Non-thermal Plasma Research Articles

A general strategy for synthesizing bimetallic Pt-based nanoclusters supported on carbon black via non-thermal plasma

Downsizing Pt-based catalysts to generate a higher surface-to-volume ratio and maximize atom utilization efficiency has been recognized as an effective strategy to achieve high mass activity. However, the synthesis of homogeneous, ultra-small bimetallic nanoclusters remains a significant challenge due to the difficulties in controlling stoichiometry and surface state control, large miscible gaps between different metals and surface state changes induced by the reaction gas environment. In this paper, bimetallic Pt-based nanoclusters such as PtPd, PtRu, PtCu deposited on carbon black (Vulcan XC72R) were fabricated by the reduction of H2 plasma.The structure and morphology of those prepared catalysts were revealed by HAADF-STEM, HR-TEM, EDS and XPS. The results indicated the prepared Pt-based nanoclusters displayed high dispersibility and small size owning to the non-equilibrium characteristics of non-thermal plasma (NTPs). The average sizes of PtPd, PtRu and PtCu were 2.06 ± 0.68 nm, 3.66 ± 1.34 nm and 1.98 ± 0.7 nm, respectively. Meanwhile, the synthesized PtPd nanoclusters with the ratio of 3:4 exhibited high catalytic activity in the hydrogen evolution reaction (HER). The Pt3Pd4/VR-P displayed a low overpotential (19 mV) at 10 mA/cm2 and achieved a high mass activity of 5.4 A/mg for HER in 0.5 M H2SO4 solution, which was 13.8 times higher than those of the commercial Pt/C catalysts. Moreover, the Pt3Pd4/VR-P demonstrated excellent stability with a negatively shifting about 40 mV after 10,000 cycles at a current density of 10 mA/cm2, which was close to that of JM-Pt/C (32 mV). The results prove NTPs technology is effective for the preparation of bimetallic Pt-based nanoclusters.

Gravitational force-induced changes in collisionless shock wave behavior in a charge-varying nonthermal dusty plasma

Gravitational force-induced changes in collisionless shock wave behavior in a charge-varying nonthermal dusty plasma

Non-thermal atmospheric pressure gas discharge plasma enhances tendon-to-bone junction repair in a rabbit model

Non-thermal atmospheric pressure gas discharge plasma enhances tendon-to-bone junction repair in a rabbit model

Mechanical and statistical pathway for the experimental investigation of the dairy industry effluent using non-thermal plasma

Globally, there is still a demand for effective removal of industrial pollutants using modern treatment technologies. Therefore, to achieve industrial implementation, treatment efficiency and energy demand, at present the new Non-Thermal Plasma (NTP) technology is adopted to treat the dairy industry pollutants. Falling Film Dielectric Barrier Discharge reactor (FF-DBD) is developed whereas the reactor is further characterized by the various operating parameters including electric field, gas source, flow rate and pH for the removal of COD and lactose content for different experimental conditions. In this present study, experimental works are carried out in ‘lab-scale experimental hardware to analyze the degradation efficiency of dairy effluent based on COD and lactose. For the maximum of 68 % and 75.56 % of COD and lactose removal is achieved at the maximum voltage of 30 k,Vp-p. Moreover, the interaction between COD and lactose is analyzed by using ANOVA and the p-value is < 0.001. Comparing to the air, oxygen as a discharge gas in a DBD reactor gives more treatment efficiency because it produces more oxygen-based oxidative species. Further the 2D - simulation model is employed to find the velocity profile of effluent inside the FF-DBD reactor.

Preliminary Exploration of Low Frequency Low-Pressure Capacitively Coupled Ar-O2 Plasma

Non-thermal plasma as an emergent technology has received considerable attention for its wide range of applications in agriculture, material synthesis, and the biomedical field due to its low cost and portability. It has promising antimicrobial properties, making it a powerful tool for bacterial decontamination. However, traditional techniques for producing non-thermal plasma frequently rely on radiofrequency (RF) devices, despite their effectiveness, are intricate and expensive. This study focuses on generating Ar-O2 capacitively coupled plasma under vacuum conditions, utilizing a low-frequency alternating current (AC) power supply, to evaluate the system’s antimicrobial efficacy. A single Langmuir probe diagnostic was used to assess the key plasma parameters such as electron density (ne), electron temperature (Te), and electron energy distribution function (EEDF). Experimental results showed that ne increases (7 × 1015 m−3 to 1.5 × 1016 m−3) with a rise in pressure and AC power. Similarly, the EEDF modified into a bi-Maxwellian distribution with an increase in AC power, showing a higher population of low-energy electrons at higher power. Finally, the generated plasma was tested for antimicrobial treatment of Xanthomonas campestris pv. Vesicatoria. It is noted that the plasma generated by the AC power supply, at a pressure of 0.5 mbar and power of 400 W for 180 s, has 75% killing efficiency. This promising result highlights the capability of the suggested approach, which may be a budget-friendly and effective technique for eliminating microbes with promising applications in agriculture, biomedicine, and food processing.

Influence of Applied Discharge Voltage and Gas Flow Rate on Nickel Plasma Jet Parameters Diagnosed by Optical Emission Spectroscopic Technique

Abstract: In this work, we measure the plasma parameters by using an AC high-voltage power supply that generates a non-thermal plasma jet system at atmospheric pressure. A nickel (Ni) metal strip, with dimensions of 1.5 × 10 cm2, was connected to the anode electrode of the AC power supply. This nickel strip was immersed in a flask with a small amount of distilled water positioned below the plasma plume nozzle. Optical emission spectroscopy (OES) was used to diagnose the plasma system at different argon gas flow rates (1-5 L/min) and varying applied voltage values (11-15 kV). It is significant to know the processes accompanying plasma generation to measure their parameters which include the electron temperature (Te), electron number density (ne) of the plasma, Debye length (λD), and plasma frequency (fp). Our results showed an increase in the intensity of spectral lines with the increase in applied discharge voltage (11-15 kV). The maximum peak for ArI was observed at a wavelength of 811.531 nm, and the maximum peaks for nickel (Ni) were observed at wavelengths of 285.21 and 519.70 nm. Also, the results indicated a gradual increase in electron temperature (Te) and electron density (ne) values at the applied voltage of 0.403-0.468 eV. Likewise, the electron density (ne) was in the range of (11.486-13.851) × 1017 cm-3. Keywords: Atmospheric plasma jet, Nickel (Ni) plasma parameters, Electron temperature, Spectroscopic optical emission (OES).

Impact of Nonthermal Plasma Treatment on the Oxidation of Lipids with Different Unsaturation Degrees.

Nonthermal plasma (NTP) treatment of food presents a new technology for the industry but raises concerns about lipid oxidation due to the presence of reactive species. Considering the critical role of the degree of unsaturation in lipid oxidation, this study investigates NTP-induced oxidation across various unsaturated lipids. These lipids are six oil samples primarily containing one of the following methylesters: oleate, linoleate, linolenate, arachidonate, eicosapentaenoate, and docosahexaenoate. Samples were treated with a nonthermal surface dielectric barrier discharge. Plasma-induced effects were first examined by classical lipid oxidation indicators, such as the peroxide value and p-anisidine value. The specific volatile oxidation products, including hexanal, nonanal, trans-2-hexenal, and methyl 9-oxononanoate, were determined to further elucidate the impact of ozone-related oxidation. Monitoring the production of selected nonvolatile oxidation products, such as epoxy-, oxo-, and hydroxy fatty acid methylesters, confirmed that plasma treatment facilitated the decomposition of lipid hydroperoxide. Generally, the level of plasma-induced oxidation increased in parallel with the unsaturation degree of the studied samples, except for the quantity of individual volatile carbonyls. The long-term effect of NTP treatment was investigated by a stability test, revealing that the oxidative stability depended on the input gas of plasma treatment, the sensitivity of the treated sample, and the presence of antioxidants. Except for the focus on the NTP impact, this study offered a case study of a comprehensive investigation into lipid oxidation.

Efficacy of Atmospheric Non‐thermal Plasma Corona Discharge Under Dry and Wet Conditions on Decontamination of Food Packaging Film Surfaces

ABSTRACTFood packaging materials must be sterilized to prevent cross‐contamination of the product. Non‐thermal plasma (NTP) corona discharge can be an effective alternative sterilization method for packaging films. The inactivation efficiency atmospheric NTP corona discharge under dry and wet conditions against vegetative cells of Escherichia coli, Staphylococcus aureus and Bacillus subtilis, spores of B. subtilis and Clostridium sporogenes and fungal spores of Candida albicans, Penicillium expansum and Aspergillus niger on polymeric packaging films were studied. The maximum inactivation of these microorganisms was 5.58, 0.54, 1.51, 1.06, 2.47, 1.73, 2.80, 3.20 and 3.50 log, respectively. Microbial inactivation by the treatments was greatly enhanced under wet conditions. Gram‐negative bacteria were found to be more sensitive to NTP, but spores were more resistant than vegetative bacterial cells. Although fungi were less susceptible than bacteria in dry treatments, they became more sensitive than the Gram‐positive bacteria in wet treatments. Overall, plasma treatments under wet conditions achieved higher microbial inactivation and would be favourable over the dry treatment.

Enhanced Nonenzymatic Glucose Biosensor of ZnO Nanostructure via Nonthermal Plasma

The sensitive nonenzymatic sensing of glucose has been made feasible for the first time using a nonthermal plasma (NTP)-synthesized ZnO nanostructure. This work presents an interesting and novel method for surface modification. The effects of flow gas of Argon/Oxygen (20, 30 and 40 l/min) on the Zn foil surface and various properties were investigated. Optical emission spectroscopy OES has been used to characterize transmissions for positive and negative systems of Ar/O plasma. X-ray diffraction showed close adjacent tops and the strongest peak at Zn (101). EDX displays the constants (Ok_[Formula: see text], (Znk_[Formula: see text] and (Znk_[Formula: see text] and change in (ZnL_[Formula: see text]. Photoluminescence (PL) Analysis shows a shift at the vertex toward the left and then toward the right confirming the reaction of all PL spectra within a strong UV emission peak. Raman spectroscopy analysis demonstrates two clear peaks gradually shifting to the right with an increase in the percentage of gas flowing compared to the blank metal, and scanning electron microscopy (FE-SEM) images show changes in the shape of nanoparticles due to increasing gas flow, the surface of zinc metal is affected by cold plasma and forms particles with very small diameters ranging from 10.8[Formula: see text]nm to 123[Formula: see text]nm. Also altered the surface morphology where the nano shape changed from flower-like particles to sheets with diameters ranging 282.7–643.5[Formula: see text]nm and the sheets grew with the increase of gas flow to diameters ranging 132–710[Formula: see text]nm. ZnO nanostructures are employed as biosensor electrodes (nonenzymatic) glucose as the increase in current is proportional to the flowing gas (2.06E-03[Formula: see text]mA, 2.09E-03[Formula: see text]mA and 4.34E-03[Formula: see text]mA).

Unveiling the Mechanism of Plasma-Catalytic Low-Temperature Water-Gas Shift Reaction over Cu/γ-Al2O3 Catalysts.

The water-gas shift (WGS) reaction is a crucial process for hydrogen production. Unfortunately, achieving high reaction rates and yields for the WGS reaction at low temperatures remains a challenge due to kinetic limitations. Here, nonthermal plasma coupled to Cu/γ-Al2O3 catalysts was employed to enable the WGS reaction at considerably lower temperatures (up to 140 °C). For comparison, thermal-catalytic WGS reactions using the same catalysts were conducted at 140-300 °C. The best performance (72.1% CO conversion and 67.4% H2 yield) was achieved using an 8 wt % Cu/γ-Al2O3 catalyst in plasma catalysis at ∼140 °C, with 8.74 MJ mol-1 energy consumption and 8.5% H2 fuel production efficiency. Notably, conventional thermal catalysis proved to be ineffective at such low temperatures. Density functional theory calculations, coupled with in situ diffuse reflectance infrared Fourier transform spectroscopy, revealed that the plasma-generated OH radicals significantly enhanced the WGS reaction by influencing both the redox and carboxyl reaction pathways.

Non-thermal plasma-catalytic processes for CO2 conversion toward circular economy: fundamentals, current status, and future challenges.

Practical and energy-efficient carbon dioxide (CO2) conversion to value-added and fuel-graded products and transitioning from fossil fuels are promising ways to cope with climate change and to enable the circular economy. The carbon circular economy aims to capture, utilize, and minimize CO2 emissions as much as possible. To cope with the thermodynamic stability and highly endothermic nature of CO2 conversion via conventional thermochemical process, the potential application of non-thermal plasma (NTP) with the catalyst, i.e., the hybrid plasma catalysis process to achieve the synergistic effects, in most cases, seems to promise alternatives under non-equilibrium conditions. This review focuses on the NTP fundamentals and comparison with conventional technologies. A critical review has been conducted on the CO2 reduction with water (H2O), methane (CH4) reduction with CO2 to syngas (CO + H2), CO2 dissociation to carbon monoxide (CO), CO2 hydrogenation, CO2 conversion to organic acids, and one-step CO2-CH4 reforming to the liquid chemicals. Finally, future challenges are discussed comprehensively, indicating that plasma catalysis has immense investigative areas.

Electrified methane upgrading via non-thermal plasma: Intensified single-pass ethylene yield through structured bimetallic catalyst

Chemical valorization of methane (CH4) via modular electrified reactors could represent a profitable avenue for biogas producers. Ethylene (C2H4) is the most valuable product due to its large demand that results in high energy cost and carbon emissions. However, alternative electrified processes proposed so far cannot compete with the state-of-the-art fossil route in terms of energy efficiency. The catalytic plasma reactor presented in this work achieves 34.4 % C2H4 yield from non-oxidative CH4 coupling, by integrating a bimetallic Pd-Ag catalyst on the surface of a 3D-printed structured electrode in a nanosecond-pulsed-discharge plasma reactor. This performance sets a new benchmark for alternative C2H4 production, potentially relying purely on renewable energy. Onsite energy generation via the excess hydrogen produced in the process could allow recovery of 16 % of the input energy. Moreover, the process produces solid carbon deposit that can be collected on the surfaces in proximity of the plasma discharge. This residue shows amorphous features and significant incorporation of metal particles coming from the electrodes surface. Hence, its low surface area hampers its application as carbon black analogue.

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.

Enhancing Selectivity with Molecularly Imprinted Polymers via Non-Thermal Dielectric Barrier Discharge Plasma.

Molecularly imprinted polymers (MIPs) are synthetic polymers that mimic the functions of antibodies. Though MIPs are promising tools in various areas, achieving high selectivity in MIPs can be difficult. To improve selectivity, various approaches have been implemented; however, the role of polymerization methods or synthetic techniques in enhancing the selectivity of MIPs has not been studied and remains a crucial area for further research. MIPs are typically prepared from free radical reactions. Recently, we found that Dielectric Barrier Discharge (DBD) plasma can be used to initiate the polymerization of vinyl monomers. The DBD plasma method allows the monomers to associate with the template molecules and initiate polymerization with minimal disruption to the positioning of the monomers. We hypothesize that this could be a preferred method to prepare MIPs over the traditional radical reaction that may cause a disturbance of the pre-associated monomers on the templates for the polymerization. Chicken egg white serum albumin (CESA) was used as the template protein for the MIPs. Our results show that in all test conditions, approximately twofold improvement in selectivity was achieved, which is the primary performance metric for MIPs. This enhancement was evident across all categories, including MIPs prepared from various monomer combinations.

Bayesian Optimization of Low-Temperature Nonthermal Plasma Jet Sintering of Nanoinks.

In response to the escalating demand for flexible devices in applications such as wearables, sensors, and touch panels, there is a need for innovative fabrication approaches for devices made from nanomaterial-based inks. Subsequent to ink deposition, a pivotal stage in device manufacturing typically involves high-temperature sintering, posing challenges for heat-sensitive substrates. Nonthermal plasma jet sintering utilizing an atmospheric pressure dielectric barrier discharge (DBD) plasma jet enables sintering at room temperature and standard pressure, facilitating the sintering of printed nanoparticle films without compromising substrate or film surface integrity. However, determining optimal plasma jet sintering conditions can be challenging due to multiple processing variables with intricate interrelationships. This work employed Bayesian optimization (BO) and machine learning (ML) to identify optimal values for seven primary plasma jet sintering variables. Optimization yielded a 99.2% increase in the measured electrical conductivity for plasma jet-sintered indium tin oxide (ITO) films after five rounds of experiments. Moreover, the optimal sintering conditions achieved an electrical conductivity that was 81.4% of conventional furnace sintering at 300 °C, but was three times faster and with a peak substrate temperature below 47 °C. This result demonstrates the prospect of applying BO to optimize processing techniques for emerging low-temperature requirements.

Removal and Oxidation of Low Concentration tert-Butanol from Potable Water using Nonthermal Plasma Coupled with Metal Oxide Adsorption.

Taste and odor are crucial factors in evaluating the quality of drinking water for consumers. Geosmin is an example of a pollutant commonly found in potable water responsible for earthy and musty taste, and odor even at low concentrations. We have investigated the use of a hybrid two-step adsorption-mineralization process for low-level volatile organic compounds removal from potable water using dielectric barrier discharge over common metal oxides (MO). The system proposed is a proof of principle with tert-butanol (TBA) used as a model compound for geosmin removal/degradation during wastewater treatment when combined with an appropriate metal oxide adsorbent. Initial assessments of the adsorption properties of titania by density functional theory (DFT) calculations and experimental tests indicated that the adsorption of geosmin and TBA with water present results in only weak interactions between the sorbate and the metal oxide. In contrast, the DFT results show that alumina could be a suitable adsorbent for these tertiary alcohols and were reinforced by experimental studies. We find that while there is a competitive effect between the water and TBA adsorption from gaseous/liquid feed, the VOC can be removed, and the alumina will be regenerated by the reactive oxygen species (ROS) produced by a dielectric barrier discharge (DBD). The use of alumina in conjunction with NTP leads to efficient degradation of the adsorbate and the formation of oxygenated intermediates (formates, carbonates, and carboxylate-type species), which could then be mineralized for the regeneration of the adsorbent. A reaction mechanism has been proposed based on the in-situ infrared measurements and DFT calculations, while the removal of TBA with conventional heating is indicative of a gradual desorption process as a function of temperature rather than the destruction of the adsorbate. Furthermore, steady performance was observed after several adsorption-regeneration cycles, indicating no alteration of the adsorption properties of alumina during the NTP treatment and demonstrating the potential of the approach to be applied in the treatment of high throughput of water, without the challenges faced by the biocatalysts or formation of toxic byproducts.

Investigating cation distribution and photocatalytic response of non-thermal plasma treated MZnFe2O4(M = Ni, Mg, Mn) nanocomposite ferrites

Investigating cation distribution and photocatalytic response of non-thermal plasma treated MZnFe2O4(M = Ni, Mg, Mn) nanocomposite ferrites

Use of Non-Thermal Plasma as Postoperative Therapy in Anal Fistula: Clinical Experience and Results.

Anal fistula, characterized by abnormal tracts between the perianal skin and the anal canal, presents challenges in treatment because of its diversity and complexity. This study investigates the use of non-thermal plasma as a postsurgical therapy for anal fistula, aiming to promote healing and tissue regeneration. A specialized plasma reactor was designed to apply non-thermal plasma within the anorectal cavity practically. Non-thermal plasma treatment was administered to 20 patients including 10 undergoing fistulectomies and 10 undergoing fistulotomies. The average duration of non-thermal plasma application in the operating room was shorter for fistulotomies. The pain reported the day after surgery was similar in both groups. Improvements in the number of evacuations starting from the day after surgery, as well as the assessment of stool quality using the Bristol scale, indicated satisfactory intestinal recovery. Fistulotomy patients exhibited faster wound healing times. These findings underscore the efficacy of non-thermal plasma as a postoperative therapy for anal fistula, enhancing healing and recovery outcomes without increasing complication risks.

Effect of Plasma-Activated Water (PAW) Generated Using Non-Thermal Atmospheric Plasma on Phytopathogenic Bacteria.

Plasma-activated water (PAW) exhibits potent antimicrobial properties attributed to the generation of diverse reactive oxygen and nitrogen species. This study assessed the effectiveness of PAW in vitro against phytopathogenic Xanthomonas arboricola and Pseudomonas syringae pv. syringae, which cause diseases on ornamental plants. Extending the plasma activation time of water and the incubation time of bacterial suspension in PAW increased the effectiveness of PAW. Treatments consisting of PAW activation using a power output of 200 Watts and a frequency of 50 Hz at different activation times and target population incubation times revealed significantly different effectiveness against P. syringae pv. syringae and X. arboricola. X. arboricola (reduction of 4.946 ± 0.20 log10 CFU/mL) was more sensitive to PAW inactivation than P. syringae pv. syringae (reduction of 3 ± 0.15 log10 CFU/mL). The plasma activation of water for 20 min followed by incubation of bacterial population for 180 min was proven to be the most effective treatment combination. The plasma activation time dose required to reduce the population by 90% was 7.47 ± 1.09 min for P. syringae pv. syringae and 4.45 ± 1.81 min for X. arboricola incubated for 180 min in PAW. The results of this study have the potential to further contribute to assessment of the effects of PAW on pathogen infected plant tissues. In addition, the findings of this study could aid in further characterization of the reactive species formed during the plasma activation of water.

Development of hydrophobic graphenoid layer on Portland cement for non-thermal plasma method

This study focuses on the development of hydrophobic layer on Portland cement using graphenoid materials to enhance impermeability and hydrophobicity. X-ray diffraction analysis indicated that characteristic peaks associated with concrete, such as ettringite, calcium hydroxide, and calcite, remained intact. The application of graphenoid material produced by non-thermal plasma resulted in the formation of carbonaceous structures, minimally affecting the overall cement structure. Raman spectroscopy provided detailed insights into the composition, highlighting the presence of specific and indicating boundary defects. Moreover, contact angle measurements confirmed a substantial increase in hydrophobicity for the graphene-coated cement, with an average angle of 117° ± 4.72° demonstrated graphenoid material layers deposited over structural defects, effectively waterproofing and enhancing local hydrophobicity.