Investigation on nanobubbles on graphite substrate produced by the water–NaCl solution replacement

• Published in: Surface science Vol. 606; no. 17-18; pp. 1462 - 1466
• Main Authors: Guo, Wen, Shan, Han, Guan, Min, Gao, Lianhua, Liu, Minghuan, Dong, Yaming
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01.09.2012; Elsevier
• Subjects: AFM; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; HOPG; NaCl; Nanobubbles; Physics; NaCl; AFM; Nanobubbles; HOPG; Water; Atomic force microscopy; Inorganic compounds; Graphite; Sodium chloride
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2012.05.018

How to produce nanobubbles repeatedly on a certain surface with sufficient amount is a key issue in nanobubbles research. It is well known that nanobubbles can be produced by exchanging water with organic solutions like alcohol which contains higher concentration of dissolved gas than that in water. However, it is not clear if this mechanism would work when exchanging water with the relatively low concentrations of dissolved gas such as salt solutions. In this paper, we employed NaCl solutions with different concentrations to replace water on graphite surface. We found that nanobubbles could indeed be generated and showed similar properties with those produced by other methods. Nanobubbles could be apparently observed when the NaCl concentration was as low as 0.15M and their densities increased with the salt concentrations. When the concentration of NaCl was higher than 2.00M, the number of nanobubbles increased slowly and nearly kept a constant. We also showed that the dissolved gas played an important role in the formation process of nanobubbles. ► On HOPG surfaces, water–NaCl solution exchange can repeatedly produce nanobubbles. ► Nanobubble density increases with salt concentrations ranging from 0.15M to 4.00M. ► Their diameter decreases with the salt concentrations. ► For 2.00 and 4.00M of NaCl, the density of nanobubbles has little difference. ► The dissolved gas played an essential role in the process of nanobubbles formation.