In Situ Atomic Force Microscopy Investigation of Temperature-Dependent Properties of Interfacial Nanobubbles on Highly Oriented Pyrolytic Graphite Surfaces.

The temperature of water is positively correlated with its air-saturation concentration. Variations in the temperature can influence the degree of air oversaturation, which is critical for the evolution of interfacial nanobubbles (INBs). We hypothesize that an increase or decrease in the temperature will lead to a corresponding increase or decrease in the properties of INBs. Air-oversaturated water was prepared by chilling the water in a refrigerator, and the air concentration in the chilled water was subsequently measured. The temperature of the liquid cell containing water and highly oriented pyrolytic graphite (HOPG) was controlled by using a temperature controller. Variations in the height and base diameter of INBs with temperature were measured in situ using atomic force microscopy (AFM). As the water temperature increased, the height and mass of the INBs increased significantly, while the base diameter changed only slightly. Conversely, as the temperature decreased, both the height and mass of the INBs decreased notably with minimal change in base diameter. Based on the theoretical understanding of INBs stability and experimental observations, it was found that surface gas layers, in addition to air oversaturation in water, play a significant role in supporting the stability of INBs.