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The excessive and uncontrollable discharge of diverse organic pollutants into the environment has emerged as a significant concern, presenting a substantial risk to human health. Among the advanced oxidation processes used for the purification of wastewater, cold plasma technology is superior in fast and effective decontamination but often fails facing mixed pollutants. To address these issues, here we develop the new conceptual approach, plasma process, and proprietary reactor that ensure, for the first time, that the efficiency of treatment (114.7%) of two mixed organic dyes, methylene blue (MB) and methyl orange (MO), is higher than when the two dyes are treated separately. We further reveal the underlying mechanisms for the energy-efficient complete degradation of the mixed dyes. The contribution of plasma-induced ROS and the distinct degradation characteristics and mechanism of pollutants in mixed treatment are discussed. The electron transfer pathway revealed for the first time suggest that the mixed pollutants reduce the overall redox potentials and facilitate electron transfer during the plasma treatment, promoting synergistic degradation effects. The integrated frameworks including both direct and indirect mechanisms provide new insights into the high-efficiency mixed-contaminant treatment. The degradation products for mixed degradation are revealed based on the identification of intermediate species. The plasma-treated water is proven safe for living creatures in waterways and sustainable fishery applications, using in vivo zebrafish model bio-toxicity assay. Overall, these findings offer a feasible approach and new insights into the mechanisms for the development of highly-effective, energy-efficient technologies for wastewater treatment and reuse in agriculture, industry, and potentially in urban water networks.

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This study investigates the structural phase and dielectric properties of poly(vinylidenefluoride-co-trifluoroethylene) (P[VDF-TrFE]) thin films grown via atmospheric pressure (AP) plasma deposition using a mixed polymer solution comprising P[VDF-TrFE] polymer nano powder and dimethylformamide (DMF) liquid solvent. The length of the glass guide tube of the AP plasma deposition system is an important parameter in producing intense cloud-like plasma from the vaporization of DMF liquid solvent containing polymer nano powder. This intense cloud-like plasma for polymer deposition is observed in a glass guide tube of length 80 mm greater than the conventional case, thus uniformly depositing the P[VDF-TrFE] thin film with a thickness of 3 µm. The P[VDF-TrFE] thin films with excellent ß-phase structural properties were coated under the optimum conditions at room temperature for 1 h. However, the P[VDF-TrFE] thin film had a very high DMF solvent component. The post-heating treatment was then performed on a hotplate in air for 3 h at post-heating temperatures of 140 °C, 160 °C, and 180 °C to remove DMF solvent and obtain pure piezoelectric P[VDF-TrFE] thin films. The optimal conditions for removing the DMF solvent while maintaining the ß phases were also examined. The post-heated P[VDF-TrFE] thin films at 160 °C had a smooth surface with nanoparticles and crystalline peaks of ß phases, as confirmed by the Fourier transform infrared spectroscopy and XRD analysis. The dielectric constant of the post-heated P[VDF-TrFE] thin film was measured to be 30 using an impedance analyzer at 10 kHz and is expected to be applied to electronic devices such as low-frequency piezoelectric nanogenerators.

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Characterisation of the vibrational kinetics in nitrogen-based plasmas at atmospheric pressure is crucial for understanding the wider plasma chemistry, which is important for a variety of biomedical, agricultural and chemical processing applications. In this study, a 0-dimensional plasma chemical-kinetics model has been used to investigate vibrational kinetics in repetitively pulsed, atmospheric pressure plasmas operating in pure nitrogen, under application-relevant conditions (average plasma powers of 0.23-4.50 W, frequencies of 1-10 kHz, and peak pulse powers of 23-450 W). Simulations predict that vibrationally excited state production is dominated by electron-impact processes at lower average plasma powers. When the average plasma power increases beyond a certain limit, due to increased pulse frequency or peak pulse power, there is a switch in behaviour, and production of vibrationally excited states becomes dominated by vibrational energy transfer processes (vibration-vibration (V-V) and vibration-translation (V-T) reactions). At this point, the population of vibrational levels up to v ⩽ 40 increases significantly, as a result of V-V reactions causing vibrational up-pumping. At average plasma powers close to where the switching behaviour occurs, there is potential to control the energy efficiency of vibrational state production, as small increases in energy deposition result in large increases in vibrational state densities. Subsequent pathways analysis reveals that energy in the vibrational states can also influence the wider reaction chemistry through vibrational-electronic (V-E) linking reactions (N + N 2 ( 40 ⩽ v ⩽ 45 ) → N ( 2 D ) + N 2 ( A ) and N + N 2 ( 39 ⩽ v ⩽ 45 ) → N + N 2 ( a ' ) ), which result in increased Penning ionisation and an increased average electron density. Overall, this study investigates the potential for delineating the processes by which electronically and vibrationally excited species are produced in nitrogen plasmas. Therefore, potential routes by which nitrogen-containing plasma sources could be tailored, both in terms of chemical composition and energy efficiency, are highlighted.

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This study systematically investigated an atmospheric pressure plasma reactor with a centered single pin electrode inside a dielectric tube for depositing the polyaniline (PANI) thin film based on the experimental case studies relative to variations in pin electrode configurations (cases I, II, and III), bluff-body heights, and argon (Ar) gas flow rates. In these cases, the intensified charge-coupled device and optical emission spectroscopy were analyzed to investigate the factors affecting intensive glow-like plasma generation for deposition with a large area. Compared to case I, the intense glow-like plasma of the cases II and III generated abundant reactive nitrogen species (RNSs) and excited argon radical species for fragmentation and recombination of PANI. In case III, the film thickness and deposition rate of the PANI thin film were about 450 nm and 7.5 nm/min, respectively. This increase may imply that the increase in the excited radical species contributes to the fragmentation and recombination due to the increase in RNSs and excited argon radicals during the atmospheric pressure (AP) plasma polymerization to obtain the PANI thin film. This intense glow-like plasma generated broadly by the AP plasma reactor can uniformly deposit the PANI thin film, which is confirmed by field emission-scanning electron microscopy and Fourier transform infrared spectroscopy.

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Functionally graded materials (FGMs) exhibit unique properties and are expected to deliver outstanding and stable performance under extreme conditions. High-voltage, high-power FGM-based electric insulation commonly fails because of inadequate surface charge control (flashover) performance and stability of stacked layers of dielectric materials with graded permittivity εr. Here, we address these issues by interfacing the rutile and anatase TiO2 layers on a ceramic with very different εr values of 110, 48, and 9, respectively, using scalable, environment-benign, and energy-efficient atmospheric pressure plasma processing. The FGM drastically reduces the maximum electric field along the optimized surface by 66% and increases surface flashover voltage by 36 %, while featuring a remarkable (120/180 days) long-term stability. The mechanisms of the plasma-enabled graded layer formation are presented, which can be used for precise engineering of FGMs for diverse applications in other fields.

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Developing a low-cost depyrogenation process is vital in extending medical applicability of polymers that can be used in medicine. We present an overview of the plasma-based depyrogenation literature and address the need to develop a non-thermal plasma-based depyrogenation process for delicate materials such as chitosan. We present a low-cost plasma apparatus to treat chitosan powder in hermetically sealed bags. We decouple the experiments into two; depyrogenation experiments for dried standard endotoxin on glass slides, and chitosan modifications analysis through FTIR spectroscopy. We demonstrate depyrogenation efficacy with up to a 4-log reduction in endotoxin levels and discuss minor changes observed in plasma-treated chitosan.

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A compact low-temperature plasma jet device was developed to use ambient air as plasma gas. The device was driven by a 2.52-kV high-voltage direct-current pulse in a burst mode, with a repetition rate of 2 kHz. The maximum plasma discharge current was 3.5 A, with an approximately 10 ns full-width half-maximum. Nitric oxide, hydroxyl radical, atomic oxygen, ozone, and hydrogen peroxide-important reactive oxygen and nitrogen species (RONS)-were mainly produced. The amount of plasma-generated RONS can be controlled by varying the pulse-modulation factors. After optimization, the plasma plume length was approximately 5 mm and the treatment temperature was less than 40 °C. The preliminary bactericidal effects were tested on Staphylococcus aureus, Pseudomonas aeruginosa, and methicillin-resistant S. aureus (MRSA), and their biofilms. The results showed that the plasma can effectively inactivate S. aureus, P. aeruginosa, and MRSA in both time- and pulse-dependent manner. Thus, this produced plasma device proved to be an efficient tool for inactivating deteriorating bacteria. Further versatile utilization of this portable plasma generator is also promising.

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We briefly discuss the history of cold atmospheric plasma (CAP) applications in dentistry. The reasons for seeking innovative solutions in dentistry are reported, highlighting results showing the potential of plasma along with some still-open questions. Finally, we suggest the next steps on the road from the laboratory to the dental chair.

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The degradation of methylene blue in aqueous solution as a model dye using a non thermal microwave (2.45 GHz) plasma jet at atmospheric pressure has been investigated. Argon has been used as feed gas and aqueous solutions with different concentrations of the dye were treated using the effluent from plasma jet in a remote exposure. The removal efficiency increased as the dye concentration decreased from 250 to 5 ppm. Methylene blue degrades after different treatment times, depending on the experimental plasma conditions. Thus, kinetic constants up to 0.177 min-1 were obtained. The higher the Ar flow, the faster the degradation rate. Optical emission spectroscopy (OES) was used to gather information about the species present in the gas phase, specifically excited argon atoms. Argon excited species and hydrogen peroxide play an important role in the degradation of the dye. In fact, the conversion of methylene blue was directly related to the density of argon excited species in the gas phase and the concentration of hydrogen peroxide in the aqueous liquid phase. Values of energy yield at 50% dye conversion of 0.296 g/kWh were achieved. Also, the use of two plasma applicators in parallel has been proven to improve energy efficiency.

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A direct current atmospheric pressure glow microdischarge (dc-µAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-µAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO3 solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

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Since effective therapies for melanoma with BRAF(V600E) mutation are being developed, interest has been shown in the development of therapies for melanoma without BRAF(V600E) mutation. Recently, interest has also been shown in medical application of non-nequilibrium atmospheric pressure plasmas (NEAPPs). We previously suggested that repeated NEAPP irradiation to spontaneously developed benign melanocytic tumors in RFP-RET-transgenic mice (RET-mice) not only suppresses tumor growth but also prevents malignant transformation. In this study, we first confirmed that transcript expression levels of tumor growth regulators (CyclinD1, D2, E1, E2, G2 and PCNA but not CyclinG1) and tumor invasion regulators [Matrix metalloproteinase (MMP)-2, -9 and -14 and melanoma cell adhesion molecule (MCAM)] in melanomas were significantly higher than those in benign melanocytic tumors in RET-mice. We then showed that transcript expression levels of CyclinE1, G1 and G2 and MMP-2 and -9 in melanomas from RET-mice were significantly decreased by single NEAPP irradiation, whereas transcript expression levels of CyclinD1, D2, E2, PCNA, MCAM and MMP-14 were comparable in untreated and NEAPP-treated melanomas. Since no Braf(V600E) mutation melanomas have been found in RET-mice, our results suggest that single NEAPP irradiation is a potential therapeutic tool for melanoma without BRAF(V600E) mutation through modulation of the expression levels of tumor growth and invasion regulators.

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