Rapid synthesis of MgCo2O4 and Mg2/3Ni4/3O2 nanocrystals in supercritical fluid for Mg-ion batteries

Magnesium metal complex oxides are potential electrode materials for magnesium ion batteries with high specific capacities. However, the strong electrostatic interaction between Mg²⁺ and the host lattice due to its divalency induces slow intercalation kinetics of Mg ions within the crystal lattices. Thus, nanocrystalline particles with shortened Mg ion diffusion distance enable the insertion/extraction of Mg ions and improve the specific capacities of the batteries. Herein, we report the facile rapid production of crystalline MgCo₂O₄ and Mg_2/3Ni_4/3O₂ nanocrystals by rapid supercritical fluid processing. The phase transition from spinel to rocksalt during the Mg²⁺ ion intercalation has been confirmed by high-resolution transmission electron microscopy. The nanosheets of Mg_2/3Ni_4/3O₂ rocksalt nanocrystals were controllably synthesized for the first time, which are active materials for magnesium-ion batteries.

High-quality spinel MgCo₂O₄ and rocksalt Mg_2/3Ni_4/3O₂ nanocrystal cathodes allow fast extraction/insertion of magnesium ions for high energy-density batteries.     

Room temperature ferromagnetism in D–D neutron irradiated rutile TiO2 single crystals

Room temperature ferromagnetism (RTFM) was observed in unirradiated rutile TiO₂ single crystals prepared by the floating zone method due to oxygen vacancy (V_O) defects. D–D neutrons mainly collide elastically with TiO₂, producing V_O, titanium vacancies (V_Ti) and other point defects; the density and kind of defect is related to the neutron irradiation fluence. D–D neutron irradiation is used to regulate the concentration and type of defect, avoiding impurity elements. As the irradiation fluence increases, the saturation magnetization (M_s) first increases, then decreases and then increases. To verify the origin of RTFM, the CASTEP module was used to calculate the magnetic and structural properties of point defects in TiO₂. V_O induces a 2.39 μ_B magnetic moment, Ti³⁺ and F⁺ induce 1.28 μ_B and 1.70 μ_B magnetic moments, respectively, while V_Ti induces a magnetic moment of ∼4 μ_B. Combining experimental and theoretical results, increases in V_O concentration lead to M_s increases; more V_O combine with electrons to form F⁺, inducing a smaller magnetic moment. V_O and V_Ti play a key role and M_s changes accordingly with larger fluence. V_O, F⁺ and V_Ti are the most likely origins of RTFM.

D–D neutron irradiation is used to regulate the concentration and type of defect in rutile TiO₂. Room temperature ferromagnetism was observed after irraidiation. Combining experimental and theoretical results, we elucidate the likely origins of RTFM.     

Microstructure and hydrogen storage kinetics of Mg89RE11 (RE = Pr,Nd, Sm) binary alloys

The present work reports the fabrication of Mg₈₉RE₁₁ (RE = Pr, Sm, Nd) alloys by a vacuum induction furnace. The phase analysis, structure characterization and microstructure observation of Mg₈₉RE₁₁ alloys were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). There exhibits a multiphase microstructure in the as-cast Mg₈₉RE₁₁ (RE = Pr, Nd, Sm) alloys from the comprehensive analysis made from XRD and SEM, which are containing the major phase (RE₅Mg₄₁) and several secondary phases (REMg₃ and REMg₁₂). The detections of XRD and TEM reveal that these experimental alloys turn into a MgH₂ nanocrystalline composite with equably distributed RE hydride nanoparticles after hydriding and this MgH₂ major phase turns into a Mg nanocrystalline after dehydriding. The determination results of the hydrogen storage kinetics show that adding the rare earth element (Pr, Sm and Nd) ameliorates the hydriding and dehydriding kinetics of the Mg-based alloys dramatically. The hydrogen desorption activation energy E_a(de) of Mg₈₉Pr₁₁, Mg₈₉Nd₁₁, Mg₈₉Sm₁₁ are 140.595, 139.191, 135.280 kJ mol⁻¹ H₂, respectively. Specially, the hydrogen storage capacity (wt%) of Mg₈₉Sm₁₁ alloy that added Sm element can reached 5 wt%. The improvement of the hydrogen storage performance of Mg₈₉RE₁₁ alloys can be principally ascribed to the RE hydride nanoparticles facilitating the hydriding and dehydriding reactions.

Improving hydrogen storage performance of Mg₈₉RE₁₁ alloys attributes to the RE hydride nanoparticles facilitate the hydriding and dehydriding reactions.     

Influence of an external electric field on the rapid synthesis of MoO3 micro- and nanostructures by Joule heating of Mo wires

The growth mechanism of layered α-MoO₃ nano- and microplates on the surface of Mo wires during Joule heating has been investigated by application of an external electric field to the current carrying wire. The observed rapid growth of the structures, involving enhanced diffusion processes associated to the intense electric current, is further enhanced by the external field leading to a near instantaneous formation of MoO₃ plates. Thermally assisted electromigration in the Mo wire with the additional effect of the electric field appears as a very time effective method to grow MoO₃ layered low dimensional structures. Other molybdenum oxide nanostructures, such as nanospheres and nanocrystallites with different shapes, have been found to grow by deposition from the Mo wire on the electrodes used to apply the external electric field. The growth on the electrodes takes place by a thermally assisted electric-field-driven process.

The growth mechanism of layered α-MoO₃ nano- and microplates on the surface of Mo wires during Joule heating has been investigated by application of an external electric field to the current carrying wire.     

Large improvement in thermoelectric performance of pressure-tuned Mg3Sb2

The Mg₃Sb₂-based Zintl compound is a promising candidate for a high-performance thermoelectric material with the advantage of the component elements being low cost, non-toxic and earth-abundant. Here, we investigate the influence of pressure on the electronic structure and p-type and n-type thermoelectric transport properties of Mg₃Sb₂ by using density functional theory and Boltzmann transport theory. The energy gaps first increase and then decrease with the increasing of pressure, and a peak value of the valley degeneracy of conduction band occurs at 4 GPa. Based on the calculated band structures, the zT (figure of merit) values of p-type Mg₃Sb₂ under pressure are significantly enhanced, which predominantly originates from the boosted PF (power factor) contributed by the increased carrier''s relaxation time. When the carrier concentration reaches 1 × 10²⁰ cm⁻³, the PF of p-type Mg₃Sb₂ at 4 GPa is increased by 35% relative to that of the compound at 0 GPa, thus leading to a considerably improved zT of ∼0.62 at 725 K. Under the same conditions, due to the increased density of states effective mass, the n-type Mg₃Sb₂ exhibits a highest PF of ∼19 μW cm⁻¹ K⁻² and a peak zT of 1.7. Therefore, pressure tuning is an effective method to improve the p-type and n-type thermoelectric transport performance of Mg₃Sb₂-based Zintl compounds. This work on Mg₃Sb₂ under pressure may provide a new mechanism for the experimenters towards the enhancement of the thermoelectric performance of materials.

Because of the modified electronic band structure, the thermoelectric properties of Mg₃Sb₂ can be improved by pressure tuning.     

Structure and mechanical behavior of in situ developed Mg2Si phase in magnesium and aluminum alloys – a review

The demand for lightweight, high specific strength alloys has drastically increased in the last two decades. Magnesium and aluminum alloys are very suitable candidate materials. Research on alloys with an Mg₂Si phase started about three decades ago. The current scenario is that magnesium and aluminum alloys containing an Mg₂Si phase are very popular in the scientific community and extensively used in the automotive and aerospace industries. Mg₂Si is a very stable phase and exhibits excellent mechanical, thermal, electrochemical and tribological properties. This paper presents a brief review of Mg–Si binary alloys, and Mg–Si–Al and Al–Si–Mg alloys. Grain refinement methods and mechanical properties have been reported on lightweight alloys containing Mg and Si. The available results show that silicon reacts with magnesium and forms an intermetallic compound with the stoichiometric formula Mg₂Si. There is in situ formation of an Mg₂Si phase in Mg–Si, Mg–Si–Al and Al–Mg–Si alloys by the diffusion or precipitation process. The morphology and size of an in situ developed Mg₂Si phase depend on the synthesis route and base metal or matrix. In the liquid metallurgy process the precipitation sequence depends on the cooling rate. The morphology of the Mg₂Si phase depends on the precipitation sequence and the mechanical properties depend on the morphology and size of the Mg₂Si phase within the alloy matrix.

The demand for lightweight, high specific strength alloys has drastically increased in the last two decades.     

Searching for double σ- and π-aromaticity in borazine derivatives

Inspired by the double-aromatic (σ and π) C₆H₃⁺, C₆I₆²⁺, and C₆(SePh)₆²⁺ ring-shaped compounds, herein we theoretically study their borazine derivative analogues. The systems studied are the cation and dications with formulas B₃N₃H₃⁺, B₃N₃Br₆²⁺, B₃N₃I₆²⁺, B₃N₃(SeH)₆²⁺, and B₃N₃(TeH)₆²⁺. Our DFT calculations indicate that the ring-shaped planar structures of B₃N₃H₃⁺, B₃N₃I₆²⁺, and B₃N₃(TeH)₆²⁺ are more stable in the singlet state, while those of B₃N₃Br₆²⁺ and B₃N₃(SeH)₆²⁺ prefer the triplet state. Besides, exploration of the potential energy surface shows that the ring-shaped structure is the putative global minimum only for B₃N₃I₆²⁺. According to chemical bonding analysis, B₃N₃H₃⁺, B₃N₃I₆²⁺, and B₃N₃(TeH)₆²⁺ have σ and π delocalized bonds. The number of delocalized σ/π electrons is 2/6 for the first, and 10/6 for the second and third, similar to what their carbon analogs exhibit. Finally, the analysis of the magnetically induced current density allows B₃N₃H₃⁺, B₃N₃I₆²⁺, and B₃N₃(TeH)₆²⁺ to be classified as strongly σ aromatic, and poorly π aromatic compounds.

Evolutionary algorithms, Born–Oppenheimer molecular dynamics and the magnetic criteria of aromaticity have been used to evaluate the stability and σ–π aromaticity of borazine derivatives in order to expand the family of double aromatics systems.     

Cs2NaGaBr6: a new lead-free and direct band gap halide double perovskite

In this work, we have studied new double perovskite materials, A₂¹⁺B²⁺B³⁺X₆¹⁻, where A₂¹⁺ = Cs, B²⁺ = Li, Na, B³⁺ = Al, Ga, In, and X₆¹⁻. We used the all electron full-potential linearized augmented plane wave (FP-LAPW+lo) method within the framework of density functional theory. We used the mBJ approximation and WC-GGA as exchange–correlation functionals. We optimized the lattice constants with WC-GGA. Band structures were calculated with and without spin–orbit coupling (SOC). Further, band structures for Cs₂LiGaBr₆ and Cs₂NaGaBr₆ were calculated with SOC + mBJ to correct the band gap values with respect to experimental value. We obtained direct bandgaps at Γ-point of 1.966 eV for Cs₂LiGaBr₆ and 1.762 eV for Cs₂NaGaBr₆, which are similar to the parent organic–inorganic perovskite (MAPI) CH₃NH₃PbI₃ (E_g = 1.6 eV). Total and partial density of states were analyzed to understand the orbital contribution of Cs, Na, Li, Ga and Br near the Fermi level. The optical properties in terms of real and imaginary ε, refractive index n, extinction coefficient k, optical conduction σ, absorption I, and reflectivity R were calculated. A study of the elastic and mechanical properties shows that both materials are thermodynamically stable. A stable, direct bandgap and a gap value close to those of MAPI make Cs₂NaGaBr₆ a great competitor in the Pb-free hybrid perovskite solar cells world.

In this work, we have studied new double perovskite materials, A₂¹⁺B²⁺B³⁺X₆¹⁻, where A₂¹⁺ = Cs, B²⁺ = Li, Na, B³⁺ = Al, Ga, In, and X₆¹⁻.     

Influence of pressure on the transport,magnetic, and structural properties of superconducting Cr0.0009NbSe2 single crystal

We investigate the superconducting critical current density (J_c), transition temperature (T_c), and flux pinning properties under hydrostatic pressure (P) for Cr_0.0009NbSe₂ single crystal. The application of P enhances T_c in both electrical resistivity (∼0.38 K GPa⁻¹: 0 ≤ P ≤ 2.5 GPa) and magnetization (∼0.98 K GPa⁻¹: 0 ≤ P ≤ 1 GPa) measurements, which leads to a monotonic increase in J_c and flux pinning properties. The field-dependent J_c at various temperatures under P is analyzed within the collecting pinning theory and it shows that δT_c pinning is the crossover to δl pinning above the critical pressure (P_c ∼0.3 GPa). Our systematic analysis of the flux pinning mechanism indicates that both the density of pinning centers and pinning forces greatly increase with the application of P, which leads to an enhancement in the vortex state. Structural studies using synchrotron X-ray diffraction under pressure illustrate a stable hexagonal phase without any significant impurity phase and lattice parameter reduction with P shows highly anisotropic nature.

We investigate the superconducting and vortex dynamics properties on Cr intercalated NbSe₂ single crystal by the application of external pressure.     

Vibrational band-structures caused by internal rotations of the boron Wankel rotor B11−

Nuclear quantum effects are often neglected for systems without hydrogen atoms. However some planar boron rotors turn out to exhibit remarkable nuclear quantum effects. Recent experiment on infrared spectroscopy of B₁₃⁺ shows unexpected spectral broadening which still awaits physical explanation. Here we present quantitative investigations of the vibrational energy levels of B₁₁⁻ up to full dimension. A harmonic-bath averaged Hamiltonian suitable for planar boron rotors is constructed and used to predict typical types of vibrational states of B₁₁⁻. Band structures caused by internal rotations are found for all the investigated vibrational states. The experimental phenomenon of spectral broadening is thus due to the band structures of the corresponding vibrational levels. The detailed information of the relevant vibrational states reported in the present work may provide valuable references for future investigations of high resolution spectroscopy of B₁₁⁻.

The band structures of the vibrational energy levels of B₁₁⁻ lead to corresponding spectral broadening. The vibrational band-structures of planar boron rotors are caused by internal rotations.     

Cold sintering of YBa2Cu3O7−δ

Cold sintering is a sintering technique which enables ceramic powders to be densified at greatly reduced temperatures compared to traditional solid state techniques, which often require temperatures in excess of 1000 °C. These temperatures often preclude the exploitation of size or orientational effects in ceramics as these are lost during heating. One such effect is the orientation of the crystallographic c axis in YBa₂Cu₃O_7−δ (YBCO) which can be controlled through applied pressure. This effect is of interest for increasing critical current density which is highly dependent on the orientation of the a–b (CuO₂) planes within the ceramic. Using cold sintering, we demonstrate that dense YBCO can be created at 180 °C (vs. 1000 °C using solid state) and demonstrate that the likely sintering mechanism is mediated by the cracking which occurs in YBCO when exposed to water. In addition, the ceramics produced show and retain the orientational effect, representing a unique opportunity to study the effect on critical current density. We show that the intergranular critical current when the a–b planes are parallel to the applied field is around 15% higher than when perpendicular.

Cold sintered superconducting YBa₂Cu₃O_7−δ densified at 180 °C shows enhanced critical current densities by exploiting grain alignment created during pressing.     

Luminescence and energy transfer of warm white-emitting phosphor Mg2Y2Al2Si2O12:Dy3+,Eu3+ for white LEDs

A series of Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺ phosphors were synthesized by the solid-state method. The luminescent properties and crystal structures of the Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺ phosphors were analyzed. The XRD results show that the synthesized Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺,Eu³⁺ phosphors are of pure phase. Mg₂Y₂Al₂Si₂O₁₂:Dy³⁺ can emit blue and yellow light under 367 nm light excitation; when doped with Eu³⁺, there is an obvious energy transfer from Dy³⁺ to Eu³⁺, and warm white light can be realized by adjusting the concentrations of Dy³⁺ and Eu³⁺ in Mg₂Y₂Al₂Si₂O₁₂. A warm white LED device was fabricated by combining Mg₂Y_1.88Al₂Si₂O₁₂:0.05Dy³⁺,0.07Eu³⁺ and a UV LED chip (370 nm) under a voltage of 3.2 V and current of 5 mA, the characteristics of the white LED being CIE = (0.4071, 0.3944), CCT = 3500 K and CRI = 91.3.

MYAS:xDy³⁺,yEu³⁺ can produce warm white light with CIE chromaticity coordinates of (0.4071, 0.3944) and relative color temperature of 3500 K.     

Anomalous boron isotope effects on electronic structure and lattice dynamics of CuB2O4

Copper metaborate had a unique crystal structure and exhibited noteworthy magnetic phase transitions at 21 and 10 K. The electronic structure and lattice dynamics of copper metaborate Cu¹¹B₂O₄ single crystals were investigated and compared with the optical properties of CuB₂O₄, to assess the boron isotope effect. The optical absorption spectrum at room temperature revealed two charge-transfer bands at approximately 4.30 and 5.21 eV with an extrapolated direct optical band gap of 3.16 ± 0.07 eV. Compared with the data on CuB₂O₄, the electronic transitions were shifted to lower energies upon the replacement of a heavier boron isotope. The band gap was also determined to be lower in Cu¹¹B₂O₄. Anomalies in the temperature dependence of the optical band gap were observed below 21 K. Furthermore, 38 Raman-active phonon modes were identified in the room-temperature Raman scattering spectrum of Cu¹¹B₂O₄, which were also observed in CuB₂O₄ with a shift to lower frequencies. No broadening caused by isotopic changes was observed. As the temperature decreased, phonon frequencies shifted to higher wavenumbers and the linewidth decreased. Anomalous softening in the Raman peaks below 21 K was also revealed.

Copper metaborate had a unique crystal structure and exhibited noteworthy magnetic phase transitions at 21 and 10 K.     

Erythrocyte membrane AChE,Na+, K+-ATPase and Mg2+ ATPase activities in mothers and their premature neonates in relation to the mode of delivery

Abstract

Aim. To investigate erythrocyte membrane AChE, Na⁺, K⁺-ATPase and Mg²⁺-ATPase activities in mothers and their full-term or premature newborns in relation to the mode of delivery. Methods. Blood was obtained from mothers pre- and post-delivery and the umbilical cord (CB) of their full-term newborns: Group A₁ (n = 16) born with vaginal delivery (VD), Group B₁ (n = 14) full-terms with scheduled cesarean section (CS), Group A₂ (n = 12) prematures with VD, Group B₂ (n = 14) prematures with CS. Total Antioxidant Status (TAS) and common laboratory tests were measured with routine methods, and the membrane enzyme activities spectrophotometrically. Results. TAS was reduced in mothers post VD and in the CB whereas remained unaltered in CS mothers and their newborns. AChE and Na⁺, K⁺-ATPase were increased in mothers post VD. AChE was lower in the CB of prematures than that of full-terms independently of the mode of delivery. Na⁺, K⁺-ATPase activity was increased in the groups of mothers post VD and decreased in prematures. The enzyme was higher in prematures with CS than that with VD. Mg²⁺-ATPase activity was unchanged. Conclusion. The increased maternal AChE and Na⁺, K⁺-ATPase activities may be due to the low TAS determined post VD, whereas their decreased activities in prematures to their immaturity.     

Serum ionized magnesium and calcium levels in adult patients with seizures

Objective. Prior studies have been equivocal about whether or not serum levels of the divalent ions calcium and magnesium are altered during different types of seizures. Magnesium is a potential modulator of seizure activity because of its ability to antagonize the excitatory calcium influx through the N‐methyl‐D‐aspartate (NMDA) receptor. We hypothesize that serum ionized levels of calcium (Ca²⁺) and magnesium (Mg²⁺) would be altered significantly during certain types of seizures. Material and methods. A convenience sample of seizure patients presenting to an emergency department (ED) were enrolled in this prospective study. Novel ion‐selective electrodes were used to measure Ca²⁺ and Mg²⁺. Data were reported as mean values±standard deviations. Group comparisons were analyzed by ANOVA with post‐hoc testing using the Bonferroni, or the Fisher exact test, where appropriate, α = 0.05 (two‐tailed). Results. Forty‐nine patients with seizure and 32 healthy racially matched controls were included in the study. Seizure patients had a significantly (p<0.001) lower mean Mg²⁺, but not total serum Mg and a significantly (p<0.001) higher Ca²⁺/Mg²⁺ ratio than that in controls. Conclusions. We were able to show significantly lower Mg²⁺ and higher ionized Ca²⁺/Mg²⁺ ratios in seizure patients compared with a racially matched control group.     

Calcium, Magnesium, and Phosphorus: Emergency Department Testing Yield

Objectives: To investigate how often the ED ordering of stat serum calcium (Ca⁺²), magnesium (Mg⁺²), and phosphorus (PO₄^-3) levels affected clinical treatment; to define the diagnoses of patients for whom Ca⁺², Mg⁺², and PO₄^-3 measurements did affect clinical therapy; and to suggest guidelines for more appropriate ordering of these laboratory tests. Methods: A retrospective chart review was performed in an academic teaching hospital. All adult ED patients who had Ca⁺², Mg⁺², or PO₄^-3 laboratory testing during the 9-month study period were included and evaluated for potential clinical impact of an abnormal Ca⁺², Mg⁺², or PO₄^-3 laboratory test. Results: 1,477 patients had Ca⁺², Mg⁺², or PO₄^-3 measured while in the ED during the study period. Of these, 260 patients (17.6%) had a total of 312 abnormal Ca⁺², Mg⁺², or PO₄^-3 values as defined by results exceeding ±15% of normal reference values. Of these, only 5 patients (0.3%) received treatment for abnormal values in the ED, while 75 patients (5.1%) were treated once admitted to the hospital. In this study, the only diagnostic groups to whom significant treatment was administered were diabetic patients (Ca⁺² and PO₄^-3); alcoholic patients (Mg⁺²); and renal failure patients (Ca⁺², Mg⁺², and PO₄^-3). Conclusion: These results suggest that stat Ca⁺², Mg⁺², and PO₄^-3 levels seldom affect clinical treatment in the ED. The frequency of ordering these tests may be reduced by obtaining Ca⁺², Mg⁺², or PO₄^-3 measurements only for patients known to be at risk for such abnormalities, based on their existing or suspected diagnoses. The authors suggest obtaining these tests, when indicated, on a “non-stat” basis, with the subsequent laboratory results becoming available in-hospital, where treatment is more likely to occur.     

Effect of WIN 64338, a B2 bradykinin receptor antagonist on guinea-pig tracheal smooth muscle cells in culture

Summary— This study investigated the effect of the non-peptidic B₂ bradykinin (BK) receptor antagonist WIN 64338 on BK binding and BK-induced inositol phosphate formation on guinea-pig tracheal smooth muscle cells in culture. The presence of specific and saturable binding sites for BK was demonstrated using [³H]BK. Scatchard analysis indicates a single population of binding sites for [³H]BK with a maximal density (B_max) of 245.4 ± 71 fmol/mg of protein and an equilibrium dissociation constant (K_d) of 87.7 ± 0.12 pM. The order of potency of B₂ BK receptor ligands was Hoe 140 = NPC 17731 > BK > WIN 64338 > D- Arg⁰[Hyp³, D-Phe⁷]-BK > > des-Arg⁹-BK, while the B₁ BK receptor antagonist, des-Arg⁹-[Leu⁸]-BK, was without effect on [³H]BK binding. These results demonstrate the presence of B₂ BK receptors on cultured tracheal smooth muscle cells. The cells were stimulated by BK, and inositol phosphate formation was determined by anion exchange chromatography. The stimulating effect of BK on inositol phosphate formation was concentration dependent (1 nM to 10 μM). The B₁ BK agonist des-Arg⁹-BK did not induce inositol phosphate formation. The order of potency of B₂ antagonists to inhibit BK-induced inositol phosphate formation was Hoe 140 = NPC 17731 > WIN 64338 > D-Arg⁰[Hyp³, D-Phe⁷]-BK. This study demonstrates that WIN 64338 is able to displace [³H]BK binding and to inhibit B₂-BK-induced inositol phosphate formation on cultured guinea-pig tracheal smooth muscle cells.     

Photoluminescence and afterglow behavior of Ce3+ activated Li2Sr0.9Mg0.1SiO4 phosphor

A blue emitting phosphor Li₂Sr_0.9Mg_0.1SiO₄:Ce³⁺, with long persistence, was synthesized via a high-temperature solid phase method. According to the X-ray diffraction analysis result, the introduction of Mg²⁺ and Ce³⁺ ions has no influence on the structure of the host material. Typical 5d-²F_5/2 and 5d-²F_7/2 transitions of Ce³⁺ ions were detected by PL spectra, which corresponded to the CIE chromaticity coordinates of x = 0.1584, y = 0.0338. An optimal doping concentration of Ce³⁺ was determined as of 0.4 at%. Furthermore, the Li₂Sr_0.9Mg_0.1SiO₄:Ce³⁺ phosphor showed a typical triple-exponential afterglow behavior when the UV source was switched off. The highest lifetime of the electrons within the material reached a value of 73.9 s. Thermal stimulated luminescence study indicated that the afterglow of Li₂Sr_0.9Mg_0.1SiO₄:Ce³⁺ was due to the recombination of the electrons with holes released from the traps generated by the doping of Ce³⁺ ions in the Li₂Sr_0.9Mg_0.1SiO₄ host. The afterglow mechanism of Li₂Sr_0.9Mg_0.1SiO₄:Ce³⁺ is illustrated and discussed in detail on the basis of the experimental results.

A blue emitting phosphor Li₂Sr_0.9Mg_0.1SiO₄:Ce³⁺, with long persistence, was synthesized via a high-temperature solid phase method.     

Magnesium Attenuates the Neutrophil Respiratory Burst in Adult Asthmatic Patients

Introduction: IV magnesium (Mg²⁺) has been proposed as an emergent treatment for acute asthma exacerbations. Recent studies have focused on the effects of Mg²⁺ on bronchial smooth muscle, yet asthma is primarily an inflammatory disease. Objective: To assess the effects of Mg²⁺ on the neutrophil respiratory burst of adult patients with asthma. Methods: A prospective, blind study of volunteer adult asthmatic patients was performed. The patients' polymorphonuclear neutrophils (PMNs) were isolated, purified, and placed into phosphate-buffered saline with the following test conditions: concentrations of magnesium chloride (MgCl₂) added: 0 mmol MgCl₂, 1 mmol MgCl₂ (low), and 10 mmol MgCl₂ (high) both with and without the calcium (Ca) ionophore A23187 (0.1 mmol). PMNs were activated using N-formyl-methionyl-leucyl-phenylalanine (fMLP) (10 pmol), and the production of superoxide (O^-₂) was measured by the spectrophotometric reduction of cytochrome c. Results: Mg²⁺ reduced activated PMN O^-₂ production compared with that for no Mg²⁺ (1.0 ± 0.1 nmol O^-₂/5 ± 10⁵ PMN/min) in both low (-0.52* ± 0.3 nmol O^-₂/5 ± 10⁵ PMN/min) and high (-0.76* ± 0.3 nmol O^-₂/5 ± 10⁵ PMN/min; *p < 0.05) concentrations. The addition of A23187 increased O^-₂ production in both the high (0.53* ± 0.02 nmol O^-₂/5 ± 10⁵ PMN/min) and the low (1.5* ± 0.6 nmol O^-₂/5 ± 10⁵ PMN/ min) Mg²⁺ groups, with no change in the control group (1.2 ± 0.2 nmol O^-₂/10⁵ PMN/min). Conclusions: In clinically relevant concentrations, Mg²⁺ attenuates the neutrophil respiratory burst in adult asthmatic patients. Mg²⁺ appears to affect PMNs by interfering with extracellular Ca²⁺ influx. Mg²⁺ may have a beneficial anti-inflammatory effect in asthmatic individuals.     

B12X11(H2)−: exploring the limits of isotopologue selectivity of hydrogen adsorption

We study the isotopologue-selective binding of dihydrogen at the undercoordinated boron site of B₁₂X₁₁⁻ (X = H, F, Cl, Br, I, CN) using ab initio quantum chemistry. With a Gibbs free energy of H₂ attachment reaching up to 80 kJ mol⁻¹ (ΔG at 300 K for X = CN), these sites are even more attractive than most undercoordinated metal centers studied so far. We thus believe that they can serve as an edge case close to the upper limit of isotopologue-selective H₂ adsorption sites. Differences of the zero-point energy of attachment average 5.0 kJ mol⁻¹ between D₂ and H₂ and 2.7 kJ mol⁻¹ between HD and H₂, resulting in hypothetical isotopologue selectivities as high as 2.0 and 1.5, respectively, even at 300 K. Interestingly, even though attachment energies vary substantially according to the chemical nature of X, isotopologue selectivities remain very similar. We find that the H–H activation is so strong that it likely results in the instantaneous heterolytic dissociation of H₂ in all cases (except, possibly, for X = H), highlighting the extremely electrophilic nature of B₁₂X₁₁⁻ despite its negative charge. Unfortunately, this high reactivity also makes B₁₂X₁₁⁻ unsuitable for practical application in the field of dihydrogen isotopologue separation. Thus, this example stresses the two-edged nature of strong H₂ affinity, yielding a higher isotopologue selectivity on the one hand but risking dissociation on the other, and helps define a window of adsorption energies into which a material for selective adsorption near room temperature should ideally fall.

The extreme H₂ affinity of B₁₂X₁₁⁻ gives a glimpse of how higher selectivities in adsorptive isotopologue separation may be achieved.