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Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to inactivate Escherichia coli cells suspended in aqueous solution. Measurements show that the efficiency of inactivation of E. coli cells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2 and He microplasma arrays, air and O2 microplasma arrays may be utilized to more efficiently kill E. coli cells in aqueous solution. The efficiencies of inactivation of E. coli cells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react with E. coli cells in water by direct or indirect interactions., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Uniform and stable reactivity of atmospheric pressure plasmas is a prerequisite for most applications in fields ranging from materials' surface processing, environment protection, to energy conversion. Dielectric barrier discharges (DBDs) are among the most promising plasmas to satisfy these requirements. However, the unpredictable and uncontrollable transitions between discharge modes, the limited understanding of the DBD ignition and extinction processes, and the complexity of plasma chemistries and reactions with admixture gases restrict their adoption in industry. Here, we report a practically relevant and elegant solution based on using customized nanosecond (ns) pulse excitation and precise addition of oxygen to an Ar flow. The effects of ns pulses and oxygen on the uniformity and reactivity of the DBD are investigated via quantifying the gap voltage Ug and the discharge current Ig from the current–voltage measurements and quantitative discharge imaging. The electron density, ne, is estimated with Ug and Ig. With increasing Ug, more electron avalanches are ignited and overlap, which facilitate ne, Te, and discharge uniformity, while high Ug induces excessive electrons generated with high ionization rates, resulting in the distortion of the space electric field and reduced stability and uniformity. A small amount of added oxygen favors the production of electrons. Overdosed oxygen molecules capture electrons causing a drop in ne and Te and couple with the effect of the electrical field resulting in the filamentary discharges or complete plasma extinction. The mechanism of the effects of ns pulses and oxygen addition on the uniformity and reactivity of plasmas is based on the electrical measurements and discharge image analysis and is cross-validated by optical emission spectra measurements and the ratio of the Ar intensities' calculations as indicators of the variation in ne and Te. The results in this work contribute to the realization and controllability of uniform, stable, and reactive plasmas at atmospheric pressure. [ABSTRACT FROM AUTHOR]

A correction to the article "Synergistic Effect of Atmospheric-Pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media" in the Scientific Reports (December 22, 2016) is presented, which discusses errors in Figure 3 due to repeated bacterial colony images.

Peroxynitrite is an important chemical in the human immune system, which has high biocidal activity and can resist the invasion of pathogens. Currently, in vitro generation of peroxynitrite faces major technological challenges, especially for gas‐phase production, which requires low‐pressure conditions. Here, we report the method of how to generate gas‐phase peroxynitrite at atmospheric pressure using dielectric barrier discharge. Results show that the peroxynitrite concentration positively correlates with energy density. Moreover, Penicillium digitatum, a common fungus contaminant greatly affecting food and fruit preservation, was used as a microbial pathogen model to confirm the biocidal effects of ozone‐free nitrogen oxides under different discharge conditions. The germination inhibition efficiency of P. digitatum is highly likely attributed to the synergistic effect of gaseous peroxynitrite and NO. [ABSTRACT FROM AUTHOR]

Homogeneous penetration of atmospheric pressure uniform air plasma (APUAP) into thin gaps is highly warranted for multipurpose processing of materials. Here, we report APUAP generation in a 7 mm discharge gap with ambient air as the working gas, well beyond the presently maximum achievable 4 mm. Driven by a short pulse high voltage power, a 7 mm wide and 60 mm long uniform air plasma sheet is generated. The discharge is robust and the uniformity is not affected by the complex and variable components of ambient air, as is the case for most plasma discharges in air. Ultrafast photography shows that, different from previous reports, the discharge initiates in the whole air gap simultaneously and brightens quickly with the fast rise of the pulsed voltage. The generation of uniform plasma is mainly attributed to the high density of seed electrons and the reduced number density of molecules in air. Moreover, the achievable gas temperature of up to 1300 K indicates that this type of plasma is suitable for processing of a broad range of materials. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency. [ABSTRACT FROM AUTHOR]

Plasma medicine is a relatively new field that investigates potential applications of cold atmospheric-pressure plasmas in bioengineering, such as for bacterial inactivation and degradation of organic molecules in water. In order to enunciate mechanisms of bacterial inactivation at molecular or atomic levels, we investigated the interaction of atmospheric-pressure air microplasmas with amino acids in aqueous solution by using high-resolution mass spectrometry (HRMS). Results show that the oxidation effect of plasma-induced species on the side chains of the amino acids can be categorized into four types, namely hydroxylation, nitration, dehydrogenation and dimerization. In addition, relative activities of amino acids resulting from plasma treatment come in descending order as follows: sulfur-containing carbon-chain amino acids > aromatic amino acids > five-membered ring amino acids > basic carbon-chain amino acids. Since amino acids are building blocks of proteins vital to the growth and reproduction of bacteria, these results provide an insight into the mechanism of bacterial inactivation by plasma. [ABSTRACT FROM AUTHOR]

In this study, the effect of atmospheric-pressure air surface dielectric barrier discharge (SDBD) on the degradation of Omethoate smeared edible wolfberry was investigated by gas chromatography and mass spectrometry (GC-MS). The degradation efficiency of SDBD on Omethoate is shown to be strongly dependent on the discharge voltage and plasma treatment time. The plasma-induced degradation mechanisms were studied through identification of the intermediates or by-products generated during SDBD plasma treatment. The results show that the degradation efficiency may be higher than 99% under the optimum discharge conditions, i.e., at the applied voltage of 10 kV and the treatment time of 30 min. It is concluded that the atmospheric-pressure SDBD plasma may degrade pesticide residue into nontoxic species (such as PO43−, H2O, SO42−, and CO2) during the plasma treating process. [ABSTRACT FROM AUTHOR]

A self-made microplasma jet array device is used to treat deoxyadenosine (dA) and adenosine (Ado) solutions to avoid the effect of air on genetic materials. Results show that Ado is easily converted into dA through deoxidation reaction. In addition, dA solution is treated with different microplasma arrays (i.e., atmospheric-pressure Ar, N2, air, and O2­) for comparative analysis. The dA molecule is relatively stable within the Ar plasma for 3 min treatment time. This molecule can be modified into different structures with N2, air, and O2 microplasma arrays. The results obtained in this study provide references for the application of plasma in biology and the effect of oxygen-containing free radicals in biological plasma. [ABSTRACT FROM AUTHOR]

A large-area diffuse surface dielectric barrier discharge (SDBD) produced using ambient air at atmospheric pressure is investigated with respect to its electrical and optical characteristics. Current–voltage measurements and intensified charge coupled device images show that the multiple-groove SDBD device is able to generate a kind of visible large-area diffuse discharge at the applied voltage more than 22 kV with the repetition frequency of 9 kHz, which is associated with the accumulation of electric charges. Moreover, the multiple-groove SDBD is also found to be very efficient in the inactivation of Escherichia coli and Candida albicans on the surface of chopsticks. It is found that the electrostatic tensile generated by accumulated charges may play a key role on the cell inactivation. [ABSTRACT FROM PUBLISHER]

Plant diseases resulting from plant pathogens are profoundly affecting crops worldwide. In this study, the tomato pathogen Cladosporium fulvum ( C. fulvum) have been inactivated by using the atmospheric-pressure plasma jet (APPJ). The results show that the inactivation efficiencies of C. fulvum are dependent on the plasma density and treatment time. The APPJ with a relatively high plasma density can completely kill the resistant C. fulvum within the treatment time of 60 s. Due to plasma generating electrostatic force, the outer membrane of C. fulvum is disrupted and the cytoplasm is released to the surrounding medium. Both protein and DNA molecules can be destroyed during the plasma inactivation. Meanwhile, the APPJ can also provide a novel approach to decrease the rotting rates of C. fulvum-infected tomato seeds. [ABSTRACT FROM AUTHOR]

• CO 2 reforming of CH 4 was performed in DBDs with different dielectric layers. • More intensified filamentary microdischarges were displayed in DBD-SD. • DBD-SD exhibited higher reactant conversion and liquid product selectivity. • Higher gas product selectivity and stable carbon balance were achieved in DBD-DD. • Higher energy efficiency for plasma reforming process was obtained in DBD-SD. CO 2 reforming of CH 4 in a non-thermal plasma process (e.g., dielectric barrier discharge, DBD) possesses dual benefits for our environment and energy needs. However, this process is strongly influenced by the dielectric structure of the DBD. Here, plasma CO 2 reforming of CH 4 has been performed in both single-dielectric and double-dielectric DBD (DBD-SD and DBD-DD) reactors under atmospheric pressure. Electrical and optical characterization, along with temperature measurements are performed to understand the influence of the DBD-SD and DBD-DD designs. Reactor performance for reforming is compared under different discharge powers. The results show that CO 2 /CH 4 discharges in both DBD-SD and DBD-DD display typical filamentary microdischarges. Compared with the DBD-DD, the DBD-SD reactor exhibits a larger number and higher intensity of current pulses, which leads to a higher electron density and formation of reactive species. The highest conversion of CO 2 (24.1 %) and CH 4 (49.2 %) are achieved in the DBD-SD at a high discharge power (75 W). Moreover, higher selectivities of gaseous products are obtained in the DBD-DD, while the DBD-SD reactor shows a higher selectivity for liquid products, mainly including methanol and acetic acid. The highest energy efficiencies for reactant conversion (0.34 mmol/kJ), gaseous and liquid production formation (0.26 mmol/kJ and 0.015 mmol/kJ) are achieved in the DBD-SD reactor at a low discharge power (22 W), resulting from the low energy loss to the environment. However, the carbon deposited on the inner electrode surface in the DBD-SD would have an adverse influence on the reactor's performance. Further research on the optimization of the DBD reactor to establish an efficient plasma-catalysis system is required for industrial applications. [ABSTRACT FROM AUTHOR]

Silver nanoparticles have applications in plasmonics, medicine, catalysis and electronics. We report a simple, cost-effective, facile and reproducible technique to synthesise silver nanoparticles via plasma-induced non-equilibrium liquid chemistry with the absence of a chemical reducing agent. Silver nanoparticles with tuneable sizes from 5.4 to 17.8 nm are synthesised and characterised using Transmission Electron Microscopy (TEM) and other analytic techniques. A mechanism for silver nanoparticle formation is also proposed. The antibacterial activity of the silver nanoparticles was investigated with gram-positive and gram-negative bacteria. The inhibition of both bacteria types was observed. This is a promising alternative method for the instant synthesis of silver nanoparticles, instead of the conventional chemical reduction route, for numerous applications. [ABSTRACT FROM AUTHOR]

• Cold plasma was used to modify photoanodes of the SnO 2 based DSSCs. • Plasma removes hydrocarbonated and oxocarbonated species from photoanode surfaces. • N 2 plasma converts Sn into higher oxidation states and reduces oxygen vacancies. • Remarkable efficiency increasement of ~410% was achieved. Dye sensitized solar cells (DSSC) are an attractive third-generation photovoltaic technology particularly promising for operation under diffuse and lower light conditions. However, high costs of the precious metals used for sensitizing dyes and low charge generation capability parameters limit the utility of DSSCs in comparison to conventional silicon solar cells. In this study, tin oxide (SnO 2) photoelectrodes are treated with non-thermal atmospheric pressure plasmas to enhance photovoltaic performance. The effects of nitrogen and argon plasma surface treatment of photoanodes on the efficiency enhancement of DSSCs are systematically investigated by fabricating solar cells using pristine SnO 2 and plasma-treated photoanodes. Solar cells made with Eosin Y sensitized pristine SnO 2 photoanode exhibited a short circuit current density (J SC) of 1.03 mA cm−2 and an overall power conversion efficiency (PCE) of 0.30% whereas solar cells made with nitrogen plasma treated photoanode exhibited a J SC of 6.20 mA cm−2 and an overall PCE of 1.53% (4 times enhancement) under the same illumination of 100 mW cm−2 (AM 1.5). The efficiency of the solar cells fabricated with Ar plasma treated SnO 2 photoanodes also showed an enhanced power conversion efficiency. Further characterizations revealed that the surface plasma treatments increased the surface roughness of the photoanodes. Plasma treatment led to the incorporation of nitrogen species and removal of surface impurities resulting in an increase in dye adsorption in the photoanode and hence the enhancement in the efficiency of the DSSC. This study demonstrated a one-pot treatment method for efficiency enhancement which could be used in various applications such as photovoltaic, catalytic and energy generation applications including DSSCs, thin-film solar cells, perovskite solar cells, gas sensing, bio-sensing, supercapacitors, Li-ion batteries and others. [ABSTRACT FROM AUTHOR]