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961.
Dr. Dong Heon Nam Dr. Jenny Z. Zhang Virgil Andrei Dr. Nikolay Kornienko Dr. Nina Heidary Andreas Wagner Kenichi Nakanishi Katarzyna P. Sokol Barnaby Slater Dr. Ingo Zebger Prof. Stephan Hofmann Dr. Juan C. Fontecilla‐Camps Prof. Chan Beum Park Prof. Erwin Reisner 《Angewandte Chemie (International ed. in English)》2018,57(33):10595-10599
Hydrogenases (H2ases) are benchmark electrocatalysts for H2 production, both in biology and (photo)catalysis in vitro. We report the tailoring of a p‐type Si photocathode for optimal loading and wiring of H2ase through the introduction of a hierarchical inverse opal (IO) TiO2 interlayer. This proton‐reducing Si|IO‐TiO2|H2ase photocathode is capable of driving overall water splitting in combination with a photoanode. We demonstrate unassisted (bias‐free) water splitting by wiring Si|IO‐TiO2|H2ase to a modified BiVO4 photoanode in a photoelectrochemical (PEC) cell during several hours of irradiation. Connecting the Si|IO‐TiO2|H2ase to a photosystem II (PSII) photoanode provides proof of concept for an engineered Z‐scheme that replaces the non‐complementary, natural light absorber photosystem I with a complementary abiotic silicon photocathode. 相似文献
962.
A Polyimide Nanolayer as a Metal‐Free and Durable Organic Electrode Toward Highly Efficient Oxygen Evolution 下载免费PDF全文
Yun‐Xiao Lin Wei‐Jie Feng Jun‐Jun Zhang Zhong‐Hua Xue Tian‐Jian Zhao Hui Su Prof. Shin‐Ichi Hirano Prof. Xin‐Hao Li Prof. Jie‐Sheng Chen 《Angewandte Chemie (International ed. in English)》2018,57(38):12563-12566
The exploitation of metal‐free organic polymers as electrodes for water splitting reactions is limited by their presumably low activity and poor stability, especially for the oxygen evolution reaction (OER) under more critical conditions. Now, the thickness of a cheap and robust polymer, poly(p‐phenylene pyromellitimide) (PPPI) was rationally engineered by an in situ polymerization method to make the metal‐free polymer available for the first time as flexible, tailorable, efficient, and ultra‐stable electrodes for water oxidation over a wide pH range. The PPPI electrode with an optimized thickness of about 200 nm provided a current density of 32.8 mA cm?2 at an overpotential of 510 mV in 0.1 mol L?1 KOH, which is even higher than that (31.5 mA cm?2) of commercial IrO2 OER catalyst. The PPPI electrodes are scalable and stable, maintaining 92 % of its activity after a 48‐h chronoamperometric stability test. 相似文献
963.
Luca Campone Anna Lisa Piccinelli Rita Celano Imma Pagano Rosa Di Sanzo Sonia Carabetta 《Natural product research》2018,32(15):1803-1808
The occurrence of aflatoxin M1 in 69 milk samples collected in a south region of Italy in 2016 was evaluated. The samples were analysed using an automated method based on online SPE coupled with UHPLC tandem mass spectrometry. After a salt induced liquid–liquid extraction with acetonitrile to remove protein from milk, the extract was diluted with water and analysed using an automated online SPE MS/MS method. Among the analysed samples no one had AFM1 higher than the legally allowable limits whereas 71.4% of the other analysed samples were above the LOD of the method. The highest contamination level of AFM1 was found in pasteurised milk (44.39 ng kg?1). The results show the worrying and widespread of AFM1 contamination, highlighting the necessity of monitoring studies in order to evaluate the reduction of the maximum legal limit. 相似文献
964.
A nitrogen doped mesoporous carbon matrix supported oxygen vacancies rich tungsten oxide composite material, WO3-x@NC (1 > x > 0), has been fabricated successfully with chitosan and H3PW12O40 as precursors through calcination. In this composite material, WO3-x particles with the size about 10–15 nm disperse evenly in nitrogen doped mesoporous carbon matrix. WO3-x@NC presents low overpotentials (η10) of 61 and 306 mV to reach a current density of 10 mA/cm2 for HER and OER in 1.0 M KOH, respectively. With WO3-x@NC as both cathode and anode at the same time, an electrolyzer, WO3-x@NC//WO3-x@NC was constructed for overall water splitting, which only needs a cell voltage of 1.60 V to achieve a current of 10 mA/cm2. During this process, WO3-x@NC//WO3-x@NC exhibits remarkable stability in 48 h. Moreover, besides HER and OER, WO3-x@NC also shows striking catalytic activity for reductive conversion of 4-nitrophenol to 4-aminophenol. Oxygen vacancies from WO3-x and good electron transportation property of nitrogen doped carbon matrix play important roles in overall water electrocatalytic splitting and 4-nitrophenol reductive removal. We expect WO3-x@NC will find its way as a new resource for hydrogen energy as well as a promising material in 4-nitrophenol removal from water. 相似文献
965.
Van der Waals Heterostructures Comprised of Ultrathin Polymer Nanosheets for Efficient Z‐Scheme Overall Water Splitting 下载免费PDF全文
Lei Wang Dr. Xusheng Zheng Liang Chen Prof. Yujie Xiong Prof. Hangxun Xu 《Angewandte Chemie (International ed. in English)》2018,57(13):3454-3458
Inspired by natural photosynthesis, Z‐scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal‐free Z‐scheme photocatalysts for overall water splitting, however, still remains challenging. The construction of polymer‐based van der Waals heterostructures as metal‐free Z‐scheme photocatalytic systems for overall water splitting is described using aza‐fused microporous polymers (CMP) and C2N ultrathin nanosheets as O2‐ and H2‐evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H2 and O2 was observed when aza‐CMP/C2N heterostructures were used. A solar‐to‐hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge‐transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting. 相似文献
966.
Hierarchical Nanoboxes Composed of Co9S8−MoS2 Nanosheets as Efficient Electrocatalysts for the Hydrogen Evolution Reaction 下载免费PDF全文
The development of hydrogen evolution catalysts based on nonprecious metals is essential for the practical application of water‐splitting devices. Herein, the synthesis of Co9S8?MoS2 hierarchical nanoboxes (HNBs) as efficient catalysts for the hydrogen evolution reaction (HER) is reported. The surface of the hollow cubic structure was organized by CoMoS4 nanosheets formed through the reaction of MoS42? and Co2+ released from the cobalt zeolite imidazole framework (ZIF‐67) templates under reflux in a mixture of water/ethanol. The formation process for the CoMoS4 HNB structures was characterized by TEM images recorded at various reaction temperatures. The amorphous CoMoS4 HNBs were converted through sequential heat treatments into CoSx?MoS2 and Co9S8?MoS2 HNBs. Owing to their unique chemical compositions and structural features, Co9S8?MoS2 HNBs have a high specific surface area (124.6 m2 g?1) and superior electrocatalytic performances for the HER. The Co9S8?MoS2 HNBs exhibit a low overpotential (η10) of 106 mV, a low Tafel slope of 51.8 mV dec?1, and long‐term stability in an acidic medium. The electrocatalytic activity of Co9S8?MoS2 HNBs is superior to that of recently reported values, and these HNBs prove to be promising candidates for the HER. 相似文献
967.
Task-specific ionic liquid dispersive liquid–liquid microextraction (TSIL-DLLME) is a simple and rapid preconcentration approach for the measurement of cadmium in serum and blood samples of human subjects. In this method a novel task-specific ionic liquid, trioctylmethyl ammonium thiosalicylate (TOMATS), which has dual characteristics as a chelating agent and extractive solvent, was investigated. TOMATS complexes with Cd due to the chelating effect of the ortho-positioned carboxylate relative to the thiol functionality. The assessment of the optimum values of variables including the pH, amount of reagents (TOMATS, diluents, Triton X114, and back extracting acid solution), temperature, and incubation time, which affect the recoveries of analyte by TSIL-DLLME method were studied. After enrichment experiments, acidic solution was used to back extract the metal ions from the ionic liquid rich phase and with determination by electrothermal atomic absorption spectrometry. Using the optimal experimental conditions, the limit of detection (3?s), precision (relative standard deviation), preconcentration, and enhancement factors of developed method for Cd were found to be 0.05?µg/L, greater than 5%, 62.5, and 52.8, respectively. To check the accuracy of the developed method, certified reference material of serum and blood were analyzed by the developed method, and the measured values of Cd were in good agreement with the certified values. The developed method was applied successfully to determine Cd in blood and serum samples of lymphatic cancer patients relative to healthy controls. 相似文献
968.
The Use of a Thin Glass-Ceramic Rod as a Surface for Sol-Gel Coating in the Preparation of SPME Fibers 总被引:4,自引:0,他引:4
A. Fernandes de Oliveira C. Berto da Silveira S. Denofre de Campos E. Antônio de Campos E. Carasek 《Chromatographia》2005,61(5-6):277-283
The efficiency of a glass-ceramic rod as a base for the preparation of SPME fibers using sol-gel technology was investigated. Glass-ceramic rod was coated with PDMS using sol-gel reaction, and its surface characteristic was determined for SEM. Optimum conditions for the preparation of the fiber are presented. The same procedure was used for coating the fused silica rod. The fibers thickness and absorption capacity were compared. The proposed fiber was used for the extraction of a mixture of BTEX, from aqueous samples. The results obtained proved the superiority of glass-ceramic as a new base for SPME fiber, resulting in a thickness of ~44 m against 6 m for fused silica base. The calibration graphs for BTEX were linear (r > 0.998) and the detection limits were below 0.8 g L–1. 相似文献
969.
A method for the determination of trace amounts of arsenic in food samples using flow injection analysis and atomic absorption spectrometry with hydride generation (FI-HG AAS) was developed. The parameters of the flow injection system and the hydride generation were optimized with respect to reagent concentrations, atomization temperature, injection volume, reaction coil length and carrier flow rate. The limits of detection and quantification were 0.34µgL–1 and 1.2µgL–:1, respectively, and the analytical curve is linear up to 30.0µgL–1 arsenic. The relative standard deviation for 12 replicates varies between 5% for 4.0µgL–1 As and 1.8% for 30.0µgL–1 As, with an injection frequency of up to 135h–1. Interferences from Ni(II), Cu(II), Fe(III), Cr(III), Mo(II), Bi(III), Se(IV), Se(VI), Sb(III) and Sb(V) could be masked with a mixture of ascorbic acid-KI in a 5.0molL–1 HCl solution. The accuracy of the proposed method was evaluated by using certified reference materials of biological samples, and the method was used to determine the content of arsenic in fish and coffee beans. 相似文献
970.
It is shown that X-ray excited KLL Auger electron spectra allow it to describe measured signal strengths similarly to X-ray photoelectron signals, thus offering valuable information on the quantitative surface composition of a solid sample. The principal equation and corresponding fundamental parameters are discussed. As a result Auger spectra of C, N, O, F, and Na can be easily used in a multiline approach for quantitative analysis. LMM and MNN spectra give rise to more problems, due to their more complicated structure, uncertainties with regard to the background and the influence of Coster-Kronig transitions. These problems are overcome by the use of empirical ratios of the strongest lines of 2p/LMM or 3d/MNN. Since these ratios are independent of sample composition, they allow it to transform the Auger signal into the corresponding photoelectron signal, provided that a standard sample has been measured. Thus a true additional information is obtained and moreover difficulties in cases of photoelectron spectra with overlapping lines from other chemical elements can be overcome.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday 相似文献