@article{2c2b12e84582467baf41160bb20de65d,
title = "Stability and Free Radical Production for CO2 and H2 in Air Nanobubbles in Ethanol Aqueous Solution",
abstract = "In this study, 8% hydrogen (H2) in argon (Ar) and carbon dioxide (CO2) gas nanobubbles was produced at 10, 30, and 50 vol.% of ethanol aqueous solution by the high-speed agitation method with gas. They became stable for a long period (for instance, 20 days), having a high negative zeta potential (−40 to −50 mV) at alkaline near pH 9, especially for 10 vol.% of ethanol aqueous solution. The extended Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory was used to evaluate the nanobubble stability. When the nanobubble in ethanol alkaline aqueous solution changed to an acidic pH of around 5, the zeta potential of nanobubbles was almost zero and the decrease in the number of nanobubbles was identified by the particle trajectory method (Nano site). The collapsed nanobubbles at zero charge were detected thanks to the presence of few free radicals using G-CYPMPO spin trap reagent in electron spin resonance (ESR) spectroscopy. The free radicals produced were superoxide anions at collapsed 8%H2 in Ar nanobubbles and hydroxyl radicals at collapsed CO2 nanobubbles. On the other hand, the collapse of mixed CO2 and H2 in Ar nanobubble showed no free radicals. The possible presence of long-term stable nanobubbles and the absence of free radicals for mixed H2 and CO2 nanobubble would be useful to understand the beverage quality.",
keywords = "Carbon dioxide, Ethanol aqueous solution, Extended DLVO theory, Free radical, Hydrogen, Nanobubble stability",
author = "Zhenyao Han and Hiromi Kurokawa and Hirofumi Matsui and Chunlin He and Kaituo Wang and Yuezou Wei and Gjergj Dodbiba and Akira Otsuki and Toyohisa Fujita",
note = "Funding Information: bydecreasingtheFigure 10. bubble zetaModel ofpotentialnanobubble breakage by absolute value. changing pH from 9 to 5 and the production of radicals by decreasing the bubble zeta potential absolute value. 4. Conclusions The 8% hydrogen (H2) in argon (Ar) and carbon dioxide (CO2) gas nanobubbles with ethanolwereproducedThe 8% at 10,hy30,drogen (Hand 50 vol.%2) in arethanolgon (Araqueous) and carbon dioxsolutionibyde (COthe high2) gas naspeednobubbles with agitationmethodethawithnol were gas injection,produced at and10the, 30main, and 50 vfindingsol.% weretheanoasl follows:aqueous solution by the high speed agitation method with gas injection, and the main findings were as follows: potentialat• alkalineThe prepapH 9.red nanobubbles were stable for 20 days owing to a high negative zeta po-• When the pH of ethanol alkaline aqueous solution with nanobubbles was adjusted toacidicat• aroundWhen thepH 5,pHtheof ethzetaanol potentialalkalineofaqueous sonanobubbleslution waswith almostnanobzerubblo. eThes was adjusted to numbersofnanobubbleacidic at aroudecrnd peasedH 5,atthalmoste zeta pzeroteontcharial ofgen(pHanob5)ubwerblesewidentifiedas almostbyzero. The num-measuringtheirbenumbersrs of nanobusingubblthee decreparticleased trajectoryat almostmethodzero char(Nanoge (pH 5site).) were identified by meas-• The extended Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory was used to • The extendedDerjaguin, Landau, Verwey, and Overbeek (DLVO)theory was used to anditsinstabilityeva(attractionluate the nabetweennobubblebubbles)stabilityin(repuacidiclsion betconditions.ween bubbles) in alkaline conditions, The collapsed nanobubbles at zero charge generated slight free radicals detected using G-CYPMPOspintrapThe colreagentlapinsedelectrnanobonuspinbblesresonanceat zero ch(ESR)arge gespectrneratedoscoslight freepy. The producedradicals detected us-freeradicalsweringe superG-CYPMoxidePO spanionsin tratap collapsedreagent in8%eleHct2roinn spinAr nanobubblesresonance (ESR) and spectrohydroxylscopy. The pro-radicalsatcollapsedducedCO fre2e nanobubbles.radicals wereOnsuperoxidthe othere anhand,ions at cothe collapsedllapsed 8% mixedH2 inCOAr2 nandanobubbles and H2 in Ar nanobubbleshydroxyl radicashowedls atno frcollaee radicals.psed CO2 nanobubbles. On the other hand, the collapsed mixed Based on this study, a schematic model of nanobubble breakage and the production of radicalsbychangingBasesolutiond on thpHis stuwasdy, pra scheoposed.matic model These phenomenaof nanobubbandle breatheir understand-kage and the production ingwouldbeusefulof radtoicals byformulatechanhealthyging solution pHbeverages,wforas proposedexample.. These phenomena and their under-standing would be useful to formulate healthy beverages, for example. Author Contributions: Conceptualization, Z.H. and T.F.; methodology, H.K. and H.M.; validation, Author Contributions: Conceptualization, Z.H. and T.F.; methodology, H.K. and H.M.; validation, writing—originalH.K.draftand Hpreparation,.M.; investigZ.H.ationand, C.TH.,.F.;K.Wwriting—r., and Aeview.O.; resouandrceediting,s, Z.H. anG.D.d G.andD.; data A.O.curation, Y.W.; supervision, T.F.;wprriotijnegc—t aodrmigiinniaslt rdartaioftnp, rYe.pWa.r,aCti.oHn.,, Zan.Hd. Kan.Wd .TA.Fl.l; awurtihtionrgs—harevveierewa danadndedaigtirnege,dGt.oD. and A.O. su- the published veprseirovnisoiofnth, eT.mF.a; npuroscjercipt ta.dministration, Y.W., C.H., and K.W. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Natural Science Foundation of China, grant number NSFC (21976039). Funding: This research was funded by the Natural Science Foundation of China, grant number NSFC (21976039). Data Availability Statement: The data presented in this study are available on request from the corresponding author. Publisher Copyright: {\textcopyright} 2022 by the authors. Licensee MDPI, Basel, Switzerland.",
year = "2022",
month = jan,
day = "1",
doi = "10.3390/nano12020237",
language = "English",
volume = "12",
journal = "Nanomaterials",
issn = "2079-4991",
publisher = "Multidisciplinary Digital Publishing Institute (MDPI)",
number = "2",
}