Effect of precipitants during the preparation of Cu-ZnO-Al2O3/Zr-ferrierite catalyst on the DME synthesis from syngas

The synthesis of dimethyl ether (DME) from biomass-derived model synthesis gas has been investigated on Cu-ZnO-Al₂O₃/Zr-ferrierite bifunctional catalysts. The catalysts are prepared by co-precipitation–impregnation method using Na₂CO₃, K₂CO₃ and (NH₄)₂CO₃ as the precipitants. The catalytic activity tests reveal that the best yield of DME can be obtained on the catalyst precipitated by using (NH₄)₂CO₃. Detailed characterization studies conducted on the catalysts to measure their properties such as surface area, acidity by temperature-programmed desorption of ammonia (NH₃-TPD), reducibility of Cu oxide by temperature-programmed reduction (TPR), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and copper surface area and particle size measurements by N₂O titration method. Increasing the number of moderate acidic sites and facilitation of easily reducible copper species with small particle size are found to be the prime reasons for the superior functionality of the (NH₄)₂CO₃ precipitated catalyst. The usage of (NH₄)₂CO₃ also leaves no residual ions, whereas the presence of residual K⁺ and Na⁺ ions in the case of K₂CO₃ and Na₂CO₃ precipitated catalysts leads to lower activity and selectivity.     

Nonlinear optical properties of poly‐ortho‐toluidine films implantated by N+ ions with different energy

This article reports experimental work on the effect of N⁺ ion implantation on third‐order nonlinear optical properties of POT films. Using K₂Cr₂O₇ as oxidizing agent, poly‐ortho‐toluidine (POT) was synthesized in 1 M hydrochloric. The POT films were prepared by spin‐coating method and then implantated by N⁺ ions (15–30 KeV) at a dose 1.9 × 10¹⁶ ions/cm². The films were characterized by FT‐IR spectroscopy, visible spectroscopy and SEM, their third‐order nonlinear optical susceptibility (χ⁽³⁾) were also examined by a degenerate four‐wave mixing (DFWM) system at 532nm. Compared to pristine POT films, the optical band gap obtained from visible spectra decreased from 3.58 to 3.48 eV when the energy was 30 KeV. Also, The χ⁽³⁾ value of implantated POT films increased from 3.31 × 10⁻¹⁰ esu to 4.04 × 10⁻⁹ esu when the implantated energy was 25 KeV. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

IR spectroscopic investigation of interaction between sodium aluminosilicate electrode glasses and aqueous solutions

The effect of introduction of aluminum oxide into the composition of sodium silicate glasses has been studied by IR absorption and reflection spectroscopy. The change in the spectroscopic characteristics of glasses after their treatment with HNO₃ and AgNO₃ aqueous solutions is analyzed. The concentration profiles of Na₊ and Ag₊ ions in the surface layers of these glasses are determined by the HF-sectioning technique. It is found that silver ions predominantly interact with the [AlO_4/2]^- groups in the glass. The leaching of sodium ions, formation of amorphous silica in the surface layers of the treated glass samples, and exchange of sodium ions by hydrogen ions are revealed from changes in the spectra.     

IR spectroscopic investigation of interaction between sodium aluminosilicate electrode glasses and aqueous solutions

The effect of introduction of aluminum oxide into the composition of sodium silicate glasses has been studied by IR absorption and reflection spectroscopy. The change in the spectroscopic characteristics of glasses after their treatment with HNO₃ and AgNO₃ aqueous solutions is analyzed. The concentration profiles of Na₊ and Ag₊ ions in the surface layers of these glasses are determined by the HF-sectioning technique. It is found that silver ions predominantly interact with the [AlO_4/2]^- groups in the glass. The leaching of sodium ions, formation of amorphous silica in the surface layers of the treated glass samples, and exchange of sodium ions by hydrogen ions are revealed from changes in the spectra.     

Poly(styrene-b-isobutylene-b-styrene) block copolymer ionomers (BCPI) and BCPI/silicate nanocomposites. 2. NaBCPI sol-gel polymerization templates

Polystyrene (PS) blocks in poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers were partially sulfonated and the acid groups converted to Na⁺SO₃⁻ groups to create ionomers. Then, dimethylacetamide was used to selectively swell the ionic PS domains and the swollen films were exposed to sol-gel reactive tetraethylorthosilicate solutions. (EtO)_4−xSi(OH)_x monomers then permeated films so that sol-gel reactions occurred within/around the ionic PS domains. Environmental scanning electron microscopy/energy dispersive X-ray spectroscopy investigations showed that silicate structures can be incorporated within the interior of the ionomer films. Differential scanning calorimetry studies indicated that there is no variance in the PIB block T_g with respect to ionomer formation, or with respect to silicate loading of the ionomer at low levels, which suggests that the silicate component does not reside in the PIB phase. ²³Na solid state NMR spectroscopy detected isolated Na⁺SO₃⁻ groups as well as aggregated SO₃⁻Na⁺ ion pairs for ‘as cast’ and ‘dry’ non-silicate containing ionomer samples. In a hydrated sample, almost all Na⁺ ions were solvent-separated. AFM analysis showed that phase separation exists, but that the degree of order is significantly less than that for hybrids based on the corresponding benzyltrimethylammonium ionomer. This frustrated morphology was also seen in the results of small angle X-ray scattering experiments. Given the scale of organic/inorganic heterogeneity, these hybrids are properly classified as nanocomposites.     

Interaction of nafion ionomers toward various solvents

Interactions of Nafion (Naf) ionomer with water, aqueous ethanol (EA), aqueous isopropyl alcohol (IPA), and aqueous ammonia were investigated by attenuated total reflectance (ATR)–infrared (IR) spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and computational modeling studies. Microstructural features by ATR–IR revealed the existence of hydrophilic interaction of Naf with all solvents. The Naf membranes formed hydrogen bonds with water, aqueous EA, and IPA. The incorporation of solvents on the Naf matrix impaired the crystallinity, which was highest in the case of IPA. Of all the microsolvated structures of Naf investigated, the formation of H₃O⁺ ions was evident; in addition, H₅O₂⁺ ions appeared in the alcohol–water mixture, and NH₄⁺ ions were observed in the water–ammonia mixture along with a direct ion pair with the SO₃^? group in Naf. Theoretical studies based on computational modeling disclosed that the interchain distance increased with enhanced interactions (hydrophobic interactions in particular), and this was in good agreement with the highest swelling ratio of the Naf membrane in aqueous IPA and EA solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An in Vitro–Selected DNAzyme Mutant Highly Specific for Na+ under Slightly Acidic Conditions

Sodium is one of the most common metal ions in biology; however, DNA-based sodium probes have only been reported recently. A Na⁺-specific RNA-cleaving DNAzyme named NaA43 is active with Na⁺ alone. In this work, we were using Co(NH₃)₆³⁺ as the intended metal cofactor for in vitro selection, but obtained a mutant of the NaA43 DNAzyme. The mutant was named NaH1, and differs from NaA43 by only two nucleotides. NaA43 has an optimal pH of 7.0, whereas the optimal pH for NaH1 is 6.0. This difference might be due to our selection having been performed at pH 6.0. NaH1 also displays an excellent selectivity for sodium relative to other competing monovalent ions, as well as a fast catalytic rate of (0.11±0.01) min⁻¹ with 50 mm Na⁺. At low Na⁺ concentrations, the selected DNAzyme exhibited a higher cleavage rate than NaA43 and thus a tighter apparent K_d of (12.0±1.6) mm Na⁺. Furthermore, the NaH1 DNAzyme was engineered into a fluorescent Na⁺ biosensor by attaching a fluorophore/quencher pair to the DNAzyme with a detection limit of 223 μm Na⁺. Preliminary work on detection of Na⁺ in serum was demonstrated as well. This study provides a useful mutant that works in a slightly acidic environment, which might be useful for sensing Na⁺ in acidic in vivo environments.     

Polystyrolaustauscher mit 5-(4-dimethylaminobenzyliden)-rhodanin als ankergruppe für die abtrennung von silber,gold und quecksilber

The distribution coefficients of Ag⁺, Au³⁺, and Hg²⁺ on a polystyrene exchanger with 5-(4-dimethylaminobenzylidene)-rhodanin as anchor group are determined as function of pH in 0,1 M NaNO₃ as basic solution and after addition of NaCl, NH₄NO₃, Na₂S₂O₃ or NaCN. Ag⁺ ions are bound with relatively high distribution coefficients if the concentrations of NaCl, NH₄NO₃ and NaCN are low. Na₂S₂O₃ interferes even in low concentrations. Au³⁺ and Hg²⁺ ions are bound with relatively high distribution coefficients in the presence of 0.5 M NaCl.     

Redox chemistry of highly dispersed rhodium in zeolite NaY

NaY zeolite exchanged with [Rh(NH₃)₅Cl]²⁺ ions have been studied using temperature programmed oxidation (TPO), temperature programmed reduction (TPR), and Fourier transformed infrared spectroscopy. The TPO profiles show that ammine ligands in NaY encaged [Rh(NH₃)₅Cl]²⁺ are destroyed above 300 °C, whereas the Rh precursor ion remains intact after calcination at 200 °C. TPR profiles in conjunction with the CO_ads IR spectra show that the reducibility of Rh by H₂ is largely controlled by the concentration of the surface protons, i.e. Rh³⁺+H₂Rh⁺+2H⁺ Rh⁺ + 1/2H₂Rh⁰+H⁺ In the presence of ammonia, the protons are neutralized and Rh³⁺ is reduced to Rh⁰. However, reduction remains incomplete when the concentration of protons is high. The ammonia was provided either by NH₃ admission or by conservation of ammine ligands by controlled calcination. CO adsorption does not lead to reoxidation of Rh⁰ particles to Rh⁺ ions.     

Infrared spectroscopy of NH4-bearing and saturated clay minerals: A review of the study of layer charge

Infrared (IR) spectroscopy study of the layer charge of clay minerals demonstrates that the υ₄ NH₄⁺ band, assigned to the deformation vibrations of the NH₄⁺ ion can be used to evaluate the charge characteristics of NH₄⁺-bearing clay minerals. Total accessible charge, equivalent to cation exchange capacity (CEC), as well as tetrahedral and octahedral charge distribution in both dioctahedral and trioctahedral smectites are determined by quantifying the υ₄ NH₄⁺ band before and after lithium treatment. When using the KBr pressed pellets technique, the position and the shape of the υ₄ NH₄⁺ bands can distinguish exchangeable and fixed NH₄⁺ in clay minerals.     

Amperometric determination of ammonium ions with a microbial sensor

A sensor for NH⁺₄ ions has been developed, which consists of immobilized micro-organisms (Bacillus subtilis, Pseudomonas aeruginosa, Trichosporon cutaneum) in combination with an electrochemical transducer. This sensor is based on the measurement of acceleration of respiration after addition of NH⁺₄ in the presence of glucose. The physiological background of this signal and its connection with NH⁺₄ ion uptake and/or metabolism is discussed. The response time of the sensor is about 5.10 s for NH⁺₄ ions. A linearity was observed between 0.005 and 0.15 mmol dm^?3 NH⁺₄ ions. The sensitivity of the sensor remained almost constant for 12 days. The sensor was used to determine NH⁺₄ ions in a microbial fermentation broth.     

Regulation of dye assembly within wet and dry nafion films

Different forms of Nafion films were prepared and used to exchange phenothiazine and phenazine dye cations. The monomer dye molecules are emittive and the protonated and aggregated dye molecules are nonemittive. A spectrophotometer and spectrofluorometer were used effectively to identify these molecules in the adsorbed state and the control of different forms of dye molecules by Nafion film was clearly established. Protonation of the dye molecules occurred mainly in the proton-exchanged dry Nafion film (H⁺—Nf), whereas dimerization of dye molecules was predominant in the sodium-exchanged dry Nafion film (Na⁺–Nf). The higher acidity and narrow ionic cluster and interfacial regions of the dry Nafion films were found to control the protonation and dimerization of dye molecules. The dyes were predominantly in monomeric form in the wet H⁺– and Na⁺–Nf films. When the Na⁺–Nf film was in a wet condition, the ionic cluster and interfacial regions expanded to form a more open structure. When large hydrophobic organic cations like tetrabutyl ammonium ions (Bu₄N⁺) and tetraethyl ammonium ions (Et₄N⁺) were exchanged into the Nafion film, the film structure was totally controlled by these organic cations and, consequently, controlled the monomeric and dimeric forms of dyes in the film. The dye adsorbed dry H⁺– and Na⁺–Nf films may find applications in acid–base sensors. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 777–787, 1997     

Alkali metal tungsten bronze-doped energy-saving glasses for near-infrared shielding applications

Tungsten bronze has attracted global attention for its applications in near-infrared (NIR)-shielding windows. Here, alkali metal tungsten bronze (M_xWO₃, M = one or two types of Li, Na, and K)-doped glasses are prepared by a simple melt-quenching method. Their structure and properties were characterized by XRD, Raman spectroscopy, XPS and UV–Vis–NIR spectrophotometry. The effects of M on their structure and the NIR shielding performance are investigated. The LiF sample has the best NIR shielding performance, but its visible transmittance is sacrificed due to its low quality. The glasses containing mixed Li⁺ and K⁺ cooperate to form a high-quality Li⁺/K⁺-codoped tungsten bronze, while the glasses containing mixed Li⁺ and Na⁺ compete for limited tungsten resources to form Li⁺- and Na⁺-doped tungsten bronzes separately. The research here is helpful for understanding the role of different alkali metal ions in bulk energy-saving glass and is hugely significant for the guidance of the future applications of energy-saving glass without films.     

A diamino based resin modified silica composite for the selective recovery of tungsten from wastewater

A new adsorbent was developed by synthesizing 1,8‐diaminonaphthalene formaldehyde resin (DANFR) and coating it over the surface of silica gels. The silica composite was then treated with HCl for the activation of binding sites (?NH₃⁺Cl^?) on its surface. The structure of DANFR and its coating over the silanols were thoroughly characterized. Further, the adsorbent was applied to remove tungsten (W) from printed circuit board recycling unit wastewater that contained various co‐metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Pb²⁺, NH₄⁺, Zn²⁺, Cu²⁺ and Mn²⁺. The selective removal was achieved due to the anion exchange mechanism of Cl^? with W(VI) while other cations get repelled from the surface (?NH₃⁺) of the DANFR‐silica composite. X‐ray photoelectron spectroscopy studies, Raman spectra and overlay chromatograms of ion chromatography demonstrated selective separation of WO₄^2? species from the wastewater. A removal capacity of 55.32 mg g^?1 for W(VI) was achieved from the wastewater within 45 min of reaction (pH ca 6.0). Simultaneous treatment with neat aqueous solution of W brings out 63.27 mg g^?1 of W(VI) removal. Finally, recovery of WO₄^2? ions and regeneration of the adsorbent were carried out by using alkaline solution which demonstrated successful desorption, as investigated by using ion chromatography. © 2016 Society of Chemical Industry     

Scavenging Ratios in an Urban Area in the Spanish Basque Country

For a period of six years (1995–2000) the scavenging ratio, which is the ratio of a pollutant's concentration in water to its concentration in air, collected at an urban site in the Spanish Basque Country was studied. The aerosol is characterized by SO₄ ^2? and NO₃? with 1.79 and 1.61 μg m^?3, respectively. Greater fractions of SO₄ ^2?, NO₃?, and NH₄+ ions were present in the fine particle range, while greater fractions of other ions appeared in the coarse range. The most important species found in the precipitation is SO₄ ^2? with 3.0 mg l^?1. NO₃?, Ca²⁺, and Cl^? are the second most important ions. The volume-weighted mean concentration of H⁺ is 4.6 μg l^?1 (pH = 5.3). The concentration of all analyzed ions (except H⁺) decreases throughout the rain event, showing the washout phenomenon of the rainwater. The scavenging ratio for the anthropogenic ions NO₃?, SO₄ ^2?, NH₄+, and K⁺ is lower than the scavenging ratio for the marine-terrigenous ions, Cl^?, Na⁺, and Ca²⁺.     

NH2+ implantations induced superior hemocompatibility of carbon nanotubes

NH₂⁺ implantation was performed on multiwalled carbon nanotubes (MWCNTs) prepared by chemical vapor deposition. The hemocompatibility of MWCNTs and NH₂⁺-implanted MWCNTs was evaluated based on in vitro hemolysis, platelet adhesion, and kinetic-clotting tests. Compared with MWCNTs, NH₂⁺-implanted MWCNTs displayed more perfect platelets and red blood cells in morphology, lower platelet adhesion rate, lower hemolytic rate, and longer kinetic blood-clotting time. NH₂⁺-implanted MWCNTs with higher fluency of 1 × 10¹⁶ ions/cm² led to the best thromboresistance, hence desired hemocompatibility. Fourier transfer infrared and X-ray photoelectron spectroscopy analyses showed that NH₂⁺ implantation caused the cleavage of some pendants and the formation of some new N-containing functional groups. These results were responsible for the enhanced hemocompatibility of NH₂⁺-implanted MWCNTs.     

How the Influence of Different Salts on Interfacial Properties of Surfactant–Oil–Water Systems at Optimum Formulation Matches the Hofmeister Series Ranking

In this work, we present the effects of salts on sodium dodecyl benzene sulfonate micellization and on the interfacial performance of a sodium dodecyl benzene sulfonate–heptane–brine system at optimum formulation, i.e., hydrophilic–lipophilic deviation (HLD) = 0. In order to do that, interfacial tension and dilational interfacial rheology properties of surfactant–heptane–water systems at optimum formulation are measured using an interfacial spinning drop tensiometer with an oscillating velocity, which can accurately measure interfacial rheology properties at both low and ultralow interfacial tensions. The brines used contain one of the following salts: MgCl₂, CaCl₂, NaCl, NH₄Cl, NaNO₃, CH₃COONa, or Na₂SO₄. We performed a one-dimensional salinity scan with each of these salts to achieve an optimum formulation. In relation to the Hofmeister series, we found that, at optimum formulation, systems with chaotropic ions (NH₄⁺, NO₃⁻) present interfaces with ultralow interfacial tensions, very low dilational modulus, and a low phase angle, whereas kosmotropic ions (Mg²⁺, Ca²⁺, SO₄⁻²) generate high interfacial tension and high rigidity monolayers. Intermediate ions in the Hofmeister series (Na⁺, CH₃COO⁻, Cl⁻) present interfaces with intermediate properties. Furthermore, according to the Hofmeister series, interfaces can be respectively ordered from higher to lower rigidity for surfactant counterions Mg²⁺ > Ca²⁺ > Na⁺ > NH₄⁺ and coions SO₄²⁻ > CH₃COO^– > Cl⁻ > NO₃⁻, which correspond to a salting-out (highest rigidity) and salting-in (lowest rigidity) effect. We observed that counterions have a more significant effect on surfactant–oil–water system properties than those that act as coions.     

Solvent Extraction of Li+ using Organophosphorus Ligands in the Presence of Ammonia

In this work, the selective extraction of Li⁺ with the aid of organophosphorus ligands (H-OP) including phenylphosphonic (H-PHO), phenylphosphinic (H-PHI) and bis(2-ethylhexyl) phosphoric (H-BIS) acids in the absence and presence of ammonia was studied. Adding NH₃ to the aqueous phase resulted in significant improvement in the % extraction of Li⁺ into the organic phase containing H-OP ligands. The highest % extraction values obtained in the case of H-PHO, H-PHI, and H-BIS were 43.2%, 45.7%, and 90.0%, respectively. Two mechanisms were inferred; the first was that the extraction equilibrium reaction of LiCl + H-OP ? Li-OP + HCl shifted forward due the reaction of the produced HCl with NH₃. The second mechanism was that the Li⁺/NH₄⁺ exchange of NH₄-OP (produced from the reaction of H-OP with NH₃) was easier than Li⁺/H⁺ exchange of H-OP itself. Competitive extraction experiments indicated that the selectivity factors of Li⁺ over Na⁺ and K⁺ were strongly dependent on the concentration of H-OP ligands which suggested that aggregation of ligand molecules via hydrogen bonding is the limiting factor for selectivity.     

Preparation and characterization of Ag-magadiite nanocomposites

Well-defined Ag-magadiite nanocomposites were successfully prepared by an ion-exchange method using a silver ammine complex, [Ag(NH₃)₂]NO₃, as the starting material. These nanocomposites were found to have a structure in which Ag-nanoparticles consisting of a single-crystalline particle were well dispersed in the interlayer spaces of two types of magadiite materials: Na-magadiite (H_0.2Na_1.8Si₁₄O₂₉·7.8H₂O) and H-magadiite (H_1.4Na_0.6Si₁₄O₂₉·3.9H₂O). Such Ag-nanoparticles appear to be caused by heating [Ag(NH₃)₂]⁺ ions incorporated into the interlayer spaces of the magadiite materials by ion exchange with Na⁺ ions. Furthermore, in nanocomposites heated at 120 °C in air, Ag-nanoparticles show a relatively uniform particle size of 3–5 nm, whereas a heterogeneous enlargement of Ag-nanoparticles occurs when the temperature exceeds ∼180 °C.     

A Selective Na+ Aptamer Dissected by Sensitized Tb3+ Luminescence

A previous study of two RNA‐cleaving DNAzymes, NaA43 and Ce13d, revealed the possibility of a common Na⁺ aptamer motif. Because Na⁺ binding to DNA is a fundamental biochemical problem, the interaction between Ce13d and Na⁺ was studied in detail by using sensitized Tb³⁺ luminescence spectroscopy. Na⁺ displaces Tb³⁺ from the DNAzyme, and thus quenches the emission from Tb³⁺. The overall requirement for Na⁺ binding includes the hairpin and the highly conserved 16‐nucleotide loop in the enzyme strand, along with a few unpaired nucleotides in the substrate. Mutation studies indicate good correlation between Na⁺ binding and cleavage activity, thus suggesting a critical role of Na⁺ binding for the enzyme activity. Ce13d displayed a K_d of ～20 mm with Na⁺ (other monovalent cations: 40–60 mm ). The K_d values for other metal ions are mainly due to non‐specific competition. With a single nucleotide mutation, the specific Na⁺ binding was lost. Another mutant improved K_d to 8 mm with Na⁺. This study has demonstrated a Na⁺ aptamer with important biological implications and analytical applications. It has also defined the structural requirements for Na⁺ binding and produced an improved mutant.