Design, ‘one-pot’ synthesis,characterization, antibacterial and antifungal activities of novel 6-aryl-1,2,4,5-tetrazinan-3-thiones in dry media

A novel ‘one-pot’ synthesis of 6-aryl-1,2,4,5-tetrazinan-3-thiones is carried out by the three-component coupling of thiourea, various structurally diverse aromatic aldehydes and ammonium acetate in the presence of reusable NaHSO₄·SiO₂ heterogeneous catalyst in dry media under microwave irradiation. FT-IR, ¹H NMR, D₂O Exchange, HOMOCOR, ¹³C NMR, MS and elemental analysis characterize all the synthesized compounds. In vitro antibacterial/fungal activities are carried out for all the synthesized eight new compounds. All the compounds are more active against bacterial strains namely Staphylococcus aureus, β-Heamolytic streptococcus, Vibreo cholerae, Salmonella typhii, Shigella felxneri, Klebsiella pneumonia and Pseudomonas except compounds 1 and 6, while compound 6 shows promising activity against Salmonella typhii. Moreover, of all the compounds tested, compounds 3 and 8 are more effectual against all the tested fungal strains.     

Facile synthesis,antibacterial mechanisms and cytocompatibility of Ag–MnFe2O4 magnetic nanoparticles

Magnetic MnFe₂O₄ nanoparticles containing 0, 1 and 3 at.% silver, respectively were synthesized by one-pot sol-gel method for antibacterial applications in biomedical fields. Material characterizations indicate that MnFe₂O₄ begins crystallization at 134 °C and oxidation at 450 °C, the grain size and agglomeration degree increase with the silver content and silver exists as metallic state for the particles. The saturation magnetization decreases with the sintering temperature and slightly increases with the silver content, with the maximum of 50.0 emu/g obtained. Antibacterial tests by plate counting and PI-Hoechst 33342 staining suggest that the antibacterial activity of Ag–MnFe₂O₄ nanoparticles is silver content-dependent. Silver ions concentration measurement, β-galactosidase activity assay and transmission electron microscopic observation show that the antibacterial activity is dominated by the actions of the released silver ions, rather than the membrane cell impairment or reactive oxygen species-induced oxidative stress mechanism. MC3T3-E1 cell test demonstrates the best cytocompatibility of the nanoparticles with 3 at.% silver, which is likely related to the reduced cell endocytosis of the aggregated particles. The combination of magnetism, antibacterial activity and biocompatibility would make Ag–MnFe₂O₄ nanoparticles a potential multi-functional material in various biomedical applications.     

Design,Synthesis, in vitro and in silico Characterization of 2-Quinolone-L-alaninate-1,2,3-triazoles as Antimicrobial Agents

Due to the ever-increasing antimicrobial resistance there is an urgent need to continuously design and develop novel antimicrobial agents. Inspired by the broad antibacterial activities of various heterocyclic compounds such as 2-quinolone derivatives, we designed and synthesized new methyl-(2-oxo-1,2-dihydroquinolin-4-yl)-L-alaninate-1,2,3-triazole derivatives via 1,3-dipolar cycloaddition reaction of 1-propargyl-2-quinolone-L-alaninate with appropriate azide groups. The synthesized compounds were obtained in good yield ranging from 75 to 80 %. The chemical structures of these novel hybrid molecules were determined by spectroscopic methods and the antimicrobial activity of the compounds was investigated against both bacterial and fungal strains. The tested compounds showed significant antimicrobial activity and weak to moderate antifungal activity. Despite the evident similarity of the quinolone moiety of our compounds with fluoroquinolones, our compounds do not function by inhibiting DNA gyrase. Computational characterization of the compounds shows that they have attractive physicochemical and pharmacokinetic properties and could serve as templates for developing potential antimicrobial agents for clinical use.     

Design,synthesis, antibacterial and antifungal activity of novel spiro-isoxazolyl bis-[5,5′]thiazolidin-4-ones and spiro-isoxazolyl thiazolidin-4-one-[5,5′]-1,2-4 oxdiazolines

The synthesis of novel isoxazolyl 1,6-dithia-4,9-diazaspiro[4.4]nonane-3,8-diones (4a–h) and isoxazolyl 1-oxa-6-thia-2,4,9-triazaspiro[4.4]non-2-ene-8-ones (5a–h) analogs is described. Reaction of N-1-{3-methyl-5-[(E)-2-aryl-1-ethenyl]-4-isoxazolyl}-2-chloroacetamide (2) with aryl isothiocyanates yielded 3,3-methyl-5-[(E)-2-aryl-1-ethenyl]-4-isoxazolyl-2-(arylimino)-1,3-thiazolan-4-ones (3). Cyclocondensation of 3 with mercaptoacetic acid furnished novel isoxazolyl-1,6-dithia-4,9-diazaspiro[4.4]nonane-3,8-diones (4a–h). Cycloaddition of 3 with benzonitrile oxides afforded novel isoxazolyl 1-oxa-6-thia-2,4,9-triazaspiro[4.4]non-2-ene-8-ones (5a–h). Compounds 4a–h and 5a–h showed significant biological activity against all the standard strains.     

Synthesis and antibacterial activities of some 2-amino-4-(1,1′-biphenyl-4-yl)-6-aryl-6H-1,3-thiazines

A series of new 2-amino-4-(1,1′-biphenyl-4-yl)-6-aryl-6H-1,3-thiazines has been synthesized, characterized by IR, ¹H NMR, ¹³C NMR, mass and elemental analyses and evaluated for in vitro antibacterial activity against some Gram-positive and Gram-negative bacteria. The antibacterial data revealed that the compounds had better activity against tested organisms than the reference norfloxacin.     

Preparation and characterization of crednerite glass–ceramics in the MnO·CuO·SiO2 system

Nanoscale crednerite (CuMnO₂) was prepared in the system MnO·CuO·SiO₂, using glass–ceramics technique for the first time. Based on obtained data from differential thermal analysis (DTA), the prepared samples were heat-treated at 700 and 800 °C for 2 h. The presence of crystalline phases after and before heat treatment was investigated by X-ray diffraction analysis. Crystallization of crednerite (CuMnO₂), manganese silicate (Mn₂SiO₄) and traces of cuprite (Cu₂O) and cristobalite (SiO₂) phases were recognized. Transmission electron microscopy showed nanoscale crystals in the range 5–10 nm. The prepared glass–ceramics showed ferrimagnetic properties with wide range coercivity from 53 to 2217 Hci and magnetization saturation from 0.21708 to 1.2 emu/g. From IR reflection data; the reflection intensity of the light is high in the range of orange–red color and violet–blue colors and low in the range of green color.     

Heterogeneous synthesis of dimethylhexane-1,6-dicarbamate from 1,6-hexanediamine and methyl carbonate in methanol over a CeO2 catalyst☆

The efficient synthesis of dimethylhexane-1,6-dicarbamate (HDC) from 1,6-hexanediamine (HDA) and methyl carbonate over a series of heterogeneous catalysts (e.g., MgO, Fe2O3, Mo2O3, and CeO2) was invest...     

Facile synthesis of MgO–Mg2SiO4 composite ceramics with high strength and low thermal conductivity

The recycling of solid waste is a win-win solution for humans and nature. For this purpose, magnesite tailings and silicon kerf waste were employed to prepare MgO–Mg₂SiO₄ composite ceramics by solid-state reaction synthesis in the present work. Then, effects of sintering temperature and raw material ratio on as-prepared ceramics were systematically studied. As-prepared ceramics showed improvement in their relative density (from 47.55%–68.12% to 90.96%–95.25%) and cold compressive strength (from 7.34–118.66 MPa to 303.39–546.65 MPa) with the increase in sintering temperature from 1300 to 1600 °C. In addition, it was found that Si promoted synthesis process of Mg₂SiO₄ phase through transient liquid phase sintering and Fe₂O₃ accelerated sintering process through activation sintering. Consequently, the presence of Mg₂SiO₄ phase effectively improved the density and strength of MgO–Mg₂SiO₄ composite ceramic, while reducing its thermal conductivity. This work provides a potential reutilization strategy for magnesite tailings, and as-prepared products are expected to be applied in fields of construction, metallurgy, and chemical industry.     

Self-assembly synthesis of dumbbell-like MnPO4·H2O hierarchical particle and its application in LiMnPO4/C cathode materials

The large-scale and efficient synthesis of MnPO₄·H₂O is an urgent problem to be solved. In this paper, self-assembled dumbbell-shaped MnPO₄·H₂O particles were successfully synthesized just using KMnO₄ and commercial concentrated H₃PO₄, and then employed as the precursor to prepare LiMnPO₄/C composites. The XRD, SEM, TEM, and electrochemical performance tests were used to investigate MnPO₄·H₂O and the corresponding LiMnPO₄/C. The formation mechanism of MnPO₄·H₂O was discussed. The results showed that temperature and water content have a significant effect on the yield, purity, and morphology of MnPO₄·H₂O. The synthesized LiMnPO₄/C with reduced carbon content at 650 °C delivered a discharge capacity of 109.3 mA h g^-1 at 1 C and 104.3 mA h g^-1 at 2 C. This green and efficient synthesis method of MnPO₄·H₂O provides a new idea for the large-scale preparation of LiMnPO₄/C cathode materials.     

Porous β-Ca2SiO4 ceramic scaffolds for bone tissue engineering: In vitro and in vivo characterization

The biodegradable ceramic scaffolds with desirable pore size, porosity and mechanical properties play a crucial role in bone tissue engineering and bone transplantation. A novel porous β-dicalcium silicate (β-Ca₂SiO₄) ceramic scaffold was prepared by sintering the green body consisting of CaCO₃ and SiO₂ at 1300 °C, which generated interconnected pore network with proper pore size of about 300 μm and high compressive strength (28.13±5.37–10.36±0.83 MPa) following the porosity from 53.54±5.37% to 71.44±0.83%. Porous β-Ca₂SiO₄ ceramic scaffolds displayed a good biocompatibility, since human osteoblast-like MG-63 cells and goat bone mesenchymal stem cells (BMSCs) proliferated continuously on the scaffolds after 7 d culture. The porous β-Ca₂SiO₄ ceramic scaffolds revealed well apatite-forming ability when incubated in the simulated body fluid (SBF). According to the histological test, the degradation of porous β-Ca₂SiO₄ ceramic scaffolds and the new bone tissue generation in vivo were observed following 9 weeks implantation in nude mice. These results suggested that the porous β-Ca₂SiO₄ ceramic scaffolds could be potentially applied in bone tissue engineering.     

‘Green’ synthesis of silver polymer Nanocomposites of poly (2-isopropenyl-2- oxazoline-co- N-vinylpyrrolidone) and its catalytic activity

Metal-polymer nanocomposites are of great interest and mainly focused on advanced catalytic and sensor applications. Resulting from this, new copolymers composed of poly(2-isopropenyl-2-oxazoline) (PIPOx) and poly(N-vinylpyrrolidone) (PNVP) segments were prepared from highly water soluble 2-isopropenyl-2- oxazoline (IPOx) and N-vinylpyrrolidone (NVP) monomers. Finally, silver polymer nanocomposites of poly(2-isopropenyl-2-oxazoline-co-N-vinylpyrrolidone) were synthesized and reporting for the first time. All polymerizations were done in an aqueous phase with potassium persulfate as an initiator at 60 °C. The reaction time varied from 1 to 6 h in accordance with stoichiometric ratios of PIPOx and PNVP, leading to insoluble copolymers; which are termed as PIPOx_PNVP (75:25), PIPOx_PNVP (50:50), PIPOx_PNVP (25:75) and PIPOx_PNVP (10:90). Only, PIPOx_PNVP (10:90) showed adequate swelling behavior in water and some other organic solvents. All the polymers were distinguished by various physicochemical spectroscopic techniques such as UV/Visible spectroscopy, Scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and FTIR analysis. Thermogravimetry (TGA) and Differential scanning calorimetry (DSC) were used to investigate thermal stability of the samples. The metalo-polymer nanocomposites (PIPOx_PNVP-SNCs) showed an apparently improved stability even when the composites were stored in air, at room temperature. The PIPOx_PNVP-SNCs showed a remarkable catalytic activity during the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride.     

Properties of liquid CaO–SiO2 and CaO–SiO2-‘Fe2O3’tot slags measured by a combination of maximum bubble pressure and rotating bob methods

Liquid slag properties are essential for understanding complex mass and momentum phenomena in metallurgical operations. The density, surface tension and viscosity were measured in six silicate-rich slags of the CaO–SiO₂ and CaO–SiO₂-‘Fe₂O₃’_tot systems by combining the maximum bubble pressure and rotating bob methods. The properties investigated were sensitive to the temperature, SiO₂ and Fe₂O₃ contents. Different experimental trends were derived due to the amphoteric properties of Fe₂O₃. The slags with ferric oxide were denser than the silicate melts. Surface tension gradually decreased with temperature and indicated firstly a rise and then decline with further Fe₂O₃ addition. Raman spectra were analyzed to provide structural information of the polymer melt and indicated an enhancement in the polymerization degree with Fe³⁺. The derived experimental trends and role of Fe³⁺ in the silicates were attributed to the interplay of complex factors: different bonding in the melt, cation interactions and the oxidation state of iron. The influence of Fe³⁺/Fe²⁺ on the melt properties was discussed.     

Formation of O‘—Sialon Matrix and Microstructure Development in the Refractory of Si3N4—SiO2—ZrO2—Al2O3 System

An O‘-Sialon-Al2O3 composite refractory was prepared by in situ reaction of Si3N4-ZrSiO4-Al2O3 mixture with fused alumina aggregates.Densification,in situreaction procedure and microstructure of the material were investigated by means of X-ray diffraction,optical and scanning electronic microscopes and EDAX.     

Hydrothermal synthesis and characterization of nanorods “LixV2−δO4−δ·H2O”

Nanorods “Li_xV_2−δO_4−δ·H₂O” were hydrothermally synthesized with starting agents LiOH·H₂O and V₂O₅, and reducing agent hydrazine monohydrate (NH₂NH₂·H₂O) under alkaline condition at 160 °C. The samples were characterizated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The nanorods obtained have diameters from 80 to 100 nm with length up to several micrometers. Molecular coordination and assembly mechanism can be assumed to explain the formation of one-dimensional nanorods.     

Characterisation of carbon deposits on Ni/SiO2 in the reforming of CH4–CO2 using fixed- and fluidised-bed reactors

CO₂ reforming of methane was investigated with regard to carbon deposition on 4.5 wt% NiO/SiO₂ catalyst at 1023 K, 1 atm and a CH₄/CO₂ ratio of 1.0 employing micro-fluidised- and fixed-bed reactors. A higher catalytic activity (by 20%) was observed in the initial stage (0.5 h) of the fluidised-bed reforming which may be attributed to lesser deactivation of the catalyst compared to fixed-bed operation. Only a limited amount of carbon was deposited in a period of 11 h on stream. In the case of the fixed-bed reactor, a much larger amount of carbon was found on the spent catalyst, particularly, when sampled from the bottom of the bed. TPO results suggest that carbon deposits on the catalyst samples from the fluidised-bed as well as the top of the fixed-bed are rather small and of similar nature. The carbon deposited at the bottom of the fixed-bed reactor contained two distinct species according to XPS results (corresponding to C–O and C–C bonds).     

Raman characterization and photoluminescence properties of La1-xTbxPO4·nH2O and La1-xTbxPO4 phosphor nanorods prepared by microwave-assisted hydrothermal synthesis

The effect of the Tb³⁺–doping content (in the range 0–100 mol%) on the structure (using Raman spectroscopy) and photoluminescence (PL) properties of both rhabdophane-type La_1-xTb_xPO₄·nH₂O and monazite-type La_1-xTb_xPO₄ single-crystal nanorods was investigated. La_1-xTb_xPO₄·nH₂O was directly obtained by microwave-assisted hydrothermal synthesis and La_1-xTb_xPO₄ by calcination of La_1-xTb_xPO₄·nH₂O at 700 °C in air for 2 h. It was found that the characteristic Raman bands shift to higher wavenumbers and become broader with increasing Tb³⁺ concentration, which is attributed to attendant unit-cell volume reduction. The PL due to the Tb³⁺ f-f transitions has been studied with continuous and pulsed excitations. The PL intensity increases with doping and is maximum for La_0.80Tb_0.20PO₄·nH₂O and La_0.85Tb_0.15PO₄, i.e., for rhabdophane and monazite-type structures, respectively. A quenching effect is detected for concentrations below x=0.05, but constant efficiency is obtained at higher doping. The calcination increases the efficiency by a factor around 2 due to the combined effects of water molecules and defect elimination. The PL decay curves reveal a long lifetime attributable to single Tb³⁺ ions which is almost independent of doping for monazite nanorods (5–4.5 ms), and a shorter one around 0.2 ms most likely due to Tb³⁺ dimmers.