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Halide perovskites are promising emitters for light‐emitting diodes (LEDs) due to their outstanding optoelectronic properties, i.e., tunable bandgap, high photoluminescence quantum efficiency, and excellent color purity. However, in contrast to their green and red cousins, the present blue perovskite LEDs are still suffering from poor operational lifetime and electroluminescence shift during bias operation, hindering their practical applications in full‐color information displays. Developing rational strategies to achieve efficient and stable blue perovskite LEDs is one of the urgent tasks in this community. Herein, through substituting the Pb site with strontium ions, blue perovskite films with stable emission under relatively harsh working conditions, i.e., high electrical bias, constant thermal heating, and UV illumination, are obtained, which accordingly guarantees spectrally stable blue perovskite LEDs with external quantum efficiency of 4.1%. Moreover, different alkaline‐earth metal ions are also investigated to further explore the effects of B‐site ion substitution on the performance of perovskite LEDs. This work demonstrates an alternative path for the development of spectral‐stable blue perovskite LEDs. [ABSTRACT FROM AUTHOR]

A carboxymethyl chitosan (O-CMC) gel was prepared by crosslinking and functionalizing with ethylenediaminetetraacetic acid (EDTA) using a one-pot reaction under mild conditions. Structural characterizations have revealed that the prepared O-CMC/EDTA gel has 3D porous structure with abundant carboxyl groups distributed in the pores. The prepared O-CMC/EDTA gel was used to adsorb Sr(II) ions in water while X-ray photoelectron spectroscopy (XPS) was used to explore the adsorption mechanism. In order to analyze the adsorption process, we performed the adsorption kinetics and isotherms. The results show that the maximum adsorption capacity of O-CMC/EDTA for Sr (II) ions is about 105.81 mg/g at pH = 7. Notably, it exhibited fairly high compression elasticity due to multiple hydrogen bonds in the network. The showed no deformation after 30 continuous compression cycles. The ratio of O-CMC:EDTA significantly influences the adsorption property by affecting the crosslinking degree as well as the number of active sites. The high adsorption capacity, elasticity, and reusability have demonstrated that the prepared material is an effective and promising adsorbent for Sr(II) removal. [ABSTRACT FROM AUTHOR]

The equilibrium partition coefficient of strontium (K Sr eq ) between aqueous solutions and calcite is still poorly known, even though it is a valuable parameter for studies involving the use of calcite trace element geochemistry for reconstructing paleoenvironments and fluid chemistry. In this paper we use pore fluid data from deep sea carbonate sediments to constrain K Sr eq at low temperature (5–17 °C) and show that the derived values are consistent with laboratory calcite precipitation experiments at 25 °C when the latter are corrected for kinetic effects. Using these low-temperature values, and experimental data available at higher temperature based on replacement reactions, we show that all of the data can be accounted for by a single formulation based on the thermodynamics of the relevant components of seawater-like fluids and the SrCO 3 –CaCO 3 solid solution. The value of pore fluid data is that the fluids and carbonate sediment have been in contact for millions of years so local equilibrium is approached, the overall system can be treated with one-dimensional models, and the temperature is constrained. These natural systems provide an opportunity to investigate low-temperature equilibrium in the carbonate system that is difficult to probe in the laboratory because of sluggish exchange kinetics. We estimate values of K Sr eq using measured Sr and Ca concentrations in pore fluid and sediment solid calcite and a numerical model of sediment deposition, reaction and transport. The model is used to fit the Sr, Ca, and sulfate concentrations observed in pore fluids of several calcite-dominated sites that we believe are optimal for understanding Sr partitioning. Combining the pore fluid results with experimental measurements at higher temperature results in the following expression which applies for the temperature range 0–200 °C: K S r eq T = 0.025 exp Δ G r , 0 R 1 298.15 - 1 T where ΔG r,0 is the free energy change associated with the exchange reaction and temperature is in Kelvin. The uncertainty is approximately ±20%. Recently summarized thermodynamic data yield ΔG r,0 = 1.2 kcal/mol (5.0 kJ/mol) which fits well the lower limit of the high temperature data. The corresponding activity coefficient for the SrCO 3 component in the calcite crystal structure is 5.4 for the lower value of ΔG r,0 , and 3.17 for the higher value. The derived low-temperature values of K Sr eq of 0.020 to 0.025 (for 0 °C to 25 °C) have implications for models of marine carbonate diagenesis, and the interpretation of vein carbonate Sr/Ca in oceanic crust. Published data showing much higher K Sr values in Mg-bearing solutions are not representative of equilibrium values for either Mg or Sr. [ABSTRACT FROM AUTHOR]

The in vitro bioactivity and in vivo bone neoformation in critical-size bone defects of a glass-ceramic material containing strontium ions (Sr2+) were evaluated in the present study as well as the antimicrobial effect against oral pathogens. A glass-ceramic bioactive material in powder (CP), based on the composition of S53P4 bioactive glass, was produced by partially replacing calcium with SrO using the sol-gel route. The amount of SrO added was 2.2 wt% (CPSr12.5) and 5.0 wt% (CPSr25). The amount of Sr2+ ions released by the CP increase with time achieving 18 mg/L at 6 h and the release rate decreased at longer times. pH values higher than 10 were obtained in the first 6 h, in agreement with an inhibitory microbial effect. These materials showed in vitro bioactivity, with total surface coated by hydroxyapatite (HA) after 7 days of immersion in simulated body fluid (SBF). The pH of SBF increased rapidly after immersion of CP, reaching a maximum value of 8.72 after 168 h. HA formation was observed in vitro for all samples. On microtomography and histomorphometric analysis, CPSr25 showed higher values than CP without Sr2+ (CPSr0) for bone volume (p = 0.016), density (p = 0.016) and neoformation area (p = 0.025) at 28 days. Histological analysis revealed higher degree of vascularization after 28 days for CPSr25 when compared to CPSr0 (p = 0.003). In addition, CP showed an inhibitory effect on oral pathogens. Substitution of CaO by SrO (CPSr25) presented the best results on the healing of critical-size bone defects, as evidenced by microtomographic and histological analyses. These data confirmed that higher concentrations of Sr2+doped CP materials are potential alternatives to improve bone healing and regeneration in critical-size bone defects. [ABSTRACT FROM AUTHOR]

Hydrazide based phosphine linkers were prepared by the condensation reaction of hydrazide of the type RC(O)NHNH2 (R = t‐BuPh) with dppe (1,2‐bis (diphenylphosphino)ethane) to produce the corresponding product of the type RCONHN=PPh2CH2CH2PPh2 = NNHCOR (2). The silylation product RC (OSiMe3) = N‐N=PPh2‐CH2CH2PPh2 = N‐N=C (OSiMe3)R (3) derived from 2 reacts with halosilanes to yield novel hypercoordinate silicon (IV) complexes (4–7). All the products are well characterized by the spectroscopic and analytical data. The DFT calculations indicate that both charge density and electronegativity of the atoms surrounding a magnetically active nucleus have an effect on the chemical shift values. An increase in the electronegativity of the substituted atoms is reflected by the natural hybrids, which causes deshielding of the magnetic Si and P nuclei from the external magnetic field to an increasing level. As a consequence of this, the 29Si and 31P NMR chemical shifts increase for 4–7 thus augmenting the experimental interpretations. Since the phosphorus hydrazide based hypercoordinate Si (IV) complexes are the rich sources of P, and Si directly from a single molecule, the present work also demonstrates the preparation of spherically shaped strontium phosphosilicate (Sr5(PO4)2SiO4) by the sol–gel method. [ABSTRACT FROM AUTHOR]

A gamma induced copolymerization process was applied to modify hydroxyapatite prepared from eggshell. The composite material was characterized by different physicochemical methods, and then it was used for removal of Sr2+ and Co2+ ions from aqueous solutions as a function of pH, temperature, time, interfering ions, and initial Sr2+ and Co2+ concentrations by applying batch adsorption technique. The maximum removal was obtained at pH 6, and 8 for Sr2+ and Co2+ ions respectively. Sorbents regeneration was successful with HCl eluent. Results showed good fitting to Freundlich isotherm than Langmuir. Kinetic data was well described by pseudo-second order equation. [ABSTRACT FROM AUTHOR]

A gamma induced copolymerization process was applied to modify hydroxyapatite prepared from eggshell. The composite material was characterized by different physicochemical methods, and then it was used for removal of Sr2+ and Co2+ ions from aqueous solutions as a function of pH, temperature, time, interfering ions, and initial Sr2+ and Co2+ concentrations by applying batch adsorption technique. The maximum removal was obtained at pH 6, and 8 for Sr2+ and Co2+ ions respectively. Sorbents regeneration was successful with HCl eluent. Results showed good fitting to Freundlich isotherm than Langmuir. Kinetic data was well described by pseudo-second order equation. [ABSTRACT FROM AUTHOR]

Hydrazide based phosphine linkers were prepared by the condensation reaction of hydrazide of the type RC(O)NHNH2 (R = t‐BuPh) with dppe (1,2‐bis (diphenylphosphino)ethane) to produce the corresponding product of the type RCONHN=PPh2CH2CH2PPh2 = NNHCOR (2). The silylation product RC (OSiMe3) = N‐N=PPh2‐CH2CH2PPh2 = N‐N=C (OSiMe3)R (3) derived from 2 reacts with halosilanes to yield novel hypercoordinate silicon (IV) complexes (4–7). All the products are well characterized by the spectroscopic and analytical data. The DFT calculations indicate that both charge density and electronegativity of the atoms surrounding a magnetically active nucleus have an effect on the chemical shift values. An increase in the electronegativity of the substituted atoms is reflected by the natural hybrids, which causes deshielding of the magnetic Si and P nuclei from the external magnetic field to an increasing level. As a consequence of this, the 29Si and 31P NMR chemical shifts increase for 4–7 thus augmenting the experimental interpretations. Since the phosphorus hydrazide based hypercoordinate Si (IV) complexes are the rich sources of P, and Si directly from a single molecule, the present work also demonstrates the preparation of spherically shaped strontium phosphosilicate (Sr5(PO4)2SiO4) by the sol–gel method. [ABSTRACT FROM AUTHOR]

Inspired by significant local distortions found near vacancies in a neutron pair distribution function analysis study (G. King et al., Inorg. Chem. 2012, 51, 13060) of Sr2MSbO5.5 (M = Ca and Sr), this computational study finds minimum‐energy structures with these and related distortions using density functional theory (DFT) with the Perdew‐Burke‐Ernzerhof (PBE) functional as implemented in the Vienna Ab Initio Simulations Package (VASP) (G. Kresse and J. Furthmüller, Phys. Rev. B, 1996, 54, 11169; G. Kresse and J. Hafner, Phys. Rev. B, 1993, 47, 558; G. Kresse and J. Furthmüller, Comput. Mater. Sci., 1996, 6, 15). All structures were optimized using the conjugate gradient method. The global minima found for both systems featured trigonal bipyramid SbO5 structures and edge sharing with M‐centered polyhedra. However, while calcium ions occupied full and partial octahedra, the larger strontium ions were more commonly found in full and partial pentagonal bipyramids. Molecular dynamics with velocity rescaling at 1200 K revealed movements of the oxygen vacancy via polyhedral rotations. This work highlights the need to consider both square pyramid to trigonal bipyramid rearrangements around small ions and rotational polyhedral movements in simulating oxygen vacancy conduction in oxygen‐deficient double perovskites. [ABSTRACT FROM AUTHOR]

Most of previous works studied the bioactivity of tertiary soda-lime-borate as in vitro method, but, there have been no previous studies investigated the in vivo compatibility of such glass. This work was mainly aimed at in vivo assessment of bone formation of tertiary soda-lime-borate bioactive glass doped with Sr. the glass composition was based on 60 B2O3–20 Na2O–(20-x) CaO–xSrO (wt%), where, x = 0 and 10 wt% (samples encoded B0 and BS, respectively). The in vivo test was conducted in femoral bone defect of Sprague-Dawley adult male rats after 3 and 6 weeks post-surgery using the histological analyses and bone formation markers (alkaline phosphatase (ALP) and osteocalcin (OCN)). Moreover, the possible systemic toxicity was studied using different biochemical analyses (alanine transaminase, aspartate transaminase, urea and creatinine). The result of bone markers showed that serum OCN level increased in rat implanted with sample B0 than that observed in sample BS at 3 and 6 weeks post-implantation, while this finding was reversed in ALP activity. In vivo bioactivity test showed that implantation of all borate glasses did not demonstrate local or general complications in all rats, and they exhibited nearly complete bone mineralization. However, BS glass was formed more new bone % than B0 one in long implantation time. In conclusion, the synthesized bioactive borate glasses were safe materials, and introducing of Sr in the glass was enhanced formation of new bone throughout long time of implantation. Accordingly, this glass can be used as a potential substitute for bone regenerative materials and a hosting for strontium ions delivery. [ABSTRACT FROM AUTHOR]

Various toxic metal ions were successfully removed from solid matrix into supercritical CO2 (scCO2) by open-chain crown ether bridged diphosphates at 313.15 K and 20 MPa, these diphosphates with different ester side chains and different length of ethylene oxide bridge group are highly soluble in supercritical CO2. The extraction efficiency (E%) of heavy metals is between 55 and 89%. Mulliken charge distribution of ligand's P=O coordination group was calculated to indicate the stability of metal complex. The ligand structure effects and the rationale for different selectivity were discussed. In addition, binding property of these diphosphates towards the alkaline earth metals was further studied following the same extraction procedures. Alkaline earth metal ions Ca2+, Sr2+ and Ba2+ were extracted with E% at 49–74%, 50–73% and 16–64%, respectively. DFT calculations were performed to investigate the interaction energy of the complexes and the correlation with the E% was discussed. [ABSTRACT FROM AUTHOR]

Strontium chromate (SrCrO4) nanorod particles were successfully prepared at low temperature using the chemical precipitation method. In this synthesis process, sodium dichromate and celestite mineral, which is a water-insoluble mineral, were used as starting materials. The morphology and size of the particles obtained were determined by SEM-EDAX analysis. XRD analysis of the synthesized particles revealed an SrCrO4 phase and other phases. The effects of different molar ratios on SrCrO4 formation were investigated. The addition of NaCl has been found to play a significant role in the formation of strontium chromate nanorods, in particle size, particle shape and product composition. [ABSTRACT FROM AUTHOR]

90Sr (t1/2 = 28.8 a), one of the most significant fission products in high-level radioactive liquid waste (HLLW), contributes to a large part of the heat load and radiation. Removal of 90Sr from the HLLW is beneficial for the final treatment of nuclear waste. In this paper, the extraction of Sr2+ was carried out using dicyclohexano-18-crown-6 (DCH18C6) in a variety of diluents including conventional organic solvents and novel ionic liquid solvents. The effect of several factors, such as nitric acid concentration, crown ether concentration and initial strontium concentration on the extraction of Sr2+ have been studied comprehensively. The higher distribution ratio and the stripping efficiency of Sr2+ were obtained with the binary diluents consisted of n-octanol and acetylene tetrachloride, which were compared with that using pure n-octanol as diluent. As for the CnmimNTf2 (n = 2, 4, 6) ionic liquid solvent systems, the distribution ratio of Sr2+ was much higher in the nitric acid medium with low concentration than in the traditional solvent systems. The results showed that DC2mimNTf2 > DC4mimNTf2 > DC6mimNTf2, which indicated that shorter carbon chain benefits the extraction of Sr2+. [ABSTRACT FROM AUTHOR]

In this paper, we produced Saccharomyces cerevisiae (S. cerevisiae)-Fe3O4 (S@F) by a low-cost and self-assembly technique called the one-step method. The results of SEM and XRD showed that nano-Fe3O4 particles had successfully attached to the surface of S. cerevisiae and the results of TEM indicted that nano-Fe3O4 particles had a uniform core–shell structure to the composite S. cerevisiae with a magnetic core. The results of FTIR showed that nano-Fe3O4 particles were mainly combined with S. cerevisiae through chemical bonds. Meanwhile, the VSM analysis and SBET results reflected that S@F had a good magnetization and big surface area. Strontium ion sorption of S@F was independent of ionic concentration and pH, indicating that the complexion and electrostatic attraction dominated the sorption. Besides, the results of VSM analysis and SBET reflected that S@F had good magnetization and large surface area, and we found that the adsorption capacity of S@F for strontium ions was independent of ion concentration and pH, which indicated that complexation and electrostatic attraction played a dominant role in the adsorption process. S@F needed 16 h to get the maximum from our pseudo-second-order kinetic study analysis and The maximum adsorption capacity of S@F calculated by the Langmuir isotherm model is 20.47 mg g−1. Moreover, whether it is in a single working condition, in simulated low-level wastewater or a radiation environment, S@F always has good regeneration ability and reusable performance (after three cycles, S@F almost maintains the same adsorption capacity). In summary, these findings indicate that S@F can be a renewable material for nuclear wastewater treatment. [ABSTRACT FROM AUTHOR]

Ketone synthesis via the addition of organometallic reagents to amides has long been investigated. In many cases, it is necessary to control the solvent, reaction temperature, and adhere to strict nucleophile stoichiometry for each combination of amide and organometallic reagent. Strontium, with an electronegativity comparable to lithium but a larger ionic radius, may display high reactivity with the characteristics of monoalkylation. Here, we show that the monoalkylation of various N,N‐dimethylamide derivatives with alkyl iodides to afford the ketones proceeds smoothly under generally mild temperature conditions. By this method, not only aromatic amides but also α‐proton‐bearing aliphatic amides were suitable substrates for ketone synthesis. In addition, we found that tetramethylurea, typically a poor electrophile, also reacted to afford benzophenone in good yield with excellent selectivity. [ABSTRACT FROM AUTHOR]

The escalation of fine particulate matter (PM) air pollution has recently become a global concern. Evidence is fast accumulating on PM exposure-related skin damage. The present study explored the therapeutic potentials of fucoidan purified from Sargassum natans against damaging effects of PM exposure on human HaCaT keratinocytes. Fucoidan (SNF7) was purified from S. natans by an enzyme-assisted extraction and purified by anion exchange chromatography. SNF7 (≈50 kDa) was identified as a fucoidan containing 70.97% fucose and 36.41 ± 0.59% of sulfate. Treatment of fine dust from Beijing, China (CFD) increased intracellular ROS levels in HaCaT cells triggering DNA damage and apoptosis. Treatment of SNF7 dose-dependently attenuated CFD-induced surge of intracellular ROS levels in keratinocytes by increasing antioxidant defense enzymes. Moreover, SNF7 chelated metal ions Pb2+, Ba2+, Sr2+, Cu2+, Fe2+, and Ca2+ coming from CFD. The results substantiated the potential therapeutic effects of SNF7 against CFD-induced oxidative stress. Further studies could promote SNF7's use as an active ingredient in cosmetics. Unlabelled Image • Fucoidans are renowned for reducing cellular oxidative stress. • The untapped alga Sargassum natans is highly abundant along the west coast of Sri Lanka. • A low molecular weight fucoidan (SNF7) was purified and characterized from S. natans. • SNF7 reduced fine dust-induced ROS generation and protected keratinocytes against apoptosis. • Effects might contribute to the enhancement of antioxidant defense mechanisms. [ABSTRACT FROM AUTHOR]

In the process of in situ synthesis using ultrasound, a magnetoactive sorbent based on humic acid and magnetite was produced for the extraction of heavy metals from industrial wastewater by magnetic solid-phase extraction. When exposed to ultrasound, substances are dispersed, which results in an increase in the specific surface area of the studied sorbent and the opening of inaccessible pores on its surface. Humic acid, which is part of the magnetoactive sorbent, is a stabilizer of the size of magnetite nanoparticles. The composition and sorption properties of a magnetoactive compound with respect to heavy metal ions Pb(II), Cu(II), Zn(II), Sr(II), Fe(III), and Al(III) were investigated. The dependence of the sorption value of the studied metal ions on the temperature and pH of the waste water was examined, the sorption capacity of the magnetoactive compound and the degree of waste water purification were determined. It was found that the maximum extraction of metal ions Pb(II), Cu(II), Al(III), Zn(II), Sr(II), Fe(III) from wastewater occurs at 25°C and pH 6.5, after additional sorption post-treatment, the content of Pb(II), Cu(II) and Zn(II) ions decreases by more than 15 times, and of Al(III), Pb(II), and Fe(III) ions, more than 12 times. The maximum degree of water purification from metal ions Pb(II), Cu(II), Al(III), Zn(II), Sr(II), and Fe(III) is 98.8, 83.1, 81.5, 78.1, 69.5, and 42.5%, respectively. [ABSTRACT FROM AUTHOR]

The aim of the present work is titanium silicate influence on the zinc and strontium migration in the aquatic environment. The adsorption capacity of titanium silicate toward zinc and strontium ions was investigated. With the aid of a fluorescent X-ray analyzer and energy dispersive spectroscopy the composition of the sorbent formed was determined as well as zinc and strontium presence on the surface of the sorbent after the sorption process. It was shown, that adsorption of zinc and strontium by titanium silicate strongly depends on time of interaction and solution acidity and increases with increasing of both parameters. It was established, that for the initial concentration of zinc and strontium at the level of 0.005M the presence of ions that cause the natural mineralization of water does not affect their adsorption extraction. [ABSTRACT FROM AUTHOR]

The Raman OH stretching vibration band of liquid water is asymmetric and multimode superimposed and is susceptible to variations in salinity, pressure, and temperature. Ions have non-negligible influences on the Raman O–H stretching band of water because these ion–water interactions are stronger than those between water molecules. The determination of molecular-level details of hydration processes remains a great challenge, both experimentally and theoretically. The effects of 11 common ions on the O–H stretching band of liquid water are characterized with a skewing parameter introduced to describe the distortion caused by ion hydration. With increasing salt concentration, the symmetry of the Raman O–H stretching band decreases as the skewing parameter value increases. Therefore, ions primarily break the tetrahedral hydrogen bonding and promote the formation of partly hydrogen-bonded and free water molecules. Additionally, the effects of anions are much stronger than those of cations due to the asymmetric charge distribution in the dipoles of H2O. It is revealed that the influences of the common ions on the Raman OH stretching band of water are in the following order: I– > Br– > Cl– > F–, SO 4 2 − > CO 3 2 − , K+ > Na+, and Sr2+ > Ca2+ > Mg2+. For ions with the same charge, the order of their effects on the Raman O–H stretching band of water is usually the same as the order of their ionic crystal radii but the reverse order of their hydrated radii. [ABSTRACT FROM AUTHOR]

Considering the intrinsic poor self-healing capacity of meniscus, tissue engineering has become a new direction for the treatment of meniscus lesions. However, disturbed by mechanical stability and biocompatibility, most meniscus implants fail to relieve symptoms and prevent the development of osteoarthritis. The goal of this study was to develop a potential meniscal substitute for clinical application. Here, silk fibroin with good mechanical performance and biocompatibility, and strontium ion acting as bioactive factor, were incorporated with Ɛ-Polycaprolactone to fabricate a meniscus scaffold (SP-Sr). By the wet-electrospun method, the 3D SP-Sr provided suitable pore size (100–200 μm) and enough mechanical support (61.6 ± 2.9 MPa for tensile modulus and 0.11 ± 0.03 MPa for compressive modulus). Moreover, after addition of Sr2+, the SP-Sr seeded by rabbit adipose tissue-derived stromal cells (rADSCs) showed the highest secretion with 2.61- and 2.98-fold increase in collagen and aggrecan, respectively, compared with SF/PCL group. And the extracellular matrix related genes expression in SP-Sr also showed upregulation results. Particularly, the expression of the collagen II gene, which played a crucial role in the formation of meniscal inner avascular region, showed a 9-fold increase in SP-Sr compared with pure PCL group. Furthermore, the MRI results of SP-Sr implanted in rabbits with total meniscectomy for 6 months demonstrated effective prevention of meniscus extrusion and relieving joint space narrowing compared with meniscectomy group. And the effects of cartilage protection and delaying osteoarthritis development were confirmed by Pathological examination. Especially, after 6-month implantation, the neo-menisci showed similar structural constituent and mechanical performance. Meniscus regeneration faces great challenge due to the meniscus having limited healing potential owing to its anisotropic structure, its hypocellularity and hypovascularity. The present tissue engineering solutions have failed to maintain the biological function for meniscus reconstruction in vivo because of fragile and poor biocompatible materials, leading to long-term joint degeneration. The goal of this study was to develop a meniscal substitute potential for clinical application. Here, silk fibroin and strontium were incorporated with Ɛ-Polycaprolactone by wet-electrospinning method to fabricate a meniscus scaffold (SP-Sr). The 6-month implantation results revealed that SP-Sr scaffold was effective in preventing meniscus extrusion, cartilage protection and delaying osteoarthritis development, and the regenerated menisci showed similar structural constituent and mechanical performance. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• A modified molten salt synthesis was explored. • The chemical composition of the obtained particles was close to the stoichiometric ratio. • Raising calcination temperature could promote the particles growth along diameter direction. • This will be an effective way to fabricate the ideal template for the preparation of textured ceramics. A modified molten salt synthesis was explored to investigate the A-site occupancy (K+ and Sr2+) and morphology change of the KSr 2 Nb 5 O 15 (KSN) microcrystalline. The difference between this work and the conventional method was that the raw materials were pressed into blocks under a certain pressure before calcination. The effects of pressure and temperature on the chemical composition and particle morphology of KSN powder were analyzed. The composition and morphology of the obtained powder varied significantly with the various pressures and temperatures. It was found that as the pressure and temperature increased, more Sr ions tended to occupy vacant A sites and the particle size become uneven. Increasing pressure benefited to the formation of slender particles, while raising calcination temperature could promote the particles growth along diameter direction. The results of the KSN ceramics suggested that this will be an effective way to fabricate the ideal template for the preparation of textured ceramics by adjusting the pressure and temperature. [ABSTRACT FROM AUTHOR]

In the present work, well‐recognized La0.8Sr0.2MnO3 (LSM) system as cathode for IT‐SOFC is prepared by using different process control reagents (PCAs) such as stearic acid and salicylic acid with varying grinding times. This is the first attempt to develop LSM by using PCAs in mechanochemical synthesis. By using stearic acid single cubic phase, LSM material is obtained at 3 h of grinding (LSM‐St). However in case of salicylic acid, the respective phase of La0.8Sr0.2MnO3 is achieved for 5 h of grinding (LSM‐Sa) and without PCA the same phase is obtained for 7 h of grinding (LSM‐Wt). X‐Ray diffraction confirms single crystalline cubic phase of as‐synthesized LSM by PCAs and without PCA. All the samples are sintered at 700 °C to improve the degree of crystallinity. Scanning electron microscopy images of as‐synthesized samples reveal highly agglomerate fine‐scale grains. The temperature dependence of direct current conductivity curve exhibits linear dependence of conductivity with temperature, which is found maximum for LSM‐St as compared to other two samples. Symmetric cells in the configuration given by—composite cathode/electrolyte/composite cathode—are fabricated using spin coating technique. The area specific resistance is minimum for LSM‐St based symmetric cell and correlated with the maximum conductivity. [ABSTRACT FROM AUTHOR]

Strontium (Sr) isotope ratios (87Sr/86Sr) measured in human skeletal material can increase one's understanding of the residential behaviour and resource‐acquisition strategies of past populations. The paper maps bioavailable 87Sr/86Sr variation in 183 plant and soil samples across Cambodia. Bioavailable 87Sr/86Sr, as measured in plants, differs significantly between four major geological units. The data set will support future investigations of skeletal material from Cambodian archaeological sites. Baseline 87Sr/86Sr data should be applied judiciously to skeletal populations, and in concert with other lines of evidence, to identify potential geographical outliers rather than to ascribe specific locations from which individuals may have moved. [ABSTRACT FROM AUTHOR]

In the present work, well‐recognized La0.8Sr0.2MnO3 (LSM) system as cathode for IT‐SOFC is prepared by using different process control reagents (PCAs) such as stearic acid and salicylic acid with varying grinding times. This is the first attempt to develop LSM by using PCAs in mechanochemical synthesis. By using stearic acid single cubic phase, LSM material is obtained at 3 h of grinding (LSM‐St). However in case of salicylic acid, the respective phase of La0.8Sr0.2MnO3 is achieved for 5 h of grinding (LSM‐Sa) and without PCA the same phase is obtained for 7 h of grinding (LSM‐Wt). X‐Ray diffraction confirms single crystalline cubic phase of as‐synthesized LSM by PCAs and without PCA. All the samples are sintered at 700 °C to improve the degree of crystallinity. Scanning electron microscopy images of as‐synthesized samples reveal highly agglomerate fine‐scale grains. The temperature dependence of direct current conductivity curve exhibits linear dependence of conductivity with temperature, which is found maximum for LSM‐St as compared to other two samples. Symmetric cells in the configuration given by—composite cathode/electrolyte/composite cathode—are fabricated using spin coating technique. The area specific resistance is minimum for LSM‐St based symmetric cell and correlated with the maximum conductivity. [ABSTRACT FROM AUTHOR]

Study of multiferroic Y1−xSrxCrO3 (x = 0.0, 0.1) chromite obtained through solid-state reaction technique is presented. The Rietveld refinement of the XRD profile shows the orthorhombic Pbnm crystal symmetry of the system. The bandgaps of YCrO3 and Y0.9Sr0.1CrO3 samples are found as ~ 2.31 and ~ 2.23 eV, respectively. The FTIR spectra peaks show a red shift in the case of Sr2+ ion doping in YCrO3 indicating the reduction in cell volume. Two dielectric relaxation peaks are observed in the YCrO3 , whereas Y0.9Sr0.1CrO3 shows only one broad peak that is found to be extremely frequency dependent. The dielectric peak maxima shifts to higher temperatures with an increase in frequency in both the samples. This kind of dielectric variation is indicating a relaxor type of dielectric material. It is noted that the observed conductive process is closely associated with thermally stimulated oxygen vacancies. The P–E loops of both the samples have completely round shape with maximum polarization (Pmax) being observed at zero electric field. For YCrO3, the mechanism of leakage current conduction is in good agreement with the Ohmic conduction mechanism, whereas Y0.9Sr0.1CrO3 agrees well with space charge-limited conduction mechanism. The decreased bandgap and leakage current makes the Sr2+ ion doping beneficial for various electronic applications. [ABSTRACT FROM AUTHOR]

A foreign dynasty, known as the Hyksos, ruled parts of Egypt between c. 1638–1530 BCE. Their origins are thought to be rooted in the Near East, which is supported by architectural features and grave accoutrements of Tell el-Dabca. In this former Hyksos capital in the Eastern Nile Delta, burial culture is characterized by a blend of Egyptian and Near Eastern elements. However, investigations are still ongoing as to where the Hyksos came from and how they rose to power. The aim of this study is to elucidate the question of possible provenience. We present the results of strontium isotope (87Sr/86Sr) ratios of human tooth enamel (n = 75) from Tell el-Dabca, focusing on comparing pre- and during Hyksos rule and sex-based differences. An influx of non-locals can be observed in the pre-Hyksos period (12th and 13th Dynasties, c. 1991–1649 BCE) during the constitution of this important harbor town, while the number of individuals already born in the Delta is larger during the Hyksos period. This is consistent with the supposition that, while the ruling class had Near Eastern origins, the Hyksos' rise to power was not the result of an invasion, as popularly theorized, but an internal dominance and takeover of foreign elite. There is a preponderance of non-local females suggesting patrilocal residence. We discuss our findings against the current evidence of material culture and historiography, but more investigation in Near Eastern comparative sites has to be conducted to narrow our future search for the actual origins of the Hyksos. [ABSTRACT FROM AUTHOR]

• Sr ion doped Ca 3 (PO 4) 2 for varying doping wt.% (10, 20, 30, 40) was synthesized by a facile co-precipitation method. • Structural, morphologic and optical properties were studied in detail. • Photocatalytic degradation experiments were evaluated using RhB dye as a molecule model. • 30 wt% Sr-Ca 3 (PO 4) 2 solid solution shows the highest photocatalytic performance for RhB degradation. • Photodegradation mechanism was discussed. Well-crystallized Ca 3 (PO 4) 2 doped and un-doped nano-particles with the maximum strontium content (40 wt% Sr) followed by calcination at 800 °C for 3 h were synthesized via facile co-precipitation method. DTA/TGA, X-ray diffraction (XRD), energy dispersive scanning electron microscopy (SEM/EDX), UV–vis diffuse reflectance spectrum (UV–vis DRS), Raman spectroscopy and photoluminescence (PL) techniques were used for material characterization. The (XRD) patterns of as-synthesized Sr-doped Ca 3 (PO 4) 2 solid solution samples exhibited a systematic shift toward lower angles by possessing a single rhombohedral crystal structure without any secondary phases. The UV light driven photocatalytic activity was assessed for rhodamine B (RhB) degradation. As a result, ultrafast photodegradation activity was observed after Sr doping. Moreover, the 30 wt% Sr-Ca 3 (PO 4) 2 sample showed the highest photocatalytic degradation among the Sr-doped Ca 3 (PO 4) 2 samples toward RhB. It was further suggested that as-synthesized 30 wt% Sr-Ca 3 (PO 4) 2 superior photocatalytic performance is ascribed to the more proficient partition of photogenerated electron-hole pairs. Furthermore, the involved mechanism of superior photocatalytic performance of the 30 wt% Sr-Ca 3 (PO 4) 2 solid solution was also investigated. In addition, regeneration cycles indicated the higher stability of the photocatalyst to be effectively recycled up to four times without any considerable reduction in photocatalytic performance. Thus, these informations further provides us a scalable pathway to fabricate Sr doped Ca 3 (PO 4) 2 and its consequent use as an efficient photocatalyst for rhodamine B (RhB) contaminated wastewater treatment. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Sr and Nd isotopic compositions of a sample depend on its initial isotopic ratios, the ratios between the parent nuclide and daughter product, and the decay time. Due to their significance for the tracing of reservoirs, they were widely applied in the geological studies. Traditional cation resin was applied to purify Sr and Nd for isotope analysis, which involved the organic reagent and pH adjustment. The complex chemical procedure was time-consuming. In recent years, the appearance of special resins has made it easy to separate these elements. However, due to the influence of sulfates and other factors, the use of special resins is limited. OBJECTIVES: To shorten the chemical purification time of Sr and Nd, and to avoid the damage of sulfate ions on the Sr and REE specific resins, we proposed a new chemical purification method, where multiple columns were utilized. METHODS: The method combines cationic resin and special resin to realize the rapid separation of Sr and Nd and can extend the using time of special resin. The experiment uses cationic resin, Sr special resin and LN rare earth special resin to analyze the basalt standard BCR-2. RESULTS: The recoveries of Sr and Nd with this method are larger than 90%. The 87Sr/86Sr and 143Nd/144Nd isotope ratios were 0.705016±0.000016 (n=36, 1SD) and 0.512623±0.000008 (n=39, 1SD), respectively, which are in coincident with the values previously reported by TIMS method within the analytical error. The complied 87Sr/86Sr and 143Nd/144Nd isotope ratios obtained TIMS are 0.705000-0.705023 and 0.512630-0.512650, respectively. The 85Rb/86Sr and 147Sm/144Nd rations of the purified Sr and Nd solution are less than 0.01 and 0.001, respectively. CONCLUSIONS: The proposed chemical purification procedure can efficiently separate Rb, Sr, Sm and Nd, and realize the accurate analysis of Sr and Nd isotopes. [ABSTRACT FROM AUTHOR]

In the present work, Ba 1-x Sr x MnO 3 (x = 0.03, 0.07, and 0.10) fibers are synthesized by using the electrospinning–calcinations combinations process. The fabricated fibers were characterized by a combination of analytical technique such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive analysis of X-rays (EDAX), Fourier Transform Infrared (FT-IR), and Diffuse reflectance spectroscopy (DRS). XRD confirms hexagonal structure of Ba 1-x Sr x MnO 3 fibers. A classical size-strain plot (SSP) method has been applied to estimate the microstructure parameters of the produced fibers from the XRD peak broadening analysis. SEM images show the randomly oriented fibers along with diameter growth upon increasing the Sr content. DRS technique was used to estimate the optical band gap of the synthesized samples. The gas sensing study shows the sensing ability of Ba 1-x Sr x MnO 3 fibers, pressed into pellets, toward ethanol vapors. [ABSTRACT FROM AUTHOR]

Effective bone repair applications of titanium-based biometals must have excellent self-antibacterial properties and osteogenesis. Due to the special nano-geometric structure of titanium dioxide nanotubes (TN), the modified TN can confer various biological functions on the surface of titanium-based biometals. In this study, we used anodization, hydrothermal synthesis, and dopamine self-assembly to develop a Sm/Sr-doped TN (SSNT) array that integrated the antibacterial properties of Sm and the bone formation properties of Sr. AFM, SEM, FTIR, EDS, and XPS methods were used to characterize the SSTN, and the antibacterial and cell compatibility of the SSTN were systematically studied. Sm ions and Sr ions were slowly and stably released from the surface of dopamine and SrTiO 3 crystals, respectively. Compared with TN, SSTN had a smaller roughness and significantly improved hydrophilicity. The colony count, inhibition zone and turbidity experiments demonstrated that the SSTN structure containing Sm had obvious antibacterial effect on E. coli and S. aureus. The nanotube structure containing strontium ions can promote the early differentiation and osteogenic gene expression of MC3T3-E1 cells adhered to the SSTN surface. Based on the above results, the dual doping of Sm and Sr, and the ideal hydrophilicity can not only improve the osteogenesis of titanium-based biometals, but also make such bone implant biometals have effective self-infection resistance. [ABSTRACT FROM AUTHOR]

To study the radiolysis of the extractant composition based on solutions of dicyclohexano-18-crown-6 (DCH18C6) in ionic liquids containing the bis(trifluoromethylsulfonyl)imide anion (NTf2−), we synthesized stereoisomeric DCH18C6•Sr(NTf2)2 complexes as a model of the strontium-containing macrocyclic component of this system and studied the mechanism of their destruction in the solid phase. Three main stages of radiation-chemical transformations were found. At the initial stage of radiolysis after ionization of the complex components, a positive charge is transferred from the macrocycle to the anion, which is induced by the lower ionization potential of NTf2− as compared to the crown ether. This results in the radiation protection of the macrocycle due to the blockage of the polyether ring cleavage, which is observed under radiolysis of "free" DCH18C6. The next stage consists in the accumulation of the —O—•CH—CH2— radicals caused by the reaction of the dissociation products of the NTf2− anion with the crown ether. It intensifies the radiation destruction of the polyether ring. At the final stage, the macrocyclic radicals efficiently scavenge SO2, the molecular product of dissociation of the NTf2− anion, with the formation of sulfonyl-type radicals. The discovered channels of radiation-chemical transformations of the macrocycle in the systems including the NTf2− anion should be considered in the design of new radiation-resistant extractants. [ABSTRACT FROM AUTHOR]

Removal of 90Sr from aqueous media by sorbents prepared from bentonite from the Oglanlynski field and by their composites with magnetite is studied. It is shown that the sorbents can be used for purification of large volumes of radioactively contaminated waters. Here, we study bentonite rock material (a natural mineral), montmorillonite in Na-form derived from it, clinoptilolite and cristobalite (impurities in bentonite), and composites obtained by depositing magnetite onto the surface of listed materials. The 90Sr sorption is effective in a broad pH range (3.7–9). The developed composites can be successfully used in purification of radioactively contaminated aquatic environments. The magnetite in sorbents functions exclusively as a magnetically active component, which enables us to use an external magnetic field in separation of sludge resulting from water purification process. The maximum adsorption of strontium ions, as calculated from the Langmuir equation, is obtained for montmorillonite in Na-form and the initial rock material: 20.8 and 14.5 mg/g, respectively. For the composites based on these materials, the values are smaller: 18.5 and 10.6 mg/g, respectively. The effectiveness of sorbents for removal of 90Sr from natural waters and liquid radioactive wastes is shown to be determined mostly by the mineral content of media to be purified, i.e., the type and concentration of macro elements: Na+, K+, and Ca2+. Among the indicated competing ions, calcium affects the removal of strontium from aquatic environments to the largest extent. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of Sr2+ and Ba2+ into liquid Bi was investigated in dilute concentrations of Srcl2/Bacl2 (05 mol%) in LiCl-KCl electrolytes at 500 °C to ascertain the limit of liquid Bi electrodes for alkaline-earth recovery. Analysis of the electrodes after constant current electrolysis to the specific charge of 270 C g-1 showed Sr2+ ions consuming 29% of charge at 5 mol% before dropping to 8%10% of the total charge at 0.450.72 mol% Srcl2. Ba2+ ions consumed 54% at 5 mol% Bacl2 before decreasing to 22%24% at 0.420.89 mol% Bacl2; substantial co-deposition of Li was observed in all chemistries, consuming up to 53% of charge. Considering only 1% of the total charge was consumed for depositing Ba2+ and Sr2+ ions in 0.1 mol% Srcl2/Bacl2 electrolyte, the lower recovery limit of Bi for alkaline-earth elements is suggested to be at 0.4 mol% Srcl2/Bacl2 to achieve appreciable deposition of alkaline-earths (>1.5 mol% Ba/Sr in liquid Bi). The overpotentials of liquid Bi at 5 mol% of Srcl2/Bacl2 were evaluated by electrochemical impedance spectroscopy. The co-deposition of Sr and Li exhibited the largest increase in charge transfer resistances implying sluggish charge transfer kinetics whereas the co-deposition of Ba and Li exhibited a large increase in mass transport resistances due to the slow diffusion of Ba2+ ions in the electrolyte. [ABSTRACT FROM AUTHOR]

Identifying the geographic origins of Chinese mitten crabs is important for food safety and fair market competition. In this study, we used strontium (Sr) isotopes as a tool to trace the geographic origins of Chinese mitten crabs. Chinese mitten crabs, water, and different types of crab feed were collected from four different lakes for Sr isotope analyses. The results showed that the Sr isotope compositions of the different parts from one single crab were consistent within error, indicating that any piece of a crab could be used to represent the Sr isotope characteristics of the whole crab. The Sr isotope compositions of Chinese mitten crabs from the same lake were consistent within the analytical error, and the values were similar to the Sr isotope composition of the water from the same lake. However, the Sr isotope compositions of water and crabs from different lakes are significantly different. Therefore, the Sr isotope compositions of Chinese mitten crabs are mainly controlled by lake water composition, while the impact of feed is limited. This study provides an effective method for tracing the geographic origins of Chinese mitten crabs. [ABSTRACT FROM AUTHOR]

We examined the cation selectivity of the Saalfrank-type {2}-metallocryptands [Ga2R3 and [Fe2R3 (R: 1,1'-(pyridine-2,6-diyl)bis(2-(1H-tetrazol-5-yl)ethan-1-one)) with alkaline and earth alkaline metal ions by means of DFT calculations (B3LYP/LANL2DZp) to obtain a better insight into the influence of the bridge head metal ions responsible for the cryptands ion selectivity. Based on our DFT calculations, notably the application of model equations and geometric features regarding the flexibility of the {2}-metallocryptands, we identified K+, Sr2+ and Ba2+ as the best fitting ions. While [Fe2R3 has a cavity a bit larger than [Ga2R3, it prefers the Ba2+ cation, whereas [Ga2R3 selects the smaller Sr2+ cation. The good flexibility of the investigated hosts is provided by the oxygen-donor moieties of the {2}-metallocryptands. [ABSTRACT FROM AUTHOR]

The effect of silver (Ag) and strontium (Sr) ions implanted into polycrystalline (SiC) was investigated. One batch of polycrystalline SiC wafers was implanted with 360 keV silver ions (Ag-SiC) and another implanted with 360 keV strontium ions (Sr-SiC). Both implantations were performed at 600 °C to a fluence of 2 × 1016 cm−2. Some of the Ag- SiC samples were then implanted with Sr ions of 280 keV to a fluence of 2 × 1016 cm−2 at 600 °C (Ag&Sr-SiC). The as-implanted samples were annealed at temperatures from 1000 to 1400 °C in steps of 100 °C for 5 h. The samples were thereafter characterised by Transmission electron microscopy (TEM), Raman spectroscopy, Elastic Recoil Detection Analysis (ERDA), Rutherford backscattering spectrometry (RBS), and Scanning electron microscopy (SEM). Both individual and dual implantations resulted in no amorphization of the SiC. As expected, dual implantation resulted in a higher defect concentration. Subsequent Sr implantation resulted in the formation of Ag precipitates, especially around grain boundaries. Annealing the Ag-SiC and Ag&Sr-SiC samples caused the shift of implants towards the surface accompanied by loss at 1400 °C while no loss was observed in the Sr-SiC samples. [ABSTRACT FROM AUTHOR]

Ferrocyanides with general formula AIxBIIy[Fe(CN)6], where A and B are cations, are thought to accept many substitutions on the A and B positions. In this communication, the synthesis and crystal structure of Cs²Sr[Fe(CN)6] are reported. The latter was obtained from K2Ba[Fe(CN)6] particles, put in contact with caesium and strontium ions. Hence, a simultaneous ion-exchange mechanism (Cs for K, Sr for Ba) occurs to yield Cs2Sr[Fe(CN)6]. The synthesis protocol shows that K2BaFe(CN)6 particles can be used for the simultaneous trapping of radioactive caesium and strontium nuclides in water streams. Cs2Sr[Fe(CN)6] adopts the cryolite structure type and is isotypic with the known compound Cs2Na[Mn(CN)6] [dicaesium sodium hexa­cyanidomanganate(III)]. The octa­hedrally coordinated Sr and Fe sites both are located on inversion centres, and the eightfold-coordinated Cs site on a general position. [ABSTRACT FROM AUTHOR]

We examined the cation selectivity of the Saalfrank-type {2}-metallocryptands [Ga2R3 and [Fe2R3 (R: 1,1'-(pyridine-2,6-diyl)bis(2-(1H-tetrazol-5-yl)ethan-1-one)) with alkaline and earth alkaline metal ions by means of DFT calculations (B3LYP/LANL2DZp) to obtain a better insight into the influence of the bridge head metal ions responsible for the cryptands ion selectivity. Based on our DFT calculations, notably the application of model equations and geometric features regarding the flexibility of the {2}-metallocryptands, we identified K+, Sr2+ and Ba2+ as the best fitting ions. While [Fe2R3 has a cavity a bit larger than [Ga2R3, it prefers the Ba2+ cation, whereas [Ga2R3 selects the smaller Sr2+ cation. The good flexibility of the investigated hosts is provided by the oxygen-donor moieties of the {2}-metallocryptands. [ABSTRACT FROM AUTHOR]

The evolution of intermediate circulation in the northern Indian Ocean since the last deglaciation has been reconstructed from two marine cores located at intermediate depths off the southern tip of India (MD77‐191) and in the northern Bay of Bengal (BoB) (MD77‐176). Benthic foraminiferal δ13C, seawater carbonate ion concentration ([CO32−]) estimated from the Sr/Ca, and paleotemperature reconstructed on the basis of the Mg/Li of aragonite benthic species Hoeglundina elegans were used to trace the evolution of past intermediate‐deepwater masses and to constrain ocean‐atmosphere exchanges during the two‐stage increase in atmospheric CO2 across the last deglaciation. The intermediate water [CO32−] was mainly affected by changes in the ocean alkalinity inventory, associated with the modulation of atmospheric CO2 on glacial‐interglacial timescales. Higher benthic foraminiferal δ13C, depleted [CO32−], and decreased benthic‐planktonic 14C age offsets at intermediate water depths suggest a release of deep‐sea CO2 to the atmosphere through the Antarctic Intermediate Water (AAIW) in the Southern Ocean during the 17–15.2 and 12.6–10.5 cal kyr BP time intervals. In addition, the decreased H. elegans Mg/Li record seems to reflect an increased contribution of cold water mass during the 17–15.2 and 12.6–11.9 cal kyr BP intervals and throughout the Holocene. In contrast, two warm events occurred in the 15–13.3 and 11–10.3 cal kyr BP time intervals. During the late Holocene, a decrease in the intermediate water [CO32−] indicates a contribution to atmospheric CO2 rise since 8 cal kyr BP, due to the depleted global ocean alkalinity and/or the variations in surface productivity (at least for MD77‐191). Key Points: We produced high‐resolution records of benthic foraminiferal elemental ratios, δ18O, and δ13C from two cores from the northern Indian OceanEvaluation of past IWT from the Mg/Li ratio and the δ18O since last deglaciation exhibit millennial‐scale changesVariations of the IW Δ[CO32−] calculated from H. elegans Sr/Ca are related to atmospheric CO2 changes on glacial‐interglacial timescales [ABSTRACT FROM AUTHOR]

We analysed the isotopic compositions of bioavailable strontium (Sr) and lead (Pb) in 47 samples of animals and plants derived from the various geological substrates of southwestern South Africa, to explore the utility of these isotope systems as dietary tracers. Measurements were made using high-resolution multi-collector inductively-coupled-plasma mass spectrometry (MC-ICP-MS). B7Sr/8&Sr could efficiently discriminate between geologically recent sediments of marine origin in near-coastal environments and older geologies further inland. However, 87Sr/B6Sr was not able to distinguish between the Cape Granite Suite and the Cape System (Table Mountain sandstones), whereas Pb isotopes could, demonstrating the utility of this hitherto underused isotope system. Bioavailable 87Sr/86Sr in near-coastal terrestrial environments is influenced by marine input whereas Pb isotopic ratios are not, because of low concentrations of Pb in seawater. There is considerable potential to use Pb isotopes as a dietary and palaeodietary tracer in near-coastal systems in fields as diverse as archaeology, palaeontology, wildlife ecology and forensics. [ABSTRACT FROM AUTHOR]

Strontium-doped neodymium orthoferrites belong to the perovskite type of materials of a wide range of interests and applications. This material has an orthorhombic perovskite crystal system of space group (Pbnm) no. 62. Nd0.6Sr0.4FeO3 is synthesized using the co-precipitation method, and the resulting precipitated powder was fired at different temperatures to control the nano-crystalline size. The effect of the nano-crystalline size on the structure and the electrical properties were studied. The EDS spectra confirmed that the compound was formed according to the suggested calculations. SEM micrographs showed the homogeneity of the nano grain size in the compound. The nano-crystalline size of the prepared samples, fired at 705 °C and at 850 °C were 40 nm and 90 nm, respectively. Nd0.6Sr0.4FeO3 showed a semiconducting behavior according to the exponential dependence of resistivity on temperature in the range from 350 K up to 473 K. The temperature independence of impedance is found at high frequencies starting from 0.5 MHz. The frequency dependence–activation energy is found in the temperature range from 350 K up to 473 K. The found decrease in AC resistivity with frequency increase for Nd0.6Sr0.4FeO3 showed that the hopping mechanism occurred in the charge carrier transfer. [ABSTRACT FROM AUTHOR]

The effects of Co-Ti ions substituting Fe3+ ions in strontium hexaferrite nanoparticles synthesized using ball-milling technique were investigated. X-ray diffraction patterns of SrFe12-2xCoxTixO19 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) demonstrated standard SrFe12O19 patterns with space group P63/mmc. The phase purity and the valence state of each ion were examined using X-ray photoelectron spectroscopy. The results indicated a Ti4+ valence state and a coexistence of 2 + and 3 + valence states for Fe and Co. An obvious irreversibility between the zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves was observed below 300 K. The broad peaks in the ZFC curves were attributed to the movement of magnetic domains at temperature (TM). Magnetization hysteresis loops at discrete temperatures between 4 and 300 K showed a ferromagnetic behavior, with high coercive fields and large saturation magnetizations. The change of the saturation magnetization with increasing x revealed spin reorientation behavior at x ≥ 0.4 and remained relatively high for practical applications. The first anisotropy constant decreased with the increase of temperature. With Co-Ti substitution, it remained almost constant up to x = 0.4, and then decreased almost linearly at higher Co-Ti concentrations. Furthermore, the coercive field decreased with increasing x, reaching values suitable for high-density magnetic recording at 300 K in the substitution range 0.4 ≤ x ≤ 0.8. [ABSTRACT FROM AUTHOR]

Treatment of fission product aqueous waste is a challenging problem as their chemical concentrations are too low but have significant radiation hazard due to their half-life. The current methods of co-precipitation lead to more sludge and require more space for confinement. Size enhanced ultrafiltration (SEUF) is an emerging technology with a potential not only to effectively separate the species of interest namely Strontium [Sr(II)] and Cesium [Cs(I)] but also recover them by reversing certain chemical conditions. The present paper concerns the removal of Sr(II) and Cs(I) from aqueous streams using SEUF. The studies were conducted using chitosan derivative, carboxymethyl chitosan (CMCh) as a size enhancing agent. The effect of process variables such as initial pH, loading ratio (P/M), and initial concentration of Sr(II) and Cs(I) on the percentage rejection and binding capacity have been studied. The design of experiments was performed by response surface methodology (RSM). The maximum percentage rejection of Cs(I) was found to be 99% at the following optimum process conditions: initial pH of the feed solution is 12, initial concentration of Cs(I) is 10 mg/L, and P/M value is 0.5. The maximum percentage rejection of Sr(II) was found to be 99% at the following optimum process conditions: initial pH of the feed solution is 12, initial concentration of Sr(II) is 9 mg/L, and P/M value is 0.5. The results show that SEUF with CMCh could be an effective method for the removal of Sr(II) and Cs(I). [ABSTRACT FROM AUTHOR]

New coordination polymers with 2D network structures with fluorine directly coordinated to the metal ion were prepared both via mechanochemical synthesis and fluorolytic sol–gel synthesis. Depending on the synthesis route, the samples show different particle sizes, according to SEM imaging. The crystal structures of barium acetate fluoride, strontium acetate fluoride, and lead acetate fluoride (BaF(CH3COO), SrF(CH3COO) and PbF(CH3COO)) were solved from X-ray powder diffraction data. The structure solution is backed by the results from 19 F MAS NMR, FT IR data, and thermal analysis. The calculated chemical shifts of the 19 F MAS NMR spectra coincide well with the measured ones. It turns out that the grinding conditions have a remarkable influence on the mechanochemical synthesis and its products. Our systematic study also indicates a strong influence of the atomic radii of Ca, Sr, Ba, and Pb on the success of the syntheses. [ABSTRACT FROM AUTHOR]

A strontium‐doped lanthanum cobaltite perovskite, La0.6Sr0.4CoO3, was prepared and utilized as a recyclable heterogeneous catalyst for the direct oxidative C(sp3)─H/C(sp2)─H coupling reaction between cyclic ethers and alkenes or coumarins to achieve corresponding α‐functionalized ethers. The α‐functionalization of cyclic thioethers or amides with alkenes or coumarins was also achieved via this protocol. The La0.6Sr0.4CoO3 catalyst exhibited better performance than a variety of homogeneous and heterogeneous catalysts. Utilizing a recyclable catalyst would offer a greener option for the direct oxidative C(sp3)─H/C(sp2)─H coupling reaction. To our best knowledge, the C(sp3)─H/C(sp2)─H coupling between olefins and ethers to generate α‐functionalized ethers using a heterogeneous catalyst has not been previously reported, and the α‐functionalization of cyclic thioethers or amides with alkenes or coumarins is new. [ABSTRACT FROM AUTHOR]

Substitution of alkali earth metal ion of Sr2+, in the Pb2+ site of Pb(Mg 1/3 Nb 2/3)O 3 –PbTiO 3 is expected to induce functional modulations in the system. Doping of 4 at.% of Sr2+ in 0.68PMN-0.32PT was carried out to lower the transition temperature, and to investigate the intended ferroelectric and dielectric variations. Excellent relaxor property was observed in the doped sample without appreciable reduction in remnant polarization. Doping with Sr2+ led to a reduction in transition temperature from 165 °C to 117 °C. Doped sample exhibited remnant polarization P r = 16.2 μC/cm2, Squareness factor (Rsq) = 1.05 and Relaxor exponent (γ) around 2. Modulation in the functional response was exhibited by the doped composition, having low transition temperature, and its prospect in electrocaloric applications was analyzed. Image 1 [ABSTRACT FROM AUTHOR]

BACKGROUND Microbial biosorption is recognized as a resourceful process for the remediation of pollution from contaminated environs. To investigate radionuclide bioremediation, carbohydrate contained extracellular polymeric substance (EPS) and strontium ion (Sr+) tolerant marine actinobacterium has been isolated and identified as Streptomyces sp. CuOff24 through 16S rDNA sequencing. RESULTS: EPS was extracted, characterized and the biosorption of the long half‐life radionuclide of Sr2+ was also performed. EPS could remove 82% of Sr2+ from the experimental solution of 100 mg L−1 of strontium chloride (SrCl2). Furthermore, EPS composition also obtained with the presence of Sr2+ radionuclide and major contents of carbohydrate (68.6%) followed by protein (12.3%), nucleic acid (10.4%) and unidentified compounds 8.7%) were quantified. The spectroscopy study also confirmed the presence of carbohydrate functional groups presence in the EPS surface were probably to be involved in Sr2+ adsorption. CONCLUSION: Overall results conclude that, marine actinobacterial EPS could be used for the large‐scale remediation of radionuclides contaminated environment. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

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• A novel impregnated zeolite was synthesized and characterized. • Sr2+ and Cs+ elimination efficacy using NAASMS-Z was assessed and optimized. • Empirical models were derived to correlate elimination with time and temperature. • Mechanism of Sr2+ and Cs+ elimination was investigated through modeling evaluation. • ANFIS model predicted the sorption amount according to the input variables. In this research, a novel impregnated nano-zeolite (NAASMS-Z) was synthesized and characterized using different characterization techniques. Excellent properties, such as high specific surface area (~502.77 m2/g), low pore size (~8.92 Å) and the existence of numerous functional groups caused the efficient elimination of Sr2+ and Cs+ cations from aquatic systems. The sorption performance of the nano-particles was enhanced by impregnation up to 60% in the aquatic media. The kinetic study indicated that the elimination process of both the concerned cations is controlled by external film mass transfer through the boundary within the first 30 min then controlled by intra-particle diffusion. The sorption equilibrium data suggested that the sorption process occurs on the heterogeneous sorbent surface. Parameters affecting the elimination of Sr2+ and Cs+ from a single metal sorption system, such as pH, initial contaminant concentration (C i) and contact time (t), were investigated and optimized. A predictive model based on an Adaptive Neuro-Fuzzy Inference system (ANFIS) analysis was applied to evaluate the experimental parameters affecting the elimination of Sr2+ and Cs+ cations from aquatic system. A Mamdani-type FIS was employed to justify a collection of 16 rules (If-Then format) by means of centroid membership functions. The suggested fuzzy model revealed high predictive concert with high correlation coefficient (R2) and satisfactory deviation from the experimental data, affirming its appropriateness to predict Sr2+ and Cs+ elimination efficacy from the studied system. Rooted in experimental data and statistical analysis, the synthetized material was effective for treating contaminated aquatic solutions containing Sr2+ and Cs+ cations. [ABSTRACT FROM AUTHOR]