Search Results (682)

A Ce-doped photocatalytic composite with easy solid–liquid separation capability was prepared and a heterojunction was constructed between BiVO₄ and Fe₃O₄ via a co-precipitation method. A variety of characterization techniques were employed, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), as well as other related methods. Its photocatalytic performance for the degradation of Rhodamine B (RhB) was also studied. The results indicate that the photocatalytic efficiency of BiVO₄/Fe₃O₄ is 1.4 times that of the pure BiVO₄ matrix. In particular, the photocatalytic efficiency of Ce_1.5%-BiVO₄/Fe₃O₄ was 2.2 times higher than that of the pure BiVO₄ matrix, and a 100% degradation rate of RhB was achieved within 30 min. The introduction of Fe₃O₄ not only forms a heterojunction with BiVO₄, increasing the active sites and surface oxygen vacancies of the material and effectively suppressing the recombination of photogenerated electron (e^-)-hole (h⁺) pairs, but it also enables the rapid separation of the material from the wastewater solution by the magnetic properties of Fe₃O₄. Additionally, the partial substitution of Ce for Bi in the BiVO₄ lattice reduces the bandgap energy, which enhances the utilization efficiency of visible light and improves the photocatalytic performance of the composite material. The mechanism of RhB degradation by Ce_1.5%-BiVO₄/Fe₃O₄ composite materials is also analyzed in this study. Quenching experiments and EPR tests revealed that h⁺ and ${·\mathrm{O}}_2^{-}$ were the primary reactive species in the degradation process. Full article

Copper dithiocarbamate complexes have long been known and are relevant in biology, medicine and material science; however, their low solubility in water can be a limitation. Therefore, the search for modified ligands is an important task. Copper complexes with five phosphorylated dithiocarbamates were investigated in aqueous solutions by several experimental and theoretical methods. Copper(II) bis-complex formation constants were obtained from spectrophotometric titrations. Based on UV-vis and EPR spectroscopy data, the presence of monoligand complexes (in excess copper) and hydroxy-forms (under basic conditions) was revealed. The structures of the obtained forms were optimized using DFT calculations. The instability of complexes under neutral and acidic conditions was established and interpreted by the dimerization upon protonation. This assumption is supported by association constants derived from quantum chemically computed Gibbs free energies for protonated and non-protonated copper(II) bis-dithiocarbamate complexes. Crystal structures of protonated binuclear and non-protonated mononuclear complexes were established using X-ray diffraction. The redox properties of the complexes were studied by cyclic voltammetry; the electrochemical behavior of the complexes was strongly influenced by pH. The scheme of the copper(I)/(II)/(III) species transformations, including chemical and electrochemical stages, is proposed on the base of experimental data and quantum-chemical calculation results. Full article

In this paper, we consider a series of new compact A-π-D photoinitiators consisting of donor aromatic fragments (naphthalene, anthracene, phenanthrene, pyrene and perylene) and a strong acceptor tricyanoethylene group—aryltricyanoethylenes (ArTCNEs). Spectral, photophysical, and electrochemical characteristics of ArTCNEs are studied. One-photon (with LED@405 nm) and two-photon (λ = 780 nm, impulse duration of 100 fs) photopolymerization of PETA can be effectively initiated by ArTCNEs with the tertiary amine N,N-dimethylcyclohexylamine DMCHA and/or the iodonium salt diphenyliodonium chloride Iod. Based on results of experiments on photodegradation, photopolymerization and EPR spectroscopy, a photoinitiation mechanism of radical photopolymerization was proposed for two-component (AntTCNE/DMCHA) and three-component (AntTCNE/DMCHA/Iod) initiating systems. The composition containing PerTCNE/DMCHA as a photoinitiator demonstrated the best reactivity under two-photon nanolithography conditions: the polymerization threshold was 2 mW at a laser beam scanning speed of 100 μm/s, and the widest fabrication window of 11 mW was typical for it. As an example, 3D “cage” structures were fabricated using the AntTCNE-based composition, and the test structure resolution parameters, such as the minimum line width and the distance between lines of 80 and 400 nm, respectively, were achieved. MTT experiments with human dermal fibroblasts showed promising preliminary biocompatibility of the resulting polymers, which opens up possibilities for using the obtained materials in biological applications. Full article

Background/Objectives: Chlorogenic acid (CGA) is a natural antioxidant widely distributed in various plant foods, exhibiting great potential for the development of natural antioxidant agents and biomedical applications. Methods: In this study, the antioxidant activity of CGA was first characterized via electron paramagnetic resonance (EPR) spectroscopy by determining its scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Meanwhile, its hydroxyl radical (•OH) scavenging activity in aqueous solution was quantitatively evaluated based on the signal intensity changes of DMPO-OH• adducts. Furthermore, a fluorescein-labeled chlorogenic acid derivative (FL-CGA) was utilized to visualize the distribution of CGA in major mouse organs following tail vein injection, with a specific focus on the kidney, and to investigate its penetration capacity into podocytes. Results: The results demonstrated that 0.35 mM CGA exerted potent scavenging activity toward highly reactive and cytotoxic •OH radicals, achieving a scavenging rate of 95.2% in a system where •OH was generated by continuous UV irradiation of 5 mM H₂O₂ aqueous solution for 30 min. Additionally, FL-CGA was specifically accumulated in the kidney and localized to the lysosomes of podocytes, while no signal was detected in the endoplasmic reticulum or mitochondria. Conclusions: This study provides experimental evidence to further elucidate the mechanisms underlying CGA-mediated intervention in renal injury, and lays a foundation for the further development and clinical application of CGA as a natural dietary antioxidant. Full article

UV-C irradiation enables digital zirconia colouring. This study investigates the atomic mechanism driving this defect-induced optical change. The band gap was calculated from the absorption spectra with the Tauc plot. The absorption spectra were measured using UV–visible spectroscopy. The surface composition was evaluated through X-ray photoelectron spectroscopy (XPS). The location of the oxygen vacancy was tested through electron paramagnetic resonance (EPR). The computer calculation using Density Functional Theory was conducted and the density of states (DOSs) were calculated. The band gap reduced rapidly from the baseline group (3.184 eV) to the 30 min irradiated group (3.097 eV). The XPS results showed that the electron density around O1s reduced and the electron density around Zr 3d increased. The EPR signal (g = 2.0037) increases progressively as the UV-C irradiation time is prolonged from 15 min to 24 h, indicating the accumulation of paramagnetic defect centres. The DOSs suggested the emergence of defect-associated states and band-edge tailing in oxygen deficient models, consistent with the experimentally observed reduction in the Tauc-derived optical band gap. This study confirmed the mechanism by which UV-C-induced oxygen vacancies modify the colour of 3Y-TZP. Full article

Photo-Fenton technology is considered an effective method for removing organic pollutants from water. In this work, a novel Mn-doped FeWO₄ (Mn-FeWO₄) photocatalyst was synthesized via a one-step hydrothermal method and applied for the photo-Fenton degradation of tetracycline (TC). The optimal Mn-FeWO₄-0.05 achieved 100% removal of TC within 60 min under visible light irradiation with a degradation rate constant of 0.0793 min⁻¹, which is 4.5 times higher than that of pristine FeWO₄. Systematic characterization revealed that Mn²⁺ ions were successfully incorporated into the FeWO₄ lattice, inducing lattice expansion and narrowing the bandgap from 2.37 eV to 2.25 eV, while also adjusting the conduction and valence band positions. This modulation significantly enhanced visible light absorption and promoted the separation and migration of photogenerated electron–hole pairs. In addition, the Mn²⁺/Mn³⁺ and Fe²⁺/Fe³⁺ dual redox cycles ensure the continuous generation of reactive oxygen species. Radical trapping experiments and electron paramagnetic resonance (EPR) spectroscopy demonstrated that superoxide radicals (•O₂⁻) and photogenerated holes (h⁺) were the dominant reactive species, while singlet oxygen (¹O₂) and hydroxyl radicals (•OH) played auxiliary roles. Moreover, Mn-FeWO₄-0.05 exhibited excellent stability, strong anti-interference ability against common anions, and high degradation efficiency toward various pollutants. Full article

Curcumin, a natural polyphenol derived from Curcuma longa, is widely recognized for its therapeutic properties. However, its clinical utility is limited because of poor solubility, rapid degradation and hence low bioavailability. To overcome these issues, nanoformulation approaches, especially PEGylated liposomes, have been explored as advanced delivery systems. PEGylation, which involves attaching polyethylene glycol (PEG) to the liposomal surface, enhances circulation time by creating a steric shield that reduces protein interactions and clearance by the mononuclear phagocyte system (MPS). However, PEG can alter lipid membrane properties, which may in turn affect curcumin’s solubility and distribution within the liposomal bilayer, ultimately reducing its loading efficiency. To ensure that PEG-modified liposomes can be effectively loaded with curcumin, we investigated curcumin–membrane interactions in saturated (DMPC) and unsaturated (POPC) liposomes, both in the presence and absence of PEG. Based on dissociation constants (K_d) obtained from fluorescence spectroscopy measurements, we found that PEGylated DMPC liposomes exhibit the strongest binding affinity for curcumin. Fluorescence quenching experiments showed that curcumin adopts a transbilayer orientation in all membranes examined. Curcumin’s location within PEGylated and non-PEGylated liposomal membranes was further confirmed by examining its effects on membrane properties, including fluidity, polarity, and oxygen transport. These effects were investigated using electron paramagnetic resonance (EPR) spectroscopy with spin labels. The results indicate that PEG does not impose major changes on membrane properties. Curcumin, however, was found to reinforce the liposomal membranes, increase their polarity, and reduce oxygen availability. Overall, the findings suggest that liposomes, particularly those composed of PEGylated DMPC, are effective vehicles for curcumin delivery. Full article

Photocatalytic H₂O₂ synthesis emerges as a promising green substitute for the energy-intensive anthraquinone process, yet its efficiency is limited by rapid charge recombination and limited surface active sites in bulk polymeric semiconductors. Herein, we report a topology-directed strategy to tailor the interlayer interactions of graphitic carbon nitride (g-C₃N₄), yielding ultrathin nanosheets with optimized electronic structures. The resulting catalyst exhibits an exceptional H₂O₂ production rate of 1.34 mmol g⁻¹ h⁻¹ under visible light, surpassing bulk g-C₃N₄ by a factor of 2.48. Water contact angle measurements confirm the superior hydrophilicity of the engineered nanosheets, facilitating interfacial mass transfer, while in situ FTIR and EPR spectroscopies unravel that the abundant exposed active sites optimize the adsorption configuration of the key *OOH intermediate and promote the generation of •O₂⁻ and •OH radicals. Regarding charge transfer dynamics, in situ EPR trapping experiments and Kelvin probe force microscopy (KPFM) reveal that the attenuated interlayer coupling induces a robust internal electric field, effectively suppressing carrier recombination and prolonging the exciton lifetime by a factor of 1.249. This work establishes a quantitative structure–activity relationship between interlayer engineering and exciton dynamics, offering a reliable protocol for the rational design of high-performance molecular photocatalysts. Full article

The exceptional stability of C-F bonds renders PFAS highly persistent in aqueous environments, posing significant challenges for conventional treatment technologies. While plasma-based technologies show promise, their efficiency is often limited by poor gas–liquid mass transfer in bulk liquid. Here, an in-house constructed ultrasonic atomization–dielectric barrier discharge (UEN-DBD) system was developed to promote PFAS degradation under non-thermal plasma conditions. Ultrasonic atomization generated microdroplets, which promoted PFAS enrichment at the surface of microdroplets and facilitate interactions with plasma-generated reactive species. Using perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) as model compounds, degradation behavior was evaluated over an initial concentration range of 0.01–1.0 ppm. At 0.01 ppm, degradation efficiencies of 96.06% for PFOA and 94.86% for PFOS were achieved within 5 min. Electron paramagnetic resonance (EPR) spectroscopy confirmed the formation of oxidative radicals (·OH) and suggested a mixed redox environment involving reactive species, potentially including superoxide (O₂·⁻) or hydrated electrons (e_aq⁻), in the discharge-treated system. High-resolution mass spectrometry results are consistent with a stepwise chain-shortening pathway dominated by successive –CF₂– scission, while fluoride-release measurements provided supporting evidence for partial defluorination. These findings advance the understanding of plasma-assisted PFAS degradation at the gas–liquid interface and provide a basis for the further development of plasma-assisted PFAS treatment strategies. Full article

Phenazine derivatives are promising metal-free chromophores with strong redox and photophysical properties, yet their use in photocatalytic hydrogenation remains limited. Here, we report a homogeneous phenazine-based system for the visible-light-driven hydrogenation of nitroarenes under mild conditions. Using nitrobenzene as a model substrate and triethanolamine as a sacrificial hydrogen source, the photocatalyst achieved aniline yields of up to 81% after 12 h of irradiation at 390 nm. Systematic variation in reaction parameters revealed that catalyst structure, solvent, and light wavelength strongly influence performance. Kinetic analysis indicated that prolonged irradiation reduces overall yield due to the reconversion of reactive intermediates. The system exhibited higher efficiency toward nitroarenes bearing electron-withdrawing groups, while aliphatic nitro compounds underwent only partial reduction. Mechanistic studies using UV–Vis, fluorescence, and EPR spectroscopy confirmed the formation of persistent radical species and supported a stepwise electron and proton transfer mechanism. This work showcases the potential of phenazine-based photocatalysts as metal-free platforms for nitroarene reduction under visible light. Full article

The purpose of this work is to investigate the binding state of inorganic elements to flavonoid components in aqueous extract of Silybum marianum (SM) seeds, as well as the antioxidant activity of the extract. This study employed reversed-phase high-performance liquid chromatography (RP-HPLC) to separate silymarin flavonoids in boiling water decoction of SM seeds, and collected the post-column effluent in the segments according to the retention time of seven main silymarin flavonoid components. Inductively coupled plasma mass spectrometry (ICP-MS) was subsequently utilized to quantify nine inorganic elements (As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Zn) in the collected HPLC fractions of the decoction. Meanwhile, electron paramagnetic resonance spectroscopy (EPR) was employed to assess the free radical scavenging activity of aqueous extract of SM seeds, using the signal intensity changes of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and DMPO-OH• adducts as quantitative metrics. The results showed that essential trace elements (Cu, Fe, Mn, Zn) mainly existed as inorganic ions or strong polar forms in the tea-like infusion, with weak binding to flavonoid compounds. On the other hand, the aqueous extract exhibited significant •OH scavenging capacity, with a scavenging rate of 95% against •OH generated by continuous 5 min ultraviolet irradiation of H₂O₂ aqueous solution. This study provides experimental evidence for the development of SM as a food–medicine dual-purpose resource, proposing that consumption of SM seed tea represents a facile and effective approach to supplement trace elements and intake silymarin for enhancing endogenous antioxidant defense. Full article

The technological promise of nonlinear optical (NLO) compounds has stimulated intense interest in optoelectronic devices, data storage, photonics, and anticancer therapy. Thiosemicarbazone ruthenium materials are of growing interest because of their tunable ligand framework and coordination sphere, allowing fine control over geometry, electronics, and functional properties. Here, we report an N-substituted salicylaldehyde thiosemicarbazone ligand and a series of octahedral Ru(III) complexes bearing triphenylphosphine or triphenylarsine and halide (Cl, Br) co-ligands. The complexes were characterized by elemental analysis, FT-IR, UV–Vis, EPR, mass spectrometry, and magnetic susceptibility measurements, which together confirm NS-chelation to a low-spin Ru(III) center in a distorted octahedral environment. Their photophysical and NLO responses were assessed by UV–Vis spectroscopy and powder second-harmonic generation measurements (Kurtz–Perry method), revealing promising NLO behavior. In parallel, antioxidant activity and in vitro anticancer effects against HeLa cells were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assays. These results provide insight into ligand-controlled structure–activity relationships, in which the halide (Cl/Br) and ancillary triarylphosphine co-ligands regulate electronic interactions and lipophilicity and ultimately increase biological performance, underscoring the dual materials and medicinal potential of these Ru(III) complexes. Full article

This paper investigates a ceramic material based on ferrite-doped zirconia intended for use as a solar absorber in systems designed for the conversion of solar energy into thermal energy. The experimental study details the synthesis procedure of the ferrite-doped zirconia ceramic and its structural, morphological, optical, and magnetic characterization using X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy, electron paramagnetic resonance (EPR), and optical band gap energy determination. XRD analysis confirms the presence of the crystalline ferrite phase, which is responsible for the enhanced solar absorption properties. UV–Vis investigations reveal intense absorption bands across the ultraviolet, visible, and near-infrared regions, indicating high solar radiation absorptivity. These properties recommend the investigated ceramic as a promising solar receiver material for solar thermal power plants comparable to conventional materials such as carbides and nitrides. Full article

Catalytic ozonation often suffers from a low ozone utilization rate and incomplete mineralization of organic pollutants. To address these challenges, we designed and prepared a novel catalyst via a one-step thermal polymerization method, anchoring single-atom manganese on a glucose-derived carbon network-modified C₃N₅ framework (Mn/C-C₃N₅). Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) on an FEI Titan Themis Z microscope confirmed the atomic dispersion of Mn sites, while Raman spectroscopy using a Renishaw inVia Reflex laser micro-Raman spectrometer verified the successful incorporation of a graphitic carbon network within the C₃N₅ matrix. Moreover, electrochemical analyses, including electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) performed on a Bio-Logic SP-150 electrochemical workstation, demonstrated that the integration of the conductive carbon matrix substantially enhanced the interfacial charge transfer capability. The optimized Mn/C-C₃N₅ catalyst demonstrated exceptional performance in phenol mineralization, achieving a 97% total organic carbon (TOC) removal within 60 min, a remarkable improvement compared to pristine C₃N₅ (30%). Furthermore, the catalyst exhibited excellent operational stability, preserving more than 95% of its original activity over five repeated runs. Mechanistic investigations, including electron paramagnetic resonance (EPR) spectroscopy and radical quenching experiments, revealed that the Mn/C-C₃N₅ system accelerated the generation of multiple oxidizing radicals (•O₂⁻, ¹O₂, and •OH), with •OH identified as the predominant reactive species responsible for complete mineralization. This work establishes an integrated catalytic platform and provides fundamental insights into electronic structure modulation for designing advanced oxidation catalysts. Full article

Ionotropic alginate-based hydrogelation by divalent metal interaction has been employed to study the effect that different types of ions might have on gel formation. In this regard, EPR and IR spectroscopies, as well as rheology techniques, have been used to evaluate the influence of divalent cations on gel formation, and at the same time to assess host–guest interactions. Alginate was functionalized with TEMPO moieties; therefore, TEMPO-alginate system was taken as a reference. The novelty of this study consists of using a mixture of adamantyl-TEMPO-functionalized alginate and β-cyclodextrin linked through 1,3-diaminopropane to assess the host–guest interactions in functionalized gels. The properties of divalent cations considered in this study (Ba²⁺, Ca²⁺, Sr²⁺, Zn²⁺) were proven by changes in spectral parameters of paramagnetic moieties, while the viscoelastic moduli as functions of shear strain and frequency were evaluated through rheology measurements. Overall, the information obtained from these investigations has shown that the properties of the alginate gels are influenced both by the type of divalent cation used for complexation and by the host–guest interactions. The results show that the type of the cation significantly affects gel strength; therefore, Ba²⁺ forms the strongest gel, while Zn²⁺ the least resistant. Additionally, a high immobilization of the spin-labeled probes has been obtained by the addition of tosylated β-cyclodextrin in the alginate gel network containing Ba²⁺ ions. Full article