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Superhydrophobic and to some extent oleophobic paper surfaces are prepared using atmospheric pressure plasma etching. A novel dielectric barrier discharge operating in helium-oxygen mixture is used to rapidly etch organic material from paper surface and create hierarchical topography and subsequently a thin fluorocarbon film is deposited to modify the surface energy. The enhancement of surface topography is achieved via the selective removal of organic matter over inorganic calcium carbonate (calcite) fillers that co-exist in paper. The process led to the fabrication of roll-off superhydrophobic paper with water contact angles >150° and hysteresis <10° for all samples treated over 2 min with no deterioration of paper quality. Further treatment over 8 min resulted also in diiodomethane repellent surfaces. [ABSTRACT FROM AUTHOR]

In this study, four‐layer stacks of bleached, unrefined Kraft papers are exposed to a plane‐to‐plane dielectric barrier discharge at atmospheric pressure operated in a glow‐like discharge regime and sustained in a mixture of hexamethyldisiloxane and helium gases. Scanning electron microscopy confirms that the plasma‐deposited coating follows the roughness of the porous cellulosic substrate. Whereas fairly spatially homogeneous coatings are obtained on silicon, significant variations of the coatings' thickness, organic content, and water contact angle are observed along the gas flow lines on the Kraft paper. These effects are even more important in the presence of substrate outgassing. In addition, plasma‐generated species sequentially penetrate down to the fourth layer of the cellulosic substrate, rendering surfaces hydrophobic with very low water absorption kinetics. [ABSTRACT FROM AUTHOR]

Released in March 2023, GPT‐4 has shown remarkable proficiency in various scientific areas, including atmospheric pressure plasma research. The paper discusses how GPT‐4, supported by ScholarAI and Wolfram plugins, enhances research efficiency with its vast knowledge and inferencing skills. It focuses on plasma‐water‐based nitrogen fixation experiments, demonstrating GPT‐4's abilities in explanation, analysis, prediction, planning, and verification. The study also addresses challenges like interpreting non‐textual data and keeping pace with scientific advancements. It highlights GPT‐4's role in improving nitrogen fixation process efficiency, showcasing its utility in scientific analysis and decision‐making. The paper emphasizes the evolving role of AI in research and the need for the scientific community to adapt to the rise of more advanced AI systems. [ABSTRACT FROM AUTHOR]

An atmospheric pressure glow discharge in air stabilized by a magnetic field is reported. The plasma is fixed at a position when the direction of the Lorentz force and the direction of the air flow is opposite. Under such condition, a stable glow discharge can be achieved and the plasma parameters can be independently controlled by the applied voltage, the magnetic field and the air flow rate, which is not the case for the widely used gliding arc (GA) discharge. For applied voltage of 6.5 kV, air flow rate of 2 L min−1, and magnetic field of 0.11 T perpendicular to the paper pointing outward, the discharge voltage (Vdis) and discharge current (Idis) are 1.2 kV and 49.7 mA, respectively. The rotational and vibrational temperature is about 3420 K and 4550 K, respectively. The electron density is on the order of 1014 cm−3 and the reduced electric field of plasma is about 36.9 Td, which is favorable for vibrational excitation of N2 to promote the production of NOx. As the plasma is fixed at a position, all the gas has to pass the plasma region and treated by the plasma when they are flowing, which is not the case for GA discharge where only a little percentage of gas is actually treated by the plasma. The energy cost of NOx production for the plasma stabilized by magnetic field of 0.19 T pointing outward is about 2.65 MJ mol−1, which is 41% lower than the GA discharge. [ABSTRACT FROM AUTHOR]

For several years now, atmospheric pressure plasma has been discussed as a future technology. It is a key technology with a long and successful past. For many decades, corona treatment has been an atmospheric pressure plasma application, well established within the extrusion and converting industry. Corona technology has been applied in industrial use since the 1950s, mostly within converting polymer films and to some degree paper, board, and metal foil. Corona treatment is used to improve the adhesion of printing inks, lacquers, adhesives, and coatings. From this strong base, atmospheric pressure plasma is growing into new applications. This paper introduces atmospheric pressure plasma basics and compares modern atmospheric pressure plasma technologies for grafting chemical functional groups on polymer surfaces. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of three different ring electrode configurations (copper wire electrode [CWE], copper foil electrode [CFE], and copper block electrode [CBE]) on the characteristics of the ring–ring typed atmospheric pressure plasma jet (APPJ) and polyethylene terephthalate modification. The characteristics of APPJ were simulated and experimentally explored. The results show that APPJ with CWE has the maximum electric field magnitude, power, concentration of reactive species, and gas temperature. While CBE has the most uniform electric field distribution and the most stable discharge process. Besides, CWE has the maximum hydrophilization rate while the CBE has the most uniform modification area. The plasma characteristics and modification effect of APPJ with CFE fall in between. [ABSTRACT FROM AUTHOR]

The paper presents the effects of plasma treatment on agricultural seeds. Cucumber and pepper seeds, widely used in agriculture, were treated using the Diffuse Coplanar Surface Barrier Discharge (DCSBD) at atmospheric pressure in ambient air. The plasma treatment (4 s for pepper, 20 s for cucumber) led to an improvement of germination and germinating power. XPS confirmed chemical changes on the seed surface. The surface morphology of the plasma treated seeds showed no evidence of structural damage. The conclusion is that DCSBD proves to be able to reduce some of the microorganisms and pathogens affecting the seeds. Thanks to their technical simplicity and easy scaling‐up, DCSBD plasma sources open new opportunities for atmospheric pressure plasma application in the agricultural industry. [ABSTRACT FROM AUTHOR]

An atmospheric argon plasma jet has been used to explore the plasma penetration inside tubes of small diameter and the plasma treatment effect on the inner tube surface. The goal of this paper is to show how the tube size can influence the plasma jet penetration and the resulting surface effects on polyethylene tubes with diameters varying between 0.28 mm and 3.00 mm. Optical emission spectroscopy and light emission images have been used to investigate the distribution of active species along the tube length. To examine the plasma treatment effect on the inner tube surface, capillary action, water contact angle measurements and XPS analysis have been used. The results presented in this paper will clearly demonstrate the great potential of atmospheric pressure plasma jets for inner tube surface modification. [ABSTRACT FROM AUTHOR]

The current and potential applications of atmospheric pressure plasmas in medicine generate an increasing need to develop safe and reliable plasma devices for patient treatment. This paper shows how the estimation of safety risks, the stability of the generated plasma, and the effectiveness in the aimed application can orientate the design process of a specific atmospheric pressure plasma device intended for clinical use. A promising plasma jet device operated with air is optimized, leading to a configuration with a more advanced design that reduces the temperature of the effluent, prevents the material degradation and improves the isolation of the high voltage components. The effects of the plasma jet treatment are investigated by chemical analysis of demineralized water and inactivation tests on E. coli cultures. [ABSTRACT FROM AUTHOR]

In this paper, a detailed study is carried out on an argon plasma jet excited by a biased sinusoidal voltage. Results indicate that, with increasing the biased voltage from negative polarity to positive one, the resultant plume transits from solid to hollow. Through implementing fast photography, a plump guided bullet is found to propagate in the solid plume, in which a negative streamer mechanism is involved. However, a positive streamer mechanism is involved in the hollow plume. It behaves as a thin guided streamer starting out from the driven electrode end, which subsequently evolves into branching streamers propagating in the flow periphery. To investigate the formation mechanism of the two plumes, the intensity ratio of spectral lines is investigated. [ABSTRACT FROM AUTHOR]

The paper presents experimental results concerning pre‐sowing stimulation of Thuringian Mallow (Lavatera thuringiaca L.) seeds with non‐thermal plasma generated in GlidArc reactor (dry nitrogen, atmospheric pressure) and its effect on the germination process. Five groups of seeds characterized by different exposure times were used. The effect of cold plasma on seeds was analyzed by investigation of microscopic pictures of carbon coated seed surfaces registered by means of electron scanning microscope. Visible changes in the seed surface structure could enhance the formation of micro‐pores which may be involved in water absorption, thus facilitating faster seed germination. Pre‐sowing plasma stimulation of seeds improved germination parameters such as germination capacity and germination energy for all tested groups, relative to control. The highest germination parameters were obtained for seeds stimulated with plasma for the exposure times of 2 and 5 min. [ABSTRACT FROM AUTHOR]

Atmospheric Pressure Plasma Jet (APPJ) arrays are considered as one of the most promising methods for uniform plasma processing of large uneven surfaces. To improve the downstream uniformity and enhance the surface treatment effects, it is important to reveal the mechanisms of the jet‐to‐jet interactions of plasma plumes in the jet array. In this paper, the electrical, optical, and fluid characteristics of the He and Ar three‐channel one‐dimensional (1D) plasma jet arrays with cross‐field needle‐ring electrode structure are studied and compared. It is found that there are divergences in the outside plumes of the propagation trajectory by the repellency of the plasma bullets and the spatial uniformity of the He and Ar plasma jet arrays can be improved with a lower applied voltage and a higher gas flow rate. The deflection angle of side plumes with respect to the central one of He is larger than that of Ar jet array due to the lighter molecular weight and better discharge synchronization. The experimental results show that Ar jet array is more controllable and stable and is more suitable for the design of the practical, simpler, and cheaper scalable plasma jet arrays. [ABSTRACT FROM AUTHOR]

Porous ZnO nanocrystalline films have drawn research attention due to improvement in gas sensing, adsorption, photocatalytic, and photovoltaic applications. However, scalable synthesis of porous nanostructures has been a challenge. Here, This paper reports a very easy, fast, and scalable one-step process for synthesis and deposition of porous ZnO nanocrystalline film by low-temperature atmospheric pressure plasma. The plasma is generated with radio frequency power using a metallic zinc wire as a precursor. Nanostructures have been synthesized and agglomerate to form a porous film at the substrate. Energy band structure of the deposited film has been investigated to understand the corresponding band alignment, which is relevant to many applications. An in-depth study of the grown nanostructured ZnO film has been included and characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, kelvin probe measurement, ultra-violet/visible absorption, and photoluminescence. [ABSTRACT FROM AUTHOR]

A novel two‐dimensional atmospheric pressure plasma jet device is proposed for large‐area processing. A finite element algorithm is adopted to obtain the optimized dimensions of the designed device based on microwave power reflection coefficient |S11| and electric field intensity. The plasma parameters of electron density ne and electron temperature Te within 0.1 ms after microwave power input were analyzed. When plasma is fully excited, ne is close to 3.5 × 1018 m−3, and Te is calculated to be 2 eV. Besides, an experimental system is established, and microwave power of 70 W can process 30 L of argon per minute, which shows a high energy efficiency. Two plasma jets with a width of 10 mm and a length of 5 mm are successfully excited. In addition, reflected power measured by the power meter is only 9.5% of incident power, which is in good agreement with simulation results. [ABSTRACT FROM AUTHOR]

We report on a computational study of the intersection of plasma filaments in a dielectric barrier discharge with small particulates suspended in air or residing on surfaces. The relative location of the particle with respect to the streamer axis is important on plasma time scale considered in the paper. The particulates residing on the substrate surface are partially enveloped by the sheath formed beneath the filament and the substrate. Ion energies and fluxes incident on the particulate depend on dielectric properties of the underlying substrate materials. [ABSTRACT FROM AUTHOR]

For researchers wishing to generate an understanding of complex plasma systems, global models often present an attractive first step, mainly due to their ease of development and use. These volume averaged models are able to give descriptions of plasmas with complex chemical kinetics, and without the computationally intensive numerical methods required for spatially resolved models. This paper gives a tutorial on global modeling, including development and techniques, and provides a discussion on the issues and pitfalls that researchers should be aware of. Further discussion is provided in the form of two reviews on methods of extending global modeling techniques to encompass variations in either time or space. [ABSTRACT FROM AUTHOR]

Copper oxide films have been deposited successfully on borosilicate glass substrates with a copper containing nitrogen plasma at atmospheric pressure. This was done by using a non-thermal DC jet with a sacrificial electrode as copper source. The produced films have been systematically investigated by different methods, including scanning electron microscopy and X-ray photoelectron spectroscopy (XPS). It is demonstrated that various copper morphologies, such as nanoflakes, can be produced by non-thermal atmospheric pressure plasma sources. The XPS data suggest that the nanostructures produced in the deposition process consist mostly of Cu(II)O. The dominant shape of these nanoparticles is flake-like with a high aspect ratio. Furthermore, it is shown that the temperature during the deposition process is well below 70 °C, and thus, enables copper oxide deposition on heat sensitive materials. [ABSTRACT FROM AUTHOR]

In this paper, the effect of polyimide surface modification - using near-atmospheric pressure plasmas - on the line width and adhesion of inkjet-printed Ag was investigated by texturing and modifying the chemical composition of the polyimide surface. The polyimide surface was textured with He/O2, to increase the surface area of the polyimide substrate and it increased the water contact angle from 57 to 137°, when the textured polyimide surface was treated with a SF6 plasma after the texturing process. The textured polyimide surface also exhibited the increased adhesion strength of Ag film (by about two times), due to the increase in the contact area, as expected, according to the Wenzel model. The linewidth of the inkjet-printed Ag line decreased by about ten times from 330 µm (for the flat polyimide surface) to 23 µm (for the textured polyimide surface) in addition to having smoother line edges. [ABSTRACT FROM AUTHOR]

Surface treatment of polydimethylsiloxane (PDMS) with a rotative nozzle atmospheric pressure plasma jet (APPJ) was reported. Operating conditions were optimized by statistical design of experiments, using water contact angle and XPS as response variables; OES (optical emission spectroscopy) was used for plasma diagnosis. The nozzle-PDMS distance and the torch speed were the most influencing parameters and were optimum at 6.6 mm and 10.3 m s−1, respectively. The extent of hydrophobic recovery of treated PDMS, investigated by water contact angle measurements, was less than what reported in the literature for this amorphous polymer. However, the APPJ treatment proposed in this paper is meant to be inserted in line for a homogeneous surface treatment of PDMS for enhanced adhesion improvement to coatings or adhesives. [ABSTRACT FROM AUTHOR]

Protein adsorption on inorganic surfaces involves a complex mechanism which could be controlled by surface functionalization methods. A dry surface functionalization method for powders could be beneficial as compared to wet-chemical methods, since aspects like suspension preparation and subsequent drying can be avoided. This paper focuses on atmospheric pressure plasma technology for surface activation of hydroxyapatite powder as a carrier in oral administration applications, aiming at increasing the loading capacity of proteins. Hydroxyapatite powder is treated in N2 and N2H2 atmospheric plasma processes within a static and a dynamic reactor. The influence of plasma activation on the protein adsorption isotherms, powder characteristics: particle morphology, specific surface area, and particle size distribution; have been discussed. The nature and amount of functional groups are studied by zeta potential measurements, thermogravimetric analysis, and titration analysis. Atmospheric plasma treatment increases the protein loading up to 37% when hydroxyapatite powder is treated in pure N2 plasma whereas that of powder activated using N2H2 plasma increased by 13%. The increased protein loading can be attributed to the creation of nitrogen and oxygen containing moieties which cause an increased hydrophilicity after plasma treatment. [ABSTRACT FROM AUTHOR]

In this paper, we report a molecular beam mass spectrometer study of a time‐modulated radiofrequency (RF)‐driven atmospheric pressure plasma jet in Ar + 1% O2. Time‐resolved measurements of the absolute density of O3 during the RF modulation period revealed a temporal increase of O3 densities at the start and end of the power modulation. This increase correlates with the increase in O2 due to plasma‐induced transient vortices in the gas jet. Pseudo‐one‐dimensional plug flow modeling of the axial species densities as a function of distance match well with the experimentally recorded trends. The obtained results were used to assess the importance of the O flux in previously reported ClO− production in saline by the same plasma jet. [ABSTRACT FROM AUTHOR]

Plasma treatment of polypropylene (PP) is a well‐established method of improving its surface properties. However, the efficiencies of different plasma discharges are seldom compared. Herein, we discuss the differences in PP treated by three arc‐based commercial plasma jets working in dry air, Plasmatreat rotating plasma jet (PT‐RPJ), AFS PlasmaJet® (AFS‐PJ), and SurfaceTreat gliding arc jet (ST‐GA), and by the low‐temperature RF plasma slit jet (RF‐PSJ) working in argon. The AFS‐PJ has a significantly different reactive species composition dominated by nitrogen oxides. It induced higher thermal loads leading to surface damage. The other arc‐based jets (PT‐RPJ and ST‐GA) created the PP surface with higher oxygen and nitrogen concentration than the low‐temperature RF‐PSJ. It induced a higher adhesion strength measured on PP‐aluminum joints. [ABSTRACT FROM AUTHOR]

This work investigates the temporal dynamics of O atoms in nonequilibrium atmospheric pressure plasma (NAPP) generated by kHz nanosecond pulsed discharge. Two‐photon laser‐induced fluorescence (TALIF) method is used to measure the time resolution of O atom density from the first discharge pulse in two gas mixtures, He + 0.4%O2 and He + 0.4%air. The discharge frequencies of 1 and 10 kHz are considered in the experiment. The results show that the O atom density does not accumulate with increasing number of pulses in both gas environments at 1 kHz. However, at 10 kHz, a cumulative effect of O atom density with the number of pulses is observed in both gas mixtures. After 10 and 300 discharge pulses in He + 0.4%O2 and He + 0.4%air, respectively, the O atom density saturates at the same moment after each discharge cycle. It was found that even after a long operating period of discharge, the decay of O atom density during each discharge cycle is not negligible. The O atom density in He + 0.4%O2 varies in the range of 2.85 × 1021 m−3–4.29 × 1021 m−3 while the O atom density in He + 0.4%air varies in the range of 2.60 × 1021 m−3–3.19 × 1021 m−3. This indicates that the choice of diagnostic time points is important for the O atom density measurements when using TALIF to diagnose kHz pulsed NAPP. In addition, 0D plasma chemical kinetics models are developed for the two gas mixtures to investigate O atoms' production and consumption processes. The causes of the cumulative effect of O atom density at 10 kHz, the saturation effect, and the formation of the periodic variation trend are also investigated. The simulation results show that the consumption rate of O atoms and the O atom density are directly correlated. As the number of pulses increases, the O atom consumption rate increases, which gradually counteracts the number of O atoms generated during the pulse discharge. This leads to delay and saturation of the cumulative effect of O atoms. [ABSTRACT FROM AUTHOR]

This paper reports the characterization of a low‐power, atmospheric pressure plasma source developed for and successfully tested in applications of plasma medicine. The source produces plasma by ionizing a helium flow containing traces of air. The effluent gas is thus enriched in reactive oxygen and nitrogen species as well as helium metastable excited states. Electrical measurements, Schlieren imaging, OES and various chemical analyses and probes enabled us to fully characterize the plasma source and to determine some fundamental parameters for treating living samples such as the power feeding the discharge, the optimal source to target distance, the maximum exposure time, and to identify the major chemical species responsible for the biological action on exposed living matter. This paper reports the characterization of a low‐power, atmospheric pressure plasma source developed for and successfully tested in applications of plasma medicine. The source produces plasma by ionizing a helium flow containing traces of air. Electrical measurements, Schlieren imaging, OES, and various chemical analyses and probes enabled us to fully characterize the plasma source and to determine some fundamental parameters for treating living samples such as the power feeding the discharge, the optimal source to target distance, the maximum exposure time, and to identify the major chemical species responsible for the biological action on exposed living matter. [ABSTRACT FROM AUTHOR]

Here, we report on the optimized design for the needle‐to‐plane electrode geometry to generate the atmospheric air streamer‐to‐spark transition discharge over the surface of the water at the pulsed voltage of ±30 kV. This design contributes to an increase in the electric field at the head of air surface streamers during their propagation, which eventually evolves into a spark over water. The length of streamer‐to‐spark transition discharge is up to 150 mm, which is affected by the conductivity of water, the electrode polarity, and the horizontal distance between the high‐voltage pin electrode and the grounded plane electrode. Water is quickly activated by the streamer‐to‐spark transition discharge, which can be attributed to the dissolution of plasma‐generated species including long‐lived and short‐lived reactive species in the gas phase. Compared to the negative streamer‐to‐spark transition discharge, the positive one is more effective in increasing the biological reactivity of water. Analysis indicates that the positive ions in the positive surface streamers can dissolve in water, which contributes to the formation of reactive species in water, thus an increase in the biological reactivity of water. [ABSTRACT FROM AUTHOR]

Gas chromatography, optical emission spectroscope, high speed video camera were used to study the microwave discharge ignited near the end of the microwave antenna in aqueous solution of ethanol at different ethanol content and different incident microwave power. The pressure above the surface of liquid was close to atmospheric pressure. The main gas products were Н2, СО, С2Н2, СН4, С2Н4. H2 (≈60 vol%) and CO (≈30 vol%) are predominated. The composition of the reaction products in a microwave discharge is practically independent of incident power and ethanol content in the solution, but the total flow rate of gas products at the system output increases with an increase in the incident power and the ethanol content in solution. Best obtained characteristics of process of hydrogen production were: flow rate of hydrogen was of 3240 mL/min, concentration of hydrogen in gas mixture on the discharge outlet was of 59 vol%, maximum energy efficiency of hydrogen production was of 324 NL/kWh. [ABSTRACT FROM AUTHOR]

It is difficult to generate jet‐shaped He microwave plasma jets in ambient air. In this study, a dual‐channel pulsed microwave coaxial resonant discharge device is constructed. An atmospheric pressure pulsed microwave He plasma jet is formed when He passes through the central copper tube. And a spatially layered He/N2 plasma jet is produced when He and N2 are aerated through the central copper tube and the resonant cavity, respectively. The spatiotemporal ionization evolution process of the He/N2 plasma jet is determined in experiments. The ionization characteristics could be attributed to the combining interactions between the resonant excitation of locally enhanced electric fields, the ionization wave propagation, and the various particle states in the He/N2 plasma jet. [ABSTRACT FROM AUTHOR]

This work examines the combination of pulsed direct‐liquid injections with dielectric barrier discharge at atmospheric pressure for the deposition of organosilicon coatings using hexamethyldisiloxane (HMDSO) as the precursor and nitrogen as the carrier gas. In such conditions, deposition relies on the charging of micrometer droplets and their transport toward the substrate by the Coulomb force. The thin‐film morphology and extent of precursor fragmentation are strongly linked to the amount of energy provided by the filamentary discharge to HMDSO droplets. While cross‐linked and smooth coatings were achieved at low energies as in standard gas phase plasma polymers, viscous and droplet‐like structured thin films were deposited at higher energies. The latter material is attributed to the soft polymerization of HMDSO droplets related to plasma–droplet interactions. [ABSTRACT FROM AUTHOR]

This paper presents the use of a simple‐arranged, low‐cost, and flexible atmospheric pressure microplasma generation device (μPGD) with controlled gas discharge to achieve maskless atmospheric plasma‐enhanced chemical vapor deposition (PECVD) of SiOx films on both planar and nonplanar surfaces. The μPGD is mainly composed of a copper–polyimide–copper sandwich structure with predefined microfluidic channels. Uniform microplasmas of different shapes and dimensions were generated in the open air. SiOx films were masklessly deposited with well‐defined edges and good feature transfer fidelity. The SEM, EDS, XPS, and FTIR spectra of the deposited film confirm the SiOx structure. These results indicate that μPGD is able to achieve maskless PECVD of SiOx films in the open air, especially micropatterning on nonplanar surfaces. [ABSTRACT FROM AUTHOR]

The HelixJet, a plasma source operating under atmospheric pressure with RF power, was used for the synthesis of silicon nanoparticles (Si‐NPs) in the context of relevance in nanomedicine, sensor technology, and nanotechnology. The HelixJet was operated with a variety of He/Ar/H2/SiH4 gas mixtures to characterize the Si‐NPs in regard to their size, crystallinity, structure, and photoluminescence. Distinct varieties of nanomaterials in the size range from 3 nm to over 100 nm were synthesized depending on the operation parameters of the HelixJet. Admixture of H2 alongside high RF powers led to the formation of crystalline nanoparticles with a strong photoluminescence intensity, where the photoluminescence properties as well as the nanocrystal synthesis yield were tunable by adjustment of the synthesis parameters. Post‐synthesis in‐flight annealing allowed the formation of large crystalline nanoparticles. In addition, the experiments conducted in this study resulted in a design improvement of the HelixJet plasma source that extends the stability of the operating range. Furthermore, the added spatial separation of the He/H2 and He/Ar/SiH4 streams (SiH4 injection on‐axis) minimizes material deposition within the HelixJet and enables continuous long‐term operation. [ABSTRACT FROM AUTHOR]

Metal oxide coatings have a variety of applications in industrial processes. As some of them have bio-sensitive properties there is growing interest for their use in medical applications as well. Thus, the development of suitable deposition techniques is of major importance for these purposes. From these techniques plasma deposition at atmospheric pressure offers a promising approach as there is no need for vacuum systems accompanied by lower costs, less process time, and easier integration into existing process chains. In order to optimize the coating process, a good knowledge of the plasma is needed. In this work, we present investigations on the plasma properties performed by systematic optical emission spectroscopy (OES) measurements. [ABSTRACT FROM AUTHOR]

Plasma polymers have long been of interest as thin film coatings on biomedical devices and products, to generate desirable surface properties for favorable bio‐interfacial interactions. Plasma polymers have also been used as platforms for the covalent immobilization of bioactive molecules. More recently, additional aspects have been investigated, such as selective prevention of adhesion of microbial pathogens, either via plasma polymers per se or including antimicrobial drugs. Plasma polymers have also been investigated for the release of silver ions and small organic molecules. Complementing low‐pressure plasma approaches, processes at atmospheric pressure have attracted interest recently, including for nano/biocomposite coatings. This contribution reviews the use of plasma polymers for intended biomedical applications, with a focus on more recent topic areas. [ABSTRACT FROM AUTHOR]

We performed a free radical polymerization of acrylamide in an aqueous solution by a radio frequency‐driven atmospheric pressure plasma jet. The polymerization was catalyzed by simultaneous generation of nanoparticles resulting in a percentage polymer yield increased by a factor of 2–30 times. Polyacrylamide acted as a capping agent for the silver nanoparticle formation yielding smaller nanoparticles while uncontrolled growth and massive particles were observed without acrylamide for the same conditions. Both Fourier transform infrared and Raman spectroscopy show the formation of bonds of (poly)acrylamide with the silver particles suggesting that polymerization at least in part occurs at the surface of silver particles. As plasma enables reduction without the addition of chemicals, this procedure might be a novel biocompatible approach to generate polyacrylamide/silver nanocomposite hydrogels. [ABSTRACT FROM AUTHOR]

Plasma catalysis is attracting great interest due to its synergistic combination of catalytic and plasma reactor processes. To provide possible controlling methods to this tunability, two‐dimensional particle‐in‐cell/Monte Carlo simulations are applied to investigate the propagation mechanisms of plasma streamers in the porous catalyst in a surface dielectric barrier discharge. Dry air at atmospheric pressure is investigated under a subnanosecond voltage pulse. The results show that the presence of the catalyst pores could enhance the steamer intensity and control the direction of the streamers, yielding highly concentrated reactive species inside catalyst pores. The streamer propagation speed is enhanced by increasing the strength of cathode voltage. These high‐density plasma streamers with controllable direction could benefit many applications in plasma‐enhanced catalysis. [ABSTRACT FROM AUTHOR]

The significance of shield gases on atmospheric pressure plasma jet (APPJ) propagation over a horizontal dielectric surface using various diagnostic methods has been investigated. The obtained results imply that adding nitrogen as a shield gas only has an impact on the N2 reactive species generation, mainly close to the plasma effluent while argon shield gas can boost the optical emission intensity of all excited species, especially at distances further away from the plasma jet, which is in agreement with the observed length of the plasma propagation all over the surface. On the basis of the obtained results, the employment of a shield gas can improve the plasma jet efficiency to achieve the desired treatment effect on a flat surface. [ABSTRACT FROM AUTHOR]

Reduction of SnO2 to form spherical Sn particles and Sn etching are obtained by floating wire (FW)‐assisted medium‐pressure H2/Ar plasma. High‐density H2/Ar plasma (1014 cm−3) with a larger treatment area at medium pressure (10 kPa) produces a two‐times higher removal rate of SnO2 (0.111 mg/min) than that at atmospheric pressure with the same treatment area of 300 mm2. SnO2 film is removed from the glass surface by a two‐step process involving (1) reduction of SnO2 by FW‐H2/Ar plasma to form spherical Sn particles and (2) removal of low‐contact Sn particles by water‐based cleaning. High surface smoothness (roughness of 0.488 nm) and high optical transmittance (>92%) of treated samples indicate no damage compared to that of pristine quartz glass. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue including nanostructured copper oxide films, biocompatible atmospheric pressure plasma as a therapeutic approach in medicine and effects of low temperature argon plasma.

The simulation model of the pulsed dielectric barrier discharge plasma catalytic CO2 hydrogenation is established to numerically investigate the effects of Ni and Cu catalysts on the selectivity conversions to CH4 and CH3OH. Under plasma without catalyst, the electron impact CO2 and CO produce CO and C, and then stepwise hydrogenations of CO and C generate CH3OH and CH4. Under plasma with Ni catalyst, Langmuir–Hinshelwood (LH) reactions mainly form the CHx(s) and Eley–Rideal (ER) reaction CH3(s) + H → CH4 are the key paths of CH4 synthesis. Under plasma with Cu catalyst, the intermediate CH3O(s) is principally produced by the LH reaction between CH2O(s) and H(s), followed by the ER reaction CH2O(s) + H → CH3O(s). While CH3OH(s) is mainly produced by the ER reaction CH3O(s) + H → CH3OH(s), CH3O(s) + H(s) → CH3OH(s) + S is a rate‐limiting step owing to the higher reaction energy barrier. [ABSTRACT FROM AUTHOR]

A pulse‐modulated atmospheric pressure radio frequency (RF) plasma is used to prepare a dense TiO2 thin film at a low temperature. With certain plasma on time (Ton = 50 ms), the discharge temperature decreases with plasma off time (Toff), and the lengths of the thin films increase. An anatase TiO2 thin film was successfully deposited on a temperature‐sensitive substrate (polyethylene terephthalate). The transmission electron microscope (TEM) results show that the film is composed from anatase TiO2 nanoparticles grown through plasma in 0.07 s. By using laser light scattering, the TiO2 particles are found to be trapped above the substrate at about 0.27 mm during plasma on, which is close to the simulated plasma sheath thickness (0.26 mm). The deposition mechanism of pulse‐modulated atmospheric pressure RF plasma has been investigated. [ABSTRACT FROM AUTHOR]

This study explores the plasma‐induced modification of microfibrillated cellulose (MFC) foams in a plane‐to‐plane atmospheric‐pressure dielectric barrier discharge with helium and hexamethyldisiloxane as carrier and precursor gases, with and without a gas gap. When the foam took up all of the gas gap, filamentary discharges were generated and burn‐like damage was produced. This resulted in highly inhomogeneous deposits having both hydrophilic and hydrophobic domains. MFC foams taking up only a portion of the gas gap volume generated a homogeneous discharge and induced cellulose defibrillation. They generated effective hydrophobic surfaces on both the top and bottom of the foams. Oleophilicity measurements were also carried out, which support the possibility of an effective separation of oily wastewater using a green and renewable material. [ABSTRACT FROM AUTHOR]

The key processes in an atmospheric‐pressure plasma jet containing Ar and tetraethyl orthosilicate (TEOS) are studied by means of two‐dimensional imaging of the important discharge radicals: OH, CH, and atomic O. The kinetics of the species generation is investigated by laser‐induced fluorescence spectroscopy. The work is focused on the behavior of the ground‐state radicals' density as a function of the applied voltage and of the Ar/TEOS mixing ratio. First insights on the physicochemical mechanisms of precursor fragmentation are provided. The influence of precursor admixture and precursor fragmentation on the OH, CH radicals, and atomic oxygen kinetics is revealed. The dominant role of gas‐phase oxidation processes in CH radical formation and polymerization is discussed and analyzed. [ABSTRACT FROM AUTHOR]

In the European Union, foodborne outbreaks caused by Salmonella Enteritidis, related to eggs and egg products, have even been reported in 2018. Atmospheric pressure plasma is becoming increasingly important as a decontamination method. A semidirect cold atmospheric pressure plasma, the flexible electrode plasma source, was developed for treating whole hen's eggs. An average reduction of 1.16 and 0.95 log colony‐forming units (CFU)/egg was achieved for the total bacterial count of clean and dirty eggs, respectively. An inactivation of 4.1 log CFU/egg Salmonella Enteritidis was achieved with artificially inoculated eggshells. Selected quality parameters and sensory properties were analysed. Overall, the present study yielded promising results for a realistic implementation of an industrial prototype plasma source. [ABSTRACT FROM AUTHOR]

An innovative approach using the vapor axial deposition (VAD), for the preparation of silica‐based high‐power fiber laser preforms, is described in this study. The VAD uses a plasma deposition system operating at atmospheric pressure, fed by a single, chemically adapted solution containing precursors of laser‐active dopants (e.g., Yb2O3), glass‐modifier species (e.g., Al2O3), and the silica matrix. The approach enables simultaneous doping with multiple optically active species and overcomes some of the current technological limitations encountered with well‐established fiber preform technologies in terms of dopant distribution, doping levels, and achievable active core diameter. The deposition of co‐doped silica with outstanding homogeneity is proven by Raman spectroscopy and electron probe microanalysis. Yb2O3 concentrations are realized up to 0.3 mol% in SiO2, with simultaneous doping of 3 mol% of Al2O3. [ABSTRACT FROM AUTHOR]

This study reports a one‐step process for the formation of anti‐fog coatings on commercial glass substrates using the jet of an open‐to‐air microwave argon plasma at atmospheric pressure with hexamethyldisiloxane (HMDSO) as the precursor for plasma‐enhanced chemical vapor deposition. Optical microscopy and broadband light transmittance measurements revealed significant precursor fragmentation and gas phase association reactions when HMDSO was injected close to the tube outlet, resulting in powder‐like, hydrophobic, and semiopaque glass surfaces. On the contrary, injection of HMDSO close to the substrate led to smoother, homogeneous, hydrophilic, and transparent glass surfaces. In addition, transmittance measurements at 590 nm in humid air according to American Society for Testing and Materials standard tests revealed superior anti‐fogging properties to plasma‐treated glass substrates. On the basis of the optical emission and absorption spectroscopy measurements, electrons, metastable argon atoms, and hot neutral argon atoms were mostly responsible for the significant precursor fragmentation close to the tube outlet, whereas the contribution of hot neutrals and ultraviolet photons became important close to the substrate. [ABSTRACT FROM AUTHOR]

Recently, cold atmospheric pressure plasmas (CAPs) have provided many new opportunities in dermatology by providing a multimodal action of reactive agents (RA). This review critically examines the generation, transport, and physical effects induced by CAPs in dermatologic treatments. We introduce the most suitable plasma sources, which provide a multitude of physical effects on the skin without any electric or thermal shocks. The mechanisms of generation and transport of the key reactive species are introduced and examined from the viewpoint of their applications in dermatology. Special attention is paid to study the "plasmaporation" effect, which enables RA penetration through healthy and damaged skin. Plausible physical mechanisms involved in the CAP treatment of some of the most common skin diseases are analyzed. [ABSTRACT FROM AUTHOR]

Polyamide 12 (PA12) powder was exposed for up to 3 h to low pressure air plasma treatment (LP‐PT) and several minutes by two different atmospheric pressure plasma jets (APPJ) i.e., kINPen (K‐APPJ) and Hairline (H‐APPJ). The chemical and physical changes resulting from LP‐PT were observed by a combination of Scanning Electron Microscopy (SEM), Hot Stage Microscopy (HSM) and Fourier transform infrared spectroscopy (FTIR), which demonstrated significant changes between the plasma treated and untreated PA12 powders. PA12 exposed to LP‐PT showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from the surface functionalization and materials removal during the plasma exposure. However, it showed poor melt behavior under heating conditions typical for Laser Sintering. In contrast, brief PJ treatments demonstrated similar changes in porosity, but crucially, retained the favorable melt characteristics of PA12 powder. [ABSTRACT FROM AUTHOR]

Treatments of polymer films using either a MHz atmospheric pressure plasma jet (APPJ) or an atmospheric pressure surface micro-discharge (SMD) plasma are investigated. While the typical approach to determine relevant reactive species is to correlate surface effects with gas phase species measurement, this does not capture potential synergistic or other complex effects that may be occurring. Activation energy and directionality of the etching process can characterize what is occurring at the surface for these processes in more detail. The APPJ source shows an apparent activation energy of ~0.18 eV at 8 mm distance and up to ~0.34 eV at 16 mm distance for a temperature range of 20-80 °C tested with thin polymer films. The APPJ source shows directional etching at 8 mm distance with less anisotropy the more distance is increased. The SMD source has an apparent activation energy of ~0.8-0.9 eV at a distance of 3 mm. The SMD also only shows isotropic etching behavior. However the SMD surface chemistry changes significantly to less oxidation with increased temperature while the APPJ source induced modifications remain very similar with temperature change. The lower apparent activation energy of the APPJ-induced etching reactions as compared with low pressure work (0.5 eV) and observation of line-of-sight contribution to etching suggests the involvement of a directional species at closer distances facilitating the etching which falls off with increasing distance. The high activation energy of the SMD suggests that species with less capability for etching is responsible compared to the APPJ and low pressure plasma. The high surface oxidation from low temperature SMD treatments shows that the surface is being oxidized but not sufficiently to reach the desorption step of the etching process. [ABSTRACT FROM AUTHOR]

Fluoropolymer coated alanine films are treated by a dielectric barrier discharge and a gliding arc at atmospheric pressure as well as with gamma irradiation. The film surfaces and the underlying bulk materials are characterized before and after each treatment. The fluorine content decreases and the oxygen content increases at the fluoropolymer surfaces, while deposition of specific plasma energies in the alanine films is detected by electron paramagnetic resonance spectroscopy, indicating that not only the fluoropolymer surfaces but also the bulk alanine materials are modified. Differences of surface and bulk modification effects between the two plasma treatments are discussed in detail. [ABSTRACT FROM AUTHOR]

The use of low‐temperature plasmas for bio‐decontamination and sterilization has been gaining increased attention. In this study, a two‐dimensional array of integrated coaxial microhollow micro‐discharges generated in dry air at atmospheric pressure is used to treat metal surfaces (gas‐phase) and solution (liquid‐phase) contaminated with a known concentration of feline calicivirus (FCV). FCV acts as a surrogate for human norovirus, which is responsible for causing outbreaks of acute gastroenteritis in humans. The decontamination efficacy as well as the primary chemical pathways leading to virus inactivation in both the treatments are studied and compared. It is found that the humidity of the bio‐sample for gas‐phase treatment in dry air is required to achieve >5 log10 reduction in FCV titer within 3 min. The gas‐phase FCV inactivation is found to be due to a combination of ozone (O3) and reactive nitrogen species (RNS), most likely NOx. The liquid‐phase FCV inactivation mechanism is pH‐dependent and is primarily due to RNS, most likely acidified nitrites. O3 has a negligible effect on FCV suspended in solution. Previous studies performed in a batch reactor have shown that the inactivation pathways through O3 and RNS are mutually exclusive due to ozone poisoning at high NxOy concentrations. The present study employs a flow‐through system which avoids accumulation of reactive species and allows for the coexistence of NOx and O3 for the gas residence times used in this study, giving rise to these specific inactivation pathways. [ABSTRACT FROM AUTHOR]

Silica‐like films for moisture barriers were deposited on a polymeric substrate in an Atmospheric Pressure PECVD reactor using a N2/O2/TEOS gas mixture. Statically deposited silica films were characterized by spatially resolved ATR FTIR and revealed a clear gradient in the silanol concentration. Silanol is an impurity in the silica network, resulting in pore formation, thus a higher silanol content leads to a decrease in the film density. Hence the spatial non‐uniformity in the static profile results in a density gradient in the thickness of web‐rolled films. The gradual transition from a lower to a higher density film appeared to be an essential requirement for maintaining the film integrity on the polymer. Hence, the porous layer acts as an adhesion promotion layer for the dense top layer. These optimal layer properties are achieved in a continuous single processing step. [ABSTRACT FROM AUTHOR]