Surface modulation at the atomic level is an important approach for tuning surface chemistry and boosting the catalytic performance. Here, a surface modulation strategy is demonstrated through the ...decoration of isolated Ni atoms onto the basal plane of hierarchical MoS2 nanosheets supported on multichannel carbon nanofibers for boosted hydrogen evolution activity. X‐ray absorption fine structure investigation and density functional theory (DFT) calculation reveal that the MoS2 surface decorated with isolated Ni atoms displays highly strengthened H binding. Benefiting from the unique tubular structure and basal plane modulation, the newly developed MoS2 catalyst exhibits excellent hydrogen evolution activity and stability. This single‐atom modification strategy opens up new avenues for tuning the intrinsic catalytic activity toward electrocatalytic water splitting and other energy‐related processes.
Surface modulation at the atomic level has been an important approach for boosting the performance of electrocatalysts. Here, a combined theoretical and experimental study on Ni atom decorated hierarchical MoS2 nanosheets supported on a multichannel carbon matrix (MCM) is presented. The obtained hybrid MCM@MoS2–Ni electrocatalyst with activated S sites exhibits high performance in electrocatalytic hydrogen evolution.
Heterointerface engineering can be used to develop excellent catalysts through electronic coupling effects between different components or phases. As one kind of promising Pt‐free electrocatalysts ...for hydrogen evolution reaction (HER), pure‐phased metal phosphide exhibits the unfavorable factor of strong or weak H*‐adsorption performance. Here, 6 nm wall‐thick Ni2P–NiP2 hollow nanoparticle polymorphs combining metallic Ni2P and metalloid NiP2 with observable heterointerfaces are synthesized. It shows excellent catalytic performance toward the HER, requiring an overpotential of 59.7 mV to achieve 10 mA cm−2 with a Tafel slope of 58.8 mV dec−1. Density functional theory calculations verify electrons' transfer from P to Ni at the heterointerfaces, which decreases the absolute value of H* adsorption energy and simultaneously enhance electronic conductivity. That is, the heterojunctions balance the metallic Ni2P and the metalloid NiP2 to form an optimized phosphide polymorph catalyst for the HER. Furthermore, this polymorph combination is used with NiFe‐LDH nanosheets to form an alkaline electrolyzer. It shows highly desirable electrochemical properties, which can reach 10 mA cm−2 in 1 m KOH at 1.48 V and be driven by an AAA battery with a nominal voltage of 1.5 V. The work about interfacial charge transfer might provide an insight into designing excellent polymorph catalysts.
6‐nm‐thin‐wall Ni2P–NiP2 hollow nanoparticles with highly efficient hydrogen evolution reaction (HER) activity are designed. The electron transfer from P to Ni at the Ni2P–NiP2 interfaces can optimize the ΔGH* value of Ni2P–NiP2. This Ni2P–NiP2 polymorph combined with NiFe‐LDH nanosheets can be used as an alkaline electrolyzer driven by a 1.5 V (AAA) battery.
By using copper(I) homoenolates as nucleophiles, which are generated through the ring‐opening of 1‐substituted cyclopropane‐1‐ols, a catalytic asymmetric allylic substitution with allyl phosphates is ...achieved in high to excellent yields with high enantioselectivity. Both 1‐substituted cyclopropane‐1‐ols and allylic phosphates enjoy broad substrate scopes. Remarkably, various functional groups, such as ether, ester, tosylate, imide, alcohol, nitro, and carbamate are well tolerated. Moreover, the present method is nicely extended to the asymmetric construction of quaternary carbon centers. Some control experiments argue against a radical‐based reaction mechanism and a catalytic cycle based on a two‐electron process is proposed. Finally, the synthetic utilities of the product are showcased by means of the transformations of the terminal olefin group and the ketone group.
A catalytic asymmetric allylic substitution with NHC‐stabilized copper(I) homoenolates generated from cyclopropanols is developed that affords γ‐chiral ketones in excellent regio‐ and high enantioselectivities. This process enables the generation of chiral quaternary carbon centers and features a broad substrate scope.
Streptococcus mutans
is considered the most relevant bacteria in the transition of non-pathogenic commensal oral microbiota to biofilms which contribute to the dental caries process. The present ...study aimed to evaluate the antimicrobial activity of a natural plant product, cinnamaldehyde against
S. mutans
biofilms. Minimum inhibitory concentrations (MIC), minimal bactericidal concentration (MBC), and growth curves were determined to assess its antimicrobial effect against planktonic
S. mutans
. The biofilm biomass and metabolism with different concentrations of cinnamaldehyde and different incubation time points were assessed using the crystal violet and MTT assays. The biofilms were visualized using confocal laser scanning microscopy (CLSM). Bacterial cell surface hydrophobicity, aggregation, acid production, and acid tolerance were evaluated after cinnamaldehyde treatment. The gene expression of virulence-related factors (
gtfB
,
gtfC
,
gtfD
,
gbpB
,
comDE
,
vicR
,
ciaH
,
ldh
and
relA
) was investigated by real-time PCR. The MIC and MBC of cinnamaldehyde against planktonic
S. mutans
were 1000 and 2000 μg/mL, respectively. The results showed that cinnamaldehyde can decrease biofilm biomass and metabolism at sub-MIC concentrations. CLSM images revealed that the biofilm-covered surface areas decreased with increasing concentrations of cinnamaldehyde. Cinnamaldehyde increased cell surface hydrophobicity, reduced
S. mutans
aggregation, inhibited acid production, and acid tolerance. Genes expressions in the biofilms were down-regulated in the presence of cinnamaldehyde. Therefore, our data demonstrated that cinnamaldehyde at sub-MIC level suppressed the microbial activity on
S. mutans
biofilm by modulating hydrophobicity, aggregation, acid production, acid tolerance, and virulence gene expression.
Excitation of photoactive electron donor–acceptor (EDA) complexes is an effective way to generate radicals. Applications in a catalytic regime typically use catalytic donors. Herein, we report that ...readily available electron-poor tetrachlorophthalimides can act as effective organocatalytic acceptors to trigger the formation of EDA complexes with a variety of radical precursors not amenable to previous catalytic methods. Excitation with visible light generates carbon radicals under mild conditions. The versatility of this EDA complex catalytic platform allowed us to develop mechanistically distinct radical reactions, including in combination with a cobalt-based catalytic system. Quantum yield measurements established that a closed catalytic cycle is operational, which hints at the ability of tetrachlorophthalimides to readily turn over and govern each catalytic cycle.
This article investigates the effect of cross‐shareholdings on stock price synchronicity, as a measure of price informativeness, of the listed firms in the Chinese stock market. We gauge firms' ...levels of cross‐shareholdings in terms of centrality in the cross‐shareholding network. It is confirmed that it is through a noise‐reducing process that cross‐shareholdings promotes price synchronicity and reduces price delay. More importantly, this effect on price informativeness is pronounced for large firms and in the periods of market downturns. Overall, our analyses provide insights into the relation between the ownership structure and price informativeness.
Vitamins are a class of essential nutrients in the body; thus, they play important roles in human health. The chemicals are involved in many physiological functions and both their lack and excess can ...put health at risk. Therefore, the establishment of methods for monitoring vitamin concentrations in different matrices is necessary. In this review, an updated overview of the main pretreatments and determination methods that have been used since 2010 is given. Ultrasonic assisted extraction, liquid⁻liquid extraction, solid phase extraction and dispersive liquid⁻liquid microextraction are the most common pretreatment methods, while the determination methods involve chromatography methods, electrophoretic methods, microbiological assays, immunoassays, biosensors and several other methods. Different pretreatments and determination methods are discussed.
Perovskite solar cells (PSCs) are highly promising next‐generation photovoltaic devices because of the cheap raw materials, ideal band gap of ≈1.5 eV, broad absorption range, and high absorption ...coefficient. Although lead‐based inorganic‐organic PSC has achieved the highest power conversion efficiency (PCE) of 25.2%, the toxic nature of lead and poor stability strongly limits the commercialization. Lead‐free inorganic PSCs are potential alternatives to toxic and unstable organic‐inorganic PSCs. Particularly, double‐perovskite Cs2AgBiBr6‐based PSC has received interests for its all inorganic and lead‐free features. However, the PCE is limited by the inherent and extrinsic defects of Cs2AgBiBr6 films. Herein, an effective and facile strategy is reported for improving the PCE and stability by introducing an N719 dye interlayer, which plays multifunctional roles such as broadening the absorption spectrum, suppressing the charge carrier recombination, accelerating the hole extraction, and constructing an appropriate energy level alignment. Consequently, the optimizing cell delivers an outstanding PCE of 2.84%, much improved as compared with other Cs2AgBiBr6‐based PSCs reported so far in the literature. Moreover, the N719 interlayer greatly enhances the stability of PSCs under ambient conditions. This work highlights a useful strategy to boost the PCE and stability of lead‐free Cs2AgBiBr6‐based PSCs simultaneously, accelerating the commercialization of PSC technology.
A multifunctional N719 dye interlayer is introduced into lead‐free all‐inorganic Cs2AgBiBr6‐based perovskite solar cells to enhance the efficiency and stability by broadening the absorption spectrum, promoting the charge carrier separation/extraction and constructing an appropriate energy level alignment. As a result, the optimized device shows a superior power conversion efficiency of 2.84% and excellent operational stability under ambient conditions.
Chronic kidney disease (CKD) patients have an increased risk of cardiovascular diseases (CVDs). The present study aimed to investigate the gut microbiota and blood trimethylamine-N-oxide ...concentration (TMAO) in Chinese CKD patients and explore the underlying explanations through the animal experiment. The median plasma TMAO level was 30.33 μmol/L in the CKD patients, which was significantly higher than the 2.08 μmol/L concentration measured in the healthy controls. Next-generation sequence revealed obvious dysbiosis of the gut microbiome in CKD patients, with reduced bacterial diversity and biased community constitutions. CKD patients had higher percentages of opportunistic pathogens from gamma-Proteobacteria and reduced percentages of beneficial microbes, such as Roseburia, Coprococcus, and Ruminococcaceae. The PICRUSt analysis demonstrated that eight genes involved in choline, betaine, L-carnitine and trimethylamine (TMA) metabolism were changed in the CKD patients. Moreover, we transferred faecal samples from CKD patients and healthy controls into antibiotic-treated C57BL/6 mice and found that the mice that received gut microbes from the CKD patients had significantly higher plasma TMAO levels and different composition of gut microbiota than did the comparative mouse group. Our present study demonstrated that CKD patients had increased plasma TMAO levels due to contributions from both impaired renal functions and dysbiosis of the gut microbiota.
China is one of the countries with the highest incidence of gastric cancer. There are differences in epidemiological characteristics, clinicopathological features, tumor biological characteristics, ...treatment patterns, and drug selection between gastric cancer patients from the Eastern and Western countries. Non‐Chinese guidelines cannot specifically reflect the diagnosis and treatment characteristics for the Chinese gastric cancer patients. The Chinese Society of Clinical Oncology (CSCO) arranged for a panel of senior experts specializing in all sub‐specialties of gastric cancer to compile, discuss, and revise the guidelines on the diagnosis and treatment of gastric cancer based on the findings of evidence‐based medicine in China and abroad. By referring to the opinions of industry experts, taking into account of regional differences, giving full consideration to the accessibility of diagnosis and treatment resources, these experts have conducted experts’ consensus judgement on relevant evidence and made various grades of recommendations for the clinical diagnosis and treatment of gastric cancer to reflect the value of cancer treatment and meeting health economic indexes. This guideline uses tables and is complemented by explanatory and descriptive notes covering the diagnosis, comprehensive treatment, and follow‐up visits for gastric cancer.
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