15th technological plasma workshop programme and book of … · 2018. 10. 25. · 15th...

15th Technological Plasma Workshop

Programme and Book of Abstracts

The Boardroom, Ricoh Arena, Coventry, UK

11th and 12th October 2017

15th Technological Plasma Workshop Ricoh Arena, Coventry

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Notes

There are more notes pages at the back of this booklet

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Contents

Conference Dinner Arrangements 5

Conference Schedule 6

Abstracts for Invited presentations 11

Abstracts for Contributed Presentations 14

Abstracts for Poster Presentations 32


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TPW Background

The Technological Plasma Workshop (TPW) is principally a UK-based international forum on the

science and technology of plasmas and gas discharges. Delegates from all countries are very

welcome to participate in this workshop.

Since the EPSRC Technological Plasma Initiative in 1997, technological plasmas have found

applications in diverse fields ranging from nano-science energy, through biomedicine and

environment, to space exploration. They offer major collaboration opportunities for academic

and industrial communities and exciting career prospects for younger scientists and engineers.

To support a full realisation of these opportunities, TPW aims to foster academic-industry

collaboration and to engage young plasma scientists with a scientific programme anchored by

leading plasma scientists. The workshop will comprise invited talks, contributed presentations

and a poster session.

In 2011, TPW became a conference of the Institute of Physics (IOP) Plasma Physics Group and

since 2014 TPW has been held in conjunction with the Vacuum Expo and the Vacuum

Symposium. The conference is currently co-sponsored by the IOP Plasma Physics Group and the

IOP Dielectrics & Electrostatics Group.

Scientific Committee

Professor Adrian Cross

University of Strathclyde

Chairman

Dr Felipe Iza

Loughborough University

Co-chair

Professor Timo Gans

University of York

Dr Mark Bowden

University of Liverpool

Mr John Simmons

RF Services, UK

Organising Committee

Dr Felipe Iza


Mr Alex Shaw


Professor Adrian Cross


Dr Nadarajah Manivannan

Brunel University


5

Conference Dinner Arrangements

The conference dinner will be held at Cosmo- world restaurant buffet. The all-you-can-eat

buffet and a refillable soft drink is included in your conference fee, any extra drinks must be

bought by you.

The table is booked for 19:00, so please meet in the foyer of the restaurant at 18:55.

Please make your own way from the conference venue to the restaurant, 36-42 Corporation

Street, Coventry, CV1 1GF.

If you have any problems getting to the restaurant then you can call the organising committee

on 07949 851738.

A number of transport options are available:

If you are driving then there are several car parks located close to the restaurant

o West Orchards Car Park, Smithford Way, Coventry, CV1 1GF

o Belgrade Plaza Car Park, Ringway Hill Cross, Coventry, CV1 4AJ

o Bishop Street Car Park, Tower Street, Coventry, CV1 1JN

Taxi- the address for the restaurant is 36-42 Corporation Street, Coventry, CV1 1GF

o www.allenstaxis.com or 02476 55 55 55

Bus- there is several buses that can get you to the restaurant. A google maps search is

the most efficient way of finding the next bus, however the 20 or 20A bus routes go

from near the arena to near the restaurant.

http://www.allenstaxis.com/


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Conference Schedule

Wednesday 11th October 2017

10:00 – 12:00 Vacuum Expo (Free entry for all delegates to visit the exhibitors)

12:00 – 12:45 Registration (Ricoh Arena foyer) and hang posters (Vacuum Expo exhibition hall)

Session 1 Chair: Dr Felipe Iza, Loughborough University, UK

12:45 – 12:50 Welcome, introduction and announcements

Adrian Cross, TPW chairman

12:50 – 13:30 Chemistry Induced by Atmospheric Plasma in Aqueous Liquids (invited)

Petr Lukes, Czech Academy of Sciences, Czech Republic

13:30 – 13:50 Charge Transfer Mechanisms Underlying Contact Glow Discharge Electrolysis

Aleksey Yerokhin, University of Manchester, UK

13:50 – 14:10 Chemical Probes for Plasma Diagnostics

Benjamin Buckley, Loughborough University, UK

14:10 – 14:30 Coffee break

Session 2 Chair: Professor Timo Gans, University of York, UK

14:30 – 15:10 Plasma medicine – beyond the long lived species (invited)

Kristian Wende, INP, Germany

15:10 – 15:30 The Potential of Gas Plasma Activated Water (PAW) Technology within the Agri-tech Industry

Giles Grainge, Royal Holloway University London, UK

15:30 – 15:50 Efficacy of plasma-generated ozone in bioburden decontamination

Declan Diver, University of Glasgow, UK

15:00 – 16:10 Combining simulations and experiments to investigate the plasma chemistry in atmospheric pressure plasmas

Sandra Schröter, University of York, UK


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Session 3: Poster session

16:10 – 17:00 Poster session (Vacuum Expo Exhibition Hall). The day one poster prize presentation will be at 16:30.

19:00 Conference dinner (Cosmo Restaurant, 36-42 Corporation St, Coventry, CV1 1GF)

Thursday 12th October 2017

Session 4 Chair: Professor Paul May, University of Bristol, UK

09:00 – 09:20 Low Temperature Plasma – Liquid Droplet Interactions

Paul Maguire, University of Ulster, Ireland

09:20 – 09:40 Dual frequency excitation for control of plasma chemistry and ion fluxes in radio-frequency atmospheric pressure plasmas

Andrew Gibson, University of York, UK

09:40 – 10:00 Manipulation of chemical species densities in an atmospheric pressure air plasma discharge using gas flow velocity

Mohammad Hasan, University of Liverpool, UK

10:00 – 10:20 Comparative Study of ‘COST Reference Microplasma Jets’

Frederik Riedel, University of York, UK

10:20 – 10:40 Coffee break

Session 5 Chair: Professor Adrian Cross, University of Strathclyde, UK

10:40 – 11:00 Non-Thermal Plasma for the Removal of Endocrine disrupting chemicals in Water

Chedly Tizaoui, Swansea University, UK

11:00 – 11:20 Modelling deposition removal from fusion optics

David Shaw, University of York, UK

11:20 – 11:40 Plasma-assisted degradation of dodecane as model organic extraction solvent from PUREX process

Yichen Ma, University of Liverpool, UK


8

11:40 – 12:00 Current-Controlled High Power Impulse Magnetron Sputtering of Titanium in Oxygen Atmosphere

Arutiun Ehiasarian, Sheffield Hallam University, UK

12:00 – 12:20 Technological Plasma Workshop AGM

12:20 – 13:45 Lunch and visit to the Vacuum Expo (Vacuum Expo Exhibition Hall). The day two poster prize presentation will be at 13:30.

Session 6 Chair: Dr Declan Diver, University of Glasgow, UK

13:45 – 14:05 Investigation of pseudospark-sourced electron beams in millimetre wave extended interaction oscillators

Adrian Cross, University of Strathclyde, UK

14:05 – 14:25 Laser Ablation of metal and metal-oxide targets, and applications towards Plasma Enhanced-Pulsed Laser Deposition

David Meehan, University of York, UK

14:25 – 14:45 Enhanced control of the ionisation rate in radio-frequency plasmas with structured electrodes via tailored voltage waveforms

Scott Doyle, University of York, UK

14:45 – 15:05 Low Temperature Plasmas for Wound Healing Applications

Helen Davies, University of York, UK

15:05 – 15:15 Closing remarks

Adrian Cross, TPW Chairman

15:15 Depart


9

List of poster contributions

6 Applying tailored voltage waveforms for control of the electron dynamics in atmospheric pressure plasmas

Layla Alelyani, A. Gibson, J.Bredin, S. Doyle, J. Dedrick, T. Gans, D. O’Connell

University of York

7 The detection of reactive oxygen and nitrogen species in plasma using luminescent europium complexes

Colum Breen, Ben Buckley and Stephen J. Butler


8 Magnetron injection gun design for Ka-band MW Gyroklystron

Kun Dong1, Li Wang1, Jianxun Wang1, Yong Luo1, Wenlong He2, Huabi Yin2, Dian Zhang2, Adrian W. Cross2, Kevin Ronald2, Alan D. R. Phelps2

1University of Electronic Science and Technology of China, 2University of Strathclyde

9 Using Fluorescent Probes for the Analysis of Reactive Oxygen Species in Plasma Systems

James Fuster, B. Buckley, F. Iza


10 Surveying plasma chemical kinetics with basic graph theory

Thomas D Holmes, William B Zimmerman

University of Sheffield

27 Analysis of HIPIMS of Molybdenum Plasma for the Development of Back Contacts for Solar Cell Applications

Daniel A. L. Loch, Arutiun P. Ehiasarian

Sheffield Hallam University, National HIPIMS Technology Centre, Howard Street, Sheffield UK

11 Atmospheric pressure plasma jet bonding of polydimethylsiloxane cell scaffolds

Matt Moles, Alex Shaw, Felipe Iza, Nick Medcalf


12 Space Averaged Mathematical Model of Pulse Powered Atmospheric Pressure Air Plasma

Faraz Montazersadgh, Alexander Wright, Alexander Shaw, Felipe Iza



10

13 Enhancement of mass transfer rate of plasma reactive species in gas-liquid phases with a Microfluidic plasma reactor

Oladayo Ogunyinka, A. Wright, A. Shaw, H. Bandulasena, F. Iza


14 Modelling the interaction of gas–plasma jets with liquids

Juliet Chinasa Ojiako


15 Atmospheric-Pressure Plasma Device for CO2 Conversion and Utilization

Adriano Randi, F. Iza, U. Wijayantha, A. Shaw, B.R. Buckley1


16 Plasma liquid interface for CO2 Conversion and Utilization

Muhammad Shaban, A. Randi, A. Shaw, B.R. Buckley,F. Iza


17 Removal of pharmaceuticals in waste water through Non-Thermal Plasma Treatment to impede Antimicrobial Resistance

Kay Tor, Chedly Tizaoui

Swansea University

18 Modeling of the particle fluxes of a helium plasma jet onto water surface

Sui Wang1,2, Dingxin Liu1, Xiaohua Wang1, Felipe Iza2

1Xi’anJiaotong University, P. R. China, 2Loughborough University, UK

19 Pre-treatment of a faecal simulant for bio-ethanol production with a novel microbubble enhanced DBD plasma reactor

A. Wright, A. Marsh, A. Shaw, G. Shama, F. Iza, H. Bandulasena


20 Performance Optimisation of Plasma Closing Switch Filled With Environmentally Friendly Gases

Yuan Yao, I. Timoshkin, M. P. Wilson, M. J. Given, T. Wang, S. J. MacGregor


21 QDB: a database of plasma process data

C. Hill1, S. Rahimi1, D. B. Brown1, A. Dzarasova1, J. R. Hamilton2, Saj Zand-Lashani1, S. Mohr1, J. Tennyson1,2

1Quantemol Ltd, 2University College London


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Technological Plasma Workshop 2017

Abstracts for Invited Presentations


12

Chemistry Induced by Atmospheric Plasma in Aqueous Liquids

Petr Lukes

Institute of Plasma Physics, Czech Academy of Sciences, Prague, Czech Republic

[email protected]

Plasma–liquid interactions are becoming an increasingly important topic in the field of plasma

science and technology. The interaction of non-equilibrium plasmas with a liquid state is

important in many applications ranging from environmental remediation to material science and

health care. Depending on the type of discharge, its energy, and the chemical composition of the

surrounding environment various types of physical processes and plasma-chemical reactions can

be initiated and a number of primary and secondary species can be formed by plasma in the

liquid either directly, or transferred from the gas phase discharge plasma being in contact with

the liquid [1, 2]. Among these processes, the oxidative properties of reactive oxygen species (OH

radical, atomic oxygen, ozone, hydrogen peroxide) and nitrogen species (nitric oxide, nitrogen

dioxide radical) are generally accepted to play central role in the chemical and biological effects

of plasma produced in gas-liquid environments. In addition, secondary chemical and biological

effects can be induced in the plasma-treated liquid through the post-discharge reactions of

chemical species produced by plasma in the liquid either directly, or transferred from the gas

phase discharge plasma via gas-liquid interface (e.g., H2O2, ozone, nitrite, peroxynitrite). Many

of these chemical species are not stable in the liquid and subsequent reactions can take place

giving rise to new transient species as OH•, O2•-, NO• and NO2• radicals, which have highly

cytotoxic properties and cause prolonged activity of plasma-treated solutions after the exposure

to the discharge. This extended chemical and biological effect phenomenon was called by

different names (e.g., plasma activated water) and is subject of study in different plasma

medicine and agriculture motivated applications.

Nevertheless, the properties of plasma activated liquids and duration of their activity are affected

by many factors which determine a type, quantity and also lifetime of the reactive species being

formed in plasma treated liquid. For aqueous solutions that were treated by air-liquid-phase

plasmas, great attention is paid especially to the chemistry and biocidal effects of peroxynitrite

and acidified nitrites [3, 4]. Hypochlorite ions are assumed to play important role in saline

solutions treated by plasma. Chemical composition of cell culture media gives additional

complexity to the aqueous chemistry in plasma activated liquids because presence of organic

compounds. Therefore, chemical and biological effects in plasma activated liquids are result of

complex interactions of plasma at gas-liquid interface and chemical reactions of its products in

the liquid. In this talk the main chemical processes initiated in plasma-treated liquids will be

discussed. Special attention will paid to the peroxynitrite chemistry in air plasma treated liquids.

References:

1. P. J. Bruggeman, M. J. Kushner, B. R. Locke, et al., Plasma Sources Sci. Technol. 25,

053002 (2016)

2. V. I. Parvulescu, M. Magureanu, P. Lukes (eds.), Plasma Chemistry and Catalysis in Gases

and Liquids, Wiley-VCH Verlag, Weinheim, 2012

3. D.B. Graves, J. Phys. D: Appl. Phys. 45, 263001 (2012)

4. P. Lukes, E. Dolezalova, I. Sisrova, M. Clupek, Plasma Sources Sci. Technol. 23, 015019

(2014)


13

Plasma medicine – beyond the long lived species

K. Wende1, H. Jablonowski

1, G, Bruno

1, J. Lackmann

1,3, Th. v. Woedtke

1, M. Lalk

2, K.-D.

Weltmann1

1Leibniz Institute for Plasma Science and Technology e.V., Felix-Hausdorff-Str. 2,17489,

Greifswald, Germany 2University of Greifswald, Institute for Biochemistry, Felix-Hausdorff-Str. 3,17489,

Greifswald, Germany 3Ruhr-University Bochum, Biomedical Applications of Plasma Technology, Universitaetsstr.

150, 44780 Bochum

Today, plasma medicine has reached recognition from clinicians and practical physicians,

especially from the field of surgery. Initially, attention based on the ability of non-thermal

atmospheric pressure plasmas to kill even multi-resistant bacteria while leaving mammalian

cells apparently unaffected. As will be briefly introduced, the field has profoundly developed,

with sophisticated applications in dentistry, wound care, and cancer treatment. As safety

seem to be of no concern for some plasma sources, the clinical proof of their effectiveness is

being “in production”. Although much effort has already been put forward, the underlying

chemical mechanisms remain scarcely understood. Clearly, he concept of (mammalian) redox

signalling must be observed for the presence of dominant, cell physiologically relevant

reactive oxygen or nitrogen species. Two different avenues are currently used to gain

understanding and will be discussed: a) using the medical (or biological) outcome of a plasma

treatment as a key towards understanding or b) using the (bio-) chemical traces and footprints

left by the reactive entities created by the plasma. Using a suitable environment, impact of

plasma generated ROS on defined small organic molecules can be successfully applied as an

avenue to circumscribe the potential of plasmas [1],[2], and especially the deposited short

lived species [3]. As an example, the use of cysteine and cystine will be highlighted. Further,

dedicated radical scavenger known in EPR spectroscopy can be used. The data presented will

highlight the role of short lived species, leaving the hydrogen peroxide behind. From

evidence, implications for clinics, further research, and general application are discussed.

1. J. Winter, K. Wende, K. Masur, S. Iseni, M. Dunnbier, M. U. Hammer, H. Tresp, K. D.

Weltmann, and S. Reuter, J Phys D Appl Phys 46 (29) (2013).

2. P.-M. Girard, A. Arbabian, M. Fleury, G. Bauville, V. Puech, M. Dutreix, and J. S. Sousa,

Scientific reports 6 (2016).

3. H. Tresp, M. U. Hammer, J. Winter, K. Weltmann, and S. Reuter, Journal of Physics D:

Applied Physics 46 (43) (2013) 435401.


14


Abstracts for Contributed Presentations


15

Charge Transfer Mechanisms Underlying Contact Glow Discharge

Electrolysis

A. Yerokhin1, V.R. Mukaeva

2, E.V. Parfenov

2, A. Matthews

1

1University of Manchester, Oxford Road, Manchester, M13 9PL, UK

2Ufa State Aviation Technical University,12 Karl Marx Street, Ufa, 450008, Russia

[email protected]

Plasma-assisted electrochemical processes underpin a range of ground-breaking

developments in chemistry, biology, medicine, materials science and engineering. Despite

high practical significance, the mechanisms underlying these processes are relatively poorly

understood. In particular, for the systems where gaseous products of electrolysis prevail,

transition from normal electrolysis to the plasma-assisted regime known as Contact Glow

Discharge Electrolysis (CGDE) is often treated in terms of bubble to film boiling transition

within the framework of Helmholtz-Taylor theory of hydrodynamic heat transfer1. However,

this does not explain what governs the charge transfer through the electrode-electrolyte

interface in the film-boiling mode.

We investigated anodic processes that occur during CGDE of stainless steels in aqueous

solutions of (NH4)2SO4 in the voltage range of 250 to 350 V at electrolyte temperatures of 70

to 90 oC, using voltammetry, OES and impedance spectroscopy techniques. The latter was

adopted to the high-voltage electrolysis, with data validated in time domain using originally

developed approach2. Faradaic yields of the main anodic reactions of metal dissolution and

water splitting were studied using gravimetric methods.

The optical emission from the anode was found to commence in the falling part of the

current–voltage diagram prior to the median region of minimum current density. The optical

spectra of discharge born clear evidence of intermediates and final products of the main

anodic reactions, including Fe, H, OH and O species. The impedance spectra revealed

presence of three kinetic processes with different time constants which we associate with the

interfacial charge transfer and two characteristic responses from different reaction

intermediates – one species providing blocking effect by covering about 95% of active sites

on the surface and the other unblocking it. The equivalent thickness of the blocking layer was

estimated to be in the region of 0.5 to 1 nm, indicating that the current transfer in the system

was limited by the adsorbed layer of reaction intermediates rather than by a whole film of

gaseous reaction products. The inductive unblocking response coincided with the onset of

plasma discharge and a noticeable decrease in the current yield of anodic metal dissolution

reaction. This was therefore attributed to the changes in the pathways of the water splitting

reaction, which could be catalysed on oxy-hydrated metal surfaces. In particular, it was

proposed that this four-electron transfer process has been facilitated by deviation from a two-

site terminal oxo-twin route to the single-site early peroxo formation route3. Possible reasons

and pre-requisites for such diversion are discussed.

References:

1. S.K. Sen Gupta, Plasma Sources Science and Technology, 24 (2015) 063001.

2. A Yerokhin, et al, Electrochemistry Communications, 27 (2013) 137-140.

3. H. Dau, et al, ChemCatChem, 2 (2010) 724-761.


16

Chemical Probes for Plasma Diagnostics

C. Castelló-Beltrana,b

, Alexander Wrightb, James Fuster

a, Felipe Iza

b, and Benjamin Buckley

a

aDepartment of Chemistry, Loughborough University

bSchool of Mechanical, Electrical & Manufacturing Engineering, Loughborough University

[email protected]

Characterization of the chemical composition of plasmas is of primary importance to optimize

their performance. Plasma composition is typically studied by absorption and emission

spectroscopy and mass spectrometry[1]. These experimental techniques are also often

complemented with computational studies[2]. These traditional plasma diagnostics characterize

the plasma gas phase. But, for atmospheric pressure discharges it is difficult to link experimental

information on the gas phase to the actual flux of species experienced by a target exposed to

plasma. This is due to the non-homogeneity of atmospheric pressure discharges.

The detection and quantification of reactive oxygen species (ROS) has been an area of intense

interest due in part to ROS ubiquitous involvement in a range of biological processes.[1,2] The

development of sensitive mechanisms by which to monitor and detect ROS has found wide

interest across a range of scientific disciplines. From the range of possible methods of detection,

small molecule fluorescent probes have become increasingly applied in the determination and

quantification of ROS. This is due to their high levels of sensitivity, simplicity in terms of data

collection, and high spatial resolution.[3]

Due to the importance of oxygen containing plasmas in emerging biomedical and environmental

applications, we have focused our initial efforts on studying oxygen containing plasmas. Some of

the main reactive oxygen species (ROS) generated in these plasmas are singlet oxygen, ozone,

superoxide radical, hydroxyl radical and hydrogen peroxide. Our efforts have been focused on

the development of novel ozone detection probes[1]. Unlike their application in biological

systems the application of these probes to nonthermal plasma characterisation has been

challenging vida infra and has highlighted the need for in depth analysis of the probes in

question. Selectivity of the chemical probe is paramount and the severe oxidising environments

experienced by the probes under nonthermal plasma conditions can limit their usefulness and

ability to enable quantification of the ROS in question.

We will report here that small molecule fluorescent probes present a viable tool to be applied in

the detection/quantification of nonthermal plasmas, but caution is required when using them in

such highly oxidising environments.

References:

1. S. Reuter, J. Winter, S. Iseni, et al., Plasma Sources Sci. Technol., 2012, 21, 034015.

2. D. X. Liu, M. Z. Rong, X. H. Wang, F. Iza, M. G. Kong and P. Bruggeman, Plasma Process and

Polym, 2010, 7, 846.

3. Carlos Castelló Beltrán, Elliott A. Palmer, Benjamin R. Buckley* and Felipe Iza* Chem.

Commun. 2015, 51, 1579.


17

The Potential of Gas Plasma Activated Water (PAW) Technology within

the Agri-tech Industry

Grainge G.1, Steinbrecher T.

1, Nakabayashi K.

1, Iza F.

2, Sharma G.

2, Leubner-Metzger G.

1

1School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, UK;

2Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough

University, Loughborough, LE11 3TU, UK

www.seedbiology.eu, [email protected]

It is a priority for farmers to establish uniform and rapid seed germination within a broad

range of abiotic conditions. The industry actively pursues the development of innovative seed

treatments to achieve this goal, and the emergence of utilizing gas plasma is drawing

attention. The formation of non-thermal atmospheric gas plasma at a gas-aqueous interface

results in the production of many transient species (OH·,NO2·, NO radicals) and more stable

compounds (H2O2, NO3-, NO2

-). Several of these chemicals synthesised in plasma activated

water have known positive physiological effects on the regulation of seed germination, and

therefore opens an intriguing area of study. Seed germination is the most vital stage in a

plants life cycle and determines its fitness and crop yield. Previous reports have shown

significant improvement in germination speed of mung bean and increased tolerance to both

salt and osmotic stress, however, no underlying mode of action has been ascertained. This

work looks at deciphering which constituent chemicals of the plasma activated water

influence the speed and uniformity of seed germination. The stable nitrogen anions, NO3- and

NO2-, have well described signalling mechanisms which act through modulating the

phytohormones, Abscisic acid (ABA) and Gibberellins (GA) ratio, in the favour of GA. Nitric

oxide is a known to influence the timing of germination which in part functions as part of the

N-end rule pathway regulating ethylene response factors. Hydrogen peroxide is an established

intercellular signalling molecule which regulates the timing of germination, and the more

reactive oxygen species O2- and OH. are critical for endosperm weakening, a pre-requisite for

the onset of germination. If the improvements to seed germination performance are optimized

and shown to be conserved amongst crops seeds, the environmentally friendly aspect and

practically of plasma activated water technology would be an enticing prospect for the seed

industry, agriculture and food security.


18

DBD plasma source

Target chamber

Efficacy of plasma-generated ozone in bioburden decontamination

M. Pajak1, R. Barton

2, D. A. Diver

1, H. E. Potts

1,2, A. Smith

3

1School of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK

2Anacail Ltd, Thomson Building, University of Glagsow, Glasgow G12 8QQ, UK

3Institute of Infection, Immunity and Inflammation, University of Glasgow, 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 configuration, the system can generate significant ozone concentrations in sealed packages

from the outside, 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 possible 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, mycobactericidal and fungicidal treatments are possible, both in

vitro and in realistic conditions.


19

Combining simulations and experiments to investigate the plasma chemistry

in atmospheric pressure plasmas

S. Schröter1, J. Bredin

1, A. R. Gibson

1,2, A. Wijaikhum

1, A. West

1, H. Davies

1, Y. Gorbanev

3,

K. Niemi1, J. Dedrick

1, M. Foucher

2, N. de Oliveira

4, L. Nahon

4, J.-P. Booth

2, V. Chechik

3,

E. Wagenaars1, T. Gans

1, D. O’Connell

1

1York Plasma Institute, Department of Physics, University of York, York YO10 5DQ, UK

2Laboratoire de Physique des Plasmas-CNRS, Ecole Polytechnique, 91128 Palaiseau, FR

3Department of Chemistry, University of York, Heslington, York YO10 5DD, UK

4Synchrotron Soleil, l’Orme des Merisiers, St Aubin BP 48, 91192 Gif sur Yvette Cedex, FR

[email protected]

The quantification of reactive species (RS) in atmospheric pressure plasmas (APPs) is of great

interest for various applications, such as in biomedicine, where they are believed to play an

important role. A variety of experimental and numerical techniques have been used to quantify

RS and investigate the complex plasma chemistry in APPs. Experimentally, diagnostic

techniques for the detection of RS in APPs have to tackle challenges associated with these

systems, such as small physical dimensions and fast decay times of excited states due to

collisions with the background gas, as well as gas mixing with ambient air. Computationally,

large chemical reaction sets are typically required to describe the complex plasma-chemical

kinetics accurately. The accuracy of plasma-chemical models is strongly limited by the

uncertainties associated with reaction rate coefficients, making benchmarking of these models

against experimental results essential.

In this work, experimental and numerical approaches are combined to investigate the generation

of reactive species in a radio-frequency APP in He, with small admixtures of molecular gases

such as H2O and O2. Experimentally, we use absorption spectroscopy in the VUV and UV

spectral range (gas phase) and in the UV-visible range (liquid phase), as well as two-photon

absorption laser induced fluorescence with picosecond temporal resolution (gas phase) to detect

O, H, OH, and H2O2. Absolute quantities of these species are compared to those obtained using a

0D plasma-chemical kinetics model. This combined approach allows for a benchmark of the

simulation results against an array of experimentally measured species densities, and for

subsequent investigation of the most important formation pathways for different plasma

produced species. Following this benchmark, the simulated species densities are generally found

to be in good agreement with those obtained from numerical simulations. The complex formation

pathways of these and other plasma produced species, along with potential tailoring strategies

will be discussed.

Acknowledgements:

This work was financially supported by the UK EPSRC (EP/K018388/1 \& EP/H003797/1), the

Leverhulme Trust (grant no. RPG-2013-079), the York-Paris Low Temperature Plasma Collaborative

Research Centre, and the Australian Government Endeavour Research Fellowship. Additionally, this

work was performed within the LABEX Plas@par project and received financial state aid, managed by

the Agence National de la Recherche as part of the programme ``Investissements d'avenir" (ANR-11-

IDEX-0004-02). A. Wijaikhum acknowledges financial support from the Development and Promotion of

Science and Technology Talents Project (DPST), Royal Government of Thailand scholarship.


20

Low Temperature Plasma – Liquid Droplet Interactions

Paul Maguire, H McQuaid, D Rutherford, D Mariotti

NIBEC, University of Ulster, Newtownabbey, Ireland

[email protected]

Transport of micron-sized liquid droplets through a low temperature RF plasma [1] at

atmospheric pressure has demonstrated a number of remarkable and unexpected effects. After

a short flight time, ~120

and gas flux proceed at a rate that is significantly faster that observed in plasma – bulk liquid

studies and many orders of magnitude faster than in standard bulk chemistry [2]. The

microdroplet system allows for a controlled ambient environment, a large surface area to

volume ratio, very small reaction volume, low droplet temperature, in-flight chemical

synthesis of nanoparticles and encapsulation, and remote delivery of the nanoparticles.

The droplet chemistry leading to nanoparticle formation is complex. The plasma feed gas

contains only noble gases along with H2O from the evaporating droplet. Other observed

chemical species in the liquid are H2O2 and OH, most likely due to generation of these

species in the plasma phase. The H2O2 generation rate was measured and found to be much

higher than reported for other plasma – liquid configuration. The degradation rate of

Methylene Blue dye due to OH radical bombardment was observed with varying distance up

to 150 mm from the plasma source.

Plasmas-liquid interactions are a valuable source of radical species for plasma medicine

including antimicrobial applications. However untangling the complex interplay between

species and biology over very short timescales and distances is proving extremely

challenging. The plasma-droplet system offers opportunities to study these interactions in a

controlled manner. We have used droplets as carriers for single bacteria cells, which are then

exposed to plasma species (electrons, OH and H2O2) for a very short time (~0.1 ms) and the

effects on cell viability and properties determined.

It is clear that this system is complex but yet may offer unique access for plasma – liquid

chemistry and biology studies.

References:

1. PD Maguire et al., Appl. Phys. Lett. 106, 224101 (2015); http://dx.doi.org/10.1063/1.4922034

2. PD Maguire et al., Nano Lett., 17, 1336–1343 (2017)

http://dx.doi.org/10.1021/acs.nanolett.6b03440

http://dx.doi.org/10.1063/1.4922034

http://dx.doi.org/10.1021/acs.nanolett.6b03440


21

Dual frequency excitation for control of plasma chemistry and ion fluxes in

radio-frequency atmospheric pressure plasmas

A. R. Gibson1,

C. O’Neill2, T. Gans

1

1York Plasma Institute, Department of Physics, University of York, York YO10 5DQ, UK

2Centre for Plasma Physics, Queen’s University Belfast, University Road, Belfast, BT7 1NN,

UK

[email protected]

Plasmas driven by two or more frequencies in the radio-frequency range are extensively used

in low-pressure plasma processing applications. In these cases, dual frequency operation

offers favourable control of the plasma density, which defines the ion and neutral flux to the

substrate, and the sheath potential, which defines the ion energy distribution (IEDF) at the

substrate. Despite the widespread use of such waveforms at low pressure, excitation of

atmospheric pressure plasmas by multiple frequency waveforms has received comparatively

little attention.

In this work, dual frequency waveforms (13.56 + 40.68 MHz) are investigated for control of

charged and neutral species properties in atmospheric pressure He/O2 plasmas using 1D semi-

kinetic fluid simulations. It is demonstrated that variation of the contribution of each

frequency to the driving voltage waveform, and the phase shift between the frequencies,

allows for a high degree of independent control of the density of high- (He metastables) and

lower-energy (O and O3) threshold species. Furthermore, independent control of the ion and

neutral flux to surfaces can also be achieved. The mechanism behind this control is shown to

be the motion of the plasma sheath, which, under certain combinations of frequencies and

phase shift, leads to strong temporal confinement of electron heating within the radio-

frequency cycle and subsequently to control of the electron energy distribution function

(EEDF). Potential uses for such control strategies in applications of these plasmas will be

discussed.

Acknowledgements:

The authors would like to thank the U.K. Engineering and Physical Sciences Research Council

(EPSRC) for supporting this research through EPSRC Manufacturing Grant (No.EP/K018388/1). C.

O’Neill acknowledges funding through a Northern Ireland Department of Employment and Learning

(NI DEL) studentship.


22

Manipulation of chemical species densities in an atmospheric pressure air

plasma discharge using gas flow velocity

M I Hasan and J L Walsh

Centre for Plasma Microbiology, Department of Electrical Engineering and Electronics, the

University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, U.K. [email protected]

In recent years, interest in atmospheric-pressure air plasma discharges (AAPD) has grown

significantly. Due to their ability to deliver a wide range of species in ambient conditions (humid

air at room temperature), they have been developed for wide range of applications extending

from materials modification to wound healing [1,2].

The lifetimes of chemical species generated in an AAPD vary significantly, ranging from

nanoseconds to minutes. For several applications, such as microbial decontamination, it is highly

desirable to deliver species with relatively short lifetimes, e.g. OH, to a downstream sample [3].

Unfortunately, perhaps one of the most common AAPD systems employs a Surface Barrier

configuration, where plasma is generated remotely from the sample and thus the downstream

transport of highly reactive species is minimal. This situation can be improved by introducing

gas convection, this enhances transport of OH and other relatively short-lived species to a treated

sample within the species lifetimes.

Using a numerical model, it is shown in this work that the influence of a convective flow goes

beyond merely transporting the species downstream. Results show that increasing the gas flow

velocity causes an increase in the densities of short lived species such as OH, N, and O2(a1

and causes a decrease in the densities of long lived species, including O3, NO2, H2O2 and HNO3

[4]. This behaviour is attributed to a quadric loss reaction of OH that is strongly influenced by

the convection velocity. Due to the high reactivity of OH, this change in its density alters the

chemistry of the other species, leading to the reported behaviour.

References: 1. Applied Surface Science 388, 539 (2016).

2. Appl. Phys. Lett 109, 233701 (2016).

3. New J. Phys. 11, 115012 (2009).

4. Appl. Phys. Lett. 110, 134102 (2017).

Figure 1. The OH density as function of space for different flow velocities


23

Comparative Study of ‘COST Reference Microplasma Jets’

Frederik Riedel1, J Golda

2, J Held

2, J Bredin

1, T Gans

1, V Schulz-von der Gathen

2, D O’Connell

1

1York Plasma Institute, Department of Physics, University of York, York YO10 5DD, UK

2Experimental Physics II: Application Oriented Plasma Physics, Ruhr-Universität Bochum,

44801 Bochum, Germany

[email protected]

Atmospheric microplasmas have gained interest in the past decades in many fields [1] including

biomedical applications, due to their efficient production of chemical reactive species e.g.

reactive oxygen nitrogen species. A source that is easy to use, build and simulate was proposed

by the COST Action MP1101 ‘Biomedical Applications of Atmospheric Pressure Plasmas’ and

presented in [2].

The motivation for the COST Reference Microplasma Jet is to have a reference source for

atmospheric pressure plasmas. Such a reference source could boost the understanding of

atmospheric microplasmas by making results from different labs more comparable. For this every

plasma jet should be reproducible with little variability and have the same characteristics with

regards to plasma power, gas temperature and reactive species.

For the purpose of characterisation and examining variability four COST Reference Jets have

been characterised. This includes electrical power measurements, gas temperature measurements

of the effluent, optical emission spectroscopy of the core plasma and atomic oxygen densities by

means of two photon absorption laser induced fluorescence. The results show that the four tested

jets are in good agreement with each other.

References:

1. Foest et al. “Microplasmas, an emerging field of low-temperature plasma science and technology”

https://doi.org/10.1016/j.ijms.2005.11.010

2. Golda et al. “Concepts and characteristics of the COST Reference Microplasma Jet”

http://dx.doi.org/10.1088/0022-3727/49/8/084003

Figure 1. Atomic oxygen densities vs. plasma power and voltage vs. plasma power. Gas: 1 slm helium and 5 sccm oxygen.

The densities are averaged from four COST reference jets and the error bars represent the standard deviation from all

jets. The atomic oxygen density increases not linearly with power but with voltage (shown in red). The standard deviation

between the jets varies between 8 – 13 %.

mailto:[email protected]

https://doi.org/10.1016/j.ijms.2005.11.010

http://dx.doi.org/10.1088/0022-3727/49/8/084003


24

Non-Thermal Plasma for the Removal of Endocrine disrupting chemicals in

Water

Tizaoui, C. and Ni Y.

College of Engineering, Bay Campus, Swansea University, Swansea SA1 8EN, UK

[email protected]

Endocrine Disrupting Chemicals (EDC) can affect the endocrine system and interfere with

important development in humans and wildlife. EDCs have been found in almost all water

matrices including surface water, ground waters, drinking waters, and conventional wastewater

treatment plants were not designed to remove EDCs.

Non-thermal plasma (NTP) ignited in ambient air is able to generate a rich amount of reactive

species, which attracts an extensive attention in the applications of wastewater treatment and

organic contaminants removal. This study investigated the removal of 17α-ethinylestradiol

(EE2) in water using a pulsed NTP system under a variety of operation conditions such as pulse

frequency, output voltage and feed gas flow rate.

Results showed that the higher removal rate of EE2 in water after NTP treatment was achieved

with the combination of higher frequency, higher voltage and lower gas flow rate. Figure 1

shows the effect of pulse frequency on the degradation of EE2 as a function of time. The half-life

times (i.e. 50% removal) were approximately 38, 21 and 12 min for the frequencies 100, 300, and

500 Hz respectively. The increased rates of degradation as function of the pulse frequency is the

result of increased energy deposited in the system. This has also been confirmed by increased

rates when the voltage was increased.

Figure 1. Degradation of EE2 by NTP treatments at different pulse frequencies.

0%

20%

40%

60%

80%

100%

0 5 10 15 20 25 30

Rem

oval (%

)

time (min)

100 Hz 300 Hz 500 Hz


25

Modelling deposition removal from fusion optics

David Shaw1, Mark Kushner

2, and Erik Wagenaars

1

1York Plasma Institute, Department of Physics, University of York, York, YO10 5DQ, UK

2University of Michigan, Electrical Engineering and Computer Science Dept., 1301 Beal Ave,

Ann Arbor, MI 48109-2122, USA

Within a fusion reactor the optical component of any diagnostic closest to the plasma is called

the first mirror. The energetic atoms formed by charge exchange within the plasma can bombard

the mirrors and erode the surface. This same erosion process occurs on the nearby first wall and

causes the deposition of this material on the mirrors. These processes cause degradation of the

reflectance of the mirror surface and therefore degradation in the quality of the signal reaching

the diagnostic. Erosion is easily overcome using either single crystal or small scale crystal

structures, however degradation caused by deposition is substantial and still requires a sufficient

solution.

Low-temperature plasma removal of these fusion depositions is a potential way of maintaining

the reflectivity of the mirrors in-situ. This involves creating a capacitively coupled plasma using

the mirror as the electrode. Experimentally this has been tested and provides good results [1,2],

however these have used aluminium oxide as a proxy for the beryllium set for use in future

fusion devices. It is also not possible to test all individual mirror placements or magnetic field

geometries. Using the Hybrid Plasma Equipment Model (HPEM) it is possible to simulate the

conditions and chemistry as close to the working environments as possible. This allows us to

understand the plasma and work towards optimisation of the removal process by varying

operating parameters, such as frequency, voltage, pressure, and power. By also investigating gas

mixtures we can combine the ion bombardment with chemical etching.

References: 1. Moser, L., et al. Nucl. Fusion, 55(6):063,020 (2015).

2. Moser, L., et al. J. Nucl. Mater., 463:940{943 (2015).


26

Plasma-assisted degradation of dodecane as model organic extraction

solvent from PUREX process

Yichen Ma, Shiyun Liu and Xin Tu*

Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool L69

3GJ, UK

*[email protected]

In nuclear industry, one of the radioactive liquid organic wastes, contaminated dodecane (C12H26)

from spent fuel reprocessing, is classified as problematic wastes. Effective method of complete

degradation of dodecane is in urgent need. Non-thermal plasma catalysis has been regarded as a

promising alternative with advantages over conventional methods to tackle this challenge facing

nuclear industry. It can achieve significant reduction of waste volume at low temperature and

provide a solution to convert waste to valuable products.

In this study, plasma degradation of dodecane was carried out using a gliding arc plasma reactor

by changing dodecane concentration, total flow rate, and applied voltage. The performance of the

plasma process has been investigated in terms of the conversion of dodecane, yield and

selectivity of products, and energy efficiency. A large amount of valuable gaseous products, such

as light alkynes and olefins, were produced in this process. The selectivity of H2, C2H2, and

C2H4, reached 83.4%, 47.1%, and 13.6%, respectively. In addition, the total selectivity of

hydrocarbons peaked (67.5%) at the maximum total flow rate of 3.75 L/min. Future work will

focus on the combination of plasma with a range of catalysts to further enhance the selectivity

and energy efficiency of the process.

References: 1. J.C. Whitehead, M. Prantsidou, Investigation of hydrocarbon oil transformation by gliding arc

discharge: comparison of batch and recirculated configurations, Journal of Physics D: Applied

Physics, 49 (2016) 154001.

2. D. Moussa, J.-L. Brisset, Disposal of spent tributylphosphate by gliding arc plasma, Journal of

Hazardous Materials, 102 (2003) 189-200.


27

Current-Controlled High Power Impulse Magnetron Sputtering of

Titanium in Oxygen Atmosphere

A.P. Ehiasarian1, P.Eh. Hovsepian

1, D.A. Loch

1, J. Neidhard

2, A. Heisig

2

1National HIPIMS Technology Centre, Sheffield Hallam University, Howard St., Sheffield,

UK 2Von Ardenne GmbH, Plattleite 19/29, 01324 Dresden, Germany

[email protected]

High density transparent oxide layers on glass can improve the environmental protection

ability of low emissivity layers in glazing and the photocatalytic deactivation of organic

contaminants. High Power Impulse Magnetron Sputtering (HIPIMS) produces high

toughness films with a high density microstructures due to the delivery of a highly ionised

deposition flux to the substrates.

Reactive HIPIMS of Ti in Argon-Oxygen atmosphere was carried out by regulating the

current within each pulse. This allowed seamless operation for oxygen flows ranging from 10

to 50% of the total gas flow and resulted in the elimination of stability issues arising from

runaway currents associated with target poisoning. The plasma ignition proceeded through a

Argon gas phase. The excitation of Argon was dampened due the development of metal

sputtering and an associated cooling of the electron temperature. At later stages of the pulse,

gas rarefaction leads to further reduction in Ar excitation. Atomic oxygen is produced both

by sputtering from the target and gas dissociation with the former processes dominating at

lower pressures. TiOx films were produced in a cluster tool by reactive HIPIMS of a pair of

metallic targets in an Ar-Oxygen atmosphere in an asymmetric bipolar discharge. The films

were deposited without additional heating or substrate biasing and had good transparency.

The thickness uniformity was < 2% across a 100x100 mm area. The refractive index of

HIPIMS-deposited films reached value of 2.55 at a wavelength of 550 nm compared to 2.47

for bipolar pulsed DC. The films comprised a mixture of rutile and anatase phase with

HIPIMS deposition producing higher fractions of rutile compared to bipolar pulsed DC

operation. The hardness of the films and its relation to process conditions are discussed.


28

Investigation of pseudospark-sourced electron beams in millimetre wave

extended interaction oscillators

A.W. Cross1, H. Yin

1, L. Zhang

1, W. He

1, G. Shu

1, J. Zhao

2, Y. Yin

3, K. Ronald

1 and A.D.R.

Phelps1

1Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, Scotland, UK

2High Voltage Division, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an,

710049, China 3School of Physical Electronics, University of Electronic Science & Technology of China,

Chengdu, China

[email protected]

High frequency sources above 100 GHz are in great demand for a wide range of research and

technical applications, including molecular spectroscopy, bio-imaging and security screening. Up

to date, vacuum electronic technolody still remains as the main method to achieve millimetre

wave radiation of high power of up to the kilowatt level. As the frequencies move into the sub-

terahertz and terahertz region, the size of device reduces greatly. This brings a challenge with

regard to device fabrication. Therefore a compact and simplified structure is desirable with the

pseudospark-sourced electron beam an ideal choice for high power, high frequency sources. This

is because of the formation of an ion channel following the pseudospark anode, which enables

the beam to propagate with no need of a guiding magnetic field.

Thus the pseudospark discharge has attracted a lot of interest in recent years and have been

explored for high quality electron beam generation for various microwave and millimetre-wave

sources and potential terahertz devices [1,2]. Among various vacuum electronic devices, the

extended interaction oscillation (EIO) has gained considerable attention as a promising

millimetre wave oscillation source due to its high gain per unit length and compact configuration.

This paper presents some recent investigation results of using pseudospark-sourced electron

beam instead of the conventional electron beam produced by a thermionic cathode to drive the

EIO to achieve a more compact structure. Electron beams from both a 4-gap pseudospark

discharge chamber and a one-gap pseudosaprk discharge chamber combined with a post-

acceleration unit were used to drive a W-band EIO structure. It was found that the post-

accelerated beam driven EIO has much higher output power because the electron beam quality

was greatly improved with much smaller beam energy spread [2,3].

To further increase the output power, future studies of a pseudospark-sourced beam for the

generation of a sheet-beam to drive the EIO interaction will be presented.

References:

1. W. He.,L. Zhang, et al, “Generation of broadband terahertz radiation using a backward wave

oscillator and pseudospark-sourced electron beam”, Appl. Phys. Lett. 107, 133501(2015).

2. J. Zhao, H. Yin, L. Zhang, G. Shu, W. He, et al, “Influence of the electrode gap separation on

the pseudospark-sourced electron beam generation”, Phys. Plasmas 23(7)， 073116 (2016)

3. J. Zhao, H. Yin, L. Zhang, G. Shu, W. He, Q. Zhang, A. D. R. Phelps, and A. W. Cross,

"Advanced post-acceleration methodology for pseudospark-sourced electron beam", Phys.

Plasmas 24 (2), 023105 (2017).


29

Laser Ablation of metal and metal-oxide targets, and applications towards

Plasma Enhanced-Pulsed Laser Deposition.

David Meehan, Sudha Rajendiran, Erik Wagenaars

York Plasma Institute, Department of Physics, University of York, York, UK, YO10 5DQ

Metal oxide thin films, such as Zinc Oxide and Copper Oxide, find uses in many modern

technologies including photovoltaics, batteries, and displays. An established method of making

such films is Pulsed Laser Deposition (PLD), where a laser is used to ablate a target of the

desired material, which is then deposited onto a substrate; Although PLD is easy and readily used

for metal targets, oxide targets have been shown to be more challenging, requiring carefully

tuned oxygen background atmospheres to ensure the desired stoichiometry is achieved. We have

investigated this computationally using of the 2-dimensional hydrodynamic code POLLUX; The

ablation of Zinc, Copper and their corresponding oxides was simulated under a range of possible

laser ablation conditions; From this we can shown that metal-oxides ablate ~60% less mass than

their metal counterparts, with comparable yet slightly cooler temperatures.

Alongside this a novel deposition technique has been developed, Plasma Enhanced-Pulsed Laser

Deposition (PE-PLD), where a metal target is ablated in the presence of oxygen reactive species

produced by an Inductively Coupled Plasma (ICP); Allowing for use of the easier ablated metal

targets, whilst also providing additional benefits such as no need for substrate heating, and

stoichiometry control of the deposited film via different operating conditions of the ICP. Initial

Copper Oxide films have been deposited and analysed, showing the deposition rate and

stoichiometry of films created by PE-PLD over a range of operating pressures. Analysis with

XRD, SEM, and EDX confirm that we achieved high quality, stoichiometric thin films with our

new PE-PLD technique. Furthermore, we were able to tune the phase of the film from

stoichiometric, (211) Cu2O at an ICP pressure of 7.5Pa, to stoichiometric, (020) CuO at 13Pa.


30

Enhanced control of the ionization rate in radio-frequency plasmas with

structured electrodes via tailored voltage waveforms

Scott J. Doyle1, Trevor Lafleur

2, Andrew R. Gibson

1,2, Peng Tian

3, Mark J. Kushner

3, James

Dedrick1

1York Plasma Institute, Department of Physics, University of York, Heslington, York, YO10 5DD,

UK 2LPP, CNRS, Ecole Polytechnique, UPMC Univ, Paris 06, Univ. Paris-Sud, Observatoire de

Paris, Universite Paris-Saclay, Sorbonne Universites, PSL Research University, 91128

Palaiseau, France 3University of Michigan, Dept. of Electrical and Computer Engineering, 1301 Beal Ave., Ann

Arbor, MI 48109-2122, USA

[email protected]

Radio-frequency (rf) capacitively coupled plasmas that incorporate structured electrodes enable

increases in the electron density within spatially localised regions through the hollow cathode

effect. This enables enhanced control over the spatial profile of the plasma density, which is

useful for several applications including materials processing, lighting and spacecraft propulsion.

However, asymmetries in the powered and grounded electrode areas inherent to the hollow

cathode geometry lead to the formation of a time averaged dc self-bias voltage at the powered

electrode. This bias alters the energy and flux of secondary electrons leaving the surface of the

cathode and consequentially can moderate the increased localized ionization afforded by the

hollow cathode discharge. In this work, two-dimensional fluid-kinetic simulations are used to

demonstrate control of the dc self-bias voltage in a dual-frequency driven (13.56~MHz,

27.12~MHz), hollow cathode enhanced, capacitively coupled argon plasma over the 0.5-1.5 Torr

pressure range. By varying the phase offset of the 27.12 MHz voltage waveform, the dc self-bias

voltage varies by 10-15% over an applied peak-to-peak voltage range of 600-1000~V, with lower

voltages showing higher modulation. Resulting ionization rates due to secondary electrons within

the hollow cathode cavity vary by a factor of 3 at constant voltage amplitude, demonstrating the

ability to control plasma properties relevant for maintaining and enhancing the hollow cathode

effect.


31

Low Temperature Plasmas for Wound Healing Applications

Helen Davies1,2

, Marjan van der Woude2, Deborah O’Connell

1

1York Plasma Institute, Department of Physics, University of York, York, YO10 5DQ

2Centre of Immunology and Infection, Department of Biology, University of York, York, YO10

5DD

[email protected]

Chronic wounds are defined as wounds that do not progress through the normal healing

process, leaving patients open to complications such as infection. Chronic wounds present a

huge socio-economic burden both in the UK and globally, with 1-2% of the population of

developed countries expected to develop a chronic wound in their lifetime. New therapeutic

strategies are being sought to improve wound healing, with the aim of accelerating the normal

healing process to reduce the potential for concurrent wound infection. One potential

therapeutic is the use of low temperature plasma (LTP), which has already been shown to be

effective for killing bacteria and is showing promise in the context of wound healing too.

These promising biological effects are thought to be due to the rich composition of LTP,

comprising Reactive Oxygen and/or Nitrogen Species (RONS), electric fields and charged

particles. At well-regulated, low levels, RONS are known to be vital molecules for normal

cellular function. Crucially, they are known to be involved for all stages of normal,

physiological wound healing and therefore it is thought that these are the most important

plasma components for this application.

This project is concerned with the investigation of low temperature air plasmas, and their

applicability for wound healing applications. In particular, it is hoped that the composition of

different RONS within the plasma can be determined, and a correlation between plasma

composition and biological effect can be determined.

In this work, the initial plasma diagnostics strategies will be discussed, in particular, the

development of a 0D global plasma chemistry model, alongside some initial benchmarking

measurements taken experimentally using picosecond Two-photon Absorption Laser Induced

Fluorescence (TALIF). Development of a carefully benchmarked plasma model can help with

characterisation of plasmas that are difficult to investigate experimentally, as well as help to

guide experiments by indicating how plasma composition may be influenced by changing

plasma parameters (such as power, frequency etc.). In the future, it is hoped that by using a

combination of experimental and computational plasma characterisation, coupled to in vitro

wound healing assays, the influence of plasma composition on biological outcome could be

correlated. This would be interesting when considering tuning plasma composition for

different situations and applications.


32


Abstracts for Poster Presentations


33

Applying tailored voltage waveforms for control of the electron dynamics in

atmospheric pressure plasmas

L. Alelyani1, A. Gibson

2, J.Bredin

2 S. Doyle

2, J. Dedrick

2, T. Gans

2, D. O’Connell

2

York Plasma Institute, Department of Physics, University of York, York YO10 5DD, United

Kingdom [email protected], [email protected]

Atmospheric pressure plasmas have recently been investigated due to their potential for

technological and biomedical applications. They are very efficient sources for chemically

reactive species, for example reactive oxygen and nitrogen species. Precise control of these

reactive species is important for control of the application. The chemical kinetics is initiated by

the electrons, energised through the external electrical power input. Therefore, precise control of

the power input and electron dynamics should provide control of the radicals and other reactive

species in the plasma [1]. We investigate using non-sinusoidal waveforms to control the plasma

electron dynamics on nano-second timescales. Similar strategies have been applied to low

pressure plasmas for ion energy control [2-4]. Due to the strongly collisional environment and

associated short electron energy relaxation times in atmospheric pressure plasmas, close coupling

of the electrons and chemical species, allows control of the chemical pathways.

In this work a fundamental frequency of 13.56 MHz, and adding up to 5 harmonics drives a

capacitively coupled atmospheric pressure plasma. The source geometry is the same as that of the

COST Reference Microplasma Jet [5]. Different waveform shapes including pulse- and

sawtooth-type are applied. Helium is used as a carrier gas with small mixtures nitrogen and argon

(0.05% each). The temporally asymmetric waveforms applied to a geometrically symmetric

plasma induces an asymmetric plasma, accompanied by the formation of a dc self bias. Phase

resolved optical emission spectroscopy (PROES) is employed to study the excitation dynamics in

spatio-temporal with high resolution. There is also a significant change in the electron excitation

mechanisms depending on the waveform and number of harmonics. Control of excitation in both

space and time can be achieved, strongly suggesting potential for control of the chemical

pathways.

References:

1. Gans, T., Schulz‐von der Gathen, V., & Döbele, H. (2004). Prospects of Phase Resolved Optical

Emission Spectroscopy as a Powerful Diagnostic Tool for RF‐Discharges. Contributions to

Plasma Physics, 44(5‐6), 523-528.

2. Lafleur, T. (2015). Tailored-waveform excitation of capacitively coupled plasmas and the

electrical asymmetry effect. Plasma Sources Science and Technology, 25(1), 013001.

3. Bruneau, B., Gans, T., O’Connell, D., Greb, A., Johnson, E. V., & Booth, J.-P. (2015). Strong

Ionization Asymmetry in a Geometrically Symmetric Radio Frequency Capacitively Coupled

Plasma Induced by Sawtooth Voltage Waveforms. Physical review letters, 114(12), 125002.

4. Schulze, J., Schüngel, E., Czarnetzki, U., & Donkó, Z. (2009). Optimization of the electrical

asymmetry effect in dual-frequency capacitively coupled radio frequency discharges: Experiment,

simulation, and model. Journal of Applied Physics, 106(6), 063307.

5. J. Golda, et al. Concepts and characteristics of the ‘cost reference microplasma jet. Journal of

Physics D: Applied Physics, 49(8):084003, 2016.


34

The detection of reactive oxygen and nitrogen species in plasma using

luminescent europium complexes

Colum Breen, Ben Buckley and Stephen J. Butler

Department of Chemistry, Loughborough University, Loughborough LE11 3TU, UK

[email protected]

The use of plasma in medicine and therapeutics (e.g. wound healing, antiseptic treatment) is

an exciting new area of research, due to recent developments in room temperature plasma.2

However, in order to make better use of plasma in medical applications and beyond, better

methods for understanding short-lived reactive oxygen and nitrogen species (ROS/RNS)

within plasma are required.

Herein, a potential candidate for sensing peroxynitrite (ONOO-) and hydrogen peroxide

(H2O2) in plasma based systems is reported (scheme 1). This probe is based on a stable

luminescent europium(III) complex bearing a quinoline chromophore functionalised with a

boronate ester.

The boronate ester has already shown promising results in previous research for sensing

ONOO-.3 In this project, the boronate ester is attached to a quinoline chromophore and upon

oxidation by peroxynitrite (or hydrogen peroxide), it is envisaged that the hydroxyquinoline

group will sensitise the Eu(III) metal centre.4 Furthermore this probe could potentially be

applied to cellular studies of ROS/RNS.

References:

1. D. B. Graves, J . Phys . D Appl . Phys . J . Phys . D Appl . Phys, 2012, 45, 263001–42.

2. M. Keidar, Z. Chen, C. Xiaoqian and L. Lin, J. Phys. D. Appl. Phys., 2017, 50, 15208.

3. N. A. Sieracki, B. N. Gantner, M. Mao, J. H. Horner, R. D. Ye, A. B. Malik, M. E. Newcomb

and M. G. Bonini, Free Radic. Biol. Med., 2013, 61, 40–50.

4. S. J. Butler, M. Delbianco, L. Lamarque, B. K. Mcmahon, E. R. Neil, R. Pal, D. Parker, J. W.

Walton and J. M. Zwier, Dalt. Trans., 2015, 44, 4791–4803.

Scheme 1 - Oxidation of the boronate ester by peroxynitrite/hydrogen peroxide to reveal the hydroxyl group, thus

sensitising the lanthanide metal centre.


35

Magnetron injection gun design for Ka-band MW Gyroklystron

Kun Dong, Li Wang, Jianxun Wang, Yong Luo

School of Physical Electronics, University of Electronic Science and Technology of China

Wenlong He, Huabi Yin, Dian Zhang, Adrian W. Cross, Kevin Ronald, Alan D. R. Phelps

Department of Physics, SUPA, University of Strathclyde [email protected], [email protected]

Gyroklystrons are high-power high-frequency vacuum electronic devices based on the principle

of electron cyclotron maser instability. As a millimetre wave high-power source for accelerators,

a Ka-band gyroklystron is being studied at the University of Strathclyde. This gyroklystron is

predicted to deliver an output power of over 1 MW at an operating frequency of 36 GHz.

A small-orbit electron beam generated from a magnetron injection gun (MIG) is used to interact

with the electromagnetic wave. For better controlling the beam parameters, a triode-type MIG

having two anodes, is adopted. The operating current and voltage of this MIG is 45 A and 95 kV

respectively. The cathode emitting current density was designed to be 20 A/cm2 for pulsed

operation. The velocity ratio (α=vt/vz, where vt and vz are transverse and axial velocity

components, respectively) of the beam was designed to be 1.3, and the design goal of the relative

axial velocity spread Δβz of lower than 5% was achieved.

The design and optimization of the MIG was performed by using the particle-in-cell code

MAGIC. The optimized MIG geometry and beam trajectories are shown in Fig 1(a). The electron

beam can pass through the gun tunnel without any interception. The final Δβz was about 4.1%

when α was kept at 1.3. Fig 1(b) shows the variations of Δβz and α as functions of modulating

anode voltage Vm. It is demonstrated that when Vm grows from 37.5 kV to 38.9 kV, α almost

linearly increases from 1.12 to 1.4, while Δβz is maintained below 5%.

We plan to perform a sensitivity study of the MIG design to investigate the effect of the

dimension tolerances on the performance of the gun.

References: 1. Chu K R, Granatstein V L, Latham P E, et al. A 30-MW Gyroklystron-Amplifier Design for

High-Energy Linear Accelerators[J]. IEEE Transactions on Plasma Science, 1985, 13(6):424-434.

2. J. MARK BAIRD, WES LAWSON. Magnetron injection gun (MIG) design for gyrotron

applications[J]. International Journal of Electronics, 1986, 61(6):953-967.

3. Michizono S, Tsutsui H, Matsumoto S, et al. Electron gun simulation using Magic[J].

International Journal of Computer Applications, 1998, 48(48):511-514.

(a) (b)

Figure 1. The optimized design of the MIG. (a) MIG geometry and beam trajectories and (b) velocity ratio α and axial

velocity spread Δβz as functions of the modulating anode voltage Vm.


36

Using Fluorescent Probes for the Analysis of Reactive Oxygen Species in

Plasma Systems

James Fuster1, B. Buckley

1, F. Iza

2

1Department of Chemistry, Loughborough University, Loughborough, LE11 3TU, UK



[email protected]

In recent years, the advance of atmospheric-pressure, non-thermal plasmas has revolutionized the

field of plasma medicine. A wide range of Reactive Oxygen Species (ROS), which have been

shown to be both vital in critical biological functions, such as homeostasis and cell signalling,

whilst also an indicator for cell damage and numerous diseases, are produced in plasma

systems[1]

. Nonetheless, the chemical composition of the plasma, can vary significantly

depending on the set up[2]

, thus characterization of these plasma systems is of primary

importance in order to fully benefit ROS research in this field. Fluorescence emitted from

chemical probes is an ideal way of monitoring ROS because of its fast response, however,

current methods are limited to testing against individual ROS in low concentrations with little

knowledge of the effects that plasma could have on it. Hence, the aim of this project is to develop

a cross-disciplinary approach to be able to use fluorescent chemical probes in optimised plasma

systems that successfully quantifies fluxes of these produced species.

Figure 1: General schematic for the reaction of the current focus ROS, singlet oxygen, with probes based on

isobenzofuran

A broader expansion on the synthesis of these probes and our future work into how the

fluorescent responses from these probes match with literature will be discussed. Also,

consequently steps into how the plasma set up could be optimised to better control the generation

of specific ROS species will be overviewed.

References:

1. T. Finkel and N. J. Holbrook, Nature, 2000

2. J. He and Y. T. Zhang, Plasma Processes and Polymers, 2012.


37

Surveying plasma chemical kinetics with basic graph theory

Thomas D Holmes, William B Zimmerman

Department of Chemical and Biological Engineering, University of Sheffield, United Kingdom

[email protected]

Plasma chemistry has been gained increased interest in recent years, especially with new

developments in plasma catalysis on the horizon. With or without catalysis, one of the biggest

problems in plasma chemical systems is the sheer number and range of different variables. Some

plasma chemical kinetic simulations have incorporated more than one thousand individual

reactions, many of which have rates that are functions of electric fields which in turn have a wide

range of possible waveforms and frequencies, and have many different methods of being coupled

to the plasma gas. Each of these extra factors contributes to an increasingly vast number of

possible permutations in plasma chemical systems.

In the information age the need to comprehend large amounts of data is certainly not confined to

the study of plasmas. Data visualisation techniques are becoming not just increasingly important,

but increasingly indispensable. One such data visualisation technique is the use of graph theory

for surveying large collections of interconnected pathways. This has been used before for the

study of chemical processes, but does not yet seem to have been used to any appreciable extent

for plasma chemistry.

Here it has been the aim to make a small contribution to the on-going assembly of low

temperature plasma knowledge by demonstrating how graph theory based visualisation may be

particularly useful for rapidly examining different permutations of plasma chemical kinetic

systems. With the use of some open source graph theory software, it can be shown how

suggestions for experiments, recommendations for specific simulation conditions, or even

potential catalysts may be rapidly and intuitively identified using some basic graph theory.


38

Analysis of HIPIMS of Molybdenum Plasma for the Development of Back Contacts for Solar

Cell Applications

Daniel A. L. Loch, Arutiun P. Ehiasarian

Sheffield Hallam University, National HIPIMS Technology Centre, Howard Street, Sheffield UK

[email protected]

The back contact for CIGS solar cells needs to fulfil requirements such as low resistance and high

reflectivity and must be able to withstand high temperatures needed for CIGS deposition.

Molybdenum has been identified as a suitable material for the back contact for CIGS solar cells on

soda lime glass substrates.[1-2] In this study we aim to correlate the plasma properties to the

characteristics of the deposited Mo films to enhance back contact performance.

Plasma analysis was conducted by plasma sampling energy-resolved mass spectroscopy and optical

emission spectroscopy. Measurements were taken in two pressure settings 0.22 Pa and 0.44 Pa. The

voltage was varied from 800 - 1500 V in 175 V steps and the pulse-time was increased from 60-

1000 μs, doubling in length for each setting. The resulting average power was in the range of 0.3-

1.1 kW, the duty-cycle was between 1.8 - 5 %.

Optical emission spectra were measured in the bulk of the magnetic confinement. The Mo- II/Mo-I

optical emission ratio exhibits a rapid reduction in Mo-II content with increasing pulse-time and

voltages below 1150V (fig.1a). For higher voltages the emission ratio is constant.

Mass Spectrometry measurements were taken in the middle of the pulse-time in the substrate

position. The Mo2+/ Mo1+ ratio shows a strong dependence on the discharge voltage (fig.1b). The

discrepancy between OES and ion flux measurements may occur under certain conditions where

high energetic Mo2+ can escape the electric field in the presheath and reach the substrate.

Concurrently, we assume there to be changes in chemistry of the plasma by increased charge

exchange collisions with argon returning to the cathode and substrate, having been repelled by gas

rarefaction in the beginning of the pulse, thus the creation of Mo1+ forcing a reduction in the

Mo2+/Mo1+ ion flux ratio. The influence of ionisation on film morphology is discussed.

References:

1. J. H. Scofield, A. Duda, D. Albin, B.L. Ballard, P.K. Predecki; Thin Solid Films 260 ( 1995) 26-31

2. P M P Salomé, J Malaquias, P A Fernandes and A F da Cunha; J. Phys. D: Appl. Phys. 43 (2010)

345501

Figure 1. (a) Mo II/Mo I Optical emission intensity ratio for increasing pulse duration and discharge voltage at a pressure of

0.22 Pa. (b) Mo2+/Mo1+ ion flux ratio for increasing pulse duration and discharge voltage at a pressure of 0.22 Pa.


39

Atmospheric pressure plasma jet bonding of polydimethylsiloxane cell scaffolds

Matt Moles, Alex Shaw, Felipe Iza, Nick Medcalf

Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough


[email protected]

Polydimethylsiloxane (PDMS) is long established as a biocompatible material for use in vitro and in vivo.

In developing PDMS-based devices joining or bonding of PDMS-to-PDMS may be necessary. An

automated solution is sought for batch production of PDMS-based cell culture scaffolds. As PDMS is

resistant to most acids, alkalis and solvents, plasma bonding is highly suited to this application. It also

omits the need for post-joining cleaning of contaminants.

Ultra-thin PDMS membranes (250 µm) were exposed to a helium plasma jet (2 standard litres per

minute) with a small admixture of oxygen (0.5, 2 or 5%). The plasma was driven by an in-house built

25kVpp - 15kHz power supply and the power delivered to the plasma was limited to ~1W. The jet was

scanned across the PDMS substrate and a custom built programmable XY-translation stage [1] was used

to ensure even and repetitive treatment of PDMS samples. The jet described a grid pattern at 2mm

intervals at a speed of 40mm/s. Two or four scans were performed per sample and the plasma

treatment took around 1 minute to complete. Post-plasma treatment the treated areas of the samples

were pressed together then stored in air for 48 h.

Bond strength was evaluated by the T-peel test (BS ISO 11339-2010 [2]) using a displacement rate of 10

mm/min on an Instron tensile testing machine. Samples were gripped by emery-backed jaws, and failure

always occurred in the gauge length. Actual bond length correlated with both gas composition and number

of passes. Tighter control over the bonded area could be achieved using a higher proportion of oxygen in

the carrier gas. Doubling the exposure time did not significantly change the bond strength.

References:

1. Lisco F, Shaw A, Wright A, Walls J M and Iza F 2017 Atmospheric-pressure plasma surface

activation for solution processed photovoltaic devices Sol. Energy 146 287–97

2. Standardization I O for 2010 ISO 11339:2010 Adhesives -- T-peel test for flexible-to-flexible

bonded assemblies

Ground electrode

Ceramic jet body

High voltage

electrode

Dielectric

Gas flow

Quartz glass tube

PDMS

Start EndStart

End

Step 1 Step 2

Figure 1. Left- the plasma jet used to treat the PDMS samples. Right- The pattern described by the 2-dimensional stage to

treat the PDMS uniformly


40

Space Averaged Mathematical Model of Pulse Powered Atmospheric Pressure

Air Plasma

Faraz Montazersadgh1, Alexander Wright

2 and Alexander Shaw

1, Felipe Iza

1


University, Loughborough LE11 3TU, UK 2Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK

[email protected]

A space averaged mathematical model describing a pulse powered atmospheric pressure air

plasma has been developed and final results are compared with a similar DBD experimental

setup. The atmospheric pressure dry air plasma model consisting of more than 380 reactions and

36 species is developed according to [1]. The system of equations is then solved by a zero-

dimensional global model with a stiff differential equation solver and variable time steps in

Matlab. To verify the model results, long-lived species densities and the gas temperature was

measured in a simple DBD plasma. Gas temperature was measured using a thermocouple

located as close as possible to the plasma and effluent gasses were measured using FTIR.

Although numerical studies have been done on atmospheric pressure plasmas previously [1][2], a

comprehensive research outlining the exact effects of pulsed power input is yet to be done. It is

seen that the same power input with different duty cycle percentage results in a massive

difference in effluent gas composition, especially in industrial ozone generation equipment.

While the gas temperature plays an important role in the gas density evolution, it is seen that this

is not the only effective factor.

Figure 1: Ozone density vs time, model (top) and experiment (bottom).

References:

1. Y. Sakiyama, D. B. Graves, H.- W. Chang, T. Shimizu, and G. E. Morfill, “Plasma chemistry

model of surface microdischarge in humid air and dynamics of reactive neutral species,” J. Phys.

D. Appl. Phys., vol. 45, no. 42, p. 425201, 2012.

2. C. Riccardi and R. Barni, “Chemical Kinetics in Air Plasmas at Atmospheric Pressure,” Chem.

Kinet., pp. 185–201, 2012.

mailto:[email protected]


41

Enhancement of mass transfer rate of plasma reactive species in gas-liquid

phases with a Microfluidic plasma reactor

O. Ogunyinka1, A. Wright1, A. Shaw2, H. Bandulasena1, F. Iza2 1Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK


University, Loughborough LE11 3TU, UK

[email protected]

There have been various studies on the treatment of volatile organic compounds in liquids via

oxidation from reactive species from the interference of plasma and liquid phases. These species

are short-lived hence require high mass transfer between the two phases. To enhance this

process, a microfluidic plasma reactor has been designed whereby dielectric barrier discharge

plasma is transferred into gas-liquid interface. The process is enabled using two metal rods acting

as electrodes are coated with quartz and placed across a gas-liquid flow channel to generate an

electric discharge. Interference occurs at a microchannel connection which enhances mass

transfer rate of the species due to microbubble formations.

This device reaction has been analysed whereby an indigo solution is oxidised by the reactive

species by measuring the reduction in the indigo concentration in the solution which is

manipulated by the breaking of C=C bonds in the indigo compound. The measurement was

examined via the absorption spectrum of 600nm light by the indigo compounds in the solution. It

was discovered that rate of the oxidation was dependent duty cycle of the plasma discharge. In

addition a fluidic oscillator for gas flow optimises the rate of the reaction.

Figure 1- Oxidation of indigo compound


42

Modelling the interaction of gas–plasma jets with liquids

Juliet Chinasa Ojiako

Department of Mathematical Sciences, Loughborough University, LE11 3TU, UK

[email protected]

Gas–plasma interactions with liquids find applications in industries and medicine. We aim to

model the interaction of a plasma jet with a liquid accounting for hydrodynamics,

electrodynamics and chemical kinetics. This involves the calculation of flows generated in the

gas and in the liquid, the rate at which the generated long-lived and short-lived plasma species

are transferred to the liquid, as well as feasibility of chemical reactions. For a start, we aim to

reproduce and model the experiment of van Rens et al. [1], as shown in figure (a), who

considered the interaction of a plasma jet with a liquid in a cubic reactor of size 3×3×3 cm. The

jet was placed above the liquid surface and it was found that it generated a cavity on the liquid

surface as well as eddies inside the liquid, which affect the transfer of plasma particles into the

liquid.

We start by modelling only the hydrodynamic part of the experiment without the plasma, i.e., we

consider a gas jet impinging on a liquid surface. The future aim is to analyse how the plasma jet

will affect the flow patterns and chemical reactions within the system.

To this end numerical simulations in COMSOL were performed. The best solution was found

when the gas and the liquid problems were decoupled, which was an appropriate approximation

under the conditions of the experiment. We also implemented an analytical model in MATLAB

using the thin film equations. Figure (b) shows the simulation of the experiment. The results are

in good qualitative agreement.

(A) (B)

(A) A REPRESENTATION OF THE VAN RENS ET AL. [1] EXPERIMENT SHOWING THE INTERFACE SHAPE AND THE FLOW

PROFILE IN THE LIQUID INDUCED BY THE PLASMA JET. (B) THE AXI-SYMMETRIC SIMULATION OF THE FLOW PATTERN

USING THE DECOUPLED MODEL IN COMSOL. NOTE THAT BECAUSE OF AXIAL SYMMETRY ONLY HALF OF THE IMAGE

MODELLED IN (A) IS SHOWN.

References: 1. J. F. M. van Rens, J. T. Schoof, F. C. Ummelen, D. C. van Vugt, P. J. Bruggeman, and E. M. van

Veldhuizen. Induced liquid phase flow by rf ar cold atmospheric pressure plasma jet. IEEE

Transactions on Plasma Science, 42:2622–2623, 2014.


43

Atmospheric-Pressure Plasma Device for CO2 Conversion and Utilization

A.Randi1, F. Iza

2, U. Wijayantha

1, A. Shaw

2 , B.R. Buckley

1

1Department of Chemistry, Loughborough University, United Kingdom


University, United Kingdom

[email protected]

The increasing levels of CO2 in the atmosphere and its consequential impact on global

warming is driving many research groups to develop ways to use CO2 as raw material. A

wide variety of approaches to carbon dioxide utilisation have been reported employing

homogeneous catalysis, heterogeneous catalysis, photocatalysis, photoreduction and

electrochemical reduction.

Besides the reduction of greenhouse gases, by producing feedstocks using CO2 will greatly

reduce our dependence of fossil fuels for chemical synthesis. Our previously reported

electrochemical processes have proven to be successful in terms of electron transfer between

substances at room temperature and atmospheric pressure (See Scheme), in this we have

explored the use of substituted acetylenes (See Scheme) to give selectively mono-

carboxylated products.

Atmospheric-pressure plasmas interacting with organic liquids offer a new possibility for

chemical synthesis that remains largely unexplored. Here we report on the results obtained

with a Jet device in which chemical reactions are triggered in an organic liquid by an

atmospheric-pressure plasma.

As a proof-of-concept, we considered the incorporation of CO2 into an alkyne to form a

carboxylic acid. Here we explore plasma reduction. A CO2 saturated solution of

diphenylacetylene in Tetra-n-butylammonium iodide (Bu4NI), Triethanolamine (TEOA) and

Dimethylformamide (DMF) and an argon DC plasma is used as a gaseous cathode to provide

electrons for the reduction of CO2. Gas chromatography (GC) and nuclear magnetic

resonance (NMR) analysis indicate the formation of 2,3 diphenylpropanoic acid with good

selectivity although further optimization is needed to increase yield and increase the power

efficiency of the device.

References:

1. Jhong HM, Ma S, Kenis PJ Electrochemical Convrsion of CO2 to useful chemicals: current

status, remaining challenges, and future opportunities, Chemical Engineering 2013 2: 191-

199.

2. Richmonds, C., Witzke, M., Bartling, B., Lee, S. W., Wainright, J., Liu, C.-C., & Sankaran, R.

M. (2011). Electron-Transfer Reactions at the PlasmaÀLiquid Interface. J. Am. Chem. Soc,

133, 17582–17585.


44

Plasma liquid interface for CO2 Conversion and Utilization

M. Shaban1, A. Randi

2, A. Shaw

1, B.R. Buckley

2 and F. Iza

1


University, Loughborough LE11 3TU, UK 2Department of Chemistry, Loughborough University, Loughborough LE11 3TU, UK

[email protected]

Atmospheric pressure plasmas are used in material processing, in lighting applications, for

plasma thrusters and for numerous biological applications [1-3]. Bearing in mind the importance

of plasma liquid interaction, this research aim to focus mainly on plasma interaction with organic

liquids and exploring the phenomena associated with it. The device built during this research

uses CO2 as raw material.

The increasing levels of CO2 in the atmosphere and its consequential impact on global warming

are driving research to develop ways to utilize CO2 as raw material to produce useful products.

Previously reported electrochemical processes have shown possibility of electron transfer

between substances. In this research, we discuss the employment of atmospheric pressure plasma

with liquid for CO2 using a microfluidic device. We are trying to move from batch treatment to

continuous flow treatment. Some of the results obtained so far from this research are presented in

here. Different techniques of bubbling CO2 in the solvent (DMF) are being used. The ionized gas

carries free electrons which in turn reduces the CO2 forming carboxylic acid in the presence of

alkyne. The results of the reaction are analysed using GCMS.

Figure 1 shows CO2 concentration curve and cross sectional view of continuous flow plasma

driven reaction cell. In future, we plan to use multiple interaction cycles of the same CO2

saturated DMF to observe if more plasma contact with the liquid increases the product and

utilization of CO2.

Figure 2. (a) Number of photons absorbed by the solution (b) Cross sectional view of microfluidic device.

References: 1. K. H. Schoenbach, A. El-habachi, W. Shi, V. Martin, G. Bauville, and M. Fleury, “Micro plasma

and applications,” J. Phys. D. Appl. Phys., vol. 39, 2006

2. C. G. Wilson and Y. B. Gianchandani, “Silicon Micromachining Using In Situ DC Micro

plasmas,” J. microelectromechanical Syst., vol. 10, no. 1, pp. 50–54, 2001.

3. M. Moselhy et al., “Xenon excimer emission from pulsed micro hollow cathode discharges,”

Appl. Phys. Lett., vol. 1240, no. 9, 2001


45

Removal of pharmaceuticals in waste water through Non-Thermal Plasma

Treatment to impede Antimicrobial Resistance

Kay Tor, Chedly Tizaoui

Swansea University [email protected]

Antimicrobial resistance (AMR) is a serious global threat to humans. Wastewater has recently

been found as a source of AMR due to the ever-increasing emissions of antimicrobial substances

in the sewer systems. The situation is highly critical and given the high rate and widespread of

these antimicrobial resistant genes in the environment, it is likely that within a few years, existing

antimicrobial drugs will not be effective. Hence there is an urgent need to develop effective

technologies to limit the widespread of AMR causing compounds in the environment via

effective wastewater treatment. AMR which was declared by the WHO in 2012 as “a complex

problem driven by many interconnected factors; single, isolated interventions have little impact”,

is also regarded as a new serious type of environmental pollutant due to its potential to be

transmitted from the environment to human pathogens as well as its negative impact on the

environmental microbiota [1,2].

There has been increasing interests in non-thermal plasma (NTP) in recent years due to its ability

to produce highly reactive species (e.g. O3, •OH, e-, UV) and chemistries suited to oxidise

organic contaminants whilst simultaneously disinfecting the water. Although treatments such as

chlorination are commonly used to treat water, they are known to produce disinfection by-

products (DBPs) such as trihalomethanes, a carcinogen. The concentration of DBPs are

monitored and disinfectants such as Chlorine are only kept in used because, as reported by the

World Health Organisation (WHO), “the risks to health from these by-products are extremely

small in comparison with the risks associated with inadequate disinfection” [3]. There is

therefore, an urgency to utilise AOPs such as NTPs for water treatments.

Preliminary experiments are focused on the degradation of Azithromycin; prior to plasma

treatment, the degradation of the drug with some reactive species were analysed individually for

a better insight to the behaviour of the drug with different species. A pin to plate electrode

configuration is then used for the plasma treatment where the pin (high voltage) is in the gas

phase (air), and the plate (ground) is in liquid phase (deionised water). Initial results are

promising in showing drug degradation with plasma treatment and advanced oxidative species.

Future analysis will endeavour to determine the by-products of the process.

References: 1. Harbarth, S., Samore, M. H., Antimicrobial Resistance Determinants and Future Control.

Emerging Infectious Diseases, 11(6), 794-801 (2005).

2. Xi, C., Zhang, Y. et al., Prevalence of Antibiotic Resistance in Drinkig Water Treatment and

Distribution Systems. Applied and Environmental Microbiology, 75(17), 5714-5718 (2009).

3. World Health Organisation, Guidelines for drinking water quality, Third Edition, (2008).


46

Modeling of the particle fluxes of a helium plasma jet onto water surface

Sui Wang1,2

, Dingxin Liu1, Xiaohua Wang

1, Felipe Iza

2

1State Key Laboratory of ElectricalInsulationand Power Equipment, Centre for Plasma

Biomedicine, Xi’anJiaotong University, Xi'an City 710049, P. R. China 2Wolfson School of Mechanical, Electrical& Manufacturing Engineering, Loughborough

University, LE11 3TU, United Kingdom

[email protected]

Atmospheric pressure plasma jets (APPJ) hold great prospects in biomedical applications in

which the targets of plasma treatment arenormally in moisture circumstance or even covered

by a thin liquid layer[1]

.In this work, we simulated the interaction between helium APPJ and a

petri dish of deionized water. The purpose was to quantify the radial distributions of particle

fluxes of reactive species on the water surface, as well as elucidate their dependence on the

mixture of the surrounding air and the water evaporation.

An axisymmetric 2-D fluid model was firstly used to obtain the spatial distribution of the

feedstock gases before discharge, and then a series of 0-D models for the boundary layer of

the plasma were used to quantify the particle fluxes. The plasma area of interest was

simplified to a cylindrical layer covering the water surface, with a thickness of 200μm[2]

and a

radius of 1mm. The cylindrical layer was further divided into four coaxial elements from the

center to the outer edge. For each element, a global model was established to simulate the

discharge.

Due to the mixture of ambient air and water evaporation, the concentrations of N2 and O2 in

the thin boundary layer to be modeled were in the order of several tens of ppm and the

relative humidity was higher than 30%. Except for ozone, the particle fluxes of reactive

species reveal a downward trend as one moves away from the centre of the plasma. The

fluxes of HNO3 and NO3 reach a maximum value at a distance of 0.25-0.5mm away from the

axis of the jet, as shown in figure 1. The particle flux of OH has the lowest decreasing rate

and the particle flux of H2O2 is the largest with a value of over1020

m-2

s-1

. The particle fluxes

of OH, HO2, HNO2 and HNO3 on the water surface are also remarkably high with values

above 1017

m-2

s-1

.

References:

1. Norberg S A, Tian W, Johnsen E, et al., J. Phys. D: Appl. Phys.47, 475203 (2014).

2. Liu D X, Yang A J, Wang X H et al.,J. Phys. D: Appl. Phys. 45 305205 (2012).

Figure 3.Radial distributions of particle fluxes of neutral species on the water surface(a) RNS (b) ROS.


47

Pre-treatment of a faecal simulant for bio-ethanol production with a novel

microbubble enhanced DBD plasma reactor

A. Wright, A. Marsh, A. Shaw, G. Shama, F. Iza, H. Bandulasena

Chemical Engineering, Loughborough University, LE11 3TU, United Kingdom

[email protected]

It is now widely known both within and outside of the scientific community there is a shortage of

renewable energy options to replace the diminishing supply of fossil fuels. In recent years

biomass has been seen as a sustainable alternative to provide a transport fuel for the growing

number of vehicles on the roads. Here a cellulose rich product is fermented to form ethanol via

an intermediary of glucose. However the existing methods for the breakdown of cellulose are

either energy intensive or have a high consumption of chemicals. Atmospheric pressure plasma

has been identified as one way of reducing the cost of biomass pre-treatment.1

Several biomass feed stocks have been investigated but feasibility is limited due to cost of

production and processing. One feed stock that is not limited by these factors is faecal slurry

which is high in cellulose and is seen as a waste to many. In this study cellulose, one of the major

components of faecal slurry2 was treated in a microbubble enhanced DBD plasma reactor. The

degree of solubility in sodium hydroxide and the percentage of realised sugars when hydrolysed

were used a measure of effectiveness.

Figure 1 (a) shows that as the cellulose is treated the solubility rapidly increases over the first 30

minutes before plateauing and reaching a maximum after 90 minutes. This indicates that the

highly crystalline structure of the cellulose is being broken by the reactive species produced from

the plasma. This is further evident in figure 1 (b) which shows how the glucose concentration is

higher for a cellulose samples that has been treated for a longer period of time.

Figure 4: (a) shows the effect of pre-treatment time on the solubility of cellulose and (b) the measured glucose

concentration.

References:

1. Esrey, S.A. (2000). Towards a recycling society. Ecological sanitation – closing the loop to food

security. In proceedings of the international symposium, 30–31 October, 2000. Bonn, Germany.

GTZ, GmbH. 2001

2. A Wright et al. (2017). Dielectric Barrier Discharge Plasma Microbubble Reactor for

Pretreatment of Lignocellulosic Biomass. AIChE (submitted).

0102030405060708090

100

0 30 60 90 120

Solu

bili

ty (

%)

Pretreatment Time (Mins)

0

2

4

6

8

10

0 1 2 3 4 5

Glu

cose

Co

nc.

(g/

l)

Hydrolyis Day

30 Mins Treatment

60 Mins Treatment

90 Mins Treatment

120 Mins Treatment

(a) (b)


48

Performance Optimisation of Plasma Closing Switch Filled With

Environmentally Friendly Gases

Y. Yao, I. Timoshkin, M. P. Wilson, M. J. Given, T. Wang, S. J. MacGregor

Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, 204

George Street, G1 1XW, United Kingdom

[email protected]

One of the critical components in the high energy density pulsed power systems which are used

to generate short high-voltage, high-power (10s MW to several GW), impulses is a gas filled

plasma closing switch. In recent years significant research efforts have been aimed at finding

environmentally friendly gases with advanced dielectric properties which can be used as

substitution for SF6 [1] in the plasma closing switches. Several gases have been considered as

potentially suitable alternatives including Zero Grade air, nitrogen, carbon dioxide and their

mixtures. However, the lack of knowledge of their dielectric behaviour limits their practical

applications as working fluids in the plasma closing switches. Therefore, further investigation of

the dielectric characteristics of such gases is required in order to establish their applicability for

practical use in high voltage high power pulsed power systems.

The present paper investigates the breakdown and pre-breakdown characteristics of Zero Grade

air, N2, CO2 gases and Ar/O2 gas mixture. A dedicated two-stage plasma closing switch with

highly divergent electric field has been designed and constructed (Figure 1). The sharp needle

electrodes attached to the central trigger electrode are used to generate pre-breakdown non-

thermal plasma (corona) discharges to achieve potential corona stabilisation effect. It was shown

that the designed switch can operate under both positive and negative voltage stress. The

operational characteristics of the switch has been obtained for all tested gases in the pressure

range from 1 bar to 10 bar (absolute). The obtained results will help to identify gas type and

pressure to achieve the optimal performance of the plasma closing switch.

References:

1. “Novec™ 5110 dielectric fluid”, 3M Technical Data,

http://multimedia.3m.com/mws/media/1132123O/3mnovec-5110-dielectric-fluid.pdf

Figure 5. A cross-section of the plasma switch with 4 needle electrodes on each side of the central plate.


49

QDB: a database of plasma process data

C. Hill1, S. Rahimi

1, D. B. Brown

1, A. Dzarasova

1, J. R. Hamilton

2, S. Zand-Lashani

1, S. Mohr

1,

J. Tennyson1,2

1Quantemol Ltd, 320 City Road, EC1V 2NZ

2University College London, Gower Street, WC1E 6BT

[email protected]

Plasma-assisted atomic layer deposition processes have become more and more popular and

increasingly enable better control and achieve high precision [1]. Plasma processes are widely

used in semiconductor manufacturing and are notoriously hard to control. One of the key factors

in plasma chamber design and process optimisation becomes modelling of the plasma kinetics

and understanding of plasma–surface interaction. This is also a key to understanding processes

on the atomic scale where different laws of physics could apply and scaling becomes non-linear.

We have established a database [3] for plasma chemistry including surface interactions, QDB,

which aims to become a basis for ALD modelling and plasma modelling in general for tool

manufacturers and others interested in research in this area [2].

The web software provides a platform for users to upload, compare and validate such data and

exposes an API for its automated retrieval in a range of formats suitable for use in modelling

software. The service currently has both academic and commercial users and its development is

overseen by an international Advisory Board comprised of active researchers in theoretical and

experimental plasma science. Data is input from both experimental and theoretical sources by

Quantemol staff and by our community of users.

In this presentation, we will describe recent developments in QDB: the increased provision of

data relating to (a) heavy-particle processes (chemical reactions) and (b) the interaction of

particles with surfaces. This has required the expansion of the QDB data model to include a

characterization of the surface (substrate) composition and structure as well as the description of

the behaviour of individual adsorbed species (desorption energy, diffusion energy, etc.)

It is hoped that the database and its associated online web application software and API will

prove useful to the International Plasma Chemistry Research community: an illustrative example

is given in our presentation.

QDB is available at https://www.quantemoldb.com/

References: 1. H. B. Profijt et al., J. Vac. Sci. Technol. A 29, 050801 (2016)

2. Markku Leskelä and Mikko Ritala, Angew. Chem. Int. Ed. 42, 5548 (2003)

3. J. Tennyson et al., Plasma Sources Sci. Technol. 26 055014 (2017)


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Ricoh Arena 3D Floor Map

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15th technological plasma workshop programme and book of … · 2018. 10. 25. · 15th...

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