Presence Of Na Ions Research Articles

Radiation effect on the UV-green thermally stimulated luminescence emission of a natural Na-rich aluminosilicate

This paper reports on the thermoluminescence (TL) emission (from 250 to 500 nm) of a 10 Gy irradiated natural Na-rich aluminosilicate from Minas Gerais (Brazil), previously characterized by Raman spectroscopy and differential thermal analysis techniques. 3D-TL spectrum of the analyzed sample displays a complex glow curves with five different emissions bands peaked at 290, 380, 420, 460 and 500 nm that could be associated with structural and point defects. The UV-blue emission bands have the following characteristics: (i) the 290 nm waveband could be due to defects-sites by the presence of Na ions; (ii) the 380 nm band, caused by intrinsic defects in the lattice (i.e. Non-Bridging Oxygen Hole Centers (NBOHCs), [AlO4]o centres, alkali planar defects and Oxygen Defect Centers (ODCs), among others); (iii) the 420 nm waveband, linked to the recombination on a centre formed from a hole-oxygen atom adjacent to two aluminum atoms (Al-O-Al) and Al-O-Si complexes; (iv) the 460 nm band, associated with the presence of Ti4+ in the plagiclase crystal lattice. The green waveband could be linked to de-excitation of Mn2+ ions. The estimation of the activation energy (Ea) from the 10 Gy-induced TL glow curves analyzed by means of the initial rise method display linear regressions with acceptable r coefficients (r > 0.977) that reveal three groups of components with traps at different depth in the crystal lattice of the albite with Ea values in the range of 0.5–0.64 eV.

Achieving High Capacity at High Rates in Aqueous-Based Zn-Ion Batteries Via Advanced 3D Electrode Design and Mixed-Salt Electrolytes

Manganese oxides (MnOx) are a well- established class of active materials for electrochemical energy- storage technologies ranging from primary alkaline to rechargeable Li- ion batteries and more recently, have shown great promise in electrochemical capacitors. The widespan applicability of MnOx in these different devices stems from the use of different electrode structures and electrolyte compositions. However, we have demonstrated that with the use of an advanced 3D electrode architecture in which the MnOx component exists as a conformal nanoscale coating on a carbon nanofoam paper with a through-connected pore structure, it is possible to deliver full theoretical capacity of LiMn2O4, a nominal battery material, at EC-like rates in an aqueous electrolyte. We are now extending the performance enhancements gained via the 3D electrode architecture demonstrated for Li-ion battery chemistries to aqueous-based Zn-ion batteries comprised of a MnOx@carbon nanofoam cathode and a Zn anode. We show that the MnOx@carbon nanofoam delivers full theoretical capacity (308 mA h g-1) at 1 C when cycled in an aqueous mixed salt electrolyte (e.g., 0.75 M Na2SO4 + 0.25 M ZnSO4) – delivering high capacity at high rate in a single electrode. To gain a better understanding of the charge-storage reactions occurring in this complex system, we perform a suite of characterization methods as a function of potential. Electrochemical impedance spectroscopy confirms that MnOx stores charge via pseudocapacitance, supported by the presence of Na ions in the electrolyte, at potentials not associated with Zn2+ insertion/extraction. Ex-situ surface characterization of discharged MnOx@carbon nanofoam electrodes reveal the formation of Zn4(OH)6SO4·5H2O crystallites on the exterior surface, but no evidence of those precipitates after recharge. The ability to deposit/dissolve the Zn4(OH)6SO4·5H2O precipitates in conjunction with pseudocapacitive charge-storage supports long-term cycling ability, with minimal decrease in capacity over 1000 cycles.

Insights of Diffusion Doping in Formation of Dual-Layered Material and Doped Heterostructure SnS-Sn:Sb2S3 for Sodium Ion Storage.

Insights into the formation mechanism of a dual-layered and doped heterostructure material SnIIS-SnIV:Sb2S3 are reported. In the presence of mixed alkyl thiols, first nanotubes of Sb2S3 were formed, and upon introduction of Sn(IV), SnIIS was deposited onto the surface of these tubular structures. Upon further annealing at a constant temperature, sluggish transformation resulted in a Sn(II)S-Sn(IV) doped Sb2S3 heterostructure, which finally turned to flake-like layered doped Sb2S3 nanostructures. SnS and Sb2S3, both being layered materials, were explored for the study of Na-ion storage, and these heterostructures were observed to be superior in comparison to the individual materials as well as the final doped nanostructures. The mechanism of formation of the heterostructures, the epitaxy at the junction, the diffusion doping, and the dopant-induced axial exfoliations leading to the final doped structures were studied. The electrochemical conversions in the presence of Na ions were also investigated, and insights into the mechanisms of both are reported in this Letter.

Selenium-Substituted Hydroxyapatite Nanoparticles and their in Vitro Interaction on Human Bone Marrow- and Umbilical Cord-Derived Mesenchymal Stem Cells

Hydroxyapatite (HA) is biocompatible with high binding activity to DNA and protein. Selenium (Se) plays a specific role in human health. Incorporation of selenium into biocompatible hydroxyapatite (HA) may endow the material with novel characteristics. in this work, a series of nano-hydroxyapatite [SeHA] powders with 1 to 5 mass-% substituted selenium were synthesised by an aqueous precipitation method using sodium selenite. The precipitates were dried at 60°C and their dried ground powders were characterised by XRD, FTIR end TEM. Substitution of Se ions took place in the crystal lattice of HA. The presence of Na ions in the hydroxyapatite was detected by XRF in all samples with selenium substituted in the lattice. No change was detected in the morphology of the rod-shaped particles, but a reduction in their size was observed as the selenium content increased. The cytotoxicity of the powders on human bone marrow mesynchymal stem cells (BM-MSCs) and umbilical cord-derived mesenchymal stem cells (UC-MSCs) was evaluated in vitro. The amount of 0.59 mM Se, corresponding to 2 mass-% substitution in the HA lsttice, did not show cytotoxicity and stimulated proliferation of UC-MSCs in contrast to pure HA powders which inhibited growth of cells. Toxicity started to appear in samples when substitution exceeded 2 mass-%. The highest concentration (5 mass-%) was severely cytotoxic. The results suggest that selenium substitution might be an attractive cell delivery modification of hydroxyapatite nanoparticles for future use in tissue engineering.

Rate-Dependent Nucleation and Growth of NaO2 in Na-O2 Batteries.

Understanding the oxygen reduction reaction kinetics in the presence of Na ions and the formation mechanism of discharge product(s) is key to enhancing Na-O2 battery performance. Here we show NaO2 as the only discharge product from Na-O2 cells with carbon nanotubes in 1,2-dimethoxyethane from X-ray diffraction and Raman spectroscopy. Sodium peroxide dihydrate was not detected in the discharged electrode with up to 6000 ppm of H2O added to the electrolyte, but it was detected with ambient air exposure. In addition, we show that the sizes and distributions of NaO2 can be highly dependent on the discharge rate, and we discuss the formation mechanisms responsible for this rate dependence. Micron-sized (∼500 nm) and nanometer-scale (∼50 nm) cubes were found on the top and bottom of a carbon nanotube (CNT) carpet electrode and along CNT sidewalls at 10 mA/g, while only micron-scale cubes (∼2 μm) were found on the top and bottom of the CNT carpet at 1000 mA/g, respectively.

Structural characteristic of Na2O[sbnd]P2O5[sbnd]GeO2 glass systems

Phosphate glasses based on xNa2O0.5P2O5(0.5−x)GeO2 (0.0⩽x⩽0.5)mol%, were prepared and their structures were characterized by magic angle spinning (MAS) nuclear magnetic resonance (NMR), Raman and IR spectroscopy techniques. It was found that the phosphate network of these glasses is composed of middle (Q2) and branching (Q3) phosphate tetrahedra, whereas germanium part in the network is composed of three- or four-membered GeO4 tetrahedral rings. It was also found that the germanium tetrahedral are randomly connected to either Q2 or Q3 phosphate units in the network. The glass network, especially the Q2 units can be modified by the presence of Na ions. This modification is primarily associated with the phosphate. It is found that these glasses behave as if they are formed from a solution of GeO2 and sodium–phosphate glass with various GeO4 units and the Q2 and Q3 phosphate units randomly distributed in the network.

Solid phase epitaxy of Na-ion irradiated α-quartz: Cathodoluminescence, kinetics and surface morphology

Even at low fluences doping of quartz by ion implantation results in amorphization. Here we report on the measurement of cathodoluminescence and surface structures during solid phase epitaxy in Na-implanted α-quartz annealed in 18O2 atmosphere. Complete epitaxy was achieved under appropriate conditions of ion fluence, annealing temperature and time. The crystalline structure of the samples was studied by Rutherford backscattering channelling spectroscopy and the 18O–16O exchange between the matrix and 18O2 annealing gas by elastic recoil detection analysis. In the cathodoluminescence spectra taken at room temperature, five bands were identified and assigned to various defect centres. Two of the bands in the violet region at 3.25 and 3.65eV strongly vary in intensity at 843–1173K annealing temperature and appear to be intimately correlated with the presence of Na-ions in the implanted region of the matrix. Finally, atomic force microscopy enabled, for the first time, the observation of the correlation of surface structures and epitaxy.

Adsorption of chlorofluorocarbons in nanoporous solids; a combined powder neutron diffraction and computational study of CFCl3 in NaY zeoliteCCDC reference number 201879.

The crystal structure of NaY (Na54Si138Al54O384) + CFCl3 has been determined at 20 K by Rietveld analysis of powder neutron diffraction data in space group Fdm. The sodium cations were located preferentially in sites II, which are fully-occupied and also in sites I, which are half-occupied. A new cation position in the β-cages was detected around x = 0.125, y = 0.125, z = 0.031. Important cation migration is observed upon adsorption of CFCl3, as shown by the absence of cations in sites I′, known to be a favorable cation site in bare NaY, together with the detection of this new site in the β-cages. Part of extraframework cations remained undetected, that were assumed to be located in the supercages in low symmetry sites. The CFCl3 molecules are found in the 12-ring windows, where they accomodate Cl⋯Ozeolite and F⋯Ozeolite van der Waals interactions together with Cl⋯Na(II) electrostatic interactions. (N,V,T) Monte Carlo simulations were performed in order to elucidate the role of extraframework cations in the adsorption of CFCl3 in NaY. They show that the presence of Na ions in the 12-ring window (sites III′) has to be taken into account in order to get adsorption geometries consistent with that obtained from neutron diffraction.

Anomalous Effect of Presence of Na Ions on the Removal of 90Sr from Solutions by Using Various Zeolites

Anomalous Effect of Presence of Na Ions on the Removal of 90Sr from Solutions by Using Various Zeolites

Thermal stability of [B]ZSM-5 molecular sieve

The thermal stability of [BJZSM-5 (boronsilicalite) has been examined by IR, XRD,11B MAS NMR and XPS techniques. [B]ZSM-5 and amorphous borosilicate were converted to α-cristobalite at high temperatures (=750C). However, Na-free amorphous borosilicate was not converted to a-cristobalite at 750C. Therefore, the presence of Na ions in [BJZSM-5 would determine whether this transition occurred or not. When the phase transition to α-cristobalite occurred, most of B atoms tetrahedrally coordinated were released from the ZSM-5 structure and migrated to the exterior surface as a boron compound having trigonal BO3 units and oxidation states of 3.

Ion‐selective micro‐electrode studies of the electrochemical potentials in trout urinary bladder.

Intracellular micro-electrode techniques were used to measure the electrical resistances of the cell membranes and the shunt pathway and intracellular ionic activities in trout urinary bladder when the tissue was incubated in Ringer solution and in the presence of the polyene antibiotic ionophore amphotericin B. In control conditions the transepithelial potential was zero and the intracellular potential was -56 mV. The intracellular ionic activities measured with single- and double-barrel ion-sensitive micro-electrodes for the first time in a fish bladder (aiNa = 16 mM, aiK = 87 mM, and aiCl = 21 mM) indicate an active accumulation of K and Cl ions and an active extrusion of Na ions by the cell. The maintenance of intracellular Cl activity above its equilibrium value depended on the presence of Na ions in the mucosal medium, but was independent of the presence of K ions. Flat cable analysis yielded values for transepithelial, apical, basolateral and shunt resistances of 197, 2790, 1986 and 205 omega cm-2 respectively. Equivalent circuit analysis using amphotericin B yielded similar values for shunt resistance. The paracellular pathway accounts for 96% of transepithelial current flow and this epithelium may be classified as 'leaky'. The cells are electrically coupled with a space constant of 354 micron. Amphotericin B when added to the mucosal solution induced an immediate serosa positive transepithelial potential of about 9 mV and a short-circuit current of 64 microA cm-2. The Vt was ouabain sensitive and dependent on mucosal Na concentration. The origin of the antibiotic induced transepithelial potential was an increase in the sum of the cell membrane electromotive forces. The apical membrane potential depolarized to -7 mV and its resistance fell to 433 omega cm-2. During the first 10 min of exposure aiNa increased to 80 mM and aiK decreased to 7 mM with only a small change in aiCl. The changes in cellular Na+ and K+ activities were in accordance with their passive redistribution down their electrochemical gradients.

Effects of vascular perfusion on the accumulation, distribution and transfer of 3‐O‐methyl‐D‐glucose within and across the small intestine

1. Factors affecting the transfer of the non-metabolized, ;actively transported' sugar, 3-O-methyl-D-glucose (3MG) across the small intestinal epithelium have been examined in vascularly perfused anuran intestine. Transfer has been studied during absorption in the steady state, and also during the period of transition from one steady state to another.2. During the steady state, the rate of absorption of 3MG from the intestinal lumen is equal to the rate of appearance in the portal venous effluent; this rate of transfer is to a small, but significant, extent directly related to the rate of arterial perfusion. With phlorizin in the intestinal lumen, transfer across the epithelium is reduced to very low rates which are independent of the rate of vascular perfusion.3. The apparent size of the tissue pool(s) of 3MG that have to be loaded to achieve the steady state rate of transfer are less than those that unload into the vascular bed after 3MG is removed from the intestinal lumen. This ;up-down asymmetry' is abolished when phlorizin is present in the intestinal lumen during the unloading phase.4. When 3MG is abruptly removed from the intestinal lumen after the tissue has been previously loaded with the sugar, the rate of washout into the vascular bed can be described by the sum of two exponential terms. The two terms differ in that the rate constant of the earlier ;fast' term is sensitive to the rate of vascular perfusion, while the later, ;slow', rate constant is insensitive to flow rate. The total quantity of 3MG that can be unloaded from the tissue into the portal venous effluent is decreased when phlorizin is present in the intestinal lumen during the unloading phase.5. Absorption from the lumen of the anuran intestine continues while the mesenteric circulation is interrupted. An estimate of the concentration of 3MG during the period of vascular stoppage can be made from the quantity recovered in the portal venous effluent when vascular perfusion is reinstituted (;vascular stop-flow'). The extent of the accumulation depends upon the duration of the vascular stoppage and the presence of Na ions in the intestinal lumen is essential for accumulation to occur.6. The findings are discussed in relation to the transfer of 3MG between various possible compartments in the tissue during absorption. Evidence is presented that a re-uptake of previously absorbed 3MG may occur across the brush border membrane. Such a recycling of 3MG across the epithelium implies that the apparent unidirectional fluxes measured across the epithelium between the bulk phase of the lumen and the blood may underestimate the size of fluxes across the epithelium at the cellular level.

The relationship between the electrical and mechanical activity of the guinea-pig stomach.

1. The relationship between electrical and mechanical properties of the antrum circular muscle of the guinea-pig stomach in various ionic environments was investigated by the double sucrose gap method.2. The minimum latency was 82 msec for the onset of the contraction after the spike showed the maximum velocity of the upstroke at 38°C.3. The slow wave, the depolarization of the membrane by excess K ion, and the electrotonic potential also produced contraction.4. On replacement of Na ion by other substances (Li ion, tris ion and sucrose), the amplitude of the spike was similar to that elicited in the presence of Na ion. The amplitude of contraction was not reduced by tris ion, but it was reduced by sucrose and Li ion.5. NO3 and Br ion lowered the electrical and mechanical threshold, and repetitive or enlarged spikes were evoked. The membrane resistance was reduced and the membrane was hyperpolarized. The contraction was enlarged in amplitude and prolonged in duration. Br ion showed more dominant effects on the electrical and mechanical activity than NO3 ion.6. In the absence of Ca ion, Sr and Ba ion produced a spike with amplitude similar to that in the presence of Ca ion. However, the contraction was reduced in amplitude to a tenth of that in Krebs. When Cl ion was replaced with either NO3 or Br ion, the amplitude of contraction was restored to more than half of the control.7. The results are discussed in comparison with the properties of skeletal muscle, and it is proposed that the Ca ion which flows into the cells as the current carrier may release at least a portion of the Ca ion bound in the membrane and activate the contractile protein. Mobilization of bound Ca ion might be influenced by Na and Cl ion.