Min Plasma Treatment Research Articles

Multimodal intelligent approach to low-temperature atmospheric plasma processing of apple slices before drying.

This study presents a comprehensive analysis of the impact of plasma treatment on the browning inhibition. A 30 min plasma treatment resulted in a pronounced decrease in the concentration of flavan-3-ols, which play a pivotal role in antioxidant defense and browning prevention. This significant reduction is likely due to plasma-induced oxidative stress, which can lead to the breakdown of these compounds or their conversion into other phenolic structures. Simultaneously, a slight increase in dihydrochalcones and flavonols was observed, suggesting a selective effect of plasma on different phenolic classes. The increase in these compounds could be attributed to the plasma's ability to induce specific reactions that generate these phenolics from other precursors present in the apples. The reduction in flavan-3-ols may affect the antioxidant capacity and health benefits associated with the apples, while the increase in dihydrochalcones and flavonols could have a positive impact on the flavor profile and potential health-promoting properties. Moreover, these modifications could contribute to the extension of shelf-life and maintenance of sensory qualities, making plasma treatment a valuable tool in the food industry for enhancing product stability and consumer appeal.

Cellular response to plasma-generated electrical and chemical stimulation of equal electricity

Plasma medicine is a novel field of research that has the potential in life sciences, including cancer treatment. It has been believed that all of these potential applications depend on the chemical factor of the plasma. However, the electrical factors that are produced simultaneously with the chemical factors have not been researched thoroughly. To assess the effect of plasma on the response of cells, a system that enables simultaneous comparison of the effects of chemical and electrical factors of plasma with equal electricity was invented. This system separates the polarity of plasma and isolates the chemical species from the electric stimulation. Using this system, HT-1080 cells were exposed to plasma for 10 min, 1 h, and 24 h. The 10 min plasma treatment showed a clear difference in the polarity of plasma, where cells under exposure to positive plasma died while cells in other conditions survived. An hour of plasma treatment affected the cells under the negative plasma, where the cell viability was reduced to half. Meanwhile, the electric stimulation did not affect the cell viability but did alter the cell membrane. Collectively, this study demonstrates the differential effects of three factors (electric factor, positive plasma, negative plasma) under the same condition: both the electrical and chemical effects of plasma-generated stimuli with equal amounts of electricity were successfully observed.

An ultraviolet photodetector based on conductive hydrogenated TiO2 film prepared by radio frequency atmospheric pressure plasma

The growing demand for real-time ultraviolet (UV) monitoring calls for a simple, rapid, and low-cost strategy to prepare UV photodetectors (PDs). We prepare a wearable real-time UV PD based on hydrogenated titanium dioxide film synthesized by radio frequency atmospheric pressure plasma. The conductivity of our hydrogenated titanium dioxide is improved to 10.2 S cm−1, nine orders of magnitude higher than that of pristine titanium dioxide after 10 min plasma treatment. Plasma hydrogenation disrupts the surface crystal structure, introducing oxygen vacancies (OVs) that create self-doped titanium(III) and titanium(II) species. First-principles calculations indicate that the OVs raise the Fermi level of TiO2 and distort the lattice locally. Our optimized film has a distinctive periodic switching characteristic under intermittent illumination; its responsivity is good from 280 to 400 nm, peaking at 632.35 mA W−1 at 365 nm. The fabricated wearable sensor based on the optimized film effectively monitors the daily variation of ambient UV intensity in three typical weather types, transferring its data to a smartphone via Wi-Fi.

Cold plasma assisted synthesis of spinel-CoFe2O4 nanoparticle with narrow bandgap and high magnetic activity

Non-thermal plasma (NTP)-assisted catalysis offers a promising avenue with diverse applications, particularly in air and water treatment. This study aimed to investigate the utilization of NTP discharge for the synthesis of magnetically active nanoparticles (MANps). We have demonstrated that the NTP discharge-assisted low-temperature calcination effectively induces surface modification and crystallization, thereby enhancing magnetic susceptibility. Specifically, a 30 min plasma treatment at 200 °C (CF-P-200) facilitated the formation of crystalline particles, a phenomenon that was absent in materials synthesized without plasma treatment under similar operating conditions. High-resolution microscopy revealed an average particle size of about 6.7 nm, while EDX analysis unveiled surface oxygen defects in CF-P-200 compared to materials synthesized by conventional calcination at 600 °C (CF-T-600), resulting in a narrower bandgap (1.9 eV). Magnetization measurements conducted using vibrating sample magnetometry (VSM) displayed superior magnetic properties of plasma treated MANps, with a magnetization (Ms) of 91.80 emu/g and coercivity (Hc) of 888 Oe. These values outperformed those of materials calcined at 600 °C (Ms: 64.53 emu/g, Hc: 1289 Oe), emphasizing the efficacy of NTP discharge in enhancing magnetic characteristics during material synthesis.

Improving the textural and functional properties of soy protein isolate using dielectric barrier discharge (DBD) plasma-assisted pH-shifting

This study aimed to improve the textural and functional properties of soy protein isolate (SPI) through a plasma-assisted pH-shifting method to create an alternative to meat products. The SPI was treated with DBD plasma for 0, 5, 10, and 15 min and then subjected to pH-shifting of 10 and 12 for 48 h before being adjusted to a neutral pH. The changes in the secondary structure of protein were evaluated using FTIR spectroscopy, free sulfhydryl measurement, and scanning electron microscopy (SEM). Heating the pH-shifted suspensions resulted in the formation of SPI gels with a densely cross-linked polymer-like network. Rheological and textural properties indicated that the pH-shifting treatment of SPI led to the production of stiff gels, so that the gel hardness increased from ∼6.75 to ∼13.28 N after 15 min plasma treatment at pH 12-shifting. The DBD plasma pretreatment negatively affected the functional properties of the SPI and decreased the solubility about 12 and 8% after 10 min plasma treatment at pH-shifting 10 and 12, respectively. The plasma-assisted pH-shifting offered a new approach for preparing SPI gel with enhanced water holding capacity, potentially expanding the range of applications for SPI in food formulations that require gelling and texturizing functions.

Nanosecond pulsed discharge with plasma-functionalized TiO2 for the high efficiency degradation of tetracycline

Non-thermal plasma coupling with photocatalyst is recognized as a promising technology for the degradation of antibiotics, and improving the photocatalyst performance is one of the most significant strategies to improve the efficiency of plasma-catalytic systems. This study employed a nanosecond pulsed gas–liquid discharge coupled with plasma-functionalized TiO2 to achieve a high efficiency of tetracycline degradation and clarify the synergistic mechanism of nanosecond pulse discharge coupling with functionalized TiO2. Results showed that the degradation efficiency with functionalized TiO2 increased by 20% compared to the untreated TiO2 for 4 min-plasma treatment. It is also suggested that the effect of photogenerated holes and electrons can be promoted in the functionalized TiO2, as evidenced by the radical quenching experiments. The plasma-modified TiO2 catalysts were proven to have a good stability and recyclability. This study provides a new sustainable approach to enhance the performance of photocatalysts in the plasma system for environmental remediation.

Model Prediction and Optimization of Cefixime Trihydrate Removal from Simulated Wastewater through Advanced Plasma Technology

Plasma technology has received significant attention as an advanced oxidation technique for the efficient removal of pharmaceuticals from various wastewaters. In this study, cefixime trihydrate (CFX) was used as a typical pharmaceutical, and a stepwise optimization strategy was adopted to determine the experimental parameters that benefiting the generation of free radical. The removal rate of 20 mg/L CFX reached 94.8% after 60 min plasma treatment when the voltage was 12 kV, the discharge gap was 15 mm, and the number of needles was 5. Furthermore, through the prediction and optimization of the response surfaces mythology (RSM) and artificial neural networks (ANN) model, the removal rate of CFX increased to 95.8% when the voltage was 11.9 kV, discharge gap was 15 mm, the number of needles was 5, and treatment time was 60 min. Finally, based upon the change of solution absorbance before and after the UV-Vis scan for plasma treatment and free radical quenching experiments, ·OH, 1O2, and ·O2− mainly attacked the C=C of CFX and played an important role during the plasma treatment. Moreover, the toxicity of CFX solution after ·OH attack was reduced evidently compared with that of the initial CFX solution via further toxicity assessment.

The Effect of the Addition of Powdered Sumac (Rhus coriaria L.) and Cold Plasma Treatment on the Quality of Carrot Juice

The aim of the study was to investigate the effect of cold atmospheric plasma (CAP) and sumac powder (Rhus coriaria L.) on the pH, total soluble solids, color, content of phytochemicals (carotenoids and polyphenols), and microbiological quality of freshly pressed carrot juice. Experiments were carried out with sumac powder concentrations of 0.5 and 3%, which were added before or after 20 min plasma treatment using a gliding arc reactor. The combination of CAP and 3% sumac powder resulted in very effective microbial reduction (to an undetectable level on each day of testing). These juices were characterized by an extended microbiological shelf life of up to 72 h. Additionally, the juice which was first enriched with 3% sumac and then treated with cold plasma, even on the last day of testing, contained 34.36 mg/100 mL of polyphenols and 3.49 mg/100 g more carotenoids than the control samples. The total effect of the application of these method is highly important for the improvement of the quality and safety of carrot juice.

Effects of plasma treatment on surface insulation properties of epoxy composites

The surface of epoxy composite material working in DC electric field for a long time is easy to accumulate charge and cause flashover, which seriously reduces its insulation level and poses a threat to the safe operation of electrical equipment. In this study, SiO x films were deposited on the surface of nano-SiO2/ER nanoparticles by atmospheric pressure dielectric barrier discharge plasma vapor deposition technology using ethyl nor-silicate as a precursor. The effects of different deposition time on the deposition effect and the pressure level of the film surface were studied. Scanning electron microscope and atomic force microscope were used to characterize the surface morphology of the material, and the flashover voltage before and after deposition was measured. The results show that SiO x films of different thicknesses can be formed on the surface of the material at different times of plasma deposition. After extending the deposition time of the film, the film becomes more uniform and dense, the surface roughness of the material decreases continuously, and the electrical conductivity and flashover voltage along the surface increases continuously. After 10 min plasma treatment, the conductivity increased from 1.78×10−16 S to 2.3×10−13 S, while the flashover voltage along the surface increased from 19.29 kV to 22.66 kV, an increase of about 17.5%.

A peleg modeling of water absorption in cold plasma-treated Chickpea (Cicer arietinum L.) cultivars

Plasma processing appears to be the mainstay of food preservation in the present day due to its effectiveness in controlling microorganisms at low temperatures. Legumes are usually soaked before cooking. Six chickpea varieties (Kripa, Virat, Vishal, Vijay, Digvijay, and Rajas) were soaked in distilled water at room temperature, and Peleg model was fitted after plasma treatment. Cold plasma treatment was used at 40, 50 and 60 Watt with exposure times of 10, 15 and 20 min. K1 (Peleg rate constant) consistently decreased from 32.3 to 4.3 × 10–3 (h % − 1) for all six chickpea cultivars, indicating an increased water absorption rate with increasing plasma power and treatment time. It was lowest in 60 W 20 min plasma treatment in Virat cultivar. K2 (Peleg capacity constant) ranged from 9.4 to 12 × 10–3 (h % − 1) for all six chickpea cultivars. Thus, plasma treatment showed no effect on water uptake capacity (K2), as it did not increase or decrease consistently with increasing plasma power and treatment time. Fitting the Peleg model successfully revealed the correlation between the water absorption of chickpea cultivars. The model fit ranged from R2 ≥ 0.9873 to 0.9981 for all six chickpea cultivars.

Damage-free remote SF6 plasma-treated CNTs for facile fabrication of electrochemical enzyme biosensors

Remote SF6 plasma treatment of CNTs is performed to graft hydrophobic fluorine on the surface of CNTs. Fluorinated CNTs (F-CNTs) allow for the facile adsorption of enzyme molecules via hydrophobic interaction between F-CNTs and the hydrophobic patches of enzyme molecules. The loading of glucose oxidase (GOx) on F-CNTs correlates well with plasma treatment time. Interestingly, the Rct value of GOx/F-CNTs decreases when CNTs are treated with plasma for a short time such as 1 and 5 min, which is due to weakly-bound chemisorbed fluorine molecules on F-CNTs (semi-ionic C-F). As an example, the Rct value of GOx/F-CNT electrode with 1 min plasma treatment is 0.57 times lower than that of GOx/CNTs, while increasing its sensitivity by 2.5 times. Upon extending the treatment time such as 30, 45 and 60 min, the XPS results reveal the dominance of covalently-attached fluorine, leading to marginally-increased resistance and sensitivity. It is worthy of noting this work is the first report of simple enzyme adsorption on remote-plasma treated CNT surfaces together with its detailed mechanism studies, especially for the binding of enzyme molecules semi-ionic fluorine.

Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries

A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.

Investigation of Fludioxonil Reduction Using Non-Thermal Atmospheric Plasma through Experimental Simulation

In this study, the effect of non-thermal atmospheric plasma (NTAP) treatment on the reduction of residual fludioxonil (C12H6F2N2O2, 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) was investigated through experimental simulation. Fludioxonil is known for its high residual concentration on fruits and vegetables. To simulate residual fludioxonil reduction in the storage location prior to consumption of fruits or vegetables by consumers, we designed an experimental setup utilizing a gas distribution system and a cylindrical dielectric barrier discharge (DBD) plasma source. A cylindrical DBD plasma source was adopted to produce the plasma activated chemical species (O3). To evaluate the effect of plasma treatment on the reduction of residual fludioxonil, experiments were performed under three different conditions: varying concentrations and treatment times of O3, as well as the surface roughness of microscope slide glass. Based on the results, 10 min plasma treatment with an O3 concentration of 11.89 μL/L, which showed a 58.5% reduction rate, is recommended. The O3 concentration has a higher priority than the treatment time for reduction rates of residual fludioxonil.

Plasma jet decontamination of sulfur mustard and its analogues in water by oxidation effect

Atmospheric pressure plasma jet (APPJ), as an emerging clean and efficient technology, has been found a great potential for chemical warfare agents (CWAs) decontamination. In this study, we first proposed APPJ for the degradation of sulfur mustard (HD) and its surrogate 2-chloroethyl ethyl sulfide (2-CEES) in water. Under optimal conditions, the degradation efficiency of 2-CEES and HD reached 100 % after 5 min or 6 min plasma treatment. The degradation products of 2-CEES and HD were mainly non-toxic alcohols or low toxic sulfones, which can be degraded and converted into some small molecules (HCl, SO2, or CO2) under further plasma treatment. We then identified two dominant short-lived reactive species (·OH and 1O2) and long-lived reactive molecule (H2O2) and distinguished the effect of these three active particles during the degradation process of 2-CEES in water. This work provides detailed evidence of a novel decontamination strategy for HD and 2-CEES.

Effect of Ambient Plasma Treatments on Thermal Conductivity and Fracture Toughness of Boron Nitride Nanosheets/Epoxy Nanocomposites.

With the rapid growth in the miniaturization and integration of modern electronics, the dissipation of heat that would otherwise degrade the device efficiency and lifetime is a continuing challenge. In this respect, boron nitride nanosheets (BNNS) are of significant attraction as fillers for high thermal conductivity nanocomposites due to their high thermal stability, electrical insulation, and relatively high coefficient of thermal conductivity. Herein, the ambient plasma treatment of BNNS (PBNNS) for various treatment times is described for use as a reinforcement in epoxy nanocomposites. The PBNNS-loaded epoxy nanocomposites are successfully manufactured in order to investigate the thermal conductivity and fracture toughness. The results indicate that the PBNNS/epoxy nanocomposites subjected to 7 min plasma treatment exhibit the highest thermal conductivity and fracture toughness, with enhancements of 44 and 110%, respectively, compared to the neat nanocomposites. With these enhancements, the increases in surface free energy and wettability of the PBNNS/epoxy nanocomposites are shown to be attributable to the enhanced interfacial adhesion between the filler and matrix. It is demonstrated that the ambient plasma treatments enable the development of highly dispersed conductive networks in the PBNNS epoxy system.

Study on flexible surface dielectric barrier discharge plasma film for in situ inactivation of bacteria and viruses

COVID-19 is still pandemic in the world although it has lasted for more than two years, in situ real-time disinfection of curved surfaces in public places is extremely urgent. A flexible plasma film based on surface dielectric barrier discharge is proposed in this study. In situ disinfection effect and the influence of curvature on the performance are studied. The results showed that the film could in situ inactivate a variety of pathogens. Specifically, 10 min plasma treatment results in a log reduction of 3.10, 3.42, and 3.03 for Escherichia coli, Staphylococcus aureus, and vesicular stomatitis virus, respectively. The discharge power and disinfection effect of the film are independent of the curvature, which proves that it can be used for in situ disinfection of curved surfaces. It is speculated that the combined effects of a strong electric field and radical etching physical damage as well as the chemical damage of reactive oxygen and nitrogen species to the protein are the main reasons for the inactivation of pathogens. The inhibition of the film to Omicron type SARS-CoV-2 pseudovirus is 99.3%, and the killing rate to natural bacteria is 94.3%. The film can run for at least 10 h without significant reduction in disinfection effect. In addition, large-scale and digitalization increase the practical potential of a disinfection film. In conclusion, this film is expected to realize in situ real-time disinfection of curved surfaces such as the buttons of the elevator or instrument and door handles, which is of great significance in blocking the spread of COVID-19.

Measuring contact angles on hydrophilic porous scaffolds by implementing a novel raised platform approach: A technical note

AbstractContact angle (CA) analysis is a widely employed technique to assess the surface properties of solid samples, including in tissue engineering research where scaffolds are typically designed to be both porous and hydrophilic to enable cell and tissue infiltration. Paradoxically, the types of scaffolds that possess the most optimal hydrophilic surface properties for cell attachment are the most challenging surfaces to attain accurate CA measurements. Here, we propose the use of a small 3D printed platform to elevate samples above the CA measurement substrate and demonstrate reproducible and accurate CA measurements on a range of popular polymer scaffolds that had undergone 5 min plasma treatment to instigate hydrophilicity. Using four polycaprolactone or high‐density polyethylene scaffolds with porosity ranging from 35.8%–93.1%, 0° CAs were reproducibly observed by measuring the CA while the scaffolds were elevated on the 3D printed platform, compared to the highly variable false‐positive results when measuring the scaffolds while directly sitting on measurement substrates of various materials. This versatile, low‐cost modification to CA hardware overcomes the challenges associated with measuring the surface properties of porous, hydrophilic scaffolds and provides a simple tool for tissue engineering researchers to perform CA measurements for any biomaterial scaffolds to ascertain hydrophilicity which is used to infer the suitability of scaffold surfaces for cell attachment.

Surface modification of polyimide fibers for high-performance composite by using oxygen plasma and silane coupling agent treatment

In this study, the oxygen plasma and silane coupling agent composite treatment was used to modify the polyimide fiber surface to improve the interfacial properties. The oxygen plasma treatment introduced active groups on the fiber surface, which facilitated the grafting of silane coupling agent to the fiber surface. The surface morphology and chemical composition of fibers were characterized by scanning electron microscope and X-ray photoelectron spectroscopy. The results showed that after plasma treatment, the etching spots on the fiber surface increased with the plasma treatment time, and the surface O atom content, O/C ratio and C–O(H) bond ratio reached the highest value at 27 min plasma treatment. After the composite treatment, the surface Si atomic content reached the highest value after 27 min plasma pretreatment. Moreover, polyimide/polyamic acid unidirectional reinforced composites were prepared. In polyimide/polyamic acid composites, the interfacial shear strength of polyimide fibers first increased and then decreased with plasma treatment time, both in oxygen plasma treatment and in composite treatment, and increased by up to 36.98% and 61.68% respectively compared. In addition, the transverse tensile strength of polyimide/polyamic acid composites increased by 103.73% after composite treatment compared with the pristine specimens.

Superhydrophilic 3D-printed scaffolds using conjugated bioresorbable nanocomposites for enhanced bone regeneration

Scaffolds synthesized from synthetic polymers, though mechanically robust, are hydrophobic in nature, lack sufficient cell attracting cues and are not amenable to monitoring. These drawbacks, however, can be overcome by fabricating a new generation of biocompatible scaffolds with quantum nanoparticle additives and surface functionalization. The objective of the present work was to investigate the enhancement of cellular adhesion, growth, proliferation, differentiation and migration on polymer-based scaffolds. To achieve this, carbon dots (CDs) were melt blended with poly(L-Lactide) acid or PLA, followed by rapid prototyping to generate photoluminescent scaffolds with the advantages of hydrophilicity and built-in monitoring opportunity via two-photon microscopy. Apart from these, cell proliferation and migration aspects in the biological environment are found to be enhanced by oxygen plasma treatment which enables polymer superhydrophilicity. Carbon dots introduces nanoscale roughness, and plasma incorporates hydrophilic oxygen and hydroxyl groups on the scaffolds. After a 7 min plasma treatment, PLA-CD surfaces were found to gain superhydrophilicity (contact angle of 0˚) and cell proliferation increased by 70% relative to the untreated scaffold. Quantitative analysis and bioimaging showed significant increases in ECM mineralization. Thus, the plasma treated PLA-CD composite supports the potential for producing high-performance, monitorable scaffolds for tissue engineering.

Chlorinated disinfection by-product formation during DOM removal by discharge plasma: Insights into DOC structure alterations

Dissolved organic matters (DOM) are important precursors for chlorinated disinfection by-products (DBPs). Little information is available regarding correlations among DOM removal, DBPs formation, and DBPs-associated toxicity in the plasma process. In this study, four sources of humic substances (HAⅠ, HAⅡ, HAIII, and HAIV) were chosen as the targeted DOM, and their removal performances and DBPs formation were investigated. The removal efficiencies of UV254 for HAⅠ, HAⅡ, HAIII, and HAIV were 81.6%, 75.6%, 64.2%, and 79.5% after 60 min plasma treatment, respectively. Plasma oxidation resulted in conversion of high aromatic DOM to low molecular weight components. As a result, total DBP contents decreased by 68.1%, 59.4%, 41.6%, and 50.9% for HAⅠ, HAⅡ, HAIII, and HAIV after 60 min plasma oxidation, respectively. High aromatic components were the main precursors of trichloroacetic acid (TCAA) and trichloromethane; lower molecular weight components contributed to chloralhydrate formation. Reactivity and contents of N played major roles in dichloroacetonitrile formation. Total calculated toxicities of DBPs derived from HAI and HAⅡ decreased by 57.5% and 59.4% after 60 min treatment, respectively, while fewer changes were observed from HAIII and HAIV. Plasma oxidation significantly reduced C-DBPs toxicity, but more attention should be paid to N-DBPs toxicity with low C/N ratio.