BIOPLASMAS & PLASMAS WITH LIQUIDS - Joint Conference of COST ACTIONS TD1208 “Electrical discharges with liquids for future
applications” & MP1101 Biomedical Applications of Atmospheric Pressure Plasma Technology, Bertinoro, Italy, 13th-17th September 2015
Spectroscopic diagnostics and bactericidal efficacy of DBD helium
plasma jets
M. M. Kuraica1, B. M. Obradović1, V. V. Kovačević1, I. B. Krstić1, G. B.
Sretenović1, B. Vuković2, Z. Tambur3 and D. Cenić-Milošević2
1
Faculty of Physics, University of Belgrade, Studentski trg 12, 11000 Belgrade, Serbia
2
Faculty of Stomatology in Pančevo, Žarka Zrenjanina 179, 26000 Pančevo, Serbia
3
Military Medical Academy, Crnotravska 17, 11000 Belgrade, Serbia
Two types of dielectric barrier discharge (DBD) plasma jets in helium have been investigated. The first one
(JET I) consists of two copper electrodes tightly wrapped around a glass tube. The lower electrode is placed 1
cm above the tube’s end and it is attached to high voltage, while the upper one is grounded. The second
plasma jet (JET II) has one copper electrode wrapped around the glass tube which is connected to high
voltage. The other, a grounded copper electrode is placed downstream at a variable distance from the nozzle.
Both plasma jets work with helium and both are supplied by sinusoidal high voltages with frequency of
12 kHz [1]. They operate in bullet/streamer mode with emission of a single plasma bullet per positive half
period of applied voltage.
Plasma jets have been studied by optical emission spectroscopy and electrical measurements. Spatially and
temporally resolved spectroscopic measurements are performed by means of ICCD camera coupled with a
one meter monochromator. The overview spectra are recorded in order to identify excited chemical species.
The gas temperature in plasma jet is determined from the rotational temperatures of molecular bands of OH
and N2+. Gas temperature is found to be about 310 K which is favourable for biomedical applications [2].
Spatio-temporal evolutions of plasma jets are followed through emission development of He (23P–33S) line at
706.5 nm. Discharge in the effluent of JET I develops analogously to cathode directed streamer, while the
discharge between nozzle and grounded electrode exhibits all features of a microdischarge in air. The plasma
bullet velocities for both jets are obtained from the ICCD images. It was found that the discharge
configuration crucially affects the streamer/bullet velocity. In case of JET I plasma bullet has a maximal
velocity of 10 km/s, while in case of JET II it reaches 40 km/s, for the same applied voltage [1]. Using Stark
polarization spectroscopy based method, electric field strength developments for both jets have been
determined [3]. Similar to the behaviour of plasma bullet velocities, the maximal electric field strength in
plasma bullet of JET II is twice higher than in the case of JET I. The electric field reaches value of 10 kV/cm
in the plasma bullet generated in first plasma jet configuration, while it has a maximal value of about 20
kV/cm in the plasma bullet of plasma jet with grounded electrode downstream the nozzle. Plotting a graph
of plasma bullet velocity in dependence on electric field strength the correlation between these two quantities
become more obvious. The graphs clearly show that the bullet velocity is governed by the electric field in the
bullet head.
After complete plasma diagnostics, the antimicrobial efficiency of the plasma jet is investigated. The effect of
plasma jet on inactivation of five pathogens is presented in this work. This is a part of broader study where
antimicrobial efficiency of plasma jet is tested on fifteen different, most common microorganisms in human
mouth flora. In that study, the antimicrobial efficacy of plasma jet will be compared with efficacy of plasma
activated water using water falling film DBD reactor. In this work we present preliminary results of treatment
of planktonic samples of following bacteria: Staphylococcus aureus, Streptococcus sangvinis, Pseudomonas
aeruginosa, Enterococcus faecalis and Veillonella parvula. The suspensions of bacteria had average initial
concentration of 108 CFU/mL. In this study the treatment time was a variable parameter and planktonic
samples are treated for 1, 3, 5 and 7 minutes. For all treated species the inactivation efficiency of plasma jet of
at least 4-5 orders of magnitude is reached in 5-7 minutes of treatment.
[1] G. B. Sretenović et al. J. Phys. D. Appl. Phys. 47 (2014) 102001.
[2] G. B. Sretenović et al. IEEE Trans. Plasma Sci. 40 (2012) 2870.
[3] G. B. Sretenović et al. Appl. Phys. Lett. 99 (2011) 161502.