Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has ...been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.
•ACE2 are highly expressed in human small intestinal enterocytes.•2019-nCoV may have same tissue tropism such as small intestine with SARS-CoV.•The gastrointestinal tract may be an alternative route ...for 2019-nCoV.•Distribution pattern of ACE2 gene insinuates the possibility of a fecal–oral transmission for COVID-19.
The coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China and rapidly spread in other countries in December 2019. The infected patients presented with fever, respiratory symptoms, sometimes with digestive and other systemic manifestations, and some progressed with a severe acute respiratory syndrome or even death. Associated digestive symptoms were frequently observed in the patients, with an unknown significance and mechanism. ACE2, as the major known functional receptor of the 2019 novel coronavirus (2019-nCoV) attracted our attention. We collected the clinical data of the 2019-nCoV-infected patients from published studies and extracted the data about the incidence of gastrointestinal symptoms. Furthermore, we used online datasets to analyze ACE2 expression in different human organs, especially in the small intestine, to explore the relationship between ACE2 expression patterns and clinical symptoms. We found that diarrhea accounted for a notable proportion of COVID-19 patients, ranging from 8.0% to 12.9%. The results reveal that ACE2 mRNA and protein are highly expressed in the small intestinal enterocytes but not in the goblet cells or intestinal immune cells. High expression of ACE2 on the surface cells in the digestive tract may lead to gastrointestinal symptoms and inflammation susceptibility. Overall, digestive symptoms were common in the COVID-19 patients. ACE2 expression on surface cells of the small intestine may mediate the invasion and amplification of the virus and activation of gastrointestinal inflammation. It is a possible mechanism of digestive symptoms in the COVID-19 patients and explains the presence of the virus in patients’ stool samples. The study also highlights the necessity of taking stool samples for suspected patients to help in early diagnosis and assessment of disease status.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Hierarchical bottom‐up structuring in nature provides inspiration for the construction of self‐assembled complex with advanced properties out of simple building blocks. However, the development of ...self‐standing assemblies of ultrasmall metal nanoparticles using redox ligands is still challenging. Here, a molecule‐confined reduction strategy to prepare robust self‐organized superstructures through metal–ligand interfacial interactions and hydrogen bonding is reported. High‐density and well‐separated Pd nanoparticles and single atoms are embedded within organometallic matrixes (Pd@eFc) via in situ reduction of the Pd precursor by redox‐active ligands. Furthermore, these metal–organic networks can be disassembled into fragments with highly dispersed Pd nanoparticles and single atoms by solvent mediation. Strikingly, Pd@eFc disassembly delivers excellent oxygen reduction performance, while its assembly can act as a selective hydrogenation catalyst. This viable molecule‐confined reduction strategy can also be applied to other organometallic superstructures (e.g., Au@eFc, Ag@eFc). The findings thus encourage on‐going study to explore controlled hierarchically self‐assembled superstructures for a wide range of catalysis.
Metal–organic superstructures (Pd@eFc) self‐organized from ultrasmall nanoparticles and redox ligands using a molecule‐confined reduction strategy, endowing intimate contact and strong metal–ligand interfacial interactions is reported. The Pd@eFc assembly goes through a disassembly process by solvent mediation. The Pd@eFc disassembly and assembly exhibits outstanding ORR activity in alkaline media and excellent performance in the selective hydrogenation of unsaturated aldehyde.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
D-limonene (4-isopropenyl-1-methylcyclohexene) is an important compound in several citrus essential oils (such as orange, lemon, tangerine, lime, and grapefruit). It has been used as a flavoring ...agent and as a food preservative agent, with generally recognized as safe (GRAS) status. D-limonene has been well-studied for its anti-inflammatory, antioxidant, anti-cancer, and antibacterial properties. The antibacterial activity of D-limonene against food-borne pathogens was investigated in this study by preparing a D-limonene nanoemulsion. The D-limonene solution and nanoemulsion have been prepared in six concentrations, 0.04%, 0.08%, 0.1%, 0.2%, 0.4%, and 0.8% (v/v), respectively, and the antibacterial activity was tested against four food-borne pathogens (Staphylococcus aureus, Listeria monocytogenes, Salmonella enterica, and Escherichia coli). The results showed that the D-limonene nanoemulsion had good nanoscale and overall particle size uniformity, and its particle size was about 3~5 nm. It has been found that the D-limonene solution and nanoemulsion have a minimal inhibitory concentration of 0.336 mg/mL, and that they could inhibit the growth of microorganisms efficiently. The data indicate that the D-limonene nanoemulsion has more antibacterial ability against microorganisms than the D-limonene essential oil. After bananas are treated with 1.0% and 1.5% D-limonene nanoemulsion coatings, the water loss of the bananas during storage and the percentage of weight loss are reduced, which can inhibit the activity of pectinase. The application of a biocoating provides a good degree of antibacterial activity and air and moisture barrier properties, which help with extending the shelf life of bananas.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
An unexploited pentacarboxylate ligand, 2,5-bis(3',5'-dicarboxylphenyl)-benzoic acid (H5L), was designed and used for the preparation of metal organic material using Zn2+ as a node. The new compound, ...{(Me2NH2)Zn2(L)(H2O).0.5DMF}n (1) (DMF = dimethylformamide), has been synthesized and structurally characterized. The topology of the 5-connected anionic framework may be described as (44)(66) (Schlaefli symbol) based on {M2(CO2)5} molecular building blocks (MBBs) and L ligands in 1. It has been demonstrated that 1 can act as a fluorescent sensor for highly sensitive detection of nitroaromatics and Fe3+, with a detection limit of 0.54 ppm for 2,4,6-trinitrophenol (TNP) and 0.81 ppm for Fe3+. The possible emission quenching mechanism in the presence of nitroaromatics has been addressed by theoretical calculations.
A new metal–organic framework having the formula (NH
2
(CH
3
)
2
)Zn
2
(OAc)(L)·0.5DMF (H
4
L = 2,5-di(3′,5′-dicarboxylphenyl)pyridine) (
GDMU-3
) has been synthesized and characterized. The net of
...GDMU-3
is uninodal and is closely related to the
lvt
net, which has the same Schläfli symbol of 4
2
·8
4
.
GDMU-3
displays selective properties for the detection of nitrobenzene and Fe
3+
ions. Remarkably,
GDMU-3
exhibits an excellent capability to adsorb methylene blue with high selectivity. The present work indicates that
GDMU-3
could be a potential candidate for developing novel luminescence sensors for the selective sensing of nitrobenzene which can be deployed for explosives, Fe
3+
and organic dyes.
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IJS, KILJ, NUK, UL, UM, UPUK
Tuning the activity of low-cost carbon materials for electroreduction of CO2 to valuable chemicals and fuels has attracted extensive attention due to its significance in energy and environmental ...problems, and the main challenge lies in how to tune the electronic structure of such materials using facile strategies. Here, we designed a novel and facile strategy for optimizing nitrogen-doped carbon (N–C) for efficient CO2 reduction reaction (CO2RR) by in situ encapsulation of nickel nanoparticles (NPs) into N-doped carbon nano-hybrid substrates (Ni/N-CHSs). Strikingly, the as-prepared Ni/N-CHS catalyst exhibits excellent performances towards catalyzing CO2 into CO with a high faradaic efficiency of 93.1% at −0.9 V vs. the reversible hydrogen electrode (RHE) and remarkable long-term durability, which is even comparable to those of state-of-the-art CO2RR catalysts. Theoretical calculations indicated that the inclusion of Ni NPs could enhance the activity of N–C for the CO2RR by deeply reducing the activation barriers. This work thus provided an ideal route to rational in situ encapsulation of metal NPs into N–C materials, further tuning the electronic structure and significantly enhancing the CO2RR performance of low-cost carbon materials.
A new metal–organic framework, formulated as {Zn
2
(L)(DMF)
3
·2DMF·2H
2
O} (
1
), has been synthesized using a symmetrical rigid carboxylate ligand terphenyl-3,3′′,5,5′′-tetracarboxylic acid (H
4
...L). Single-crystal X-ray diffraction analysis shows that
1
possesses a 3D uninodal 4-c lonsdaleite (
lon
) topology based on binuclear Zn clusters.
1
behaves as a fluorescent chemosensor for highly selective and sensitive detection of Fe
3+
/Fe
2+
ions, 2,4-dinitrophenol (2,4-DNP),
p
-nitrophenol (PNP) and 2,4,6-trinitrophenol (TNP). Furthermore, the photocatalytic properties of
1
for degradation of methyl violet (MV) and Rhodamine B (RhB) have been explored. The possible emission quenching of
1
in the presence of aromatic compounds has been addressed by theoretical calculations and the photocatalytic activity of
1
against organic dyes has been addressed using density of states (DOS) calculations.
Semiconductor polymeric graphitic carbon nitride (g-C3N4) is considered a favorable candidate for converting solar energy into chemical energy driven by visible light. Nevertheless, its practical ...applications are largely impeded by the low specific surface area, fast recombination of photoexcited electron–hole pairs, and limited visible-light response range. Therefore, it is highly desirable to improve the photocatalytic performance of metal-free g-C3N4 photocatalysts at the molecular level by elemental doping. This study developed a rational cross-linking copolymerization strategy to synthesize sulfur-doped g-C3N4 (S-CN) using urea and 4-mercaptobenzoic acid (4-MBA) as precursors. The results indicate that the introduction of S atoms onto the g-C3N4 framework through the formation of C–S bonds leads to the reduction of the interlayer stacking distances, narrowing of the band gap, expansion of visible-light absorption regions, and increased separation and transfer of photoinduced electron–hole pairs. The optimal S-CN-7 sample exhibits outstanding photocatalytic performance under visible light with the highest hydrogen production rate of 133.12 μmol h−1, which was nearly 8-fold higher than that of pure g-C3N4 (16.83 μmol h−1). In addition, the S-CN sample shows high photocatalytic stability after recycling experiments of up to 20 hours. Theoretical calculations show that doping with S leaves the sample with impurity states, making it easy for photogenerated electrons to jump from the valence band to the impurity state or from the impurity state to the conduction band.
Respiratory viruses, such as severe acute respiratory syndrome coronavirus (SARS-CoV)-1, SARS-CoV-2, influenza A viruses, and respiratory syncytial virus, pose a serious threat to society. Based on ...the guiding principles of “holism” and “syndrome differentiation and treatment”, traditional Chinese medicine (TCM) has unique advantages in the treatment of respiratory virus diseases owing to the synergistic effect of multiple components and targets, which prevents drug resistance from arising. According to TCM theory, there are two main strategies in antiviral treatments, namely “dispelling evil” and “fu zheng”. Dispelling evil corresponds to the direct inhibition of virus growth and fu zheng corresponds to immune regulation, inflammation control, and tissue protection in the host. In this review, current progress in using TCMs against respiratory viruses is summarized according to modern biological theories. The prospects for developing TCMs against respiratory viruses is discussed to provide a reference for the research and development of innovative TCMs with multiple components, multiple targets, and low toxicity.
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