BoMyrosinase plays an essential role in sulforaphane accumulation in response to selenite treatment in broccoli

Sulforaphane, a naturally specialized metabolite, plays significant roles in human disease prevention and plant defense. Myrosinase(MY) is a key gene responsible for the catalysis of sulforaphane formation, but the molecular mechanisms through which MY regulates sulforaphane biosynthesis in plants remains largely unknown. Here, we discovered that the change of sulforaphane content in broccoli sprouts caused by exogenous selenite treatments is positively related to BoMY expression. BoMY overexpression in the Arabidopsis thaliana tgg1 mutants could dramatically increase myrosinase activity and sulforaphane content in the rosette leaves of 35S::BoMY/tgg1 and rescue its phenotypes.Moreover, an obvious increase of myrosinase activity and sulforaphane content was displayed in transgenic BoMY-overexpressed broccoli lines.In addition, a 2 033 bp promoter fragment of BoMY was isolated. Yeast one-hybrid(Y1H) library screening experiment uncovered that one bHLH transcription factor, BoFAMA, could directly bind to BoMY promoter to activate its expression, which was further evidenced by Y1H assay and dual-luciferase reporter assay. BoFAMA is a selenite-responsive transcription factor that is highly expressed in broccoli leaves;its protein is solely localized to nucleus. Additionally, genetic evidence suggested that the knockdown of FAMA gene in Arabidopsis thaliana could significantly decrease sulforaphane yield by inhibiting the expression of myrosinase genes. Interestingly, exogenous selenite supply could partially restore the low level of sulforaphane content in transgenic Arabidopsis FAMA-silencing plants. Our findings uncover a novel function of FAMAMY module in the regulation of selenite-mediated sulforaphane synthesis and provide a new insights into the molecular mechanism by which selenite regulates the accumulation of sulforaphane in plants.

Sodium selenite promotes neurological function recovery after spinal cord injury by inhibiting ferroptosis

Ferroptosis is a recently discovered form of iron-dependent cell death,which occurs during the pathological process of various central nervous system diseases or injuries,including secondary spinal cord injury.Selenium has been shown to promote neurological function recovery after cerebral hemorrhage by inhibiting ferroptosis.However,whether selenium can promote neurological function recovery after spinal cord injury as well as the underlying mechanism remain poorly understood.In this study,we injected sodium selenite(3μL,2.5μM)into the injury site of a rat model of T10 vertebral contusion injury 10 minutes after spinal cord injury modeling.We found that sodium selenite treatment greatly decreased iron concentration and levels of the lipid peroxidation products malondialdehyde and 4-hydroxynonenal.Furthermore,sodium selenite increased the protein and mRNA expression of specificity protein 1 and glutathione peroxidase 4,promoted the survival of neurons and oligodendrocytes,inhibited the proliferation of astrocytes,and promoted the recovery of locomotive function of rats with spinal cord injury.These findings suggest that sodium selenite can improve the locomotive function of rats with spinal cord injury possibly through the inhibition of ferroptosis via the specificity protein 1/glutathione peroxidase 4 pathway.

Redifferentiation of Human Gastric Cancer Cells Induced by Ascorbic Acid and Sodium Selenite

Objective To explore the effects and mechanisms of ascorbic acid (AA) and sodium selenite (SS) on growth inhibition and redifferentiation in human gastric cancer cells. Methods In the present study, trypan blue dye exclusion method was used to determine the cell growth curve and mitotic index, cell electrophoresis and colonogenic potential were used as the indexes of redifferentiation. In order to find out the mechanisms of redifferentiation, the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) were assayed, the content of malondialdehyde (MDA), reduced glutathione (GSH) and H2O2 were evaluated. Results After treatment with AA 3 mol/L + SS 2μmol/L, the growth rate and mitotic index of human gastric cancer cells (MGc-803) decreased remarkably. The indexes related with cell malignancy were alleviated. For example, cell surface charge was obviously decreased, the electrophoresis rate was dropped from 2.21 to 1.15μm·s-1·V-1·cm-1. The indexes related with cell redifferentiation were promoted. For example, the colonogenic potential was decreased to 93.5%. These results indicated that redifferentiation of human gastric cancer cells was successfully induced by AA + SS. The activities of SOD and GPX were significantly higher, while the activity of CAT was slower in treated group than that in the control. The content of MDA was slightly decreased, GSH was sharply decreased, and H2O2 content was dramatically increased. Conclusion These results indicated that combination of ascorbic acid and sodium selenite may induce the redifferentiation of human gastric cancer cells and inhibit cell growth by virtue of enhancing the activities of antioxidative enzymes and inducing the formation of H2O2, and altering the cell redox status. Combination of ascorbic acid and sodium selenite may be a potent anticancer agent for human gastric cancer.

Hydrothermal Synthesis and Crystal Structure of a Novel Selenite-chloride:[Cd_4(SeO_3)_2Cl_4(H_2O)]_n with a Three-dimensional Framework

A novel three-dimensional（3-D） compound [Cd4（SeO3）2Cl4（H2O）]n（1） was prepared from a hydrothermal reaction and structurally characterized.Compound 1 crystallizes in the space group Fmmm of the orthorhombic system with eight formula units in a cell：a = 15.5165（4）,b = 17.5090（9）,c = 7.3318（5） ,V = 1991.9（2） 3,Cd4Cl4H2O7Se2,Mr = 863.38,Dc = 5.758 g/cm3,S = 1.075,μ（MoKα） = 16.820 mm-1,F（000） = 3088,R = 0.0427 and wR = 0.1220.Compound 1 features a 3-D structure with the cadmium atoms having two different coordination environments,i.e.,six-and eight-coordination geometries.Two different chain-like structures of cadmium-oxo polyhedra are interconnect to each other to give a 2-D layer of [Cd4（SeO3）2（H2O）]n4n＋.Between the [Cd4（SeO3）2（H2O）]n4n＋ layers is a novel chloride layer.A 3-D framework is constructed from these [Cd4（SeO3）2（H2O）]n4n＋ layers linked by the chloride layers.

Comparison of the impact of epigallocatechin gallate and ellagic acid in an experimental cataract model induced by sodium selenite

AIM：To compare the potential protective effects of epigallocatechin gallate（EGCG） and ellagic acid（EA） in an experimental cataract model.●METHODS：Twenty-eight Spraque-Dawley rat pups were assigned into four groups.All the rats,except for those in the control group,were injected subcutaneously sodium selenite to induce experimental cataract on the postpartum ninth day,and between 10 th and 14 th days.Rats in the sham,EGCG,and EA groups were intraperitoneally administered 50 mg/（kg·d） saline solution,50 mg/（kg·d） EGCG and 200 mg/（kg·d） EA,respectively.The reduced glutathione（GSH） and malondialdehyde（MDA） levels,total antioxidant status（TAS） and total oxidant status（TOS） in lens supernatants were measured.RESULTS：The mean cataract gradings in EGCG and EA groups were found to be significantly lower than that in sham group（P〈0.001）.The mean GSH levels and TASs in EGCG and EA groups were significantly higher than that in sham group while mean MDA levels and TOSs in EGCG and EA groups were significantly lower than that in the sham group（P〈0.001）.CONCLUSION：EGCG and EA have protective effects on cataract development via the inhibition of oxidative stress.

Sodium selenite ameliorates dextran sulfate sodiuminduced chronic colitis in mice by decreasing Th1, Th17, and γδT and increasing CD4(+)CD25(+) regulatory T-cell responses

AIM To assess the effect of sodium selenite on the severity of dextran sulfate sodium(DSS)-induced colitis in C57BL/6 mice.METHODS Mice were randomly divided into four groups(n = 10/group): normal group, selenium(Se) group, chronic colitis group, and Se + chronic colitis group. The mice were sacrificed on day 26. Survival rates, clinical symptoms, colon length, and histological changes were determined. The percentages and absolute numbers of immune system cells in the lamina propria lymphocytes(LPL) of the colon, the expression of m RNA in colon tissue, and the concentrations of Th1, Th17, and Treg cytokines in LPL from the large intestine, were measured.RESULTS Se significantly ameliorated the symptoms of colitis and histological injury(P < 0.05 each), increasing the proportions of neutrophils and CD4+ CD25+ T cells(P < 0.05 each) and decreasing the proportions of γδT cells, CD4+, CD4+CD44+, and CD4+ CD69+ T cells in LPL(P < 0.05 each). Moreover, Se reduced the expression of IL-6, IFN-γ, IL-17 A, IL-21, T-bet, and RORγt(P < 0.05 each), but enhanced the expression of IL-10 and Foxp3(P < 0.05 each). CONCLUSION These results suggest that Se protects against DSSinduced chronic colitis perhaps by increasing the number of CD4(+)CD25(+) Tregs that suppress the secretion of proinflammatory cytokines and populations of Th1, Th17, and γδT cells.

Antitumour Activity of Chitosan Hydrogen Selenites

Chitosans reacted with selenious acid to prepare chitosan hydrogen selenites, which were found to be growth-inhibitory against sarcoma 180 solid tumor. The results indicated that the activity also depended on the molecular weight of chitosan supports.

Alabaster and Selenite Gypsum:I-Dehydration-Rehydration Comparison Studies

Two types of gypsum raw materials, selenite and alabaster, were used to prepare dental stone (a-hemihydrate). Gypsum lumps (0.8~2.5 cm) were hydrothermally treated at 135, 160 and 180癈 for 6, 2 and 1 h respectively. The physicochemical properties and composition characteristics of the a-hemihydrates prepared from selenite and alabaster raw gypsum were determined. The results indicated that both the selenite and alabaster raw gypsum show the same chemical and mineralogical composition of calcium sulphate dihydrate. They differs only in their microstructure, selenite raw gypsum exhibits perfect regular crystals while alabaster gypsum, on the other hand, exhibits irregular, large size and interlocked crystals. Selenite is more accessible to dehydration than alabaster raw gypsum. The a-hemihydrate samples prepared from alabaster raw gypsum showed a very short setting time and a lower compressive strength values in relation to that prepared from selenite gypsum. The compressive strength values of the all prepared samples were higher than that specified by A.D.A specification for dental use. To optimize the setting time of both products further studies are needed.

Protective Role of C-Phycocyanin Against Secondary Changes During Sodium Selenite Mediated Cataractogenesis

Age related cataract is the leading cause of blindness associated with accumulation of oxidative stress in the eye lens.The present investigation reveals the rational of the beneficial effects of the natural compound C-phycocyanin(CPC)is beneficial when administered to rat pups to protect against the secondary effects of sodium selenite induced cataractogenesis.A single subcutaneous dose of sodium selenite(19 lmol/kg body weight)on the 10th day of postpartum is adequate to induce cataract in rat pups.Serum biochemical parameters,such as the level of electrolytes,mean activities of anti-oxidant enzymes i.e.superoxide dismutase,catalase and reduced glutathione were observed to be significantly altered during selenite induced cataractogenic process.Histopathological examination revealed signs of degradation of normal cell architecture in the liver,kidney and eye lens.Interestingly,the deleterious effects of sodium selenite toxicity were restored with the simultaneous treatment with C-PC.The results suggest that an administration of 200 mg/kg body weight of C-PC has the ability to prevent/alter the secondary changes reflected in the serum biochemical and histological modifications in rats exposed to sodium selenite.These results complement the beneficial role of C-PC of cyanobacterial origin as a efficacious anti-cataractogenic agent against sodium selenite toxicity.

Syntheses, Structures, and Some Properties of Three Vanadium Selenites

Three novel vanadium selenites with the formulae [（VO2）（1,10-phenanthtoline）（SeO3H）]2 1, [（VO2）（2,2′-bipyridine）]2（SeO3） 2 and [（VO）（H2O）（SeO3）2]2（HaEDD） 3 （EDD = N1,N1′-（ethane-1,2-diyl）diethane-1,2-diamine） were hydrothermally synthesized, and characterized with elemental analysis, FT-IR spectrum, Raman spectrum, TG-DTA analysis, EPR spectra, and single-crystal X-ray diffraction analysis. Compound I belongs to the triclinic system, space group P1^- with a = 7.7527（5）, b = 9.5345（10）, c = 9.8192（8） A^°, α = 92.712（3）, β = 105.540（3）, γ = 108.154（4）°, V = 657.66（1） A^°^3, Mr = 782.22, Z = 1, F（000） = 384,μ（MoKa） = 3.544 mm^-1, R = 0.0432 and wR = 0.1142; Compound 2 is of orthorhombic system, space group F212121 with a = 7.6574（15）, b = 14.916（3）, c = 19.085（4） A, V = 2179.8（8） Aa, Mr = 605.21, Z = 4, F（000） = 1200, μ（MoKa） = 2.579 mm^-1, R = 0.0338 and wR = 0.0658; Compound 3 belongs to the triclinic system, space group P1^- with a = 9.247（2）, b = 9.659（2）, c = 7.2651（19） A^°, α = 98.171（7）, β = 103.709（5）, γ = 114.712（13）°, V = 550.9（2） A^°^3, Mr = 828.03, Z = 1, F（000） = 400, μ（MoKa） = 7.537 mm^-1, R = 0.0641 and wR = 0.2118. Compound 1 is constructed from alternating corner-shared [VO4N2] octahedra and SeO3H units, forming a dimeric vanadium unit. These assemblies are further linked into an infinite chain via hydrogen bonds along the a axis. In the structure of 2, two distinct V centers form centrosymmetric [V2O6N4] clusters through edge-sharing, and the SeO3 unit serves as a capping unit to fix the oxovanadate cluster. In the structure of 3, each [VO6] octahedron shares four oxygen atoms with adjacent Se atoms, while every SeO3 unit shares two oxygen atoms with neighboring V atoms. This connectivity of alternating VO6 and SeO3 units results in a joint-like chain. Based on the TGA analysis, these three compounds are thermally stable under 200℃ .

Analysis of Protein Characteristics of Selenite Transporter OsPT2 in Rice

OsPT2,which is a selenite transporter in rice,belongs to rice phosphate transporter family OsPT. In this study,the amino acid sequence information of OsPT family members was collected using NCBI database. Bioinformatics method was employed to analyze physical and chemical properties and protein structure of OsPT2 and its homologous relationship with other members of the family. The results indicated that OsPT2 was a stable alkaline hydrophobic protein embedded in the cell membrane. The protein contained 11 transmembrane domains,and consisted of 45. 08% of alpha helix,16. 48% of extended strand,10. 80% of beta turn and 27. 65% of random coil,forming a barrel-like three-dimensional structure. Members in OsPT family had high homology and could be divided into 5 subgroups.OsP T2 had closer relationship with OsPT1 and OsPT3. This study could provide a basis for further revealing of molecular mechanism of selenite transport in rice.

Sodium selenite may be not the optimal speciation as an effective therapy for arsenic-induced anxiety-/depression-like behavior

Major depressive disorder is a serious and prevalent neuropsychiatric disorder,affecting more than 350 million people worldwide.Here,sodium selenite(SS)was selected as the selenite supplement to improve the behavior in a mouse model of depression induced by As.SS may be not the optimal speciation for selenite supplementation and the source of the SS used in the study was not disclosed.There are many mouse models of depression and anxiety;however,in the current study,a classical mouse model of depression was not used.Thus,several questions still need to be further discussed.Taken together,the results indicate that SS may be not the optimal speciation as an effective therapy for As-induced anxiety-/depression-like behavior.

Effect of Sodium Selenite-Chitosan Compound Preservative on Storability of Kumquats

[Objectives]To explore the effect of sodium selenite-chitosan compound preservative on storability of kumquats.[Methods]Under the condition of room temperature,fresh kumquats were coated with different concentrations of sodium selenite-chitosan compound preservative,respectively.[Results]Sodium selenite-chitosan compound preservative reduced the weight loss rate,delayed the decline of vitamin C,soluble solids,titratable acid and GSH contents,slowed down the accumulation of MDA,inhibited the increase of PPO activity,and increased to a certain extent the activity of SOD in fresh kumquats.[Conclusions]Sodium selenite-chitosan compound preservative maintained the quality and prolonged the shelf life of kumquats.The preservation effect of compound preservative composed of 4 mg/L sodium selenite and 8 g/L chitosan was the best.

Synthesis,Structure,and Magnetic Properties of a New Cobalt Selenite Ca_2Co(HSeO_3)_2(SeO_3)_2

A new cobalt selenite,Ca_2Co（HSeO3）_2（SeO_3）_2,was synthesized by a conventional hydrothermal method. Single-crystal X-ray diffraction analysis reveals that Ca_2Co（HSeO3）_2（SeO_3）_2 crystallizes in triclinic system,space group P1,with a = 5.330（5）,b = 7.047（7）,c = 8.457（9） ？,V = 285.0（5） ？~3,Z = 1,Mr = 646.93,Dc = 3.769,μ = 15.235 mm^（-1）,F（000） = 299.0,the final R = 0.0452 and wR = 0.1169 for observed 1265 reflections with I 〉 2σ（I）. The title compound consists of isolated chains built from CoO_6 octahedra and SeO_3 pyramids. In this structure,the chains are separated by Ca^（2＋） cations. Magnetic measurements confirm that the title compound exhibits long-range antiferromagnetic ordering at 3 K and field-induced magnetic transition at 2 T.

Inhibitory Effect of Sodium Selenite on Microsatellite Instability of RER^+ Colorectal Cancer Cells

Objective Investigation of the effects of sodium selenite on genetic instability of human tumor cells via its role in alteration of microsatellite sequence(MS) of RER + (replication error) colon cancer cell line. Methods RER + and RER - human colon cancer cell lines, RKO or SW480, were used as hosts for lipofection with pcmv car in which a foreign(CA) 14 repeat was inserted in the coding sequence of LacZ reporter gene, resulting in misreading LacZ frame. Any mutation which makes the base number of (CA) 14 tract to be 3 fold will resume the normal reading frame of the reporter gene, and thus lead to expression and production of bioactive β galactosidase. To test the effect of selenite on MI(microsatellite instability) of tumor cells, a series of concentrations of selenite were administered in cell culture in vitro. Variable expression of bioactive β galactosidase of transfectant cells resulted from selenite administration was measured by A reading at λ410 after X gal staining; Results Mutations of the exogenous(CA) 14 developed and maintained in pcmv car transfectant RKO cells but not in SW480 cells. It was found that blue cell frequency of RKO transfectant cells was markedly reduced after incubation of cells with 5 μmol/L of selenite for 5 days, at which concentration it was not toxic to cell growth. However, selenite at lower concentration of 1μmol/L didn′t exhibit suppression of blue cell rate until cell′s exposure to it for a longer period up to 5 weeks or more. Conclusion Our data showed that selenite displayed inhibitory effect on MI of human cancer cells and thus demonstrated its beneficial role in stabilization of human genomic DNA.

Mechanistic research:Selenium regulates virulence factors,reducing adhesion ability and inflammatory damage of Helicobacter pylori

BACKGROUND The pathogenicity of Helicobacter pylori is dependent on factors including the environment and the host.Although selenium is closely related to pathogenicity as an environmental factor,the specific correlation between them remains unclear.AIM To investigate how selenium acts on virulence factors and reduces their toxicity.METHODS H.pylori strains were induced by sodium selenite.The expression of cytotoxin-associated protein A(CagA)and vacuolating cytotoxin gene A(VacA)was determined by quantitative PCR and Western blotting.Transcriptomics was used to analyze CagA,CagM,CagE,Cag1,Cag3,and CagT.C57BL/6A mice were infected with the attenuated strains subjected to sodium selenite induction,and H.pylori colonization,inflammatory reactions,and the cell adhesion ability of H.pylori were assessed.RESULTS CagA and VacA expression was upregulated at first and then downregulated in the H.pylori strains after sodium selenite treatment.Their expression was significantly and steadily downregulated after the 5th cycle(10 d).Transcriptome analysis revealed that sodium selenite altered the levels affect H.pylori virulence factors such as CagA,CagM,CagE,Cag1,Cag3,and CagT.Of these factors,CagM and CagE expression was continuously downregulated and further downregulated after 2 h of induction with sodium selenite.Moreover,CagT expression was upregulated before the 3rd cycle(6 d)and significantly downregulated after the 5th cycle.Cag1 and Cag3 expression was upregulated and downregulated,respectively,but no significant change was observed by the 5th cycle.C57BL/6A mice were infected with the attenuated strains subjected to sodium selenite induction.The extent of H.pylori colonization in the stomach increased;however,sodium selenite also induced a mild inflammatory reaction in the gastric mucosa of H.pylori-infected mice,and the cell adhesion ability of H.pylori was significantly weakened.CONCLUSION These results demonstrate that H.pylori displayed virulence attenuation after the 10th d of sodium selenite treatment.Sodium selenite is a low toxicity compound with strong stability that can reduce the cell adhesion ability of H.pylori,thus mitigating the inflammatory damage to the gastric mucosa.

Two selenium tolerant Lysinibacillus sp. strains are capable of reducing selenite to elemental Se efficiently under aerobic conditions

Microbes play important roles in the transport and transformation of selenium(Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides,respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations(MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L.xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles(SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra-or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized Se NPs would have potential applications in agriculture, food, environment and medicine.

Hydrogen selenide,a vital metabolite of sodium selenite,uncouples the sulfilimine bond and promotes the reversal of liver fibrosis

Sodium selenite has alleviating effects on liver fibrosis;however,its therapeutic molecular mechanism remains unclear.Herein,hydrogen selenide,a major metabolite of Na_(2)SeO_(3),was tested to uncouple the sulfilimine bond in collagen IV,the biomarker of liver fibrosis.A mouse model of liver fibrosis was constructed via a CCl_(4)-induced method,followed by the administration of 0.2 mg kg−1 Na_(2)SeO_(3)via gavage three times per week for 4 weeks.Changes in H2Se,NADPH,and H_(2)O_(2)levels were monitored in real time by using NIR-H2Se,DCI-MQ-NADPH,and H_(2)O_(2)probes in vivo,respectively.H_(2)Se continuously accumulated in the liver throughout the Na_(2)SeO_(3)treatment period,but the levels of NADPH and H_(2)O_(2)decreased.The expression of collagen IV was analyzed through Western blot and liquid chromatography-mass spectrometry.Results confirmed that the sulfilimine bond of collagen IV in the fibrotic mouse livers could be broken by H2Se with the Na_(2)SeO_(3)treatment.Therefore,the therapeutic effect of Na_(2)SeO_(3)on liver fibrosis could be mainly attributed to H_(2)Se that uncoupled the sulfilimine bond to induce collagen IV degradation.This study provided a reasonable explanation for the molecular mechanism of the in vivo function of Na_(2)SeO_(3)and the prevention of liver fibrosis by administering inorganic selenium.

Influence of inherent iron and oxygen concentrations on selenite sorption process using bentonite

The oxygen concentration and inherent Fe in bentonite have a significant influence on the Se(IV) sorption process.In this study,the sorption of selenite on natural bentonite was investigated using a batch experiment method,and the distribution coefficient(K_d)values were obtained in the pH range from 2.0 to 10.0 under oxic/anoxic conditions.The K_d values always reached a maximum value at a pH of 4 under oxic conditions and at a pH of 8 under anoxic conditions;meanwhile,the K_d value under anoxic conditions was larger than the value under oxic conditions,especially in regard to the maximum K_d values.The oxygen conditions have a significant influence on the ratio of redox-sensitive Fe^(2+)/Fe^(3+),which was closely related to the difference in the K_d values under both oxic/anoxic conditions.Ferric selenite and green rust could be responsible for the maximum K_d values under oxic/anoxic conditions.In the leaching experiments,we found that the Fe^(2+) in bentonite could replace Mg^(2+) and Al^(3+) in the octahedral sheet.Spectroscopy methods,such as Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD) and X-ray absorption spectroscopy(XAS) were used to characterize the surface properties of the samples after reaction.Overall,this study shows that the addition of Fe^(2+)-containing materials into backfill/buffer materials under anoxic condition could enhance the sorption of ^(79)Se(IV).

Exploration of cobalt selenite-carbon composite porous nanofibers as anode for sodium-ion batteries and unveiling their conversion reaction mechanism

Efforts have been made to develop a promising anode material with a novel composition for sodiumion batteries(SIBs).In this study,the sodium-ion storage mechanism of transition metal selenite that comprises transition metal cation coupled with two anions is studied.Amorphous cobalt selenite(CoSeO_(3))-carbon composite nanofibers containing numerous pores are synthesized via electrospinning process.Upon heat treatment of the electrospun nanofibers containing selenium,CoSe_(2)nanoclusters are formed.During the subsequent oxidation,CoSe_(2)transformed into amorphous CoSeO_(3)and some part of carbon was oxidized into CO_(2),leaving the pores inside the nanofiber.To unveil the electrochemical reaction mechanism,analytical methods including cyclic voltammetry,ex-situ X-ray photoelectron spectroscopy,ex-situ transmission electron microscopy,and in-situ electrochemical impedance spectroscopy techniques were adopted.Based on the analyses,the following conversion reaction from the second cycle onward is suggested:CoO+xSeO_(2)+(1-x)Se+4(x+1)Na^(+)+4(x+1)e~-?Co+(2x+1)Na_(2)O+Na_(2)Se.Furthermore,the electrochemical properties of porous CoSeO_(3)-carbon composite nanofibers are analyzed in detail.The anode material exhibited stable cycle stability up to 200 cycles at 0.5 A g^(-1)and high rate performance up to 5 A g^(-1).