Se Molar Ratio Research Articles

Differential metal and metalloid contents in fresh and cooked Charu mussels (Mytella charruana) from a southeastern Brazilian estuary and associated human health risks

Sepetiba Bay, a key estuarine ecosystem in southeastern Brazil, faces significant metal inputs, with a differential pollution gradient from the bay's entrance to inner areas, raising environmental and public health concerns. This study assessed metal levels in fresh and cooked samples of highly consumed Charu mussels (Mytella charruana) from three bay areas, one near the bay entrance (P1), with higher water renewal rates, one in the northern bay area (P2) and one the eastern bay (P3), presenting lower water renewal rates. Variations in metal and metalloid concentrations across sites were observed, with P3 exhibiting higher levels in fresh mussels for most elements, except for As, which was higher at P2 (0.35 ± 0.45 mg kg−1). Cooked samples demonstrated similar trends for Cu (1.30 ± 0.39 mg kg−1), Ni (0.28 ± 0.20 mg kg−1), and V (0.75 ± 0.28 mg/kg−1), indicating that cooking in contaminanted estuary water does not significantly reduce contamination. Significant differences were detected for Ni, Cd (0.014 ± 0.008 mg kg−1), Zn (14.28 ± 2.50 mg kg−1), and V at P1, which were significantly higher than at P3. Significant Fe (246 ± 68 mg kg−1), Al (109 ± 33 mg kg−1), and Mn increases were observed from P1 to P3. Mussels sampled from P3, near an abandoned military area and urban center, exhibited high Fe and Al levels, attributed to both natural processes and industrial activities. Metal concentrations in Charu mussels often exceeded regulatory limits set by Brazilian, North American, and European agencies. Calculated Se molar ratios indicate that while Se can mitigate Hg toxicity, high Hg levels in Sepetiba Bay's Charu mussels still pose significant health risks. Similarly, high levels of Ag, Cd, and Pb suggest ineffective Se protection. However, Se appears effective against As toxicity. The Health Benefit Value of Selenium (HBVSe) indicate Se's overall protective benefits against Hg toxicity. Higher HBVSe values in cooked mussels at P1 and P2 suggest that cooking increases Se bioavailability. However, raw mussels at P3 had higher HBVSe values than cooked ones, highlighting the need for site-specific assessments. Calculated Hazard Indices indicate general high health risks from mussel consumption, and As levels in Charu mussels indicate high carcinogenic risks. These findings emphasize the need for comprehensive Charu mussel monitoring and environmental management efforts at Sepetiba Bay.

Trace element concentrations in common dolphins (Delphinus delphis) in the Celtic Seas ecoregion: Interelement relationships and effects of life history and health status

Given the increased extraction of trace elements for use by new and emerging technologies, monitoring the environmental fate and potential effects of these compounds within the aquatic environment has never been more critical. Here, hepatic trace element concentrations were assessed in a key sentinel predator, the common dolphin (Delphinus delphis), using a long-term dataset. Variation in concentrations were assessed in relation to other elements, time period, decomposition state, sex, age, total body length, sexual maturity and nutritional status, and cause of death. Additionally, mercury toxicity thresholds for evaluating risk were reviewed and employed. Concentrations of elements which bioaccumulate, THg, MeHg, Cd, and Pb, in addition to Se and V, were strongly correlated with age, and/or body length. An association was observed between Zn concentrations and disease status, with significantly higher concentrations measured in individuals that died from infectious disease, compared to other causes. Strong inter-elemental relationships were detected, namely between Hg and Se, MeHg and Se, Cd and Se, and Cu and Zn. While THg:Se molar ratio values were observed to increase with age and body length, approaching equimolarity. THg was largely comprised of inorganic Hg in older individuals, potentially bound to Se, therefore the effects from THg toxicity may possibly be less important than originally assumed. In contrast, higher MeHg:Hg ratio values were reported in juveniles, suggesting a poorer efficiency in demethylation and a higher sensitivity. The generation of data on proportions of hepatic MeHg and inorganic Hg is highly informative to both future toxicity threshold assessments within pollutant indicator assessments, and to understanding the ultimate fate of mercury in the marine web.

Composition Engineering for the Content and Distribution of Sb–O, Se, S in Antimony Sulfoselenide Thin Films Using Chemical Bath Deposition for Efficient Solar Cells

Herein, Na2SSeO3 solutions are prepared by hydrothermal method at 140 °C for 8 h using Se powder and Na2SO3 solution (the molar ratios of Se:Na2SO3 = 1:4, 1:5, 1:6) and the chemical composition of Na2SSeO3 solutions is analyzed by X‐ray photoelectron spectroscopy. Sb2S y Se3−y thin films are prepared by chemical bath deposition (CBD) at 90 °C for 5 h and subsequently annealed at 375 °C for 10 min and etched by N‐butyldithiocarbamic acid solution in DMF. The effect of the Na2SSeO3 solution, growth solution volume, etching on the thickness and chemical composition of Sb2S y Se3−y thin films, and the power conversion efficiency (PCE) of the corresponding solar cells is systematically investigated. The result reveals that the Na2SSeO3 solutions may be the mixing solutions containing Na2SSeO3, Na2S2SeO6, Na2S2Se2O6, Na2Se. When the molar ratio of Se:Na2SO3 and growth solution volume is 1:5 and 56 mL and the Sb2S y Se3−y thin films with annealing are etched, the PCE of Sb2S y Se3−y solar cells is 8.00% with spiro‐OMeTAD and 8.43% with spiro‐OMeTAD:TMT‐TTF. The PCE of 8.43% is the highest value for Sb2S y Se3−y solar cells using CBD and demonstrates that the composition engineering is an important strategy for improving the PCE of Sb2S y Se3−y solar cells using CBD.

Selenium in the liver facilitates the biodilution of mercury in the muscle of Planiliza haematocheilus in the Jiaozhou Bay, China

There are increasing evidences that the biodilution effect can significantly reduce the biomagnification of mercury (Hg) in fish. The significant antagonism of selenium (Se) -Hg may have a potential diluting effect on Hg in fish; however, there is still lack of knowledge on such effect. To reveal the Se-Hg interaction and its role in controlling the biodilution effect of Hg, we investigated levels of Hg and Se in the muscle and liver of redlip mullet from Jiaozhou Bay, China, an urbanized semi-enclosed bay highly impacted by human activities. In general, Hg levels in fish muscle were significantly negatively correlated to the levels of Se in the liver and fish size for fish with a size of < 200 mm, indicating that the antagonistic effect of Se on Hg increased with fish growth. This relationship was not significant for fish with a size of > 200 mm, possibly because the normal metabolism of Hg in muscle was hindered by homeostatic regulation or physiological activities such as gonadal development in vivo. Furthermore, the molar ratio of Se in the liver/Hg in the muscle was significantly increasing with Se/Hg in the liver, suggesting that the liver may be the key organ involved in Se-Hg antagonism. Moreover, both ratios continued to decrease with increasing fish size, implying that the antagonistic effect weakens with fish growth. These results indicate that Hg sequestration by liver may be a key mechanism of Se-Hg antagonism in fish and function as a driver for the biodilution effect of Hg, especially at a size of < 200 mm. These findings are further supported by the established linear model of Se-Hg antagonism at different developmental stages.

Relation among Mercury, Selenium, and Biomarkers of Oxidative Stress in Northern Pike (Esox lucius).

Mercury (Hg) is a toxic environmental contaminant associated with oxidative stress in freshwater fish. A known antagonist to Hg, selenium (Se), may reduce the toxic effects of Hg. In this study, the relation among Se, methylmercury (MeHg), inorganic mercury (IHg), total mercury (THg), and the expression of biomarkers of oxidative stress and metal regulation in livers of northern pike were examined. Livers from northern pike were collected from 12 lakes in Isle Royale National Park, Pictured Rocks National Lakeshore, Sleeping Bear Dunes National Lakeshore, and Voyageurs National Park. The concentrations of MeHg, THg, and Se were measured in liver tissue, and the expression of superoxide dismutase (sod), catalase (cat), glutathione s-transferase (gst), and metallothionein (mt) was assessed. There was a positive relationship between the concentrations of THg and Se, with a Hg:Se molar ratio less than one in all livers examined. There was no significant relation between sod, cat, gst, or mt expression and Hg:Se molar ratios. cat and sod expression were significantly related to increases in percent MeHg, relative to THg; however, gst and mt expression were not significantly altered. This suggests that incorporating biomarkers containing Se may be a better indicator than non-selenium-containing proteins of assessing the long-term effect of Hg and the interactions between Hg and Se in the livers of fish, such as northern pike, especially when molar concentrations of Se are greater than Hg.

Body burdens and distribution of mercury and selenium in bottlenose, striped and Risso's dolphins along the Adriatic coast: A 20-year retrospective

Top marine predators present high mercury concentrations in their tissues due to biomagnification in the marine food chain. This study reports mercury (Hg) and selenium (Se) status, and the Hg:Se molar ratio assessment in bottlenose (Tursiops truncatus), striped (Stenella coeruleoalba) and Risso's dolphins (Grampus griseus). Total Hg and Se concentrations were determined in muscle, liver, kidney, lung, spleen, adipose tissue and skin collected from 186 specimens stranded in the Croatian part of Adriatic Sea from 1995 to 2014. Total Hg concentrations in tissue samples ranged from 0.001 in the spleen to 2238 mg/kg wet weight in liver. Se concentrations in dolphin samples ranged from 0.010 to 2916 mg/kg ww. Minimum Se concentration was found in muscle and maximum Se concentration were found in liver of bottlenose dolphin. Hg and Se levels in Risso's dolphins showed higher concentrations in all tissues in comparison to bottlenose and striped dolphins. Significant and positive correlations were observed between age and Hg concentrations (P < 0.05). In 66.6 % of Risso's, 15.3 % of bottlenose dolphins and one stranded striped dolphin in this study, the hepatic concentration of Hg exceeded the higher toxic thresholds (400 mg/kg w.w.) previously defined as evidence of liver damage in marine mammals. The Hg:Se molar ratio in the liver of Risso's dolphin was 0.670. The liver of adult bottlenose dolphins showed expected values (0.870), while the liver of young dolphins had a high ratio (0.750), non-specific for the age group. The Hg:Se molar ratio in the liver of striped dolphins was 0.390, which is lower than the literature values.

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.

Facile fabrication of atom-level heterojunction 2D MoSSe nanoplates with excellent performance in photoelectrochemistry and photocatalytic levofloxacin degradation

Designing highly efficient photocatalysts for the degradation of overused levofloxacin (LEV) antibiotics is an important and challenging task. Herein, novel atom-level heterojunction 2D MoSSe nanoplates (MSS) with various S:Se molar ratios were obtained by hydrothermal synthesis . XRD studies indicated lattice constants of these MSS catalysts were intermediate between the values for MoS 2 and MoSe 2 , and their internal lattice distortion energy increased due to the interaction between the two types of lattice structures. Further analysis revealed the appearance of the internal electric fields in MSS catalysts, which appeared as the centers of the positive charge and the negative charge did not coincide. Due to the internal electric field, MSS catalysts had lower internal resistances, which were conducive to the transmission of internal carriers, and eventually enhanced the photoelectrochemical activity. The photocatalytic LEV degradation rate ( k ) of the MSS1 was 7.5 and 8.1 times superior to that of MoS 2 and MoSe 2 , respectively. The photocurrent densities of MSS1 and MSS4 were 3.5 and 18.2 times higher than that of MoS 2 . In addition, the conduction band position of MSS1 shifted to the higher than O 2 /•O 2 − and that of MoS 2 , which could generate •O 2 − for LEV degradation. Moreover, Electron Spin Resonance (ESR) analysis further revealed that the main active species in photocatalytic LEV degradation were photo-generated •O 2 – and •OH that generated from the transformation of the •O 2 − . Finally, a possible photocatalytic mechanism for LEV degradation was proposed. These results confirm the advantage of the developed ternary compound. • Novel atom-level heterojunction 2D MoSSe nanoplates with tunable S:Se molar ratio were obtained. • The photocatalytic and photoelectrochemical activity of the MoSSe is largely enhanced. • The photocurrent of the MoSSe photocatalyst has an enhancement of 17.26 times. • The photocatalytic activity of the MoSSe photocatalyst has an enhancement of 6.58 times.

Electronic transport properties of Pb(Bi1−xSbx)2(Te1−ySey)4 topological insulator

A series of Pb(Bi1−xSbx)2(Te1−ySey)4 topological insulator crystals with various Sb molar ratios x and Se molar ratios y were fabricated, and their electronic transport properties were studied. Some of the millimeter-sized samples exhibited metallic behavior, while others exhibited semiconducting behavior with a resistivity as high as 48 mΩ cm at 2 K. In addition, Hall coefficients with a large variance were observed for samples from the same ingot, indicating spatial fluctuations in the composition and/or a nonuniform defect distribution. Then, micrometer-sized samples were cut from the millimeter-sized sample with the highest resistivity, and further electrical transport measurements were performed. Some of the micrometer-sized samples exhibited an even higher resistivity than that for the millimeter-sized sample. The magnetoresistance of the semiconducting micrometer-sized samples agreed well with a three-dimensional weak antilocalization/weak localization model in the low-temperature region below 20 K.

Selenite Substituted Calcium Phosphates: Preparation, Characterization, and Cytotoxic Activity.

The aim of this study was to prepare a biomimetic selenium substituted calcium phosphate system for potential application in osteosarcoma therapy. Calcium phosphate (CaP) systems substituted with selenite ions were prepared by the wet precipitation method, using biogenic CaCO3 (derived from cuttlefish bone), CO(NH2)2-H3PO4, and Na2SeO3·5H2O as reagents. Starting reaction mixtures were prepared based on the formula for selenite-substituted hydroxyapatite, Ca10(PO4)6-x(SeO3)x(OH)2, with Ca/(P + Se) molar ratio of 1.67 and Se/(P + Se) molar ratio of: 0, 0.01, 0.05, and 0.10, respectively. The prepared CaP powders were characterized by Fourier transform infrared spectrometry, elemental analysis, scanning electron microscopy, X-ray powder diffraction analysis and Rietveld refinement studies. Phase transformation and ion release were analyzed during 7 days of incubation in simulated body fluid at 37 °C. The metabolic activity of healthy and osteosarcoma cell lines was assessed by cell cytotoxicity and viability test. The as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP). Along with the selenite substitution, the presence of Sr2+, Na+, and Mg2+ was detected as a result of using cuttlefish bone as a precursor for Ca2+ ions. Inductively coupled plasma mass spectrometry analysis showed that the Se/(P + Se) molar ratios of selenite substituted powders are lower than the nominal ratios. Heat treated powders were composed of HAp, α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). Doping CaP structure with selenite ions improves the thermal stability of HAp. The powder with the Se/(P + Se) molar ratio of 0.007 showed selective toxicity to cancer cells.

Mercury and selenium concentrations in different tissues of brown smooth-hound shark (Mustelus henlei) from the western coast of Baja California Sur, Mexico

A study on mercury (Hg) and selenium (Se) concentrations in the liver and muscle of brown smooth-hound shark Mustelus henlei and its principal prey items, was conducted in the western coast of Baja California Sur, Mexico. Average Hg concentrations were found to be high in the muscle than in the liver; however, Hg concentrations were below the maximum permissible limits, and hence, the consumption of this species does not constitute a risk to human health. The mean Se concentrations were higher in the liver than in the muscle. The results of Hg: Se molar ratio revealed that Se counteracts the toxicity of Hg in hepatic tissues, whereas the contrary occurs in the muscle. Significant differences in Hg and Se accumulation were observed between females and males. Biomagnification factor values >1 demonstrate a biomagnification process from its principal prey species (i.e., red crab, Pleuroncodes planipes and Pacific mackerel, Scomber japonicus).

ZnS/CdSe0.2S0.8/ZnSSe heterostructure as a novel and efficient photosensitizer for highly efficient quantum dot sensitized solar cells

Herein, we systematically studied the influence of ZnS, ZnSe and ZnSxSe1-x, with S:Se molar ratio of 1:4, layers as both inner and outer layers on photovoltaic properties of QDSSCs based on CdSexS1-x QDs when the molar ratio of S:Se is 4:1. The results show that ZnS and ZnS0.2Se0.8 layers are the best choice for the CdSe0.2S0.8-based QDSSCs as an inner and outer layer, respectively. Hence, we successfully designed and fabrication of QDSSCs based on ZnS/CdSe0.2S0.8/ZnS0.2Se0.8 photosensitizer with a high efficiency of 6.31%, which is almost more than double the efficiency of 3% for bare CdSe0.2S0.8-based QDSSCs. Our results indicated that in this heterostructure structure the ZnS layer acts as both a seed layer and a blocking layer, which leads to an increase in the light harvesting efficiency and a decrease in the interfacial charge recombination. On the other hand, the ZnS0.2Se0.8 layer acts as an effective passivation layer which not only reduces the charge recombination process, but also improves the light absorption range. Therefore, when both of these layers were employed in the CdSe0.2S0.8 QDSSCs, the electron lifetime and thereby the accumulation of photo-injected electrons in the TiO2 film greatly improved and reached to 104 ms and 1.21E + 18 cm3, respectively.

Elements of toxicological concern and the arsenolipids’ profile in the giant-red Mediterranean shrimp, Aristaeomorpha foliacea

The aim of this study was to determine lead, mercury, cadmium, arsenic and selenium in muscle and cephalothorax of giant red Mediterranean shrimp (Aristaeomorpha foliacea). Arsenic was also determined in the lipid fraction of the shrimp to provide an estimate of the arsenolipids. The results indicated that Pb and Cd were higher in cephalothorax than in muscle (p < 0.05), while Hg was doubled in muscle. The concentrations of Cd, Pb and Hg in the edible tissue of shrimp were under the European Union maximum levels for contaminants in foodstuffs. The molar ratio of Se:Hg was calculated to 2.4:1 and 20:1 in muscle and cephalothorax, respectively, results higher than the recommended (1:1). Arsenic concentration was one order of magnitude higher than the rest of the elements. The arsenolipids comprised 0.4 and 1.9 % of the total As in muscle and cephalothorax, respectively, whereas the rest was comprised by water soluble compounds. Analysis of the lipid extracts with High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectrometry showed the existence of several arsenolipids, with a dominant peak eluting at 2−4 min, in both muscle and cephalothorax. The Estimated Weekly Intake per meal size in both tissues for adults was calculated.

Selenium-doped hydroxyapatite nanoparticles for potential application in bone tumor therapy

In the present study we have studied the incorporation and release of selenite ions (SeO32−) in hydroxyapatite nanoparticles for the treatment of bone tumors. Two types of selenium-doped hydroxyapatite (HASe) nanoparticles (NPs) with a nominal Se/(P + Se) molar ratio ranging from 0.01 up to 0.40 have been synthesized by a new and mild wet method. The two series of samples were thoroughly characterized and resulted to be slightly different in chemical composition, but they had similar properties in terms of morphology and degree of crystallinity. Selenium release from HASe was investigated under neutral and acidic conditions to simulate both healthy tissues and the low-pH environment surrounding a tumor mass, respectively. The comparison of the release profiles at two pH values clearly showed the possibility of modulating the Se release by simply changing the amount of Se in the HASe particles. The correlation between the physicochemical properties of HASe and their dissolution as a function of pH has been also investigated to facilitate future application of the NPs as chemotherapeutic adjuvant agents. Finally, the cytotoxic activity of HASe was evaluated using prostate (PC3) and breast (MDA-MB-231) cancer cells as well as healthy human bone marrow stem cells (hBMSc). HASe NPs exerted a good cytocompatibility at low concentration of Se but, with high Se doping concentration, they displayed strong cytotoxicity.

Ionic Liquid-Based Low-Temperature Synthesis of Phase-Pure Tetradymite-Type Materials and Their Thermoelectric Properties.

Phase-pure crystalline Bi2Se3 and Bi2Te3 nanoparticles are formed in reactions of [C4C1Im]3[Bi3I12] (C4C1Im = 1-butyl-3-methylimidazolium) with [C4C1Pyr][ESiMe3] (E = Se or Te; C4C1Pyr = 1-butyl-1-methylpyrrolidinium) in the ionic liquid (IL) [C4C1Im]I. The resulting crystalline tetradymite-type nanoparticles exhibit stoichiometric Bi:E (E = Se or Te) molar ratios (2:3). Because all synthetic steps were performed under strict inert gas conditions, the surfaces of the Bi2Se3 and Bi2Te3 nanoparticles are free of metal oxide species. As proven by infrared and X-ray photoelectron spectroscopy analyses, the nanoparticle surfaces reveal only minor organic contamination from solvent residues ([C4C1Im]I). The nanomaterials show high Seebeck coefficients of -124 μV K-1 (Bi2Se3) and -155 μV K-1 (Bi2Te3) and feature high electrical conductivities (328 and 946 S cm-1, respectively) at the highest tested temperature (240 °C). The corresponding thermal conductivities (0.8 and 2.3 W m-1 K-1, respectively, at 30 °C) are comparable to those of single crystals and recently reported ab initio calculations, which is in remarkable contrast to typical findings of nanograined bulk materials obtained from compacted nanoparticles. These findings emphasize the low level of impurities, surface contamination, and, in general, defects produced by the synthetic approach reported here. The figure of merit in the in-plane direction of the compacted pellets reached peak values 0.45 for Bi2Se3 and 0.4 for Bi2Te3.

Selenium and mercury in the hair of raccoons (Procyon lotor) and European wildcats (Felis s. silvestris) from Germany and Luxembourg

This study examined the concentration of total mercury (THg) and selenium (Se), as well as the molar ratio of Se:THg in hair samples of terrestrial animals. THg and Se concentrations were measured from the hair of raccoons (Procyon lotor) and European wildcats (Felis s. silvestris) from Germany and Luxembourg. Median THg concentrations in hair from raccoons and wildcats were 0.369 and 0.273 mg kg−1 dry weight (dw), respectively. Se concentrations were higher in the hair of raccoons than of wildcats (0.851 and 0.641 mg kg−1 dw, respectively). Total mercury concentration in hair of raccoons from Luxembourg was almost 5× higher that found in hair of raccoons from Germany; however, Se concentration was similar. Thus, molar ratio of Se:THg was ~4× higher in the hair of raccoons from Germany than those from Luxembourg. Significant negative correlation was found between THg concentration and Se:THg molar ratio in both wildcats and raccoons.

Cadmium, mercury, and selenium in muscle of the scalloped hammerhead Sphyrna lewini from the tropical Eastern Pacific: Variation with age, molar ratios and human health risk.

With the aim of assessing health risk to shark consumers, cadmium, mercury, and selenium were measured in muscle of Sphyrna lewini from four coastal states (Baja California Sur, Sinaloa, Nayarit, and Colima) in western Mexico. According to length of specimens, three age modes were found: juveniles and neonates (the majority of the individuals), preadults and adults. Average concentrations (μg g-1 dry weight) in all the studied individuals followed the order cadmium (0.06), selenium (0.94), and mercury (1.56). The mean concentrations of cadmium and mercury increased significantly (p < 0.001) with mean length of specimens. Overall, hazard quotient and hazard index values were below one so there is no health risk to consumers. According to molar ratios of Hg and Se in the edible portion (muscle) of sharks, and depending on the areas of collection, individuals from Baja California Sur might not be beneficial to consumers.

Effect of S/(S+Se) ratio during the annealing process on the performance of Cu2ZnSn(S,Se)4 solar cells prepared by sputtering from a quaternary target

Cu2ZnSn(S,Se)4 (CZTSSe) has gained significant attention as a solar cell absorber material owing to its great long-time application potential. In this study, the precursors deposited by single quaternary target sputtering were annealed in different S/S + Se ratios atmosphere and CZTSSe solar cells were prepared. The mechanism of the S/Se replacement process and its effect on the composition, morphology, bandgap, and performance of the CZTSSe solar cells were systematically investigated. It was found that a decrease in the Se content in the annealing atmosphere showed an effect on the growth and properties of the thin films similar to that shown by an increase in the S/(S + Se) ratio. However, this effect was much milder than that of the increase in the S/(S + Se) ratio. The S/(S + Se) ratio of the CZTSSe thin films could be controlled by varying their S and Se contents in the annealing atmosphere and then adjusting their bandgaps. An increase in the bandgap improved the open circuit voltage and efficiency of the resulting solar cells. The cell annealed with the S:Se molar ratio of 1:3 showed an efficiency of 8.41% without anti-reflection coating.

Combined biofortification of carrot with iodine and selenium

The aim of a three-year study was to assess the effect of combined biofortification with I and Se in carrot. Four cultivars ('Askona' F1, 'Samba' F1, 'Kazan' F1 and 'White Satin') were grown in soil fertilized with KI (4 kg I ha−1) and Na2SeO4 (0.25 kg Se ha−1). The I + Se fertilization did not affect yield but the plants of all cultivars accumulated both elements in leaves and roots. On average, the I and Se contents in roots increased 7.7-times for I and 4.9-times for Se as well as the average I:Se molar ratio was 0.28:1. The contents of both elements in roots remained well below the hazard threshold thus the intake of 100 g of biofortified carrot would substantially cover the RDA for I and Se. The changes in chemical composition of roots (nitrates, phenolic compounds, sugars, carotenoids, macro-, microelements and cadmium) were rather year-dependent than affected by the applied I + Se fertilization.

Structure and electrochemical property of amorphous molybdenum selenide H2-evolving catalysts prepared by a solvothermal synthesis

Abstract Amorphous molybdenum selenide nanoparticles were synthesized by the solvothermal treatment of Mo(CO) 6 and Se in dimethylformamide. By varying the Mo(CO) 6 over Se molar ratio, we obtained a family of MoSe nanoparticles having comparable morphology but different chemical composition. Using a combination of experimental analyses ( e.g. XRD, ICP-MS, Raman, XPS) and DFT theoretical calculation, we found that the structure of MoSe was close to that of the amorphous molybdenum sulfide analogous but not that of MoSe 2 layers. The MoSe was found to consist of [Mo 3 Se 13 ] 2- cluster within its structure together with some structural defects. Thanks to its less ordered structure, the MoSe can be activated by several chemical and electrochemical treatment resulting in a catalytic enhancement. A treatment with fuming HCl resulted in generation of a novel catalyst displaying 1.4 time higher catalytic current. Remarkably, a treatment with reflux NaOH solution resulted in generation of a component being soluble in water and displaying catalytic H 2 -evolving activity at a moderate onset overpotential of ca. 200 mV, being one of the most attractives homogeneous catalysts in water.