On phenomena in ionized gases
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- Bu sahifa navigatsiya:
- Free-standing graphene: synthesis and functionalization using plasma- based methods
- DBD plasma jet in helium, argon and nitrogen: energy balance and bactericidal activity
- 2. Experimental setup and procedure
- 4. References
- Efficacy of plasma-generated ozone in bioburden decontamination
- 3. References
- Surface-wave-sustained plasma for model biological systems treatment
- 2. Results and discussion
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References [1] I.-L. Velicu, V. Tiron, B.-G. Rusu, G. Popa, Surf. Coat. Technol. (2017) doi:10.1016/j.surfcoat. 2016.11.001. [2] I.-L. Velicu, V. Tiron, C. Porosnicu, I. Burducea, N. Lupu, G. Stoian, G. Popa, D. Munteanu, Appl. Surf. Sci. (2017), doi: 10.1016/j.apsusc.2017.01.067 [3] V. Tiron, I.-L. Velicu, D. Stanescu, H. Magnan and L. Sirghi, Surf. Coat. Technol. (2017) doi: 10.1016/j.surfcoat.2016.11.087. 83
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Fig 1 – SEM image of FSGs.
A. Dias P 1,2
P , J. Berndt P 2
, E. Kovacevic 2 P , C. Pattyn P 2 P , T. Strunskus 3 , J. Henriques 1 , E. Tatarova 1
P 1 P
P
P
3 Institute for Materials Science - Multicomponent Materials, Christian-Albrechts-Universität zu Kiel, Germany
In the present work, an atmospheric pressure microwave plasma-based method is used to synthesize free-standing graphene sheets (FSGs). The FSGs were then transferred to several types of substrates using different graphene suspensions. The results allowed to demonstrate the possibility to use graphene in future flexible nanodevices. Subsequently, the deposited graphene sheets were successfully N-functionalized and polymerized with aniline (ANI) using a capacitively coupled plasma at low pressure. The samples were characterized by transmission and scanning electron microscopy (TEM and SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and by contact angle technique.
A critical requirement for the mass production of graphene is the control of the synthesis processes. So far, conventional methods used for the synthesis of these 2D materials present several drawbacks most importantly the quite limited control on the assembly process. Moreover, N 2 functionalization of graphene is one of the key topics in materials research, since functionalized graphene finds extensive application in polymer science and technology due to its extraordinary electrochemical properties (eg. polymer-graphene nanocomposites). Therefore, the aim of this work is to find a simple method for the subsequent deposition and treatment of free-standing graphene sheets.
At first an atmospheric microwave plasma was used to synthesize FSGs [1-5]. To this end, a hydrocarbon precursor was injected into the microwave plasma
environment, where
decomposition processes take place. The main part of the solid carbon is gradually dragged into the outlet plasma stream, where the graphene sheets assemble and grow. A power of 2 kW was applied, injecting Ar as background gas and ethanol as precursor with a ratio of 10:1. The collected FSGs (see Fig.1) are deposited using a simple dispersion method, which enable the deposition on various substrates. Distilled water and methanol were used as solvents in this process. Subsequently, N 2 plasma
treatment [6] was performed to turn graphene into a hydrophilic surface, enabling for example the adhesion of biomolecules. The N 2 plasma treatment consists on placing the samples in a remote zone of a capacitively coupled plasma (CCP) for different processing times. A RF power of 8 W was applied at 13.56 MHz, while maintaining 0.1 mbar pressure in the chamber. The
same experimental set up was also used
for the
deposition of thin films onto the graphene flakes. These experiments were performed with aniline as a precursor for the thin film synthesis. The resulting nanostructures were characterized by SEM and TEM, Raman spectroscopy, XPS, NEXAFS and contact angle measurements. Plasma characterization was also performed by mass spectrometry and optical emission spectroscopy.
References [1] E. Tatarova, A. Dias et al. Nova Science Publishers, ISBN: 978-1-63485-214-2 (2016). [2] E. Tatarova, N. Bundaleska et al. Plasma Sources Sci. Technol. 23, 063002 (2014). [3] E. Tatarova, J. Henriques, C.C. Luhrs, A. Dias, et al. Phys. Lett. 103, 134101 (2013). [4] E. Tatarova, A. Dias et al. J. Phys. D: Appl. Phys. 47, 385501 (2014).
[5] A. Dias, N. Bundaleski et al. J. Henriques J. Phys. D: Appl. Phys. 49, 055307 (2016).
[6] E. Kovačevic ́, J. Berndt et al. J. Appl. Phys. 105, 104910 (2009). Acknowledgements Work partially funded by Portuguese FCT - Fundação para a Ciência e a Tecnologia, under project
UID/FIS/50010/2013 and
grant SFRH/BD/52413/2013 (PD-F APPLAuSE) and by French Regional Research Agency through the project APR Capt’Eau and ARD PIVOT.
Topic 14 84 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
DBD plasma jet in helium, argon and nitrogen: energy balance and bactericidal activity
O. Stepanova 1 , M. Pinchuk U 2
3 , O. Rybalchenko 1 , O. Orlova 1 , A. Astafiev 2 ,
1
Saint Petersburg State University, Saint Petersburg, Russia 2 Institute for Electrophysics and Electric Power of Russian Academy of Sciences, Saint Petersburg, Russia 3 Moscow Power Engineering Institute, National Research University , Moscow, Russia
The paper presents the experimental evaluations of bactericidal activ ity of dielectric-barrier discharge (DBD) plasma jets in helium, argon and nitrogen applied to E. coli cells freshly- inoculated on an agar surface in a grounded Petri dish. Sinusoidal high-voltage signals with the frequency of 7.5, 32 and 84 kHz were used to supply a plasma generator. The energy deposited into a discharge cell is distributed between a discharge region and a plasma jet. A balance of the energy changes with the varying of the voltage frequency. The effect of the energy balance of the system “DBD – plasma jet” on the dimensions and purity of the zones of bacterial inhibition has been considered. The biggest and the purest inhibition zones were obtained in the case of argon plasma jet. Inhibition zones formed under the nitrogen plasma jet have a heavy growth of bacteria near their boundaries. Helium plasma jets create relatively small, but pure inhibition zones.
A dielectric-barrier discharge (DBD) plasma jet is usually formed in a noble gas flow which is passed through a discharge gap. Two distinct spatial regions, a main discharge and a plasma jet, can be distinguished [1]. The energy distribution between the two regions depends on whether a treated object is grounded or not. This paper presents the experimental evaluations of bactericidal activity of DBD plasma jets in helium, argon and nitrogen for the case of the grounding of an additional electrode which is located under a Petri dish with freshly- inoculated bacteria.
To supply a DBD plasma jet generator, high- voltage sinusoidal power suppliers with a frequency of 7.5, 32 and 84 kHz were used. An electrical scheme of the experimental setup was equipped with the electrical parameters diagnostics. The energy deposited into the discharge and the energy transported to the Petri dish by the plasma jet was calculated using charge–voltage Lissajous figures. To investigate the effect of energy balance on the bactericidal activity of the
plasma jet,
Escherichia сoli M17 cells freshly-inoculated on the agar nutrient medium in Petri dishes were used. The distance between the outlet of the discharge tube and agar surface was 10 mm. The duration of all treatments was 2 min.
Bactericidal activity of the plasma jet was estimated according to the dimensions and purity of the zones of bacterial inhibition. Analysis was conducted for the zones which did not undergo heating up to the agar melting, so the modes of treatments by the jet which is close to the transition to an arc were excluded. The biggest (15-25 mm in a diameter) and the purest inhibition zones were obtained in the case of the argon plasma jet. But the argon plasma jet is easily transferred into the arc with the increasing of the voltage frequency. Inhibition zones formed under the nitrogen plasma jet are relatively large (about 15 mm on the average), but they have a heavy growth of bacteria near their boundaries - they are not pure. Helium plasma jets create small (maximal diameter is 10 mm), but pure inhibition zones. Various balances of the deposited energy have been obtained at the applying of voltages with different voltage frequencies. For example, for the helium plasma jet at frequencies of 7.5 and 32 kHz the energy deposited into the jet is higher than the amount of energy deposited into the discharge, whereas at 84 kHz this ratio is changed. For the argon plasma jet discharge energy is higher than jet’s energy for the all analyzed values of voltage frequency. The
work was
partially supported by Saint Petersburg State University (grant no. 0.37.218.2016) and
the Russian
Foundation for Basic Research (grant no. 16-08- 00870).
4. References [1] A. Shashurin, M. Keidar. Phys. Plasmas 22 (2015) 122002. 17
85 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
DBD plasma
source Target chamber Efficacy of plasma-generated ozone in bioburden decontamination
M. Pajak P 1 P , R. Barton 2 , D. A. Diver 1 , H. E. Potts 1,2 , A. Smith 3
P 1 P
P
P
3 Institute of Infection, Immunity and Inflammation, University of Glagow, Glasgow G12 8QQ, UK
We show recent results of the efficacy of ozone, generated by cold plasma DBD discharge system, in the reduction of bioburden in various practical contexts. The patented plasma system is designed to generate ozone in situ, without endangering the operator, using the ambient air; in one configu- ration, the system can generate significant ozone concentrations in sealed packages from the out- side, without compromising the seal. We demonstrate the performance of this system in a variety of contexts, with particular relevance to high level decontamination of medical devices, and also pos- sible applications in disinfecting plumbing components. Only the plasma effluent impinges on the target: the plasma does not make contact. Our experiments show effective biocidal, virucidal, my- cobactericidal and fungicidal treatments are possible, both in vitro and in realistic conditions.
Cold plasma generation of ozone has a long his- tory, primarily in water treatment plants as an alter- native to chlorination [1]. Ozone is a very strong oxidising agent and consequently is an effective biocide. However, it is a difficult chemical to han- dle, because not only is it extremely hazardous to humans, it has a short half-life (a matter of hours at room temperature) and so must be generated on demand. 2.1 Plasma device The novelty in our approach lies in the design of a plasma system that allows ozone to be generated inside sealed containers, but by an electrode system imposed from the outside [2]. In this system, there is no requirement to open the package for access, nor is any feedstock gas required. The electrode system attaches to the flexible package surface by suction, effectively making the package material an extra dielectric layer. Electric fields are expressed from the electrodes through the package to strike a low- energy plasma in the interior, which then generates ozone. The circulation of that ozone around the package interior ensures any target contained within is exposed to a powerful biocide. Typically, the ozone levels can reach in excess of 1000ppm in 20s, for 1 litre packages. The system used is shown in Figure 1: treatment targets are packaged and placed inside the chamber, attaching to the electrode plate via vacuum suction. Treatment cycles are generally 100s, with the target left for 1 hour before retrieval and testing: this allows the ozone to decay naturally, and prolongs the exposure of the bioburden to the ozone. This separation of plasma treatment time and the target dwell time is very practical: multiple, separate targets can be sequentially treated with a single plasma source, and the targets remain safely packaged whilst decontamination proceeds. 2.2. Results In vitro testing under dirty conditions (3.0g/l bo- vine albumin + 3.0ml/l sheep erythrocytes: Efficacy as a biocidal, virucidal, mycobatericidal and fungi- cidal device was demonstrated by testing, via an independent accredited microbiological laboratory (BluTest [3]), petri dishes containing Salmonella enteritidis NCTC 13346, Listeria monocytogenes NCTC 7973, Escherichia coli O157 NCTC 12900, Clostridium difficile NCTC 11209, Murine no- rovirus s99/RAW 264.7 cells, Mycobacterium terrae ATCC 15755, Aspergillus brasiliensis ATCC 16404. In each case, tests were done under dirty conditions and produced at least a 4 log 10
reduction in viable organisms. Treatment of inoculated surrogate lu- mens (2mm, 1.5m) showed > 6 log 10 reduction in P. aeruginosa, and aseptic storage exceeding 6 weeks. 3. References [1] Gerrity D, Snyder S: Ozone-Sci Eng 2011, 33(4):253-266. [2] Patent: Plasma generation and use of plasma generation apparatus WO 2011055113 A1 [3] BluTest, Glasgow UK (UKAS No. 4597)
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86 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Surface-wave-sustained plasma for model biological systems treatment
E. Benova 1 , Y. Topalova 2 , P. Marinova 3 , Y. Todorova 2 , M. Atanasova 4 , T. Bogdanov 5 ,
I. Yotinov 2
P
P
P
P
P
Faculty of Physics, Sofia University, Sofia, Bulgaria P
Faculty of Mathematics and Informatics, Sofia University, Sofia, Bulgaria P
P
Surface-wave-sustained Argon plasma torch operating at 2.45 GHz was used for treatment of Gram negative and Gram positive bacteria as model biological systems to study the plasma bactericide effect. In special discharge conditions we are able to produce microwave plasma torch with gas temperature close to the room temperature eliminating in this way the heating of the treated object by the plasma. Such plasma can be used for direct treatment of living tissues and thermo-sensitive materials. The obtained results show good deactivation effect at direct plasma treatment of bacteria in agar and in bacterial suspension. This means that at such discharge conditions the microwave plasma torch can be used for direct in vivo treatment and disinfection.
Argon plasma torch is sustained by travelling electromagnetic wave excited by surfatron type wave launcher at 2.45 GHz. A solid-state microwave generator is used at low wave power (from 12 to 40 W) with 0 W reflected power. Argon gas flow does not exceed 3.2 l/min. At appropriate discharge conditions a stable plasma torch with low gas temperature can be produced (Fig. 1).
Fig. 1. Microwave Argon plasma torch with low gas temperature The plasma torch is applied for direct treatment of microorganisms in agar and in bacterial suspension. Two model bacterial strains were used: Pseudomonas sp. AP-9 as a suitable model of pathogenic Gram negative bacteria and
Brevibacillus laterosporus BT-271 as a suitable model of pathogenic Gram positive, spore-forming bacteria. In all experiments the treatment time is very short – less than 1 min.
Thick layers of Pseudomonas with density from 2×10 7
9 cells/ml in agar plate were treated directly by the plasma torch at different wave power (14–22 W) and different treatment time (3–20 s). In Fig. 2 one can see well-presented completely sterilized zones with diameter depending on the wave power and treatment time. The later dependence is presented in Fig. 3.
Fig. 2. Control (left) and plasma treated agar plates (right) with Pseudomonas sp. AP-9 Fig. 3. Diameter of sterilization area at various wave power and treatment time at Pseudomonas concentration 6×10
9
cells/ml (left) and 2×10 7
cells/ml (right) The diameter of the plasma torch is about 2 mm and that of sterilized zones can be more than 1 cm with no movement in radial direction during the treatment. The sterilization was complete, without any survived colonies and stable (confirmed by more than 168 hours monitoring).
This work was supported by Bulgarian Science Fund under Grant DH08/8 of 2016. Topic number: 17 87
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Dariya D. Krivoruchko, Alexander V. Skrylev Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region, 141701, Russian Federation
At preset paper the excited state concentrations distribution of a Hall Thruster (HT) at 300 W operating conditions was investigated by Laser Induced Fluorescence (LIF) and compare with results of passive diagnostics. The main challenge is that researching object is non-equilibrium low-temperature xenon plasma: T e ≈2-100 eV, n i ≈ n
e ≈ 10
11 cm -3 ,n 0 ≈ 10 12 cm
-3 , r
D ≈ 10
-5...-6 cm, that can't be describe in the network of classical plasma models. The necessity of the multilevel kinetic model is shown. Excited state population density of neutral atoms is at good agreement with passive method, however for ions due to its space anisotropy can't be measurement near thruster face using integral method. Stepwise ionization and excitation is observed for one charged Xe ions but not significant for neutral atoms.
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