Well-dispersed polyimide/TiO2 nanocomposites: in situ sol–gel fabrication and morphological study

In the presented study, 3,5-diamino-N-(4-methyl-1-oxo-1-(phenylamino)pentan-2-yl)benzamide (V) as a new diamine monomer is synthesized and fully characterized by means of FT-IR, ¹H-NMR, ¹³C-NMR, and elemental analysis techniques. The stated diamine is used for the sol–gel fabrication of a series of polyimide (PI)/titania nanohybrid films with various titania percentages. The special design of diamine monomer containing bulky pendant group increased the flexibility of resulted PI matrixes. On the other hand, the ability to construct strong organic/inorganic H-bond lattice has led to the effective surrounding of nanoparticles by PI grounds and thus the well-dispersed quite spherical nanoparticles were created via a sol–gel procedure. The obtained nanocomposites showed high thermal stability and UV–vis absorption efficiency. The X-ray diffraction experiments confirmed the titania nanoparticles to be amorphous.     

Trace Level Determination of Hydrogen Peroxide at a Carbon Ceramic Electrode Modified with Copper Oxide Nanostructures

An electrochemical sensor was developed for determination of hydrogen peroxide based on nanocopper oxides modified carbon sol‐gel or carbon ceramic electrode (CCE). The modified electrode was prepared by electrodeposition of metallic copper on the CCE surface and derivatized in situ to copper oxides nanostructures and characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques. The modified electrode responded linearly to the hydrogen peroxide (H₂O₂) concentration over the range 0.78–193.98 µmol L^?1 with a detection limit of 71 nmol L^?1 (S/N=3) and the sensitivity of 0.697 A mol^?1 L cm^?2. This electrode was used as selective amperometric sensor for determination of H₂O₂ contents in hair coloring creams.     

Heck-type reaction of aryldiazonium silica sulfates

Abstract  

Aryldiazonium silica sulfates were employed as new and efficient reagents for Heck-type arylation reactions with styrene and methyl acrylate. The reactions were carried out in an organic solvent, in the presence of Pd(OAc)₂ as precatalyst without use of base and free ligand. The trans isomers of desired products, methyl cinnamates and stilbenes, were obtained with full conversion. Use of a catalytic amount of Pd(OAc)₂ produced the corresponding products in short reaction times and excellent yields.     

One-pot polyamidation reaction of optically active aromatic diacid containing methionine and phthalimide moieties with aromatic diamines under microwave irradiation and traditional heating

An optically active diacid containing phthalimide and l-methionine moiety was prepared in three steps, and was polymerized with several aromatic diamines to obtain a new series of optically active polyamides (PAs) through direct polyamidation using triphenyl phosphite/pyridine/N-methyl-2-pyrrolidone/CaCl₂ system as condensing agent. The polymerization reactions were carried out under both conventional heating and microwave-assisted irradiation. The data obtained by these methods indicate that, high yields and similar inherent viscosities are resulted. It is worth to mention that in the case of microwave conditions, a drastic decrease in reaction time (3 min vs. 5 h) and cleaner reaction have been achieved. These polymers are readily soluble in polar organic solvents such as N,N-dimethyacetamide, N,N-dimethyformamide, dimethyl sulfoxide. The obtained polymers were characterized by FT-IR, specific rotation measurements, elemental analysis and ¹H NMR techniques. The thermal stability of the resulting PAs were evaluated with thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere which indicate they are moderately stable.     

Extraction of Anthocyanins from Borage (Echium amoenum) Flowers Using Choline Chloride and a Glycerol-Based,Deep Eutectic Solvent: Optimization,Antioxidant Activity,and In Vitro Bioavailability

Borage flower (Echium amoenum), an annual herb native to the Mediterranean region, is an excellent source of anthocyanins and is widely used in various forms due to its biological activities. In the present study, a choline chloride and glycerol (CHGLY)-based natural deep eutectic solvent (NADES) was applied in order to extract the anthocyanins from borage flowers. The traditional solvents, including water, methanol, and ethanol, were used to evaluate the efficiency of CHGLY. The results showed that CHGLY was highly efficient compared to the traditional solvents, providing the highest amounts of the total anthocyanin content (TAC), total phenolic content (TPC), total flavonoid content (TFC), individual anthocyanins, and antioxidant activity (DPPH radical scavenging (DPPH) and ferric-reducing antioxidant power (FRAP) assays). The most dominant anthocyanin found in studied borage was cyanidin-3-glucoside, followed by cyanin chloride, cyanidin-3-rutinoside, and pelargonidin-3-glucoside. The bioavailability % was 71.86 ± 0.47%, 77.29 ± 0.57%, 80.22 ± 0.65%, and 90.95 ± 1.01% for cyanidin-3-glucoside, cyanidin-3-rutinoside, by pelargonidin-3-glucoside and cyanin chloride, respectively. However, cyanidin-3-glucoside was the anthocyanin compound showing the highest stability (99.11 ± 1.66%) in the gastrointestinal environment. These results suggested that choline chloride and glycerol-based NADES is not only an efficient, eco-friendly solvent for the extraction of anthocyanins but can also be used to increase the bioavailability of anthocyanins.     

The effect of two-way coupling and inter-particle collisions on turbulence modulation in a vertical channel flow

Turbulence modulation due to its interaction with dispersed solid particles in a downward fully developed channel flow was studied. The Eulerian framework was used for the gas-phase, whereas the Lagrangian approach was used for the particle-phase. The steady-state equations of conservation of mass and momentum were used for the gas-phase, and the effect of turbulence on the flow-field was included via the standard k–ε model. The particle equation of motion included the drag, the Saffman lift and the gravity forces. Turbulence dispersion effect on the particles was simulated as a continuous Gaussian random field. The effects of particles on the flow were modeled by appropriate source terms in the momentum, k and ε equations. Particle–particle collisions and particle–wall collisions were accounted for in these simulations. Gas-phase velocities and turbulence kinetic energy in the presence of 2–100% mass loadings of two particle classes (50 μm glass and 70 μm copper) were evaluated, and the results were compared with the available experimental data and earlier numerical results. The simulation results showed that when the inter-particle collisions were important and was included in the computational model, the fluid turbulence was attenuated. The level of turbulence attenuation increased with particle mass loading, particle Stokes number, and the distance from the wall. When the inter-particle collisions were negligible and/or was neglected in the model, the fluid turbulence was augmented for the range of particle sizes considered.     

Preparation and characterization of poly(amide-imide)/ZnO nanocomposites containing pendent benzoxazole and benzimidazole segments

In the present investigation, novel poly(amid-imide)/zinc oxide nanocomposites (PAI/ZnO NCs) containing benzoxazole and benzimidazole pendent groups with different amounts of modified zinc oxide nanoparticles (ZnO NPs) were successfully prepared via the ex situ method. Poly(amid-imide) (PAI) was prepared by direct polycondensation of 2-[3,5- bis(N-trimellitimidoyl)phenyl]benzoxazole (DCA) with 5-(2-benzimidazole)-1,3-phenylenediamine (DAMI) and provided the polymeric matrix with well-designed groups. The surface of ZnO NPs was functionalized with 3-aminopropyltriethoxysilane (APS) coupling agent to have a better dispersion and enhancing possible interactions of NPs with functional groups of polymer matrix. The amount of APS bonded to the ZnO surface was determined by thermogravimetric analysis. PAI/ZnO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM analysis showed that the modified ZnO nanoparticles were homogeneously dispersed in polymer matrix. In addition, TGA data indicated an enhancement of thermal stability of the nanocomposite compared with the neat polymer.     

Study of the cyclotron production of <Superscript>172</Superscript>Lu: an excellent radiotracer

¹⁷²Lu due to its suitable (T _1/2 = 6.7 days) and high detection sensitivity, is used as a radiotracer in different fields. ¹⁷²Lu appears to be suitable as a long-lived rare-earth tracer for compound labelling and biodistribution studies. In the present study, excitation functions via ¹⁷²Yb(p,n)¹⁷²Lu, ^natYb(p,xn)¹⁷²Lu, ¹⁷²Yb(d,2n)¹⁷²Lu and ^natYb(d,xn)¹⁷²Lu reactions were calculated by ALICE/91, ALICE/ASH and TALYS-1.2 codes. Deposition of ^natYb₂O₃ on Cu substrate was carried out via sedimentation method for the production of ¹⁷²Lu. Cementation separation process and liquid–liquid extraction (LLX) of no-carrier-added (nca) radiolutetium from irradiated ytterbium(III)oxide target hydrochloric solution was described using Na(Hg) amalgam, α-hydroxyisobutyric acid (α-HIB) and di-(2-ethylhexyl)phosphoric acid (HDEHP).