Monitoring of an Ethanol–Water Exchange Process to Produce Bulk Nanobubbles Based on Dynamic Light Scattering

Nanobubbles have been reported to have many novel applications due to their unique physicochemical properties. Ethanol-water exchange is regarded as one of the most convenient methods for producing nanobubbles; however, it is still questioned whether this method can produce bulk nanobubbles or not. In this paper, we present a method to monitor the ethanol-water exchange process based on a setup that combines the equipment of the ethanol-water exchange with an apparatus for dynamic light scattering. In contrast to the previous works where the measurements were performed after the exchanges were completed, our method measures the intensity of the scattered light from the beginning of the process to the end. We found that three different stages of the exchange process can be easily distinguished and that the diameters of the particles produced decrease as the exchange time increases. Furthermore, the measured diameters agree very well with a theoretical model presented very recently for the stability of the bulk nanobubbles in the liquid. Based on these findings, we believe that the products of the ethanol-water exchange are bulk nanobubbles. In addition, since our experimental setup provides the details of the ethanol-water exchange process, it can be used to investigate how to control the parameters of the final nanobubbles, such as their size, concentration, etc., which might promote the potential applications of bulk nanobubbles.