Se Ratio Research Articles

Chemical characteristics of wintertime aerosol and cloud over the Sea of Japan based on aircraft and ground measurements

Chemical characteristics of aerosols and clouds from the boundary layer to the middle troposphere (0–5.2 km) were investigated over the Sea of Japan during winter seasons and were shown to be influenced by the Asian winter monsoon blowing from Siberia. The Na+/Cl− ratio of aerosols and clouds indicates that most Na+ and Cl− originated from sea salts. Positive correlations were found between sea spray aerosol production flux and (Na+ + Cl−) concentrations of boundary layer aerosols (R2 = 0.53–0.71) or clouds (R2 = 0.45–0.69), suggesting that strong winter monsoon winds intensified the production of primary sea salts and the associated clouds. The degree of Cl loss for aerosols near ground level was higher than that at high altitudes, which may be attributed to the distance from emission sources, whereas clouds were scarcely accompanied by Cl loss. The higher (NO3− + non-sea salt (nss)-SO42–)/(NH4+ + nss-Ca2+) ratio of aerosols in the boundary layer compared with the free troposphere may be attributed to the effect of relative humidity on acid gases (SO2, H2SO4, and HNO3) uptake to aerosols. The (NO3− + nss-SO42–)/(NH4+ + nss-Ca2+) ratio of clouds (0.67 on average) implies insufficient amounts of base ions to neutralize acid ions. The Se(VI)/Se(IV) ratios of aerosols in the boundary layer were mostly higher than those of the free troposphere, which may be attributed to the concentrations of oxidants for selenium in aerosol particles. The Se(IV)/Se(VI) ratios of clouds (1.34 ± 0.62) were found to differ significantly from those of aerosols (0.50 ± 0.32 for the boundary layer, 27.92 ± 52.42 for the free troposphere), which strongly suggests that the oxidation state of Se in cloud indicates redox equilibrium.

Synthesis of CdSe QDs with various stoichiometric ratios of Se under the influence of ethanol/ethylenediamine for photovoltaic application

Synthesis of CdSe QDs with various stoichiometric ratios of Se under the influence of ethanol/ethylenediamine for photovoltaic application

Extraction of Se(iv) and Se(vi) from aqueous HCl solution by using a diamide-containing tertiary amine.

Here, we investigated the mechanism underlying the extraction of Se(iv) and Se(vi) from aqueous HCl solutions by N-2-ethylhexyl-bis(N-di-2-ethylhexyl-ethylamide)amine (EHBAA). In addition to examining extraction behavior, we also elucidated structural properties of the dominant Se species in solution. Two types of aqueous HCl solutions were prepared by dissolving a SeIV oxide or a SeVI salt. X-ray absorption near edge structure analyses revealed that Se(vi) was reduced to Se(iv) in 8 M HCl. Using 0.5 M EHBAA, ∼50% of Se(vi) was extracted from 0.5 M HCl. In contrast, Se(iv) was hardly extracted from 0.5 to 5 M HCl; however, at molar concentrations above 5 M, the extraction efficiency of Se(iv) increased drastically, reaching ∼85%. Slope analyses for the distribution ratios of Se(iv) in 8 M HCl and Se(vi) in 0.5 M HCl showed that apparent stoichiometries of Se(iv) or Se(vi) to EHBAA were 1 : 1 and 1 : 2, respectively. Extended X-ray absorption fine structure measurements revealed that the inner-sphere of the Se(iv) and Se(vi) complexes extracted with EHBAA was [SeOCl2] and [SeO4]2-, respectively. Together, these results indicate that Se(iv) is extracted from 8 M HCl with EHBAA via a solvation-type reaction, whereas Se(vi) is extracted from 0.5 M HCl via an anion-exchange-type reaction.

Bi3Se4 nanodots in porous carbon: A new anode candidate for fast lithium/sodium storage

• A new Bi 3 Se 4 -based anode material is successfully developed and firstly applied in lithium and sodium ion batteries. • For the first time, in-situ XRD is employed to disclose the lithium storage mechanism of Bi 3 Se 4 /C-800 anode. • C-Se bonds are proved to strengthen the heterointerface and improve reaction knietics via experiments and theoretical calculations. • Bi 3 Se 4 /C-800 electrode exhibits ultra-long cycling life and fast-charging capability. Bismuth selenide has attracted considerable attention as anode materials due to its high theoretical capacity. However, its development has been limited to Bi 2 Se 3 -based composites up to now. Herein, a facile strategy to regulate the atomic ratio of Bi x Se y is propsed and a new Bi 3 Se 4 -based anode material is successfully developed. Firstly, in-situ XRD technique is employed to disclose the combined conversion and alloying reactions mechanism. Besides, a uniform structure with Bi 3 Se 4 nanodots embedded within a sheet-like carbon framework is verified, ensuring fast kinetics and efficient alleviation of stress derived from dramatic volume expansion. Furthermore, experimental results combined with theoretical calculations prove the formation of robust interfacial C-Se bonds, which could simultaneously enhance the inherent bulk electronic conductivity and accelerate ionic transportation. As expected, Bi 3 Se 4 -based electrode achieves an ultralong cycle life of 1500 cycles at a high current density of 2 A g −1 and fast lithium storage capability of 211 mAh g −1 at an ultrahigh rate of 20 A g −1 . Such exceptional performance fully proves the huge potential of Bi 3 Se 4 -based electrode and also provides guidance for the exploration of other high-performance Bi x Se y -based anodes. A new Bi 3 Se 4 -based anode material is proposed via facilely optimizing the selenization temperature. Advanced in-situ technique combined with computational simulations are employed to evaluate phase evolution, lithium storage mechanism and electrolchemical performance. Consequently, Bi 3 Se 4 /C hybrid exhibits fast-charging capability and durable cycling life benefiteed from robust structure and stable C-Se bonds.

Absorption-based electromagnetic interference shielding composites with sandwich structure by one-step electrodeposition method

The absorption-dominant electromagnetic interference (EMI) shielding materials with light weight, great flexibility, fast heat dissipation and excellent mechanical strength are highly demanded in civil and military applications. In this regard, the absorption-based CNT/Co composite film with sandwich structure (Co/Co-CNT/Co layer) was designed for highly EMI shielding performance and heat dissipation. The existence of Co layers on CNT/Co composite film has suitable impedance matching between film and free space, which can increase EM waves absorption and decrease EM waves reflection. Appropriately incorporating Co nanoparticles into the CNT film can facilitate the interfacial polarization, dipole polarization and dielectric loss derived from conduction loss, thus CNT/Co composite film shows high EMI shielding effectiveness (EMI SE: 49 dB), tensile strength (120 MPa), excellent electrical and thermal conductivity of 61.1 S/cm and 66.8 W/mK respectively. Furthermore, the ratio of absorption (SEA) and total EMI SE (SET) for pristine CNT film is 86.64% and for CNT/Co composite film is 93.31%, and the ratios of A/R for pristine CNT film (0.58) and CNT/Co composite film (1.20) manifest that the EMI shielding mechanism transforms from reflection to absorption. This work offers a novel method to develop the sandwich-structure composites with absorption-dominant EMI shielding performance in the application of advanced multifunctional electromagnetic shielding field.

Electrochemical properties of Bi2Se3 layers semiconductor elaborated by electrodeposition

• Bismuth selenide (Bi 2 Se 3 ) thin films with nanoparticles was electrodeposited from a nitric bath. • The electrodeposition mechanism of Bi 2 Se 3 alloy into ITO substrate is three-dimensional instantaneous nucleation. • The reaction of Bi 2 Se 3 deposition is quasi-reversible controlled by the diffusion process, with the diffusion coefficient D of Bi and Se in the Bi 2 Se 3 system are 1.756 10 -7 cm 2 s -1 and 0.196 10 -7 cm 2 s -1 , respectively. • The interesting properties of the resulting Bi 2 Se 3 make it a relevant material for future developments in photovoltaics and optoelectronics. The semiconductor, Bi 2 Se 3 layers was electrochemically deposited on Indium Tin Oxide substrate (ITO) from a nitric acid, Bi (NO 3 ) 3 ·5H 2 O and H 2 SeO 3 solution. The results of the electrochemical behavior of Bi 2 Se 3 were as follows: Cyclic voltammetry (CV) studies revealed that the electrodeposition of Bi 2 Se 3 was performed at a negative potential of −0.22 V vs SCE, according to a quasi-reversible reaction controlled by the diffusion process. Chronoamperometry (CA) showed that the electrodeposition of Bi 2 Se 3 follows a 3D instantaneous nucleation model with diffusion-controlled growth. X-ray diffraction analysis indicated that the resulting layers at −0.22 V vs SCE exhibited a Rhombohedral Bi 2 Se 3 structure with a preferred orientation (1 1 3) and the 2:3 stoichiometric ratio of Bi and Se was checked by EDS quantitative analysis. SEM images revealed the formation of a uniform size mainly consisting of nanoparticles with spherical shapes. The Bi 2 Se 3 obtained layers are n -type semiconductors with an optical band gap of 2.35 eV.

Metabolome-wide association study suggests antagonistic responses to cadmium and selenium in diseased human lungs

Background and Aim: Cadmium (Cd) is a toxic environmental metal that binds selenium (Se) and contributes to many lung diseases. Humans have widespread exposures to Cd through diet and cigarette smoking, and studies in rodent models show that Se can protect against Cd toxicities. We performed metabolome-wide association study (MWAS) of Cd and Se in diseased and non-diseased human lungs to test for possible Cd-Se interactions. Methods: We analyzed tissue from 31 human lung explants, including 25 from patients with end-stage lung diseases, including idiopathic pulmonary fibrosis, cystic fibrosis, and chronic obstructive lung disease (COPD)/emphysema. We used ICP-MS (Inductively Coupled Plasma Mass Spectrometry) to measure Cd and Se, and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) to conduct metabolomics analysis. Results: Metabolic pathway associations with Cd were similar to those previously observed in experimental models, including amino acid, lipid and energy-related pathways, many of which were also associated with Se. Two-way hierarchical cluster analysis (HCA) of metabolites associated with Cd revealed separation of individuals according to disease, with COPD/emphysema in the highest Cd cluster, and non-diseased individuals in the lowest Cd cluster. HCA of Se-associated metabolites revealed that COPD/emphysema also clustered by lower Se compared to others. More pathway associations occurred for the ratio of Cd:Se than either Cd or Se alone, suggesting an antagonistic relationship, and network analysis showed that most metabolites were associated with either Cd or Se. A relatively small number of polyunsaturated fatty acids and metabolites associated with inflammatory signaling had high Eigenvector centrality scores, suggesting a central mechanism of antagonistic interaction. Conclusions: Overall, the data show that metabolic pathway responses in human lung vary with Cd:Se ratio in a pattern suggesting that Se is antagonistic to Cd toxicity. Keyword: Human lung disease, environmental metals, metabolic disruption, high-resolution metabolomics.

Non-essential heavy metals and protective effects of selenium against mercury toxicity in endangered Australian sea lion (Neophoca cinerea) pups with hookworm disease

The endangered Australian sea lion, Neophoca cinerea, faces ongoing population decline. Identification of key threats to N. cinerea population recovery, including disease and pollutants, is an objective of the species’ recovery plan. Previous studies have identified Uncinaria sanguinis, an intestinal nematode, as a significant cause of disease and mortality in N. cinerea pups. Given the impact of heavy metals on the immune response, investigation of these pollutants is critical. To this end, the concentrations of arsenic (As), total mercury (Hg), cadmium (Cd), chromium (Cr), lead (Pb) and selenium (Se) were determined in blood collected from N. cinerea pups sampled during the 2017/18, 2019 and 2020/21 breeding seasons at Seal Bay Conservation Park, South Australia.Significant differences (p < 0.05) in Hg, As, Cr, and Se concentrations and molar ratio of Se:Hg were seen between breeding seasons. Pup age, maternal parity and inter-individual foraging behaviour were considered factors driving these differences. The concentrations of Hg (357, 198 and 241 µg/L) and As (225, 834 and 608 µg/L) were high in 2017/18, 2019 and 2020/21 respectively with Hg concentrations in the blood of N. cinerea pups above toxicological thresholds reported for marine mammals. The concentration of Se (1332, 647, 763 µg/L) and molar ratio of Se:Hg (9.47, 7.98 and 6.82) were low compared to other pinniped pups, indicating potential vulnerability of pups to the toxic effects of Hg. Significant (p < 0.05) negative associations for Pb and Cd with several red blood cell parameters suggest they could be exacerbating the anaemia caused by hookworm disease. Temporal (age-related) changes in element concentrations were also seen, such that pup age needs to be considered when interpreting bioaccumulation patterns.Further investigation of the role of elevated heavy metal concentrations on N. cinerea pup health, disease and development is recommended, particularly with respect to immunological impacts.

Se-NiSe2 hybrid nanosheet arrays with self-regulated elemental Se for efficient alkaline water splitting

• NiSe 2 nanosheet with self-regulated elemental Se adsorbing has been prepared. • Ionic Se/elemental Se ratio has been regulated. • Roles of ionic Se and elemental Se in electrocatalysis have been identified. • Theoretical calculation has been applied to confirm the experimental result. • Bifunctional water splitting performance has been evaluated. Understanding the catalytic mechanism of non-noble transition metal electrocatalysts is crucial to designing high-efficiency, low-cost, and durable alternative electrocatalysts for water splitting which comprises the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, Se-NiSe 2 hybrid nanosheets with a self-regulated ratio of ionic Se (I-Se) to elemental Se (E-Se) are designed on carbon cloth by solution synthesis and hydrothermal processing. The effects of the I-Se/E-Se ratios on the electrocatalytic characteristics in HER and OER are investigated systematically both experimentally and theoretically. The optimized bifunctional electrocatalyst needs overpotentials of only 133 mV to deliver an HER current density of 10 mA cm −2 and 350 mV to generate an OER current density of 100 mA cm −2 in 1.0 mol L −1 KOH. Based on the density-functional theory calculation, surface-adsorbed E-Se is beneficial to optimizing the electron environment and the adsorption/desorption free energy of hydrogen/water of the hybrid catalyst, consequently facilitating the electrocatalytic water splitting process. There is a proper I-Se/E-Se ratio to improve the catalytic activity and kinetics of the reaction and the optimized E-Se adsorption amount can balance the interactions between I-Se and E-Se, so that the catalyst can achieve appropriate Se-H binding and active site exposure for the excellent electrocatalytic activity. To demonstrate the practicality, the assembled symmetrical device can be powered by an AA battery to produce hydrogen and oxygen synchronously. Our results provide a deeper understanding of the catalytic mechanism of transition metal selenides in water splitting and insights into the design of high-efficiency and low-cost electrocatalysts in energy-related applications.

Controlling Electronic Energy Structure of Near-IR-Responsive Ag(In,Ga)(S,Se)2 Quantum Dots for In Vivo Bioimaging

[Introduction] Since cancer is a leading cause of death worldwide, early diagnostic and treatment observation using biosensors becomes urgent. To date, the development of the biosensors is limited to the utilization of fluorescent probes such as organic dyes or fluorescent proteins, which suffer from various weakness[1]. Therefore, new probes that are more photostable than current organic fluorophores are needed.Semiconductor called quantum dots (QDs) of a few nanometers in size exhibit unique photochemical properties different from their bulk materials, owing to the quantum size effect. Binary QDs composed of group II−VI or IV−VI semiconductors, such as CdS, CdSe, and PbS, have been intensively investigated because of intense PL, high quantum yield, resistance to photo-bleaching, and broad excitation with narrow emission bands, which made them ideal for high contrast optical imaging of biological systems. However, notable toxicity associated with Cd and Pb causes serious limitations in practical use. Recently, mixed-cation QDs, such as ZnAgInS[2], AgInGaS[3], and AgInGaSe[4], have been an environmentally friendly alternative to conventional binary QDs. Their photochemical properties were controlled through the composition of QDs as well as their particle size. Controlling the composition of QDs containing multinary chalcogen elements, that is, mixed-anion QDs, is also expected to be another strategy to tune their physicochemical properties, but the method to prepare such QDs showing intense PL has not been developed well.In this study, we report the strategy to prepare Ag(In, Ga)(S, Se)2 (AIGSSe) QDs, of tunable photochemical properties, such as energy gap (Eg) and photoluminescence peak, with the ratio of Se/S in the particles. [Experimental] AIGSSe QDs were synthesized by a solution-phase synthesis method. A mixture of AgOAc, In(acac)3, and Ga(acac)3 was used as a metal ion precursor, and that of thiourea and selenourea was used as a chalcogen precursor. These were added to a test tube with a mixture solvent of oleylamine and dodecane thiol, in which the ratio of Se/(Se+S) varied from 0 to 1.0. The solution was heated at 100~250 °C, and then formed QDs were isolated by adding methanol. The resulting wet precipitates were washed several times with ethanol, followed by dissolving in chloroform. Thus-obtained AIGSSe QDs were surface-coated by GaSx shell to improve PL property. Furthermore, these QDs were incorporated into unilamellar liposomes of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) to make them dissolved in aqueous solution before being injected into the back of a mouse, and their PL intensity was measured. [Results and Discussion] The absorption onset was red-shifted from 580 nm to 830 nm with an increase in the Se/(S+Se) ratio in preparation, indicating that the Eg of QDs was decreased from 1.9 to 1.5 eV with an increase in the Se/(Se+S) ratio from 0 to 1.0 in QDs. Thus-obtained AIGSSe QDs exhibited broad PL peaks with relatively weak intensities. However, the surface coating of AIGSSe QDs with GaSx shell (AIGSSe@GaSx) remarkably enhanced the intensity of PL peak. The PL quantum yield (QY) of AIGSSe QDs varied in the range of 2~43%, but QDs with each Se/(S+Se) ratio exhibited increased QY after surface coating with GaSx shell. Especially, AIGSSe@GaSx with Se/(S+Se) = 0 had the highest QY value as much as 50%. The PL peak wavelength was red-shifted from 580 nm to 785 nm with a decrease in the Eg of AIGSSe core, the FWHM of PL peak being varied in the range of 0.147 ~ 0.357 eV.TEM measurement revealed that the AIGSSe@GaSx QDs were spherical, and their average size was almost constant at ca. 4 nm with narrow size distribution, regardless of Se/(Se+S) in preparation. AIGSSe@GaSx QDs with Se/(Se+S) = 0.50 exhibited a sharp PL peak at 785 nm in first biological window, which was suitable for in vivo imaging. These QDs were encapsulated with DSPC liposomes so that the QDs were dispersed in aqueous solution. Thus-obtained AIGSSe@GaSx QD-DSPC liposomes maintained a sharp band-edge PL peak even in an aqueous dispersion, in which the PLQY was slightly decreased from 25% in chloroform to 21% in aqueous dispersions but was high enough to be used as a near-IR PL probe. We successfully detected PL emission from the QDs through the skin of a mouse, and the PL intensity was proportional to the concentration of injected QDs. [References] [1] T. Jin, et al., J Mater Chem B, 2020, 8, 10686.[2] T. Kameyama, et al., J. Phys. Chem. C, 2018, 122, 13705.[3] T. Kameyama, et al., ACS Appl. Mater. Interfaces, 2018, 10, 42844.[4] T. Kameyama, et al., ACS Appl. Nano Mater., 2020, 3, 3275.

Selenium Speciation in Paired Whole Blood and Serum Samples From Pregnant Bangladeshi Women

ObjectivesWe aimed to characterize the relative concentrations of selected major selenium (Se) species in paired whole blood (WB) and serum samples collected from pregnant women at delivery in Dhaka, Bangladesh. Speciation analysis enabled differentiation of organic and inorganic Se, and quantification of the nutritionally bioactive reduced selenometabolite, selenoneine, which has been previously observed in WB from populations with high levels of fish consumption. MethodsPaired WB and serum specimens (n = 515) were collected at delivery among participants of the Maternal Vitamin D for Infant Growth trial. Quantification of total serum Se and total WBSe was conducted using inductively coupled plasma mass spectrometry (ICP-MS) at the Centers for Disease Control and Prevention (CDC). Speciation analyses were conducted in a subset of pairs (n = 20) to quantify selenometabolites using liquid chromatography coupled to ICP-MS at the University of Cincinnati. Concentrations of inorganic Se (IV), selenoneine, selenocysteine (SeCys), selenomethioneine (SeMet) were expressed as % of total Se. We assessed concordance between results generated across laboratories using paired t-tests. ResultsOverall (n = 515), mean (SD) serum Se and WBSe concentrations (μg/L) were 70 (14) and 135 (18), respectively, such that average Serum Se as a proportion of WBSe was 52%. Findings were similar in the speciation subset (n = 20) [total Serum Se: 82 (19); total WBSe: 138 (18), with a ratio of serum Se to WBSe: 60%]. Sums of quantified species accounted for most of the total serum Se (72 (10); 88% of total) and WBSe (135 (16); 98%). Organic forms were predominant in both serum and WB: SeCys: 15 (2) and 20 (3); and SeMet: 54 (9) and 92 (13), respectively. Selenoneine was detected in WBSe at mean concentrations of 24 (5) μg/L. Together, SeMet and selenoneine accounted for 85% of the additional WBSe not present in serum. Inorganic Se was not detected in WB but comprised 5% of serum. ConclusionsApproximately half of the Se in whole blood is in the cellular fraction. SeMet was enriched in WB and the most abundant form, relative to selenoneine which was not found in serum. Small amounts of inorganic serum Se may be artifactual due to freeze-thaw related degradation. These findings require confirmation in other settings but suggest that serum Se may not be a suitable biomarker of population status. Funding SourcesBMGF.

Annealing temperature effect on structural and optoelectronic properties of γ-In2Se3 thin films towards highly stable photodetector applications

Metal chalcogenide-based photodetectors have been studied extensively in recent years. However, the dark current, detective spectral ranges, responsivities, and response time are still unsatisfactory. Also, the major challenge for photodetector material is the deposition of large-scale material, a high-quality film with high reliability and low variability. In this work, we have synthesized Indium selenide (γ-In2Se3) thin films using the RF magnetron sputtering technique. We have thoroughly investigated the effect of annealing temperature on structural, optical, morphological, and photo-sensing properties of the synthesized thin films. Low angle XRD confirms the formation of hexagonal γ-In2Se3 films. The crystallite size increases from 56 nm to 64 nm with an increase in annealing temperature. Raman spectroscopy and XPS techniques confirm the γ phase of indium selenide. FE-SEM analysis revealed that the synthesized films are compact and uniform. Also, they are free from holes and cracks, which is necessary for semiconductor applications. The agglomeration of particles is observed with an increase in annealing temperature. The EDS spectra revealed that synthesized γ-In2Se3 films have ideal stoichiometry with In:Se ratio of 2:3. The UV–visible spectroscopy analysis showed a slight decrease in bandgap from 2.0 eV to 1.93 eV with an increase in annealing temperature. Other optical properties, such as absorption coefficient (α), extinction coefficient (k), the real and imaginary part of dielectric constant, optical conductivity, etc., of synthesized γ-In2Se3 films critically depend on the annealing temperature. Finally, the synthesized γ-In2Se3 thin films were used to fabricate photodetectors on ITO-coated interdigital electrodes. All γ-In2Se3 photodetector shows good stability and repeatability under dark and illumination conditions. The rise and decay time decrease with increase in annealing temperature. Photodetector with γ-In2Se3 thin film annealed at 300 °C exhibited excellent photoresponsivity (1.12 mA/ W) and stable photoswitching behavior. A fast rise (0.22 s) and decay time (2.85 s) were observed for the prepared photodetector. Our work demonstrates that γ-In2Se3 photodetector can be a promising material for photodetection applications.

Enhancing the thermoelectric performance of Ag2Se by non-stoichiometric defects

Ag2Se is an attractive candidate for room temperature thermoelectric applications because of its extremely low thermal conductivity, large power factor, and excellent mechanical properties. However, its performance is difficult to be improved effectively by doping other atoms. The traditional synthesis processes have the disadvantages of low yield, complex steps, and long period. In this study, the Ag2Se1+x samples were rapidly synthesized by the melting method via changing the ratio of Ag and Se. The carrier concentration and mobility of Ag2Se are optimized by adding excess Se, which could regulate non-stoichiometric defects in the process of synthesis. A high Seebeck coefficient of ∼136.0 μV K−1, a large power factor of ∼3000.0 μW m−1 K−2, and the maximum figure of merit (ZT) of ∼1.02 of the Ag2Se1.015 sample have been achieved at 375 K. The ZT value is 2.3 times than that of the pristine sample (Ag2Se). The mechanical properties of the molting sample are comparable to state-of-the-art thermoelectric materials. Finally, the highest ZT value of the material is predicted by factor B. This work provides an idea for further optimizing Ag2Se-based and other non-stoichiometric thermoelectric semiconductors by a slight excess of Se. Moreover, the fast synthesis technology can significantly save time and energy, which manifests great advantages to the wholesale manufacturing industry.

The Effects of Temperature and Time of Heat Treatment on Thermo-Mechanical Properties of Custom-Made NiTi Orthodontic Closed Coil Springs.

Nickel-Titanium (NiTi) springs have been increasingly used in orthodontics; however, no optimum condition of heat treatment has been reported. Therefore, this research was conducted to determine the optimum heat-treatment temperature and duration for the fabrication of NiTi-closed coil springs by investigating their effects on thermo-mechanical properties. As-drawn straight NiTi wires of 0.2 mm diameter were used to fabricate closed coil springs of 0.9 mm lumen diameter. The springs were heat-treated at three different temperatures (400, 450, and 500 °C) with three different durations (20, 40, and 60 min). Electron Probe Micro-Analysis (EPMA) and Differential Scanning Calorimetry (DSC) were used to investigate element composition and thermo-mechanical properties, respectively. Custom-made NiTi closed coil springs composed of 49.41%-Ti and 50.57%-Ni by atomic weight, where their DSC curves of 500 °C presented the obvious endothermic and exothermic peaks, and the austenite finish temperature (Af) were approximately 25 °C. With increasing temperature, deactivation curves presented decreased plateau slopes generating higher superelastic ratios (SE ratios). At 500 °C, closed coil springs showed superelastic tendency with lower stress hysteresis. The thermo-mechanical properties were significantly influenced by heat-treatment temperature rather than duration. The optimum parameter appeared to be 500 °C for 40 min to produce appropriate force delivery levels, relatively low plateau slope, and lower hysteresis for orthodontic use.

Can mixed anion transition metal dichalcogenide electrodes enhance the performance of electrochemical energy storage devices? The case of MoS2xSe2(1-x)

A significant enhancement in performance of electrochemical energy storage devices has been achieved by optimizing the S:Se ratio in electrodes made from MoS2xSe2(1-x) alloys synthesized through a facile hydrothermal technique. In symmetric two electrode configuration, the transition metal dichalcogenide with S: Se ratio of 1:1 exhibits a battery type behavior and delivers high specific capacitance of 1020F g−1 and a capacity value of 85 mAh at 10 A g−1. The electrochemical energy storage device exhibits an excellent rate capability of 96 % over the current density range of 10 to 20 A g−1. The enhanced performance is largely due to the reduced contact resistance brought in by an enhancement of electrical conductivity in the mixed cation system, in addition to the enhanced surface area of the two-dimensional material. Analysis of the electronic structure using density functional theory calculations reveals that anion vacancies created during synthesis of the material enhance the electrical conductivity of MoSSe by reducing the bandgap, which is confirmed by electrochemical impedance spectroscopy studies. The work demonstrates the importance of fine-tuning the electrical properties and morphology of the electrode material in improving the performance of electrochemical energy storage devices.

FeSe and Fe3Se4 encapsulated in mesoporous carbon for flexible solid-state supercapacitor

Metal selenides have been developed as promising alternatives of metal oxides in energy storage field due to their high conductivity and low bandgap. However, the synthesis of selenides usually suffers from the low melting point and strong volatility of selenium at temperatures higher than 217 ℃. Herein, a facile strategy was developed to prepare iron selenides using a template of Se-contained MOF gel, which could in situ immobilize Se powder due to the fast gelation process, resulting a porous, uniform and tight precursor. By adjusting the mole ratio of Fe and Se in the precursor, FeSe@C and Fe3Se4@C were controllably synthesized with rich mesopores and excellent carbon-encapsulation structure. The kinetics analysis indicates that these unique structures are beneficial for improving electrode kinetics, charge/ion-transfer resistance and electrochemical stability. FeSe@C and Fe3Se4@C exhibit significant capacitances (611.0F g−1 and 569.0F g−1 at 1 A g−1), and excellent cycling properties (94.22% and 93.28% retention after 2000 charge–discharge cycles at 5 A g−1). When estimated in practical application, the flexible solid-state symmetric supercapacitor of FeSe@C//Fe3Se4@C delivers a high Csp of 160.1F g−1, the superior energy density of 32.1 W h kg−1 and a high specific power density of 5998 W kg−1 with 89.5% capacitance retention after 5000 cycles, and the outstanding flexibility.

Comparison of effect of parenteral and oral supplementation of Selenium and vitamin E on selected antioxidant parameters and udder health of dairy cows.

The aim of this study was to compare the effect of parenteral and oral supplementation of Selenium (Se) and vitamin E (VTE) on selected antioxidant parameters in blood and colostrum as well as their effect on the incidence of mastitis in dairy cows during the final phase of gravidity (6 weeks) and first two weeks after calving. For the practical part of the study 36 dairy cows of Slovak pied breed in the second to fourth lactation-gestation cycle were selected. The animals weredivided into three groups: the control (C) and two experimental groups (D1 and D2). The selected groups were treated as follows: in group D1 products containing Se (Selevit inj.) and vitamin E (Erevit sol. inj.) were administered intramuscularly twice, six and three weeks prior to parturition; in group D2 a vitamin-minerals supplement in the form of sodium selenite (Na2SeO3) and dl-α-tocopherol acetate were supplemented orally for six weeks calving. The blood samples were collected from the vena jugularis in dairy cows approximately 42 days before calving (control sampling), on parturition day, and the 14th day after calving. Higher concentrations of Se and VTE were found in the blood plasma samples of both experimental groups collected on the day of parturition. In addition, the orally supplemented group (D2) showed higher Se and α-tocopherol concentrations in blood plasma on the14th day after calving as well a reduction of occurrence of mastitis by about 25 % compared to the control group. The relationship between inflammatory response and oxidative stress was also confirmed. The concentrations of milk malondialdehyde indicating lipid peroxidation during mastitis were significantly higher in milk samples from infected cows than in milk samples from healthy animals in each monitored group. In order to prevent oxidative stress and moderate inflammatory response in dairy cows it is very important to optimally balance their nutritive needs with an appropriate ratio of Se and VTE supplements. Therefore we still recommend supplementation of the cows' postpartum dietwith 0.5 mg of Se/kg dry matter (DM) and 102 mg of dl-α-tocopherol acetate/kg DM to stabilize their optimal blood levels, stimulate the activity of glutathione peroxidase and reduce the incidence of mastitis.

Exceptional power factor of flexible Ag/Ag2Se thermoelectric composite films

Herein, we fabricate a high-performance Ag/Ag2Se thermoelectric (TE) film by a novel method. Firstly, Ag/Ag2Se nano-dendritic composite powders were synthesized by a microwave-assisted synthesis method, then the powders were vacuum filtrated on nylon filter membrane followed by hot-pressing. Through optimization of Ag:Se ratios, a maximum power factor of 2436 ± 240 μW m−1 K−2 at room temperature has been acquired. It is one of the best values reported for n-type flexible TE films to date. The high TE performance can be ascribed to the synergy effect between Ag and Ag2Se. Besides, the composite film also shows good flexibility: 94% and 87% of the electrical conductivity are maintained, respectively, when it is subjected to a compressive force and a tensile force after 1000 bending cycles along an 8-mm diameter rod. Meanwhile, the film also shows good stability in air and good moisture resistance. A 6-leg flexible TE generator assembled with the optimized film shows a low internal resistance of ∼ 5 Ω, mainly owing to high electrical conductivity of ∼ 3030 ± 132 S cm−1 of the film. It outputs a voltage and a maximum power of 16.1 mV and 6.08 μW (corresponding power density of ∼ 13.56 W m−2), respectively, at a temperature gradient of 29.6 K. This work provides a great path for the fabrication of exceptional high-performance n-type flexible TE films, which will certainly promote the practical applications of TE films.

Influence of structure phase transition on the thermoelectric properties of Cu2Se1-x Te x liquid-like compounds.

Copper chalcogenide Cu2(Se,Te) compounds are well known as typical p-type thermoelectric materials with a figure of merit (ZT) that can be optimized by the ratio of Se : Te. Here, by using the mechanical alloying and solid-state reaction methods, Te was substituted into Se sites within Cu2Se as the formula Cu2Se1−xTex (x = 0.1, 0.2, 0.25, and 0.3). The observed changes in structural phase, grain morphologies, and grain size were recorded by XRD and FE-SEM imaging with the appearance of the secondary phase of Cu2Te, with a Te content of x = 0.25. The layered structure morphology was observed more clearly at the high Te content. The electrical conductivity was greatly increased with enriched Te content while the maximum Seebeck coefficient was obtained in the Cu2Se0.75Te0.25 sample. Accordingly, a power factor value of up to 9.84 μW cm−1 K−2 at 773 K was achieved. The appearance of a Cu2Te phase with a Te content of 0.25 created a structural phase transition which results in a ZT value of 1.35 at 773 K in the Cu2Se0.75Te0.25 sample.

Back Contact Optimization for Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; Solar Cells

Antimony selenide (Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt;) has advantages of low-toxicity, abundant and excellent photoelectric properties. It is widely considered as one of the most promising light-harvesting materials for thin-film solar cells. However, the power conversion efficiency of the Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; thin-film solar cell is still far inferior to that of cadmium telluride, copper indium gallium selenium and perovskite solar cells. As known, the Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; solar cell performance is closely related to the light absorber layer (crystallinity, composition and bulk defect density, etc.), PN heterojunction quality (charge carrier concertation, energy band alignment and interface defect density, etc.) and back-contact barrier formation, which determines the process of carrier generation, excitation, relaxation, transfer and recombination. The low fill factor is one of the core problems that limit further efficiency improvement of Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; solar cells, which can be attributed to the high potential barrier at the back contact between the Mo electrode and Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt;absorption layer. In this work, a heat treatment is applied to the Mo electrode to generate a MoO&lt;sub&gt;2&lt;/sub&gt;buffer layer. It can be found that this buffer layer can inhibit MoSe&lt;sub&gt;2&lt;/sub&gt; film growth, exhibiting better ohmic contact with Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; and reducing the back contact barrier of the solar cell. Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; thin film is prepared by an effective combination reaction involving sputtered and selenized Sb precursor. After introducing the MoO&lt;sub&gt;2&lt;/sub&gt;buffer layer, it can also promote the formation of (hk1) (including (211), (221) and (002) etc.) preferentially oriented Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; thin films with average grain size over 1 μm. And the ratio of Sb and Se was optimized from 0.57 to 0.62, approaching the stoichiometric ratio of Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; thin film and inhibiting the formation of &lt;em&gt;V&lt;sub&gt;se&lt;/sub&gt; &lt;/em&gt;and &lt;em&gt;Sb&lt;sub&gt;Se&lt;/sub&gt;&lt;/em&gt; defects. Finally, it enhances the open-circuit voltage (&lt;em&gt;V&lt;sub&gt;OC&lt;/sub&gt;&lt;/em&gt;) of solar cells from 0.473 V to 0.502 V, short-circuit current density (&lt;em&gt;J&lt;sub&gt;SC&lt;/sub&gt;&lt;/em&gt;) from 22.71 mA/cm&lt;sup&gt;2&lt;/sup&gt; to 24.98 mA/cm&lt;sup&gt;2&lt;/sup&gt;, and fill factor (&lt;em&gt;FF&lt;/em&gt;) from 46.90% to 56.18%, establishing a promotion in power conversion efficiency (&lt;em&gt;PCE&lt;/em&gt;) from 5.04% to 7.05%. This work proposes a facile strategy for interfacial treatment and elucidates the related carrier transport enhancement mechanism, paving a bright avenue to overcome the efficiency bottleneck of Sb&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; thin film solar cells.