Search Results (1,256)

A rational synthetic approach is introduced to enable hydrogen insertion into oxides by forming a solid solution of a reducible oxide with a less reducible oxide as exemplified with RuO₂ and TiO₂ (Ru_x, a mixture of x% RuO₂ with (100−x)% TiO₂). Hydrogen exposure at 250 °C to Ru_x (Ru_x_250R) results in substantial hydrogen incorporation accompanied by lattice strain that in turn induces pronounced activity variations. Here, we demonstrate that hydrogen incorporation in mixed oxides promotes the oxidation catalysis of propane combustion with Ru_60_250R being the catalytically most active catalyst. Full article

Understanding the local environment of luminescent centers in phosphors serves as a blueprint for designing the luminescent properties of phosphors. Chemical substitution is a general strategy for engineering the local structure around luminescent center ions. In this study, we systematically investigate the luminescent properties of Ga-substituted Eu-doped CaYAlO₄ (CYAGO:Eu) phosphors and the local structure of the Eu ions. The Ga substitution at the Al sites leads to a significant enhancement in the electric dipole transition of Eu³⁺ (⁵D₀ → ⁷F₂). The Judd–Ofelt analysis reveals that Eu³⁺ ions are substituted for Ca/Y, and the Ga substitution increases the asymmetricity of the local structure around the Eu ions because of the different ionic radii and electronegativities of Al and Ga. In addition, Eu²⁺ emission is missing regardless of the Ga substitution and post-hydrogen treatments. The present work provides deeper insight into the role of chemical substitution in oxide phosphors. Full article

Artemisia absinthium (A. absinthium) leaf extract was successfully used to create zinc oxide nanoparticles (ZnO NPs), and their properties were investigated via several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), and ultraviolet–visible spectroscopy (UV–Vis spectroscopy). SEM analysis confirmed the spherical and elliptical shapes of the particles. Three different zinc peaks were observed via EDX at the energies of 1, 8.7, and 9.8 keV, together with a single oxygen peak at 0.5 keV. The XRD analysis identified ZnO NPs as having a hexagonal wurtzite structure, with a particle size that decreased from 24.39 to 18.77 nm, and with an increasing surface area (BET) from 4.003 to 6.032 m²/g for the ZnO (without extract) and green ZnO NPs, respectively. The FTIR analysis confirmed the groups of molecules that were accountable for the stabilization and minimization of the ZnO NPs, which were apparent at 3400 cm. Using UV–Vis spectroscopy, the band-gap energies (Egs) for the green ZnO and ZnO (without extract) NPs were estimated, and the values were 2.65 and 2.79 eV, respectively. Full article

The coordination of rare-earth metal ions (Ln³⁺) to polyoxometalates (POM) is regarded as a way of modifying and controlling their properties, such as single-molecular magnetism or luminescent behavior. The half-sandwich complexes of Ln³⁺ with monolacunary Keggin POMs (Ln³⁺/POM = 1:1) are of particular interest, since the Ln³⁺ retains its ability to coordinate extra ligands. Thus, the knowledge of the exact structures of 1:1 Ln/POM complexes is important for the development of reliable synthetic protocols for hybrid complexes. In this work, we isolated three 1:1 Gd³⁺/POM complexes of the general formula Cat₄Gd(PW₁₁O₃₉)·xH₂O (Cat = K⁺ or Me₄N⁺). Complex (Me₄N)₂K₂[Gd(H₂O)₂PW₁₁O₃₉]·5H₂O (1) is polymeric, revealing a layered structural motif via bridging Gd³⁺ and K⁺ ions. Complexes (Me₄N)₆K₂[Gd(H₂O)₃PW₁₁O₃₉]₂·20H₂O (2) and (Me₄N)₇K[Gd(H₂O)₃PW₁₁O₃₉]₂·12H₂O (3) are classified as dimeric; the difference between them consists of the different crystal packing of the polyoxometalates, which is induced by a variation in the cationic composition. Isostructural complexes have also been characterized for praseodymium, europium, terbium and dysprosium. The coordination number of Ln³⁺ (8) persists in all the compounds, while the binding mode of the POM varies, giving rise to different architectures with two or three H₂O co-ligands per Ln³⁺. However, whatever the particular structure and exact composition, the {Ln(PW₁₁O₃₉)} moieties are always involved in bonding with each other with the formation either of polymeric chains or dimeric units. In water, these aggregates can dissociate with the formation of [Ln(H₂O)₄PW₁₁O₃₉]^4-. This behavior must be taken into account when choosing L for the design of hybrid {Ln(L)POM} complexes. Full article

The creation of effective catalytic systems for cross-coupling reactions, reduction, etc., capable of working in water-organic or pure aqueous media is in great demand. The article presents the synthesis of NHC-palladium complexes of the PEPPSI type based on monoimidazolium derivatives of thiacalix[4]arene. The structure of the imidazolium precursors, obtained in 81–88% yields and the complexes themselves, obtained in 40–50% yields, is established using modern methods, including X-ray structural analysis and high-resolution mass spectrometry. It is shown that the obtained complex with bulk substituents near the palladium atom is not inferior to the well-known PEPPSI-type Organ’s catalyst in the catalysis of Suzuki-Miyaura coupling and is four times superior to the latter in the p-nitrophenol reduction reaction. Given the presence of free phenolic hydroxyl groups in the macrocycle, the obtained complexes are of interest for further post-modification or for immobilization on a carrier. Full article

A complex study of the structure, morphology, and electrochemical properties of the Pt²⁰/SnO₂¹⁰/RGO electrocatalyst is presented. The advantage of the chemical synthesis of reduced graphene oxide (c-RGO) compared to thermal methods (t-RGO) is due to the formation of graphene plates with amorphous carbon black agglomerates and the chemical composition of the surface. The nature of the interaction between platinum and tin dioxide particles and a conclusion about the formation of heterostructures Pt-SnO₂ with the surface interaction of lattices excluding the formation of hetero phases has been established. This achieves high dispersity during the formation of platinum particles without significant agglomeration and increases the electrochemical surface area (ESA) of platinum to 85 m² g⁻¹ vs. carbon black. In addition, the surface interaction of particles and the formation of hetero-clusters Pt-SnO₂ can cause the improved activity and stability of the Pt²⁰/SnO₂¹⁰/c-RGO electrocatalyst. Full article

Metal cyanide clusterfullerenes (CYCFs) are formed via the encapsulation of a single metal atom and a cyanide unit inside fullerene cages, endowing them with excellent properties in various applications. In this work, we report the synthesis, isolation, and characterizations of the first cases of thulium (Tm)-based CYCFs with the popular C₈₂ carbon cages. The structural elucidation of the two [email protected]₈₂ isomers was achieved via diverse analytical techniques, including mass spectrometry, Vis-NIR spectroscopy, single-crystal X-ray crystallography, and cyclic voltammetry. The crystallographic analyses unambiguously confirmed the molecular structures of the two [email protected]₈₂ isomers as [email protected]_s(6)-C₈₂ and [email protected]_2v(9)-C₈₂. Both TmCN clusters adopt a well-established triangular configuration, with the Tm ion located on the symmetrical plane of the carbon cages. The electronic structures of both [email protected]₈₂ isomers adopt a Tm³⁺(CN)⁻@(C₈₂)²⁻ configuration, exhibiting characteristic spectral and electrochemical properties reminiscent of divalent endohedral metallofullerenes (EMFs). Intriguingly, unlike the divalent Tm²⁺ ion observed in the mono-metallofullerenes [email protected]_2n, a higher oxidation state of Tm³⁺ is identified in the monometallic TmCN cluster due to bonding with the cyanide anion. This result provides valuable insight into the essential role of the non-metallic endo-units in governing the oxidation state of the metal ion and the electronic behaviors of EMFs. Full article

In this study, the biological properties of novel borenium and borinium compounds in terms of their oxidative, genotoxic, and cytotoxic effects were assessed on cultured human peripheral blood cells, as well as several types of cancer cells. Our results revealed that the borinium compounds yielded the best results in terms of supporting total antioxidant capacity (TAC). In fact, borenium 1, borenium 2, borenium 3, borinium 4, and borinium 5 compounds elevated TAC levels of cultured human blood cells at rates of 42.8%, 101.5%, 69.8%, 33.3%, and 49.2%, respectively. There were no statistically significant differences (p > 0.05) between the negative control and the groups treated with all borinium and borenium concentrations from the micronucleus (MN) and chromosome aberration (CA) assays, demonstrating the non-genotoxic effects. Moreover, borenium 1 (60.7% and 50.7%), borenium 2 (70.4% and 57.2%), borenium 3 (53.1% and 45.2%), borinium 4 (55.1% and 48.1%), and borinium 5 (51.0% and 36.1%) minimized the mitomycin C(MMC)-induced genotoxic damages at different rates as determined using CA and MN assays, respectively. Again, it was found that the borinium compounds exhibited higher cytotoxic activity on cancer cells when compared to borenium compounds. Consequently, in light of our in vitro findings, it was suggested that the novel borinium and borenium compounds could be used safely in pharmacology, cosmetics, and various medical fields due to their antioxidant and non-genotoxic features, as well as their cytotoxicity potential on cancer cells. Full article

Green nanoparticle (NPs) synthesis is eco-friendly, non-toxic, and the NPs have demonstrated improved biocompatibility for use in healthcare. This study evaluated the biogenic synthesis of AgNPs from the leaves of Cardamine hirsuta L. and their biological properties. The UV-Vis. spectra at 411 nm exhibited a distinct resonance spectrum for C-AgNPs produced from C. hirsuta L. FT-IR analysis exhibited the presence of functional groups of phyto-compounds of C. hirsuta responsible of silver salt reduction and capping agents of C-AgNPs. The microscopic-based study, such as HR-TEM analysis, showed that the particles were uniformly distributed, spherical, and ranged in size from 5.36 to 87.65 nm. EDX analysis confirmed a silver (Ag) content of 36.3% by weight, and XRD analysis exhibited the face-centred cubic (FCC) crystalline nature of C-AgNPs. DLS measured the mean particle size of 76.5 nm. The zeta potential was significant at −27.9 mV, and TGA analysis revealed that C-AgNPs had higher thermal stability. C-AgNPs demonstrated moderate antimicrobial activity against the tested pathogens. In addition, the anti-proliferative activity measured by the MTT assay on the Caco-2 cell line demonstrated decreased cell viability with increasing C-AgNPs dosage, with an IC₅₀ concentration of 49.14 µg/mL. In addition, an Annexin-V/Propidium iodide flow cytometric study was utilized to evaluate the induction of apoptosis in cancer cells. Early and late apoptosis cell populations increased significantly compared to the untreated control. Therefore, green-synthesized C-AgNPs have significant antimicrobial and anti-proliferative abilities, making them intriguing options for future biomedical applications. Full article

Herein we report the synthesis of organic selenide-based maleanilic and succinanilic acids in good yields (up to 95%). Their structural identities were elucidated by spectroscopic techniques (e.g., IR, ¹H- & ¹³C-NMR, and MS). The ADMET analysis, molecule electrostatic potential map, DFT, and frontier molecular orbital were used to study the organoselenium compounds’ pharmacokinetics, drug-likeness characteristics, geometries, and chemical and electronic properties. Moreover, a molecular docking tool was employed to investigate the organic selenides’ ability to inhibit the SARS-CoV-2 Mpro target (PDB: 7BFB). Within this context, organic selenides exhibited promising binding affinities to the SARS-CoV-2 Mpro receptor in the following order (12 > 11 > 10 > 9 > 7 > 8). Furthermore, molecular dynamics simulations were also carried out for 200 ns to evaluate the exact behavior of the most active compound (12) within the M^pro binding pocket of SARS-CoV-2 compared with its co-crystallized inhibitor (Co). Full article

Complexes of Schiff bases (SBs) with metals are promising compounds exhibiting a broad range of applications, such as catalysts, polymers, dyes, and several biological activities, including antimicrobial, anticancer, antioxidant, antimalarial, analgesic, antiviral, antipyretic, and antidiabetic actions. Considering the crisis that the whole world is now facing against antimicrobial-resistant bacteria, in the present review, we chose to focus on the activity of SBs as antimicrobials, particularly underlying the most recent studies in this field. Finally, some interesting catalytic applications recently described for metal complexes with SBs have also been discussed. Full article

Hydrolysis of light metals and hydrides can potentially be used for the generation of hydrogen on-board fuel cell vehicles, or, alternatively, for refilling their fuel tanks with H₂ generated and pressurised without compressor on site, at near-ambient conditions. Implementation of this approach requires solution of several problems, including the possibility of controlling H₂ release and avoiding thermal runaway. We have solved this problem by developing the apparatus for the controlled generation of pressurised H₂ using hydrolysis of Mg or MgH₂ in organic acid solutions. The development is based on the results of experimental studies of MgH₂ hydrolysis in dilute aqueous solutions of acetic, citric, and oxalic acids. It was shown that the hydrogen yield approaches 100% with a fast hydrolysis rate when the molar ratio acid/MgH₂ exceeds 0.9, 2.0, and 2.7 for the citric, oxalic, and acetic acids, respectively. In doing so, the pH of the reaction solutions after hydrolysis corresponds to 4.53, 2.11, and 4.28, accordingly, testifying to the buffer nature of the solutions “citric acid/magnesium citrate” and “acetic acid/magnesium acetate”. We also overview testing results of the developed apparatus where the process rate is effectively controlled by the control of the acid concentration in the hydrolysis reactor. Full article

The reactivity of the racemic N-heterocyclic stannylene [{MeHCN(^tBu)}Sn] (1) with the chalcogenide elements O₂, S, Se, and Te has been investigated. In the case of the reaction of 1 with molecular oxygen, the cyclic tristannoxane complex [{MeHCN(^tBu)}₂Sn(μ-O)]₃ (3) was isolated and characterised. NMR studies (¹H, ¹³C, and ¹¹⁹Sn) show the formation of D₃- and C₂- symmetric assemblies. The reaction of 1 with S, Se, and Te, respectively, yielded the cyclo-distannachalcogenide complexes, [{MeHCN(^tBu)}₂Sn(μ-E)]₃ (4: E = S, 5: E = Se, 6: E = Te), again with multinuclear NMR studies proving the formation of C₂- and C_s-symmetric assemblies. Single crystal X-ray diffraction studies have been used to elucidate the molecular structures of the products of oxidative addition, 3, 4, 5, and 6. Full article

A series of new lanthanide(III) coordination polymers with the general formula [Ln(btrm)₂(NO₃)₃]_n, where btrm = bis(1,2,4-triazol-1-yl)methane and Ln = Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, Gd³⁺ were synthesized and characterized by IR-spectroscopy, elemental, thermogravimetric, single-crystal, and powder X-ray diffraction analyses. Europium(III), samarium(III), terbium(III), and gadolinium(III) coordination polymers demonstrate thermal stability up to 250 °C, while dysprosium(III) is stable up to 275 °C. According to single-crystal X-ray diffraction analysis, the ligand exhibits a bidentate-bridging coordination mode, forming a polymeric chain of octagonal metallocycles. The photoluminescence of the free ligand in the polycrystalline state is observed in the ultraviolet range with a quantum yield of 13%. The energy transfer from the ligand to the lanthanide ions was not observed for all obtained coordination polymers. However, there are sharp bands of lanthanide(III) ions in the diffuse reflectance and excitation spectra of the obtained compounds. Therefore, Ln(III) luminescence arises, most probably, from the enhancement of f-f transition intensity under the influence of the ligand field and non-centrosymmetric interactions. Full article

High mass loading (ca. 30 mg/cm²) electrodes were prepared with carbon recovered from catalytic methane cracking (MC). As-fabricated supercapacitors displayed 74% of capacitance retention from 6 mA/cm² to 60 mA/cm² and a Ragone plot’s slope of −7 Wh/kW (compared to 42% and −31 Wh/kW, respectively, for high mass loading devices fabricated with commercial carbon). The high-rate capability of the MC-recovered carbon is attributed to the presence of carbon black and carbon nanotubes produced during the reaction, which likely increased the electronic and ionic conductivity within the electrode. These results suggest that the by-product of this hydrogen generation route might be a suitable active material for supercapacitors. Full article