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Lettuce is a common vegetable in hydroponic production. In this paper, a selenium (Se)-biofortification method was provided. The Se content, speciation, and the effects of different concentrations of selenate and selenite on lettuce growth and amino acids were investigated. The results showed that lettuce had strong ability to accumulate exogenous selenium, and inorganic Se could be effectively converted into organic Se. The proportion of organic Se in the shoots under treatment with 4 μmol L−1 selenite was 100%. Selenomethionine was the main organic Se, accounting for 51% (selenate) and 90% (selenite) of the total Se. Adding Se improves photosynthesis of lettuce and promotes growth. The growth with 2 μmol L−1 selenate and 4 μmol L−1 selenite was better than CK, and the shoot fresh weight was increased by 143.22% and 166.98%, respectively. Furthermore, the optimum Se application is 2 μmol L−1, and some areas can apply 4 μmol L−1 selenite. But Se-excessive areas are not recommended to grow selenium-rich foods. Therefore, lettuce has strong biofortification potential. • Selenomethionine is the predominant selenium speciation in Se-biofortified. • No potential risk was found with apply low concentrations of exogenous selenium. • Selenite is safer and more effective for selenium supplementation. • Se-biofortified lettuce may be a suitable selenium supplement for increasing Se intake human. [ABSTRACT FROM AUTHOR]

We report on a simple and fast route to prepare lithium selenide (Li 2 Se) nanoparticles and show a versatile solution-based method to form uniform nanostructured carbon (C)-Li 2 Se composites with and without additional carbon shell. We systematically compare electrochemical performance characteristics of 50–100 nm high purity Li 2 Se nanoparticles with that of the C-Li 2 Se nanocomposites for rechargeable Li battery applications. While Li 2 Se nanopowder show high initial capacity, it suffers from active material loss and shuttle of dissolved polyselenides, resulting in low cycling stability and resistance growth, additionally aggravated by mechanical cathode degradation induced by repetitive volume changes during cycling. By embedding Li 2 Se nanoparticles into a conductive carbon matrix, mechanical stability of electrodes was greatly enhanced. More importantly, the dissolution and shuttle of polyselenides was suppressed significantly even for smaller (~20 nm) and thus more reactive Li 2 Se nanoparticles. As a result, C-Li 2 Se nanocomposite cathodes showed high rate capability and promising cycling stability with carbon-shell protected C-Li 2 Se showing virtually no degradation in 100 cycles. When compared with somewhat similar lithium sulfide (Li 2 S) nanoparticles and C-Li 2 S electrodes, we observe lower over-potential at different C-rates in case of Li 2 Se and C-Li 2 Se materials, which is advantageous for battery applications. Based on the postmortem analysis, significant Li dendrite growth observed in Li 2 Se/Li cells did not take place in C-Li 2 Se/Li and C-Li 2 Se@C/Li cells, suggesting that polyselenide shuttle may affect Li plating morphology. Beyond the organic electrolyte-based Li-Se batteries, all-solid Li-Se batteries based on the produced C-Li 2 Se nanocomposite cathode were built for the first time using conventional Li 2 S-P 2 S 5 solid state electrolyte. These solid state cells showed very promising cycling stability, a single flat plateau and very small voltage hysteresis in the range of 0.1–0.4 V when tested at 60 and 80 °C. [ABSTRACT FROM AUTHOR]

Abstract: This study emphasizes optimization of Fe2O3 and Fe3O4 nanowire conversion electrodes by directly-growing them on current collectors, preparing them as single crystals, and coating their surfaces with conductive carbon coatings. The systems with the least polarization during Li-ion cycling are then tested as electrodes for Na-ion chemistry. Precipitation of nanograined material during the first cycle reduces the polarization associated with Li insertion upon subsequent cycles. After the first cycle, delithiation primarily contributes to polarization associated with the conversion reaction with lithiation occurring close to the equilibrium potential. The initial reduction reaction does not proceed to completion for Na chemistries. Electron microscopy reveals significant Na insertion that occurs along with the formation of defect networks. However, the results indicate that an insufficient amount is present to form critical nuclei necessary to induce the conversion reaction. [Copyright &y& Elsevier]