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The Mesoproterozoic Eon [1,600–1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were <0.1% of present levels, sufficiently lowto have inhibited the evolution of animal life. In contrast, using a different approach, we explore the distribution and enrichments of redox-sensitive trace metals in the 1,400 Ma sediments of Unit 3 of the Xiamaling Formation, North China Block. Patterns of trace metal enrichments reveal oxygenated bottom waters during deposition of the sediments, and biomarker results demonstrate the presence of green sulfur bacteria in the water column. Thus, we document an ancient oxygen minimum zone. We develop a simple, yet comprehensive, model of marine carbon−oxygen cycle dynamics to show that our geochemical results are consistent with atmospheric oxygen levels >4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.

An ultimate goal of electron paramagnetic resonance (EPR) spectroscopy is to analyze molecular dynamics in place where it occurs, such as in a living cell. The nanodiamond (ND) hosting nitrogen-vacancy (NV) centers will be a promising EPR sensor to achieve this goal. However, ND-based EPR spectroscopy remains elusive, due to the challenge of controlling NV centers without well-defined orientations inside a flexible ND. Here, we show a generalized zero-field EPR technique with spectra robust to the sensor’s orientation. The key is applying an amplitude modulation on the control field, which generates a series of equidistant Floquet states with energy splitting being the orientation-independent modulation frequency. We acquire the zero-field EPR spectrum of vanadyl ions in aqueous glycerol solution with embedded single NDs, paving the way towards in vivo EPR. Nanodiamonds containing NV centers are promising electron paramagnetic resonance sensors, however applications are hindered by their random orientation. Qin et al. propose a new protocol that makes the technique insensitive to the sensor’s orientation and present a proof-of-principle in situ demonstration.

A comparative study is illustrated on the catalytic activities of two structurally very different vanadium complexes, one oxovanadium(IV) complex 1 , V IV O(N 2 O 2 ) and the other dioxovanadium(V) complex 2 , V V O 2 (O 2 N) for the carbon dioxide cycloaddition to epoxides to yield cyclic carbonates. The binary catalyst, 1/TBAB is found to be non-selective towards the size of the epoxide substrates showing 90–100% conversions to cyclic carbonate products under the reaction conditions [60 °C, 5 bar ( p CO 2 ),  4 h]. However, the other binary catalyst, 2/TBAB having bulky tetrabutylammonium counter cation, could show selectivity resulting only 52% (allyl glycidyl ether), 63% (butyl glycidyl ether) and 54% (1-hexene oxide) conversions for longer tailed epoxides, on contrary to the  99% (epibromohydrin) and  88% (epichlorohydrin) conversions for shorter tailed epoxides. Further, taking the advantage of the modifiability of bromo functional group to imidazolium bromide functionality, the bromo functional group containing oxovanadium(IV) complex 1 has been affixed with imidazolium bromide functionality on reaction with N -methyl imidazole, and thus transformed to a bifunctional catalyst, 1A•Br . This in situ formed bifunctional catalyst, 1A•Br during the course of catalytic reaction, also showed to be an active catalyst system resulting in 100% conversion under the reaction conditions [60 °C, 5 bar ( p CO 2 ), 12 h]. Graphical Abstract VIVO(N 2 O 2 ) shows no substrate discrimination in the cycloaddition of CO 2 to epoxides, while anionic VVO 2 (O 2 N) having bulky tetrabutyl ammonium counter cation shows. Low conversions to cyclic carbonates are found for epoxides with longer tails compared to shorter tailed ones, when VVO 2 (O 2 N) is employed as a catalyst component. In situ modification of bromo functionalised ligand containing complex VIVO(N 2 O 2 ) to a bifunctional catalyst via introducing imidazoliumbromide functionalities.

Microwave annealing technology is gaining importance for processing metal oxides owing to its faster reaction time and volumetric heating. However, the utilization of this technique for producing vanadium oxide has not been explored. This study investigates the impact of both conventional annealing and microwave annealing on the crystal structure, light absorption, defect formation and humidity sensing performance of V 2 O 5 nanoparticles. V 2 O 5 was synthesized using the polyol method, involving the thermolysis of vanadyl ethylene glycol followed by annealing in oxygen atmosphere at 400 °C, 500 °C and 600 °C. The formation of layered, orthorhombic and stable phase of V 2 O 5 nanoparticles was confirmed using X-ray diffraction and Raman spectroscopy analyses. Field emission scanning microscopy showed the development of sheet-like morphology with average particle sizes of 99 ± 40 nm and 104 ± 51 nm for conventional annealing and microwave annealing, respectively. Annealing at elevated temperatures induced grain growth and facilitated oxygen diffusion, leading to the formation of oxygen vacancies. This was confirmed by optical studies, which revealed a reduction in the bandgap and the presence of defect states within the band. Relatively, microwave annealing resulted in fewer oxygen vacancies due to rapid heating, as evidenced by electron paramagnetic resonance studies and X-ray photoelectron spectroscopy. Moreover, the samples were evaluated for humidity sensing capabilities. The superior sensitivity of 48% at a higher relative humidity (97%) was observed for M5 sample that can be attributed to the smaller particle size facilitating more active sites, which makes it suitable for humidity sensing applications. Graphical abstract

The scientific interest in the development of novel metal-based compounds as inhibitors of bacterial biofilm-related infections and alkaline phosphatase (ALP) deregulating effects is continuous and rising. In the current study, a novel crystallographically defined heteroleptic V(IV)-curcumin-bipyridine (V-Cur) complex with proven bio-activity was studied as a potential inhibitor of ALP activity and bacterial biofilm. The inhibitory effect of V-Cur was evaluated on bovine ALP, with two different substrates: para-nitrophenyl phosphate (pNPP) and adenosine triphosphate (ATP). The obtained results suggested that V-Cur inhibited the ALP activity in a dose-dependent manner (IC50 = 26.91 ± 1.61 μM for ATP, IC50 = 2.42 ± 0.12 μM for pNPP) exhibiting a mixed/competitive type of inhibition with both substrates tested. The evaluation of the potential V-Cur inhibitory effect on bacterial biofilm formation was performed on Gram (+) bacteria Staphylococcus aureus (S. aureus) and Gram (−) Escherichia coli (E. coli) cultures, and it positively correlated with inhibition of bacterial ALP activity. In silico study proved the binding of V-Cur at eukaryotic and bacterial ALP, and its interaction with crucial amino acids of the active sites, verifying complex’s inhibitory potential. The findings suggested a specific anti-biofilm activity of V-Cur, offering a further dimension in the importance of metal complexes, with naturally derived products as biological ligands, as therapeutic agents against bacterial infections and ALP-associated diseases.Key points• V-Cur inhibits bovine and bacterial alkaline phosphatases and bacterial biofilm formation.• Alkaline phosphatase activity correlates with biofilm formation.• In silico studies prove binding of the complex on alkaline phosphatase.

V-doped TiO 2 materials (0.01, 0.05, 0.10, and 1.00 nominal atomic %) were synthesized by the sol-gel method and characterized by X-ray diffraction, Raman spectroscopy, UV–visible diffuse reflectance spectroscopy, N 2 adsorption–desorption isotherms, X-ray photoelectron spectroscopy, and H 2 -temperature programmed reduction. Two vanadium precursors (vanadyl acetylacetonate and ammonium metavanadate) and three calcination temperatures (400, 500, and 600 °C, with and without air circulation) were assayed. The efficiency of the materials as photocatalysts was studied by the degradation of phenol with UV and visible lamps. The photocatalyst prepared from vanadium acetylacetonate, with a vanadium content of 0.01 nominal atomic %, calcination at 400 °C without air circulation (0.01VTi-400), showed the best performance, reaching 100% and 30% degradation of phenol (50 μM) by irradiation with UV lamps (3 h) and visible lamps (5 h), respectively. To evaluate the efficiency of this catalyst in the degradation of other structurally related compounds, two substituted phenols were selected: 4-chlorophenol and 4-nitrophenol. The 0.01VTi-400 photocatalyst showed to be applicable to the degradation of phenolic compounds when the substituent was an activating group or a weakly deactivating group (for electrophilic reactions). Additionally, the selectivity of 0.01VTi-400 for phenol degradation in the presence of Aldrich humic acid was tested: phenol degradation reached 68% (3 h, UV lamps). The performance of 0.01VTi-400 indicated that it is a promising material for further applications.

Investigation of the VO 2+ ions in a single crystal of glycine zinc sulphate (GZS) using electron paramagnetic resonance (EPR) spectroscopy is done at ambient temperature. The single crystal was formed using a solution growth process that slowly evaporated at room temperature. EPR spectrum has been recorded for three mutually orthogonal crystal planes of the prepared GZS single crystal. In the present research work, two identical distinguishable VO 2+ ion sites have been followed and analyzed. According to the calculated g-principle values, the examination of the hyperfine line positions for all three planes explains why the impurity ion occupies rhombic crystal field symmetry with the surrounding ligands. Additionally, it is revealed that both sites occupy as a substitutional position in the crystal lattice site by taking the place of the zinc ion site, since the effect of spin–orbital motion coupling is dependent on the distinct nature of the paramagnetic ion environment. The optical absorption spectrum of vanadyl ions-doped glycine zinc sulphate was measured in the UV–Vis–NIR range. Comparing Spin Hamiltonian parameters and optical absorption studies, the molecular orbital coefficient values, such as β 1 *2 , β 2 *2 , e π *2 , K, (1 −  α 2 ), and (1 −  γ 2 ), were calculated. From the above data, the ionic bonding nature and contribution of σ, π bonding were found out which decide the different behaviors of electrons affecting the crystal properties. These results indicate that the GZS-VO 2+ single crystal system could serve as a suitable material for the NLO device application.

This work reports the preparation and characterization of composite membranes with potential applications in flow battery devices. A polymer solution of polyvinylidene fluoride (PVDF), sulfonated polyether ether sulfone (SPEES), and polyether sulfone (PES) was used to prepare proton exchange membranes with low permeation of cationic species, which is a desirable feature in energy conversion devices, such as vanadium flow batteries (VRFB). Vanadyl ion (VO2+) acidic solution was selected as a model to reveal the permeation capacity through the membranes as an affordable alternative to the Nafion® 117 commercial membrane. The effects of the chemical composition and the thickness of the membranes on the morphology and proton exchange properties were evaluated. Characterization of the membranes was performed using physicochemical techniques including water uptake, swelling ratio, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared, surface charge density, atomic force microscopy, dynamic mechanical analysis, electrochemical impedance spectroscopy for proton conductivity, proton exchange rate, and the permeability of VO2+ ions. With VO2+ ion permeability of the order of 0.62 mM and H+ exchange rates of up to 498.5 × 1018 H+ cm−2*µm−1*min−1, the PVDF/PES/SPEES composite membranes emerge as an option with potential application for VRFB compared to the Nafion® 117 membrane, which presented a VO2+ ion permeation value of 2.72 mM and H+ exchange rates of 445.2 × 1018 H+ cm−2*µm−1*min−1.

Diabetic people have a much higher rate of cardiovascular disease than healthy people. Therefore, heart and aortic tissues are target tissues in diabetic research. In recent years, the synthesis of new vanadium complexes and investigation of their antidiabetic/lowering effect on the blood glucose levels and antioxidant properties are increasing day by day. Our study aimed to examine the effects of synthesized oxovanadium (IV) complex of 2-[(2,4-dihydroxybenzylidene]hydrazine-1-[(N-(2-hydroxybenzylidene)](S-methyl)carbothioamide [VOL] on diabetic heart and aortic tissues, as well as in vitro lactate dehydrogenase (LDH) and myeloperoxidase (MPO) inhibition, antioxidant properties, and reducing power. Electrochemical characterization of the VOL was carried out by using Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) methods. In addition, in silico drug-likeness and ADME prediction were also investigated. For in vivo study, male Swiss albino rats were randomly selected and separated into four groups which are control, control + VOL, diabetic and diabetic + VOL. After the experimental procedure, biochemical parameters were investigated in homogenates of heart and aorta tissues. The results showed that VOL has a protective effect on heart and aortic tissue against oxidative stress. According to electrochemical experiments, one reversible oxidative couple and one irreversible reductive response were observed for the complex. In addition, in vitro LDH and MPO inhibition of VOL was examined. It was found that VOL had a protective effect on heart and aortic tissues of diabetic rats, and caused the inhibition of LDH and MPO in in vitro studies. On the other hand, evaluating the synthesized VOL according to in silico drug-likeness and absorption, distribution, metabolism, and excretion (ADME) prediction, it was found that VOL has drug-like properties and exhibited high gastrointestinal absorption. The VOL had a therapeutic impact on the heart and aortic tissues of diabetic rats, according to the findings.

The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology, which is still in the initial stage and facing many challenges. We developed a V 2 O 5 /TiO 2 granular catalyst and established the kinetic model for the simultaneous removal of NO and chlorobenzene (i.e., an important precursor of dioxins). The granular catalyst synthesized using vanadyl acetylacetonate precursor showed good synergistic catalytic performance and stability. Although the SCR reaction of NO and the oxidation reaction of chlorobenzene mutually inhibited, the reaction order of each reaction was not considerably affected, and the pseudo-first-order reaction kinetics was still followed. The performance prediction of this work is of much value to the understanding and reasonable design of a catalytic system for multi-pollutants (i.e., NO and dioxins) emission control.