Multifunctional bimetallic MOF with oxygen vacancy synthesized by microplasma for rapid total antioxidant capacity assessment in agricultural products

The assessment of total antioxidant capacity (TAC) is crucial for evaluating overall antioxidant potential, predicting the risk of chronic diseases, guiding dietary and nutritional interventions, and studying the effectiveness of antioxidants. However, achieving rapid TAC assessment with high sensitivity and stability remains a challenge. In this study, Ce/Fe-MOF with abundant oxygen vacancies was synthesized using microplasma for TAC determination. The microplasma synthesis method was rapid (30 min) and cost-effective. The presence of oxygen vacancies and the collaboration between iron and cerium in Ce/Fe-MOF not only enhanced the catalyst's efficiency but also conferred multiple enzyme-like properties: peroxidase-like, oxidase-like, and superoxide dismutase mimetic activities. Consequently, a simple colorimetric assay was established for TAC determination in vegetables and fruits, featuring a short analysis time of 15 min, a good linear range of 5-60 μM, a low detection limit of 1.3 μM and a good recovery of 91 %-107 %. This method holds promise for rapid TAC assessment in agricultural products.

Microplasma and quenching-induced Co doped NiMoO(4) nanorods with oxygen vacancies for electrochemical determination of glucose in food and serum

In this paper, Co-doped NiMoO₄ nanorods with oxygen vacancies are synthesized on carbon cloth (Co-NiMoO₄ NRs/CC) via microplasma and quenching-induced method.Owing to the surface defects and metal ion doping, the electronic structure and surface properties of the catalyst are tuned.Cyclic voltammetry (CV) and amperometry are used to investigate the electrocatalytic behavior of the glucose sensor in an alkaline medium with sensitivities of 7411 and 3125 μA L mmol^-1 cm^-2 in the linear range 1.0 μmol L^-1 to 1.0 mmol L^-1 and 1.0 mmol L^-1 to 7.0 mmol L^-1, respectively. The detection limit is 0.079 μmol L^-1 at S/N = 3. Moreover, the as-prepared catalyst electrode is also successfully used in real food and serum samples, with a recovery rate of 97.1%-107.4%.The DFT calculations show that the Co site of the catalyst significantly influenced glucose sensing performance. This idea expands the application of quenching chemistry in electrochemical sensing.

Radiation modeling of microplasma UV lamps for design analysis and optimization

Microplasma UV lamps have recently emerged as viable excimer-based sources of UV radiation, garnering significant attention during the recent COVID-19 pandemic for their use in disinfection applications because of their ability to emit human-safe far-UVC (200-240 nm) spectrums. An accurate model to simulate the radiation profile of microplasma UV lamps is of paramount importance to develop efficient microplasma lamp-implemented systems. We developed a 3D numerical model of microplasma UV lamps using the ray optics method. The simulation results for lamp irradiance and fluence rate were experimentally validated with standard optical radiometry and actinometry measurements, respectively. To improve the optical efficiency of microplasma lamps, an in-depth analysis of radiation behavior inside the standard commercially available lamp was performed using the geometrical optics method, and several potential scenarios were explored. A 2D modeling of an individual microcavity indicated that the current common lamp design can be significantly improved by preventing radiation loss, and small modifications in optical design can greatly increase the energy performance of the system. Based on the findings of this study, several virtual design concepts were proposed, and their performances were numerically compared with that of the original design of commercial microplasma lamps. The developed model can potentially be integrated with hydrodynamic and kinetic models for the virtual prototyping of complex photoreactors operating with UV microplasma lamps.

A microplasma optical emission spectrometry pen for point-of-care diagnosis of child blood lead

Blood lead levels (BLL) of children have attracted considerable attention due to their putative impact on intelligence decline. However, most methods used for the determination of blood lead typically require expensive, bulky, high power and gas consuming instrumentation, limiting their application for a point-of-care diagnosis. Herein we report the development and testing of a portable ballpoint discharge microplasma optical emission spectrometer (BD-OES pen) device having the potential to fill this needed measurement capability. The BD-OES pen utilizes a compact ballpoint-pen format integrating point-discharge microplasma, which permits the determination of child BLL requiring no more than 100 μL blood while providing high specificity, sensitivity and satisfactory limit of detection (0.73 μg L^-1). The handheld BD-OES pen is successfully used to diagnose BLL of 16 asymptomatic children on-site, two of whom had excessive the normal BLL. The pen may aid the on-site and rapid diagnosis of childhood BLL, particularly in low-income areas.

Determination of Ag, Bi, Cd, Hg, Pb, Tl, and Zn by inductively coupled plasma mass spectrometry combined with vapor generation assisted by solution anode glow discharge - A preliminary study

A new technique of vapor generation assisted by a microplasma was proposed for an inductively coupled plasma mass spectrometry (ICP MS). It was found that, by replacing a traditional pneumatic nebulizer with a microplasma (solution anode glow discharge, SAGD), analytical signals of Ag, Bi, Cd, Hg, Pb, Tl, and Zn were improved 8, 4, 13, 13, 9, 10, and 7 times, respectively. The main factor contributing to boosted analytical signal intensities was the higher analyte flux produced by the novel microplasma system. The measurement precision in SAGD-ICP MS was comparable to that achievable for ICP MS (with pneumatic nebulization), and it did not exceed 2%. The detection limits of Ag, Bi, Cd, Hg, Pb, Tl, and Zn in SAGD-ICP MS were 5, 2, 6, 5, 4, 10, and 20 ng L^-1, respectively. The analytical performance of this method may be further improved if the observed memory effects could be minimized. To validate the trueness of the novel method, certified reference materials of lobster hepatopancreas (TORT-2), cormorant tissue (MODAS-4), and wastewater (ERM CA-713) were analyzed to determine traces of Cd, Hg, and Pb. Recoveries of certified values for these analytes were ranged from 91 to 111%, which indicated that the studied microplasma system in combination with ICP MS can be successfully used for very sensitive determinations of selected hazardous elements in environmental samples.

Direct analysis of wines from the province of Lower Silesia (Poland) by microplasma source optical emission spectrometry

New microplasma source optical emission spectrometry (OES) for the determination of Na, K, Mg, Ca, and Zn in wine was developed. As the microplasma source, a solution anode glow discharge (SAGD) or a solution cathode glow discharge (SCGD) were employed. The diluted samples solutions (0.5-2%) were directly analyzed (no acid digestion required) and the detection limits of Na, K, Mg, Ca, and Zn were 0.015, 0.03, 3, 12, and 0.1 µg L^-1, respectively. The developed method was used for the analysis of wine samples from the province of Lower Silesia (Poland). It was found that 1) red wines were characterized by a higher content of K and Mg, 2) it was possible to discriminate between Regent and Pinot Noir grape varieties (both red) by the concentrations of K and Ca, 3) the concentration of Na in the analyzed wines was lower than that found in wines from other European countries.

Interpreting convolutional neural network for real-time volatile organic compounds detection and classification using optical emission spectroscopy of plasma

This study presents the investigation of optical emission spectroscopy of plasma using interpretable convolutional neural network (CNN) for real-time volatile organic compounds (VOCs) classification. A microplasma-generation platform was developed to efficiently collect 64 k spectra from various types of VOCs at different concentrations, as training and testing sets for machine learning. A CNN model was trained to classify VOCs with accuracy of 99.9%. To interpret the CNN model and its predictions, the spectral processing mechanism of the CNN was visualized by feature maps and the critical spectral features were identified by gradient-weighted class activation mapping. Such approaches brought insights on how CNN analyzes the spectra and enables the CNN operation to be explainable. Finally, the CNN model was incorporated with the microplasma platform to demonstrate the application of real-time VOC monitoring. The type of VOCs can be identified and reported via messages within 10 s once the microplasma is ignited. We believe that using CNN brings a novel route for plasma spectroscopy analysis for VOC classification and impacts the fields of plasma, spectroscopy, and environmental monitoring.

Degradation of different pesticides in water by microplasma: the roles of individual radicals and degradation pathways

Pesticides are emergent toxins often identified in aquatic environments. In the present study, microplasma was employed to reduce the pesticide content in water. The degradation efficacy, rate, and pathways of standard organophosphorus pesticides (namely, chlorpyrifos, chlorpyrifos oxone, and diazinone) and an organochlorine pesticide (namely, DDT solution) were evaluated using microplasma. High-performance liquid chromatography (HPLC) analysis was performed to elucidate the degradation efficiency of pesticides as a function of plasma-produced substances that originally contributed to the main reduction procedure. Microplasma produces several types of radicals or reactive substances, for instance dissolved ozone (O₃), nitrogen oxides, hydroxyl radicals (OH radicals), and hydrogen peroxide (H₂O₂). The removal potential differs due to the existence or absence of varieties of plasma-produced substances. The functions of major plasma-produced species on pesticide removal were determined by a passive technique. Nitrogen oxides showed a key role in organophosphorus pesticide removal, whereas dissolved ozone and OH radicals played major roles in DDT degradation. HPLC data showed that plasma-induced pesticide removal showed first-order reaction kinetics. The pesticide removal pathways through microplasma were validated by investigating the achieved data from LC-MS and GC-MS.

Microplasma UV lamp as a new source for UV-induced water treatment: Protocols for characterization and kinetic study

The newly emerged microplasma UV radiating technology can be a viable alternative to conventional radiation sources for UV water treatment. The capability of the microplasma UV lamp to monochromatically irradiate various wavelengths with different pulsation frequencies in a flat form opens new pathways for the development of novel UV-based water purifiers. This study is the first to systematically examine the microplasma UV lamp and develop a robust experimental method and apparatus for its operation to study the kinetics of both microbial and chemical pollutant degradation. The microplasma UV lamp was characterized in terms of its radiation profile and the impact of operating parameters on the lamp radiant power output. It was shown to be an instant-on and fast stabilized source. The radiant power output was a linear function of the electrical current and was not influenced by the lamp operating temperature and intermittent on/off cycles. A protocol was developed for obtaining reliable kinetic data for UV-induced elimination of microorganisms and micropollutants. An experimental setup was proposed for the kinetic studies, where the characteristics of the incident irradiance of the lamp, including uniformity, collimation, and divergence, were quantitatively evaluated. In addition, the water factor (WF) for calculating the average fluence rate was redefined for both the transient and steady state conditions. This modification is essential to account for changes in the UV transmittance of the medium, which could be an important factor for kinetic study of chemical contaminants. Two studied cases of microbial direct inactivation and the chemical photo-initiated oxidation process in different setups, based on the developed protocol, confirmed the reproducibility of the fluence-based kinetic data independent of the reactor size. The proposed protocol can be applied to the kinetic study of the elimination of microbial and chemical contaminants using microplasma UV lamps of any size, power, and peak wavelength.

Ultra-High Resolution Elemental/Isotopic Mass Spectrometry (m/Δm > 1,000,000): Coupling of the Liquid Sampling-Atmospheric Pressure Glow Discharge with an Orbitrap Mass Spectrometer for Applications in Biological Chemistry and Environmental Analysis

Many fundamental questions of astrophysics, biochemistry, and geology rely on the ability to accurately and precisely measure the mass and abundance of isotopes. Taken a step further, the capacity to perform such measurements on intact molecules provides insights into processes in diverse biological systems. Described here is the coupling of a combined atomic and molecular (CAM) ionization source, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma, with a commercially available ThermoScientific Fusion Lumos mass spectrometer. Demonstrated for the first time is the ionization and isotopically resolved fingerprinting of a long-postulated, but never mass-spectrometrically observed, bi-metallic complex Hg:Se-cysteine. Such a complex has been implicated as having a role in observations of Hg detoxification by selenoproteins/amino acids. Demonstrated as well is the ability to mass spectrometrically-resolve the geochronologically important isobaric ⁸⁷Sr and ⁸⁷Rb species (Δm ~ 0.3 mDa, mass resolution m/Δm ≈ 1,700,000). The mass difference in this case reflects the beta-decay of the ⁸⁷Rb to the stable Sr isotope. These two demonstrations highlight what may be a significant change in bioinorganic and atomic mass spectrometry, with impact expected across a broad spectrum of the physical, biological, and geological sciences. Graphical Abstract "".

Sweep Jet Collection Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization for Lipid Analysis Applications

Laser-induced acoustic desorption coupled to microplasma-based atmospheric pressure photoionization (LIAD-APPI) using a nebulized sweep jet to aid in dopant introduction and ion transmission has been applied to the analysis of model, apolar lipid compounds. Specifically, several sterols, sterol esters, and triacylglycerols were detected using dopants such as anisole and toluene. Additionally, several triacylglycerols, sterols, carboxylic acids, and hopanoids were detected from complex mixtures of olive oil and Australian shale rock extract as a first demonstration of the applicability of LIAD-APPI on real-world samples. Detection limits using a sweep jet configuration for α-tocopherol and cholesterol were found to be 609 ± 61 and 292 ± 29 fmol, respectively. For sterol esters and triacylglycerols with a large number of double bonds in the fatty acid chain, LIAD-APPI was shown to yield greater molecular ion or [M+NH₄]⁺ abundances than those with saturated fatty acid chains. Dopants such as anisole and toluene, with ionization potentials (IPs) of 8.2 and 8.8 eV, respectively, were tested. A greater degree of fragmentation with several of the more labile test compounds was observed using toluene. Overall, LIAD-APPI with a nebulized sweep jet requires minimal sample preparation and is a generally useful and sensitive analysis technique for low-polarity mixtures of relevance to biochemical assays and geochemical profiling. Graphical Abstract.

Miniaturized point discharge-radical optical emission spectrometer: A multichannel optical detector for discriminant analysis of volatile organic sulfur compounds

In this work, we proposed a miniaturized point discharge-radical optical emission spectrometer (PD-RES) as a multichannel optical detector for discriminant analysis of various volatile organic sulfur compounds (VOSCs). Under appropriate experimental conditions, the unique molecular emission of CS radical in the vicinity of 257.6 nm was recorded, as well as the atomic emission lines of C at 193.1 nm and 247.8 nm, the molecular emission of C₂ radical around 231.5 nm and CN radical nearby 384.8 nm. They were utilized as five optical channels for precise qualification and discrimination. Linear discriminant analysis (LDA) and principal component analysis (PCA) further demonstrated the robustness of this detector for discriminant analysis: 95 unknown samples from ten typical VOSCs were classified with accuracy of 98.9%. This proposed detector was further successfully applied to the discrimination of different concentrations of CS₂ in air samples and two types of isomers (functional group isomer and carbon-chain isomer).

Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas

We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation. Graphical Abstract ᅟ.

Effect of experimental conditions on size control of Au nanoparticles synthesized by atmospheric microplasma electrochemistry

Atmospheric microplasma electrochemistry was utilized to synthesize Au nanoparticles (NPs). The synthesized Au NPs were investigated as a function of reduction current, solution temperature, and stirring (or not) by using ultraviolet-visible (UV-Vis) absorbance and transmission electron microscopy (TEM). It was illustrated that high current promoted the growth of Au NPs with small size, and more Au NPs with large size were synthesized as a rise of temperature. The Au NPs often with small size were synthesized as a result of stirring. The production rate, the electrostatic repulsion, and the residence time of the Au NPs at the interfacial region play an important role in the growth of Au NPs. The results shed light upon the roadmap to control the size and particle size distribution (PSD) of Au NPs synthesized by atmospheric microplasma electrochemistry.