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1.
J Am Chem Soc ; 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-32023049

RESUMO

The design of catalysts with high activity and robust stability for alkaline hydrogen evolution reaction (HER) remains a great challenge. Here, we report an efficient catalyst of two-dimensional bimetallene hydrides, in which H atoms stabilize the rhodium palladium bimetallene. The system exists because of the introduction of H that is in situ chemically released from the formaldehyde solution during the synthesis. This provides a highly stable catalyst based on an unstable combination of metal elements. Density functional theory calculations show the H is confined by electronic interactions and the Miedema rule of reverse stability of the RhPd alloy. The obtained catalyst exhibits outstanding alkaline HER catalytic performance with a low overpotential of 40 mV at 10 mA cm-2 and remarkable stability for over 10 h at 100 mA cm-2. The experimental results show that the confined H improve the activity, while the ultrathin sheet-like morphology yields stability. Our work provides guidance for synthesizing high-activity catalysts by confining heteroatoms into the crystal lattice of bimetallene and also a very novel mechanism for the growth of bimetallene made of highly immiscible components.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32052958

RESUMO

Heterostructures composed of superconductor and ferroelectrics (SC/FE) are very important for manipulating the superconducting property and applications. However, growth of high quality superconducting iron chalcogenide films is challenging due to their volatility and FE substrate with rough surface and large lattice mismatch. Here we report a two-step growth approach to get high quality FeSe0.5Te0.5 (FST) films on ferroelectric Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) with large lattice mismatch, which show superconductivity at only around 10 nm. Through systematic study of structural and electric transport properties of samples with different thicknesses, the mechanism is uncovered for this approach to grow high quality FST. Moreover, electric-field-induced remarkable change of Tc (superconducting transition temperature) is demonstrated in 20 nm FST film. This work paves the way to grow high quality films which contain volatile element and have large lattice mismatch with substrate. It is also helpful for manipulating the superconducting property in SC/FE heterostructures.

3.
Chem Commun (Camb) ; 56(10): 1493-1496, 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-31922159

RESUMO

This study presents the synthesis of 5,6-fused bicyclic conjugated energetic compounds through a combined strategy of anchoring the catenated nitrogen-atom chain and introducing vicinal C-amino and C-nitro groups into a tetrazolo-pyridazine ring. Their crystal structures were confirmed by single crystal X-ray diffraction. Both compounds display good thermal stability, high energetic properties and low sensitivities as energetic materials.

4.
ACS Appl Mater Interfaces ; 12(5): 6707-6715, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31927907

RESUMO

Interfaces between materials provide an intellectually rich arena for fundamental scientific discovery and device design. However, the frustration of magnetization and conductivity of perovskite oxide films under reduced dimensionality is detrimental to their device performance, preventing their active low-dimensional application. Herein, by inserting the ultrathin 4d ferromagnetic SrRuO3 layer between ferroelectric BaTiO3 layers to form a sandwich heterostructure, we observe enhanced physical properties in ultrathin SrRuO3 films, including longitudinal conductivity, Curie temperature, and saturated magnetic moment. Especially, the saturated magnetization can be enhanced to ∼3.12 µB/Ru in ultrathin BaTiO3/SrRuO3/BaTiO3 trilayers, which is beyond the theoretical limit of bulk value (2 µB/Ru). This observation is attributed to the synergistic ferroelectric proximity effect (SFPE) at upper and lower BaTiO3/SrRuO3 heterointerfaces, as revealed by the high-resolution lattice structure analysis. This SFPE in dual-ferroelectric interface cooperatively induces ferroelectric-like lattice distortions in RuO6 oxygen octahedra and subsequent spin-state crossover in SrRuO3, which in turn accounts for the observed enhanced magnetization. Besides the fundamental significance of interface-induced spin-lattice coupling, our findings also provide a viable route to the electrical control of magnetic ordering, taking a step toward low-power applications in all-oxide spintronics.

5.
J Am Chem Soc ; 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31999446

RESUMO

Defect engineering is widely applied in transition metal dichalcogenides (TMDs) to achieve electrical, optical, magnetic, and catalytic regulation. Vacancies, regarded as a type of extremely delicate defect, are acknowledged to be effective and flexible in general catalytic modulation. However, the influence of vacancy states in addition to concentration on catalysis still remains vague. Thus, via high throughput calculations, the optimized sulfur vacancy (S-vacancy) state in terms of both concentration and distribution is initially figured out among a series of MoS2 models for the hydrogen evolution reaction (HER). In order to realize it, a facile and mild H2O2 chemical etching strategy is implemented to introduce homogeneously distributed single S-vacancies onto the MoS2 nanosheet surface. By systematic tuning of the etching duration, etching temperature, and etching solution concentration, comprehensive modulation of the S-vacancy state is achieved. The optimal HER performance reaches a Tafel slope of 48 mV dec-1 and an overpotential of 131 mV at a current density of 10 mA cm-2, indicating the superiority of single S-vacancies over agglomerate S-vacancies. This is ascribed to the more effective surface electronic structure engineering as well as the boosted electrical transport properties. By bridging the gap, to some extent, between precise design from theory and practical modulation in experiments, the proposed strategy extends defect engineering to a more sophisticated level to further unlock the potential of catalytic performance enhancement.

6.
Adv Mater ; : e1906499, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31957134

RESUMO

As unique building blocks for next-generation optoelectronics, high-quality 2D p-n junctions based on semiconducting transition metal dichalcogenides (TMDs) have attracted wide interest, which are urgent to be exploited. Herein, a novel and facile electron doping of WSe2 by cetyltrimethyl ammonium bromide (CTAB) is achieved for the first time to form a high-quality intramolecular p-n junction with superior optoelectronic properties. Efficient manipulation of charge carrier type and density in TMDs via electron transfer between Br- in CTAB and TMDs is proposed theoretically by density functional theory (DFT) calculations. Compared with the intrinsic WSe2 photodetector, the switching light ratio (Ilight /Idark ) of the p-n junction device can be enhanced by 103 , and the temporal response is also dramatically improved. The device possesses a responsivity of 30 A W-1 , with a specific detectivity of over 1011 Jones. In addition, the mechanism of charge transfer in CTAB-doped 2D WSe2 and WS2 are investigated by designing high-performance field effect transistors. Besides the scientific insight into the effective manipulation of 2D materials by chemical doping, this work presents a promising applicable approach toward next-generation photoelectronic devices with high efficiency.

7.
Nat Commun ; 11(1): 132, 2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31919355

RESUMO

Exploring advanced battery materials with fast charging/discharging capability is of great significance to the development of modern electric transportation. Herein we report a powerful synergistic engineering of carbon and deficiency to construct high-quality three/two-dimensional cross-linked Ti2Nb10O29-x@C composites at primary grain level with conformal and thickness-adjustable boundary carbon. Such exquisite boundary architecture is demonstrated to be capable of regulating the mechanical stress and concentration of oxygen deficiency for desired performance. Consequently, significantly improved electronic conductivity and enlarged lithium ion diffusion path, shortened activation process and better structural stability are realized in the designed Ti2Nb10O29-x@C composites. The optimized Ti2Nb10O29-x@C composite electrode shows fast charging/discharging capability with a high capacity of 197 mA h g-1 at 20 C (∼3 min) and excellent long-term durability with 98.7% electron and Li capacity retention over 500 cycles. Most importantly, the greatest applicability of our approach has been demonstrated by various other metal oxides, with tunable morphology, structure and composition.

8.
Plant Sci ; 291: 110320, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31928664

RESUMO

Calcium-dependent protein kinases (CDPKs) are important calcium signaling components that have been shown to play crucial roles in modulating plant abiotic stress responses. However, the physiological and regulatory roles of most CDPKs are still poorly understood. Here, we report the functional characterization of PtrCDPK10 from trifoliate orange (Poncirus trifoliata (L.) Raf.) in dehydration and drought stress tolerance. PtrCDPK10, categorized in the Type III subgroup of the CDPK family, was localized to the nucleus and plasma membrane. Transcript levels of PtrCDPK10 were up-regulated by dehydration, salt and ABA treatments. Transgenic trifoliate orange plants overexpressing PtrCDPK10 showed enhanced dehydration tolerance compared with the wild type (WT), whereas VIGS (virus-induced gene silencing)-mediated knockdown of PtrCDPK10 resulted in elevated susceptibility to dehydration and drought stresses. Yeast two-hybrid screening identified several proteins that interacted with PtrCDPK10, including an ascorbate peroxidase (PtrAPX). PtrCDPK10 was shown to phosphorylate PtrAPX based on an in vitro kinase assay. PtrCDPK10-overexpressing transgenic lines exhibited higher PtrAPX mRNA abundance and APX activity and accumulated dramatically less ROS in comparison with the WT, while PtrCDPK10-silenced VIGS lines showed decreased PtrAPX expression and increased ROS level. Taken together, these results demonstrate that PtrCDPK10 promotes dehydration and drought tolerance by, at least in part, phosphorylating APX to modulate ROS homeostasis.

9.
Chem Commun (Camb) ; 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31960835

RESUMO

A core-shell hybrid of ZnO and nitrogen-doped carbon (ZnO@C:N) is designed as a long-cycling anode for LIBs. The ZnO@C:N hybrid has a high initial capacity of 1116 mA h g-1 and a reversible capacity of 608 mA h g-1 after 500 cycles at 0.1 A g-1. The unique core-shell structure, high conductivity due to nitrogen doping, and uniform solid electrolyte interphase (SEI) film formed in the electrode are revealed to result in the remarkable electrochemical performances of the ZnO@C:N electrodes.

10.
Eur Neurol ; : 1-6, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31914451

RESUMO

OBJECTIVE: To verify the efficacy and safety of dual antiplatelet therapy after intravenous thrombolysis for acute minor ischemic stroke (AMIS). METHODS: AMIS patients who received recombinant tissue plasminogen activator (rt-PA) intravenous thrombolysis from January to October 2018 were retrospectively analyzed and divided into the aspirin (ASP) and ASP + clopidogrel (ASP-CLO) groups based on the type of antiplatelet therapy to compare the rates of good clinical outcome, symptomatic intracranial hemorrhage (SICH) after thrombolysis, and mortality in 90 days. RESULTS: A total of 207 patients were included (group ASP, 105 patients; group ASP-CLO, 102 patients). There was no significant difference in the baseline clinical data between the 2 groups. The -90-day modified Rankin scale scores (66.7 vs. 82.4%, p = 0.009) showed a statistically significant difference, but SICH (1.0 vs. 1.0%, p = 0.917) and 90-day mortality (1.9 vs. 1.0%, p = 0.585) showed no significant difference between the 2 groups. CONCLUSIONS: Short-term (21 days) dual antiplatelet therapy after rt-PA intravenous thrombolysis for AMIS can improve the prognosis, reduce the risk of stroke recurrence, without increasing the risk of bleeding and mortality.

11.
Anal Chem ; 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-31941278

RESUMO

Single-atom nanozymes (SAzymes), as novel nanozymes with atomically dispersed active sites, are of great importance in the development of nanozymes for their high catalytic activities, the maximum utilization efficiency of metal atoms, and the simple model of active sites. Herein, the peroxidase-like SAzymes with high-concentration Cu sites on carbon nanosheets (Cu-N-C) were synthesized through a salt-template strategy. With the densely distributed active Cu atoms (∼5.1 wt %), the Cu-N-C SAzymes exhibit remarkable activity to mimic natural peroxidase. Integrating Cu-N-C SAzymes with natural acetylcholinesterase and choline oxidase, three-enzyme-based cascade reaction system was constructed for the colorimetric detection of acetylcholine and organophosphorus pesticides. This work not only provides a strategy to synthesize SAzymes with abundant active sites but also gives some new insights for robust nanozyme biosensing systems.

12.
J Agric Food Chem ; 68(3): 826-837, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31895558

RESUMO

A total of five strains of nicosulfuron-degrading bacteria were isolated from a continuously cultivated microbial consortium using culturomics. Among them, a novel Pseudomonas strain, LAM1902, with the highest degradation efficiency was investigated in detail. The characteristics of nicosulfuron-degradation by LAM1902 were investigated and optimized by response surface analysis. Furthermore, non-targeted metabolomic analysis of extracellular and intracellular biodegradation of nicosulfuron by LAM1902 was carried out by liquid chromatography/mass spectroscopy (LC-MS) and gas chromatography-time-of-flight/mass spectroscopy (GC-TOF/MS). It was found that nicosulfuron was degraded by LAM1902 mainly via breaking the sulfonylurea bridge, and this degradation might be attributed to oxalate accumulation. The results of GC-TOF/MS also showed that the intracellular degradation of nicosulfuron did not occur. However, nicosulfuron exerted a significant influence on the metabolism of inositol phosphate, pyrimidine, arginine/proline, glyoxylate, and dicarboxylate metabolism and streptomycin biosynthesis. The changes of myo-inositol, trehalose, and 3-aminoisobutanoic acid were proposed as a mechanism of self-protection against nicosulfuron stress.


Assuntos
Herbicidas/metabolismo , Pseudomonas/metabolismo , Piridinas/metabolismo , Compostos de Sulfonilureia/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biodegradação Ambiental , Herbicidas/química , Concentração de Íons de Hidrogênio , Metabolômica , Filogenia , Pseudomonas/classificação , Pseudomonas/genética , Pseudomonas/isolamento & purificação , Piridinas/química , Compostos de Sulfonilureia/química
13.
ACS Appl Mater Interfaces ; 12(1): 807-817, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31820911

RESUMO

Multicarbonyl polyimide derivatives were synthesized by a facial condensation polymerization of dianhydrides with a new diamine monomer containing a benzoquinone unit that was prepared according to the Michael addition reaction. The ingenious combination of dedicated carbonyl groups from the benzoquinone and dianhydride with an aniline structure linkage not only provided stable polymeric chains with a high number of carbonyl groups per unit but also guaranteed their large π-conjugated main chains, which is favorable to their long cycle life and fast kinetics. When explored as cathode materials for lithium-ion batteries, the polyimide derivatives based on naphthalic dianhydride delivered a reversible specific capacity of 145 mAh/g at 0.1 C, a high rate performance with a capacity of 108 mAh/g at 1 C, and an ultralong stable cyclic performance with a capacity retention of 80.3% after 1000 cycles at 0.5 C. Based on the theoretical calculations and the exploration of the electrochemical behaviors, sensible predictions for the reversible ion-insertion reaction of the as-prepared sample were proposed to deeply understand the charge storage mechanisms. Moreover, a stable solid electrolyte interphase film formed in the ether-based electrolyte was confirmed to improve the electrochemical properties.

14.
Angew Chem Int Ed Engl ; 59(4): 1718-1726, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31799763

RESUMO

A challenging but pressing task to design and synthesize novel, efficient, and robust pH-universal hydrogen evolution reaction (HER) electrocatalysts for scalable and sustainable hydrogen production through electrochemical water splitting. Herein, we report a facile method to prepare an efficient and robust Ru-M (M=Ni, Mn, Cu) bimetal nanoparticle and carbon quantum dot hybrid (RuM/CQDs) for pH-universal HER. The RuNi/CQDs catalysts exhibit outstanding HER performance at all pH levels. The unexpected low overpotentials of 13, 58, and 18 mV shown by RuNi/CQDs allow a current density of 10 mA cm-2 in 1 m KOH, 0.5 m H2 SO4 , and 1 m PBS, respectively, for Ru loading at 5.93 µgRu cm-2 . This performance is among the best catalytic activities reported for any platinum-free electrocatalyst. Theoretical studies reveal that Ni doping results in a moderate weakening of the hydrogen bonding energy of nearby surface Ru atoms, which plays a critical role in improving the HER activity.

15.
Plant Cell Environ ; 43(2): 400-419, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31674033

RESUMO

Plants have evolved complex mechanisms that allow them to withstand multiple environmental stresses, including biotic and abiotic stresses. Here, we investigated the interaction between herbivore exposure and salt stress of Ammopiptanthus nanus, a desert shrub. We found that jasmonic acid (JA) was involved in plant responses to both herbivore attack and salt stress, leading to an increased NaCl stress tolerance for herbivore-pretreated plants and increase in K+ /Na+ ratio in roots. Further evidence revealed the mechanism by which herbivore improved plant NaCl tolerance. Herbivore pretreatment reduced K+ efflux and increased Na+ efflux in plants subjected to long-term, short-term, or transient NaCl stress. Moreover, herbivore pretreatment promoted H+ efflux by increasing plasma membrane H+ -adenosine triphosphate (ATP)ase activity. This H+ efflux creates a transmembrane proton motive force that drives the Na+ /H+ antiporter to expel excess Na+ into the external medium. In addition, high cytosolic Ca2+ was observed in the roots of herbivore-treated plants exposed to NaCl, and this effect may be regulated by H+ -ATPase. Taken together, herbivore exposure enhances A. nanus tolerance to salt stress by activating the JA-signalling pathway, increasing plasma membrane H+ -ATPase activity, promoting cytosolic Ca2+ accumulation, and then restricting K+ leakage and reducing Na+ accumulation in the cytosol.

16.
Angew Chem Int Ed Engl ; 59(3): 1216-1219, 2020 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-31691469

RESUMO

Direct conversion of methane to value-added chemicals with high selectivity under mild conditions remains a great challenge in catalysis. Now, single chromium atoms supported on titanium dioxide nanoparticles are reported as an efficient heterogeneous catalyst for direct methane oxidation to C1 oxygenated products with H2 O2 as oxidant under mild conditions. The highest yield for C1 oxygenated products can be reached as 57.9 mol molCr -1 with selectivity of around 93 % at 50 °C for 20 h, which is significantly higher than those of most reported catalysts. The superior catalytic performance can be attributed to the synergistic effect between single Cr atoms and TiO2 support. Combining catalytic kinetics, electron paramagnetic resonance, and control experiment results, the methane conversion mechanism was proposed as a methyl radical pathway to form CH3 OH and CH3 OOH first, and then the generated CH3 OH is further oxidized to HOCH2 OOH and HCOOH.

17.
Environ Pollut ; 257: 113383, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31727419

RESUMO

Information on the occurrence and trophodynamics of per- and polyfluoroalkyl substances (PFASs) in the Antarctic region is limited. We investigated the occurrence of PFASs in an ecosystem in the Fildes Peninsula at King George Island and Ardley Island, Antarctica. The profiles, spatial distribution, and trophic transfer behavior of PFASs were further studied. ∑PFASs ranged from 0.50 ±â€¯38.0 ng/g dw (dry weight) in algae to 4.97 ±â€¯1.17 ng/g dw in Neogastropoda (Ngas), which was lower than those in the low- and mid-latitude regions and even Arctic regions. Perfluorobutyric acid (PFBA) was predominant with detection frequencies above 50% in all types of samples, and the relative contribution of PFBA ranged from 22% to 57% in the biota samples. The biomagnification factors of PFBA, perfluoroheptanoate (PFHpA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) between Archaeogastropoda (Agas) and Ngas were 0.67 ±â€¯0.54, 0.77 ±â€¯0.38, 1.04 ±â€¯1.56, 3.30 ±â€¯4.07, and 1.61 ±â€¯0.89, respectively. The trophic magnification factors of PFHxS and PFOS were 2.09 and 2.92, respectively, which indicated that they could be biomagnified through the food chain. Considering the increasing production and uncertain toxicological risks of emerging PFASs and the sensitive ecosystems in Antarctic regions, more attention should be paid, especially for the short-chain ones in the Antarctic region.

18.
Angew Chem Int Ed Engl ; 59(2): 721-724, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31622001

RESUMO

Precise control of the micro-/nanostructures of nanomaterials, such as hollow multi-shelled structures (HoMSs), has shown its great advantages in various applications. Now, the crystal structure of building blocks of HoMSs are controlled by introducing the lattice distortion in HoMSs, for the first time. The lattice distortion located at the nanoscale interface of SnS2 /SnO2 can provide additional active sites, which not only provide the catalytic activity under visible light but also improve the separation of photoexcited electron-hole pairs. Combined with the efficient light utilization, the natural advantage of HoMSs, a record catalytic activity was achieved in solid-gas system for CO2 reduction, with an excellent stability and 100 % CO selectivity without using any sensitizers or noble metals.

19.
Chemosphere ; 241: 125030, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31606000

RESUMO

Persistent organic pollutants (POPs) have been associated with a high risk of type 2 diabetes in different regions, although few studies from China have been published. We aimed to investigate the associations between POP exposure and type 2 diabetes in Chinese population. A total of 158 participants diagnosed with type 2 diabetes and 158 participants without the disorder from Shandong Province were enrolled in this case-control study during 2016-2017. Nine polychlorinated biphenyl congeners (PCBs) and 2 polybrominated diphenyl ethers with detectable levels in ≥75% of the participants were selected for data analysis. The results showed that POP exposure was significantly and positively associated with the risk of diabetes after adjusting for age, sex, BMI, triglycerides and total cholesterol. However, we did not observe an obvious modified effect of adiposity on the associations between POP exposure and diabetes in the present study, as strong associations between POPs and diabetes were observed in both the higher-BMI (BMI≥25 kg/m2) and the lower-BMI (BMI<25 kg/m2) groups. POPs showed stronger associations with diabetes in males than in females. The odds ratio (OR) for the highest quartile of ∑POPs was 6.97 for males, nearly two times higher than that for females (OR = 3.58). All these findings suggest that POP exposure may impact the risk of diabetes in Chinese population.

20.
Angew Chem Int Ed Engl ; 59(1): 232-236, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31609053

RESUMO

Traditional methods for analyzing organophosphorus pesticide chlorpyrifos, usually require the tedious sample pretreatment and sophisticated bio-interfaces, leading to the difficulty for real-time analysis. Herein, we use palladium single-atom (PdSA)/TiO2 as a photocatalytic sensing platform to directly detect chlorpyrifos with high sensitivity and selectivity. PdSA/TiO2 , prepared by an in situ photocatalytic reduction of PdCl4 2- on the TiO2 , shows much higher photocatalytic activity (10 mol g-1 h-1 ) for hydrogen evolution reaction than Pd nanoparticles (1.95 mol g-1 h-1 ), and excellent stability. In the presence of chlorpyrifos, the photocatalytic activity of PdSA/TiO2 decreases. Through this inhibition effect the platform can realize a detection limit for chlorpyrifos of 0.01 ng mL-1 , much lower than the maximum residue limit (10 ppb) permitted by the U.S. Environmental Protection Agency.

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