Two-dimensional surface properties of 2-methoxy ethyl oleate at the air/water interface

Methoxy ethyl oleate, a nonionic surfactant, has been investigated at the air/water interface for various surface properties by employing the Langmuir film balance technique. The ester forms an expanded isotherm at the air/water interface. The minimum area of packing (A ₀), initial area of increase of surface pressure (A _i ), collapse pressure (π _c ), and area/molecule at collapse pressure (A _c ) have been estimated from the isotherm curve.The higher compressibility coefficient (K) suggests that the ester forms a more expanded liquid film than the parent oleic acid. Besides, the ester film is fairly stable as suggested by only about 30% loss in area over a period of 20 min. The relaxation rates of the ester film at different surface pressures of 10, 15, and 20 mN·m^?1 have been estimated from changes in the surface area/molecule with time. Interestingly, the surface area (54.2 Ų/molecule) that corresponds to a minimized structure projected for the ester, calculated theoretically, agrees reasonably well with the experimental value (57.2 Ų/molecule).     

Ammonium hydrogen difluoride induced fluorination of hydroxyapatite

Ammonium hydrogen difluoride (NH₄HF₂) was used as a fluorinating agent for the fluorination of hydroxyapatite. The process was carried out at room temperature by pH cycle method, at 80 °C by reflux method and at 900 °C by solid state reaction. The products obtained in all the three methods were analyzed by powder XRD and FT-IR techniques to confirm fluorination. FT-IR spectra showed the decrease in the intensity of ‘OH’ stretching band at 3571 cm⁻¹ and complete disappearance of ‘OH’ bending band at 632 cm⁻¹. Appearance of a new peak at around 740 cm⁻¹ (due to the formation of .H-F. bond) was observed in all the spectra. Similarly, powder XRD patterns exhibited higher angle shift in 2θ values of high intense peaks associated with (300), (112) and (211) planes when compared to parent hydroxyapatite. Both the structural and spectroscopic analyses confirmed partial fluorination of hydroxyapatite.     

Synthesis of poly(4, 4′-biphenylene sulfonyl succinamide)-polysulfone blend membranes for removal of toxic metal ions from water

A novel polymer poly(4,4′-biphenylene sulfonyl succinamide) (PBSS) was synthesized via polycondensation reaction. Succinyl chloride and 4-aminophenyl sulfone were used as reactive monomers and anhydrous AlCl₃ was used as a catalyst. Both polysulfone (PSf) and PBSS were dissolved in N-methyl-2-pyrrolidone (NMP) at different compositions to obtain a homogeneous solution to fabricate PSf-PBSS blend membranes. The structure of PBSS was characterized by ATR-IR and ¹H-NMR spectroscopy. Thermal properties of PBSS were analyzed by TGA-DTA. Mechanical properties and morphology of blend membranes were analyzed by universal testing machines and field emission scanning electron microscope, respectively. The hydrophilicity of blend membranes with respect to the concentration of PBSS was studied by contact angle and water uptake studies. Upon blending, the hydrophilicity of PSf-PBSS membranes drastically increased due to the presence of large number of amide and sulfonyl groups in the matrix. The blend membranes exhibited significant increase in water flux from 100 L m⁻² h to 650 L m⁻² h⁻¹, and rejection of 100% for Pb(II) and 80% for both Cd(II) and As(III) toxic heavy metal ions. The hydrophilic nature of  CO NH and inter and intramolecular hydrogen bonding among PBSS polymer chains dispersed within rigid PSf matrix imparts softness, amide and sulfonyl groups enhance interconnected porosity and hydrophilicity of blend membranes. Hence, PBSS may serve as a low-cost novel polymeric additive for water purification and separation membrane applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48254.     

Heterocyclic modification of chitosan for the adsorption of Cu (II) and Cr (VI) ions

A heterocyclic modification of chitosan has been attempted for development of an effective adsorbent material for removal of metal ions. The modified polymer was characterized using infrared (IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) techniques. The adsorption capacity exhibited for Cu (II) and Cr (VI) were 83.75 and 85.0 mgg^?1, respectively, which is a significant improvement over chitosan. The adsorption on the modified polymer was a second-order kinetic process and followed Langmuir isotherm model. The thermodynamic analysis indicated exothermic and spontaneous nature of adsorption. About 80% of the adsorbed metal ions were desorbed in appropriate stripping solutions indicating reusability.     

Modification of highly brittle polystyrene sulfonic acid-co-maleic acid crosslinked sodium alginate membrane into flexible membranes by the incorporation of dibutyl phthalate as a plasticizer for pervaporation separation

To convert highly brittle into flexible membrane, the polystyrene sulfonic acid-co-maleic acid crosslinked sodium alginate (PSSAMA/NaAlg) membrane was modified by incorporating the different weight% of dibutyl phthalate (DBP) as a plasticizer. The effect of DBP content on the physico-chemical properties of the membranes was thoroughly examined. The membranes exhibited lower glass transition temperatures with increasing the plasticizer content in the matrix of PSSAMA/NaAlg. The separation performance of the membranes for water/isopropanol and water/1,4-dioxane was studied at different temperatures. Among the modified membranes, the membrane containing 6 wt% of DBP exhibited the highest separation factors of 24,129 with a flux of 13.57 × 10⁻² kg/m² hr and 23,353 with a flux of 12.99 × 10⁻² kg/m² hr for water/isopropanol and water/1,4-dioxane at 30°C, respectively. From the temperature-dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The estimated activation energy values for permeation of water (E_pw) and isopropanol (E_pIPA) were, respectively, ranged between 12.09 and 8.79, and 42.52 and 32.79 kJ/mol. A negative heat of sorption (ΔH_s) values was obtained for all the membranes, suggesting that Langmuir's mode of sorption was predominant. Based on the results, it is concluded that the modified membranes demonstrated excellent pervaporation performance for the separation of water/isopropanol and water/1,4-dioxane.     

Pd/Fe3O4 supported on bio-waste derived cellulosic-carbon as a nanocatalyst for C–C coupling and electrocatalytic application

The current work describes the synthesis of a new bio-waste derived cellulosic-carbon supported-palladium nanoparticles enriched magnetic nanocatalyst (Pd/Fe₃O₄@C) using a simple multi-step process under aerobic conditions. Under mild reaction conditions, the Pd/Fe₃O₄@C magnetic nanocatalyst demonstrated excellent catalytic activity in the Hiyama cross-coupling reaction for a variety of substrates. Also, the Pd/Fe₃O₄@C magnetic nanocatalyst exhibited excellent catalytic activity up to five recycles without significant catalytic activity loss in the Hiyama cross-coupling reaction. Also, we explored the use of Pd/Fe₃O₄@C magnetic nanocatalyst as an electrocatalyst for hydrogen evolution reaction. Interestingly, the Pd/Fe₃O₄@C magnetic nanocatalyst exhibited better electrochemical activity compared to bare carbon and magnetite (Fe₃O₄ nanoparticles) with an overpotential of 293 mV at a current density of 10 mA·cm^–2.     

Ni–Pt/H–Y Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene

Ni–Pt/H–Y zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250–400 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl₂O₄. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH₃-TPD and pyridine-adsorbed FT–IR spectroscopy show the increasing occupation of acid sites by increasing nickel loading. The catalytic activity of Ni–Pt/H–Y zeolite and Pt/H–Y catalysts was compared and it was found that addition of Ni up to 0.3 wt.% increases conversion of toluene and 1,2,4-trimethylbenzene, disproportionation selectivity and sustainability of the catalysts. Further addition of Ni leads to a decrease in conversion and disproportionation selectivity and increasing dealkylated products, which may be due to the presence of unreduced Ni species and pore blockage by large-sized bimetallic particles formed.     

Improved method to graft polyaniline on E‐glass fabric to enhance its electronic conductivity

A method to enhance the electronic conductivity of polyaniline grafted E‐glass fabric is described. The influence of substituted aromatic sulfonic acids as primary dopants on conductivity of the grafted polyaniline–E‐glass fabrics is studied. The conducting fabrics obtained in this method were characterized by UV‐vis spectroscopy, scanning electron microscopy, X‐ray diffraction study, thermogravimetric analysis, and conductivity. Shielding effectiveness measurements on these Pan–E‐glass fabrics showed that the performance is improved (i.e., 0.01 MHz = 49 dB, 1000 MHz = 7 dB) compared to earlier studies (i.e., 0.05 MHz = 37 dB, 1000 MHz = 1 dB) without pretreatment of fabrics. Possible application of these fabrics, e.g., for dissipation of electrostatic charge, is suggested. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2316–2323, 2005     

Properties of scaffolds based on chitosan and collagen with bioglass 45S5

Scaffolds based on chitosan (CTS), collagen (Coll) and glycosaminoglycans (GAG) mixtures cross‐linked by tannic acid (TA) with bioglass 45S5 addition were obtained with the use of the freeze‐drying method. The prepared scaffolds were characterised for morphology, mechanical strength and degradation rate. Moreover, cell viability on the obtained scaffolds was measured with and without the presence of ascorbic acid and dexamethasone. The main purpose of the research was to compare the effectiveness of bioglass 45S5 influence on the physicochemical and biological properties of scaffolds. The results demonstrated that the scaffolds based on the blends of biopolymers cross‐linked by TA are stable in an aqueous environment. Scanning electron microscope images allowed the observation of a porous scaffold structure with interconnected pores. The addition of bioglass nanoparticles improved the mechanical properties and decreased the degradation rate of composite materials. The biological properties were improved for 20% tannic acid addition compared to 5%. However, the addition of bioglass 45S5 did not change to cells response significantly.Inspec keywords: biomedical materials, drying, porous materials, freezing, tissue engineering, proteins, nanofabrication, bone, scanning electron microscopy, polymers, molecular biophysics, cellular biophysics, nanoparticles, porosityOther keywords: chitosan, collagen, glycosaminoglycans, bioglass 45S5 addition, freeze‐drying method, degradation rate, ascorbic acid, dexamethasone, physicochemical properties, biological properties, porous scaffold structure, bioglass nanoparticles, mechanical properties, tannic acid addition, scanning electron microscopy     

Do Images of Biskyrmions Show Type‐II Bubbles?

The intense research effort investigating magnetic skyrmions and their applications for spintronics has yielded reports of more exotic objects including the biskyrmion, which consists of a bound pair of counter‐rotating vortices of magnetization. Biskyrmions have been identified only from transmission electron microscopy images and have not been observed by other techniques, nor seen in simulations carried out under realistic conditions. Here, quantitative Lorentz transmission electron microscopy, X‐ray holography, and micromagnetic simulations are combined to search for biskyrmions in MnNiGa, a material in which they have been reported. Only type‐I and type‐II magnetic bubbles are found and images purported to show biskyrmions can be explained as type‐II bubbles viewed at an angle to their axes. It is not the magnetization but the magnetic flux density resulting from this object that forms the counter‐rotating vortices.