Microplasma Treatment Research Articles

Size‐Dependent Optical Properties and Exciton Self‐Trapping Emission in Carbon Quantum Dots

AbstractCarbon quantum dots (CQDs), synthesized through controlled microplasma treatment of orange juice, exhibit unique luminescent characteristics. The impact of synthesis time on particle size was investigated. Deconvoluted emission spectra displayed broad bands, peaking at an excitation wavelength of 350 nm for CQD sizes of 2.06, 2.4, and 3.09 nm, indicating multiple fluorescence peaks. This suggests a mixture of CQDs with different excitation energies on their surfaces. Luminescence kinetics unveiled three exponential decay components with time constants of 2.73, 4.61, and 3.27 ns, indicating multiple luminescent centers. Emission behavior affected by excitation wavelengths ranging from 350 to 490 nm suggests that quantum transition probabilities are influenced by impurities or defects. These findings emphasize the size‐dependent optical properties and exciton self‐trapping (EST) emission of CQDs. The calculation of the Huang‐Rhys factor S values underscores the profound influence of carrier‐phonon coupling and the Huang‐Rhys factor on the emergence of ESTs within CQDs. Understanding these interactions is crucial for fully utilizing the capabilities of CQDs in applications spanning optoelectronics, sensors, bioimaging, and various technological fields.

Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium toruloides.

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 × 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides. Specifically, a compact-sized microplasma channel (25 × 20 × 2 mm3) capable of generating an electron density of greater than 1013 cm-3 was constructed to produce reactive species (N2*, N2+, O, OH, and Hα) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. This compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.

Detection of micro-plasma-induced exosomes secretion in a fibroblast-melanoma co-culture model

BackgroundMelanoma is a highly aggressive tumor and a significant cause of skin cancer-related death. Timely diagnosis and treatment require identification of specific biomarkers in exosomes secreted by melanoma cells. In this study, label-free surface-enhanced Raman spectroscopy (SERS) method with size-matched selectivity was used to detect membrane proteins in exosomes released from a stimulated environment of fibroblasts (L929) co-cultured with melanoma cells (B16–F10). To promote normal secretion of exosomes, micro-plasma treatment was used to gently induce the co-cultured cells and slightly increase the stress level around the cells for subsequent detection using the SERS method. Results and discussionFirstly, changes in reactive oxygen species/reactive nitrogen species (ROS/RNS) concentrations in the cellular microenvironment and the viability and proliferation of healthy cells are assessed. Results showed that micro-plasma treatment increased extracellular ROS/RNS levels while modestly reducing cell proliferation without significantly affecting cell survival. Secondly, the particle size of secreted exosomes isolated from the culture medium of L929, B16–F10, and co-cultured cells with different micro-plasma treatment time did not increase significantly under single-cell conditions at short treatment time but might be changed under co-culture condition or longer treatment time. Third, for SERS signals related to membrane protein biomarkers, exosome markers CD9, CD63, and CD81 can be assigned to significant Raman shifts in the range of 943–1030 and 1304-1561 cm-1, while the characteristics SERS peaks of L929 and B16–F10 cells are most likely located at 1394/1404, 1271 and 1592 cm-1 respectively. Significance and noveltyTherefore, this micro-plasma-induced co-culture model provides a promising preclinical approach to understand the diagnostic potential of exosomes secreted by cutaneous melanoma/fibroblasts. Furthermore, the label-free SERS method with size-matched selectivity provides a novel approach to screen biomarkers in exosomes secreted by melanoma cells, aiming to reduce the use of labeling reagents and the processing time traditionally required.

Accelerated degradation of 4-nitrophenol using microplasma discharge: Processes and mechanisms

In this work, an atmospheric microplasma reactor has been constructed to evaluate, the influence of microplasma forming gases (air, oxygen, nitrogen, and argon) on 4-nitrophenol (4NP) degradation and mineralization efficiency as a function of treatment time. 92 % of 4NP in solution was degraded by air microplasma after 7 min, which was higher than nitrogen, oxygen, and argon microplasma treatments. The air microplasma treatment achieved a consistent mineralization percentage of 57 %. With the addition of hydroxyl radical scavenger during the treatment, irrespective of the gas medium, the degradation percentage got reduced; for air, it was 76 % reduced compared to without scavenger. This implies that the hydroxyl radical is primarily responsible for the degradation of 4NP. The amount of hydrogen peroxide produced during the treatment was measured, and its role in 4NP degradation was examined. A density functional theory calculation was carried out to identify reactive sites on the 4NP molecule. 4NP intermediates, including hydroquinone and benzoquinone, were identified using liquid chromatography-mass spectrometry, and a 4NP degradation pathway was proposed based on the detected intermediates. The phytotoxicity of plasma mineralized 4NP aqueous solution was analyzed by mung bean seed germination, and the results reveal that plasma treated 4NP aqueous solution has 11.5 % of higher germination percentage than untreated 4NP.

Atmospheric Microplasma Treatment Based on Magnetically Controlled Fe–Al Dynamic Platform for Organic and Biomaterials Surface Modification

By exploiting the physical effect of the electron emission from a thermionic source in combination with a magnetically controlled Fe–Al dynamic platform to assist electrical discharge, we generated atmospheric microplasma (AM). The electrical characteristics of microplasma discharge-induced cold atmospheric plasma in combination with a magnetically controlled Fe–Al dynamic platform in open air were evaluated. The surface analysis of organic wheat seeds was investigated at two steps: (1) the coating effect of an Al nanoparticle with an electrons drift toward the seed surface along the direction of an electric field and (2) inelastic collision with secondary electrons moving from the cathode in the presence of an electric field. Using SEM microscopy analysis, it was found that plasma affects seed surface topography and apparent contact angle (ACA). The effect of atmospheric microplasma treatment leads to seed surface modification by the manifestation of fine mesh structures on the seed surface. Well-established AM technology will garner interest in agriculture and biomaterials coatings applications.

Transdermal administration of adenosine using microplasma and the examination of the effect of microplasma on stratum corneum using infrared spectroscopy

The strong barrier established by stratum corneum serves a protective purpose. It also prevents pharmacological compounds from being delivered via the epidermal layer. Microplasma discharge was used to overcome the barrier of epidermal layer to permeate adenosine. Depth of the microplasma effect into the stratum corneum layer was evaluated using tape striping method and attenuated total reflectance-Fourier transform IR spectroscopy (ATR-FTIR). Microplasma treatment caused increased permeability of stratum corneum lipids to a depth of several micrometers. The possible interaction between microplasma and stratum corneum lipids was studied on ceramide C4 by ATR-FTIR. Microplasma particles dominantly interacted with ceramide C4 at the bond between the NH and C=O causing possible dissociation and weakening of hydrogen bonding between molecules.

Extension of Raw Cow Milk Shelf Life by Microplasma Discharge

Cow's milk, the universal nutrient, is being stored and supplied, which seeks proper preservation. The prevalent milk preservation procedure of refrigeration, is effective only for two days, and after which, it starts to contaminate due to the growth of various milk-laden bacteria. This bacterial overload has to be inactivated properly to increase its shelf life, and is been achieved effectively using microplasma, a single-step, cost-effective and chemical-free process. Raw milk was treated for 5, 10, and 13 seconds in microplasma discharge. After 13 seconds of microplasma treatment, E. Coli, Pseudomonas, and S. Aureus bacteria got reduced at a respective rate of 89.93, 84.55, and 94.19% for in raw milk. The reactive species formed during microplasma discharge disrupts the structural integrity of bacterial cells and inactivates it, thereby enhancing the milk shelf life. Treated samples remained in good condition for 8 days. Thus, microplasma discharge increases the shelf life of milk by quickly inactivating the bacterial load.

Construction of hydrophobic-hydrophilic microfluidic patterns with controlled wettability on PVDF filter paper surface using maskless microplasma scanning

Paper-based microfluidic analytical devices (μPADs) have attracted increasing interest due to their unique advantages. Localized hydrophilization on hydrophobic paper surfaces to form the microfluidic patterns and their wettability control are the key issues in μPADs preparation. This paper introduces a novel method to construct hydrophobic-hydrophilic microfluidic patterns on the surface of the Poly(vinylidene fluoride) (PVDF) filter paper by maskless microplasma writing. The hydrophilic performances and surface morphology of the patterns were characterized by water contact angle (WCA) and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze their chemical compositions. The results showed that paper surface changed from hydrophobic to hydrophilic and its wettability can be controlled through plasma parameters adjustment. PVDF layer was gradually removed from the filter paper and the fluorine-containing groups on paper surface of the micropatterns decreased with increasing microplasma treatment time. Besides, the polar functional groups (e.g. –C=O) also appeared and increased with longer treatment time. Finally, the mechanism of the microfluidic patterns construction by microplasma was discussed, and the microfluidic pattern with the pattern “H” were demonstrated and successfully constructed. This work shows great potential for simple, fast, environmental friendly and low-cost construction of μPADs.

Luminescent properties of carbon quantum dots synthesized by microplasma method

The luminescent carbon quantum dots were synthesized by microplasma treatment of a glucose solution at atmospheric pressure at room temperature. The spectral and kinetic characteristics of synthesized quantum dots were studied by time-resolved confocal scanning luminescent microscopy and time-correlated single photon counting. The emission spectra are wide non-elementary bands. Their maxima were located at 476, 500, 547 and 580 nm at the wavelengths of the exciting radiation of 375, 405, 470 and 532 nm, respectively. Three exponential components with decay time constants of 0.65, 2.2, and 6.2 ns were detected in the luminescence kinetics. The presence of these components is due to the formation of three different types of luminescence centers at quantum dots with different probabilities of quantum transitions. Presumably, it may be related to the activation of quantum dots by various impurities or other defects formed luminescence centers. The concentration of quantum dots was controlled by changing the microplasma processing time of the glucose solution.

Chemical warfare agents decontamination via air mircoplasma excited by a triboelectric nanogenerator

Low-temperature air plasma, as an emerging green and efficient technology, has great potential to do chemical warfare agents (CWAs) decontamination. However, conventional plasma devices are bulky, costly and inconvenient. More importantly, their practical application is limited by the power grid and battery capacity. Here, A double layer paper-strip rotary triboelectric nanogenerator (dps-rTENG) is fabricated to serve as a self-powered high-voltage device to induce microplasma in air for CWAs decontamination. The degradation efficiency of 2-chloroethylethyl sulfide (2-CEES), a surrogate for the sulfur mustard (HD), reaches more than 99% within 2 min of microplasma treatment, and the energy utilization efficiency (Ee) of the dps-rTENG is calculated to be 0.520 μg/J, which is one order of magnitude higher than those of the commercial power supplies. Further study confirms that the degradation process of the dps-rTENG induced microplasma is well controllable to avoid the formation of large amounts of 2-chloroethyl ethyl sulfone (2-CEESO2), a toxic excessive oxidation product. Triboelectric microplasma provides a new approach for self-powered, easily portable decontamination system for CWAs in future.

Innovative non-thermal plasma coating for “core–shell” CaCu3Ti4O12 material

Colossal permittivity of CaCu3Ti4O12 (CCTO) makes it a very interesting candidate for capacitor applications. To improve its properties, an innovative physical method based on a pulsed non-thermal micro-plasma treatment was set up to realize the coating of CCTO's grains (core) with silicon oxide (shell). This method is adapted to control the thickness and homogeneity of the shell, which will allow a better control of grain–grain boundary interfaces and improve the properties of this material. Best result is obtained for the set of gas mixture: Ar/O2/hexamethyldisiloxane (HMDSO) = 2028 N cm3 min−1/7.84 N cm3 min−1/523 mg h−1, respectively, in plasma with a shell thickness of 50 nm. This study offers a new opportunity to quickly synthetize core–shell materials with a dry technique and without almost no secondary product resulting from the chemical reaction because it is in the gaseous state. A complete analysis of the plasma by optical emission spectroscopy in the UV-visible range shows that HMDSO molecules are totally dissociated in atomic (Si, C, and O) or simple radical species (C2 and CH) in the plasma phase. In addition, several thermometer species (OH°, CH, CN, N2, and N2+) are used to estimate excitation temperatures of the plasma (Trot, Tvib, and Te = 300 K, 2400–3700 K, and 5.3 eV, respectively) that clearly shows the non-equilibrium character and the efficiency of this plasma.

Research stand for microplasma surface treatment of materials at atmospheric pressure

A research stand for microplasma treatment of object surfaces with the ability to move the discharge zone along the object using a program-controlled linear stepper motor has been developed. The design of the stand allows the use of different types of plasma generation systems, as well as processing with feeding of various gases such as air, nitrogen, oxygen, etc. into the discharge zone. The research bench is equipped with measuring equipment for monitoring the electrical and physical characteristics of the discharge (digital oscilloscopes, optical emission spectrometer, air ion meter, etc.). A microhardness tester, goniometer, interference microscope, tribometer, tensile testing machine, etc. can be used to further evaluate the quality and characteristics of the treated surfaces. Examples of the electrical characteristics of discharge devices tested as part of the research stand, optical emission spectroscopy of plasma, and results of measurements of the contact angle of treated objects surfaces are given.

Cell membranes of plant materials anatomical integrity changes under the influence of filamentary microplasma treatment assisted by thermionic emission

The effect of low-temperature filamentary microplasma treatment on the anatomi-cal integrity of cell membranes of plant raw materials was studied. It is shown that microplasma treatment forms a through channels in the structure of plant materi-als and accelerate mass transfer process. The effect on the cell membrane of plant raw materials leads to a change in the capillary-porous structure with the for-mation of additional pores formed by microplasma discharge, oriented along the direction of the electric field strength. It was found that the dependence of the number of destroyed cells on the intensity of microplasma treatment is limited and decreases with longer processing of plant raw materials. According to the results of experimental studies, it was established that with microplasma treatment assis-tant, it is possible to control mass transfer processes which are important for the further processing of plant raw materials, such as drying and extraction

Inactivation and sensitization of Pseudomonas aeruginosa by microplasma jet array for treating otitis media

Otitis media (OM), known as a middle ear infection, is the leading cause of antibiotic prescriptions for children. With wide-spread use of antibiotics in OM, resistance to antibiotics continues to decrease the efficacy of the treatment. Furthermore, as the presence of a middle ear biofilm has contributed to this reduced susceptibility to antimicrobials, effective interventions are necessary. A miniaturized 3D-printed microplasma jet array has been developed to inactivate Pseudomonas aeruginosa, a common bacterial strain associated with OM. The experiments demonstrate the disruption of planktonic and biofilm P. aeruginosa by long-lived molecular species generated by microplasma, as well as the synergy of combining microplasma treatment with antibiotic therapy. In addition, a middle ear phantom model was developed with an excised rat eardrum to investigate the antimicrobial effects of microplasma on bacteria located behind the eardrum, as in a patient-relevant setup. These results suggest the potential for microplasma as a new treatment paradigm for OM.

Degradation of Methylene Blue Using Microplasma Discharge – A Relative Study with Photodegradation

Large-scale production and application of synthetic dyes have become a matter of concern as it is a major factor responsible for environmental pollution. Most dyeing effluents are discharged into water bodies and lands without being treated, which ultimately pollutes the groundwater making it unfit for consumption. The present study explains the degradation of one of such synthetic dyes Methylene blue (MB), using non-thermal Microplasma treatment. The aqueous solution of MB was treated with an array of air microplasma discharge at atmospheric pressure. Different concentrations (10 ppm, 20 ppm) of MB solution were treated for various treatment time and chemical parameters like pH, electrical conductivity, total dissolved solids and salinity was measured. The degradation percentage reached 100% in 15 min of treatment for 10 ppm MB solution, and 20 min of treatment for 20 ppm MB solution indicated by the color change from blue to a clear solution. The reactive oxygen species (ROS) and reactive nitrogen species (RNS) formed during the microplasma treatment are responsible for MB degradation. Same volume of MB solution was irradiated by direct sunlight for photodegradation and was found to degrade the solution of 10 ppm by 96% and 20 ppm by 93% in 10 hours of treatment. Experimental results indicated that microplasma treatment was effective for dye degradation, without the need for pretreatment process or chemicals.

Direct and Indirect Bactericidal Effects of Cold Atmospheric-Pressure Microplasma and Plasma Jet.

The direct and indirect bactericidal effects of dielectric barrier discharge (DBD) cold atmospheric-pressure microplasma in an air and plasma jet generated in an argon-oxygen gas mixture was investigated on Staphylococcus aureus and Cutibacterium acnes. An AC power supply was used to generate plasma at relatively low discharge voltages (0.9–2.4 kV) and frequency (27–30 kHz). Cultured bacteria were cultivated at a serial dilution of 10−5, then exposed to direct microplasma treatment and indirect treatment through plasma-activated water (PAW). The obtained results revealed that these methods of bacterial inactivation showed a 2 and 1 log reduction in the number of survived CFU/mL with direct treatment being the most effective means of treatment at just 3 min using air. UV–Vis spectroscopy confirmed that an increase in treatment time at 1.2% O2, 98.8% Ar caused a decrease in O2 concentration in the water as well as a decrease in absorbance of the peaks at 210 nm, which are attributed NO2− and NO3− concentration in the water, termed denitratification and denitritification in the treated water, respectively.

In-site and solvent-free exfoliation of porous graphene oxide from pencil lead fiber for solid-phase microextraction of cadmium ion before GF-AAS determination.

Graphene oxide (GO)-functionalized pencil lead fiber was prepared for the first timeby in situ oxidation and exfoliation of graphite contained in pencil lead fiber to porous graphene oxide structure via a one-step solvent-free dielectric barrier discharge (DBD) microplasma treatment. This new fiber was demonstrated as a highly efficient and low-cost solid-phase microextraction (SPME) fiber for the determination of toxic metal ions. The fiber extraction performance was evaluated by using cadmium as a model analyte in a direct immersing SPME mode. Unlike mostcommercially available and other lab-built fibers, the preparation of the graphene oxidized pencil lead fiber is environmentally friendly, low cost, and non-toxic without using any organic solvents. The fiber is robust due to its coating-free configuration. Furthermore, high extraction efficiency and high sensitivity for cadmium can be obtained due to the abundant oxygen-containing functional groups on the surface of the novel fiber. After extraction, the cadmium adsorbed on the fiber was desorbed to 150-μL solution. Graphite furnace atomic absorption spectrometry (GF-AAS) with low sample consumption was used to determine cadmium. The calibration curve for cadmium ions was linear in a range 0.04-0.26μgL-1 with a detection limit of 0.005μgL-1. A relative standard deviation (RSD, n = 5) of 2.1% was obtained at 0.1μgL-1 of cadmium. The sensitivity enhancement factor (EF) value of the proposed SPME method was 25. The SPME fiber was successfully applied to determinecadmium in tap water, river water, and pond water with spike recoveries ranging from 94 to 105%. Pipe network water samples were also analyzed to evaluate the cadmium release to drinking water due to the corrosion of tubes.

Микроплазменная обработка для сушки табачных листьев

Микроплазменная обработка для сушки табачных листьев

Synthesis of Nanostructured Nonmetallic Inorganic Coatings at High Energy Localization in Interfacial Nanolayers

The paper presents the mathematical model of the microplasma process in an electrolyte solution and the main equation of the nanostructured nonmetallic inorganic coating growth during the coating formation on the material surface under conditions of the high energy localization in interfacial nanolayers. The microplasma process is considered as a microplasma collective discharge. The proposed physicochemical model links the main parameters of electrochemical and microplasma processes (concentration, temperature, polarization voltage, pulse duration, time of microplasma treatment) in electrolyte solutions with the parameters of the coating synthesis (growth rate, thickness, grain size). The total microplasma discharge current is limited by the current passing through the nonmixed interlayer.

Relative Potential of Different Plasma Forming Gases in Degradation of Rhodamine B Dye by Microplasma Treatment and Evaluation of Reuse Prospectus for Treated Water as Liquid Fertilizer

Degradation of Rhodamine B in aqueous solution was carried out with different microplasma medium generated from air, oxygen, nitrogen and argon gases at atmospheric pressure. Rhodamine B (RhB) aqueous solution was prepared (10 ppm) and treated in microplasma reactor at different treatment time and applied potential. The RhB degradation was mainly due to the hydroxyl radical formation, during the plasma treatment, which was identified by terephthalic acid probe method. The result shows that the oxygen microplasma produced more hydroxyl radicals than air, nitrogen and argon. The degradation percentage of RhB solution with respect to different plasma gases were estimated by using UV–Vis absorption spectra which reveals that the oxygen microplasma is most competent for complete degradation within petite time followed by air, nitrogen and argon. Post discharge phenomenon was observed in air and nitrogen microplasma treated solution, which could reduce the treatment time to accomplish complete dye degradation. The sample treated with air and nitrogen microplasma for 3 min resulted in the degradation percentage of 62.3% and 60.4%, respectively, and the complete degradation was obtained after 7 and 10 h of post discharge, respectively. Further an attempt was made to verify the reusability of air microplasma treated solution as a liquid fertilizer in cultivation purpose using Mung bean (Vignaradiata). The obtained results were encouraging as the treated water enhanced the seed germination and plant growth notably.