Amounts Of Selenium Research Articles

In-situ fabrication and performance optimization of CIGS thin film deposited by ion-beam sputtering without post-selenization

Cu(In, Ga)Se2 thin films were fabricated by an in situ fabrication process of ion beam sputtering deposition without post-selenization. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and four-point probe technique were used to study the microstructures, surface morphology, composition and electrical properties, respectively. The results show that the films grown above 400 °C are of chalcopyrite structure and Cu (In0.7Ga0.3) Se2 thin film was obtained at annealing temperature of 550 °C. With the increase in annealing temperature, the resistivity of the films decreases while the component is nearly steady. The degree of crystallization of the thin films increased at first with increasing of the annealing time and then decreased with the annealing time increasing further. It was demonstrated that the structural and electrical properties of the films improved significantly with adding selenium amount by sputtering selenium.

Influence of the species effect on trueness of analytical results estimated by the recovery test when determining selenium by HG-AFS

The recovery test in the "surrogate" mode is often exploited for trueness assessment when appropriate certified reference materials are not available or to support reference material studies. The species effect occurs when chemical forms of native and surrogate analytes are different. It usually results in obtaining incomparable analytical signals for both forms. Influence of the species effect on the results obtained by "surrogate" recovery test was examined. The examination was performed theoretically on the basis of a extended mathematical model and the results predicted by the model were checked experimentally. Experiments were carried out with the use of synthetic samples containing selenite ions and l-selenomethionine acting as inorganic and organic form of selenium, respectively. Moreover, real samples of thermal spring water and vitamin drink were analysed with the use of flow injection system. The system was dedicated to perform not only spiking but also UV digestion of the synthetic and real samples in order to study the species effect. The system was coupled to hydride generation atomic fluorescence spectrometer (HG-AFS) enabling to determine total amount of selenium.

Indirect spectrophotometric determination of ultra trace amounts of selenium based on dispersive liquid–liquid microextraction–solidified floating organic drop

A novel dispersive liquid–liquid microextraction–solidified floating organic drop (DLLME–SFOD) method combined with fiber optic-linear array detection spectrophotometry has been developed for the indirect determination of selenium. The method is based on the oxidation of the I− to iodine by inorganic Se(IV). The produced I2 reacts with the excess of I− ions in acidic media to give triiodide ions. The I3- is then extracted into 1-undecanol by DLLME–SFOD upon the formation of an ion pair with cetyltrimethylammonium cation. The extracted ion pair is determined by measuring its absorption at 360nm. The absorbance signal is proportional to the selenium concentration in the aqueous phase. Under optimum conditions, the method provided an enrichment factor of 250 with a detection limit of 16.0μgL−1 and a linear dynamic range of 40.0–1000.0μgL−1. The relative standard deviation was found to be 2.1% (n=7) at 100.0μgL−1 concentration level. The method was successfully applied to the determination of selenium in water samples and selenium plus tablet.

Method for the Determination of Total Selenium in a Wide Variety of Foods Using Inductively Coupled Plasma/Mass Spectrometry

An optimized method for use in a high volume laboratory was developed and validated for the determination of total selenium in a wide variety of food products including infant formula. The method utilizes a single-stage, closed-vessel microwave digestion procedure with nitric acid. Upon completion of digestion, the solution is brought to volume with water. A dilution is prepared for analysis by adding methanol (MeOH) to an aliquot and then brought to volume by nitric acid diluent resulting in a 3% MeOH concentration. The amount of selenium is determined by inductively coupled plasma (ICP)/MS with the capability of removing argon-based polyatomic interferences. Experiments were conducted to validate the method by determining precision, accuracy, linearity, specificity, ruggedness, and robustness. The calculated practical reporting level for this method was 25.0 microg/kg. The method provided an average RSD of 2.03% during analysis of a wheat flour reference material and 2.73% during analysis of a powdered infant formula. The accuracy of the method for these materials was 98.6 and 105%, respectively. The method has also been used successfully on a variety of foods from various categories including fruits, grains, vegetables, protein, and dairy.

A Turn-on Fluorescent Nanoprobe for Selective Determination of Selenium(IV)

A turn-on fluorescent nanoprobe was developed for selective determination of selenium(IV). A trace amount of selenium, as an essential nutrient, plays an important role in human health. It has been proven that a selenium deficiency will result in serious health problems. The developed nanoprobe is capable of in situ detection of selenium with target-induced signaling, and no separation step is needed. The nanoprobe consists of a silica nanoparticle core and a coating layer containing selenium(IV)-induced fluorescent molecules, 3,3'-diaminobenzidine (DAB). The nanoprobes have no fluorescence signals if they are not exposed to selenium(IV). However, the nanoprobes will be "turned on", with fluorescence, when they bind to the targets of selenium(IV). With this strategy, the selenium(IV) are first collected and enriched on a small domain of the nanoprobes. Then, with an excitation at 420 nm, the nanoprobes emit fluorescence signals at 530 nm. The fluorescence intensity is proportional to the selenium concentration. A fluorescence microscope was used to monitor the process of enriching and collecting of the selenium(IV) by the nanoprobes. The optimal conditions for the determination of selenium(IV) using the nanoprobe were investigated including pH, solvent, and linear range. The interference from common metal ions was studied as well. This study is expected to shed light on how to design turn-on fluorescent nanoprobes for in situ monitoring of a wide variety of targets in biological processes.

Selenium and mercury molar ratios in commercial fish from New Jersey and Illinois: variation within species and relevance to risk communication.

There is an emerging consensus that people consuming large amounts of fish with selenium:mercury ratios below 1 are at higher risk from mercury toxicity. As the relative amount of selenium increases compared to mercury, risk may be lowered, but it is unclear how much excess selenium is required. It would be useful if the selenium:mercury ratio was relatively consistent within a species, but this has not been the case in our studies of wild-caught fish. Since most people in developed countries and urban areas obtain their fish and other seafood commercially, we examined selenium:mercury molar ratios in commercial fish purchased in stores and fish markets in central New Jersey and Chicago. There was substantial interspecific and intraspecific variation in molar ratios. Across species the selenium:mercury molar ratio decreased with increasing mean mercury levels, but selenium variation also contributed to the ratio. Few samples had selenium:mercury molar ratios below 1, but there was a wide range in ratios, complicating the interpretation for use in risk management and communication. Before ratios can be used in risk management, more information is needed on mercury:selenium interactions and mutual bioavailability, and on the relationship between molar ratios and health outcomes. Further, people who are selenium deficient may be more at risk from mercury toxicity than others.

Selenium Content in Seafood in Japan

Selenium is an essential micronutrient for humans, and seafood is one of the major selenium sources, as well as red meat, grains, eggs, chicken, liver and garlic. A substantial proportion of the total amount of selenium is present as selenium containing imidazole compound, selenoneine, in the muscles of ocean fish. In order to characterize the selenium content in seafood, the total selenium levels were measured in the edible portions of commercially important fish and shellfish species. Among the tested edible portions, alfonsino muscle had the highest selenium levels (concentration of 1.27 mg/kg tissue). High levels of selenium (1.20–1.07 mg/kg) were also found in the salted ovary products of mullet and Pacific herring. In other fish muscles, the selenium levels ranged between 0.12 and 0.77 mg/kg tissue. The selenium levels were closely correlated with the mercury levels in the white and red muscles in alfonsino. The selenium content in spleen, blood, hepatopancreas, heart, red muscle, white muscle, brain, ovary and testis ranged between 1.10 and 24.8 mg/kg tissue in alfonsino.

Engineered CuInSexS2-x Quantum Dots for Sensitized Solar Cells.

Colloidal CuInSexS2-x quantum dots (QDs) are an attractive less-toxic alternative to PbX and CdX (X = S, Se, and Te) QDs for solution-processed semiconductor devices. This relatively new class of QD materials is particularly suited to serving as an absorber in photovoltaics, owing to its high absorption coefficient and near-optimal and finely tunable band gap. Here, we engineer CuInSexS2-x QD sensitizers for enhanced performance of QD-sensitized TiO2 solar cells (QDSSCs). Our QD synthesis employs 1-dodecanethiol (DDT) as a low-cost solvent, which also serves as a ligand, and a sulfur precursor; addition of triakylphosphine selenide leads to incorporation of controlled amounts of selenium, reducing the band gap compared to that of pure CuInS2 QDs. This enables significantly higher photocurrent in the near-infrared (IR) region of the solar spectrum without sacrificing photovoltage. In order to passivate QD surface recombination centers, we perform a surface-cation exchange with Cd prior to sensitization, which enhances chemical stability and leads to a further increase in photocurrent. We use the synthesized QDs to demonstrate proof-of-concept QDSSCs with up to 3.5% power conversion efficiency.

Selenium and the thyroid gland: more good news for clinicians

The thyroid is the organ with the highest selenium content per gram of tissue because it expresses specific selenoproteins. Since the discovery of myxoedematous cretinism and thyroid destruction following selenium repletion in iodine- and selenium-deficient children, data on links between thyroid metabolism and selenium have multiplied. Although very minor amounts of selenium appear sufficient for adequate activity of deiodinases, thus limiting the impact of its potential deficiency on synthesis of thyroid hormones, selenium status appears to have an impact on the development of thyroid pathologies. The value of selenium supplementation in autoimmune thyroid disorders has been emphasized. Most authors attribute the effect of supplementation on the immune system to the regulation of the production of reactive oxygen species and their metabolites. In patients with Hashimoto's disease and in pregnant women with anti-TPO antibodies, selenium supplementation decreases anti-thyroid antibody levels and improves the ultrasound structure of the thyroid gland. Although clinical applications still need to be defined for Hashimoto's disease, they are very interesting for pregnant women given that supplementation significantly decreases the percentage of postpartum thyroiditis and definitive hypothyroidism. In Graves' disease, selenium supplementation results in euthyroidism being achieved more rapidly and appears to have a beneficial effect on mild inflammatory orbitopathy. A risk of diabetes has been reported following long-term selenium supplementation, but few data are available on the side effects associated with such supplementation and further studies are required.

Introducing Antibacterial Properties to Paper Towels Through the Use of Selenium Nanoparticles

ABSTRACTBacterial infections are commonly found on paper towels and other paper products leading to the potential spread of bacteria and consequent health concerns. The objective of this in vitro study was to introduce antibacterial properties to paper towel surfaces by coating them with selenium nanoparticles. Scanning electron microscopy was used to measure the size and distribution of the selenium coatings on the paper towels. Atomic force microscopy was used to measure the surface roughness of paper towels before and after coated with selenium nanoparticles. The amount of selenium precipitated on the paper towels was measured by atomic absorption spectroscopy. In vitro bacterial studies with Staphylococcus aureus were conducted to assess the effectiveness of the selenium coating at inhibiting bacterial growth. Results showed that the selenium nanoparticles coated on the paper towel surface were well distributed and semispherical about 50nm in diameter. Most importantly, the selenium nanoparticle coated paper towels inhibited S. aureus growth by 90% after 24 hours and 72 hours compared with the uncoated paper towels. Thus, the study showed that nano-selenium coated paper towels may lead to an increased eradication of bacteria to more effectively clean a wide-range of clinical environments, thus, improving health.

The relationship of selenium tolerance and speciation in Lecythidaceae species

Comparative study of selenium (Se) speciation in hyperaccumulator plants offers an interesting challenge from the analytical point of view. In our study the application of a sophisticated sample clean-up procedure and the combination of elemental and molecular mass spectrometric methods led to the identification of several new selenocompounds. The difference between the Se speciation of the primary accumulator Lecythis minor and the secondary accumulator Bertholletia excelsa confirmed the current opinion that the speciation pattern in hyperaccumulator plants is principally related to the mechanism of accumulation and not to taxonomy. The most abundant new selenocompounds were found to be the derivatives of selenohomocysteine (SeHCy) and selenomethionine (SeMet), including fatty acid metabolism related compounds. A series of SeHCy derived species containing multiple Se atoms (>2) was also detected and their structures were validated by the synthesis of their S-Se analogues.

Thermoelectric bulk glasses based on the Cu–As–Te–Se system

Stable bulk glasses from the quaternary system Cu–As–Te–Se are investigated for thermoelectric applications. These materials exhibit a low thermal conductivity κ ∼ 0.3 W K−1 m−1 which is appealing for raising the thermoelectric figure of merit ZT. The addition of small amounts of selenium within the telluride amorphous matrix plays two fundamental roles. First, the increased disorder associated with the size mismatch improves glass-formation and widens the glass-formation domain, and second, it increases phonon scattering and slightly decreases the thermal conductivity. Furthermore, the addition of copper up to 32% dramatically increases the electrical conductivity without notably affecting the thermal conductivity. This permits us to obtain bulk glass samples with promising thermoelectric properties, which could be manufactured through conventional low-cost glass casting methods. While addition of copper permits the increase of electrical conductivity by more than six orders of magnitude, another three orders of magnitude are required to obtain thermoelectric materials with competitive ZT. Nevertheless, predicted values of ZT > 1.2 are estimated which would constitute some of the highest reported figure of merit for a bulk solid at room temperature. The effect of glass annealing on thermoelectric properties is also discussed.

Influence of inorganic and organic selenium on number of living mycelial cells and their ultrastructure in culture ofHericium erinaceum(Bull.: Fr. Pers.)

Mycelium of the white-rot fungus (Hericium erinaceum (Bull.: Fr. Pers.) produces polysaccharides showing anticancer and immunostimulating activity. In our previous works, we have shown that organic selenitetriglycerides (Selol) contribute to the increase of biosynthesis of exopolysaccharides (EPS) having antioxidative properties and containing large amounts of selenium. The present work is a study of influence of inorganic and organic form of selenium on viability of H. erinaceum mycelium and on ultrastructural changes taking place during its development in submerged culture. The mycelium was grown on media containing sodium selenite (Na2SeO3), a mixture of Na2SeO3 + Selol2% and on control medium (no selenium added). It was shown that mycelium cultured for 3 days in control conditions on standard media contained almost 100% of living cells, with over 80% after 24 days. Treatment with 100 ppm of Na2SeO3 lowered the number of viable cells to 11.8% and 9.1% after 3 and 24 days, respectively. The addition of 2% Selol caused the amounts of living cells to remain at ca 90%. Apparently, Selol helped the cells to cope with the toxic activity of inorganic selenium ions. The addition of sodium selenite induced degradative changes in cell organelles. Such changes were not observed in the case of Na2SeO3 + Selol mixture, in which case cells contained numerous ribosomes and small lipid bodies.

Short communication: inhibiting biofilm formation on paper towels through the use of selenium nanoparticles coatings

Bacterial infections are commonly found on paper towels and other paper products, leading to the potential spread of bacteria and consequent health concerns. The objective of this in vitro study was to introduce antibacterial properties to standard paper towel surfaces by coating them with selenium nanoparticles. Scanning electron microscopy was used to measure the size and distribution of the selenium coatings on the paper towels. Atomic force microscopy was used to measure the surface roughness of paper towels before and after they were coated with selenium nanoparticles. The amount of selenium precipitated on the paper towels was measured by atomic absorption spectroscopy. In vitro bacterial studies with Staphylococcus aureus were conducted to assess the effectiveness of the selenium coating at inhibiting bacterial growth. Results showed that the selenium nanoparticles coated on the paper towel surface were well distributed with semispherical geometries about 50 nm in diameter. Most importantly, the selenium nanoparticle-coated paper towels inhibited S. aureus growth by 90% after 24 and 72 hours compared with the uncoated paper towels. Thus, the study showed that nanoparticle selenium-coated paper towels may lead to an increased eradication of bacteria in a wider range of clinical environments and in the food industry, thus improving human health.

Dispersive Liquid-Liquid Microextraction-Solidified Floating Organic Drop Combined with Spectrophotometry for the Speciation and Determination of Ultratrace Amounts of Selenium

In this study a simple and inexpensive dispersive liquid-liquid microextraction-solidified floating organic drop (DLLME-SFOD) has been reported for the separation and speciation of inorganic selenium prior to its spectrophotometric determination. The method is based on the formation of a yellow piazselenol complex between the Se(IV) and 3,3'-diaminobenzidine (DAB) followed by its extraction into 1-undecanol and the measurement of its absorption at 434 nm. Total inorganic selenium is determined after the reduction of Se(VI) to Se(IV). The concentration of Se(VI) is calculated by the difference between the total selenium and Se(IV). Under the optimized conditions, an enrichment factor of 133, a detection limit of 1.6µg L-1, a relative standard deviation of 2.1% at 50.0µg L-1 (n = 6) and a linear dynamic range of 5.0-600.0µg L-1 for the preconcentration of 20.0 mL of aqueous sample was obtained. The method was successfully applied to the determination of selenium in garlic, selenium plus tablet and water samples. The accuracy was evaluated through the recovery experiments and the analysis of a certified water sample.

Potential Enrichment of Medicinal Mushrooms with Selenium to Obtain New Dietary Supplements

The purpose of this study was to resolve the question of whether various selenium concentrations affect the ability of eight species, members of five genera, to produce mycelium biomass and absorb this trace element during submerged cultivation in Na2SeO3-enriched medium. The obtained results demonstrated the ability of mycelia of all of the tested species to absorb selenium at analyzed concentrations. Thus, selenium content ranged from 1.4 µg g-1 (Pleurotus eryngii) to 20.3 µg g-1 (Pleurotus ostreatus). The potential of mycelia to absorb selenium was significant, ranging from 8.1% (Lenzites betulinus) to 62.5% (P ostreatus) of its content in the medium. It may be concluded that all tested mushroom species could be used as satisfactory selenium sources due to the fact that the absorbed concentrations ranged from 15.8% (P. eryngii) to 36.9% (P. ostreatus) of the dietary selenium amount (55 µg d-1) recommended by the European Scientific Committee on Food.

Development of a novel antidiabetic zinc complex with an organoselenium ligand at the lowest dosage in KK-Ay mice

Diabetes mellitus (DM) is a considerably diagnosed metabolic disease and a serious problem worldwide. We prepared various zinc complexes and studied their potential for use as new antidiabetic agents. In this study, we synthesized a seleniferous zinc complex, di(2-selenopyridine-N-oxidato)zinc(II) ([ZPS]) that has a Zn(Se2O2) coordination mode. Analyses of structure-activity relationships between its insulin-like activity and the coordination mode of [ZPS]-related complexes showed that it had high insulin-like activity. Hypoglycemic effects of [ZPS] on type 2 diabetic KK-Ay mice were exerted at the lowest dose administered (1.25–2.5mg Zn/kg body weight), unlike previously synthesized zinc complexes. Furthermore, [ZPS] afforded us a new advantage; we were able to investigate the tissue distribution of the ligand by measuring the amount of selenium in the organs of [ZPS]-treated mice. Gastrointestinal absorption and tissue penetration of zinc derived from [ZPS] in ddY mice, which was monitored using an isotope tracer technique, was significantly increased compared to that of ZnCl2. These results suggest that [ZPS] has superior antidiabetic effects compared to previously reported zinc complexes, and is thus a potential novel antidiabetic agent that facilitates the possibility of organoselenium ligands as new metal delivery systems for treating DM.

Preparation and characterization of polypyrrole/selenium composites

AbstractThis article reports synthesis of polypyrrole (PPy) and its composites having various amounts of selenium (Se) in the presence of nitric acid in aqueous medium via chemical oxidative polymerization. Samples were spectroscopically characterized using Fourier transform infrared spectroscopy, ultraviolet‐visible spectroscopy, and atomic absorption spectroscopy. Although morphology of the samples was examined by using scanning electron microscopy (SEM), their thermal properties were studied via differential scanning calorimetry (DSC). The alternating current (ac) conductivity and dielectric properties were investigated as a function of temperature. Variation of adsorption free energy obtained from Langmuir adsorption isotherm showed that metal cations were physically adsorbed onto the polymer surface. SEM images showed that filling process significantly changes the morphology of PPy. DSC results indicated that cold crystallization temperature (Tcc) of unfilled PPy decreases with increasing filling level. Dielectric measurements showed that relaxation times for PPy and its composites have decreased linearly with increasing temperature. The conductivity of the PPy, when filled with 1 g of Se, increased ∼ four times at room temperature for 1 kHz. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Selenium modified Te85Ge15 films elaborated by thermal co-evaporation for infrared applications

With the final objective to manufacture micro-sensors for CO2 detection, one of the major issues in the fabrication of infrared channel waveguides, which is the deposition of a core layer with controlled optical properties, was investigated. The paper reports on the effect of introduction of increasing amount of selenium in Te85Ge15 films. The possibility of tuning the optical properties, i.e. transmission domain and refractive index, principally, was demonstrated. 5μm-thick Te–Ge–Se amorphous films were deposited by thermal co-evaporation, and deposition conditions were chosen in such a way that a constant content in Ge, fixed at 15at.%, was obtained. The homogeneity as well as the morphological, thermal and optical properties of the as-obtained nominal Te85−xGe15Sex films were studied. The homogeneity in thickness and composition was very good on a region of about 4cm in diameter. The vitreous transition temperature lies between 137°C and 145°C depending upon the film composition, and the thermal analysis curves of the films containing more than 60% of selenium did not show any crystallization peak. As expected, the replacement of tellurium by selenium in the films led to a displacement of the optical band gap to the near-infrared and a decrease in the film refractive index. To end, the Se-rich Te–Ge–Se thermal co-evaporated films were shown to be suitable for the fabrication of channel waveguides being operational at 4.2μm and between 13 and 16μm, opening the door to the fabrication of micro-sensors for CO2 detection.

In vitro metabolism of diphenyl diselenide in rat liver fractions. Conjugation with GSH and binding to thiol groups

In spite of an extensive literature reporting pharmacological properties of diphenyl diselenide, (PhSe)2, little is known about its metabolism. The aim of this study was to identify possible metabolic pathways of (PhSe)2in vitro to get insights into the mechanism of its toxicity. Rat liver preparations, namely total homogenate, S9 fraction, cytosol and microsomes were used in the incubations. Samples were analyzed using liquid chromatography–tandem mass spectrometry (LC–MS/MS), high-performance liquid chromatography (HPLC) or inductively coupled plasma (ICP). A reduced glutathione (GSH)-selenol adduct (m/z 462) was identified in all liver fraction incubations by LC–MS/MS, suggesting a reaction between (PhSe)2 and GSH in tissues. Results from incubation of (PhSe)2 with microsomal fraction showed that (PhSe)2 disappears from the supernatant without formation of phase I metabolites. The addition of exogenous GSH maintained constant (PhSe)2 levels in supernatant and significantly reduced the amount of selenium in the precipitate obtained when microsomal incubations were treated with methanol. Addition of N-acetylcysteine (NAC) had a similar effect; moreover, a NAC-selenol adduct similar to the GSH-selenol adduct was identified by LC–MS/MS (m/z 318) in the NAC incubations. The data indicates that (PhSe)2 probably binds covalently to microsomal components and that GSH and NAC can prevent binding. The depletion of GSH levels in vitro may be related to (PhSe)2 toxicity. The inhibition of cytochrome P450 (CYP) activity by carbon monoxide or proadifen did not change the amount of (PhSe)2 in supernatant and selenium levels in the precipitate, neither did the inactivation of the microsomes by heat indicating that binding was not mediated by cytochrome P450 metabolism and was probably due to a direct reaction between (PhSe)2 and microsomal components. Due to the covalent binding of (PhSe)2 to microsomal components the potential of (PhSe)2 to inhibit cytochrome P450 was examined. (PhSe)2 at a concentration as low as 1μM reduced monooxygenase activity with an IC50 value of 78μM.