Abstract An atmospheric-pressure plasma jet (APPJ) device was optimized by enlarging the plasma discharge region to enhance the production efficiency of plasma-activated water (PAW), particularly under air discharge conditions. The physicochemical properties of PAW were found to be strongly dependent on the working gas and treatment duration. Under the same discharge conditions, PAW prepared by air discharge contained higher concentrations of NO₃⁻ and NO₂⁻, whereas PAW prepared by Ar discharge was richer in O₃ and H₂O₂. Meanwhile, increasing the discharge time led to a continuous decrease in pH, accompanied by sustained increases in both conductivity and oxidation–reduction potential. In addition, the effects of PAW were further investigated under soilless conditions. The results indicated that PAW enhanced the water absorption capacity of seeds, while different PAW compositions induced varying degrees of modification to the seed coat. When the physicochemical properties of PAW were adjusted to the optimal range for maize seed growth, both germination rate and seedling growth were significantly promoted. These findings demonstrated the strong potential of PAW for agricultural applications.

The absorption characteristics of cylindrical surface plasmon resonance (CSPR) have been studied. We demonstrated that a single plasma column with CSPRs can achieve high absorptivity at the plasmon frequency. We also studied the effects of plasma density and collision frequency on the absorptivity. As both of them increase, the corresponding absorptivity tends to increase first and then decrease, but with different reasons. Such manifestation is explained by analyzing transmission and reflection spectra in both cases, as well as magnetic field distribution patterns at the frequency of plasmon. On the one hand, the increase in plasma density leads to the enhancement of plasmons, improving transmittance; On the other hand, the increase in collision frequency leads to a weakening of plasmons and an increase in reflectivity. Finally, we investigated the absorption characteristics of plasmons in the plasma photonic crystals (PPCs) structure and overcame the absorption attenuation caused by the increase in plasma density by increasing the number of plasma columns. Meanwhile, the absorption generated by surface plasmon resonance is not affected by the lattice constant of PPCs. The research has shown that efficient absorption can be achieved using CSPR, resulting in extremely high absorptivity when using fewer plasma columns. Finally, we verified the absorption ability of CSPRs through experiments.

Vertical graphene nanosheets (VGs) were synthesized on Cu, Ti, Si, and C substrates by helicon wave plasma chemical vapor deposition (HWP-CVD) method using CH4/Ar as precursors. The obtained samples formed vertical orientation structures of nanosheets-graphene as the scanning electron microscopy and TEM images indicated. Specifically, the VGs grown on Cu substrate exhibit a parallel arrangement with a wall spacing of approximately 450 nm. This structural characteristic facilitates efficient ion exchange channels and promotes low resistance for electron transport. The effect of substrate type on the growth mechanism of VGs was discussed. The relationship between the microstructure and electrochemical performance of the VGs grown on different substrates was investigated. The charge transfer resistance of the VGs/Cu is 20.75 S2, and the value of VGs/Ti, VGs/C and VGs/Si are 23.51 S2, 33.76 S2 and 66.40 S2, respectively. The robust vertical orientation structure of VGs holds promise for various applications, including catalyst support in fuel cells, conductive electrodes in photovoltaic cells, and energy storage devices like lithium-ion batteries and supercapacitors. This structural characteristic plays a pivotal role in advancing the development of next-generation energy storage technologies.

"Sputtering damage" arising from high-energy negative ions plays a pivotal role in shaping the characteristics of indium tin oxide (ITO) thin films deposited through direct-current magnetron sputtering (DCMS). To mitigate this issue, we employ DCMS with an external anode. The increment in anode bias VA from 0 to +60V effectively diminishes the average kinetic energy of negative ions such as O-, O2-and InO- by reducing the cathode voltage. Additionally, the flux of positive ions (e.g., Ar+, In+, Sn+, O+) increases and their ion energy distribution functions (IEDFs) exhibit supplementary peaks at plasma potentials. Both facilitate film crystallization, as evi-denced by the structural transition from subgrain to grain formations. Heightened surface roughness markedly enhances optical transmittance. Due to a reduced oxygen sticking coefficient, films grown with higher VA values exhibit increased oxygen vacancies, which serve as the primary charge carriers for ITO films. Consequently, ITO films attain their lowest resistivity (7.81 x 10-4 omega cm) and highest optical transmittance (78.71 %) at VA = +60V. This investigation underscores the significant influence of the external anode bias on both ion behavior and film growth, providing a viable approach to enhance the electrical and optical properties of ITO films.

In this study, we found a kind of edge state located at the interface between plasma photonic crystals (PPCs) and traditional photonic crystals, which depends on the property of the photonic band gap rather than the surface defect. Simulation and theoretical analysis show that by adjusting the plasma density, we can change the topological characteristics of the photonic band gap of PPCs. This makes it different from the photonic band gap of traditional PCs, and thus excites or closes the topological edge states. We further discussed the influence of plasma parameters on edge state characteristics, and the results showed that as the plasma density increased, the first photonic band gap (PBG) of the PPCs closed and then reopened, resulting in band inversion and a change in the PBG properties of the PPCs. We can control the generation of edge states through plasma and adjust the frequency and strength of the edge states. After the appearance of edge states, as the plasma density further increases, the first PBG of the PPCs will shift towards high frequencies and deepen. The frequency of edge states will shift towards higher frequencies, and their strength will also increase. We increased the first PBG depth of the PPCs by increasing the number of arrays and found that when the number of the PPCs arrays increased, only the intensity of the edge states would increase while the frequency remained unchanged. Therefore, flexible adjustment of edge state frequency and intensity can be achieved through plasma density and array quantity parameters. Our study demonstrates the properties of topological edge states in plasma photonic crystals, which we believe can provide some guidance for applications based on edge states.

Closing or opening the first two photonic bandgaps (PBGs) of plasma photonic crystals (PPCs) by adjusting the plasma parameters are studied. We first calculated the impedance of the band structure of one-dimensional PPCs and found that in the presence of plasma, the impedance under two certain frequencies can match that of the air. We have verified through simulation that when the two PBG frequencies and two impedance-matched frequencies are equal to each other, the two PBGs can be closed simultaneously under the same plasma density. On the other hand, a more common situation is that we need two plasma densities to, respectively, close the two PBGs located near different impedance-matched frequencies. At this point, by adjusting the plasma density, the PBGs can be closed in segments, that is, we can choose to close or open the corresponding PBGs at different plasma densities.

Silk fibroin (SF) has been widely used in biomedical applications for the hydrophilicity modification of high molecular polymer materials. However, the challenge remains to immobilize SF with high structure stability and strong adhesion strength between SF and the substrate. Here, we propose an effective two-step process for modifying polyethylene terephthalate (PET) with SF: dipping PET film in SF solution and subsequently carrying out plasma-assisted deposition in SF aerosol. The structure and property analysis revealed that the SF-modified PET (PET-SF) prepared using the two-step method exhibited superior structural stability and stronger adhesion strength compared to the dip-coating method and the plasma-assisted deposition method. In addition, PET-SF prepared using the two-step method resulted in a higher concentration of SF and an increased content of active groups on its surface, enhancing its hydrophilicity compared to the other two methods. Additionally, the influence of dipping time and deposition time in the two-step method was investigated. The results demonstrated that the dipping time for 6 h and the deposition time for 3 min resulted in maximum SF grafting amount with a highly stable structure. Furthermore, the PET-SF exhibited satisfactory hydrophilicity when the deposition time was more than 3 min and showed the most hydrophilicity surface at 8 min.

This study delves into ion behavior at the substrate position within RF magnetron discharges utilizing an indium tin oxide ( ITO) target. The positive ion energies exhibit an upward trajectory with increasing RF power, attributed to heightened plasma potential and initial emergent energy. Simultaneously, the positive ion flux escalates owing to amplified sputtering rates and electron density. Conversely, negative ions exhibit broad ion energy distribution functions (IEDFs) characterized by multiple peaks. These patterns are clarified by a combination of radiofrequency oscillation of cathode voltage and plasma potential, alongside ion transport time. This elucidation finds validation in a one-dimensional model encompassing the initial ion energy. At higher RF power, negative ions surpassing 100 eV escalate in both flux and energy, posing a potential risk of sputtering damages to ITO layers.

Preparation of Titanium dioxides loaded vertical graphene nanosheets (TiO2/VGs) composite films with heterojunctions by a multi-plasma combination method. Highly vertically oriented VGs were prepared by helicon wave plasma chemical vapor deposition (HWP-CVD), and TiO2 nanoparticles were deposited on VGs templates by ultra-high vacuum magnetron sputtering (UH-MS). By controlling the sputtering time of TiO2 nanoparticles to modulate the nanoparticle loading content. The morphology, structure, and photocatalytic performance of heterojunction TiO2/VGs composite films were investigated. The characterization results of morphology and structure show that the structure of VGs nanosheets is not altered by the increase of the deposited particle content, indicating that VGs have excellent mechanical properties as a template for TiO2 loading. As the deposition time of the TiO2 nanoparticles increases, the loading type progresses from epitaxial growth at the beginning to conformal deposition and eventually to gap-filling growth. Photoelectric performance tests showed that the heterojunctions were formed at the interface between TiO2 and VGs. The photovoltage test results show that the photogenerated carriers are effectively separated at the interface, and the nanosheets can promote the migration of separated electrons to the external circuit. The variation in photocurrent density shows a positive correlation with the number of TiO2 attachment sites and loading content on the surface of the VGs nanosheets.

Short-wavelength numerical fluctuations limit the choice of space step in conventional explicit particle-in-cell (PIC) simulations, and it is meaningful to study explicit particle movers with damping of numerical noises. In this work, we propose a strategy to guide the construction of such movers, in which the electric field acceleration is smoothed in the time domain and the unknown future acceleration is split into the sum of a known major quantity and an unknown minor quantity, with the latter being estimated as a combination of a series of known quantities through line approximation. We further design an explicit particle mover with damping for electrostatic PIC simulations. Dispersion analysis of cold plasma Langmuir wave shows that the mover provides damping of modes depending on the product of mode frequency and time-step, wherein the damping is strong at large time-step or high-frequency, which is helpful to reduce short-wavelength noise modes. The results of numerical experiments indicate numerical heating caused by poor resolution of electron Debye length can be suppressed effectively by the explicit PIC simulations running with the new mover while the accurate descriptions of desired physical phenomena are retained. Meanwhile, the mover tends to cool particles, with the cooling rate being considered tolerable in the case the product of the motion frequency and time-step is small. We believe that the proposed mover here is helpful for people to research the bounded plasma driven by RF source.

Metal coatings with micron thickness, high conductivity, and a unique structure that can provide exceptional electromagnetic interference (EMI) shielding performance to insulation substrates are highly desirable, especially if the production method is inexpensive, pollution-free, and efficient. In this study, the Ar/H-2 mixed atmospheric pressure plasma jet (APPJ) was utilized to reduce AgNO3 to produce PC + ABS substrates coated with silver nanoparticles (AgNPs). It was found that the low roughness AgNPs coating has a multilayer network structure, which could exhibit high conductivity and excellent EMI shielding effectiveness (SE). In conclusion, this method is an excellent choice for producing metal EMI shielding coating.

We deposited indium-tin-oxide (ITO) films on silicon and quartz substrates by magnetron sputtering technology in pure argon. Using electrostatic quadrupole plasma diagnostic technology, we investigate the effects of discharge power and discharge pressure on the ion flux and energy distribution function of incidence on the substrate surface, with special attention to the production of high-energy negative oxygen ions, and elucidate the mechanism behind its production. At the same time, the structure and properties of ITO films are systematically characterized to understand the potential effects of high energy oxygen ions on the growth of ITO films. Combining with the kinetic property analysis of sputtering damage mechanism of transparent conductive oxide (TCO) thin films, this study provides valuable physical understanding of optimization of TCO thin film deposition process.

3D nitrogen-doped vertically-oriented graphene nanosheets (3D N/VGs) were controllably prepared by helicon wave plasma chemical vapor deposition (HWP-CVD) employing argon, methane, and nitrogen by varying the N2 flow rate (RN2) without any catalyst and substrate heating during the growth. The effect of plasma gas phase species on the growth structure of N/VGs thin films was studied. The influence of nitrogen doping content on the structure and properties of VGs was analyzed. A growth model for the preparation of N/VGs by HWP-CVD was proposed. The results show that the elevated doping content of nitrogen atoms promotes enhanced CH4 disso-ciation and access to more H atoms, leading to an elevated nanosheet number density and a reduced growth rate. More excited N atoms could be embedded into the C vacancy to replace the missing C atom and restore the hexagonal network and increasing the nitrogen content. N/VGs with lower defect densities obtained with enhanced doping of nitrogen. The effective average distance between defects increases with nitrogen content, and the tunneling phenomenon is apparent, increasing resistance. Electrochemical performance tests showed that VGs with high nitrogen atomic content have higher specific capacitance and rate performance, up to 1340 mu F/cm2 and 91.7%, respectively.

The effect of nitrogen gas seeding on electron density, electron energy probability functions (EEPFs), ion energy distribution functions (IEDFs) and ion species concentrations downstream of an argon helicon wave plasma (HWP) beam is investigated by Langmuir probe, electrostatic quadrupole plasma analyser and optical emission spectroscopy. Neutral depletion is found at axial location Z = 45 cm downstream of the HWP source, which can suppress the electron loss and cooling at the axis caused by N-2 seeding. As the axial location increases to Z = 57.5 cm and then to 70 cm, neutral depletion becomes slight and the addition of N-2 can effectively modulate the electron density and EEPFs. IEDFs results indicate a decrease of the average ion energy with an increase of nitrogen admixture, which is consistent with the sheath voltage fall estimated based on the electron temperature and the proportion of each ion species. Moreover, compared with Ar+ ions, the IEDFs of N-2(+) and N+ ions present a shift towards the higher energy region, due to the radio frequency oscillating sheath effects

In this work, the antibacterial activity of cotton containing silver nanocapsules prepared by atmospheric pressure plasma (APP) deposition is investigated. The nanocapsules consist of a shell and a silver nanoparticle (AgNP) core, where the core is used to bring antibacterial activity, and the shell is utilized to suppress the potential toxicity of AgNPs. The surface morphology and the elements of the samples are analyzed by scanning electron microscopy (SEM), energy dispersive x-ray and x-ray photoelectron spectroscopy (XPS). The SEM results show that the skin of the cotton fibers will fall off gradually after APP treatment over 3 min, and the XPS results show that the Ag content will rise to 1.6% after APP deposition for 10 min. Furthermore, the antimicrobial activity tests show that the reduction rates of Escherichia coli and Staphylococcus aureus can achieve 100% when the sample is treated for 10 min, which exhibits excellent antibacterial activity. In addition, the UV absorption properties of the cotton will also be correspondingly improved, which brings a broader application prospect for antibacterial cotton.

The direct implicit particle-in-cell is a powerful kinetic method for researching plasma characteristics. However, it is time-consuming to obtain the future electromagnetic field in such a method since the field equations contain time-dependent matrix coefficients. In this work, we propose to explicitly push particles and obtain the future electromagnetic field based on the information about the particles in the future. The new method retains the form of implicit particle pusher, but the future field is obtained by solving the traditional explicit equation. Several numerical experiments, including the motion of charged particle in electromagnetic field, plasma sheath, and free diffusion of plasma into vacuum, are implemented to evaluate the performance of the method. The results demonstrate that the proposed method can suppress finite-grid-instability resulting from the coarse spatial resolution in electron Debye length through the strong damping of high-frequency plasma oscillation, while accurately describe low-frequency plasma phenomena, with the price of losing the numerical stability at large time-step. We believe that this work is helpful for people to research the bounded plasma by using particle-in-cell simulations.

In this study, Al-Al2O3 double-layer coating and Al-Al2O3 fusion coating were prepared on 316L stainless steel substrate by double target and double frequency magnetron sputtering. It was found that the Al/Al2O3 transition layer was formed between Al and Al2O3 by CO sputtering deposition, which effectively reduces the interlayer microstructure defects, and makes the Al-Al2O3 fusion coating have a denser interlayer structure than the AlAl2O3 double-layer coating. The deuterium permeation test of the coating was carried out at 823-1023 K. The deuterium resistance reduction factor of Al-Al2O3 fusion coating was 8-72, which was 2-3 times that of Al-Al2O3 double-layer coating. The deuterium permeation diffusion time of Al-Al2O3 fusion coating was 1/10 of that of AlAl2O3 double-layer coating. With the increase of penetration test temperature, it was found that the deuterium resistance reduction factor of Al-Al2O3 fusion coating increases significantly, which was because amorphous Al2O3 was transformed into more dense gamma-Al2O3 in high temperature test.

The electron heating characteristics of magnetic enhancement capacitively coupled argon plasmas in presence of both longitudinal and transverse uniform magnetic field have been explored through both theoretical and numerical calculations. It is found that the longitudinal magnetic field can affect the heating by changing the level of the pressure heating along the longitudinal direction and that of the Ohmic heating along the direction which is perpendicular to both driving electric field and the applied transverse magnetic field, and a continuously increased longitudinal magnetic field can induce pressure heating to become dominant. Moreover, the electron temperature as well as proportion of some low energy electrons will increase if a small longitudinal magnetic field is introduced, which is attributed to the increased average electron energy. We believe that the research will provide guidance for optimizing the magnetic field configuration of some discharge systems having both transverse and longitudinal magnetic field.

The secondary electron emission yields of materials depend on the geometries of their surface structures. In this paper, a method of depositing vertical graphene nanosheet (VGN) on the surface of the material is proposed, and the secondary electron emission (SEE) characteristics for the VGN structure are studied. The COMSOL simulation and the scanning electron microscope (SEM) image analysis are carried out to study the secondary electron yield (SEY). The effect of aspect ratio and packing density of VGN on SEY under normal incident condition are studied. The results show that the VGN structure has a good effect on suppressing SEE.

Herein we report the successful preparation of silver (Ag)-decorated vertically oriented graphene sheets (Ag/VGs) via helicon wave plasma chemical vapor deposition (HWP-CVD) and radiofrequency plasma magnetron sputtering (RF-PMS). VGs were synthesized in a mixture of argon and methane (Ar/CH4) by HWP-CVD and then the Ag nanoparticles on the prepared VGs were modified using the RF-PMS system for different sputtering times and RF power levels. The morphology and structure of the Ag nanoparticles were characterized by scanning electron microscopy and the results revealed that Ag nanoparticles were evenly dispersed on the mesoporous wall of the VGs. X-ray diffraction results showed that the diameter of the Ag particles increased with the increase in Ag loading, and the average size was between 10.49 nm and 25.9 nm, consistent with the transmission electron microscopy results. Ag/VGs were investigated as effective electrocatalysts for use in an alkaline aqueous system. Due to the uniquely ordered and interconnected wall structure of VGs, the area of active sites increased with the Ag loading, giving the Ag/VGs a good performance in the oxygen evolution reaction. The double-layer capacitance (C (dl)) of the Ag/VGs under different Ag loadings were studied, and the results showed that the highest Ag content gave the best C (dl) (1.04 mF cm(-2)). Our results show that Ag/VGs are likely to be credible electrocatalytic materials.