Search Results (13)

Previous studies have demonstrated that underwater low-temperature plasma is effective for synthesizing nanomaterials by generating plasma discharges between metal electrodes submerged in water. This study extends this approach to the one-step synthesis of MXenes containing titanium, molybdenum, and titanium–molybdenum composites through pulsed discharges in carbon tetrachloride, an oxygen-free, non-flammable solvent characterized by a high boiling point and low permittivity. By employing titanium and molybdenum electrodes in various configurations, three MXene samples were synthesized: Ti₂CT_X, Mo₂CT_X, and Mo₂TiC₂T_X. Characterization techniques, including UV-Vis spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, confirmed the successful synthesis of high-purity MXenes with distinct structural and optical properties. Notably, the bandgap values of the synthesized MXenes were determined as 1.71 eV for Ti₂CT_X, 1.42 eV for Mo₂TiC₂T_X, and 1.07 eV for Mo₂CT_X. The photocatalytic performance of the synthesized MXenes was evaluated, showing a removal efficiency of 65% to 98% for dye mixtures, with methylene blue showing the highest degradation rate. This plasma-assisted method offers a scalable, precursor-free route for the synthesis of MXenes with potential applications in energy storage, environmental remediation, and optoelectronics due to their tunable bandgaps and high catalytic activity. Full article

Traditional emitters used for downhole acoustic detection have limited radiation frequency and energy, making it difficult to transmit high-precision acoustic signals over long distances. This paper presents a plasma emitter in which high-pressure discharge generates a powerful spherical impulse wave with a wide frequency range. First, the discharge characteristics of the plasma needle-plate emitter are analyzed using high-voltage discharge experiments and discharge simulation models for underwater emitters. Subsequently, advanced modifications are made to the structure of the needle–plate emitter to meet the requirements of downhole detection. A new type of hollow needle–plate emitter with a spherical tip is developed. The results show that the structural optimization of the hollow needle–plate emitter with a spherical tip resulted in a 27.2% increase in impulse wave amplitude, a 28.1% improvement in electro-acoustic conversion efficiency, and a radiation frequency band covering up to 100 kHz. This development is conducive to more accurate and longer-range downhole structure detection. The detection range outside the borehole can reach tens to hundreds of meters. This enables the precise control of the wellbore path and reduces the demands on the rig’s build rate. The emitter has significant application potential in areas such as onshore and offshore oil and gas exploration, unconventional resource detection, impulse wave fracturing and wellbore clearance, and rescue and U-well drilling. Full article

A wide range of seed-borne and soil-borne plant pathogens belonging to various fungal and fungal-like species cause pre-emergence seed decay and post-emergence seedling blights of wheat and other small-grain cereal crops. To prevent the death of the seedlings, poor establishment and reduced stand of the crops, extensive crop rotations, planting good-quality seeds and seed treatments with fungicides are used on regular basis. This study is aimed at assessing the efficacy of pre-sowing seed treatments with cold atmospheric plasma for the disinfestation of winter wheat seed from economically important fungal and fungal-like pathogens. Uninoculated or surface-inoculated with Fusarium culmorum, Bipolaris sorokiniana or Pythium ultimum wheat seeds, the cultivar Madara was treated by cold plasma produced either by microwave torch (MW) or underwater diaphragm discharge (UW) with low power at very short treatment times, or remained untreated controls. As per the treatments, the seeds were sown in a ready-to-use growing medium comprising a mixture of light and dark moss peat (w:w) 90–95%, 5–10% perlite and 3–5 kg/m³ CaCO₃, having an electrical conductivity of 40 mS/m, pH (H₂O) of 5.5–6.5 and moisture content of 60–70%, filling in 250 × 250 × 70 mm aluminum flat seed trays (40 grains per tray, four trays per treatment). The plants were cultivated for 45 days in a growth chamber held at (20 ± 2) °C, set to a cycle of 8 h/night and 16 h/day under fluorescent light of 2000–3000 lux intensity. For each replicate, disease incidence (DI) was determined as the total percentage of missing, dead and apparently symptomatic plants. Seed treatment with a microwave plasma torch with a power of 16 W for 40 s significantly (p < 0.001) reduced seedling blights caused by F. culmorum, B. sorokiniana and P. ultimum by 46.8%, 51.0% and 77.3%, respectively, but limited the emergence of wheat seedlings by 15.9% on average. Simultaneously, the effectiveness of underwater discharge seed treatments reached an average of about a 60% reduction of seedling blight caused by F. culmorum and B. sorokiniana and about 37% of the disease caused by P. ultimum. Pre-sowing treatments with a MW plasma torch with an input power of 11 W and treatment time of 60, 90 or 120 s exposure also showed significant (p < 0.001) effects in controlling winter wheat seedling blights caused by the three pathogens. The effectiveness of the treatment increased with increasing the time period of exposure and reached full disease control (>80% reduction) for B. sorokiniana and P. ultimum seedling blights. This study demonstrated that pre-sowing treatment with a microwave plasma torch and underwater diaphragm discharge at a relatively low input power and short exposure time can be used for disinfestation and the effective control of seedling blights in winter wheat caused by seed-borne fungal pathogens, such as Fusarium culmorum and Bipolaris sorokiniana, and fungal-like oomycetes, such as Pythium ultimum. Full article

A composite material based on polyvinyl alcohol (PVA) and brookite-phase titanium dioxide (TiO₂) was synthesized using a straightforward method that involved combining the polymer with a sol as a filler. The composites were analyzed using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), and mechanical testing. The effects of treating the sol with underwater discharge plasma utilizing different electrode materials on the surface morphology, mechanical properties, thermal stability, and optical (photochromic) characteristics of the composites were investigated. FTIR spectral analysis indicated the presence of a chemical bond between the polymer matrix and the filler particles, as evidenced by the appearance of new peaks in the region of 700–500 cm⁻¹. Preliminary plasma treatment was shown to enhance the thermal stability, strength, and elasticity of the PVA-based composite. These improvements resulted from the modification of the filler (sol) due to plasma activity. The resulting composites exhibited a low photocolorization rate and a high bleaching rate. Such composites represent a promising material for use as inks in 3D printing. Full article

Plasma technology, relatively new in the fields of biomedicine, agriculture, and ecology, is the subject of intensive research as a prospective means of decontamination of various microorganisms (bacteria, viruses, and fungi). The objectives of the present study were to follow the effect of cold atmospheric plasma (CAP) treatment on in vitro grown plum plants (Prunus domestica L. ‘Kyustendilska sinya’ cv.) and the possibility of eradicating or inactivating plum pox virus (PPV) causing Sharka disease by CAP. The source tree is naturally co-infected by PPV (both M and D strains). In the experiments, two different plasma sources were used. First, a surface-wave-sustained Argon plasma torch and second, an underwater diaphragm discharge. For the treatments, nodal segments (10 mm in length) from in vitro cultured plum plants with or without one leaf were prepared. Apical shoots from treated plants (PPV-positive and negative clones as well non-treated controls) were cultivated in vitro for four passages. Then they were rooted and acclimatized to ex vitro conditions, and their virus status was observed periodically for more than 3 years after treatment for the appearance of Sharka symptoms. All plants, acclimatized to ex vitro conditions, were tested for PPV by immune capture–reverse transcription–polymerase chain reaction (IC-RT-PCR). As a first step in understanding the plasma treatment of living plants, a plasma treatment variant causing no damage must be established; this has been done in our previous works. Treatment of plants by plasma with parameters that have been carefully selected leads to better development than the non-treated plants. In the treated in vitro plants, no significant differences were found in the number and length of shoots compared to the control plantlets. In ex vitro acclimated plants, greater stem length was reported, but no differences in leaf number were observed. No significant differences in growth were recorded between the control and plants that were treated twice or three times. At this stage, 3 years after ex vitro cultivation in a greenhouse, Sharka symptoms were not registered on treated in vitro negative PPV plants, and the virus was not detected by IC-RT-PCR. Very mild symptoms were showing in CAP-treated PPV-positive plants. Development of typical Sharka symptoms on non-treated controls were observed. Full article

Cold atmospheric pressure plasma (CAP) has attracted increased interest in recent years for possible biomedical, environmental and agricultural applications. A wide range of cold plasma treatment effects is observed in agricultural applications, like effects on the seed germination and seedling growth, but more systematic investigations are needed. The aim of this study was to identify the most appropriate combinations of the plasma source and duration of treatment positively affecting seed germination. In addition, the effect of cold plasma on the seedling growth and osmotic stress tolerance was studied. The seeds of three Bulgarian durum wheat cultivars were treated with cold plasma in twelve variants. The results obtained were processed statistically via two-way ANOVA. The treatment of seeds with a plasma torch for 20 s and the treatment with underwater diaphragm discharge for 5 min when the seeds were placed in both cameras in two different positions (relative to the electrodes between which the plasma is supplied, “+” and “−”) have the greatest positive effect on the all traits related to germination. The analysis of variance reveals that the variation in germination energy, shoot length and root length after the cold plasma treatment of seeds is mainly due to the interaction between the genotype and treatment variant and to a small degree due to the genotype. The treatment of seeds with cold plasma improves the osmoregulation ability of cells and therefore increases the drought resistance of genotypes. Full article

Foliar fertilizing is very important to supply apple plants with calcium and micronutrients. The most cost-effective approach to this is the application of the fertilizers in tank mixtures with plant protection chemicals. Plasma-activated water (PAW) has great potential for the use in the agriculture. We used two type of PAWs, PAW1 (made using underwater electrical discharge in an aqueous KNO₃ solution and includes reactive nitrogen species and platinum nanoparticles) and PAW2 (made using a plasma torch with nitrogen gas makeup and contains reactive nitrogen species but not metals). We studied the impact of two PAW types on the contents of Ca, B, Mn, Fe, and Co in leaves and Ca, Mn, Fe, Zn, and Mo in fruits sprayed with tank mixtures containing the fertilizers. We also tested the efficiency of PAW in the control of apple scab when applied as tank mixtures with plant protection chemicals. The application of the PAWs significantly increased foliar Ca when the PAW was mixed with Ca-containing formulations (spraying PAW1 containing Ca increased leaf Ca by up to 21%, and PAW2 up by to 9% compared to Ca spraying without PAW). The largest fruit Ca increase was in the variant treated with PAW1 with a micronutrient spraying program (up to 143%). The PAW treatments enhanced the baseline mineral contents of the plants even when they were not sprayed with the nutrients. PAW1 mainly increased the nutrient contents of the apple fruits. PAWs have proven to be efficient for the control of apple scab, thereby reducing the demand for fungicides. The scab damage to the leaves and fruits was similar in plants treated with PAWs without fungicides (1.7–1.9% on the leaves and 1.6–1.8% on the fruits) compared to the conventional chemical scab control (0.9% leaves and 0.6% fruits) and was significantly lower than in the untreated control (9.3% on leaves and 11.9 on fruits). Full article

Impulsive underwater discharges have been investigated for many decades, yet the complex pre-breakdown processes that underpin their development are not fully understood. Higher pre-breakdown energy losses may lead to significant reduction in the magnitude and intensity of the pressure waves generated by expanding post-breakdown plasma channels. Thus, it is important to characterize these losses for different discharge types and to identify approaches to their reduction. The present paper analyses thermal pre-breakdown processes in the case of free path and wire-guided discharges in water: fast joule heating of a small volume of water at the high-voltage electrode and joule heating and the melting of the wire, respectively. The energy required for joule heating of the water and metallic wire have been obtained from thermal models, analysed and compared with the experimental pre-breakdown energy losses. Pressure impulses generated by free path and by wire-guided underwater discharges have also been investigated. It was shown that wire-guided discharges support the formation of longer plasma channels better than free path underwater discharges for the same energy available per discharge. This results in stronger pressure impulses developed by underwater wire-guided discharges. It has been shown that the pressure magnitude in the case of both discharge types is inversely proportional to the observation distance which is a characteristic of a spherical acoustic wave. Full article

Plasma-activated tap water (PATW) is a new technology for obtaining a high concentration of active aqueous plasma substances by discharging underwater. Commonly plasma-activated water (PAW) is realized by activating deionized water or distilled water, which has problems such as high cost, a small discharge area, and insufficient dissolution of active substances. This paper reports the development of a dielectric barrier discharge array to generate a high concentration of active aqueous plasma substances. The device can realize a uniform, stable, and large-area discharge in a large volume of tap water, and it has the advantages of low cost, high integration, and reusability. Using the device to treat 1000 mL of tap water for 1 h can reduce the pH of the tap water from 8.10 to 2.54, and the logarithmic value of killing E. coli is greater than 5.0. We sprayed PATW onto clothes to sterilize the bacteria when people were through the disinfection door and verified that the PATW had a good sterilization effect. The short-lived substances, singlet oxygen, and superoxide anion radicals played a key role in the sterilization process by PATW. Full article

In our previous study, a novel method combining underwater high-voltage plasma discharge with acoustic cavitation (ACAP) was developed and implemented using rhodamine B (RhB) as a model organic pollutant. Results revealed that injecting argon gas into the ACAP reactor positively influences RhB decomposition efficiency, but there is still further potential for improvement. The aim of this study was therefore to further improve the efficiency of the ACAP process through Fenton reactions. Two options for ferrous ion supply were considered: the addition of FeCl₂ or the dissolution of iron from ACAP reactor steel parts into the RhB-containing solution. The results revealed that the degradation efficiency is increased by 20% due to the Fenton reactions when the concentration of ferrous ions reaches an optimal value. Lower pH was found to be desirable for the effect of Fenton reactions. Based on measurements using high performance liquid chromatography, a plausible mechanism of RhB degradation by the ACAP process assisted by Fenton reactions is additionally proposed and discussed. Full article

This paper presents a detailed analysis of underwater electrical discharge parameters in the treatment of chromium (VI) used as a model pollutant to analyze the reduction process by plasma liquid interaction (PLI). Pin-to-pin microsecond discharges were performed in an aqueous Cr(VI) solution and the processes were characterized using electrical measurements, optical imaging and UV-Vis absorption measurements for [Cr(VI)] estimation. For the first time, the total reduction of Cr(VI) was successfully achieved by PLI process and a maximum energy yield of 4.7 × 10⁻⁴ g/kJ was obtained. Parametric studies on electrode geometry, applied voltage, electrodes gap and pulse duration are presented in detail. Finally, an analysis of the process is proposed by comparing our results of the energy yield calculation based on the injected energy with those of the literature and by providing an estimation of the global energy efficiency of the process. Full article

This paper is aimed at the investigation of the acoustic and spectral characteristics of underwater electric sparks generated between two plate electrodes, using synchronized gas bubble injection. There are two purposes served by discharge initiation in the bubble. Firstly, it creates a favorable condition for electrical breakdown. Secondly, the gas bubble provides an opportunity for the direct spectroscopy of plasma light emission, avoiding water absorption. The effect of water absorption on captured spectra was studied. It was observed that the emission intensity of the H_a line and a shockwave amplitude generated by discharge strongly depend on the size of the gas bubble in the moment of the discharge initiation. It was found that the plasma in the underwater spark channel does not correspond to a source of black-body radiation. This study can be also very useful for understanding the difference between discharges produced directly in a liquid and discharges produced in gas/vapor bubbles surrounded by a liquid. Full article

Underwater plasma discharge temporally produces several reactive radicals and/or free chlorine molecules in water, which is responsible for antimicrobial activity. Hence, it can simply sanitize tap water without disinfectant treatment. Additionally, the spraying technique using cleaning water exploits deep application in the narrow and curved vaginal tract of patients. Herein, we attempted a clinical trial to evaluate the vaginal cleaning effect of spraying plasma-activated water (PAW) to patients with vaginitis (46 patients). The efficacy was compared with treatment with betadine antiseptics used to treat bacterial vaginosis (40 patients). To evaluate the cleaning effect, Gram staining of the vaginal secretions was conducted before and after spraying PAW or betadine treatment (BT). Consequently, PAW-sprayed (PAWS) patients (22.3%) showed a better vaginal cleaning effect against Gram-positive and -negative bacteria than BT patients (14.4%). Moreover, 18 patients in the BT group showed worsened vaginal contamination, whereas five patients in the PAWS group showed worsened vaginal contamination. Taken together, the noncontact method of spraying cleaning water to the vagina exhibited a reliable vaginal cleaning effect without further bacterial infection compared with BT. Therefore, we suggest a clinical application of the spraying method using PAW for vaginal cleaning to patients with vaginitis without disinfectants and antibiotics. Full article