Non-equilibrium plasmas generate highly reactive species at low temperatures [1]. New so-called cold atmospheric pressure plasma sources operated with air or noble gases allow surface treatment at ambient conditions and can thus induce novel chemistry into liquid systems such as nano-material precursors. A major role in these plasma liquid systems is attributed to liquid interfaces (see fig. 1), mediating the plasma interaction effect [2]. Plasma liquid systems are increasingly studied for the synthesis of novel materials [3, 4].

Non-equilibrium plasmas synthesise materials at low temperatures and generate nanoparticles without the use of surfactants. These aspects are advantageous over conventional equilibrium chemistry processes. The unique property of non-equilibrium plasmas is that they generate atomic species and radicals in high concentration. Their high reactivity induces high concentration gradients in space and time, making the plasma liquid systems intricate to investigate. The complexity of the plasma caused chemical reaction kinetics is largely unknown and the focus of present discussions [6]. Open questions still remain e.g. on the flux of species and especially on processes at the plasma-liquid interface. Small dimensions of the interface region and fast dynamics of the interfacial processes require the development and application of novel diagnostic techniques to study these plasma liquid systems.

This presentation will describe examples of laser based diagnostic techniques that allow probing flow fields, reactivity, species composition, and electric fields in plasma liquid systems. It will be shown, how diagnostics along with model calculations yield insight into reactive turbulent multiphase systems.

References

[1] X. Lu, G.V. Naidis, M. Laroussi, S. Reuter, D.B. Graves, K. Ostrikov, Reactive species in non-equilibrium atmospheric-pressure plasmas: Generation, transport, and biological effects, Physics Reports, 630 (2016) 1-84.

[2] P.J. Bruggeman, M.J. Kushner, B.R. Locke, J.G.E. Gardeniers, W.G. Graham, D.B. Graves, R.C.H.M. Hofman-Caris, D. Maric, J.P. Reid, E. Ceriani, D. Fernandez Rivas, J.E. Foster, S.C. Garrick, Y. Gorbanev, S. Hamaguchi, F. Iza, H. Jablonowski, E. Klimova, J. Kolb, F. Krcma, P. Lukes, Z. Machala, I. Marinov, D. Mariotti, S. Mededovic Thagard, D. Minakata, E.C. Neyts, J. Pawlat, Z.L. Petrovic, R. Pflieger, S. Reuter, D.C. Schram, S. Schröter, M. Shiraiwa, B. Tarabová, P.A. Tsai, J.R.R. Verlet, T. von Woedtke, K.R. Wilson, K. Yasui, G. Zvereva, Plasma–liquid interactions: a review and roadmap, Plasma Sources Science and Technology, 25 (2016) 053002.

[3] J. Schäfer, K. Fricke, F. Mika, Z. Pokorná, L. Zajíčková, R. Foest, Liquid assisted plasma enhanced chemical vapour deposition with a non-thermal plasma jet at atmospheric pressure, Thin Solid Films, 630 (2017) 71-78.

[4] D. Mariotti, R.M. Sankaran, Microplasmas for nanomaterials synthesis, Journal of Physics D: Applied Physics, 43 (2010) 323001.

[5] S. Reuter, T.v. Woedtke, K.-D. Weltmann, The kINPen – a Review on Physics and Chemistry of the Atmospheric Pressure Plasma Jet and its Applications, J. Phys D, accepted (2017).

[6] I. Adamovich, S.D. Baalrud, A. Bogaerts, P.J. Bruggeman, M. Cappelli, V. Colombo, U. Czarnetzki, U. Ebert, J.G. Eden, P. Favia, D.B. Graves, S. Hamaguchi, G. Hieftje, M. Hori, I.D. Kaganovich, U. Kortshagen, M.J. Kushner, N.J. Mason, S. Mazouffre, S.M. Thagard, H.R. Metelmann, A. Mizuno, E. Moreau, A.B. Murphy, B.A. Niemira, G.S. Oehrlein, Z.L. Petrovic, L.C. Pitchford, Y.K. Pu, S. Rauf, O. Sakai, S. Samukawa, S. Starikovskaia, J. Tennyson, K. Terashima, M.M. Turner, M.C.M. van de Sanden, A. Vardelle, The 2017 Plasma Roadmap: Low temperature plasma science and technology, Journal of Physics D: Applied Physics, 50 (2017) 323001.