As strong oxidizers, OH radicals are crucial for water treatment applications involving plasma-liquid interactions. Hydrodynamic cavitation-based systems show promise for disinfection and micropollutant removal at flow rates of several m3/h. Knowledge of the spatial distribution of OH is limited. However, this is vital for enhancing system efficiency. This study maps the spatial distribution of OH generated by electric discharge in a hydrodynamic cavitation cloud. Using Luminol as a chemiluminescent probe, the study addresses challenges related to probe stability and luminescence lifetime in a dynamic cavitation environment. Luminescence decay time was assessed with a fast-frame camera, and spatial mapping was conducted by using an ICCD camera with an optical filter. Strong emission was observed at the collapsing end of the cavitation cloud and within the discharge channel, indicating the production and transport of OH into the liquid.

Brno University of Technology Faculty of Mechanical Engineering 5 Kaplan Department of Fluid Engineering Technická 2896 2 616 69 Brno Czech Republic

Department of Plasma Physics and Technology Faculty of Science Masaryk University Kotlářská 2 611 37 Brno Czech Republic

Institute of Botany of the Czech Academy of Sciences Lidická 25 27 602 00 Brno Czech Republic

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Khan P., Idrees D., Moxley M. A., Corbett J. A., Ahmad F., Von Figura G., Sly W. S., Waheed A., Hassan M. I.. Luminol-based chemiluminescent signals: Clinical and non-clinical application and future uses. Appl. Biochem. Biotechnol. 2014;173:333–355. doi: 10.1007/s12010-014-0850-1. PubMed DOI PMC

Giussani A., Farahani P., Martínez-Muñoz D., Lundberg M., Lindh R., Roca-Sanjuán D.. Molecular Basis of the Chemiluminescence Mechanism of Luminol. Chem. - A Eur. J. 2019;25:5202–5213. doi: 10.1002/chem.201805918. PubMed DOI

Uchida S., Satoh Y., Yamashiro N., Satoh T.. Determination of hydrogen peroxide in water by chemiluminescence detection, (II) theoretical analysis of luminol chemiluminescence processes. J. Nucl. Sci. Technol. 2004;41:898–906. doi: 10.1080/18811248.2004.9715562. DOI

Lu C., Song G., Lin J. M.. Reactive oxygen species and their chemiluminescence-detection methods. TrAC - Trends Anal. Chem. 2006;25:985–995. doi: 10.1016/j.trac.2006.07.007. DOI

Lucas M., Cardoni A., McCulloch E., Hunter G., MacBeath A.. Applications of Power Ultrasonics in Engineering. Appl. Mech. Mater. 2008;13–14:11–20. doi: 10.4028/www.scientific.net/AMM.13-14.11. DOI

Perrin L., Colombet D., Ayela F.. Comparative study of luminescence and chemiluminescence in hydrodynamic cavitating flows and quantitative determination of hydroxyl radicals production. Ultrason. Sonochem. 2021;70:105277. doi: 10.1016/j.ultsonch.2020.105277. PubMed DOI PMC

Schüttler S., Jolmes L., Jeß E., Tschulik K., Golda J.. Validation of in situ diagnostics for the detection of OH and H2O2 in liquids treated by a humid atmospheric pressure plasma jet. Plasma Process. Polym. 2024;21:2300079. doi: 10.1002/ppap.202300079. DOI

Schüttler S., Schöne A. L., Jeß E., Gibson A. R., Golda J.. Production and transport of plasma-generated hydrogen peroxide from gas to liquid. Phys. Chem. Chem. Phys. 2024;26:8255–8272. doi: 10.1039/D3CP04290A. PubMed DOI

Shirai N., Matsuda Y., Sasaki K.. Visualization of short-lived reactive species in liquid in contact with atmospheric-pressure plasma by chemiluminescence of luminol. Appl. Phys. Express. 2018;11:026201. doi: 10.7567/APEX.11.026201. DOI

Shirai N., Suga G., Sasaki K.. Correlation between gas-phase OH density and intensity of luminol chemiluminescence in liquid interacting with atmospheric-pressure plasma. J. Phys. D. Appl. Phys. 2019;52:39LT02. doi: 10.1088/1361-6463/ab2ff2. DOI

Locke B. R., Shih K.-Y. Y.. Review of the methods to form hydrogen peroxide in electrical discharge plasma with liquid water. Plasma Sources Sci. Technol. 2011;20:034006. doi: 10.1088/0963-0252/20/3/034006. DOI

Čech J., St’ahel P., Prokeš L., Trunec D., Horňák R., Rudolf P., Maršálek B., Maršálková E., Lukeš P., Lavrikova A.. et al. CaviPlasma: parametric study of discharge parameters of high-throughput water plasma treatment technology in glow-like discharge regime. Plasma Sources Sci. Technol. 2024;33:115005. doi: 10.1088/1361-6595/ad7e4e. DOI

Foster J. E.. Plasma-based water purification: Challenges and prospects for the future. Phys. Plasmas. 2017;24:055501. doi: 10.1063/1.4977921. DOI

Locke B. R., Thagard S. M., Lukes P.. Recent Insights Into Interfacial Transport and Chemical Reactions of Plasma Generated Species in Liquid. Plasma Process. Polym. 2025;22:2400207. doi: 10.1002/ppap.202400207. DOI

Pereira T. C., Flores E. M. M., Abramova A. V., Verdini F., Calcio Gaudino E., Bucciol F., Cravotto G.. Simultaneous hydrodynamic cavitation and glow plasma discharge for the degradation of metronidazole in drinking water. Ultrason. Sonochem. 2023;95:106388. doi: 10.1016/j.ultsonch.2023.106388. PubMed DOI PMC

Zupanc M., Primc G., Dular M., Petkovšek M., Roškar R., Zaplotnik R., Trontelj J.. Proof-of-concept for removing micropollutants through a combination of sub-atmospheric-pressure non-thermal plasma and hydrodynamic (super)­cavitation. Ultrason. Sonochem. 2024;111:107110. doi: 10.1016/j.ultsonch.2024.107110. PubMed DOI PMC

Maršálek B., Maršálková E., Odehnalová K., Pochylý F., Rudolf P., Stahel P., Rahel J., Čech J., Fialová S., Zezulka Š.. Removal of Microcystis aeruginosa through the Combined Effect of Plasma Discharge and Hydrodynamic Cavitation. Water. 2020;12:8. doi: 10.3390/w12010008. DOI

Čech J., St’ahel P., Ráhel’ J., Prokeš L., Rudolf P., Maršálková E., Maršálek B.. Mass Production of Plasma Activated Water: Case Studies of Its Biocidal Effect on Algae and Cyanobacteria. Water. 2020;12:3167. doi: 10.3390/w12113167. DOI

Rudolf, P. ; Pochylý, F. ; St’ahel, P. ; Ráhel, J. ; Čech, J. ; Maršálek, B. . Apparatus for purifying liquids and a method for purifying liquids using this apparatus. PCT Application 2021, WO2021/115498.

Odehnalová K., Čech J., Maršálková E., St’ahel P., Mayer B., Santana V. T., Rudolf P., Maršálek B.. Exploring the dynamics of reactive oxygen species from CaviPlasma and their disinfection and degradation potential – the case of cyanobacteria and cyanotoxins. Environ. Sci. Pollut. Res. 2025;32:849–863. doi: 10.1007/s11356-024-35803-4. PubMed DOI PMC

Janda M., Stancampiano A., di Natale F., Machala Z.. Short Review on Plasma–Aerosol Interactions. Plasma Process. Polym. 2025;22:2400275. doi: 10.1002/ppap.202400275. DOI

Wasselin-Trupin V., Baldacchino G., Bouffard S., Balanzat E., Gardès-Albert M., Abedinzadeh Z., Jore D., Deycard S., Hickel B.. A New Method for the Measurement of Low Concentrations of OH/O2 ‑ Radical Species in Water by High-LET Pulse Radiolysis. A Time-Resolved Chemiluminescence Study. J. Phys. Chem. A. 2000;104:8709–8714. doi: 10.1021/jp000462z. DOI

Lyon R. F., Hubel P. M.. Eyeing the Camera: Into the Next Century. Color Imaging Conf. 2002;10:349–355. doi: 10.2352/CIC.2002.10.1.art00064. DOI

Berra E., Gibson-Poole S., MacArthur A., Gaulton R., Hamilton A.. Estimation of the spectral sensitivity functions of un-modified and modified commercial off-the-shelf digital cameras to enable their use as a multispectral imaging system for UAVs. Int. Arch. Photogramm. Remote Sens. Spat. Inf. Sci. 2015;XL-1/W4:207–214. doi: 10.5194/isprsarchives-XL-1-W4-207-2015. DOI

Pérez-García Á., Rodríguez-Molina A., Hernández E., Vera L., López J. F.. Development of Low-Cost Multi-Spectral Cameras for Precision Agriculture. IEEE Int. Geosci. Remote Sens. Symp. 2023:3466–3469. doi: 10.1109/IGARSS52108.2023.10282072. DOI

Bruggeman P., Leys C.. Non-thermal plasmas in and in contact with liquids. J. Phys. D. Appl. Phys. 2009;42:053001. doi: 10.1088/0022-3727/42/5/053001. DOI

Gorbanev Y., O’Connell D., Chechik V.. Non-Thermal Plasma in Contact with Water: The Origin of Species. Chem. - A Eur. J. 2016;22:3496–3505. doi: 10.1002/chem.201503771. PubMed DOI PMC

Suslick K. S., Eddingsaas N. C., Flannigan D. J., Hopkins S. D., Xu H.. Extreme conditions during multibubble cavitation: Sonoluminescence as a spectroscopic probe. Ultrason. Sonochem. 2011;18:842–846. doi: 10.1016/j.ultsonch.2010.12.012. PubMed DOI