DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster]

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster

Atmospheric-pressure plasma surface activation for solution processed photovoltaic devices

Atmospheric solution based processes are being developed for the fabrication of thin film photovoltaic devices. Deposition techniques such as electrodeposition, spin coating, spraying or printing are promising techniques to increase the throughput and reduce the cost per Watt of Copper-Indium-Gallium-Selenide (CIGS), Copper-Zinc-Tin-Sulphide (CZTS) and perovskite thin film solar technologies. All these technologies require pre-treatment of the substrate prior to the deposition of the thin film and ideally this pretreatment should also be performed at atmospheric pressure. Results presented in this paper show that use of an atmospheric-pressure plasma is highly effective in activating the surface of substrates commonly used in thin film photovoltaic (PV) device fabrication. Surface activation improves the adhesion of thin films. The use of an atmospheric activation process is compatible with a continuous vacuumfree PV fabrication process. Soda lime glass (SDL) and fluorine doped tin oxide (FTO) coated glass are substrates commonly used in the fabrication of photovoltaic modules. These substrates have been surface treated using a He/O2 atmospheric-pressure plasma, resulting in increased surface energy as evidenced by Water Contact Angle (WCA) measurements. The pre-treatment reduces adventitious surface contamination on the substrates as shown using X-ray Photoelectron Spectroscopy (XPS) measurements. The advantages of using the atmospheric plasma surface pre-treatment has been demonstrated by using it prior to atmospheric deposition of Cadmium Sulphide (CdS) thin films using a sonochemical process. The CdS thin films show pinhole-free coverage, faster growth rates and better optical quality than those deposited on substrates pre-treated by conventional wet and dry processes

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster]

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster

Quantification of the ozone dose delivered into a liquid by indirect plasma treatments: method and calibration of the Pittsburgh Green Fluorescence Probe

Determination of the ozone dose delivered into liquids by plasma systems is of importance in many emerging plasma applications, such as plasma medicine. Quantifcation of this dose remains extremely challenging due to the complex physico-chemical processes encountered in the gas plasma, the plasma–liquid interface and the liquid itself. Chemical probes have the potential to address the limitation of more traditional plasma diagnostic techniques but most commercial chemical probes are not specifc enough to be used in plasma applications. Here we report on the development of a method for the quantifcation of the ozone delivered into a liquid using Pittsburgh Green, a novel ozone-selective fuorescence probe. Entailed within this work is a method for the preparation of the probe solutions, the design of a calibration system and a normalized calibration curve correlating fuorescence intensity to actual ozone dose delivered to the liquid. This enables the quantitative comparison of ozone measurements performed with diferent spectrofuorometers and in different institutions

Microbubble-enhanced dielectric barrier discharge pretreatment of microcrystalline cellulose

Cellulose recalcitrance is one of the major barriers in converting renewable biomass to biofuels or useful chemicals. A pretreatment reactor that forms a dielectric barrier discharge plasma at the gas-liquid interface of the microbubbles has been developed and tested to pretreat α-cellulose. Modulation of the plasma discharge provided control over the mixture of species generated, and the reactive oxygen species (mainly ozone) were found to be more effective in breaking-up the cellulose structure compared to that of the reactive nitrogen species. The effectiveness of pretreatment under different conditions was determined by measuring both the solubility of treated samples in sodium hydroxide and conversion of cellulose to glucose via enzymatic hydrolysis. Solutions pretreated under pH 3 buffer solutions achieved the best result raising the solubility from 17% to 70% and improving the glucose conversion from 24% to 51%. Under the best conditions, plasma-microbubble treatment caused pronounced crevices on the cellulose surface enhancing access to the reactive species for further breakdown of the structure and to enzymes for saccharification

Staphylococcus aureus resists UVA at low irradiance but succumbs in the presence of TiO2 photocatalytic coatings

The aim of this study was to evaluate the bactericidal effect of reactive oxygen species (ROS) generated upon irradiation of photocatalytic TiO2 surface coatings using low levels of UVA and the consequent killing of Staphylococcus aureus. The role of intracellular enzymes catalase and superoxide dismutase in protecting the bacteria was investigated using mutant strains. Differences were observed in the intracellular oxidative stress response and viability of S. aureus upon exposure to UVA; these were found to be dependent on the level of irradiance and not the total UVA dose. The wild type bacteria were able to survive almost indefinitely in the absence of the coatings at low UVA irradiance (LI, 1 mW/cm2), whereas in the presence of TiO2 coatings, no viable bacteria were measurable after 24 h of exposure. At LI, the lethality of the photocatalytic effect due to the TiO2 surface coatings was correlated with high intracellular oxidative stress levels. The wild type strain was found to be more resistant to UVA at HI compared with an identical dose at LI in the presence of the TiO2 coatings. The UVA-irradiated titania operates by a “stealth” mechanism at low UVA irradiance, generating low levels of extracellular lethal ROS against which the bacteria are defenceless because the low light level fails to induce the oxidative stress defence mechanism of the bacteria. These results are encouraging for the deployment of antibacterial titania surface coatings wherever it is desirable to reduce the environmental bacterial burden under typical indoor lighting conditions

EHD-driven mass transport enhancement in surface dielectric barrier discharges

Surface Dielectric Barrier Discharges (S-DBDs) have received renewed attention in recent years for their potential application in emerging biomedical, environmental and agricultural applications. In most of these applications, the plasma is not in direct contact with the substrate being treated and the transport of reactive species from the plasma to the substrate is typically assumed to be controlled by diffusion. Here, we demonstrate that generally this is not the case and that electrohydrodynamic (EHD) forces can produce jets that enhance the delivery of these species, thereby influencing the efficacy of the S-DBD device. In particular, we have studied the degradation of potassium indigotrisulfonate solutions exposed to S-DBDs generated in devices with annular electrodes of diameters varying between 10mm and 50mm. All the devices were driven at constant linear power density (Watts per cm of plasma length) and although local plasma properties remained the same in all the devices, a three-fold efficacy enhancement was observed for devices of diameter ~30mm due to EHD effects

A microbubble plasma reactor for pretreatment of lignocellulosic biomass [Abstract]

A microbubble plasma reactor for pretreatment of lignocellulosic biomass [Abstract

Surface activation of rigid and flexible substrates for thin film photovoltaics using atmospheric pressure plasma

Reducing fabrication costs is a major driving force in photovoltaic research. Atmospheric processes such as spin coating, spraying or printing are being developed to reduce the cost/Wp of CIGS, CZTS and perovskite solar technologies. For all technologies, surface cleaning and activation prior to thin film deposition is required and for this vacuum based low pressure plasma is a well-established technique. However, a vacuum based surface pre-treatment is not compatible with atmospheric deposition methods. We show that atmospheric-pressure plasmas are highly effective in activating the surface of substrates commonly used in photovoltaic device fabrication and demonstrate its effectiveness on both rigid and flexible substrates. The effectiveness of using atmosphericpressure plasmas to increase surface energy is demonstrated using Water Contact Angle (WCA) measurements and chemical changes are analysed using X-ray Photoelectron Spectroscopy (XPS). Scanning Electron Microscopy (SEM) images show no alteration of the surface morphology of the substrates after the plasma treatment

Народы и культуры Томско-Нарымского Приобья : Материалы к энциклопедии Томской области

DBD plasma microbubble reactor for pre-treatment of lignocellulosic biomass [poster