A flow-based iodometric extraction method for the determination of selenium sulfide was developed and applied to cosmeceutical products. Iodine which was generated from the reduction of selenium（IV） ions by iodide i...A flow-based iodometric extraction method for the determination of selenium sulfide was developed and applied to cosmeceutical products. Iodine which was generated from the reduction of selenium（IV） ions by iodide ion was on-line extracted using a polypropylene HFM （hollow fiber membrane） liquid extraction technique. The HFM extraction unit was constructed and used to support an organic solvent （hexane） and separate between the organic phase and aqueous phase. The resulting purple extract was carried to a fiber optic spectrophotometric detector for the measurement at 521 nm. Parameters which affected the extraction efficiency, sensitivity and sample throughput such as iodide （selenium molar ratio, extraction time and washing time between the cycles） were investigated and optimized. A linear dynamic range of 80-373 mg.Lt selenium solution was obtained with an extraction time of 60 sec. The total analysis time including washing was about 180 sec which provided a sample throughput of approximately 20 samples＇hr1 and excluded the sample pre-treatment. The recoveries for the determination of selenium in the forms of selenium dioxide and selenium sulfide were in the range of 103%-104% with 1%-3% RSD （relative standard deviation）. The relative errors of this method which was applied for determination of selenium sulfide levels in an anti-dandruff shampoo and a cosmeceutical bead sample were both less than 2.5%.展开更多
Selenium sulfide/double-layered hollow carbon sphere （SeS2/DLHC） composites have been designed as high-performance cathode materials for novel Li-SeS2 batteries. In the constructed composite, SeS2 is predominantly e...Selenium sulfide/double-layered hollow carbon sphere （SeS2/DLHC） composites have been designed as high-performance cathode materials for novel Li-SeS2 batteries. In the constructed composite, SeS2 is predominantly encapsulated in the interlayer space of DLHCs with a high loading of 75% （weight percentage） and serves as the active component for lithium storage. The presence of Se in the composite and the carbon framework not only alleviate the shuttling of polysulfide, but also improve the conductivity of electrodes. Migration of active materials from the interlayer void to the hollow cavity of DLHCs after cycling, which further mitigates the loss of active materials and the shuttle effect, is observed. As a result, the SeS2/DLHC composite delivers a high specific capacity （930 mA.h.g-1 at 0.2 C） and outstanding rate capability （400 mA.h.g-1 at 6 C）, which is much better than those of SeS2/single-layered hollow carbon sphere, Se/DLHC, and S/DLHC composites. Notably, the SeS2/DLHC composite shows an ultralong cycle life with 89% capacity retention over 900 cycles at 1 C, or only 0.012% capacity decay per cycle. Our study reveals that both SeS2 and the double-layered structures are responsible for the excellent electrochemical performance.展开更多
文摘A flow-based iodometric extraction method for the determination of selenium sulfide was developed and applied to cosmeceutical products. Iodine which was generated from the reduction of selenium（IV） ions by iodide ion was on-line extracted using a polypropylene HFM （hollow fiber membrane） liquid extraction technique. The HFM extraction unit was constructed and used to support an organic solvent （hexane） and separate between the organic phase and aqueous phase. The resulting purple extract was carried to a fiber optic spectrophotometric detector for the measurement at 521 nm. Parameters which affected the extraction efficiency, sensitivity and sample throughput such as iodide （selenium molar ratio, extraction time and washing time between the cycles） were investigated and optimized. A linear dynamic range of 80-373 mg.Lt selenium solution was obtained with an extraction time of 60 sec. The total analysis time including washing was about 180 sec which provided a sample throughput of approximately 20 samples＇hr1 and excluded the sample pre-treatment. The recoveries for the determination of selenium in the forms of selenium dioxide and selenium sulfide were in the range of 103%-104% with 1%-3% RSD （relative standard deviation）. The relative errors of this method which was applied for determination of selenium sulfide levels in an anti-dandruff shampoo and a cosmeceutical bead sample were both less than 2.5%.
基金The authors acknowledge the financial support from the Australian Research Council, the Queensland Government, the CAS/SAFEA International Partnership Program for Creative Research Teams, the Australian National Fabrication Facility and the Australian Microscopy and Microanalysis Research Facility at the Centre for Microscopy and Microanalysis, The University of Queensland. L. Z. acknowledges the financial support from the National Natural Science Foundation of China （No. 51502226）.
文摘Selenium sulfide/double-layered hollow carbon sphere （SeS2/DLHC） composites have been designed as high-performance cathode materials for novel Li-SeS2 batteries. In the constructed composite, SeS2 is predominantly encapsulated in the interlayer space of DLHCs with a high loading of 75% （weight percentage） and serves as the active component for lithium storage. The presence of Se in the composite and the carbon framework not only alleviate the shuttling of polysulfide, but also improve the conductivity of electrodes. Migration of active materials from the interlayer void to the hollow cavity of DLHCs after cycling, which further mitigates the loss of active materials and the shuttle effect, is observed. As a result, the SeS2/DLHC composite delivers a high specific capacity （930 mA.h.g-1 at 0.2 C） and outstanding rate capability （400 mA.h.g-1 at 6 C）, which is much better than those of SeS2/single-layered hollow carbon sphere, Se/DLHC, and S/DLHC composites. Notably, the SeS2/DLHC composite shows an ultralong cycle life with 89% capacity retention over 900 cycles at 1 C, or only 0.012% capacity decay per cycle. Our study reveals that both SeS2 and the double-layered structures are responsible for the excellent electrochemical performance.
