Search Results (816)

High-performance dielectric materials that can be processed at ultra-low temperatures are essential for next-generation LTCC technologies and compact RF–microwave components. In this work, a multicomponent Bi–Fe–Nb oxide system was synthesized using a modified citrate sol–gel method and thermally treated at only 400 °C to investigate its structural evolution and dielectric behavior. XRD and Raman analysis revealed the coexistence of a well-crystallized BiOCl phase embedded within a partially amorphous Bi–Fe–Nb–O matrix. SEM and EDS mapping confirmed the presence of two distinct microstructural regions, reflecting differences in local composition and crystallization kinetics. Microwave measurements at 2.7 and 5.0 GHz showed low dielectric losses and a stable dielectric response. Impedance spectroscopy in the RF range revealed strong Maxwell–Wagner polarization at low frequencies and thermally activated relaxation evidenced by the temperature shift in the modulus and impedance peaks. Arrhenius analysis of the relaxation frequencies yielded similar activation energies from both modulus and impedance formalisms, indicating a single underlying relaxation mechanism. Equivalent-circuit fitting confirmed non-Debye behavior, with nearly temperature-independent capacitance and decreasing resistance consistent with thermally activated conduction. These results demonstrate that the Bi–Fe–Nb system exhibits promising dielectric stability and functional behavior even when processed at exceptionally low temperatures. Full article

Nanocrystalline diamond (NCD) films were synthesized by microwave plasma chemical vapor deposition (MPCVD) from a CH₄/Ar mixture on seedless p-type Si(111) substrates at 100–400 °C. Crystallinity was evaluated by X-ray diffraction (Cu Kα); bonding by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS); morphology and thickness by scanning electron microscopy (SEM); defect states by thermoluminescence (TL). SEM shows continuous films with uniform thickness. XRD displays a broad (111) reflection near 2θ = 44°. Raman and XPS reveal temperature-dependent bonding: between 300 and 400 °C, the sp³ fraction increases relative to sp². TL glow curves show peaks at 157 °C and 270 °C, indicating electron-trap centers. These results demonstrate hydrogen-free and seedless NCD growth at low substrate temperatures, supporting potential electronic and dosimetry applications requiring a low thermal load. Full article

This study evaluated the efficacy of an environmentally friendly degreasing agent formulated from orange peel extract as both a cleaning agent and corrosion inhibitor for surgical instruments manufactured from 316LVM stainless steel. The extract was obtained via microwave-assisted hydrodistillation and subsequently blended with biodegradable surfactants. Its performance was compared against a benchmark commercial cleaner (West Oxyclean^®) through Tafel polarization, Electrochemical Impedance Spectroscopy (EIS), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). FTIR analysis confirmed the presence of terpenic compounds, predominantly limonene, alongside ethers, alcohols, and unsaturated structure characteristics of citrus essential oils. Polarization and EIS results showed that the formulation containing 0.12% extract exhibited the highest charge-transfer resistance and the lowest corrosion current density (0.093 μA/cm²), achieving an inhibition efficiency of 81.29%, whereas the 0.08% formulation showed greater corrosive response than the commercial cleaner. SEM imaging demonstrated a progressive decline in both the severity and density of localized corrosion attacks with increasing extract concentration, while XRD diffractograms indicated a marked reduction in corrosion-product formation—completely absent at the optimal concentration. These findings demonstrate that orange peel extract functions as an effective and environmentally sustainable corrosion inhibitor, capable of preserving the structural and surface integrity of surgical-grade steel. Its technical performance, combined with its biodegradable profile, positions it as a promising alternative to conventional industrial cleaners within medical and hospital applications. Full article

The optimization of BiVO₄-based structures significantly contributes to the development of a global system towards clean, renewable, and sustainable energies. Enhanced photocatalytic performance has been reported for numerous doped BiVO₄ materials. Bi³⁺-based compounds can be easily doped with rare earth (RE³⁺) ions due to their equal valence and similar ionic radius. This means that RE³⁺ ions could be regarded as active co-catalysts and dopants to enhance the photocatalytic activity of BiVO₄. In this study, a simple microwave-assisted approach was used for preparing nanostructured Bi_1−xEu_xVO₄ (x = 0, 0.03, 0.06, 0.09, and 0.12) samples. Microwave heating at 170 °C yields a bright yellow powder after 10 min of radiation. The materials are characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible–near-infrared diffuse reflectance spectroscopy (UV-Vis-NIR DRS), photoluminescence spectroscopy (PL), and micro-Raman techniques. The effects of the different Eu³⁺ ion concentrations incorporated into the BiVO₄ matrix on the formation of the monoclinic scheelite (ms-) or tetragonal zircon-type (tz-) BiVO₄ structure, on the photoluminescent intensity, on the decay dynamics of europium emission, and on photocatalytic efficiency in the degradation of Rhodamine B (RhB) were studied in detail. Additionally, microwave chemistry proved to be beneficial in the synthesis of the tz-BiVO₄ nanostructure and Eu³⁺ ion doping, leading to an enhanced luminescent and photocatalytic performance. Full article

Although graphene promises a wide range of applications, large-scale production of this material remains complex. One very common way of obtaining graphene is through a reduction in graphene oxide (GO). In order to fully control this production process, it is necessary to obtain data from different techniques, but a comprehensive characterization methodology and associated metrology are currently lacking. Here, we propose tools for substrate selection (in this study, the most appropriate were silicon and silicon dioxide on silicon) and precautions to be taken when setting up a correlative metrology method integrating atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman microscopy/spectroscopy, scanning microwave microscopy (SMM) and scanning thermal microscopy (SThM). Indeed, in order to obtain reliable data for each of these techniques applied to a unique graphene oxide flake, a strategy must be developed and could be implemented to monitor the reduction in GO. Emphasis was placed on the choice of the substrate and on the possible degradations generated by each of the techniques employed, and a running sequence was determined. Full article

Microwave-Induced Hydrogen Plasma (MIHP) is introduced as a novel synthesis route for producing high-entropy carbides (HECs), offering an alternative to conventional mechanical alloying and/or sintering techniques. In this study, a representative HEC composition, ${\mathrm{MoNbTaVWC}}_5$, was successfully synthesized using MIHP processing at 200 Torr. The process employs microwave energy to generate hydrogen plasma to facilitate carbothermal reduction of metal oxide precursors. The plasma environment generates abundant reactive atomic hydrogen species, which enhance reaction spontaneity and promote efficient HEC formation. X-ray diffraction confirmed the formation of a single-phase rocksalt-type face-centered cubic structure. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy confirmed uniform elemental distribution within the synthesized microstructure. Nanoindentation measurements yielded hardness and elastic modulus values consistent with literature reports for similar compositions. X-ray photoelectron spectroscopy confirmed the chemical state of carbon to be primarily bonded with metals as carbides, with only minor oxygen present as metal-oxides. Raman spectroscopy performed over the 750–1900 ${\mathrm{cm}}^{-1}$ range yielded a featureless spectrum with no detectable D or G bands often observed for sp²-hybridized disordered carbon, graphite, or graphene materials. These results validate the structural and chemical purity of the synthesized HECs. This work aims to demonstrate the feasibility and reproducibility of MIHP as a synthesis method for HECs. Full article

Terahertz (THz) waves, situated between the infrared and microwave regions, possess distinctive properties such as non-contact, high penetration, and high resolution. These properties render them highly advantageous for non-destructive thickness measurement of multilayer structural materials. In comparison with conventional ultrasound or X-ray techniques, THz thickness measurement has the capacity to acquire thickness data for multilayer structures without compromising the integrity of the specimen and is characterized by its environmental sustainability. The extant THz thickness measurement techniques principally encompass time-domain spectroscopy, frequency-domain spectroscopy, and model-based inversion and deep learning methods. A variety of methodologies have been demonstrated to possess complementary advantages in addressing subwavelength-scale thin layers, overlapping multilayer interfaces, and complex environmental interferences. These methodologies render them suitable for a range of measurement scenarios and precision requirements. A wide range of technologies related to this field have been applied in various disciplines, including aerospace thermal barrier coating inspection, semiconductor process monitoring, automotive coating quality assessment, and oil film thickness monitoring. The ongoing enhancement in system integration and continuous algorithm optimization has led to significant advancements in THz thickness measurement, propelling it towards high resolution, real-time performance, and intelligence. This development offers a wide range of engineering applications with considerable potential for future growth and innovation. Full article

This study investigates the valorisation of piscindustrial by-products, specifically fishbones from mackerel, horse-mackerel, and sardines, as sustainable sources of multi-mineral ingredients (MMIs) for future dietary supplementation. Ground fishbone powders were first analysed for moisture content and total ash to establish baseline composition. Following these preliminary assessments, the samples underwent mineral profiling using microwave plasma atomic emission spectroscopy (MP-AES), enabling quantification of calcium, phosphorus, magnesium, iron, zinc, sodium, potassium, copper, lead, cadmium, selenium, chromium, tin, manganese, and mercury. All three species yielded high concentrations of essential minerals, supporting their relevance as upcycled nutritional resources. A sardine-based capsule formulation was developed and compared with a commercial calcium supplement through 240 min dissolution testing. While calcium release values differed significantly from 75 min onward, both formulations exhibited similar dissolution profile shapes, despite differing dosage forms. Statistical analysis confirmed time- and formulation-dependent effects, with the sardine capsule demonstrating enhanced calcium bioaccessibility in later phases (95.26 ± 10.11 vs. 78.79 ± 5.39 mg). This work contributes to the advancement of the United Nations Sustainable Development Goals (SDGs), particularly SDG 3, SDG 12, and SDG 14. By transforming marine waste into health-promoting ingredients, and enabling revenue streams for ocean-cleaning charities, this initiative exemplifies circular innovation at the interface of nutrition, sustainability, and marine stewardship. Full article

The development of advanced semiconductor-based catalysts for the rapid degradation of emerging pharmaceutical pollutants in water remains a critical challenge in environmental science. In this study, we present the synthesis, characterization, and catalytic performance of zinc oxide (ZnO) microtetrapods decorated with plasmonic Ag nanoparticles. These microtetrapods have been designed to enhance piezo-, photo-, and piezo-photocatalytic degradation of metronidazole (MNZ), a persistent antibiotic contaminant. ZnO microtetrapods were synthesized by high-temperature pyrolysis and using atmospheric-pressure microwave nitrogen plasma, followed by photochemical deposition of Ag nanoparticles at various precursor concentrations (0–1 mmol AgNO₃). The structural integrity of the samples was confirmed through X-ray diffraction (XRD) analysis, while the morphology was examined using scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Additionally, spectroscopic analysis, including Raman, electron paramagnetic resonance (EPR), and photoluminescence (PL) spectroscopy, was conducted to verify the successful formation of heterostructures with adjustable surface loading of Ag. It has been shown that ZnO microtetrapods decorated with plasmonic Ag nanoparticles exhibit Raman-active properties. A systematic evaluation under photocatalytic, piezocatalytic, and combined piezo-photocatalytic conditions revealed a pronounced volcano-type dependence of catalytic activity on Ag content, with the 0.75 mmol composition exhibiting optimal performance. In the presence of both light irradiation and ultrasonication, the optimized Ag/ZnO composite exhibited 93% degradation of MNZ within a span of 5 min, accompanied by an apparent rate constant of 0.56 min⁻¹. This value stands as a significant improvement, surpassing the degradation rate of pristine ZnO by over 24-fold. The collective identification of defect modulation, plasmon-induced charge separation, and piezoelectric polarization as the predominant mechanisms driving enhanced reactive oxygen species (ROS) generation is a significant advancement in the field. These findings underscore the synergistic interplay between plasmonic and piezoelectric effects in oxide-based heterostructures and present a promising strategy for the efficient removal of recalcitrant water pollutants using multi-field activated catalysis. Full article

Industrial hemp (Cannabis sativa L.) is increasingly valued as a sustainable raw material for textile applications, yet reliable analytical tools to characterize and trace its origin are still limited. This study presents a pilot investigation on the elemental composition and strontium isotopic ratio (⁸⁷Sr/⁸⁶Sr) of Italian industrial hemp samples, with the aim of evaluating their potential as chemical markers for geographic traceability. Hemp stalks and fibers collected from different Italian regions were finely ground, mineralized using microwave-assisted digestion, and analyzed by atomic absorption spectroscopy (AAS), inductively coupled-plasma mass spectrometry (ICP-MS), and multicollector ICP-MS (MC-ICP-MS). The analytical protocol was validated using certified reference materials, showing recoveries between 95.7% and 102.1%. The measured ⁸⁷Sr/⁸⁶Sr ratios ranged from 0.7085 to 0.7105, with consistent intra-sample reproducibility and values reflecting regional geochemical backgrounds. Elemental profiling revealed marked variability among samples, particularly Sr, Ca, Fe, and trace metals. Principal Component Analysis (PCA) indicated partial clustering according to geographical origin, distinguishing northern from southern Italian samples. Heavy-metal concentrations (Hg, Pb, Cd) were well below international textile safety thresholds, confirming the environmental sustainability of local hemp cultivation. Full article

This study deals with diamond films grown via the microwave plasma-enhanced chemical vapor deposition technique (MWPECVD) on molybdenum (Mo) substrates of different roughness. This work is motivated by the necessity of overcoming the poor adhesion of diamond films on smooth Mo substrates, to ensure their effective application as cathodes for aerospace propulsion. The deposition process was monitored in situ using pyrometric interferometry (PI), thus enabling the real-time monitoring of both the rate and the temperature of deposition. The characterization of the obtained diamond films was performed using different techniques, such as Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The poor adhesion of diamond films on Mo substrates was solved by roughening their surface, which promotes residual stress reduction in the diamond films. In this work, the PI technique was also exploited to support the prediction of the adhesion and stability of diamond films before their exposure in air through the monitoring of the deposition temperature. This represents a novel point of our work that has never been discussed in other research papers, as pyrometric interferometry is generally mainly used to assess the rate and the temperature of deposition. Full article

The rapid development of nanomedicine is driving extensive research and the synthesis of new nanomaterials. Biocompatible nanoparticles have the potential to serve as both imaging agents for medical diagnostics and carriers for targeted therapy. Among the various nanocomplexes investigated for cancer theranostics, gold nanoparticles stabilized by polyamidoamine (PAMAM) dendrimers have proven to be a promising platform. The unique physicochemical properties of gold nanoparticles, when combined with the branched architecture of PAMAM dendrimers, enhance stability, biocompatibility, and functionalization capability, enabling precise tumour targeting, improved imaging contrast, and controlled drug release. In this paper, we demonstrate the synthesis of gold nanoparticles stabilized by 2nd generation PAMAM dendrimers using three different methods: sonication, microwave, and unassisted techniques. The described synthesis approaches provide a rapid and straightforward method to achieve monodisperse particle size distribution and high colloidal stability up to 3 months. Physicochemical characterization of the nanocomplexes was carried out using ultraviolet-visible light spectroscopy, dynamic light scattering with zeta potential analysis, infrared spectroscopy, and atomic force microscopy. Furthermore, the effects of selected concentrations of PAMAM:HAuCl₄ nanoparticles for all types of synthesis on human breast adenocarcinoma and human osteosarcoma cell lines were investigated using cytotoxicity assays. The results of the conducted tests show cytotoxicity values at a similar level. However, the sample synthesized using the sonication technique exhibited the lowest toxicity. Full article

(This paper presents the synthesis of a novel copper(II) metal complex with ethyl (2-(methylcarbamoyl)phenyl)carbamate and 3-methylquinazoline-2,4(1H,3H)-dione. The characterization of the compound was conducted through various techniques, including melting point determination, microwave plasma atomic emission spectrometry (MP-AES) for Cu, attenuated total reflection (ATR), IR, ¹H NMR, and ¹³C NMR spectroscopy. The coordination compound was obtained after mixing water solutions of the metal salt and the ligand dissolved in DMSO and water solutions of NaOH, in a metal-to-ligand-to-base ratio of 1:2:2. The ligand and the metal chloride were brought into the reaction at room temperature in DMSO and H₂O as solvents, respectively. The results indicate the successful formation of a stable mixed-ligand Cu(II) coordination compound involving N,O-donor ligands. Based on the obtained data, we assumed that the ligands are coordinated through N- and O-donor atoms. Spectroscopic data suggested that the ligand (3-methylquinazoline-2,4(1H,3H)-dione), by using (NaOH), coordinated to a metal ion as a monodentate ligand through the nitrogen atom of the NH group and ethyl (2-(methylcarbamoyl)phenyl)carbamate coordinated in a bidentate fashion through the N- and O-donor atoms of ester group. Additionally, two hydroxyl groups were bridged for two metal ions into the formed dimer structure. Full article

Carbon dots (CDs) are promising for agro-environmental applications; however, clear connections between synthesis, photophysical properties, size, and biosafety are often not well established. In this study, we map these relationships for glucose–arginine CDs (GA-CDs). By using microwave and hydrothermal routes at precursor ratios of 1:3, 1:9, and 1:15, we produced sub-10 nm nanoparticles (analyzed by dynamic light scattering and atomic force microscopy) that exhibit tunable absorption and emission properties, as well as surface properties (demonstrated through UV–Vis spectroscopy, 3D photoluminescence, and FTIR analysis). The hydrothermal 1:9 condition yielded the narrowest size distribution and red-shifted photoluminescence. Across biological models spanning plants, insects, plant-growth-promoting bacteria (PGPR), and human cells, GA-CDs were well tolerated, with no adverse changes detected in plant stress markers, aphid feeding behavior or fecundity, or PGPR growth. In A549 cells, viability remained stable up to a concentration of 0.125 mg mL⁻¹, while exposure to 0.5 mg mL⁻¹ reduced viability, establishing a practical operating range. These results provide a clearer picture of how the structure and properties of carbon dots derived from arginine and glucose are correlated to their safety. The GA-CDs are, therefore, useful, and traceable tools for agro-environmental research. The findings support their use as biocompatible nanomaterials for studying interactions among plants, insects, and microbes in agriculture. Full article

This study presents a highly effective method for depositing diamond-like carbon (DLC) films onto pipe substrates using a scanning deposition by plasma enhanced chemical vapor deposition. A microwave–sheath voltage combination plasma was employed to generate local high-density plasma along a rotating pipe. While conventional contact-mode deposition using a metal contactor suffers from arcing and surface damage due to unstable sliding contact during rotation, a non-contact deposition using a metal antenna was developed to overcome these limitations. Electromagnetic field simulations were conducted to evaluate microwave power absorption in various antenna geometries, showing that the flat-plate antenna demonstrated the most effective power coupling. Subsequent scanning deposition experiments to a rotating pipe using flat-plate antennas of different lengths revealed that the 100 mm configuration achieved the highest deposition volume rate (exceeding that of the contact-mode) while avoiding arcing. Optical emission observations during deposition confirmed the formation of high-density plasma surrounding the flat-plate antenna and Raman spectroscopy of the deposited film showed typical spectra of DLC films. The deposition rates of DLC-coated pipe showed no significant variation with respect to rotational angle, suggesting that rotation during deposition contributes to achieving uniform film thickness along the circumferential direction of the pipe. Full article