Incorporation Of Sr Research Articles

Comprehensive assessment of SrO and CuO co-incorporated 50S6P amorphous silicate bioactive glasses in vitro: Revealing bioactivity properties of bone graft biomaterial for bone tissue engineering applications

Bioactivity is critically important for a glass material to be used in bone tissue engineering, which is stated to be affected by the addition of therapeutic ions such as Sr and Cu. In this study, the findings of a comprehensive in vitro study on the bioactivity of previously produced and characterized in terms of structure, composition and thermal features novel SrO and CuO co-incorporated 50S6P (SiO2–CaO–Na2O–P2O5, SrO–CuO) glasses were discussed. Herein, chemical bond, morphology, composition, and crystallinity changes on the amorphous silicate glasses were investigated using FT-IR, SEM-EDX, and XRD analysis, respectively. Furthermore, quantitative assessment of glass ionic dissolution products concentrations were performed in contact with simulated body fluid by ICP-OES analysis. SrO and CuO co-incorporated 50S6P amorphous silicate glasses showed an appropriate release profile in terms of its ionic products (Si4+: 18.5–32.6, Ca2+: 132.1–234.3, Sr2+: 1.29–2.35, Cu2+: 2.28–3.34, ppm), which resulted in the formation of Ca–P layer and the proceeding of its accumulation, further conformed with FT-IR and SEM-EDX. Furthermore, apatite layer, which consists of crystal apatite ranging in size (6.5–9.8 nm) having different degree of crystallinity percentages (2.5–22.4%), was formed on the glasses surface within 28 days in SBF. The results revealed that Sr incorporation (4.22 wt %) has an enhancing effect on bioactivity, whereas increased Cu incorporation (0.10–0.26 wt %) had a relatively inhibitory effect on bioactivity of the glasses. These findings are indicators of desirable bioactive features of 50S6P glasses. Thus, these bioactive glasses are acceptable to be utilized in bone tissue engineering application as bone graft biomaterials.

Assessing the impact of different carbonate system parameters on benthic foraminifera from controlled growth experiments

Insights into past marine carbon cycling and water mass properties can be obtained by means of geochemical proxies calibrated through controlled laboratory experiments with accurate seawater carbonate system (C-system) manipulations. Here, we explored the use of strontium/calcium ratio (Sr/Ca) of the calcite shells of benthic foraminifera as a potential seawater C-system proxy through a controlled growth experiment with two deep-sea species (Bulimina marginata and Cassidulina laevigata) and one intertidal species (Ammonia T6). To this aim, we used two experimental set-ups to decouple as much as possible the individual components of the carbonate system, i.e., changing pH at constant dissolved inorganic carbon (DIC) and changing DIC at constant pH. Four climatic chambers were used with different controlled concentrations of atmospheric pCO2 (180 ppm, 410 ppm, 1000 ppm, 1500 ppm). Our results demonstrated that pH did not influence the survival and growth of the three species. However, low DIC conditions (879 μmol kg−1) negatively affected B. marginata and C. laevigata through reduced growth, whereas no effect was observed for Ammonia T6. Our results also showed that Sr/Ca was positively correlated with total Alkalinity (TA), DIC and bicarbonate ion concentration ([HCO3−]) for Ammonia T6 and B. marginata; i.e., DIC and/or [HCO3−] were the main controlling factors. For these two species, the regression models were coherent with published data (existing so far only for Ammonia T6) and showed overall similar slopes but different intercepts, implying species-specific effects. Furthermore, the Sr/Ca - C-system relationship was not impacted by ontogenetic trends between chamber stages, which is a considerable advantage for paleo-applications. This applied particularly to Ammonia T6 that calcified many chambers compared to the two other species. However, no correlation with any of the C-system parameters was observed for Sr/Ca in C. laevigata. This might imply either a strong species-specific effect and/or a low tolerance to laboratory conditions leading to a physiological stress, thereby impacting the Sr incorporation into the calcite lattice of C. laevigata.

X-ray detectors based on CsPb1-xSrxBr3 thick films

The CsPbX3 perovskites have demonstrated promising applications in the field of X-ray detection. Appropriate element doping to substitute Pb in CsPbX3 not only improves the photoresponse performance of the resulting material but also reduces the Pb content for achieving environmental protection. Herein, X-ray detectors based on Sr-doped CsPb1-xSrxBr3 thick films were developed. The effects of Sr doping concentration were investigated. The incorporation of Sr increased the density of the CsPbBr3 thick film and modulated the bandgap of the materials. CsPb1-xSrxBr3 exhibited good optical responses at different bias voltages and X-ray doses. The X-ray response improved as the Sr-doping concentration increased. Therefore, the partial substitution of Sr into CsPbBr3 is suitable for reducing the Pb content in X-ray detectors. Furthermore, the development of CsPb1-xSrxBr3 thick films provides a new strategy for the detection of X-rays.

Effects of the Sr/Ca ratio on the bioremediation of strontium based on microbially-induced carbonate precipitation

90Sr is a radionuclide that poses a potential threat to ecosystem security, and Sr bioremediation based on microbially-induced carbonate precipitation (MICP) usually affected by Ca. Experiments of carbonate mineralization induced by Enterobacter sp. JC-1 in solution with different Sr/Ca molar ratios were performed to explore the effect of Sr/Ca ratio on microbially-induced carbonate precipitation. X-ray diffraction patterns indicated that strain JC-1 induced the formation of calcite (Sr/Ca < 1) and strontianite (Sr/Ca = 1), and the increase in the d(104) and d(012) of calcite indicated that Sr entered the calcite lattice. The normalized distribution coefficient of Sr (DSr) in the minerals indicated that a higher Sr/Ca ratio promoted Sr incorporation into minerals. Sr2+ removal showed a V-shape (initial decrease and subsequent increase) with an increase in Sr/Ca ratio, which had no correlation with the DSr, but was positively correlated with the mass of CO32- (r = 0.779, p < 0.01) in the mineral. However, mineralization experiments induced by chemicals showed that Sr2+ removal was positively correlated with DSr (r = 0.785, p < 0.01), which suggested that MICP was not simple chemical process. The moles of carbonate in minerals revealed that a higher Sr/Ca ratio influenced the ability of bacteria to generate carbonate. The Sr2+ removal was due to the combined effect of microbial growth and the DSr. In conclusion, this study revealed the relationship of Sr/Ca ratios between the solution and minerals, which has reference value for the explanation of the formation mechanism of carbonate mineral and Sr bioremediation.

Evaluation of novel composition (SiO2–CaO–Na2O–P2O5, SrO–CuO) degradable amorphous silicate glasses properties and comprehensive characterization of the thermal features

The current work presents and discusses the findings of a comprehensive study on the structural, chemical and thermal properties of SrO and CuO incorporated SiO2–CaO–Na2O–P2O5 amorphous silicate glass with a novel composition. Here, fundamental features (experimental density, oxygen density, and hardness) of all glasses were determined and chemical as well as phase composition of the glasses was verified with XRF and XRD, respectively. Moreover, the thermal behavior (viscos flow and crystallization kinetics) of amorphous silicate glass was investigated by non-isothermal methods using DTA analysis. The activation energies of glass transition (Eg) were calculated in the range of 546–1115 kJ/mol by Kissinger method, whereas the activation energies of crystallization (Ec) were calculated in the range of 164–270 kJ/mol by three different methods (Kissinger, Ozawa, Yinnon and Uhlmann). Avrami exponent (n) values ranged from 1.17 to 3.28 demonstrated that amorphous silicate glasses have different crystallization mechanism. Working temperature, which is one of the parameters indicating glass stability, increased with the incorporation of Sr and Cu from 187 °C to 245 °C. The initial dissolution measurement has been applied to study the degradability behavior of Sr and Cu incorporated amorphous glasses in vitro. Quantitative evaluation of Si4+ (0.156–0.373 kV), Ca2+ (0.043–0.332 kV), Na+ (0.044–0.329 kV), P5+ (0.057–0.289 kV), Sr2+ (0.134–0.385 kV), and Cu2+ (0.090–0.203 kV) depending on the ion activation energy (Ea-ion) and ion concentration at different temperature values (24, 37 and 55 °C) was performed in contact with Tris-HCl solution by ICP-OES analysis. The results revealed that investigated glasses were degradable and incorporation of Sr and Cu affected the glass initial dissolution. Overall, investigated glasses are suitable for various application such as hot-working production, glass-ceramic manufacturing, and glass or glass-ceramic scaffolds fabrication, due to wide working temperature ranges and high crystallization tendencies of the developed glasses.

Non-equilibrium BaxSr1-xSO4 solid solution compositions at elevated Sr2+ concentration, ionic strength, and temperature

The BaxSr1-xSO4 solid solution is ubiquitously present in both geological and industrial processes, where they mostly form under non-equilibrium conditions. Compared with those formed under equilibrium conditions, the BaxSr1-xSO4 solid solution formed at non-equilibrium condition has significantly higher Sr incorporation at the same aqueous phase compositions. The solid composition of BaxSr1-xSO4 formed at non-equilibrium condition is critical for the study of chemical palaeoceanography as well as the solid solution nucleation and growth kinetics. However, few studies have been conducted to investigate the composition of the BaxSr1-xSO4 solid solution when it precipitates at non-equilibrium conditions. In this study, the distribution coefficient of Ba2+ and Sr2+ between the BaxSr1-xSO4 solid solution and the aqueous phases (KD,Sr-Barite) at non-equilibrium conditions was studied with barite saturation index (SIbarite) from 0.9 to 1.5, [Sr2+]/[Ba2+] molality ratio from 0.33 to 30, temperature (T) from 50 to 90 °C and ionic strength (IS) from 0.01 M to 3 M as NaCl, with celestite being undersaturated. The composition of the BaxSr1-xSO4 solid solution formed at non-equilibrium conditions can then be calculated from the KD,Sr-Barite values. The results show that the KD,Sr-Barite value decreases with the increase of aqueous Sr2+ concentration at fixed SIbarite and T conditions. The IS effect on the KD,Sr-Barite value is small. Based on the experimental results, a new empirical model is developed to accurately predict the measured compositions of BaxSr1-xSO4 solid solution at non-equilibrium conditions under a wide T and IS conditions as follows (the plot of the predicted log10KD,Sr-Barite versus the measured log10KD,Sr-Barite with R2=0.9995):KD,Sr-Barite=-1.21-1.84SIbarite+1928.1SIbarite×T+aSr2+,aqaBa2+,aq-1Several theoretical models have also been compared against the experimental data. The birth and spread crystal growth model (B + S model) could accurately predict the solid composition of BaxSr1-xSO4 at higher barite SI and/or higher T conditions (barite SI = 1.5 at 70 °C and barite SI = 1.2–1.5 at 90 °C with [Sr2+]/[Ba2+] = 0.33–10). However, the B + S model predictions show larger deviations at lower SI and/or lower T conditions (barite SI = 0.9 and 1.2 at 50 °C and barite SI = 0.9 at 70 °C with [Sr2+]/[Ba2+] = 0.33–10 in this study). For other theoretical models, such as the CNT model and the BCF model, the predicted solid compositions of BaxSr1-xSO4 are significantly higher than the measured results. This quantitative study of the BaxSr1-xSO4 solid solution compositions could help reconstruct oceanic physical conditions and chemistry. It also establishes a solid foundation to further investigate the kinetics of the BaxSr1-xSO4 solid solution formation during non-equilibrium geological and industrial processes.

Sr-doped BaZr0.5Fe0.5O3-δ cathode with improved chemical stability and higher performance for proton-conducting solid oxide fuel cells

A new Ba0.5Sr0.5Zr0.5Fe0.5O3-δ (BSZF) material was proposed as a cathode for proton-conducting solid oxide fuel cells (H–SOFCs). Compared with the traditional Fe-doped BaZrO3 (BZF) cathode, the incorporation of Sr into the lattice decreased the lattice volume of the material but enhanced the chemical stability against CO2 that has been confirmed by both experiments and first-principles calculations. In addition, doping Sr allowed larger oxygen vacancy content and enhanced interaction with O2, facilitating the oxygen reduction reaction. The fuel cell with the BSZF showed an encouraging performance of 1048 mW cm−2 at 700 °C, much larger than that of the traditional BZF cell. The analysis for cell resistances revealed that the Sr-doping strategy reduced the cell polarization resistance, and the reduction was more profound under the loading condition, providing an interesting strategy for designing H–SOFC cathodes.

Strontium-incorporated bioceramic scaffolds for enhanced osteoporosis bone regeneration

The restoration of bone defects caused by osteoporosis remains a challenge for surgeons. Strontium ranelate has been applied in preventative treatment approaches due to the biological functions of the trace element strontium (Sr). In this study, we aimed to fabricate bioactive scaffolds through Sr incorporation based on our previously developed modified amino-functional mesoporous bioactive glass (MBG) and to systematically investigate the bioactivity of the resulting scaffold in vitro and in vivo in an osteoporotic rat model. The results suggested that Sr-incorporated amino-functional MBG scaffolds possessed favorable biocompatibility. Moreover, with the incorporation of Sr, osteogenic and angiogenic capacities were upregulated in vitro. The in vivo results showed that the Sr-incorporated amino-functional MBG scaffolds achieved better bone regeneration and vessel formation. Furthermore, bioinformatics analysis indicated that the Sr-incorporated amino-functional MBG scaffolds could reduce reactive oxygen species levels in bone marrow mesenchymal stem cells in the osteoporotic model by activating the cAMP/PKA signaling pathway, thus playing an anti-osteoporosis role while promoting osteogenesis. This study demonstrated the feasibility of incorporating trace elements into scaffolds and provided new insights into biomaterial design for facilitating bone regeneration in the treatment of osteoporosis.

Tuning the Band Gap in the Halide Perovskite CsPbBr3 through Sr Substitution.

The ability to continuously tune the band gap of a semiconductor allows its optical properties to be precisely tailored for specific applications. We demonstrate that the band gap of the halide perovskite CsPbBr3 can be continuously widened through homovalent substitution of Sr2+ for Pb2+ using solid-state synthesis, creating a material with the formula CsPb1-xSrxBr3 (0 ≤ x ≤ 1). Sr2+ and Pb2+ form a solid solution in CsPb1-xSrxBr3. Pure CsPbBr3 has a band gap of 2.29(2) eV, which increases to 2.64(3) eV for CsPb0.25Sr0.75Br3. The increase in band gap is clearly visible in the color change of the materials and is also confirmed by a shift in the photoluminescence. Density-functional theory calculations support the hypothesis that Sr incorporation widens the band gap without introducing mid-gap defect states. These results demonstrate that homovalent B-site alloying can be a viable method to tune the band gap of simple halide perovskites for absorptive and emissive applications such as color-tunable light-emitting diodes, tandem solar cells, and photodetectors.

Doping Sr and Introducing Oxygen Vacancies in Ba0.7Sr0.3TiO3‐X Synergistically Promote the Pyro‐Photo‐Electric Catalysis Performance

AbstractThe low utilization of light and the severe recombination of charge carriers have always restricted the development of photoelectric catalysis. In this work, the photoelectric catalytic performance is tuned by doping Sr in BaTiO3 pyroelectric material and simultaneously introducing oxygen vacancies to form double‐type defects, combined with pyroelectric polarization. Under the light and 20–50 °C cold‐heat cycle, the current density of Ba0.7Sr0.3TiO3‐X reaches the maximum of 0.92 mA ⋅ cm−2, which is higher than the current density of Ba0.7Sr0.3TiO3‐X under only light (0.69 mA ⋅ cm−2). Under light alone, the current density of Ba0.7Sr0.3TiO3‐X is higher than that of BaTiO3 (0.19 mA ⋅ cm−2) and Ba0.7Sr0.3TiO3 (0.44 mA ⋅ cm−2). This is because the incorporation of Sr can introduce the Fermi level, improve the utilization rate of solar energy, and improve the pyroelectric polarization effect with volume shrinkage, and promote the separation and transfer of carriers. Oxygen vacancies can be used as reactive centers for excited electrons to suppress the recombination of excited electron‐hole pairs. Furthermore, the generation of photogenerated and pyrogenerated carriers increases the overall carrier concentration. This provides ideas for the modification of traditional photoelectrodes for photoelectric catalysis water splitting.

Antimicrobial properties of co-doped tricalcium phosphates Ca3-2x(MˊMˊˊ)x(PO4)2 (M = Zn2+, Cu2+, Mn2+ and Sr2+)

The substituted (Ca2+/Cu2+), and co-substituted (Cu2+/Zn2+), (Cu2+/Sr2+), and (Sr2+/Mn2+) β-tricalcium phosphate (β-TCP)-based Ca3-2x(MˊMˊˊ)x(PO4)2 (M = Zn2+, Cu2+, Mn2+ and Sr2+) solid solutions have been synthesized using solid-state route. The powder X-ray diffraction study shows the formation of β-TCP-type structure as the main phase in all solid solutions. The crystal structures and chemical compositions were approved using Fourier-transform infrared (FT-IR) absorption spectra and energy-dispersive X-ray spectrometry (EDX) data, respectively. The unit cell parameters and volume of as-synthesized samples directly depend on the radius of the incorporated ions. The limits of the single-phase solid solutions were found based on the possible occupation of the crystal sites in β-TCP structure. For the divalent ions with small radii, such as Cu2+ or Zn2+, the limit composition was found as Ca2.571Mˊ0.429–xMˊˊx(PO4)2 for Mˊ and Mˊˊ – Cu2+ and Zn2+. The enlargement of the unit cell by incorporation of Sr2+ allows to extend the limit of solid solutions up to Ca2.5Sr0.5–xMˊx(PO4)2 for Mˊ – Cu2+ or Mn2+. The antibacterial properties were studied on 4 bacteria (S. aureus, P. aeruginosa, E. coli and E. faecalis) and 1 fungus (C. albicans). It has been showed that co-doped Ca2.5Sr0.25Cu0.25(PO4)2 sample exhibits the highest antimicrobial activity resulting in 92%, 96% and 96% inhibition growth rate for S. aureus, P. aeruginosa and E. faecalis, respectively. The antimicrobial properties are strongly related to the occupation of the crystal sites in the β-TCP structure by doping ions.

Tailored electrostrain and related properties in (1 − x)BaTiO3–xSrSnO3 Pb‐free electroceramics

AbstractWe report excellent electrostrain properties of (1 − x)BaTiO3–xSrSnO3 (BSTS) Pb‐free electroceramics (0 ≤ x ≤ 0.15), as well as the corresponding structural, dielectric, and ferroelectric properties. A tailored phase diagram of the pseudo‐binary solid solution of BaTiO3–SrSnO3, which exhibits a nearly composition‐independent orthorhombic–tetragonal polymorphic phase boundary close to room temperature, was obtained, and, in contrast to Ba(Ti1−xSnx)O3, the appearance of the relaxor mode was accelerated in the phase transition of BSTS owing to the additional incorporation of Sr. Using these compositionally modified phase‐related characteristics, desirable sets of electrostrain properties for actuator applications were obtained. Based on these results, we propose that BSTS is a promising candidate for Pb‐free electroceramics for high‐precision actuator applications near room temperature.

High efficiency near infrared emission from Pb1-xSrxSe Quantum dots in lithium aluminosilicate glass-ceramics

Pb1-xSrxSe quantum dots (QDs) were prepared in Li2O-Al2O3-SiO2 (LAS) glass-ceramics with 0–2.0 mol% SrO by conventional melt-quenching method. The near-infrared photoluminescence and photodarkening properties of Pb1-xSrxSe QDs in LAS glass-ceramics were studied. Upon the heat treatments of 490–550 °C for 10 h, there are LiAlO2 nanocrystals and PbSe QDs co-existed in the glassy matrix without SrO, and 1024–1745 nm near infrared emission from PbSe QDs were realized. With the increasing of SrO concentration from 0 to 2 mol%, the absorption wavelengths blue-shifted from 1738 to 1380 nm at 540 °C, the PL peak wavelengths blue-shifted from 1788 to 1538 nm at 540 °C. The blue-shifts are attributed to the increasing bandgap by incorporation of Sr2+ ions into PbSe crystalline lattice. Pb1-xSrxSe QDs display better photoinduced anti-darkening properties than pure PbSe QDs with the increasing of pumping power, and the Pb1-xSrxSe QDs embedded in the LAS glass with 2.0 mol% SrO shows the highest photoluminescence quantum yield of ∼36.9%.

Strontium- and peptide-modified silicate nanostructures for dual osteogenic and antimicrobial activity.

Developing multifunctional nanostructures that promote bone repair while fighting infection is highly desirable in bone regenerative therapies. Previous efforts have focused on achieving one property or another by altering the chemical makeup of nanostructures or using growth factors or antibiotics. We present nanostructures with several simultaneous functional attributes including positive effects of strontium on bone formation and prevention of osteoclast differentiation along with incorporation of antimicrobial peptides (AMP) to prevent infection. To form these multifunctional nanostructures, mesoporous calcium silicate (CaMSN) was modified with high levels of strontium. For this, CaMSNs were either partially substituted (20wt% Ca) or completely replaced with strontium (Sr) to form Sr-CaMSN or SrMSN. The mesoporous nature of these bioactive silicate nanostructures rendered a configuration for substantial AMP loading as well as their effective delivery. The physico-chemical and structural characterization of synthesized MSNs confirmed the mesoporous nature of the synthesized MSNs and their total surface area, pore size, pore volume and SBF-mediated bioactivity remained unaltered with the incorporation of Sr. However, biological evaluation confirmed that synthesized SrMSN upregulated osteogenic differentiation of mesenchymal stromal cells and significantly downregulated osteoclast differentiation. Also, the AMP-loaded MSNs prevented formation and growth of methicillin resistant Staphylococcus aureus (MRSA) biofilms. Thus, high Sr-containing AMP-loaded SrMSNs may combat MRSA-associated infection while promoting bone regeneration. The controlled availability of therapeutic Sr and AMP release as SrMSN degrade enables its potential application in bone tissue regeneration.

Sorption of Sr on montmorillonite clays: Theoretical and experimental study

Montmorillonite is a clay mineral widely used to remove pollutants from wastewater. The Sr sorption on montmorillonite was analyzed combining an experimental - theoretical approach. Sr sorption on natural and synthetic Na-montmorillonite was studied, characterizing the materials before and after Sr incorporation by X-ray diffraction and Zeta potential. The total specific surface area was also determined. Besides, ab-initio calculations were performed in order to investigate the sorption stability of the clay. The effect of the hydration of Sr atoms and the influence of the van der Waals interaction were evaluated. The experimental results indicated that Sr was sorbed on both, external and internal surfaces and that the total specific surface area seems to be relevant for the sorption process. The increasing in the interlayer space by Sr incorporation was associated with the cationic exchange, the hydration of the Sr atom and the relative humidity. Nuclear magnetic resonance parameters were calculated and compared with the experimental chemical shift and electric field gradient. The calculated Sr-chemical shift corresponds to the range for atomic coordination n = 6. Since there is no experimental data available for the principal component of the electric field gradient at Sr site, the obtained theoretical value stands as a prediction.

Carboxymethyl carrageenan immobilized on 3D-printed polycaprolactone scaffold for the adsorption of calcium phosphate/strontium phosphate adapted to bone regeneration

Three dimensional (3D) substrates based on natural and synthetic polymers enhance the osteogenic and mechanical properties of the bone tissue engineering scaffolds. Here, a novel bioactive composite scaffolds from polycaprolactone /kappa-carrageenan were developed for bone regeneration applications. 3D PCL scaffolds were fabricated by 3D printing method followed by coating with carboxymethyl kappa-carrageenan. This organic film was used to create calcium and strontium phosphate layers via a modified alternate soaking process in CaCl 2 /SrCl 2 and Na2HPO4 solutions in which calcium ions were replaced by strontium, with different amounts of strontium in the solutions. Various characterization techniques were executed to analyze the effects of strontium ion on the scaffold properties. The morphological results demonstrated the highly porous with interconnected pores and uniform pore sizes scaffolds. It was indicated that the highest crystallinity and compressive strength were obtained when 100% CaCl2 was replaced by SrCl2 in the solution (P-C-Sr). Incorporation of Sr onto the structure increased the degradation rate of the scaffolds. Mesenchymal stem cells (MSCs) culture on the scaffolds showed that Sr effectively improved attachment and viability of the MSCs and accelerated osteogenic differentiation as revealed by Alkaline phosphatase activity, calcium content and Real Time-Reverse transcription polymerase chain reaction assays.

Investigation of the Role of Sr and Development of Superior Sr-Doped Hexagonal BaCoO3−δ Perovskite Bifunctional OER/ORR Catalysts in Alkaline Media

Superior electrocatalytic activity of catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) enhances the reversible energy storage efficiency of metal–air batteries and electrochemical water splitting performances to produce hydrogen. Sr incorporation in the BaCoO3−δ lattice in the form of 2H-type Ba1–xSrxCoO3−δ (0 ≤ x ≤ 0.5) perovskites enhances both ORR and OER activities. A relatively low overpotential of 395 mV at 10 mA/cm2, lower Tafel slope of 64.95 mV dec–1, and good stability up to 500 cycles (10% reduction of current density and overpotential shift to a 0.04 V higher value) in a 0.1 M KOH electrolyte were obtained for the Ba0.5Sr0.5CoO3−δ electrode. Incorporation of Sr in the BaCoO3−δ lattice decreases the Co–O–Co bond angle that results in a superior orbital overlap between Co(3d) and O(2p) orbitals and a decrease in lattice parameters that generates lower surface oxygen separation pathways and a large number of active sites on the (011) planes, making Ba0.5Sr0.5CoO3−δ a superior catalyst with increased OER/ORR activity. The formation of oxygen-vacant CoO5 octahedra containing surface oxygen vacancies, the presence of Co3+/4+ valence states, and the superior overlap between O(2p)-Co(3d) bands (covalency increases) result in a higher electronic conductivity, a lower flat band potential, and improved OER and ORR activities. The key highlight of this work is the matching of the onset potential with the calculated flat band (Efb) potential from the Mott–Schottky plot. The Mott–Schottky plot was utilized to calculate the flat band potential (Efb) that indicates the basic information about the electrochemical interface potential between the electrode and the electrolyte, and in the case of Ba0.5Sr0.5CoO3−δ, it matches very well with the onset potential for the OER activity of the catalyst.

Simultaneous immobilization of radionuclides Sr and Cs by sodium zirconium phosphate type ceramics and its chemical durability

Sodium zirconium phosphate (NaZr2(PO4)3, NZP) type phosphate compounds have been considered as a candidate material for the immobilization of radionuclides. In this work, the highly densified NZP-type ceramic waste forms for immobilizing simulated radionuclides Sr and Cs, which were designed as the formula of Cs1-2xSrxZr2(PO4)3 (x = 0, 1/12, 2/12, 3/12, 4/12, 5/12, and 6/12), were prepared by microwave-assisted solid-state sintering method. The effects of Sr and Cs incorporation on the phase composition, microstructure, densification, and chemical durability of Cs1-2xSrxZr2(PO4)3 ceramic waste forms were systematically discussed. It was shown that the single CsZr2(PO4)3 (CsZP) phase was generated in the samples when x ≤ 2/12, while two phases of CsZP and Sr0.5Zr2(PO4)3 (SrZP) were formed when 3/12 ≤ x ≤ 5/12. The Rietveld refinement results revealed that Sr/Cs could be incorporated in the NZP crystal structure. The as-prepared samples all presented a well dense microstructure, whose relative density reached up to approximately 98% with Sr incorporation. In addition, the Product Consistency Test (PCT) leaching results demonstrated that the ceramics waste forms simultaneously immobilizing Sr and Cs exhibited superior leaching resistance, and the leaching rates of Sr and Cs elements were in the order of 10−3-10−4 g m−2 d−1. The increase of Sr incorporation brought about the decreased leaching rates of ceramic samples.

Preparation and Electrical Properties of Sr-Doped LaFeO3 Thin-Film Conversion Coatings for Solid Oxide Cell Steel Interconnect Applications

A study was conducted to explore the effects of Sr doping on the electrical properties of perovskite LaFeO3 thin-film protective conversion coatings grown onto a K41 ferritic stainless steel, a typical interconnect material for intermediate temperature solid oxide cell (SOC) applications. The Sr-doped coatings were prepared in La2O3- and SrO-containing molten carbonate baths with minor added amounts of nitrate salt for accelerated coating formation. For comparison purposes, undoped coatings were obtained using the same carbonate bath, with the only difference being that SrO was replaced by inert MgO. SEM/EDX and XRD analyses were used for coating characterization and confirmed the effective incorporation of Sr but not of Mg into the LaFeO3 layer. Although both the Sr-doped and undoped coatings consisted of a LaFeO3 layer grown above an inner Fe-Cr spinel, the coating thickness of the Sr-doped coating was distinctly higher, approximately 2 µm, which is twice that of the undoped coating. Electrical measurements in terms of Area-Specific Resistance (ASR) were conducted at 700 °C in air and showed that Sr-doping significantly improved the electrical conductivity of the coated K41 steel. Due to the Sr-doping, the ASR values of the coated steel dropped from 60 to 37 mΩ cm2 after 300 h of exposure, in spite of the higher Sr-doped coating thickness. The study concludes that Sr-doped thin-film perovskite coatings appear to be a promising solution for improved SOCs steel interconnect stability at intermediate temperatures.

Electrochemical determination of glucose in blood serum and sweat samples by the strontium doped Co3O4

• The conventional synthesis routes were investigated for the preparation of Sr doped Co 3 O 4 (Sr-Co 3 O 4 ). • The successful incorporation of Sr in Co 3 O 4 lattice was found for hydrothermal method. • The occupation of Sr in octahedral sites increases the non-stoichiometric oxygen in the Co 3 O 4 lattices. • These defected electronic structures were inspected against the electrocatalytic activity of glucose oxidation. • The Sr-Co 3 O 4 is applied in real-time monitoring of glucose in blood serum and sweat samples which received good recoveries. This work reports the noninvasive electrochemical determination of glucose by strontium doped cobaltic cobalt oxide nanostructures (Sr-Co 3 O 4 ). The Sr-Co 3 O 4 is prepared by three conventional methods namely hydrothermal, magnetic stirring, and ultrasound. Among all, the hydrothermal method effectively incorporated the Sr in the Co 3 O 4 lattice. The Sr percentage and Co oxidation states were investigated by x-ray photoelectron spectroscopy. The Sr has a more ionic radius than cobalt, therefore, it is occupied in the octahedral site. As a result, the non-stoichiometric oxygen content was increased in the Co 3 O 4 lattices, which are the main contributor to the electrochemical determination of glucose. The results revealed that hydrothermally synthesized Sr-Co 3 O 4 (HSC) exhibited improved electrocatalytic activity such as low peak potential (0.55 V) and high current (116 µA) towards glucose oxidation than the other electrocatalysts. The HSC/GCE revealed a good sensitivity (9.01 ± 0.15 µA mM −1 cm −2 ) and low LoD (31 ± 3 nM). Also, high selectivity was observed towards glucose detection in the presence of co-interfering species. Moreover, the Sr-Co 3 O 4 is applied in real-time monitoring of glucose in blood serum and sweat samples which received good recoveries.