Bulk Nanobubbles Fabricated By Repeatedly Compression of Microbubbles

• Published in: Langmuir 2019-02
• Main Authors: Jin, Juan, Feng, Zhenqiang, Yang, Fang, Gu, Ning
• Format: Article
• Language: English
• ISSN: 1520-5827
• DOI: 10.1021/acs.langmuir.8b04314

Nanobubbles (NBs), given its extraordinary properties, have drawn keen attention in the field of nano-technology worldwide. However, compared to the prevailing method in obtaining surface nanobubbles, to obtain the stable bulk nanobubbles remains an arduous task. In this study, we developed a pressure-driven method to prepare bulk nanobubbles by repeatedly compressing sulfur hexafluoride (SF6) gas into water. The results show that NBs with mean diameter of 240 ± 9 nm and PDI of 0.25 were successfully prepared. The generated NBs had a high negative zeta potential (- 40 ± 2 mV) with stability of more than 48 h. Under the condition of 600 times repeated compression, the nanobubble concentration could reach about 1.92×1010 bubbles/mL. Furthermore, we examine the possible formation mechanism involved in NBs generation by virtue of optical microscope and attenuated total reflectance infrared spectroscopy (ATR-FTIR). The microscopic results showed that microbubble about 10~50 μm firstly formed and then decreased to be nanoscaled size. The stronger hydrogen bond was detected by ATR-FTIR spectroscopy during the shrinking of microbubbles into nanobubbles. It is speculated that the disappearance of microbubbles contributes to the formation of nanobubbles, and the strong hydrogen-bond at gas-water interface prompts the stability of NBs. Therefore, by the repeated compression of pressed gas in aqueous solution, it could be a new method to prepare stable nanosized bubbles for wide applications in the future.