Air Plasma Treatment Research Articles

Ultrathin, flexible, conductive silver nanowires@polyvinyl alcohol composite film fabricated via the combination of air plasma treatment and thermal sintering for electromagnetic interference shielding

• AgNWs@PVA composite films were fabricated via a unique combination method. • The AgNWs@PVA film shows high EMI SE of 55 dB at 11 μm ultra-low thickness. • The AgNWs@PVA film retains excellent stability after 2000 bending cycles. It remains still a challenge to prepare thin, flexible, conductive films for electromagnetic interference shielding, which are highly desired in next-generation electronic applications such as aerospace, medical and wearable devices, etc . Herein, silver nanowires@polyvinyl alcohol (AgNWs@PVA) composite films were fabricated via a unique combination of air plasma treatment followed by thermal sintering of AgNWs network. The prepared composite ultra-thin film (11 µm) with 24.2 wt% of AgNWs displays relatively low density of 1.58 g cm −3 . Remarkably, the sheet resistance and electromagnetic interference shielding effectiveness are separately achieved to 0.29 Ω/sq and 55 dB at the measured frequency range of 8.2 GHz to 12.5 GHz. These traits underscore a significant promising prospect of AgNWs@PVA film in the modern flexible electronic devices.

Modification of a Highly Permeable Thin-Film-Based Nanofiltration Membrane (PVC) to Increase Efficiency and Separation by Air Plasma Treatment

In this research, considering the superhydrophobic properties of nanofiltration (NF) membranes with very high permeability based on polyvinyl chloride (PVC), its surface modification by plasma and its effect on membrane performance have been investigated. To make membranes, PVC polymer was used as the base polymer, dimethylacetamide, and tetrahydrofuran in the ratio of 15:85 as a solvent. The surface modification of thin-film NF membranes under the effect of Air plasma in a plasma cleaner device applied with the power of 20, 40, and 60 W has been investigated. The best power to achieve the hydrophilic surface in irradiation for 5 min at a pressure of 80 mTorr in the chamber is 60 W, and the contact angle of 12° is obtained in this case. The results of the FTIR spectrum definitely confirmed the formation of amide and amine functional groups on the surface of the modified membrane compared to the control membrane, due to the formation of these polar functional groups, the modified surface became hydrophilic. Scanning electron microscopy (SEM) images showed that the surface of the membrane changed after plasma treatment and the plasma-treated membranes had a smoother surface than the control membrane. The surface roughness in AFM analysis was found to be 32.85 nm for the control membrane and 12.83 nm for the membrane modified by the plasma method. The results of CA showed a significant decrease in the contact angle from 101° to 12°, this change in contact angle clearly indicates the increase in the hydrophilicity of the surface of the modified membranes. The water flux increased with increasing applied power, and an opposite trend was observed for salt rejection. Salt rejection was measured at 76% for plasma-treated membranes and 85% for the control membrane. The computational results from the MATLAB code program, for example, water flux 29.0523 (L/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}~\cdot $ </tex-math></inline-formula> h) close to laboratory results 31 (L/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}~\cdot $ </tex-math></inline-formula> h), were obtained.

Appropriate software model for evaluating the effect of untreated and treated sisal fibre with different gauge length and strain rates for geotextile applications

Geotextiles are commonly used as reinforcement in building, engineering and road laying applications. The sisal fibre is one of the natural fibres which is used to reinforce soil and prevent damage. This sisal fibre is specifically helpful to fill gaps between roads to improve soil structure, and prevent soil erosion but allows the water to drain off. This paper is concerned with the study of the effect of gauge length on the strength and elongation of sisal fibres in untreated and treated states with sodium hydroxide at different concentrations and duration of treatment. The reason for applying sodium hydroxide treatment on sisal fibre is to remove the impurities from it and to improve the inter fibre adhesion with resin for producing a composite. The effective reinforcement of composites with plant fibres depends on the moisture content and the fibre matrix interfacial adhesion. Treatment with alkali improves the performance of fibres when they are used as composites. Also, the effect of strain rate on the strength and elongation of sisal in untreated and treated states has been investigated. The Weibull modelling software model has been used in many studies to quantify the degree of variability in the fibres. This paper deals with the application of an appropriate software model such as the Weibull distribution model for quantifying the variability in strength and elongation at different gauge lengths varied from 10 mm to 100 mm and also varied the strain rate from 10 mm/min to 500 mm/min. In addition to the Weibull distribution model, air plasma treatment and SEM (Scanning Electron Microscope) analysis on sisal fibre were also carried out in this paper. The result shows that the sisal fibre is more suitable for geotextile applications.

Surface activated Co3O4/MoO3 nanostructured electrodes by air-plasma treatment toward enhanced supercapacitor

Herein, nanostructured Co3O4, MoO3, and Co3O4/MoO3 composite electrodes were prepared via hydrothermal synthesis and investigated for supercapacitive properties. The Co3O4/MoO3 composite electrode with equal weight ratio (named C5M5) showed the highest electrochemical properties compared to other electrodes. Air-plasma treatment further enhanced electrochemical performances owing to synergistic effects and surface activation of the Co3O4/MoO3 composite. The air-plasma surface-activated Co3O4/MoO3 composite (i.e. C5M5-P) electrodes exhibited a specific capacitance of 141F g−1 at 1 A g-1 in 1 M potassium hydroxide electrolyte. The fastest charge transfer and smallest resistance (1.64 Ω) were recorded for optimal electrode as demonstrated by Nyquist plots analysis. The surface-controlled process provided more than 50 % of capacity for the scan rates above 0.2 mV s−1, indicating the efficient pseudocapacitive behavior and showing the outstanding rate capability. The C5M5-P electrode exhibited superior cycling stability with 91.4 % capacitance retention at 3 A g-1 for 1,000 cycles.

Furcellaran Surface Deposition and Its Potential in Biomedical Applications.

Surface coatings of materials by polysaccharide polymers are an acknowledged strategy to modulate interfacial biocompatibility. Polysaccharides from various algal species represent an attractive source of structurally diverse compounds that have found application in the biomedical field. Furcellaran obtained from the red algae Furcellaria lumbricalis is a potential candidate for biomedical applications due to its gelation properties and mechanical strength. In the present study, immobilization of furcellaran onto polyethylene terephthalate surfaces by a multistep approach was studied. In this approach, N-allylmethylamine was grafted onto a functionalized polyethylene terephthalate (PET) surface via air plasma treatment. Furcellaran, as a bioactive agent, was anchored on such substrates. Surface characteristics were measured by means of contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Subsequently, samples were subjected to selected cell interaction assays, such as antibacterial activity, anticoagulant activity, fibroblasts and stem cell cytocompatibility, to investigate the Furcellaran potential in biomedical applications. Based on these results, furcellaran-coated PET films showed significantly improved embryonic stem cell (ESC) proliferation compared to the initial untreated material.

Hydrophilic/Hydrophobic SiO2 Nanoparticles Enabled Janus‐Type Paper through Commercial Glaco Spraying and Air‐Plasma Treatment

AbstractFunctional paper‐based microdevices have been receiving wide attention in the research areas of microfluidic chips, soft actuators, etc. This work introduces the design and fabrication of a Janus‐type paper in which one side of the paper remains hydrophilic and the other side is hydrophobic. Such Janus‐type paper is prepared by directly spraying hydrophobic Glaco solutions and following air plasma treatment. The former treatment can cover the paper fibers with numerous hydrophobic SiO2 nanoparticles. Through optimizing the fabrication parameters of the air plasma, it can penetrate the filter paper in a controllable depth, resulting in effectively regulating the hydrophobic particles into hydrophilic ones. Thereafter, the antirotation and interfacial stability of the Janus paper are investigated. Finally, a liquid storage and contamination‐free analysis devices are demonstrated on the Janus‐type paper platform. Noting that the commercially nonfluoride coating (Glaco) and mature plasma instrument together make the fabrication method simple, rapid, users/environmental‐friendly, and mass‐produced. The method provides a new route to fabricate Janus‐type paper for potential multifunctional applications in microfluidic chips and smart actuators, and may open up new avenue to prepare Janus films in a simple/rapid way.

Preparation of Waterproof and Breathable Polyethylene (PE) Film Through One-Step Plasma Treatment

The waterproof and breathable multifunctional films have been widely used in advanced wear protection, medical treatment, monitoring, and the aerospace industry. In this research, we prepared a new class/kind of waterproof and breathable intelligent (WBI) films through plasma surface treatment, which can be applied in the health care field. After air plasma treatments, the structural properties of polyethylene (PE) film were observed by Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetry (TG), and Differential scanning calorimetry (DSC). It was found that plasma treatment etches PE fibers due to the sputter etching effect of plasma modification, leading to a crystallinity decrease. In addition, the changes in water contact angle, air permeability, and water vapor transmission rate of PE films were measured to illustrate their waterproof and breathable properties. After plasma treatment, the water contact angle of PE film reduced from 112.67∘ to 45∘, indicating the PE surface converted from hydrophobic into hydrophilic. The air permeability increased to 0.450[Formula: see text]mm/s and the water vapor transmission rate increased to 1419.788[Formula: see text]g/m[Formula: see text], which means the treated PE films are breathable but not permeable to liquid water. The improved performance in waterproof and breathability expands the application of PE film in the pharmaceutical field.

ATR-FTIR Analysis on Aliphatic Hydrocarbon Bond (C-H) Formation and Carboxyl Content during the Ageing of DC Air Plasma Treated Cotton Cellulose and Its Impact on Hydrophilicity

The surface of the cotton fabric was modified using a Direct current (DC) air plasma treatment and hence enhances its hydrophilicity. The Box-Behnken approach (design expert software) was used to optimise the input process parameters. The sample prepared under optimized condition is subjected to ATR-FTIR and Field Emission Scanning Electron Microscopy (FESEM) studies in order to determine the changes in hydrogen bond energies (EH), Total Crystallinity Index (TCI), Hydrogen Bond Intensity (HBI), Lateral Order Index (LOI), functionalization, lattice parameters (a, b, c &amp; β), degree of crystallinity (in %) and surface etching. The ageing of this sample has been studied by comparing the values of carboxyl content and AC-C/AC-O-C ratio calculated using data extracted from ATR-FTIR spectra of the sample recorded periodically for one month.

Comparative analysis of the germination of barley seeds subjected to drying, hydrogen peroxide, or oxidative air plasma treatments

AbstractAcceleration in germination time by 12–24 h for barley seeds treated with atmospheric air plasmas may have a significant economic impact on malting processes. In this study, the increase in germination rate and decrease in contamination level upon plasma treatment could not be directly correlated with any significant increase in the water uptake capacity, except for seeds exposed to mild drying treatment. A variety of germination essays have been carried out with seeds impregnated with an abscisic acid solution, a retarding factor of germination, treated with a peroxide solution, and/or subjected to the plasma and drying treatments. Results suggest that plasma and hydrogen peroxide treatments induce the formation of reactive oxygen and nitrogen species that affects the abscisic acid factor and accelerate the germination rate.

Tuning the Drug Release from Antibacterial Polycaprolactone/Rifampicin-Based Core-Shell Electrospun Membranes: A Proof of Concept.

The employment of coaxial fibers for guided tissue regeneration can be extremely advantageous since they allow the functionalization with bioactive compounds to be preserved and released with a long-term efficacy. Antibacterial coaxial membranes based on poly-ε-caprolactone (PCL) and rifampicin (Rif) were synthesized here, by analyzing the effects of loading the drug within the core or on the shell layer with respect to non-coaxial matrices. The membranes were, therefore, characterized for their surface properties in addition to analyzing drug release, antibacterial efficacy, and biocompatibility. The results showed that the lower drug surface density in coaxial fibers hinders the interaction with serum proteins, resulting in a hydrophobic behavior compared to non-coaxial mats. The air-plasma treatment increased their hydrophilicity, although it induced rifampicin degradation. Moreover, the substantially lower release of coaxial fibers influenced the antibacterial efficacy, tested against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Indeed, the coaxial matrices were inhibitory and bactericidal only against S. aureus, while the higher release from non-coaxial mats rendered them active even against E. coli. The biocompatibility of the released rifampicin was assessed too on murine fibroblasts, revealing no cytotoxic effects. Hence, the presented coaxial system should be further optimized to tune the drug release according to the antibacterial effectiveness.

Plasma Electroless Reduction: A Green Process for Designing Metallic Nanostructure Interfaces onto Polymeric Surfaces and 3D Scaffolds.

The design of metal nanoparticle-modified polymer surfaces in a green and scalable way is both desirable and highly challenging. Herein, a new green low-temperature plasma-based in situ surface reduction strategy termed plasma electroless reduction (PER) is reported for achieving in situ metallic nanostructuring on polymer surfaces. Proof of concept for this new method was first demonstrated on hydrophilic cellulose papers. Cellulose papers were dip-coated with different metal ion (Ag+ and Au3+) solutions and then subjected to hydrogen plasma treatment for this PER process. Transmission electron microscopy (TEM) analysis has revealed that this PER process caused anisotropic growth of either gold or silver nanoparticles, resulting in the time-dependent formation of both distinct spherical nanoparticles (∼20 nm) and anisotropic 2D nanosheets. Furthermore, we have demonstrated the adaptability of this process by applying it to hydrophobic fibrous and 3D printed polymeric materials such as surgical face masks and 3D printed polylactic acid scaffolds. The PER process on these hydrophobic polymer surfaces was accomplished via a sequential combination of air plasma and hydrogen plasma treatment. The metallic nanostructuring caused by the PER process on these hydrophobic surfaces was systematically studied using different surface imaging techniques including 3D confocal laser surface scanning microscopy and scanning electron microscopy. We have also systematically optimized the PER process on the surface of 3D scaffolds via varying the concentration of the silver ion precursor and by different postprocessing methods such as sonication and medium soaking. These optimization processes were found to be very important in generating uniform metallic nanoparticle-modified 3D printed scaffolds while simultaneously improving cytocompatibility. Through joint disk diffusion and inhibitory concentration testing, the antibacterial efficacy of silver coatings on face masks and 3D scaffolds was established. Altogether, these results clearly suggest the excellent futuristic potential of this new PER method for designing metallic nanostructured interfaces for different biomedical applications.

Enhancement of chemical, physical, and surface properties of electrospun PCL/PLA blends by means of air plasma treatment

AbstractPolycaprolactone (PCL) and poly(lactic acid) (PLA) are polymers with unique individual features, but their mixing can produce a new biodegradable material with well‐balanced properties, although with a disadvantage that both are highly hydrophobic materials. To improve this drawback, electrospun PCL/PLA blends with various weight ratios were superficially modified by air plasma. The changes undergone by the nanofibers were characterized using spectroscopic and microscopic techniques; water contact angle (WCA) was also determined. We demonstrated that the electrospun PCL/PLA blends did not suffer morphological changes, although it was observed an increase in the roughness and the O/C ratio (by XPS analysis) and, decrease in WCA values, when the PCL content dominates in the blend after the treatment. The surface characteristics of the scaffolds PCL/PLA blends can be improved after modification with plasma and by tuning the content of its components.

Effect of low-pressure radio-frequency air plasma on chitosan films

The effect of low-frequency (15 kHz), low-pressure (10 Pa) air plasma treatment on freshly prepared chitosan films at processing times from 3 to 10 min has been explored. The films were prepared using chitosan solutions in dilute acetic acid. The influence of the plasma exposure time on the composition, morphology, and hydrophilic properties of the film surfaces is discussed.

High-Performance and Water Resistant PVA-Based Films Modified by Air Plasma Treatment

Plasma treatment is considered a straightforward, cost-effective, and environmental-friendly technique for surface modification of film materials. In this study, air plasma treatment was applied for performance improvement of pure PVA, cellulose nanocrystal (CNC)/PVA, and CNC/oxalic acid (OA)/PVA films. Compared with the original performance of pure PVA, the mechanical properties and water resistance of air plasma treated films were greatly improved. Among them, the CNC/OA/PVA film treated by three minutes of air plasma irradiation exhibits the most remarkable performance in mechanical properties (tensile strength: 132.7 MPa; Young’s modulus: 5379.9 MPa) and water resistance (degree of swelling: 47.5%; solubility: 6.0%). By means of various modern characterization methods, the wettability, surface chemical structure, surface roughness, and thermal stability of different films before and after air plasma treatment were further revealed. Based on the results obtained, the air plasma treatment only changed the surface chemical structure, surface roughness, and hydrophobicity, while keeping the inner structure of films intact.

Organophosphorus toxic compounds degradation in aqueous solutions using single filament dielectric barrier discharge plasma jet source

In this paper, we report the degradation of four organophosphorus toxic compounds (Chlorpyrifos, Dimethoate, Parathion, and Dimethyl methylphosphonate) from aqueous solutions with different concentrations (5, 10, and 20 ppm), using an atmospheric pressure DBD (Dielectric Barrier Discharge) plasma source. The discharges were performed in Ar, Ar/N2, Ar/air, and Ar/O2 mixtures, at 100 W, for different treatment times. In order to investigate the degradation process, reactive gas species transferred in liquid were monitored by Optical Emission Spectroscopy (OES), and the liquid pH, conductivity, nitrate, and dissolved oxygen concentrations were measurements.The degradation products were determined by gas chromatography–mass spectrometry (GC–MS) investigation. The highest degradation percentages for the 20 ppm solutions were 99.72% for Parathion, 93.76% for Chlorpyrifos, and 85.55% for Dimethyl methylphosphonate, after 20 min of Ar/N2 plasma treatments, and 74.26% for Dimethoate, after 20 min of Ar/compressed air plasma treatment.

Using plasma-mediated covalent functionalization of rhamnolipids on polydimethylsiloxane towards the antimicrobial improvement of catheter surfaces

Controlling bacterial biofilm formation on silicone-based bloodstream catheters is of great concern to prevent related-infections. In this study, rhamnolipids (RLs), glycolipid biosurfactants, specifically a RLs mixture and the purified di-RL (RhaRhaC10:0C10:0) were covalently bonded to silicone with the intention of reaching long-lasting antibiofilm surfaces.RLs mixture and di-RL were identified by an UHPLC-MS method that also allowed the confirmation of compound isolation by automated flash chromatography. Silicone surfaces underwent air-plasma treatment, inducing reactive oxygen radicals able to promote the RLs grafting that was confirmed by contact angle, FTIR-ATR and AFM measurements. The antibiofilm activity towards different Gram positive strains was evaluated by colony forming units (CFU) count and confocal laser microscopy. In addition, protein adsorption and biocompatibility were also investigated.RLs were successfully grafted onto silicone and RLs mixture and RhaRhaC10C10:0 functionalized specimens reduced the biofilm formation over 2.3 log units against methicillin sensitive Staphylococcus aureus. Additionally, a decrease of 1 log unit was observed against methicillin resistant S. aureus and S. epidermidis. Functionalized samples showed cytocompatibility towards human dermal fibroblasts, hemocompatibility and no vascular irritation potential. The results mentioned above revealed a synergy between the antimicrobial and the anti-adhesive properties of RLs, making these compounds good candidates for the improvement of the medical devices antibiofilm properties.

Effect of plasma treatment parameters on the interfacial joining strength of overmolded hybrid fiber reinforced thermoplastic composites

AbstractIn this study, hybrid fiber reinforced thermoplastic composites (hybrid thermoplastic composites) with high interfacial joining strength were fabricated using a plasma treatment strategy and injection overmolding technique. A series of experimental investigations were carried out to ascertain the effects of various plasma treatments on the interfacial joining strength of the overmolded hybrid composites. Test results reveal that compared with the untreated continuous fiber reinforced thermoplastic (CFRT) substrates, the surface roughness of the CFRT substrates treated by plasma with air for the 10 min–160 W set‐up increases by 28.7%, the contact angle decreases by 50.5%, the silicon and fluorine are effectively removed, and the content of polar functional group increases remarkably, which bring about the increase of 24.76% of the interfacial shear strength of the overmolded hybrid composites. Further increase of plasma treatment time does not contribute to increase the interfacial shear strength of the overmolded hybrid composites. The interfacial shear strength at 60 W is 6.38% higher than that at 160 W, which is ascribed to the increase of the oxygen‐containing functional group content. Compared with the air and nitrogen plasma treatment, the interfacial shear strength of the overmolded hybrid composites after oxygen plasma treatment reaches the maximum value.

Preventing the Capillary-Induced Collapse of Vertical Nanostructures.

Robust processes to fabricate densely packed high-aspect-ratio (HAR) vertical semiconductor nanostructures are important for applications in microelectronics, energy storage and conversion. One of the main challenges in manufacturing these nanostructures is pattern collapse, which is the damage induced by capillary forces from numerous solution-based processes used during their fabrication. Here, using an array of vertical silicon (Si) nanopillars as test structures, we demonstrate that pattern collapse can be greatly reduced by a solution-phase deposition method to coat the nanopillars with self-assembled monolayers (SAMs). As the main cause for pattern collapse is strong adhesion between the nanopillars, we systematically evaluated SAMs with different surface energy components and identified H-bonding between the surfaces to have the largest contribution to the adhesion. The advantage of the solution-phase deposition method is that it can be implemented before any drying step, which causes patterns to collapse. Moreover, after drying, these SAMs can be easily removed using a gentle air-plasma treatment right before the next fabrication step, leaving a clean nanopillar surface behind. Therefore, our approach provides a facile and effective method to prevent the drying-induced pattern collapse in micro- and nanofabrication processes.

Plasma Surface Modification of Epoxy Polymer in Air DBD and Gliding Arc

We studied the epoxy polymer surface modification using air plasma treatment in a Gliding Arc (GA) plasma reactor and a pulsed Dielectric Barrier Discharge (DBD). We employed optical emission spectroscopy (OES) measurements to approximate the vibrational and rotational temperatures for both plasma sources, as well as surface temperature measurements with fiber optics and IR thermography to corelate with the corresponding hydrophilization of the epoxy material. Water contact angle measurements revealed a rapid hydrophilization for both plasma sources, with a slightly more pronounced effect for the air DBD treatment. Ageing studies revealed stable hydrophilicity, with water contact angle saturating at values lower than 50°, corresponding to a &gt;50% decrease compared to the untreated epoxy polymer. ATR-FTIR spectroscopy studies showed an additional absorption band assigned to carbonyl group, with its peak intensity being higher for the DBD treated surfaces. The spectra were also correlated with the surface functionalization via the relative peak area ratio of carbonyl to oxirane and benzene related bands. According to SEM imaging, GA plasma treatment led to no apparent morphological change, contrary to DBD treatment, which resulted in nano-roughness formation. The enhanced surface oxidation as well as the nano-roughness formation on epoxy surface with the air DBD treatment were found to be responsible for the stable hydrophilization.

Study on the monolayer dispersion behavior of SnO2 on ZSM-5 for NOx-SCR by C3H6: the remarkable promotional effects of air plasma treatment.

Aiming to fabricate more practical catalysts for NOx-SCR with C3H6, SnO2/ZSM-5 having different SnO2 loadings was prepared and treated with DBD air plasma. The dispersion of SnO2 on the H-ZSM-5 support and their interactions were investigated with both experimental methods and DFT calculations. SnO2 displays evident monolayer dispersion behavior, getting a threshold of 0.271 mmol 100 m-2 support. Plasma treatment improves significantly the SnO2 dispersion, hence amplifying the monolayer dispersion threshold to 0.380 mmol 100 m-2. XPS and DFT calculations have testified that plasma treatment strengthens strongly the SnO2-ZSM-5 support interaction, mainly through donating electrons from Sn4+ to Al3+ in the support, thus improving the dispersion of SnO2 at the same loadings. Consequently, the catalytic performance is remarkably improved because of the generation of more abundant surface acid sites and superoxide species devoted to the reaction. The sample having a SnO2 loading near the monolayer dispersion threshold shows the optimal activity in the corresponding catalyst series, demonstrating an evident threshold effect. Over SnO2/ZSM-5, the reaction goes through a Langmuir-Hinshelwood pathway, involving the adsorption and activation of both NO and C3H6 molecules. Surface mono-dentate/bridged-nitrate and carbonate species are the main reaction intermediates.