Non-thermal Atmospheric Pressure Plasma Jet Research Articles

A comparative study of gas temperature determination in non-thermal atmospheric pressure plasma jet by spectral analysis and scattering technique for plasma-catalyst measurements

Comparison and validation of different methods for the measurements of plasma gas temperature were studied. The investigations depend on optical emission spectroscopy OES, laser scattering technique, and line-broadening mechanisms. The rotational temperature of the second positive system SPS (C3 ∏+ u - B3 ∏+ g) around 380 nm, second positive system SPS at 337.1 nm of nitrogen molecule (C3 ∏+ u - B3 ∏+ g), and first negative system FNS at 391.4 nm of nitrogen ion (B2Σu +→X2Σg +) were investigated. Moreover, Raman scattering spectra at 532 nm were used to measure the gas temperature in the plasma jet. Gas temperature from the emission line broadening method was also calculated. The role of non-thermal plasma in assisting NOx reduction over an Ag/Al2O3 catalyst at low temperatures using simulated diesel fuels (toluene) was confirmed. Importantly, a significant activity of both NOx and hydrocarbons oxidation was observed and obtained at low gas temperatures. It was found that there is a clear correlation between the gas temperature and the conversion efficiency of the catalyst under different operating conditions of the plasma reactor. The main objective of this investigation was to confirm the important role of the non-thermal plasma in catalyst activation at low gas temperatures compared to traditional thermal activation.

Influence of pre-treatment with non-thermal atmospheric pressure plasma on bond strength of TP340 titanium-PEEK direct bonding

Direct bonding of a TP340 titanium to PEEK by hot pressing via pre-treatment of non-thermal atmospheric pressure plasma jet has been demonstrated. The plasma irradiation effect on the bonding surface on the bond strength after hot pressing was investigated. The tensile shear strength of TP340-PEEK joined by hot pressing after plasma pre-treatment was measured by comparing specimens bonded using conventional hot pressing and those bonded using adhesives. The plasma treatment to the TP340 side resulted in the formation of TiO2, which is chemically fed to oxide formation due to the irradiation of oxygen radicals generated by the plasma, resulting in a bond strength of less than 1 MPa, similar to the bond strength of the untreated specimens. The plasma irradiation effect on the PEEK side on the bond strength of TP340-PEEK bonded samples was also investigated. The bonding strength was increased by plasma irradiation to PEEK. As the plasma irradiation time was increased, the bonding strength gradually increased to 9.2 MPa, which is about 19 times higher than the bonding strength without plasma irradiation. These results suggest that oxygen radicals in the atmospheric pressure RF plasma jet produced oxygen-containing surface functional groups on the PEEK surface, which increased the strength of the TP340-PEEK direct joining.

Influence of pre-treatment using non-thermal atmospheric pressure plasma jet on aluminum alloy A1050 to PEEK direct joining with hot-pressing process

Abstract Aluminum alloy A1050 to polyetheretherketone (PEEK) direct joining with hot-pressing process via pre-treatment using non-thermal atmospheric pressure plasma jet has been performed. The effect of plasma irradiation on the tensile shear strength of A1050-PEEK direct bonded specimens joined by a combination of hot-pressing process and pre-plasma treatment using non-thermal atmospheric pressure plasma jet was investigated. A1050-PEEK bonded samples with plasma-treated PEEK only showed high tensile shear stress of 13.4 MPa. This increase in tensile shear strength is attributed to the addition of oxygen functional groups on the surface of the PEEK by reactive oxygen species produced by the plasma jet.

Influence of Nonthermal Plasma Jet on the Surface Properties of Wheat Seeds

The change in the surface properties of wheat seeds under the influence of a nonthermal atmospheric-pressure plasma jet is shown. After plasma treatment, the surface of wheat seeds becomes hydrophilic and is characterized by a decrease in the contact angle, an increase in surface energy, and an increase in seed water uptake.

Nonthermal atmospheric pressure plasma jet-assisted formation of oxygen vacancies stabilized tetragonal zirconia particles

This study presented a controlled oxygen vacancy formation on stabilization of tetragonal zirconia particles via a nonthermal atmospheric pressure plasma jet (APPJ) with varying the supplied power. The characteristic analyses based on X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy (HR-TEM), Raman, ultraviolet–visible spectroscopy, and ultraviolet photoemission spectroscopy confirm the existence of oxygen vacancies in tetragonal zirconia particles. Production of oxygen vacancies in the prepared zirconia powder is related to the presence of surface defects by observing HR-TEM and further decreases the bandgap as indicated by optical characterization. Thus, it can be anticipated that the research of defect engineering is a promising way to improve the optoelectronic and photocatalytic performance of oxide material via the APPJ method.

Application of Non-thermal Plasma-Activated Liquid for Delay Browning in an Apple Slice

The color of fresh-cut fruits is indicated by the appearance and quality of their products. A sliced apple is a highly putrefying fruit that is sensible to react with oxygen gas, which causes the color, taste, smell, and nutritional value to change during storage in ambient air. Non-thermal atmospheric pressure plasma jet (NTAPPJ) is one of the most crucial applications for food preservation. This study was divided into two parts. First, the emission intensities of the plasma spectrum and electrical properties were investigated. Then, the colorimetric was used to investigate plasma-treated effects on different liquids (tap water, deionized water, and saline water) to delay color changes of fresh-cut apples. The I-V characteristic curve was used to obtain an optimal power of 8.5 kHz-AC pulse-driven NTAPPJ with argon gas. Additionally, the parameter a*, L*, b*, ΔE, h*, YI, Chroma, and browning index (BI) using the colorimeter method were examined. We then demonstrated that using the Ar-NTAPPJ can be considered a novel approach to increasing fresh-cut apple’ toleration and shelf life. Furthermore, plasma exposure is one of the nondestructive processes that does not have any side effects on the products and can significantly delay degradation and discoloration. Keywords: Plasma jet, Shelf life, Colorimeter, Browning index

Spectroscopic investigation of atmospheric pressure cold plasma jet produced in dielectric barrier discharge

Non-thermal cold atmospheric pressure plasma jet (APPJ) produced in multi-pulse dielectric barrier discharge (DBD) preferentially heats the electrons that subsequently transfer their energy to the other plasma species converting them into reactive species. Therefore the characterization of different energy groups of electrons is essential for efficient production and control of reactive plasma species contributing to surface modifications. Here we present the spectroscopic investigations of the APPJ produced in multi-pulse DBD using pin electrode configuration. Boltzmann plot relates the emission intensities of the several Ar–I spectral lines to their corresponding threshold excitation energies to give the electron temperature more precisely. The Stark broadening of the Ar–I (696.54 nm) line profile gives the electron number density after de-convoluting the contributions of the Doppler and instrumental broadenings. Plasma measurements correlate the gas flow rate, applied jet power across the electrodes, and a group of electrons contributing to optical emission. Sequential imaging correlates the size of the plasma bullets momentarily with the discharge pulse for different argon flow rates and applied jet powers. With an increasing flow rate of up to 1.4 L/min, the plasma plume of the jet becomes more elongated, intense, and spatially uniform. However, the glow intensity and size of the plume start reducing with a further increase in gas flow rate. Experimental findings propose plasma processing for small-scale localized plasma surface treatments.

On different modes of a filamentary atmospheric pressure plasma jet: modeling, laser schlieren deflectometric and high-speed camera investigations

We investigated a filamentary non-thermal atmospheric pressure plasma jet used for coating applications. The plasma jet exhibits two different modes, the stationary mode and the locked mode, in which the filaments rotate around the plasma jet axis. We present a model for the modes and verify it by measurements with high-speed camera and laser schlieren deflectometry. Laser schlieren deflectometry investigations reveal a drift of the rotation frequency over time towards lower values. Additionally, relations between the filament rotation frequency and gas flow as well as input power, respectively, are investigated by the laser schlieren deflectometry. Correlation between rotation frequency and gas flow show a linear dependence and with increasing power the rotation frequency increases as well. All the results are in agreement with the proposed model.Graphical abstract

Flexible Cold Atmospheric Plasma Jet Sources

The properties of non-thermal atmospheric pressure plasma jets (APPJs) make them suitable for industrial and biomedical applications. They show many advantages when it comes to local and precise surface treatments, and there is interest in upgrading their performance for irradiation on large areas and uneven surfaces. The generation of charged species (electrons and ions) and reactive species (radicals), together with emitted UV photons, enables a rich plasma chemistry that should be uniform on arbitrary sample profiles. Lateral gradients in plasma parameters from multi-jets should, therefore, be minimized and addressed by means of plasma monitoring techniques, such as electrical diagnostics and optical emission spectroscopy analysis (OES). This article briefly reviews the main strategies adopted to build morphing APPJ arrays and ultra-flexible and long tubes to project cold plasma jets. Basic aspects, such as inter-jet interactions and nozzle shape, have also been discussed, as well as potential applications in the fields of polymer processing and plasma medicine.

Enhanced adsorption removal of As(III) using MnOFe2O3 with the non-thermal atmospheric pressure plasma jet via the catalytic redox-adsorptive phenomenon

In this study, redox adsorption of the heavy metal, As(III), was potentially removed using non–thermal plasma discharge by enhanced redox adsorption process in contaminated water as per the WHO level. The generated reactive species of O, OH•, and H2O2 produced by plasma interaction with water molecules at air ambient conditions were used to transform As(III) (H3AsO3) to As(V) (HAsO42−) and surface modification of adsorbent, MnOFe2O3 (Mn2+, Mn3+, Fe2+, and Fe3+). The maximum amount of reactive species, H2O2 was found to be 31.71 μM in the water. Also the catalyzing adsorption ability of adsorbent was enhanced by 30 % via the redox-adsorptive mechanism, when compared without plasma. Further, the batch kinetics of pseudo first order (PFO) model was shown to be well predicted for adsorption capacity qe (mg/g), in comparison with pseudo second order (PSO) under various As(III) concentrations. Also the maximum adsorption capacity qe was achieved by the isotherms studies based on the Langmuir model. The adsorption yield for As(III) to As(V) on the MnOFe2O3 were estimated with surface analysis of MnOFe2O3 by XRD, SEM, EDX, XPS, FTIR, and BET.

Surface Characterization, Antimicrobial Activity of Nonthermal Atmospheric-Pressure Plasma Jet on Polyvinyl Siloxane Impression Materials.

Background and Objectives The antimicrobial efficacy of a nonthermal atmospheric-pressure plasma jet (NAPPJ) on dental impression materials was investigated. Materials and Methods Type 3 polyvinyl siloxane was used as the impression material, and air and nitrogen NAPPJ were applied. The antibacterial effect of the NAPPJ was measured using the number of colony-forming units (CFUs) and scanning electron microscopy (SEM) images of Streptococcus mutans. Surface chemical characteristics of the impression material were examined using X-ray photoelectron spectroscopy (XPS) and contact angle measurement. Additionally, physical properties were analyzed through surface roughness measurement, detail reproduction, and strain-in-compression test. Results Compared with the control group, the plasma treatment group showed ruptured bacteria membranes, destroyed bacteria structures, a significant reduction in the number of CFUs, and a significantly reduced contact angle. Further, XPS analysis showed that their surface was significantly richer in hydroxyl groups. The surface roughness, detail reproduction, and strain-in-compression results indicated no significant differences between the plasma treatment and control groups. NAPPJ treatment could remove bacteria from polyvinyl siloxane dental impression materials without changing the surface's physical properties. Conclusion Therefore, it is considered a promising method for disinfection.

Wound healing in db/db mice with type 2 diabetes using non-contact exposure with an argon non-thermal atmospheric pressure plasma jet device.

A non-thermal atmospheric pressure plasma jet (APPJ) may stimulate cells and tissues or result in cell death depending on the intensity of plasma at the target; therefore, we herein investigated the effects of non-thermal plasma under non-contact conditions on the healing of full-thickness wounds in diabetic mice (DM+ group) and normal mice (DM- group). A hydrogen peroxide colorimetric method and high performance liquid chromatography showed that APPJ produced low amounts of reactive oxygen and nitrogen species. Ten-week-old male C57BL/6j mice with normal blood glucose levels (DM- group) and 10-week-old male C57BLKS/J Iar-+Leprdb/+Leprdb mice (DM+ group) received two full-thickness cutaneous wounds (4 mm in diameter) on both sides of the dorsum. Wounds were treated with or without the plasma jet or argon gas for 1 minute and were then covered with a hydrocolloid dressing (Hydrocolloid), according to which mice were divided into the following groups: DM+Plasma, DM+Argon, DM+Hydrocolloid, DM-Plasma, DM-Argon, and DM-Hydrocolloid. Exudate weights, wound areas, and wound area ratios were recorded every day. Hematoxylin and eosin staining was performed to assess re-epithelialization and α-SMA immunohistological staining to evaluate the formation of new blood vessels. Non-thermal plasma under non-contact conditions reduced the production of exudate. Exudate weights were smaller in the DM+Plasma group than in the DM+Hydrocolloid and DM+Argon groups. The wound area ratio was smaller for plasma-treated wounds, and was also smaller in the DM+Plasma group than in the DM+Hydrocolloid and DM+Argon groups on days 1–21 (p<0.01). Wound areas were smaller in the DM-Plasma group than in the DM-Argon group until day 14 and differences were significant on days 1–5 (p<0.01). The percentage of re-epithelialization was significantly higher in the DM+Plasma group than in the DM+Argon and DM+Hydrocolloid groups (p<0.01). The number of new blood vessels that had formed by day 7 was significantly higher in the DM+Plasma group than in the DM+Hydrocolloid and DM+Argon groups (p<0.05). These results indicate that treatment with the current non-thermal plasma APPJ device under non-contact conditions accelerated wound healing in diabetic mice.

Direct-Contact and Contact-free Treatment of a DBD-like Non-thermal Atmospheric Pressure Plasma Jet on Pseudomonas aeruginosa

In this study, a Dielectric Barrier Discharge (DBD)-like non-thermal atmospheric pressure plasma jet (NTAPPJ) was exposed to the Pseudomonas aeruginosa planktonic bacteria. The P. aeruginosa bacteria were treated by the NTAPPJs in both Ar and He at the non-contact distance (contact-free) and the contact distance (direct-contact). The contact of the NTAPPJs with the bacteria has generated spark discharges in both filamentary mode and diffuse mode. The antibacterial efficacy of the Ar and He NTAPPJs for various treatment times (60, 120, 180, and 300 sec) were investigated by treatment on the bacteria without contact and with contact in both filamentary mode and diffuse mode. The NTAPPJs in both Ar and He caused erosion on the agar surface when treated in direct-contact with the bacteria in the filamentary mode, while the NTAPPJs in Ar in the diffuse mode produced the greatest antibacterial efficacy without damage.

Effect of plasma-activated water on microbial quality and physicochemical properties of fresh beef

Abstract This work studies the influence of plasma-activated water (PAW) on the decontamination of beef and its influence on the color, pH, the thiobarbituric acid reactive substance values (TBARS), and total volatile basic nitrogen (TVBN) values of meat. PAW was generated using non-thermal atmospheric pressure plasma jet (NTAPPJ). He + 0.2% N2 and He + 0.2% O2 were used as worker gas to generate PAW. The PAW produced by the He + O2 plasma system exhibited a higher potential for decontamination of beef than that produced by the He + N2 plasma system. The lightness value (L*) of treated beef does not exhibit a noticeable difference with the control one. TBARS values of all treated beef were lower than the rancidity threshold but significantly greater than that of control samples. The TVBN value of control beef samples reached the decay threshold after 18 days of stockpiling, but treated beef remained good. This work reveals that PAW can potentially inhibit the growth of microorganisms in beef.

An Ionization-Driven Air Plasma Jet

Non-thermal atmospheric pressure plasma jets (NAPPJs) using ambient air as the inducer are of particular and desirable interest but with significant challenges. In this study, we report an air APPJ driven by ionization in the afterglow region, resembling noble gas APPJs. A pin-to-nozzle electrode is used for the air plasma jet with a nanosecond-pulsed DC high voltage as the power supply. Results show that the nozzle diameter plays an essential role in forming the air plasma jet. When the nozzle diameter is 3 mm, the air APPJ is driven by ionization in the afterglow region which is proved by the following three phenomena. First, with an exposure time of 0.1 s, an obvious shiny line (the narrow channel plasma) formed by electron accumulation is observed in the jet. The narrow channel becomes much brighter with a grounding pin approaching the nozzle vertically. In comparison, there is no such phenomenon with a 1-mm diameter nozzle. Second, the afterglow region discharge current of the ionization-driven processes is hundreds of mA distinguished from airflow-driven processes, the afterglow region current of which is typically zero. By using E-FISH to measure the electric field in the afterglow region, it can detect the electric field which has a maximum value of 10.5 kV/cm. Third, the intensity of the N2+ band is much stronger with a 3-mm diameter nozzle than with a 1-mm diameter nozzle, indicating that the local electric field plays an important role in the discharge. We expect this study can offer useful guidelines on the design and understanding of ionization-driven air plasma jets.

Plasma Promotes Fungal Cellulase Production by Regulating the Levels of Intracellular NO and Ca2.

For the industrial-scale production of useful enzymes by microorganisms, technological development is required for overcoming a technical bottleneck represented by poor efficiency in the induction of enzyme gene expression and secretion. In this study, we evaluated the potential of a non-thermal atmospheric pressure plasma jet to improve the production efficiency of cellulolytic enzymes in Neurospora crassa, a filamentous fungus. The total activity of cellulolytic enzymes and protein concentration were significantly increased (1.1~1.2 times) in media containing Avicel 24–72 h after 2 and 5 min of plasma treatment. The mRNA levels of four cellulolytic enzymes in fungal hyphae grown in media with Avicel were significantly increased (1.3~17 times) 2–4 h after a 5 min of plasma treatment. The levels of intracellular NO and Ca2+ were increased in plasma-treated fungal hyphae grown in Avicel media after 48 h, and the removal of intracellular NO decreased the activity of cellulolytic enzymes in media and the level of vesicles in fungal hyphae. Our data suggest that plasma treatment can promote the transcription and secretion of cellulolytic enzymes into the culture media in the presence of Avicel (induction condition) by enhancing the intracellular level of NO and Ca2+.

Evaluation of the Effects of a Nonthermal Atmospheric Pressure Plasma Jet on the Prevention of Enamel Demineralization during Fixed Bracket Treatment

Evaluation of the Effects of a Nonthermal Atmospheric Pressure Plasma Jet on the Prevention of Enamel Demineralization during Fixed Bracket Treatment

Influence of radiation transport on discharge characteristics of an atmospheric pressure plasma jet in argon

In the current work the method of radiation trapping treatment in finite coaxial cylinders using spherical coordinates is introduced. The operator of the resonant transition process is obtained explicitly in matrix form and its response to the delta function is analyzed in both hollow and solid cylinders. The influence of the radiation trapping effect is shown for the example of a model of a miniaturized non-thermal atmospheric pressure plasma jet. The results of the calculations with the developed matrix method (MM) are compared with those based on the effective probability approximation. It is shown that the use of the MM leads to significant spatial redistribution of the excited plasma species due to the non-local effects of the radiation transport mechanism.

Investigation of a non-thermal atmospheric pressure plasma jet in contact with liquids using fast imaging

An experimental diagnostic based on a nanosecond-intensified charged coupled device camera and optical emission spectroscopy (OES) are proposed to observe the interfacial region between the plasma plume and liquid surfaces. The study is simulating the investigations of using non thermal atmospheric pressure plasma jets for the eradication of bacterial biofilms. The spatially and temporally resolved images are focused on the contact region in the open air between the nozzle of the reactor and liquid targets. The emission intensity from one discharge cycle is captured and accumulated over several cycles to investigate the formation and the kinetic evolution of the plasma during the interaction. Moreover, the emission intensity of the helium plasma jet and plasma behaviour with different samples are observed. It is found that some dynamic of the plasma discharge has changed during the interaction with different targets. The method can be used to improve the need of understanding of the physics and chemistry of plasma jet during the interaction with liquid surfaces. Different types of species that arrived to the samples were studied and compared with the free jet mode using OES.

Effects of Pre-Treatment Using Plasma on the Antibacterial Activity of Mushroom Surfaces.

Although non-thermal atmospheric pressure plasma is an efficient tool for preventing post-harvest microbial contamination, many studies have focused on the post-treatment of infected or contaminated foods. In this study, we examined the antimicrobial quality of mushrooms pre-treated with a non-thermal atmospheric pressure plasma jet (NTAPPJ) or plasma-treated water (PTW). The CFU (Colony Forming Unit) number of Escherichia coli inoculated on surfaces of mushrooms pre-treated with NTAPPJ or PTW was significantly reduced (about 60–75% for NTAPPJ and about 35–85% for PTW), and the reduction rate was proportional to the treatment time. Bacterial attachment and viability of the attached bacteria were decreased on NTAPPJ-treated mushroom surfaces. This may be caused by the increased hydrophilicity and oxidizing capacity observed on NTAPPJ-treated mushroom surfaces. In PTW-treated mushrooms, bacterial attachment was not significantly changed, but death and lipid peroxidation of the attached bacteria were significantly increased. Analysis of mushroom quality showed that loss of water content was greater in mushrooms treated with NTAPPJ compared to that in those with no treatment (control) and PTW treatment during storage. Our results suggest that pre-treatment with NTAPPJ or PTW can improve the antibacterial quality of mushroom surfaces by decreasing bacterial attachment (for NTAPPJ) and increasing bacterial lipid peroxidation (for both NTAPPJ and PTW).