Incorporation Of Se Research Articles

Spatially resolved photoluminescence analysis of the role of Se in CdSexTe1−x thin films

Evidence from cross-sectional electron microscopy has previously shown that Se passivates defects in CdSexTe1−x solar cells, and that this is the reason for better lifetimes and voltages in these devices. Here, we utilise spatially resolved photoluminescence measurements of CdSexTe1−x thin films on glass to directly study the effects of Se on carrier recombination in the material, isolated from the impact of conductive interfaces and without the need to prepare cross-sections through the samples. We find further evidence to support Se passivation of grain boundaries, but also identify an increase in below-bandgap photoluminescence that indicates the presence of Se-enhanced defects in grain interiors. Our results show that whilst Se treatment, in tandem with Cl passivation, does increase radiative efficiencies in CdSexTe1−x, it simultaneously increases the defect content within the grain interiors. This suggests that although it is beneficial overall, Se incorporation will still limit the maximum attainable optoelectronic properties of CdSexTe1−x thin films.

Se-incorporated polycaprolactone spherical polyhedron enhanced vitamin B2 loading and prolonged release for potential application in proliferative skin disorders

Development of novel drug vehicles for vitamin B2 (VitB2) delivery is very important for designing controllable release system to improve epidermal growth and bone metabolism. In this work, selenium (Se)-incorporated polycaprolactone (PCL) spherical polyhedrons are successfully synthesized via a single emulsion solvent evaporation method which is utilized to load VitB2 to fabricate cell-responsive Se-PCL@VitB2 delivery systems. Their physicochemical properties are characterized by DLS, SEM, XRD, FTIR, and TGA-DSC. The release kinetics of VitB2 or Se from the samples are investigated in PBS solution (pH = 2.0, 5.0, 7.4, 8.0 and 12.0). The cytocompatibilities are also evaluated with normal BMSC and epidermal HaCat cells. Results exhibit that Se-PCL@VitB2 particles presents spherical polyhedral morphology (approximately (3.25 ± 0.46) μm), negative surface charge (-(54.03 ± 2.94) mV), reduced crystallinity and good degradability. Stability experiments imply that both VitB2 and Se might be uniformly dispersed in PCL matrix. And the incorporation of Se facilely promotes the loading of VitB2. The encapsulation efficiency and loading capacity are (98.42 ± 1.06)% and (76.25 ± 1.27) for Se-PCL@VitB2 sample. Importantly, it exhibits more prolonged release of both VitB2 and Se in neutral PBS solution (pH = 7.4) than other pH conditions. Presumably, the electrostatic interaction between Se, VitB2 and PCL contribute to its release mode. Cell experiments show that Se-PCL@VitB2 presents strong cytotoxicity to HaCat cells mainly due to the cytotoxic effect of Se anions and PCL degradation products. However, it exhibits weak inhibitory effect on BMSC cells. These note that the synthesized Se-PCL@VitB2 particles can be promising drug vehicles for potential application in epidermal proliferative disorders.

Development and optimization of thyme-pennyroyal essential oils based active nanostructured lipid carrier (NLC) containing saffron extract with antioxidant and antimicrobial properties

The saffron extract-loaded nanostructured lipid carrier (NLC) was synthesized by the double emulsion (W/O/W) method for application as a preservative to increase the oxidative and microbial stability of French dressing. The optimization of the NLC system was carried out using a combined D-optimal design methodology and effect of thyme (TEOs)/pennyroyal (PEOs) essential oils, and polyglycerol ester (PGE)/polyglycerol polyricinolate (PGPR) surfactants ratios (independent variables) were investigated on the mean particle size, polydispersity, zeta potential, and encapsulation efficacy (dependent variables). The optimal formulation (NLC opt) was obtained as 90/10 thyme/pennyroyal essential oils and 90/10 polyglycerol esters/polyglycerol polyricinoleate ratio, which resulted in the lowest PDI and particle size (0.38 and 66.87 nm respectively), highest zeta potential and encapsulation efficiency (−26.7 mV and %78.88 respectively). Different techniques including transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analysis were used for the characterization of structure and physicochemical properties of the different NLC systems and confirmed successful incorporation of SE into NLC. The DPPH test showed decrement of antioxidant activity during 30 days of storage and IC50 value was lower in the SE-NLC (0.68 mg/ml) than in the free extract. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests against S. aureus, E. coli, and P. aeruginosa indicated that the SE did not have antibacterial properties. However, NLC formulations showed antimicrobial effect due to the presence of TEOs and PEOs essential oils. Peroxide value of control sample was the highest (8/35 O2/kg) and it was the lowest (3.75 O2/kg) in French dressing with SE-NLC.

N-Doped Carbon Modified (NixFe1-x)Se Supported on Vertical Graphene toward Efficient and Stable OER Performance.

NiFe-based nanomaterials are extensively studied as one of the promising candidates for the oxygen evolution reaction (OER). However, their practical application is still largely impeded by the unsatisfied activity and poor durability caused by the severe leaching of active species. Herein, a rapid and facile combustion method is developed to synthesize the vertical graphene (VG) supported N-doped carbon modified (NixFe1-x)Se composites (NC@(NixFe1-x)Se/VG). The interconnected heterostructure of obtained materials plays a vital role in boosting the catalytic performance, offering rich active sites and convenient pathways for rapid electron and ion transport. The incorporation of Se into NiFe facilitates the formation of active species via in situ surface reconstruction. According to density functional theory (DFT) calculations, the in situ formation of a Ni0.75Fe0.25Se/Ni0.75Fe0.25OOH layer significantly enhances the catalytic activity of NC@(NixFe1-x)Se/VG. Furthermore, the surface-adsorbed selenoxide species contribute to the stabilization of the catalytic active phase and increase the overall stability. The obtained NC@(NixFe1-x)Se/VG exhibits a low overpotential of 220mV at 20mAcm-2 and long-term stability over 300h. This work offers a novel perspective on the design and fabrication of OER electrocatalysts with high activity and stability.

Ladle slag–based binder for the solidification/stabilization of heavy-metal-rich industrial waste

Heavy metal pollution from industrial sources is a major environmental and health hazard on a global scale. This study introduces a solidification/stabilization method of industrial waste using a waste-based, ettringite-rich solid binder from ladle slag and gypsum for the immobilization of an industrial waste material with extremely high contents of several heavy metals. The importance of sulfate and water content on the immobilization efficiency and the use of citric acid to increase the processing time of the binder were studied. The leaching of Pb, Hg, Se, As, Cd, Cu, and Ni was measured, and X-ray powder diffraction, field-emission scanning electron microscopy, and field-emission electron probe microanalysis combined with wavelength-dispersive X-ray spectroscopy were used to analyze the structure of the hardened binder and the location of the heavy metals within. The study shows that the ladle slag/gypsum binder is suitable for the solidification/stabilization of heavy-metal-rich solid industrial waste. Hg, As, Cd, Cu, and Ni were fully immobilized in all scenarios covered in the study, whereas Pb and Se showed more complicated behaviors. The main immobilization method was encapsulation, and partial Se incorporation into ettringite was observed. The presence of citric acid increased the processing time of the binder without harming the immobilization, unless combined with low sulfate content.

Physical characterizations of Se-doped CdS nanostructures

The investigation thoroughly analyzes undoped and Se-doped CdS nanostructures using multiple techniques. Elemental composition analysis via EDS showed pure Cd and S in the undoped sample, while successful Se incorporation was confirmed in Se-doped samples. XRD revealed distinct CdS phases, with reduced intensity and broadening after Se-doping, indicating lower crystalline quality. The (111) peak shift confirmed Se substitution in the CdS lattice. Williamson-Hall and Monshi-Scherrer analyses demonstrated smaller crystallite sizes and increased lattice strain after Se-doping. FESEM displayed smaller grain sizes after Se-doping. PL analyses showed diminished crystalline quality and reduced intensity. UV–Vis indicated increased absorption and reduced transmission after Se-doping. Bandgap energy declined due to Se-doping and potential CdSe phase formation. Raman spectroscopy confirmed reduced crystalline quality. Se-doping enhances photon absorption, potentially improving optical properties for diverse applications. The study provides a detailed assessment of Se-doped CdS nanostructures, highlighting structural, optical, and morphological changes, valuable for various technological applications.

RuSe2 and CoSe2 Nanoparticles Incorporated Nitrogen-Doped Carbon as Efficient Trifunctional Electrocatalyst for Zinc-Air Batteries and Water Splitting.

The development of affordable, highly active, and stable trifunctional electrocatalysts is imperative for sustainable energy applications such as overall water splitting and rechargeable Zn-air battery. Herein, we report a composite electrocatalyst with RuSe2 and CoSe2 hybrid nanoparticles embedded in nitrogen-doped carbon (RuSe2CoSe2/NC) synthesized through a carbonization-adsorption-selenylation strategy. This electrocatalyst is a trifunctional electrocatalyst with excellent hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) activities. An in-depth study of the effect of Se on the electrocatalytic process was conducted. Notably, the incorporation of Se moderately adjusted electronic structure of Ru and Co, enhancing all three types of catalytic performance (HER, η10 = 31 mV; OER, η10 = 248 mV; ORR, E1/2 = 0.834 V) under alkaline condition with accelerated kinetics and improved stability. Density functional theory (DFT) calculation reveals that the (210) crystal facet of RuSe2 is the dominant HER active site as it exhibited the lowest ΔGH* value. The in situ Raman spectra unravel the evolution process of the local electronic environment of Co-Se and Ru-Se bonds, which synergistically promotes the formation of CoOOH as the active intermediate during the OER. The superior catalytic efficiency and remarkable durability of RuSe2CoSe2/NC as an electrode for water splitting and zinc-air battery devices demonstrate its great potential for energy storage and conversion devices.

Charge Transport and Ion Kinetics in 1D TiS2 Structures are Dependent on the Introduction of Selenium Extrinsic Atoms.

Improving charge insertion into intercalation hosts is essential for crucial energy and memory technologies. The layered material TiS2 provides a promising template for study, but further development of this compound demands improvement to its ion kinetics. Here, we report the incorporation of Se atoms into TiS2 nanobelts to address barriers related to sluggish ion motion in the material. TiS1.8Se0.2 nanobelts are synthesized through a solid-state method, and structural and electrochemical characterizations reveal that solid solutions based on TiS1.8Se0.2 nanobelts display increased interlayer spacing and electrical conductivity compared to pure TiS2 nanobelts. Cyclic voltammetry and electrochemical impedance spectroscopy indicate that the capacitive behavior of the TiS2 electrode is improved upon Se incorporation, particularly at low depths of discharge in the materials. The presence of Se in the structure can be directly related to an increased pseudocapacitive contribution to electrode behavior at a low Li+ content in the material and thus to improved ion kinetics in the TiS1.8Se0.2 nanobelts.

Vertical homogeneity study of Bridgman-grown Cd0.95Mn0.05Te0.98Se0.02 for radiation detection

This study investigates the potential of CdMnTeSe as a spectroscopic-grade semiconductor, focusing on the enhanced vertical homogeneity achieved through the incorporation of Mn and Se. The segregation coefficient of Mn in the CdTe matrix, approaching 1, indicates remarkable vertical homogeneity, promising high-yield and cost-effectiveness compared to zinc-based counterparts. Selenium addition synergistically reduces structural defects inside CdMnTeSe. The spectroscopic-grade Cd0.95Mn0.05Te0.98Se0.02′s exceptional vertical homogeneity was confirmed thorough characterizations, regardless of sample’s origination. This study guides for scale-up growth conditions by replacing Zn with Mn, offering superior homogeneity including high yield, cost-effectiveness, and the potential for large-volume CdTe-based single crystals.

Photoelectron holographic evidence for the incorporation site of Se and suppressed atomic displacement of the conducting layer of La(O,F)BiSSe

La(O,F)BiS2-x Se x is a layered material that is considered to be a candidate exotic superconductor as well as a promising thermoelectrical material. We performed soft X-ray photoelectron holography to study the Se incorporation site and the local atomic arrangement of the conducting layer. A comparison of the experimental holograms with the simulated holograms indicates that Se atoms preferentially occupy the S sites in the conducting Bi–S plane of La(O,F)BiS2. A comparison between the state-of-the-art holographic reconstructions of La(O,F)BiSSe and La(O,F)BiS2 suggests that Se substitution suppresses the displacement of S atoms in La(O,F)BiS2. These results provide photoelectron holographic evidence for the Se incorporation site and the Se-induced suppression of in-plane disorder.

Enhancing Oxygen Evolution Reaction Performance in Prussian Blue Analogues: Triple-Play of Metal Exsolution, Hollow Interiors, And Anionic Regulation.

Prussian blue analogs (PBAs) are promising catalysts for green hydrogen production. However, the rational design of high-performing PBAs is challenging, which requires an in-depth understanding of catalytic mechanism. Here FeMn@CoNi core-shell PBAs were employed as precursors, together with Se powders, in low-temperature pyrolysis in an argon atmosphere. This synthesis method enabled the partial dissociation of inner FeMn PBAs that resulted in hollow interiors, Ni nanoparticles (NPs) exsolution to the surface, and Se incorporation onto the PBA shell. The resulting material presented ultra-low oxygen evolution reaction (OER) overpotential (184mV at 10mA cm-2 ) and low Tafel slope (43.4mV dec-1 ), outperforming leading-edge PBA-based electrocatalysts. The mechanism responsible for such a high OER activity was revealed, assisted by DFT calculations and the surface examination before and after the OER process.The exsolved Ni NPs were found to help turn the PBAs into Se-doped core-shell metal oxyhydroxides during the OER, in which the heterojunction with Ni and the Se incorporation were combined to improve the OER kinetics. This work shows that efficient OER catalysts could be developed by using a novel synthesis method backed up by a sound understanding and control of the catalytic pathway. This article is protected by copyright. All rights reserved.

First Generation of Antioxidant Precursors for Bioisosteric Se-NSAIDs: Design, Synthesis, and In Vitro and In Vivo Anticancer Evaluation.

The introduction of selenium (Se) into organic scaffolds has been demonstrated to be a promising framework in the field of medicinal chemistry. A novel design of nonsteroidal anti-inflammatory drug (NSAID) derivatives based on a bioisosteric replacement via the incorporation of Se as diacyl diselenide is reported. The antioxidant activity was assessed using the DPPH radical scavenging assay. The new Se-NSAID derivatives bearing this unique combination showed antioxidant activity in a time- and dose-dependent manner, and also displayed different antiproliferative profiles in a panel of eight cancer cell lines as determined by the MTT assay. Ibuprofen derivative 5 was not only the most antioxidant agent, but also selectively induced toxicity in all the cancer cell lines tested (IC50 < 10 µM) while sparing nonmalignant cells, and induced apoptosis partially without enhancing the caspase 3/7 activity. Furthermore, NSAID derivative 5 significantly suppressed tumor growth in a subcutaneous colon cancer xenograft mouse model (10 mg/kg, TGI = 72%, and T/C = 38%) without exhibiting any apparent toxicity. To our knowledge, this work constitutes the first report on in vitro and in vivo anticancer activity of an unprecedented Se-NSAID hybrid derivative and its rational use for developing precursors for bioisosteric selenocompounds with appealing therapeutic applications.

Assessment of deep levels with selenium concentration in Cd1–xZnxTe1–ySey room temperature detector materials

Incorporation of Se into Cd1−xZnxTe (CZT) to form the quaternary compound semiconductor Cd1−xZnxTe1–ySey (CZTS) has proven to be an effective solution for compensating the major flaws associated with CZT, including poor homogeneity and high concentrations of electronically active deep levels that limit the performance of CZT detectors. In order to investigate how deep levels are affected by the Se concentration in CZTS, we performed photoinduced current transient spectroscopy (PICTS) measurements on CZTS crystals grown by the traveling heater method (THM) with 10% atomic Zn and varying atomic percentage of Se from 1.5% to 7.0%. The PICTS scans for up to 4% Se showed an exponential reduction in the capture cross section of deep levels associated with Te secondary phases in conjunction with an increase in a deep level positioned near the mid-gap, which initially increases the electron trapping time before degrading again at higher Se concentrations. The PICTS peaks present in 7% Se were anomalous relative to the other crystals and are expected to originate from transition metal impurities found in the lower-purity CdSe precursor material.

High-Performance Sodium-Ion Batteries Enabled by 3D Nanoflowers Comprised of Ternary Sn-Based Dichalcogenides Embedded in Nitrogen and Sulfur Dual-Doped Carbon.

To make sodium-ion batteries a realistic option for everyday energy storage, a practicable method is to enhance the kinetics of Na+ reactions through the development of structurally stable electrode materials. This study utilizes ternary Sn-based dichalcogenide (SnS1.5 Se0.5 ) in the design of electrode material to tackle several issues that adversely hinder the performance and longevity of sodium-ion batteries. First, the incorporation of Se into the SnS structure enhances its electrical conductivity and stability. Second, the ternary composition restricts the formation of intermediates during the desodiation/sodiation process, resulting in better electrode reaction reversibility. Finally, SnS1.5 Se0.5 lowers the diffusion barrier of Na, thereby facilitating rapid and efficient ion transport within the electrode material. Moreover, nitrogen and sulfur dual-doped carbon (NS-C) is used to enhance surface chemistry and ionic/electrical conductivity of SnS1.5 Se0.5 , leading to a pseudocapacitive storage effect that presents a promising potential for high-performance energy storage devices. The study has successfully developed a SnS1.5 Se0.5 /NS-C anode, exhibiting remarkable rate capability and cycle stability, retaining a capacity of 647 mAh g-1 even after 10000 cycles at 5 A g-1 in half-cell tests. In full-cell tests, Na3 V2 (PO4 )3 //SnS1.5 Se0.5 /NS-C delivers a high energy density of 176.6 Wh kg-1 . In addition, the Na+ storage mechanism of SnS1.5 Se0.5 /NS-C is explored through ex situ tests and DFT calculations. The findings suggest that the ternary Sn-based dichalcogenides can considerably enhance the performance of the anode, enabling efficient large-scale storage of sodium. These findings hold great promise for the advancement of high-performance energy storage devices for practical applications.

A Revisit of Superconductivity in 4Hb-TaS2−2xSe2x Single Crystals

Previous investigations of 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ mainly focused on the direct competition between superconductivity and charge density wave (CDW). However, the superconductivity itself, although has been prominently enhanced by isovalent Se substitution, has not been adequately investigated. Here, we performed a detailed electrical transport measurement down to 0.1 K on a series of 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ single crystals. A systematic fitting of the temperature-dependent resistance demonstrates that the decreased Debye temperatures ($\Theta_{D}$) and higher electron-phonon coupling constants ($\lambda_{e-p}$) at the optimal Se doping content raise the superconducting transition temperature ($T_c$). Additionally, we discovered that the incorporation of Se diminishes the degree of anisotropy of the superconductivity in the highly layered structure. More prominently, a comprehensive analysis of the vortex liquid phase region reveals that the optimally doped sample deviates from the canonical 2D Tinkham prediction but favors a linear trend with the variation of the external magnetic field. These findings emphasize the importance of interlayer interaction in this segregated superconducting-Mott-insulating system.

Nutrichemical alterations in different fractions of multiple-harvest alfalfa (Medicago sativa L.) green biomass fortified with various selenium forms

Background and AimsWet processed alfalfa-based products can provide high-quality concentrated protein, also contain nutrients and phytochemicals. Agronomic fortification can increase selenium (Se) incorporation into green biomass. For this reason, the aim was to investigate how different forms of Se are incorporated into the green biomass of multiple-harvest alfalfa and how they affect the chemical quality of the processed product candidates.MethodsIn this research, alfalfa was enriched with three forms of selenium at different concentrations [selenate (Se(VI)); selenite (Se(IV)); and red elemental Se (Se0)]. The fortified green biomass was fractionated into leaf protein concentrate (LPC), fiber and phytoserum, and changes in selenium content and speciation, protein and phytochemical composition were determined.ResultsTotal Se content in alfalfa fractions drastically reduced within the four consecutive harvests, particularly for Se(VI) and Se(IV) forms, and significantly varied according to the Se treatments. Selenomethionine (SeMet) was the predominant organic Se species in LPC (35.7–246.0 µg g −1 DW) and fiber (9.0- 47.7 µg g −1 DW) fractions. Se-fortification induced considerable changes in the crude protein of LPC, which varied between 29—45 (m/m)%. Phytochemical composition markedly varied among Se-treatments. Besides several flavonoids, aglycones and glycosyl derivatives, apigenin glucuronide, and apigenin were the most abundant with a concentration up to 170.85 µg g −1 DW. Medicagenic acid concentration was below 1.86 µg g −1 DW in LPC.ConclusionsSe-enhanced alfalfa green biomass could provide functional products, such as LPC, for human and animal consumption with enhanced nutritional value, including Se, protein, and phytochemical contents.

Effects of Amount and Chemical Form of Selenium Amendments on Forage Selenium Concentrations and Species Profiles.

Selenium (Se) agronomic biofortification of plants is effective for alleviating Se deficiencies in human and livestock populations. Less is known about how higher selenate amendment rates, or how foliar compared with granular selenate amendments affect forage Se concentrations. Therefore, we compared the effects of a higher sodium selenate foliar amendment rate (900 vs. 90g Se ha-1), and two selenate amendment methods (liquid foliar sodium selenate vs. granular slow-release Selcote Ultra® at 0, 45, and 90g Se ha-1) on Se concentrations and Se species in forages across Oregon. The 10 × amendment rate (900g Se ha-1) resulted in 6.4 × higher forage Se concentrations in the first cut (49.19 vs. 7.61mg Se kg-1 plant DM, respectively) compared with the 90gha-1 amendment rate, indicating that forages can tolerate higher selenate amendment rates. Most Se was incorporated as SeMet (75%) in the harvested portion of the forage (37mg Se kg-1 forage DM of the first cut) and only a limited amount was stored in the selenate reserve pool in the leaves (~ 5mg Se kg-1 forage DM). Higher application rates of selenate amendment increased forage Se concentrations in first and second cuts, but carry over in subsequent years was negligible. Application of foliar selenate vs. granular Selcote Ultra® amendments, between 0 and 90g Se ha-1, both resulted in a linear, dose-dependent increase in forage Se concentration. Amendments differed in their Se incorporation pattern (Se%), in that, first cut forage Se concentrations were higher with foliar selenate amendment and second, third, and residual (following spring) cut forage Se concentrations were higher with granular Selcote Ultra® amendment. Given the linear relationship between forage Se concentrations and whole-blood Se concentrations in livestock consuming Se-biofortified forage, we conclude that targeted grazing or other forage feeding strategies will allow producers to adapt to either selenate-amendment form.

Incorporation of Se (IV) Complexes based on Amino Acids in Biomatrixes in Hydrogel State: Effect of the Amino Acid on the Structure and Properties of Biomatrixes for Biomedical Applications

Selenium is a non-metal that shows biological interest since it is responsible for modulating various proteins at the micronutrient level in living beings. In this work, new complexes based on the Se (IV) ion with amino acids such as phenylalanine (Se-F), histidine (Se-H) and tryptophan (Se-T) were hydrothermally synthesized and characterized. These were incorporated into biomatrixes based on semi-interpenetrated polymeric networks (Semi-IPN) of collagen-polyurethane-guar gum (CPGG) by the microemulsion process using a mass ratio of 1 wt.% with respect to collagen. The structural and crystalline characteristics that the selenium-amino acid complexes show a performance in modulating the properties of the biomatrixes under study. The results indicate that the incorporation of the complex decreases the crosslinking of the hydrogel, generating granular surfaces with porosity dependent on the type of amino acid. The CPGG Se-T biomatrix shows a swelling capacity of 10200 ± 1100 higher than the CPGG base matrix; while the CPGG Se-F and CPGG Se-T biomatrixes present slow degradation at both physiological and acidic pH. Interestingly, the matrix that includes the Se-F complex significantly stimulates the metabolic activity of L929 fibroblasts for up to 48 h, stimulating their proliferation. The fibroblasts encapsulated on these novel biomatrixes show recurrent release capacity for up to 7 days, where the structure of the CPGG Se-H biomatrix exhibits greater release from the encapsulated cells. These results demonstrate that these innovative biomatrixes could be used in biomedical applications such as dermal tissue regeneration and cell release for a specific biological fate.

Effects of the fermentation process on the selenite metabolism and selenium incorporation and speciation in a probiotic Bifidobacterium longum.

The influence of the fermentation process on selenite metabolism by a probiotic Bifidobacterium longum DD98 (B. longum DD98), and its consequent enrichment in selenium (Se) were studied. The effects of sodium selenite (Na2SeO3) concentration (18-400 μg/mL), feeding time (12, 16, and 24 h), and fermentation stage (secondary and tertiary fermentation) were evaluated by measuring i) the total Se content and its distribution between the water-soluble metabolome fraction and the water-insoluble fraction; ii) the total concentrations of the two principal Se-compounds produced: selenomethionine (SeMet) and γ-glutamyl-selenomethionine (γ-Glu-SeMet), and iii) the speciation of Se in the metabolite fraction. The results revealed that the fermentation process notably changed the Se incorporation into metabolites (γ-Glu-SeMet and free SeMet) and proteins (bound-SeMet) in B. longum DD98. In particular, the production of SeMet was negatively correlated to that of γ-Glu-SeMet when no red precipitate was seen in the bacteria. The study offers a tool for the control of the optimization of the fermentation process towards the desired molecular speciation of the incorporated Se and hence contributes to the production of Se-enriched probiotics with good qualities and bioactivities.

Improved Catalytic Activity and Stability of Co9S8 by Se Incorporation for Efficient Oxygen Evolution Reaction.

Combining an excellent electrocatalytic activity with the good structural stability of Co9S8 remains challenging for the oxygen evolution reaction (OER). In this study, density functional theory was used to demonstrate the importance of moderate adsorption strength with *O and *OOH intermediate species on Co9S8 for achieving excellent electrocatalytic performances. A novel strategy was proposed to effectively optimize the *O oxidation to *OOH by introducing Se heteroatoms to adjust adsorption of the two intermediates. This process also allowed prediction of the simultaneous enhancement of the structural stability of Co9S8 due to the weak electronegativity of a Se dopant. The experimental results demonstrated that Se doping can regulate the charge density of Co2+ and Co3+ in Co9S8-xSex, leading to a substantially improved OER performance of Co9S8-xSex. As a result, our Co9S6.91Se1.09 electrode exhibited an overpotential of 271 mV at 10 mA cm-2 in a 1.0 M KOH solution. In particular, it also demonstrated an excellent stability (∼120 h) under a current density of 10 mA cm-2, indicating the potential for practical applications. Overall, the proposed strategy looks promising for regulating the electronic structures and improving the electrochemical performances of sulfide materials.