Spectrophotometric simultaneous determination of cobalt, copper and nickel using nitroso-R-salt in alloys by partial least squares

Partial least squares modeling as a powerful multivariate statistical tool applied to spectrophotometric simultaneous determination of cobalt, copper, and nickel in aqueous solutions. The concentration range for cobalt, copper and nickel were 0.4-2.6, 0.6-3.4, 0.5-5.5 ppm, respectively. The experimental calibration set was composed with 36 sample solutions using a mixture design for three component mixtures. The absorption spectra were recorded from 470 to 600 nm. The effect of pH on the sensitivity and selectivity was studied according to net analyte signal (NAS). The values of root mean square difference (RMSD) for cobalt, copper and nickel using partial least squares (PLS) were 0.0192, 0.0263 and 0.0446 ppm, respectively. The effects of various cations and anions were investigated. The method was used to determination of cobalt, copper and nickel in two sample alloys based on copper, nickel and cobalt (known as cunico) and based on cobalt, nickel and iron (known as conife).     

Preparation of Reinforced poly (BisGMA-UDMA) Graphene-Based Nanocomposites Via Moderate in Situ SET-LRP

In the present study, cross-linked poly (dimethacrylate- urethane dimethacrylate) [poly (BisGMA-UDMA)] functionalized-graphene oxide nanosheets were prepared via single-electron transfer living radical polymerization (SET-LRP) using the ‘grafting from’ strategy, under mild conditions. This method first involves the covalent attachment of Br-containing groups onto the surface of grapheme sheets to give the initiating-groups-containing graphene (G-Br). After that, the succeeding SET-LRP polymerization in DMSO in the presence of a Cu wire/Me₆TREN catalytic system at room temperature leads to the grafting of poly (BisGMA-UDMA) chains onto the graphene surface. The resulting graphene-poly (dimethacrylate- urethane dimethacrylate) (G-PDMA-UDMA) nanocomposites were characterized using FT-IR, XRD, DSC, AFM, FE-SEM, and TEM analysis techniques. It was proved that polymer chains were successfully introduced to the surface of the graphene planes. After grafting with poly (BisGMA-UDMA), the dispersibility of the modified GO sheets significantly improved. When compared to G-PDMA, the resulting G-PDMA-UDMA nanocomposite revealed around 75%, 97%, and 65%, increase in compressive strength, Young's modulus and toughness, respectively. Such smart graphene-based nanocomposites can be used as promising biomaterials in orthopaedic and dental applications with the desired mechanical properties.     

Oxidative Desulfurization of Model Diesel Fuel by Vanadium Granular-Shape Mesoporous (V/GMS) Silica System as Nanocatalyst

The performance of V-containing granular-shape mesoporous (V/GSM) silica systems in oxidative desulfurization of model diesel fuel was studied. FTIR, XRD, SEM, TEM, N₂ adsorption-desorption, UV-Vis, and NH₃-TPD techniques were used to analyze the surface properties of the functionalized catalyst. The mesostructure of silica remains intact after vanadium modifications as shown by XRD and adsorption-desorption analysis, while spectroscopy indicates the successful impregnation of neat vanadium oxide inside the porous silica support. The oxidation desulfurization of model diesel fuel was effectively catalyzed by this catalyst and the highest activity was shown by 4.8% V/GSM catalyst. Compared with their conventional V/MCF and V/MCM-41 counterparts, SSM-supported vanadium catalysts showed much higher activity. This may be associated with the higher reducibility and better diffusion of reactants and products in V/MCF and V/MCM-41catalysts.     

A new Schiff-base as fluorescent chemosensor for selective detection of Cr3+: An experimental and theoretical study

A novel Schiff base fluorescent sensor N,N′-bis(salicylidene)-2,6-bis(4-aminophenyl)-4-phenylpyridine (P3) was synthesized through condensation of 2,6-bis(4-aminophenyl)-4-phenylpyridine and 2-hydroxybenzaldehyde. The obtained results from fluorescence analysis revealed that by excess of Cr³⁺ to P3, a remarkable increase was observed in the fluorescent intensity of the Schiff base at 663?nm with the ratio of CH₃CN/H₂O (95/5%), even though the other cations would likely have no impact on the fluorescence intensity. The cause of this trend might be ascribed to the formation of a 1:1 stoichiometric P3-Cr³⁺ complex, confirmed by Job's plot, which is resulted in preventing the photo-induced electron transfer (PET) process. From fluorescence titration, the association constant K_a was gained 2.28?×?10⁵?M^?1 and the limit of detection (LOD) was determined to be 1.3?×?10^?7?M. Furthermore, the optimized structure together with the electronic spectra of the proposed complex was determined by DFT and TDDFT calculations.     

Preparation of ion-imprinted polyvinyl sulfonate-grafted silica particles for trace enrichment of Th(IV) prior to determination by inductively coupled plasma-mass spectrometry

Grafting from polymerisation technique has been used to prepare Th(IV) ion-imprinted polyvinyl sulfonate (IIPVS)-bonded silica particles. The graft polymerisation of vinyl sulfonate (VS) on the surface of silica particles was achieved in aqueous medium through thermal decomposition of surface-bound azo initiators (60°C) in the presence of thorium ion. The prepared material was characterised by Fourier transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. The entrapped template ion was then removed using 2 M HCl. The experimental batch rebinding data were successfully described by the Langmuir–Freundlich model. The prepared material was then packed to a PTFE micro-column (20 mm × 3.0 mm, id) to evaluate its efficiency in column operations prior to determination by inductively coupled plasma-mass spectrometry (ICP-MS). The limit of detection of the method and breakthrough capacity of the column was evaluated as 0.074 µg L^?1 and 0.83 mg g^?1, respectively. The selectivity of the prepared polymer towards Th(IV) ion was investigated in the presence of some foreign competitor ions, including U(VI). Finally, the proposed method has been used to determine Th(IV) ion in real samples.     

钒掺杂的钛酸钠纳米管作为多相催化剂用于室温下硫化物的氧化

合成了一种含有TiO2, Na和V的多相纳米管催化剂,采用红外光谱、X射线衍射、扫描电镜、透射电镜和N2吸附-脱附法对该催化剂的结构和织构性质进行了表征,并用于水中30%H2O2选择性氧化硫化物制备对应的亚砜。该法具有产率极高、多相体系和简便等优点,可用于含一系列官能团底物的氧化,产物分离简便。     

The chemical behavior and degradation mitigation effect of cerium oxide nanoparticles in perfluorosulfonic acid polymer electrolyte membranes

Perfluorosulfonic acid membranes are susceptible to degradation during hydrogen fuel cell operation due to radical attack on the polymer chains. Mitigation of this attack by cerium-based radical scavengers is an approach that has shown promise. In this work, two formulations of crystalline cerium oxide nanoparticles, with an order of magnitude difference in particle size, are incorporated into said membranes and subjected to proton conductivity measurements and ex-situ durability tests. We found that ceria is reduced to Ce(III) ions in the acidic environment of a heated, humidified membrane which negatively impacts proton conductivity. In liquid and gas Fenton testing, fluoride emission is reduced by an order of magnitude, drastically increasing membrane longevity. Sideproduct analysis demonstrated that in the liquid Fenton test, the main point of attack is weak polymer end groups, while in the gas Fenton test, there is additional side-chain attack. Both mechanisms are mitigated by the addition of the ceria nanoparticles, whereby the extent of the concentration-dependent durability improvement is found to be independent of particle size.     

A new nano‐sized mononuclear Cu (II) complex with N,N‐donor Schiff base ligands: sonochemical synthesis,characterization, molecular modeling and biological activity

A new, simple Cu²⁺ nano‐structure Schiff base complex in methanol medium has been synthesized by the ultrasonic method. Structure of the compound was confirmed by FT‐IR, GC‐Mass and other spectroscopic techniques. The copper oxide (CuO) was achieved from the copper nano‐structure Schiff base complex as the raw material after calcination for 3 hr at 600 °C. According to results Cu²⁺ gives a complex with mole ratio 1:2 of metal to ligand (ML₂) with Schiff base which a distorted square planer is the most probable geometry for it. The calculations results from XRD patterns propose the nano‐sized complexes. The SEM images show morphology of both the copper complex and the CuO powder were plate‐like. The metal chelates of Cu²⁺ in two states of bulk and nano have been screened for their in vitro antibacterial activity against four bacteria, gram‐positive (Staphylococcus aureus) and gram‐negative (Escherichia coli) and three strains of fungus (Aspergillus flavus). The nano metal chelates were shown to possess more antibacterial activity than the bulk chelate. Finally, the empirical parameters of Schiff base compounds showed a good agreement with theoretical ones.     

Selective solid phase extraction of palladium by adsorption of its 5(p-dimethylaminobenzylidene)rhodanine complex on silica-PEG as a new adsorbent

The nickel(II) complex of a deoxyribonucleic acid (DNA-Ni²⁺) was directly electrodeposited on the surface of a glassy carbon electrode (GCE) to give a DNA-Ni/GCE electrode. It was investigated in terms of its capability of electro-oxidizing methanol in alkaline medium. It exhibits stable redox behavior of the Ni²⁺/Ni³⁺ couple by cyclic voltammetry. The DNA-Ni²⁺ membrane showed excellent electrocatalytic suitability for the electro-oxidation of methanol, is stable and responds reproducibly. The linear range for the detection of methanol in alkaline medium is from 8.0 µM to 2.4 mM, and the limit of detection is 2.0 µM (at a signal-to-noise ratio of 3).     

Unique substituted 3-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole-1-carboxamides generated by Ugi 3CC using bifunctional starting material

2-(2-Formyl-1H-benzimidazol-1-yl)acetic acid, as a bifunctional formyl-acid was prepared in four steps. This compound underwent one-pot reaction with primary amines, and alkyl isocyanides under Ugi conditions. A series of novel 3-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole-1-carboxamides were obtained in moderate to excellent yields.