Dr Davide Mariotti. Plasma-particle interactions at atmospheric pressure: from inorganic nanoparticles synthesis to bacteria charging.

Transcription

1 Plasma-particle interactions at atmospheric pressure: from inorganic nanoparticles synthesis to bacteria charging Dr Davide Mariotti Reader Nanotechnology & Integrated Bio-Engineering Centre (NIBEC) University of Ulster (UK)

2 Plasmas & Nanoparticles at the University of Ulster Acknowledgements Prof Maguire Plasma Nanofabrication Group Research Fellow Dr Charles Mahony Dr Mariotti Plasma Science & Nanoscale Engineering Group PostDocs Dr Manuel Macias-Montero Dr Jenish Patel Dr SomakMitra PostDocs Dr Mark Tweedie Dr Sun Dan PhD Students David Rutherford Admin Staff Gillian Conlane PhD Students Sadegh Askari Tamilselvan Velusami Conor Rocks Calum McDonald Atta Ul Haq

3 Current financial support & partners EPSRC All Inorganic Bulk Heterojunction Solar Cell Devices (n.ep/k022237/1) University of St. Andrews (UK), Prof. Irvine Leverhulme International Network (n.in ) AIST (Japan), Dr Švrcek Bochum University (Germany), Prof. Benedikt Instiut Jean Lamour (France), Prof. Belmonte Royal Society (n.ie ) AIST (Japan), Dr Švrcek EPSRC Microplasma-assisted manipulation of intact airborne bacteria for real time autonomous detection (n.ep/k006088/1) University of Glasgow (UK): Prof. Diver, Dr Potts, Dr Bennet Invest NI The Lab nanometal-manufacturing System (n.poc-325) FP7-PEOPLE-2013-ITN RAPID (n ) coordinated by Bochum University (Germany), Prof. Von Keudell NATO-SPS Atmospheric Pressure Plasma Jet for Neutralisation of CBW (n. EAP,SFPP ) coordinated by Joseph Stefan Institute (Slovenia), Prof. Cvelbar

4 Low-temperature atmospheric pressure plasmas Non-equilibrium atmospheric pressure plasmas Low-temperature (gas K; T e > 1 ev) Micro-/millimeter scale confinement ( mm diameter) RF (13.56 MHz) with DC-pulse ignition/triggering Various configurations two-ring configuration: AskariS, Mariotti D et al. Appl. Phys. Lett.104, 2014,

5 From inorganic, droplets to bacteria Gas precursors (or solid/liquid) Nanoparticles Aerosol Droplets Aerosol With bacteria charged bacteria Bacteria inert gas background (e.g. He, Ar, Ne etc.)

6 CARBON NANOSTRUCTURES SEMICONDUCTOR NPs & ALLOYS Mariotti D et al. Trans. of the Mat. Res. Soc. of Japan 31, 2006, 463 Mariotti D et al. Eur. Phys. J. Appl. Phys. 56, 2011, GOLD NANOPARTICLES ON PAPER NANO-METAL COTAINGS Mariotti D et al. Microprocesses and Nanotechnology 2007 Digest of papers COMPOSITE COATINGS Mariotti D et al. J. Phys. D: Appl. Phys. 42 (2009) Metal-OXIDE NANOSHEETS Mariotti D et al. Nanotechnology 19, 2008, Mariotti D et al. D: Appl. Phys. 43, 2010, (Topical Review) Mariotti D et al. J. Phys. D: Appl. Phys. 44, 2011, (Special Issue) METAL OXIDES NANOPARTICLES METAL OXIDES NANORODS Mariotti D et al. IEEE Transactions on Plasma Science 37, 2009, 1027 Mariotti D et al. Nanotechnology 17, 2006, 5976; Mariotti D et al. Jpn. J. Appl. Phys. 45, 2006, 8228

7 Quantum confined silicon and silicon-carbide nanoparticles

8 Why quantum confined crystalline silicon nanoparticles? Solar cells based on quantum confined silicon NCs to exploit carrier multiplication and increase efficiency above the theoretical limit Mariotti D et al.j. Phys. D: Appl. Phys.43, 2010, Mariotti D et al. J. Phys. Chem. C115, 2011, 5084 Mariotti D. et al.jpn. J. Appl. Phys.51, 2012, 10NE25 Mariotti D. et al.appl. Phys. Lett.100, 2012,

9 Quantum confined crystalline silicon nanoparticles MHz applied to a copper electrode with 1 mm distance from ground electrode Quartz capillary with 0.7 mm internal and 1 mm external diameter 250 sccm total flow of argon with 10 ppm silane 2-4 nm diameter nanoparticles Askari S, Mariotti D et al. Appl. Phys. Lett. 104, 2014,

10 Configurations for increased throughput and surface area For photovoltaic applications we need to produce films of Si nanoparticles We need to increase the throughput and also the surface are coverage Allows increasing the flow (and increasing the plasma length) without changing the plasma properties extending the configuration in one direction allows covering a larger surface area

11 Deposition of quantum confined silicon nanoparticles films Still working on control of porosity, uniformity, thickness Necessity of codeposition with other materials Further scale-up

12 Mariotti D et al. Phys. Rev. E80, 2009, further scale-up

13 Silicon-carbide nanoparticles: controlling size with the precursor concentration Quartz rectangular capillary with 0.5 mm internal gap and 0.3 mm thickness 1 slmargon background gas sccm argon flown through a bubbler with tetramethylsilane(tms) The TMS flow determine the precursor concentration and nanoparticle size Counts ~2.2 nm 5 Counts Particle diameter/nm Particle diameter/nm ~4.2 nm Increasing TMS concentration Counts ~6.5 nm 0 Particle diameter/nm

14 Why do particles crystallizeat low gas temperature? Gas temperature ~490 K Electron temperature ~1.1 ev Electrons initially negatively charge particles then the ion current contribute to particle heating Steady-state energy balance at the surface yields: OML model valid for low-collisionality CC Model valid for higher collisionality (our case) AskariS, Mariotti D et al. Appl. Phys. Lett.104, 2014,

15 Plasma interactions with droplets and bacteria

16 Studying electro-mechanical properties of live bacteria Gas Flow Charging Step Plasma Bacteria Detection Step Charged Bacteria Electrode Array to excite bacteria oscillation

17 Aerosol-plasma

18 A complicated scenario for droplets As seen before electron/ion currents contribute to particle heating and this is still applicable to liquid droplets (water/ethanol mixtures here) HEATINGinduces droplet evaporation so that these are expected to reduce in size as they travel through the plasma CHARGING. The high electron mobility does induce a net charge on the droplet which can reduce the droplet size by electrostatic repulsion at the Rayleigh limit CHEMISTRY. Finally, the electron current also induces a form of electrochemistry, inducing reactions within the droplets; it is important to underline that this is different from gas-phase plasma chemistry

19 Theoretical analysis of droplet charging and evaporation Droplet evaporation Initial charging Loss of charges due to evaporation in the plasma Loss of charges and reduction of size at the Rayleigh limit

20 Experimental observations: imaging set-up

21 Analysis of droplets size/velocity through the plasma Plasma OFF Gas velocity 23.9m/s Distance from tube 4mm Exp time 20µs 500 Images 20 minutes total time Droplet A Long Narrow Feature (in focus) Diameter = 40µm Velocity = 26m/s Droplet B Long Flat Feature (out of focus) Diameter = 93µm Velocity = 7.4m/s Droplet C Short Hollow Feature (out of focus) Diameter = 245µm Velocity = 1.5m/s

22 Analysis of droplets size/velocity through the plasma Plasma OFF Droplet Diameter (microns) Droplet Diameter (microns) STATB d=4 mm, Plasma OFF, vgas=23.9 m/s Droplet Velocity (m/s) Plasma ON STATD d=4 mm, Plasma ON, vgas=23.9 m/s Droplet Velocity (m/s) Droplet Diameter (microns) Droplet Diameter (microns) Droplet Velocity (m/s) STATF, d=1.5 mm, Plasma ON, OFFvgas=23.9 m/s STATE d=1.5 mm, Plasma ON, vgas=23.9 m/s Droplet Velocity (m/s) Droplet Diameter (microns) Droplet Diameter (microns) STATG d=1.5 mm, Plasma OFF, vgas=45.1 m/s Droplet Velocity (m/s) STATH d=1.5 mm, Plasma ON, vgas=45.1 m/s Droplet Velocity (m/s) analysis in progress

23 plasma Water + HAuCl 4 Patel J, Mariotti D et al. Nanotechnology 24, 2013,

24 plasma plasma + Ti-S plasma Water Water + H 2 O 2 Ti-S: Titanium (IV) Oxysulfate- sulfuric acid Patel J, Mariotti D et al. Nanotechnology 24, 2013,

25 Plasma interactions with droplets and bacteria

26 Deposition of charges on bacteria Charged and wet bacteria Charge (i.e. electrons) Charged and dry bacteria Electron-induced chemistry Evaporation at the Rayleigh limit Evaporation due to droplet heating Plasma Different types of electron-induced chemistry Plasma gas-phase chemistry via diffusion

27 Are charged bacteria alive? Bacteria Aerosol Plasma - raw Bacteria Aerosol Plasma - incubated Bacteria Aerosol - incubated Sterility - incubated

28 Are charged bacteria alive? 0 W 80 W 100 W 120 W Bacteria Aerosol - incubated Bacteria Aerosol Plasma - incubated Bacteria Aerosol Plasma - incubated Bacteria Aerosol Plasma - incubated Are alive bacteria really charged? What is killing bacteria at high power? Is it chemistry?

29 Dr Davide Mariotti Reader Nanotechnology & Integrated Bio-Engineering Centre (NIBEC) University of Ulster (UK)