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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]

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]

• 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]

We present a helium porous plasma jet based on gas diffuser, designed with the aim of decontaminating inner surfaces of contaminated structures, e.g., pipes. The porous plasma jet operates with three discharge modes in ambient air and inside a vessel. Its decontamination capacity is demonstrated by evaluating the inactivation efficacy of biofilm form of Pseudomonas aeruginosa, adherent to inner surface of a glass vial. Plasma treatments for 5 min with filament mode and double region helium discharge mode reduced bacterial numbers by 2.4 and 2.5 Log10 CFU/ml. Plasma treatment with double region air‐like discharge mode was the most effective, reducing bacterial cells by 4.5 Log10 CFU/ml, which demonstrates porous plasma jet could provide an efficient approach for inner surface decontamination. A helium porous plasma jet has been presented. With the proper discharge mode, it significantly inactivates Pseudomonas aeruginosa biofilm adherent to the inner surface of a glass vial by greater than 4 Log10 CFU/ml. The porous plasma jet presented can provide an efficient alternative for the inner surface sterilization in relevant sectors, such as medical device, food and pharmacy industries. [ABSTRACT FROM AUTHOR]

Cold atmospheric plasma offers significant potential as a nonthermal decontamination tool for food and medical applications. We present results of a dielectric barrier discharge (DBD) plasma induced in a gas confined by a polymer package. The resultant discharge and contained afterglow are found to have a strong antimicrobial effect. [ABSTRACT FROM PUBLISHER]

Atmospheric pressure plasma systems are routinely used to treat the surfaces of thermally sensitive materials. There are wide ranges of commercial plasma jet systems available, and for the end user, it can be difficult to directly compare the power outputs of these sources. This paper evaluates the use of a thermal imaging technique in order to provide a semiquantitative evaluation of energy output from plasma jets. The evaluation involved a comparison of the thermal energy transfer obtained from three commercially available atmospheric pressure plasma jet systems: 1) PlasmaTreat’s Openair; 2) Dow Corning’s PlasmaStream; and 3) SurFx’s Atomflo. [ABSTRACT FROM PUBLISHER]

• 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]

Abstract The effect of two novel technologies, also in combination, on germination and growth of soybeans has been investigated. On one side, ultrasound treatment of the seeds increased water uptake without altering the morphology and the wettability of the seed coat, but also induced slight chemical modifications of the outer part of the seed. Plasma-activated water (PAW), obtained from treating water with non-thermal atmospheric-pressure plasma in air, increased the rate of germination and subsequent plant growth. Different combinations of these two technologies were tested in order to study their interaction and to identify an optimum treatment process. Industrial relevance A great urgency in crop management is to enhance sustainability. The aim is to achieve a cheap and eco-friendly production process reducing the wide current use of energy, irrigation water, chemicals and pesticides. Soybeans is a legume whose worldwide production is increasing in the last years therefore a higher efficiency and sustainability in its cultivation is obviously very appealing. Cold plasma and Ultrasound technologies are well-known in the industrial scenario and their applications in crop production are recently drawing attention; the potential of combining these two powerful techniques is clearly very promising. Highlights • PAW has increasing concentration of NO 3 −, NO 2 −, H 2 O 2 and acidity with treatment time. • US induces changes on surface chemistry and water permeability. • US and PAW, alone or synergistically, increase the germination rate. • PAW treated for 1 min results in faster growth of plants in soil both on NTS or US. [ABSTRACT FROM AUTHOR]

Cold plasma is increasingly under research for decontamination of foods, especially fresh fruits and vegetables. The effect of cold plasma on food quality, however, remains under researched. This study investigates the effects of cold plasma generated within a sealed package from a dielectric barrier discharge on the physical quality parameters and respiration rates of cherry tomatoes. Respiration rates and weight loss were monitored continuously, while other parameters are reported at the end of storage period. Differences among weight loss, pH and firmness for control and treated cherry tomatoes were insignificant towards the end of storage life. Changes in respiration rates and colour of tomatoes were recorded as a function of treatment, which were not drastic. The results implicate that cold plasma could be employed as a means for decontamination of cherry tomatoes while retaining product quality. [ABSTRACT FROM AUTHOR]