxacin Photosensitizer

“…It was then placed in a vacuum-drying oven, degassed to below 0.1 atm, and held for more than 10 h. All degassing processes were repeated three times. 55,56 Generation of Bulk NBs. A detailed description of the generation of bulk NBs by the compression−decompression method is provided in the previous literature.…”

“…Nanoparticle tracking analysis (NTA) was used to measure the size distribution and concentration of NBs. The instrument used in the experiments was a Malvern NanoSight series instrument, model NS300, with NanoSight V3.4 software, which was capable of characterizing nanoparticles in the range of 10–2000 nm in different kinds of solutions by tracking the Brownian motion of the nanoparticles in real time and obtaining their concentration, particle size, and other relevant information …”

“…The instrument used in the experiments was a Malvern NanoSight series instrument, model NS300, with NanoSight V3.4 software, which was capable of characterizing nanoparticles in the range of 10−2000 nm in different kinds of solutions by tracking the Brownian motion of the nanoparticles in real time and obtaining their concentration, particle size, and other relevant information. 56 Laser Flash Photolysis Experiment. LFP is a powerful tool for the spectroscopic and kinetic determination of primary photophysical transformations and fast chemical reactions.…”