title: Microwave-Induced Interfacial Nanobubbles.
abstract: A new method for generating nanobubbles via microwave irradiation was verified and quantified. AFM measurement showed that nanobubbles with diameters ranging from 200 to 600 nm were generated at a water-HOPG surface by applying microwave radiation to aqueous solutions with 9.0-30.0 mg/L dissolved oxygen. Graphite displays strong microwave absorption and transmits high thermal energy to the surface. Because of the high dielectric constant (20 °C, 80 F/m) and dielectric loss factor, water molecules have a strong ability to absorb microwave radiation. The thermal and nonthermal effects of microwave radiation made contributions to decreasing the gas solubility, thus facilitating nanobubble nucleation. The yield of nanobubbles increased about 10-fold when the irradiation time increased from 60 to 120 s at 200 W of microwave radiation. The nanobubble density increased from 0.8 to 15 μm-2by improving the working power from 200 to 600 W. An apparent improvement in nanobubbles yield was obtained between 300 and 400 W, and the resulting temperature was 34-52 °C. When the initial dissolved oxygen increased from 11.3 to 30.0 mg/L, the density of nanobubbles increased from 1.2 to 13 μm-2. The generation of nanobubbles could be well controlled by adjusting the gas concentration, microwave power, or irradiation time. The method may be valuable in preparing surface nanobubbles quickly and conveniently for various applications, such as catalysis, hypoxia/anoxia remediation, and templates for preparing nanoscale materials.
authors.affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Miao
authors.affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, China.|School of Animal, Rural and Environmental Sciences, Nottingham Trent University , Brackenhurst Campus, Southwell NG25 0QF, United Kingdom.
authors.forename: Gang
authors.initials: G
authors.lastname: Pan