Investigation on the temperature difference method for producing nanobubbles and their physical properties.

In recent years, the possibility of nanobubbles at the solid-liquid interface has drawn wide attention in the scientific community and industry. Thus the search for evidences for the existence of nanobubbles became a scientific hotspot. To produce interfacial nanobubbles, a systematic experiment, called the temperature difference method, is carried out by replacing low temperature water (LTW) with high temperature water (HTW) at the highly-oriented pyrolytic graphite (HOPG)-water interface. When LTW (4 °C) is mixed with HTW (25-40 °C), nanobubbles are observed by atomic force microscopy (AFM), and their size, density and total volume per square micrometer are measured. Furthermore, pancake-like gas layers and the coexistence of nanobubbles on top of the pancake layers are also observed.