IOP Plasma Sources Science and Technology Plasma Sources Science and Technology Plasma Sources Sci. Technol. Plasma Sources Sci. Technol. 25 (2016) 053002 (59pp) doi:10.1088/0963-0252/25/5/053002 25 Review 2016 Plasma–liquid interactions: a review © 2016 IOP Publishing Ltd and roadmap PSST P J Bruggeman1, M J Kushner2, B R Locke3, J G E Gardeniers4, 053002 W G Graham5, D B Graves6, R C H M Hofman-Caris7, D Maric8, J P Reid9, E Ceriani10, D Fernandez Rivas4, J E Foster11, S C Garrick1, Y Gorbanev12, 13 14 15 16 15 16 P J Bruggeman et al S Hamaguchi , F Iza , H Jablonowski , E Klimova , J Kolb , F Krcma , P Lukes17, Z Machala18, I Marinov19, D Mariotti20, S Mededovic Thagard21, D Minakata22, E C Neyts23, J Pawlat24, Z Lj Petrovic8,25, R Pflieger26, S Reuter15, D C Schram27, S Schröter28, M Shiraiwa29, B Tarabová18, P A Tsai30, J R R Verlet31, T von Woedtke15, K R Wilson32, K Yasui33 34 Printed in the UK and G Zvereva 1 Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, PSST Minneapolis, MN 55455, USA 2 Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave, Ann Arbor, MI 48109-2122, USA 10.1088/0963-0252/25/5/053002 3 Department of Chemical and Biomedical Engineering, Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32309, USA 4 Mesoscale Chemical Systems, MESA + , Institute for Nanotechnology, University of Twente, 0963-0252 PO Box 217, 7500AE Enschede, The Netherlands 5 Mathematics and Physics, Queen’s University Belfast, University Road, Belfast, BT7 1NN, UK 6 5 Chemical and Biomolecular Engineering, University of California—Berkeley, 201 Gilman, Berkeley, CA 94720-1460, USA 7 KWR Watercycle Research Institute, PO Box 1072, 3430BB Nieuwegein, The Netherlands 8 Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia 9 School of Chemistry, University of Bristol, Cantock’s Close, Clifton, Bristol, BS8 1TS, UK 10 Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo, 1 35131 Padova, Italy 11 Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd, Ann Arbor, MI 48109-2104, USA 12 Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK 13 Center for Atomic and Molecular Physics, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan 14 School of Electronic, Electrical and Systems Engineering, Loughborough University, Epinal Way, Loughborough Leicestershire, LE11 3TU, UK 15 Leibniz Institute for Plasma Science and Technology, INP Greifswald, Felix Hausdorff-Str. 2, 17489, Greifswald, Germany 16 Faculty of Chemistry, Brno University of Technology, Purkynova 118, 61200 Brno, Czech Republic 17 Pulse Plasma Systems Department, Institute of Plasma Physics CAS, v.v.i., Za Slovankou 1782-3, Prague 8, 182 00, Czech Republic 18 Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska dolina, 842 48 Bratislava, Slovakia 19 Laboratoire de Physique des Plasmas, Ecole Polytechnique, route de Saclay, F-91128, Palaiseau, Cedex, France 20 Nanotechnology and Integrated Bioengineering Centre (NIBEC), University of Ulster, Newtownabbey BT37 0QB, UK 21 Department of Chemical and Biomolecular Engineering, Clarkson University, PO Box 5705, Potsdam, NY 13699-5705, USA 22 Department of Civil and Environmental Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA 23 Department of Chemistry, Research Group PLASMANT, University of Antwerp, Universiteitsplein1, BE-2610 Antwerp-Wilrijk, Belgium 0963-0252/16/053002+59$33.00 1 © 2016 IOP Publishing Ltd Printed in the UK Plasma Sources Sci. Technol. 25 (2016) 053002 Review 24 Electrical Engineering and Computer Science, Lublin University of Technology, 38A Nadbystrzycka str., 20-618 Lublin, Poland 25 Serbian Academy of Sciences and Arts, Belgrade, Serbia 26 Institut de Chimie Séparative de Marcoule, ICSM UMR 5257, CNRS/CEA/UM/ENSCM, Centre de Marcoule, Batiment 426, BP 17171, F-30207 Bagnols-sur-Ceze Cedex, France 27 Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600 MB, Eindhoven, The Netherlands 28 Department of Physics, York Plasma Institute, University of York, Heslington, York, YO10 5DD, UK 29 Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany 30 Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 2G8, Canada 31 Department of Chemistry, Durham University, Lower Mountjoy, South Road, Durham, DH1 3LE, UK 32 Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-8176 USA 33 National Institute of Advanced Industrial Science and Technology (AIST), Moriyama ku, Nagoya 463 8560, Japan 34 State University of Civil Aviation, 38, Pilotov Str., St. Petersburg, 196210, Russia E-mail: [email protected] Received 18 January 2016, revised 2 May 2016 Accepted for publication 8 June 2016 Published 30 September 2016 Abstract Plasma–liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non- equilibrium plasmas. Keywords: non-equilibrium plasma, plasma–liquid interaction, diagnostics, modeling, reaction rate data sets, multiphase chemistry, photolysis (Some figures may appear in colour only in the online journal) 1. Introduction on microsecond pulsed discharges in water have addressed these topics [7]. Plasma–liquid interactions are becoming an increasingly The field of analytical chemistry often uses plasma devices important topic in the field of plasma science and technology. to prepare samples or as a sampling process for the analyses of The interaction of non-equilibrium plasmas with a liquid state solutions. These techniques are typically based on glow dis- is important in many applications ranging from environmental charges with liquid electrodes [8], inductively coupled plas- remediation to material science and health care. Cavendish’s mas [9] and a variety of corona, dielectric barrier discharges famous work ‘experiments on air’ from 1785 might be the and glow discharges as ionization sources for mass spectrom- first report involving plasma–liquid interaction and dealt with etry [10]. The emphasis in these uses of plasmas is typically the production of nitric acid by an electric spark in air [1]. not to intentionally transfer reactivity from the plasma into Experiments dealing with the interaction of plasmas and liq- the liquid for the purposes of making a more reactive liquid. uids in the context of electrochemistry date back more than The plasma community has greatly benefited from this work. 100 years ago [2]. Up to about 30 years ago, the main focus The topics addressed in this manuscript build on this knowl- in the field of plasmas in and in contact with liquids was on edge base produced by the analytical chemistry community. glow discharge electrolysis [3] and the study of breakdown of However, the focus here is on plasma–liquid interactions and dielectric liquids for high-voltage switching [4]. These works particularly on the physical and chemical mechanisms lead- were followed by a strong emphasis on environmental driven ing to complex feedback between the plasma and liquid at the research exploiting the fact that plasmas in and in contact with plasma–liquid interface resulting in reactivity in the liquid. liquids are rich sources of reactive species, such as •OH, O• During the last 15 years, the focus of research on the inter- and H2O2, and UV radiation [5]. Plasmas are, in fact, a form actions of plasmas with liquids has broadened to address a of advanced oxidation technology enabling the breakdown of variety of application areas, including electrical switching organic and inorganic compounds in water [6]. Many studies [4], analytical chemistry [8, 10], environmental remediation 2 Plasma Sources Sci. Technol. 25 (2016) 053002 Review Figure 1. Schematic diagram of some of the most important species and mechanisms for an argon/humid air plasma in contact with water. Adapted with permission from [24], copyright 2014 IOP Publishing. (water treatment and disinfection) [6], material synthesis that electrical breakdown in water occurs through forma- (nanoparticles) [11], material processing (photoresist removal, tion of bubbles or in pre-existing voids, some recent results plasma-polishing, polymer functionalization) [12, 13], chemi- suggest that breakdown can occur without a phase change cal synthesis (H2O2, H2) [14], sterilization and medical appli- [23]. Plasmas in liquids have been investigated using imag- cations (plasma induced wound healing, tissue ablation, blood ing and optical emission spectroscopy, techniques that have coagulation, lithotripsy) [5, 15]. These exciting opportunities enabled measuring basic plasma parameters including dis- have challenged the plasma community with multidiscipli- charge morph ology, gas temperature, electron density, and nary scientific questions. In addition to specialized review excitation temperatures. Increasing efforts have recently been articles, two broader reviews focusing on the applications and devoted to modeling, but there