Fractionation of Soybean Globulins Using Ca<Superscript>2+</Superscript> and Mg<Superscript>2+</Superscript>: A Comparative Analysis

The substitution of CaCl₂ by MgCl₂ was undertaken in Deak’s two-step process of separating the soybean 11S and 7S globulins, aiming at higher purities and lower phytic acid (PA) contents of recovered protein fractions. The effects of pH and the addition of NaCl were also evaluated. Compared with CaCl₂, MgCl₂ reduced the PA content of the 11S-rich fraction by 63–71% but increased that of the 7S-rich fraction by 14–28%, depending on pH. Correspondingly, more Ca²⁺ was recovered in the 11S-rich fraction, while more Mg²⁺ co-precipitated with the 7S-rich fraction. NaCl increased the purity of the 11S-rich fraction and reduced its PA content, but the purity of the 7S-rich fraction was reduced by using 50–100 mM NaCl. Lowering pHs from 6.4 and 4.8 to 5.6 and 4.0 in the two precipitation steps increased the yield of both fractions. The optimized fractionating procedure was as follows: the 11S-rich fraction was precipitated at pH 5.8 by using 5 mM MgCl_2, 10 mM NaHSO₃ and 20 mM NaCl, followed by the precipitation of the 7S-rich fraction at pH 4.5. The new method provided both fractions with satisfactory protein yields (22% for 11S and 16% for 7S), purities (88% for 11S and 80% for 7S) and PA contents (0.356% for 11S and 0.882% for 7S).     

Effect of Ni<Superscript>2+</Superscript>, V<Superscript>4+</Superscript> and Mo<Superscript>6+</Superscript> concentration on iron oxidation by <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis>

The ferrous oxidation ability of Acidithiobacillus ferrooxidans was studied in the presence of Ni²⁺, V⁴⁺ and Mo⁶⁺ in 9 K media in order to implement the culture in the bioleaching of spent catalyst. The rate of iron oxidation decreased with increasing concentration of metal ions, but the rate of inhibition was metal-ion dependent. The tolerance limit was critical at a concentration of 25 g/L Ni²⁺, 5 g/L V⁴⁺ and 0.03 g/L Mo⁶⁺. The growth rate of microorganisms was negligible at concentrations of 6 g/L V⁴⁺ and 0.04 g/L Mo⁶⁺. Levels and degree of toxicity of these ions have been quantified in terms of a toxicity index (TI). The toxicity order of metal ions was found to be Mo⁶⁺>V⁴⁺>Ni²⁺. The significance and relevance of multi-metal ion tolerance in Acidithiobacillus ferrooxidans has been highlighted with respect to bioleaching of spent refinery catalyst.     

Morphology and photoluminescence properties of phenolic epoxy resin coating on KH550-modified SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>: Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript> powder in the presence of triarylsulfonium hexafluoroantimonate

In this study, the amino silane coupling agent (KH550)-modified SrAl₂0₄: Eu²⁺, Dy³⁺ phosphor powder coated with phenolic epoxy resin (EOCN) in the presence of triarylsulfonium hexafluoroantimonate catalyst was prepared using the combination of organic–inorganic composite dip-coating and UV curing coating methods. The results of SEM, TEM, and FTIR showed that the organic coating was a layer of compact membrane with a thickness of 20–50 nm, which can be named silane-modified epoxy monomer generated by the KH550 and the EOCN. Furthermore, it was observed that afterglow and spectrum properties of the coated phosphor powder had good long-afterglow luminescence properties, and revealed two emission peaks at 435 nm and 520 nm under the same excitation wavelength of 360 nm, respectively. More interesting, the emitting color of the coated sample was located in the area of cyan light on CIE1931 chromaticity diagram, which led to a slight blue shift rather than the yellow–green color of the pure SrAl₂0₄: Eu²⁺, Dy³⁺ phosphor powder.     

Visible up-conversion luminescence of CaWO<Subscript>4</Subscript>: Er<Superscript>3+</Superscript>,Yb<Superscript>3+</Superscript> and emission enhancement by tri-doping of Li<Superscript>+</Superscript> ions

Er³⁺,Yb³⁺ co-doped CaWO₄ polycrystalline powders were prepared by a solid-state reaction and their up-conversion (UC) luminescence properties were investigated in detail. Under 980 nm laser excitation, CaWO₄: Er³⁺,Yb³⁺ powder exhibited green UC emission peaks at 530 and 550 nm, which were due to the transitions of Er³⁺ (²H_11/2)→Er³⁺ (⁴I_15/2) and Er³⁺ (⁴S_3/2)→Er³⁺ (⁴I_15/2), respectively. Effects of Li+ tri-doping into CaWO₄: Er³⁺,Yb³⁺ were investigated. The introduction of Li⁺ ions reduced the optimum calcinations temperature about 100 °C by a liquid-phase sintering process and the UC emission intensity was remarkably enhanced by Li⁺ ions, which could be attributed to the lowering of the symmetry of the crystal field around Er³⁺ ions.     

Effects of adding B<Subscript>2</Subscript>O<Subscript>3</Subscript> as a flux on phosphorescent properties in synthesis of SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>: (Eu<Superscript>2+</Superscript>, DY<Superscript>3+</Superscript> phosphor

SrAl₂O₄: (Eu²⁺, Dy³⁺) phosphor was prepared by solid state reaction. B₂O₅ as a flux was added in SrAl₂O₄:(Eu ²⁺, Dy³⁺) in order to accelerate a solid state reaction. In this paper, the effects of B₂O₃ on the crystal structure and the phosphorescent properties of the material have been evaluated. The synthesized phosphor exhibited a broad band emission spectrum peaking at 520 nm, and the spectrum peak showed little effect by the B₂O₃ contents. The maximum afterglow intensity of the SrAl₂O₄: (Eu²⁺, Dy³⁺) phosphor was obtained at the B₂O₃ content of 5%. Adding the B₂O₃ caused uniform distortion to the crystal structure of the phosphor and resulted in reducing the lengths of a and c axes and Β angle of the SrAl₂O₄ crystal. The uniform distortion was accompanied with crystal defects which can trap the holes generated by the excitation of Eu²⁺ ions. The afterglow characteristic of the SrAl₂O₄: (Eu²⁺, Dy³⁺) phosphor was thus enhanced.     

Preparation of Co/SiO<Subscript>2</Subscript> Using Several Glycols for Enhanced Fischer-Tropsch Synthesis Activity and Dispersion of Co<Superscript>0</Superscript> Nanoparticles with Unique Co<Superscript>0</Superscript> Particle Size Effect

Abstract  

Co/SiO₂ catalysts with highly dispersed Co⁰ and reducible Co were prepared by impregnation using an aqueous solution of Co nitrate containing ethylene glycol or its homologs. Addition of glycols enhanced FTS activity by a factor of 4. Particle size of Co⁰ decreased from 30 to below 6 nm, while TOF of the catalysts was independent of the Co⁰ particle size.     

Photocatalytic Activity of a TiO<Subscript>2</Subscript> Photocatalyst Doped with C<Superscript>4+</Superscript> and S<Superscript>4+</Superscript> Ions Having a Rutile Phase Under Visible Light

C⁴⁺ and S⁴⁺-codoped titanium dioxide (TiO₂) having a rutile phase was prepared. By doping C⁴⁺ and S⁴⁺ ions into a TiO₂ lattice, the absorption edge of rutile TiO₂ powder was largely shifted from 400 to 700 nm. 2-Methylpyridine and methyleneblue were photocatalytically oxidized at high efficiency on C⁴⁺ and S⁴⁺-doped TiO₂ under visible light at a wavelength longer than 5 nm.     

Roles of doping ions in persistent luminescence of SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>: Eu<Superscript>2+</Superscript>,<Emphasis Type="Italic">RE</Emphasis><Superscript>3+</Superscript> phosphors

The polycrystalline Eu²⁺ and Dy³⁺ codoped strontium aluminates SrAl₂O₄: Eu²⁺,Dy³⁺ were prepared by a solid-state reaction. The UV-excited photoluminescence, persistent luminescence, and thermoluminescence of the SrAl₂O₄: Eu²⁺,Dy³⁺ phosphors with different compositions and ion doping was studied and compared. The results showed that the Eu²⁺ ion doped in SrAl₂O₄: Eu²⁺,Dy³⁺ phosphors is not only the UV-excited luminescent center but also the persistent luminescent center. The Dy³⁺ ion introduced into SrAl₂O₄: Eu²⁺ crystal matrix can hardly yield any luminescence under UV excitation but acts as an electron trap with a suitable depth for persistent luminescence. The Dy³⁺ codoping would effectively enhance the persistent luminescence and thermoluminescence. Different codoping RE ³⁺ ions have a different effect on persistent luminescence. Only the RE ³⁺ ions (for example, Dy³⁺ and Nd³⁺), which have suitable optical electronegativity, can form suitable electron traps and effectively improve the persistent luminescence of SrAl₂O₄: Eu²⁺. Based on the above observations, a persistent luminescence mechanism, electron transfer model, was proposed and illustrated. The text was submitted by the authors in English.     

Crystallization and luminescence properties of Eu<Superscript>2+</Superscript> doped diopside glass ceramics

Eu²⁺ doped glass ceramics have been prepared and characterized. The crystallization and optical properties of the glass ceramics were studied by XRD, SEM, and fluorescence spectra. The precipitated crystalline phase in the glass ceramics was prismatic diopside (CaMgSi₂O₆) and plate-like cristobalite (β-SiO₂). As the heat treatment time increases, the content of crystals increases gradually. Fluorescence measurements showed that Eu²⁺ ions entered into the diopside crystalline phase and induced a much stronger emission in the glass ceramics than that in the corresponding glass. With increase of Eu²⁺ content, concentration quenching was observed.     

Preparation and characterization of layered silicate magadiite intercalated by Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> for antibacterial behavior

The purpose of this work is the synthesis of two series of layered silicate materials with different ratios (10, 30, 50, 80 and 100) of Cu(NO₃)₂, or Zn(NO₃)₂ by ion-exchange method. Several analysis techniques have been used such as X-ray diffraction, energy dispersive X-ray spectroscopy, thermogravimetric analysis, scanning electron microscope and Fourier transform infrared spectroscopy. The results revealed that ion-exchange method of copper and zinc with different ratios did not affect the structure of Na-magadiite. The gap between the theoretical and experimental ion-exchange are in agreement. Antibacterial activity test against Escherichia coli, Rhizobium sp. and Staphylococcus demonstrate that when ratio was (30, 50, 80 and 100) the antibacterial activity of the layered silicate materials showed high antibacterial activity.     

Ni<Superscript>2+</Superscript> reduction under solar irradiation over CuFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/TiO<Subscript>2</Subscript> catalysts

The photo-electrochemical characterization of the hetero-system CoFe₂O₄/TiO₂ was undertaken for the Ni²⁺ reduction under solar light. The spinel CoFe₂O₄ was prepared by nitrate route at 940 °C and the optical gap (1.66 eV) was well matched to the sun spectrum. The flat band potential (-0.21 V_SCE) is more cathodic than the potential of Ni²⁺/Ni couple (-0.6 V_SCE), thus leading to a feasible nickel photoreduction. TiO₂ with a gap of 3.2 eV is used to mediate the electrons transfer. The reaction is achieved in batch configuration and is optimized with respect to Ni²⁺ concentration (30 ppm); a reduction percentage of 72% is obtained under sunlight, the Ni²⁺ reduction is strongly enhanced and follows a first order kinetic with a rate constant of 4.6×10^-2 min^-1 according to the Langmuir-Hinshelwood model.     

Optimization of Opto-Electrical and Photocatalytic Properties of SnO<Subscript>2</Subscript> Thin Films Using Zn<Superscript>2+</Superscript> and W<Superscript>6+</Superscript> Dopant Ions

Abstract  

A series of Zn²⁺ and W⁶⁺ doped tin oxide (SnO₂) thin films with various dopant concentrations were prepared by spray pyrolysis deposition, and were characterized by X-ray diffraction, atomic force microscopy, contact angle, absorbance, current density–voltage (J–V) and photocurrent measurements. The results showed that W⁶⁺ doping can prevent the growth of nanosized SnO₂ crystallites. When Zn²⁺ ions were used, the crystallite sizes were proved to be similar with the undoped sample due to the similar ionic radius between Zn²⁺ and Sn⁴⁺. Regardless of the dopant ions’ type or concentration, the surface energy has a predominant dispersive component. By using Zn²⁺ dopant ions it is possible to decrease the band gap value (3.35 eV) and to increase the electrical conductivity. Photocatalytic experiments with methylene blue demonstrated that with zinc doped SnO₂ films photodegradation efficiencies close to 30% can be reached.     

Spectroscopic investigations of Eu<Superscript>3+</Superscript> and Tb<Superscript>3+</Superscript>: Cadmium lead boro tellurite glasses

This paper reports on the preparation and spectral properties of europium (Eu³⁺) and terbium (Tb³⁺) ions doped cadmium lead boro tellurite (CLBT) glasses. For reference glasses, physical properties have been evaluated. From the [measurements of X-ray diffraction (XRD), glass amorphous nature of these [glasses has been studied. From the emission spectra of Eu³⁺: CLBT glasses, five [transitions (⁵ D ₀ → ⁷ F ₀, ⁷ F ₁, ⁷ F ₂, ⁷ F ₃ and ⁷ F ₄) at 579, 591, 613, 652 and 701 nm are observed with λ_exci = 392 nm (⁷ F ₀ → ⁵ L ₆) and in the case of Tb³⁺: CLBT glasses, four emission transitions ⁵ D ₄ → (⁷ F ₆, ⁷ F ₅, ⁷ F ₄ and ⁷ F ₃) are observed at 489, 543, 584 and 621nm respectively monitered with λ_exci = 376 nm (⁷ F ₆ → ⁵ G ₆).     

A study of the surface and luminescence properties of ZnS : Mn<Superscript>2+</Superscript> nanosized phosphors

The influence of the stabilizer and thermal treatment on the luminescence and surface properties of ZnS: Mn²⁺ nanosized phosphors has been studied. It has been found that ammonium polyacrylate is the optimal stabilizer for the use in the preparation of phosphors with nanoparticles that exhibits the highest brightness without applying thermal treatment. Analysis of the correlation between the luminescence spectral bands and the content of active surface adsorption sites has demonstrated that the model of active sites previously developed for the surface of zinc sulfide phosphors with large particles can also be used for nanosized phosphors.     

Theoretical studies of local structures and spin hamiltonian parameters for Cu<Superscript>2+</Superscript> in alkali barium borate glasses

The local structures and spin Hamiltonian parameters are theoretically studied for Cu²⁺ in alkali barium borate glasses 20A₂O ? 24.5BaO · 55B₂O₃ · 0.5CuO, where A = Li, Na and K by the quantitative calculations of these parameters for tetragonally elongated octahedral 3d ⁹ clusters. The [CuO₆]^10? clusters are subject to the local relative tetragonal elongation ratios 7.8, 8.1 and 8.4% in Li, Na and K barium borate glasses, respectively, owing to the Jahn–Teller effect. The increasing (Li < Na < K) local relative elongation ratio and decreasing cubic field parameter and covalency factor are discussed in a consistent way.     

Structural and Activity Investigation into Al<Superscript>3+</Superscript>, La<Superscript>3+</Superscript> and Ce<Superscript>3+</Superscript> Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

Abstract  

Twelve phosphomolybdate compounds were synthesized via cationic exchange and were of the form: M _x H_3–3x [PMo₁₂O₄₀] (M = Al, La or Ce; 0 ≤ x ≤ 1). These compounds were analyzed by XRD and adsorption isotherm. Aluminum addition causes a primitive cubic phase, while lanthanum and cerium yield body-centered structures. La and Ce addition reduces surface area of phosphomolybdate structure. Temperature-programmed experiments for the selective oxidation of isobutane yielded methacrolein, 3-methyl-2-oxetanone (lactone), acetic acid (not with aluminous compounds), propene (only with aluminous compounds), carbon dioxide and water. The preference for propene rather than acetic acid formation with Al³⁺ may be due to the smaller cation size, or primitive cubic structure. These products form via two distinct reaction processes, labeled categories 1 and 2. Category 1 formation is associated with isobutane forming products on the surface, but reaction rate determined by bulk migration of charged particles. Category 2 formation is concerned with isobutane penetrating deep within the bulk of the substrate and forming products which subsequently desorb in a series of bell-shaped humps. Methacrolein forms via both category 1 and 2, whilst all other products form via category 2 exclusively. Kinetic analysis showed apparent activation barriers for category 1 methacrolein formation range from 67 ± 2 kJ mol⁻¹ to >350 kJ mol⁻¹, and occur in groups with small, medium and large activation barriers. The addition of +3 metal cations to the phosphomolybdate anion increase thermal stability, significantly decreasing deactivation; IR spectroscopy shows that the Keggin structure remains intact during temperature-programmed experiments with the Al, La and Ce salts.     

Dehydration of aldoximes on rare earth exchanged (La<Superscript>3+</Superscript>, Ce<Superscript>3+</Superscript>, RE<Superscript>3+</Superscript>, Sm<Superscript>3+</Superscript>) Na–Y zeolites: A facile route for the synthesis of nitriles

Rare earth exchanged Na–Y zeolites, H-mordenite, K-10 montmorillonite clay and amorphous silica-alumina were effectively employed for the continuous synthesis of nitriles. Dehydration of benzaldoxime and 4-methoxybenzaldoxime were carried out on these catalysts at 473 K. Benzonitrile (dehydration product) was obtained in near quantitative yield with benzaldoxime whereas; 4-methoxybenzaldoxime produces both Beckmann rearrangement (4-methoxyphenylformamide) as well as dehydration products (4-methoxy benzonitrile) in quantitative yields. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream (TOS) studies show decline in the activity of the catalysts due to neutralization of acid sites by the basic reactant and product molecules and water formed during the dehydration of aldoximes.     

Thermal Stability and Spectral Properties of Tm<Superscript>3+</Superscript>-Yb<Superscript>3+</Superscript> CO-Doped Tellurite Glasses

Glasses of the system 75TeO₂–20ZnO–5La₂O₃–0.8Tm₂O₃–xYb₂O₃ were prepared by high temperature melt cooling method. Results of differential scanning calorimetry indicate that, all glass samples have excellent thermal stability. Judd–Ofelt strength parameters, spontaneous emission probabilities, fluorescence branching rations, fluorescence radiative lifetime of Tm³⁺ ions in tellurite glass were calculated. The impact of Yb³⁺ concentration on the fluorescence properties of Tm³⁺ ions in the S band under the pumping wavelength of 465 nm was investigated in a suggestion that, ³H₄ radiative lifetimes will be prolonged and the performance of optical amplifier gain of Tm³⁺ in tellurite glass co-doped with 0.5 mol % Yb³⁺ ions will be improved.     

Gd<Superscript>3+</Superscript> doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with proper magnetic and supercapacitive characteristics: A novel synthesis platform and characterization

A novel electrochemical procedure was developed for the facile preparation of Gd-doped iron oxide nanoparticles (GdIO-NPs). A simple galvanostatic deposition (i=10 mA cm^-2) was done in an additive-free aqueous solution containing FeCl₂·4H₂O, Fe(NO₃)₃·9H₂O and GdCl₃·6H₂O. The XRD, FE-SEM, EDS and TEM characterizations showed that the product is composed of 15% GdIO-NPs with 10 nm in size. VSM analysis proved that the GdIO-NPs are superparamagnetic. The cyclic voltammetry and charge-discharge tests showed that the prepared GdIO-NPs are capable to deliver specific capacity as high as 190.1 F g^-1 at 0.5A g^-1 and capacity retention of 95.1% after 2000 cycling. Based on the results, it was concluded that the developed electrochemical strategy acts as an efficient procedure for the preparation of lanthanide doped MNPs with proper magnetic and supercapacitive characters.