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41.
Seven-day-old sprouts of fenugreek (Trigonella foenum-graecum L.), lentil (Lens culinaris L.), and alfalfa (Medicago sativa L.) were studied. The legume seeds and then sprouts were soaked each day for 30 min during 6 days with water (control) or mixture of Fe-EDTA and sodium silicate (Optysil), or sodium silicate (Na-Sil) alone. Germination and sprout growing was carried out at temperature 20 ± 2 °C in 16/8 h (day/night) conditions. Phenolic compounds (free, ester, and glycosides) content were determined by HPLC-ESI-MS/MS using a multiple reaction monitoring of selected ions. Flavonoids and phenolic acids were released from their esters after acid hydrolysis and from glycosides by alkaline hydrolysis. The presence and high content of (−)-epicatechin (EC) in fenugreek sprouts was demonstrated for the first time. Applied elicitors decreased the level of free EC in fenugreek and alfalfa sprouts but enhanced the content of its esters. Besides, elicitors decreased the content of quercetin glycosides in lentil and fenugreek sprouts but increased the content of quercetin and apigenin glycosides in alfalfa sprouts. The applied elicitors decreased the glycoside levels of most phenolic acids in lentil and p-hydroxybenzoic acid in fenugreek, while they increased the content of this acid in alfalfa. The mixture of iron chelate and sodium silicate had less effect on changes in flavonoid and phenolic acid content in legume sprouts than silicate alone. In general, the used elicitors increased the content of total phenolic compounds in fenugreek and alfalfa sprouts and decreased the content in lentil sprouts. Among the evaluated elicitors, Optysil seems to be worth recommending due to the presence of iron chelate, which can be used to enrich sprouts with this element. 相似文献
42.
Natalia Tiessen Dr. Nico Schwarze Mira Keßler Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11041-11044
While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2F5)3]−, which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2F5)3O]−. In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2F5)3OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2F5)3SiOSi(C2F5)3. Deprotonation of Si(C2F5)3OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2F5)3O}2]2−, implies Lewis amphoteric character of the monomeric [Si(C2F5)3O]− anion. 相似文献
43.
Lucien Eisenburger Prof. Dr. Oliver Oeckler Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(13):4461-4465
Tetrahedra-based nitrides with network structures have emerged as versatile materials with a broad spectrum of properties and applications. Both nitridosilicates and nitridophosphates are well-known examples of such nitrides that upon doping with Eu2+ exhibit intriguing luminescence properties, which makes them attractive for applications. Nitridosilicates and nitridophosphates show manifold structural variability; however, no mixed nitridosilicatephosphates except SiPN3 and SiP2N4NH have been described so far. The compounds AESiP3N7 (AE=Sr, Ba) were synthesized by a high-pressure high-temperature approach using the multianvil technique (8 GPa, 1400–1700 °C) starting from the respective alkaline earth azides and the binary nitrides P3N5 and Si3N4. The latter were activated by NH4F, probably acting as a mineralizing agent. SrSiP3N7 and BaSiP3N7 were obtained as single crystals. They crystallized in the barylite-1O (M=Sr) and barylite-2O structure types (M=Ba), respectively, with P and Si being occupationally disordered. Cation disorder was further supported by solid-state NMR spectroscopy and energy-dispersive X-ray spectroscopy (EDX) mapping of BaSiP3N7 with atomic resolution. Upon doping with Eu2+, both compounds showed blue emission under UV excitation. 相似文献
44.
Timo Glaser Jannick Meinecke Lukas Freund Dr. Christian Länger Jan-Niclas Luy Prof. Dr. Ralf Tonner Prof. Dr. Ulrich Koert Prof. Dr. Michael Dürr 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(31):8082-8087
The additive-free tetrazine/enol ether click reaction was performed in ultra-high vacuum (UHV) with an enol ether group covalently linked to a silicon surface: Dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate molecules were coupled to the enol ether group of a functionalized cyclooctyne which was adsorbed on the silicon (001) surface via the strained triple bond of cyclooctyne. The reaction was observed at a substrate temperature of 380 K by means of X-ray photoelectron spectroscopy (XPS). A moderate energy barrier was deduced for this click reaction in vacuum by means of density functional theory based calculations, in good agreement with the experimental results. This UHV-compatible click reaction thus opens a new, flexible route for synthesizing covalently bound organic architectures. 相似文献
45.
Yuanyuan Yu Huihui Gao Jiadeng Zhu Dazhe Li Fengxia Wang Chunhui Jiang Tianhaoyue Zhong Shuheng Liang Mengjin Jiang 《中国化学快报》2021,32(1):203-209
Low-cost silicon microparticles(SiMP),as a substitute for nanostructured silicon,easily suffer from cracks and fractured during the electrochemical cycle.A novel n-type conductive polymer binder with excellent electronic and ionic conductivities as well as good adhesion,has been successfully designed and applied for high-performance SiMP anodes in lithium-ion batteries to address this problem.Its unique features are attributed to the stro ng electron-withdrawing oxadiazole ring structure with sulfonate polar groups.The combination of rigid and flexible components in the polymer ensures its good mechanical strength and ductility,which is beneficial to suppress the expansion and contraction of SiMP s during the charge/discharge process.By fine-tuning the monomer ratio,the conjugation and sulfonation degrees of the polymer can be precisely controlled to regulate its ionic and electronic conductivities,which has been systematically analyzed with the help of an electrochemical test method,filling in the gap on the conductivity measurement of the polymer in the doping state.The experimental results indicate that the cell with the developed n-type polymer binder and SiMP(~0.5 μm) anodes achieves much better cycling performance than traditional non-conductive binders.It has been considered that the initial capacity of the SiMP anode is controlled by the synergetic effect of ionic and electronic conductivity of the binder,and the capacity retention mainly depends on its electronic conductivity when the ionic conductivity is sufficient.It is worth noting that the fundamental research of this wo rk is also applicable to other battery systems using conductive polymers in order to achieve high energy density,broadening their practical applications. 相似文献
46.
Dr. Abdulghani Ismail Dr. Silvia Voci Lucie Descamps Dr. Arnaud Buhot Prof. Dr. Neso Sojic Dr. Loïc Leroy Dr. Aurélie Bouchet-Spinelli 《Chemphyschem》2021,22(11):1094-1100
This work depicts the original combination of electrochemiluminescence (ECL) and bipolar electrochemistry (BPE) to map in real-time the oxidation of silicon in microchannels. We fabricated model silicon-PDMS microfluidic chips, optionally containing a restriction, and monitored the evolution of the surface reactivity using ECL. BPE was used to remotely promote ECL at the silicon surface inside microfluidic channels. The effects of the fluidic design, the applied potential and the resistance of the channel (controlled by the fluidic configuration) on the silicon polarization and oxide formation were investigated. A potential difference down to 6 V was sufficient to induce ECL, which is two orders of magnitude less than in classical BPE configurations. Increasing the resistance of the channel led to an increase in the current passing through the silicon and boosted the intensity of ECL signals. Finally, the possibility of achieving electrochemical reactions at predetermined locations on the microfluidic chip was investigated using a patterning of the silicon oxide surface by etched micrometric squares. This ECL imaging approach opens exciting perspectives for the precise understanding and implementation of electrochemical functionalization on passivating materials. In addition, it may help the development and the design of fully integrated microfluidic biochips paving the way for development of original bioanalytical applications. 相似文献
47.
Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis. 相似文献
48.
Dr. Natalie Spomer Dr. Sven Holl Dr. Larissa Zherlitsyna Dr. Fariba Maysamy Andreas Frost Prof. Dr. Norbert Auner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5600-5616
Amorphous silicon is synthesized by treating the tetrahalosilanes SiX4 (X=Cl, F) with molten sodium in high boiling polar and non‐polar solvents such as diglyme or nonane to give a brown or a black solid showing different reactivities towards suitable reagents. With regards to their technical relevance, their stability towards oxygen, air, moisture, chlorine‐containing reaction partners RCl (R=H, Cl, Me) and alcohols is investigated. In particular, reactions with methanol are a versatile tool to deliver important products. Besides tetramethoxysilane formation, methanolysis of silicon releases hydrogen gas under ambient conditions and is thus suitable for a decentralized hydrogen production; competitive insertion into the MeO?H versus the Me?OH bond either yields H‐ and/or methyl‐substituted methoxy functional silanes. Moreover, compounds, such as MenSi(OMe)4?n (n=0–3) are simply accessible in more than 75 % yield from thermolysis of, for example, tetramethoxysilane over molten sodium. Based on our systematic investigations we identified reaction conditions to produce the methoxysilanes MenSi(OMe)4?n in excellent (n=0:100 %) to acceptable yields (n=1:51 %; n=2:27 %); the yield of HSi(OMe)3 is about 85 %. Thus, the methoxysilanes formed might possibly open the door for future routes to silicon‐based products. 相似文献
49.
Asymmetric Catalysis with Silicon‐Based Cuprates: Enantio‐ and Regioselective Allylic Substitution of Linear Precursors 下载免费PDF全文
Alexander Hensel Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):9062-9065
An enantio‐ and regioselective allylic silylation of linear allylic phosphates that makes use of catalytically generated cuprate‐type silicon nucleophiles is reported. The method relies on soft bis(triorganosilyl) zincs as silicon pronucleophiles that are prepared in situ from the corresponding hard lithium reagents by transmetalation with ZnCl2. With a preformed chiral N‐heterocyclic carbene–copper(I) complex as catalyst, exceedingly high enantiomeric excesses are achieved. The new method is superior to existing ones using a silicon–boron reagent as the source of the silicon nucleophile. 相似文献
50.
Rhodium‐Catalyzed Enantioselective Intramolecular CH Silylation for the Syntheses of Planar‐Chiral Metallocene Siloles 下载免费PDF全文
Dr. Qing‐Wei Zhang Kun An Li‐Chuan Liu Yuan Yue Prof. Dr. Wei He 《Angewandte Chemie (International ed. in English)》2015,54(23):6918-6921
Reported herein is the rhodium‐catalyzed enantioselective C? H bond silylation of the cyclopentadiene rings in Fe and Ru metallocenes. Thus, in the presence of (S)‐TMS‐Segphos, the reactions took place under very mild conditions to afford metallocene‐fused siloles in good to excellent yields and with ee values of up to 97 %. During this study it was observed that the steric hindrance of chiral ligands had a profound influence on the reactivity and enantioselectivity of the reaction, and might hold the key to accomplishing conventionally challenging asymmetric C? H silylations. 相似文献