One-pot synthesis of xanthene derivatives under solvent-free conditions

One-pot synthesis of aryl-14H-dibenzo[a,j]xanthene and 1,8-dioxo-octahydroxanthene derivatives using montmorillonite K10 as reusable eco-friendly catalyst under solvent-free conditions is described.     

Synthesis,structure and mechanical properties of nanocomposites based on exfoliated nano magnesium silicate crystal and poly(acrylamide)

In this study, hydrolyzed polyacrylamide based nanocomposite (HPAM-NC) hydrogels crosslinked by chromium (III) acetate, was synthesized using free radical polymerization. The introduction of magnesium silicate nanocrystals (MSNCs) into the hydrolyzed polyacrylamide (HPAM) network endows the system with enhanced mechanical properties. The successful formation and crystalline behavior of HPAM-NC hydrogels was verified by Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diffraction (XRD) analyses. Field-Emission Scanning Electron Microscopy (FESEM) and rheology tests showed that the morphology and mechanical properties of HPAM-NC hydrogels were strongly influenced by different content of parameters including concentration of copolymer, nanoparticle and cross-linker. The results showed that this nanocomposite hydrogel is a moldable material so it can expand its application as value-added product.     

A novel magnetically separable laccase-mediator catalyst system for the aerobic oxidation of alcohols and 2-substituted-2,3-dihydroquinazolin-4(1H)-ones under mild conditions

In this study, a magnetically reusable artificial metalloenzyme has been constructed by co-immobilization of palladium nanoparticles as a strong oxidizing catalyst and laccase as an oxygen-activating enzyme into the cavities of magnetic mesocellular foams silica (Pd-Laccase@MMCF). The combination of Pd-Laccase@MMCF and hydroquinone (HQ) act as electron-transfer mediator system and make stepwise electron transfer from substrate to molecular oxygen. This catalyst system was used for the aerobic (i) oxidation of alcohols to the corresponding carbonyl compounds and (ii) dehydrogenation of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones in phosphate buffer (0.1 M, pH 4.5, 4 mL)/THF (4%, 1 mL) as solvent under mild conditions. The co-immobilization of both laccase and Pd onto high surface area mesoporous support, high catalytic activity and magnetically separable and reusable make the present catalyst system superior to other currently available electron-transfer mediator systems.     

Determination of Deltamethrin in Water Samples Using Sulfur and Nitrogen Co-Doped Carbon Quantum Dots as a Chemiluminescence Probe

Journal of Analytical Chemistry - The application of sulfur and nitrogen co-doped carbon quantum dot?potassium permanganate chemiluminescence (CL) system for the determination of trace...     

Silicon and porous silicon mid-infrared photonic crystals

A 3D silicon micromachining method based on proton beam writing combined with electrochemical anodization of p-type silicon enables fabrication of mid-infrared photonic crystals made of silicon and porous silicon. Here, example structures of silicon 1D and 2D photonic crystals are demonstrated. Progress and problems of fabricating 3D photonic crystals made of silicon are discussed. The strategy of fabricating photonic crystals purely made of porous silicon, and the characterization method of all these mid-infrared structures, are discussed. Due to the flexibility of this fabrication method, photonic devices and integrated photonic circuits may be built on a single chip, for which two 2D silicon photonic crystals with one on top of the other are demonstrated.     

Clean synthesis and antibacterial activities of spiro[pyrimido[4,5-b]quinoline-5,5'-pyrrolo[2,3-d]pyrimidine]-pentaones

A simple, clean and efficient method for the synthesis of spiro[pyrimido[4,5-b]quinoline-5,5'-pyrrolo[2,3-d]pyrimidine]-pentaone derivatives by condensation reaction of 6-amino-uracils and isatins in aqueous media is reported. These products were evaluated in vitro for their antibacterial activities.     

Corrosion inhibition of 302 stainless steel with schiff base compounds

The effects of 2,2′-[bis-N(4-cholorobenzaldimin)]-1,1′-dithio (BCBD) and bis-(2-aminophenyl) disulphide (BAPD) on the corrosion behavior of 302 stainless steel in 0.5 M sulfuric acid solution as corrosive medium were investigated using weight loss and potentiostatic polarization techniques. Some corrosion parameters such as anodic and cathodic Tafel slopes, corrosion potential, corrosion current density, surface coverage degrees and inhibition efficiencies were calculated. The polarization measurements indicated that the inhibitors were of mixed type which inhibited corrosion by parallel adsorption on the surface of stainless steel due to the presence of more than one active centre in the inhibitor molecule. The adsorption followed Langmuir adsorption isotherm. The activation energy and thermodynamic parameters were calculated at different temperatures. Results showed that BCBD had a higher inhibition efficiency compared with BAPD.     

A class of Banach sequence spaces analogous to the space of Popov

Hagler and the first named author introduced a class of hereditarily l ₁ Banach spaces which do not possess the Schur property. Then the first author extended these spaces to a class of hereditarily l _p Banach spaces for 1 ⩽ p < ∞. Here we use these spaces to introduce a new class of hereditarily l _p (c ₀) Banach spaces analogous of the space of Popov. In particular, for p = 1 the spaces are further examples of hereditarily l ₁ Banach spaces failing the Schur property.     

Environmentally friendly synthesis of Ag/SiO2 nanoparticles using Thymus kotschyanus extract and its application as a green catalyst for synthesis of spirooxindoles

Today, plant extracts based on synthetic procedures have drawn consideration over conventional methods like physical and chemical procedures to synthesize nanomaterials. Green synthesis of nanomaterials has become an area of interest because of numerous advantages such as non-hazardous, economical, and feasible methods with a variety of applications in biomedicine, nanotechnology and nano-optoelectronics and as catalysts for various organic transformations. In this research, silver nanoparticles were deposited on the surface of nano-silica spheres by an in-situ reduction of Ag⁺ ions using an aqueous extract of Thymus kotschyanus aerial parts as a natural reducing and a capping agent. The result recorded from ultraviolet–visible (UV–Vis) spectrometer, Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS) and X-ray powder diffraction supports the biosynthesis and characterization of Ag/SiO₂ nanoparticles. The results indicated that the average size of Ag/SiO₂ nanoparticles is 25–60 nm. The Ag/SiO₂ nanoparticles act as an environmentally friendly heterogeneous catalyst in the synthesis of spirooxindoles via the three-component condensation reaction of isatins, activated methylene reagents, and 1,3-dicarbonyl compounds in aqueous media, and the desired products were obtained with yields ranging from 90 to 98%. The catalyst can be recovered easily and used repetitively without significant loss of catalytic activity.

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