Dielectric Barrier Discharge Jet Research Articles

Processing laser ablated plasmonic nanoparticle aerosols with nonthermal dielectric barrier discharge jets of argon and helium and plasma induced effects

Dielectric-barrier-discharge (DBD) plasma jets provide viable state-of-the-art nonthermal processes for a wide range of nanomaterials including particle transport and deposition. We report the interaction of argon and helium plasma jets with the particle aerosol, produced by ns laser ablation of a silver target and subsequently their transport for deposition on a distant substrate. The nanofeatures and functionality of the nanoparticles, entrained and deposited with the two plasma jets were compared using high-resolution electron microscopy, helium ion microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, and in terms of the SERS effect. The plasma jet facilitates the transport of the particle aerosol under the upshot of plasma ionic wind, caused by the high electric field in the plasma. Compared to the helium plasma jet, the argon plasma jet leads to a relatively large particle deposition and promotes the formation of aggregates. The helium plasma jet enabled the deposition of spatially well dispersed particles. In both cases, the deposited particle was crystalline and plasmonic active. The plasma-driven altered morphology, expedient particle transport, and formation of agglomerates or spatially well dispersed particles are explained in plasma-induced ionic-wind, and dusty plasma framework. The findings are novel and interesting from the perspective of plasma–surface deposition, surface nanoengineering, and nanomaterial processing for applications in sensing, catalysis, surgical tools, futuristic coating technology, and heat-sensible biological activities.

The Influence of Helium Dielectric Barrier Discharge Jet (DBDjet) Plasma Treatment on Bathocuproine (BCP) in p-i-n-Structure Perovskite Solar Cells.

A bathocuproine (BCP) layer is typically used as the hole-blocking layer in p-i-n-structure perovskite solar cells (PSCs) between PC61BM and Ag electrodes. Before evaporating the Ag, we used a low-temperature (<40 °C) atmospheric-pressure dielectric barrier discharge jet (DBDjet) to treat the BCP with different scan rates. The main purpose of this was to change the contact resistance between the BCP layer and the Ag electrodes through surface modification using a DBDjet. The best power conversion efficiency (PCE) of 13.11% was achieved at a DBDjet scan rate of 2 cm/s. The He DBDjet treatment introduced nitrogen to form C−N bonds and create pits on the BCP layer. This deteriorated the interface between the BCP and the follow-up deposited-Ag top electrode. Compared to the device without the plasma treatment on the BCP layer, the He DBDjet treatment on the BCP layer reduced photocurrent hysteresis but deteriorated the fill factor and the efficiency of the PSCs.

Dielectric barrier discharge jet processed TiO2 nanoparticle layer for flexible perovskite solar cells

For attaining good-performance perovskite solar cells (PSCs), the carrier collection from the perovskite material to the transport layer plays a prominent role; herein, we demonstrate an atmospheric pressure plasma treatment technique to enhance the interface properties between the active perovskite layer and electron transport layer (ETL). A scan-mode low-temperature helium dielectric barrier discharge (DBD) jet is applied to process the TiO2 nanoparticle layers for the flexible n-i-p PSCs made on ITO-coated polyethylene naphthalate substrates. When the surface of TiO2 nanoparticle ETL is treated by the DBD jet at a scan rate of 2 cm s−1 and scan height of 5 cm by ten times, the photoelectrical conversion efficiency of the cell is enhanced from 12.30% to 13.66%. The performance improvement can be attributed to the increase of hydrophilic O–C = O functional groups on the surface of the TiO2 nanoparticle layer and the reduction of charge transfer resistance of the cell revealed by x-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, respectively. The results show that the low-temperature DBD jet treatment is a promising technique for processing flexible photovoltaic devices.

Application of plasma‐activated water as an antimicrobial washing agent of fresh leafy produce

AbstractPlasma‐activated water (PAW) was investigated as a “green” antimicrobial washing agent for decontamination of ready‐to‐eat rocket salads. PAW was generated using a dielectric barrier discharge jet and the plasma chemistry was correlated to the PAW characteristics. The low helium flow rates favored the NOx formation and resulted also in higher reactive species concentration upon storage. PAW activity was retained even after 12 days of storage at low temperatures. The application of fresh and 7‐days‐stored PAW as washing agents resulted in significant microbial load reduction, whereas the quality indices of PAW‐treated rocket leaves were retained. Finally, the PAW treatment increased the shelf‐life of the leafy salad by a factor of ~2.5 upon storage at 5°C, demonstrating the potential application of plasma technology in the processing and shelf‐life extension of sensitive food products.

The role of O3 on the selective formation of nitrate and nitrite in plasma-treated water

This study is to investigate the role of O3 on NO and NO2 oxidations to selective formations of NO2 − and NO3 − in plasma-treated water. Two plasma reactors, a surface dielectric-barrier discharge (DBD) and a coaxial DBD jet, are employed to water treatment with a working gas primarily consisting of N2 and O2. Results of surface DBD show that O3 first is increased with plasma treatment time, reaching a maximum, and then decreased. NO takes time to grow and the grow of NO is accompanied by O3 decrease. Formations of NO2 − and NO3 − are associated with gas-phase nitrogen oxides while the presence of O3 has a critical influence on a selective formation of NO2 − and NO3 −. The strong oxidation of O3 favors the formation of NO3 − while inhibits NO2 − formation. O3 serving as an inhibitor of NO2 − is confirmed with the DBD jet experiment where O3 is admixed in the downstream of the post discharge. O3 enhancement on NO3 − formation is demonstrated by exposing water to a synthetic NO gas with and without O3. In addition to O3, the presence of water vapor in the working gas, presumably facilitating formation of HNO2 and HNO3, greatly promotes NO2 − and NO3 − concentrations in solution. This is thought to be due to the stronger dissolution susceptibility and the relatively larger rate constant of HNO2 and HNO3 than those of N2O3 and N2O5. Finally, based on observations obtained here, a schematic roadmap of selective NO2 − and NO3 − formations is presented.

Therapeutic effect of cold atmospheric plasma and its combination with radiation as a novel approach on inhibiting cervical cancer cell growth (HeLa cells)

Cervical cancer is one of the important cancers in women. Research on novel treatment approach can reduce the mortality and burden. Although radiotherapy is a common treatment, its negative side effects have concerned physician. In our study, we studied impact of cold atmospheric pressure plasma on the Hela cancer cells, as an alternative treatment. The effect of three different types of such plasma; dielectric barrier discharge (DBD), plasma jet, and afterglow plasma, on the cancer cells were studied. Moreover, some effective operating parameters such as exposure time, applied voltage, composition of working gas in plasma treatment were investigated on the survival of the afterglow plasma. Finally, treatments by the afterglow plasma, gamma radiation (1 Gy), and combination of both were compared. Analysis showed that DBD and plasma jet (direct exposure) effectively killed the cancer cells, even by a minimum applied voltage. But a fraction of the cells survived after the exposure of indirect diffused afterglow plasma. In the case of this plasma, we realized that higher applied voltage and exposure time led to less cell viability. Fewer fractions of survival cells were detected in the case of argon afterglow plasma comparing to oxygen afterglow. Cold atmospheric plasma and its combination with radiation therapy showed a significant decrease in viability of the cells, comparing to the radiation alone. Our research showed that plasma and its combination with radiation therapy have superiority over radiation therapy.

Feasibility Study of Dielectric Barrier Discharge Jet-Patterned Perfluorodecyltrichlorosilane-Coated Paper for Biochemical Diagnosis

A helium (He) atmospheric-pressure dielectric barrier discharge jet (DBDjet) is used to pattern 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFDTS)-coated cellulose paper with a shadow mask. DBDjet processing under appropriate conditions can be used to form hydrophilic patterns. The properties of the DBDjet-patterned PFDTS-coated paper are investigated through water contact angle measurement, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), and the results indicate the successful deposition and removal of PFDTS before/after DBDjet treatment. The successful routing and mixing of liquid in the hydrophilic stripes are demonstrated, and a glucose concentration colorimetric test is demonstrated using this DBDjet-patterned PFDTS-coated paper.

Development of an atmospheric nonthermal multineedle dielectric barrier discharge jet for large area treatment of skin diseases

Nonthermal plasma is suitable for applications in the biomedical field because of the large amounts of active species and a low gas temperature that does not injure the human body. A plasma jet of the typical pen type is applied in most biomedical applications, but it is difficult to apply such jets to treat skin diseases that generally have wide affected areas. In this study, nonthermal multineedle dielectric barrier discharge (DBD) jet was developed for the treatment of large area lesions and used to verify its effectiveness in treating psoriasis as a representative skin disease. Stable discharge was maintained using the developed plasma jet with a multineedle electrode structure by utilizing various discharge gases. Electrical and optical analyses were performed to determine the characteristics of the plasma. The effectiveness of psoriasis treatment using this approach was confirmed by performing in vitro and in vivo experiments with the multineedle DBD jet.

Structural modification of NADPH oxidase activator (Noxa 1) by oxidative stress: An experimental and computational study

NADPH oxidases 1 (NOX1) derived reactive oxygen species (ROS) play an important role in the progression of cancer through signaling pathways. Therefore, in this paper, we demonstrate the effect of cold atmospheric plasma (CAP) on the structural changes of Noxa1 SH3 protein, one of the regulatory subunits of NOX1. For this purpose, firstly we purified the Noxa1 SH3 protein and analyzed the structure using X-ray crystallography, and subsequently, we treated the protein with two types of CAP reactors such as pulsed dielectric barrier discharge (DBD) and Soft Jet for different time intervals. The structural deformation of Noxa1 SH3 protein was analyzed by various experimental methods (circular dichroism, fluorescence, and NMR spectroscopy) and by MD simulations. Additionally, we demonstrate the effect of CAP (DBD and Soft Jet) on the viability and expression of NOX1 in A375 cancer cells. Our results are useful to understand the structural modification/oxidation occur in protein due to reactive oxygen and nitrogen (RONS) species generated by CAP.

Inactivation of biofilms in endotracheal tube by cold atmospheric plasma treatment for control and prevention of ventilator‐associated pneumonia

AbstractVentilator‐associated pneumonia (VAP) is a type of hospital‐acquired infection with high mortality and morbidity rates that is seen in critically ill patients who are connected to mechanical ventilators in intensive care units. Conventional infection control measures may remain insufficient for control and prevention of VAP. In the present study, biofilms of most common pathogens, which are responsible for VAP, namely Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, and Candida albicans, were grown in the lumen of endotracheal tubes (ETs) under low shear to mimic the biofilm formation in clinical settings using the drip flow reactor system. Antibiofilm efficacies of two different plasma treatment methods were tested on the biofilms that were grown in ETs. In the first method, deionized water (DIW), phosphate‐buffered saline (PBS) solution, and N‐acetylcysteine (NAC) solution were treated with air dielectric barrier discharge (DBD) plasma and then nebulized on the biofilms. In the second method, air plasma afterglow (APA), which was generated using a DBD jet electrode, was flown through the lumen of ETs. Effects of two different plasma treatment methods on biofilms were evaluated using colony‐counting and XTT assays. The quantity of extracellular polymeric substance (EPS) was evaluated with the safranin assay. Scanning electron microscopy (SEM) was used to visualize the effect of various plasma treatment methods on biofilms. Cytotoxic effects of two different plasma treatment methods were tested on the human tracheal epithelial cell line. Our results suggest that the nebulized plasma‐treated NAC solution had a superior antibiofilm effect as compared with DIW and PBS. Two different plasma treatment methods used effectively inactivated biofilms and significantly reduced the quantity of EPS without a significant damage to the human tracheal epithelial cell line. Furthermore, SEM images showed the inactivation of microbial cells mainly through membrane damage.

Development and Optimization of Single Filament Plasma Jets for Wastewater Decontamination

New efficient depollution techniques for water decontamination, purification and disinfection are being sought to replace those classic methods (chemical, filtration, ozonisation, photochemical reactions) that have deficiency for some substances. The use of plasma technologies, discharges in, or in contact with, wastewater are promising approaches for the decomposition of pollutants by highly oxidative radicals, charged particles, UV radiation, etc. produced by plasma. In the present study we report on the potential of radiofrequency single and multiple filamentary Dielectric Barrier Discharge (DBD) jets for the decolorization of methylene blue (MB) dye in water solutions. Optical emission spectroscopy (OES) investigations were performed for the characterization of plasma evolving in air, and in liquid. The decolorization process was monitored by absorption spectroscopy. We determined the decolorization time, according to a variety of external parameters. The key parameters for obtaining the maximum decolorization rate were identified as being the discharge tube diameter, tube nature (glass/ceramic), the injected power in the discharge, the type of reactive gas and the number of filamentary plasma jets.

Study of large-area atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

<p indent="0mm">In order to obtain a uniform large-area plasma jet at the atmospheric pressure, a new structure of coplanar dielectric barrier discharge (DBD) is proposed in this paper. The structure used in large-area DBD plasma jet consists of two coaxial annular dielectric tubes, and an alternating current electric field is applied by metal film electrodes outside the tubes to form dielectric barrier discharge in the air gap. Based on this configuration, a uniform annular jet is achieved, with diameter of <sc>12 mm</sc> and thickness of <sc>2–3 mm.</sc> The discharge characteristics of the proposed structure and the development process of plasma jet are studied. The spectra of the discharge, the electron temperature, the electron density, and the discharge waveforms are diagnosed. The results show that the physical characteristics of the large-area jet obtained in this work are basically the same as that of the traditional small-diameter DBD jet. It is considered that the physical mechanism of the large-area jet propagation is the mutual coupling propulsion process of a large number of positive corona discharges. The influence of electrode structure and air gap structure on the characteristics of the large-area DBD plasma jet is further studied by experiments, and the optimization principle of the large-area DBD plasma jet is proposed.

Copper film deposition using a helium dielectric barrier discharge jet

AbstractThis study demonstrates that plasma‐enhanced chemical vapor deposition of copper films can be achieved in ambient air and at low temperature. A helium dielectric barrier discharge jet with a small mixture of hydrogen and copper(II) acetylacetonate vapor is utilized as the nonthermal plasma source to deposit conductive copper films with low electrical resistivity (&lt;1 × 10−7 Ω·m). The deposited film appears to have three distinct regions (reddish brown, dark blue, and yellowish) from center to edge. Copper nanograins (~50 nm) are observed in both the reddish‐brown and the dark‐blue regions, whereas the yellowish region exhibits a continuous structure containing copper oxide. The copper films are further deposited on various temperature‐sensitive substrates, including plastic, cardboard, agar, and pork skin.

Plasma‐activated medium as an innovative anticancer strategy: Insight into its cellular and molecular impact on in vitro leukemia cells

AbstractCold atmospheric plasma (CAP) has received attention as a potential anticancer strategy. In this study, culture medium was exposed to a microsecond‐pulsed dielectric barrier discharge jet to produce plasma‐activated medium (PAM). On the T‐lymphoblastic cell line, PAM induced apoptosis through the activation of the intrinsic pathway and inhibited the cell‐cycle progression. The use of the scavengers N‐acetylcysteine or O‐phenantroline significantly decreased the PAM proapoptotic activity. The genetic impact of PAM on TK6 cells was assessed, resulting in an increased micronuclei frequency. PAM exhibited cytotoxic effects even on leukemia cells cultivated in hypoxia, which plays a critical role in promoting chemoresistance. PAM was also tested on normal lymphocytes, showing its partial selectivity. Taken together, these results contribute to understand the pharmacotoxicological profile of CAP.

Low-Temperature (

A scan-mode low-temperature (<40 °C) atmospheric-pressure helium (He) dielectric-barrier discharge jet (DBDjet) is applied to treat nickel oxide (NiO) thin films for p–i–n perovskite solar cells (PSCs). Reactive plasma species help reduce the trap density, improve the transmittance and wettability, and deepen the valence band maximum (VBM) level. A NiO surface with the lower trap density surface of NiO allows better interfacial contact with the MAPbI3 layer and increases the carrier extraction capability. MAPbI3 can better crystallize on a more hydrophilic NiO surface, thereby suppressing charge recombination from the grain boundary and the interface. Further, the deeper VBM allows better band alignment and reduces the probability of nonradiative recombination. NiO treatment using He DBDjet with a scan rate of 0.3 cm/s can improve PSC efficiency from 13.63 to 14.88%.

Ar dielectric barrier discharge jet (DBDjet) plasma treatment of reduced graphene oxide (rGO)–polyaniline (PANI)–chitosan (CS) nanocomposite on carbon cloth for supercapacitor application

A low-temperature (< 42 °C) Ar dielectric barrier discharge jet (DBDjet) is used to treat screen-printed reduced graphene oxide (rGO)–polyaniline (PANI)–chitosan (CS) nanocomposites used as the electrodes of gel-electrolyte supercapacitors. X-ray photoelectron spectroscopy results indicate decreased C–O bonding content, suggesting a reaction with some CS, as well as increased C–N and –COOH contents that could be responsible for the improved hydrophilicity and the resulting enhancement in the capacity of the supercapacitor. Galvanostatic charging discharging measurements indicate that Ar DBDjet treatment improves the capacitance by 166%; these results are confirmed by cyclic voltammetry. Our results demonstrate that without substantial heating, Ar DBDjet reactive plasma species alone can improve the hydrophilicity of rGO–PANI–CS nanocomposites on carbon cloth.

Phase-resolved optical emission spectroscopy of a transient plasma created by a low-pressure dielectric barrier discharge jet

A transient plasma created by a low-pressure dielectric-barrier discharge operated with argon was investigated by means of optical emission spectroscopy and imaging. Images of the discharge and emission spectra were recorded with sub-phase resolution and relative densities of excited argon states were obtained. Profiles of densities and electron temperatures were evaluated for the discharge cycle by comparison with results of a collisional-radiative model (CRM). To overcome difficulties in sub-cycle modelling of the important argon 1s states, a combination of the CRM with a density estimation based on radiation-trapping is proposed. Absolute densities of all four 1s states were measured and additionally verified by tunable laser absorption spectroscopy. The presented combination may help to improve optical diagnostics of rare gas plasmas in cases were the dominating processes for the 1s states are not known with sufficient accuracy.

Non-Thermal Plasma As An Innovative Anticancer Strategy On Leukemia Models

Antitumor chemotherapy is often hampered by the low therapeutic index of most anticancer drugs and the development of chemoresistance. Furthermore, in leukemia incidence and death rates in patients are really close to each other, when compared to other kind of tumors; pointing out that efficacy of anticancer therapy is suboptimal. Thus, there is a continuous need for new intervention strategies, endowed with a better pharmaco-toxicological profile. Cold atmospheric plasma (CAP) has gained interest as a promising anticancer strategy and earlier studies demonstrated the “non-aggressive” nature of CAP [1]. Several lines of evidence showed that the anticancer activity of CAP mainly depends on the increase in oxidative and nitrosative stress that leads to tumor cell death [2]. However, mechanisms of CAP-cell interaction are not yet completely understood. In this context, the aim of this work is to unravel CAP anticancer effects on in vitro and ex vivo leukemia models achieved within the Italian national project “Scientific Independence for young Researchers” (SIR), that brings together a multidisciplinary team in the areas of Engineering, Pharmacology and Oncohematology. The cytotoxic impact of different CAP treatments performed by means of two plasma sources, a nanosecond pulsed dielectric barrier discharge (DBD) [3,4] and a microsecond pulsed DBD jet (Fig.1), on T-lymphoblastic cell lines was investigated. In particular, we analyzed apoptotic and/or necrotic events, cell-cycle progression, levels of proteins involved in the regulation of apoptosis correlated to reactive oxygen and nitrogen species (RONS) induced in culture medium by CAP treatment. Due to the key role of RONS in the biological effects of CAPs, its genotoxic potential was assessed. Furthermore, some preliminary results indicate that CAPs can induce cytotoxic effects also on leukemia cells cultivated in hypoxia, which plays a critical role in promoting chemoresistance. Taken together, the results we obtained contribute to understand the pharmaco-toxicological potential of CAP, thus making the basis to further investigate its anticancer properties. Download : Download high-res image (66KB) Download : Download full-size image Figure 1: Nanosecond pulsed DBD on a grounded plate (right) and microsecond pulsed DBD jet (left).

Plasma actuators for active flow control based on a glow discharge

In this work a glow discharge based active flow control for high flow velocities and low Reynolds numbers is presented. Unlike common plasma actuators such as dielectric barrier discharge (DBD) or spark jets, this actuator uses small impulse bits at frequencies. The actuator is optimized for frequencies up to 40 kHz to counter Tollmien Schlichting wave effects and so reduce overall air foil drag. Several measurements to prove the non-eroding effect of the actuator and the electrical properties were performed. It was found that the actuator is capable of operating at high frequencies without measurable erosion.

A Cold Planar Nitrogen-Based Atmospheric-Pressure Dielectric Barrier Discharge Jet With Enhanced UV Emission and Radical Generation Using Short Electrodes

In this paper, a planar nitrogen-based atmospheric-pressure dielectric barrier discharge (DBD) jet with enhanced UV emission and radical generation, and much lower power consumption and gas temperature using shorter electrodes as compared with a previously developed DBD jet is presented. The highest UV intensity (five times larger) and radical generation (two times larger) in the DBD jet region are found to occur when the electrode length is 1 cm. Corresponding jet gas temperature and power consumption are 31 °C and 39 W, respectively. The 1-cm DBD jet was used to treat polylactide film for enhancing its hydrophilic properties. The results show that a contact angle of 28.4° could be obtained with a residence time of 4 s. The resulting 1-cm DBD jet may provide an efficient surface treatment tool for delicate industrial and biomedical devices/materials.