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In this study, we present a novel pulsed microwave-induced plasma (MIP) source coupled with a glow discharge for optical emission spectrometry (MIP-OES), operating at 1000 W power and a frequency of 2.45 GHz. The MIP cavity consists of a stainless steel cylindrical waveguide connected to a circular resonator made of the same material, joined through a dielectric quartz disc. The output of the MIP cavity is linked to a closed glow discharge quartz tube and a mechanical pump. Numerical simulations were employed to optimize the structure and dimensions of the MIP cavity. The nozzle position of the cylindrical resonator's output was precisely adjusted to align with the maximum magnetic field, achieving the TM011 mode, which results in a point plasma with high density. This configuration enables the cavity to produce a dense, warm plasma emission zone with a consistent emission rate around the circumference of the emitting source. The results demonstrate that the designed MIP source exhibits a significantly higher density and temperature compared to other sources with similar microwave parameters. [ABSTRACT FROM AUTHOR]

The utilization of hydrogen as an energy carrier faces a challenge due to its limited presence in its pure form in the Earth's atmosphere, necessitating its extraction from various sources. Among hydrogen production methods, microwave-induced plasma molecular cracking shows promise as an alternative. This review explores how different operational parameters of a microwave-induced plasma system with gas-phase discharge impact hydrogen production performance. Performance indicators include hydrogen production rate, energy yield, and final hydrogen concentration. Parameters influencing hydrogen production encompass microwave power, gas flow rate, initial hydrogen concentration, steam addition, gas injection method, and plasma-forming gas type. Other vital system parameters are also discussed. Higher absorbed power leads to increased hydrogen production, albeit less efficiently. Elevated carrier gas flow rate reduces residence time, consequently lowering performance, while higher fuel gas flow rates enhance hydrogen production. Introducing steam can enhance indicators and reduce soot, and injecting fuel gas directly into the plasma torch tip yields optimal hydrogen production. Avoiding excessive power, fuel gas flow, or water vapor is important, as hydrogen saturation can limit further performance enhancement. • Microwave-induced plasma appears as a promising alternative for H 2 production. • Operational parameters' impacts on the system performance were analyzed. • Steam addition and gas injection methods' impacts on H 2 production were discussed. • Optimal practices for enhanced H 2 production were determined. [ABSTRACT FROM AUTHOR]

To obtain reliable results in the quantitative determination of rare earth elements (REE) by atomic emission spectroscopy, it is particularly important to take into account the matrix effects of the macrocomponents contained in the analyzed solutions. Analytes obtained by liquid-phase and autoclave opening of geological samples of REE ores and minerals contain significant amounts of strong mineral acids used as reagents and such macrocomponents of the samples as aluminum (aluminosilicates) and phosphorus (phosphates in apatites). Here, we studied the effects of hydrochloric, nitric, sulfuric, and orthophosphoric acids and aluminum on the relative intensity of the ion analytical lines of La, Ce, Nd, Sm, Gd, Tb, Er, and Yb in atomic emission spectroscopy of the microwave-induced plasma (AES MIP). With an increase in the acid concentration from 0 to 1 mol/L, the relative intensity of the spectral lines of all investigated REE decreased monotonically by 10–20%. The depressing effect of aluminum, which is due to a decrease in the degree of ionization of REE atoms, was much stronger and reached 70%. It was shown that the AES MIP method is not inferior to atomic emission spectroscopy of inductively coupled argon plasma in terms of the detection limits of lanthanum, cerium, gadolinium, and erbium.

As a typical carbamate pesticide, methomyl was once widely used in agriculture for its excellent broad-spectrum insecticidal effect. However, due to its high toxicity, long half-life, and difficult degradation properties, it poses a serious challenge to water environment pollution. In this study, an electrode-free discharge microwave-induced plasma technology was used to rapidly and efficiently degrade methomyl in aqueous solution. In this experiment, the statistical design of experiments (DOE) was adopted to optimize the plasma degradation parameters. Under the optimized parameters (P = 140 W, D = 0 mm, R = 0.5 L/min), 78.4% removal of 50 mg/L of methomyl was achieved after 8 min. The optical emission spectrometry and free radical detection experiments showed that the active substances generated by the collision reaction between plasma and water molecules occurring at the gas–liquid interface were the key factors to exert the degradation effect. The degradation rate of methomyl decreased by 73.2% after the addition of tert-butanol (OH burster), while it decreased by only about 12.0% after the addition of peroxidase. These implied that ∙OH was largely responsible for methomyl degradation. In addition, based on the detected intermediates, possible degradation mechanisms and pathways were analyzed. [ABSTRACT FROM AUTHOR]

The objectives of this work are to develop nanocarrier systems for the Ru(II)-p-cymene naproxen antitumor metallodrug, [Ru(η6-p-cymene)(npx)Cl] or Rupcy, based on polymeric nanoparticles (NPs) composed by the biodegradable poly(lactic acid) (PLA) and the hydrophilic polymerised β-cyclodextrin (PolyCD); to validate an analytical method for determination of Ru incorporated into the metallodrug loaded-NPs. The PolyCD was prepared by single step condensation and polymerisation reaction and incorporated as a polymer blend during the fabrication of PLA/PolyCD blends NPs and also as a core/shell structure built by adsorption of the PolyCD onto the surface of PLA NPs to give PLA(core)/PolyCD(shell) NPs. Three different loaded-systems incorporating the metallodrug (Rupcy-PLA NPs (1), Rupcy-PLA/PolyCD blends (2), and Rupcy-PLA(core)/PolyCD(shell) NPs (3)) were prepared by nanoprecipitation. The characterisation was performed by Proton Nuclear Magnetic Resonance, Matrix Assisted Laser Desorption/Ionization Time-of-Flight, Fourier-Transform Infra-red and UV-VIS Electronic Absorption Spectroscopies, Thermogravimetric Analysis, Differential Scanning Calorimetry, Dynamic Light Scattering, and Electrophoretic Light Scattering. Ru was determined by Microwave Induced Plasma Optical Emission Spectrometry (MIP-OES) with validation of the method. The metallodrug entrapment efficiency was around 90% (w/w) and drug loading was at 3–4% (w/w). The characterised metallodrug-loaded systems exhibited monomodal size distributions and appropriate hydrodynamic diameters [218.3 ± 13.5 (1), 205.4 ± 14.4 (2), 231.5 ± 22.0 (3) nm] and zeta potential values [−31.5 ± 2.2 (1), −26.1 ± 4.5 (2), −28.8 ± 6.1 (3) mV]. The validation of the MIP-OES method by evaluating selectivity, linearity, precision, accuracy, and limits of detection and quantification succeeded. The NPs parameters are compatible with colloidally stable systems. The MIP-OES method showed to be simple, reliable, and feasible to quantify indirectly the amount of the metallodrug-loaded into the PLA NPs. [ABSTRACT FROM AUTHOR]

As a prospective ignition technique, microwave-assisted spark ignition (MAI) can accelerate flame and thus satisfy the demand for effective ignition. However, its acceleration mechanism on flame velocity is still unclear, which hinders its application and optimizations. Therefore, this research focuses on understanding the flame acceleration mechanism behind MAI. In this paper, MAI is achieved through radiating a microwave pulse after spark ignition. The flame velocity and the precise absorbed energy under different combustion conditions are investigated with flame kernel's Schlieren images and microwave energy diagnostics, respectively. The results show that MAI accelerates flame primarily by the interaction between microwave plasma and flame front, rather than the free electrons within the flame. Specifically, microwave accelerating flame takes two processes: energy absorption, and velocity match. Energy absorption refers to the microwave energy absorbed by residual electrons after ignition to generate and sustain microwave plasma, while velocity match involves the outward plasma with faster velocity propelling the slower flame front. Moreover, the plasma velocity shows a positive relationship with absorbed microwave energy. The velocity match between microwave plasma and flame is important to successful flame acceleration. Besides, the efficiency of energy absorption and flame acceleration varies with plasma type (glow or incandescent). Glow plasma is characterized by effective flame acceleration but relatively low absorption efficiency, and incandescent plasma is in reverse. The maximum absorption efficiency can be elevated to 70 % with incandescent plasma occurring. Ultimately, the plasma velocity declines with its traveled distance, which might impair the flame acceleration. [ABSTRACT FROM AUTHOR]

As a prospective ignition technique, microwave-assisted spark ignition (MAI) efficiently enhances ignition with plasma absorbing microwave energy. This paper achieves MAI through radiating a single 0.2 ms microwave pulse after the initial spark ignition, and investigates the ignition performance and the precise absorbed energy of MAI in different absorption patterns. The absorption pattern is tailored by the microwave pulse power. The results show that the enhancement of MAI can be divided into two categories based on ignition performance and absorbed energy: the glow enhancement and the incandescence enhancement. Compared to the glow enhancement, the incandescence enhancement has a greater energy absorption efficiency and thus induces more significant ignition enhancement. Additionally, the effect of gas parameters, including gas pressure and components, on these two enhancement categories is studied. Increasing pressure or decreasing methane concentration facilitates the generation of incandescence enhancement. Ultimately, the causes of both enhancements are discussed. The incandescence enhancement may be originated from the ionization of metal particles in the microwave field, whereas the glow enhancement is attributed to gas ionization. This work highlights the potential application of metal-microwave discharge on MAI, which can play a crucial role in suiting different conditions and further understanding the mechanisms of MAI. [ABSTRACT FROM AUTHOR]

In the past few years, microwave induced plasma optical emission spectrometry (MIP-OES) has generated great interest as an alternative technique to inductively coupled plasma-based techniques due to its lower operational cost. Since MIP-OES suffers from severe matrix effects due to easily ionizable elements (EIEs) (Na, Ca, etc.), it is unclear whether this technique could be employed for elemental bioavailability studies in soils and sediments since the main extractant solutions employed in such works may contain high levels of these elements. Thus, the aim of this work was to evaluate the feasibility of MIP-OES as a detector for such applications. To this end, the influence of different extractant solutions (0.25 mol L−1 MgCl 2 , 0.25 mol L−1 CaCl 2 , 0.10 mol L−1 acetic acid, 0.05 mol L−1 Na 2 EDTA, 0.25 mol L−1 NaNO 3 , 0.25 mol L−1 NaOAc/HOAc and 0.10 mol L−1 NH 2 OH·HCl) on the analyte emission of several elements (As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Rh, Se, Sr and Zn) was investigated. Results were compared to those obtained using a reference solution made of 5% w w−1 HNO 3 solution. For saline extractant solutions, both the optimum nebulizer gas flow rate (Q g) and analyte emission were modified with regard to the reference solution. In general, the optimum Q g was reduced by between 0.1 and 0.2 L min−1 for both ionic and atomic lines. Under optimum Q g conditions, analyte emission was supressed by saline solutions except for atomic lines with an upper electronic state below 4 eV, which were enhanced. The magnitude of matrix effects was strongly dependent on EIE ionization energy. The lower the ionization energy, the greater the matrix effects were registered. No measurable matrix effects were registered on both Q g and analyte emission within experimental uncertainties for NH 2 OH·HCl and acetic acid extractant solutions. Experimental data suggest that matrix effects were related to changes in plasma characteristics and the analyte excitation/ionization mechanism. To mitigate matrix effects and improve long-term MIP-OES performance, internal standardization using either Rh (343.489 nm and 369.236 nm) or OH molecular emission band (308.958 nm) was required. This calibration methodology was successfully applied to the study of the elemental bioavailability in soil samples from a vineyard affected by copper-based fungicides and sediment samples from an area affected by mining waste. [Display omitted] • MIP-OES is suitable as a detector for elemental bioavailability studies. • Saline extraction solutions affect to Q g and the analyte emission signal. • Matrix effects depend on wavelength characteristics and the extractant solution. • Internal standard mitigates matrix effects and improve long-term MIP-OES performance. [ABSTRACT FROM AUTHOR]

Injectable fiducial markers are crucial in image-guided radiation therapy (IGRT) due to their minimally invasive operations and improved patient compliance. This study presents the development of a ready-to-use injectable fiducial marker utilizing alginate stabilized-gold nanoparticles (alg-Au NPs) and a body temperature-activated in situ gel-forming system. Gram-scale alg-Au NPs were prepared in an hour by a green microwave-induced plasma-in-liquid process (MWPLP). Sodium alginate was introduced in this process to avoid aggregation between Au NPs, which ensured their stability and injectability. The gelation behavior of alginate with divalent cations and a temperature-dependent release of calcium source (glucono-delta-lactone (GDL) and CaCO 3 ) served as the foundation of the body temperature-activated in situ gel-forming system. The injectable fiducial marker GDL/CaCO 3 /alg-Au NPs could maintain a liquid state at a low temperature for a higher injectability. After injection, on the other hand, Ca 2+ would be released due to the body temperature-activated hydrolysis of GDL and the subsequent reaction with CaCO 3 , which would initiate the gelation of alginate. The injectable fiducial marker can be therefore delivered via injection and form gel at target site to avoid marker movement or Au NPs leakage after injection. Rheological measurements demonstrate the stability and gelation behavior of GDL/CaCO 3 /alg-Au NPs at different temperatures. Furthermore, the injectability and imaging ability of GDL/CaCO 3 /alg-Au NPs were also examined. In summary, ready-to-use injectable fiducial marker GDL/CaCO 3 /alg-Au NPs were developed via a green and facile method for IGRT.