A review of ^(17)O isotopic labeling techniques for solid-state NMR structural studies of metal oxides in lithium-ion batteries

Recent advances in utilizing ^(17)O isotopic labeling methods for solid-state nuclear magnetic resonance(NMR)investigations of metal oxides for lithium-ion batteries have yielded extensive insights into their structural and dynamic details.Herein,we commence with a brief introduction to recent research on lithium-ion battery oxide materials studied using ^(17)O solid-state NMR spectroscopy.Then we delve into a review of ^(17)O isotopic labeling methods for tagging oxygen sites in both the bulk and surfaces of metal oxides.At last,the unresolved problems and the future research directions for advancing the ^(17)O labeling technique are discussed.

Hierarchical sulfur and nitrogen co-doped carbon nanocages as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air battery

Exploring inexpensive and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) is critical for rechargeable metal-air batteries. Herein, we report a new 3D hierarchical sulfur and nitrogen co-doped carbon nanocages(hSNCNC) as a promising bifunctional oxygen electrocatalyst by an in-situ MgO template method with pyridine and thiophene as the mixed precursor. The as-prepared h SNCNC exhibits a positive half-wave potential of 0.792 V(vs. reversible hydrogen electrode, RHE) for ORR, and a low operating potential of 1.640 V at a 10 mA cm-2 current density for OER. The reversible oxygen electrode index is 0.847 V, far superior to commercial Pt/C and IrO2,which reaches the top level of the reported bifunctional catalysts. Consequently, the hSNCNC as air cathodes in an assembled Zn-air battery features low charge/discharge overpotential and long lifetime. The remarkable properties arises from the introduced multiple heteroatom dopants and stable 3D hierarchical structure with multi-scale pores, which provides the abundant uniform high-active S and N species and efficient charge transfer as well as mass transportation. These results demonstrate the potential strategy in developing suitable carbon-based bi-/multi-functional catalysts to enable the next generation of the rechargeable metal-air batteries.

Unusual structural properties of polymers confined in a nanocylinder

Structural properties of polymers confined in nanocylinders are investigated by Monte Carlo simulation, which is successfully used to consider the conformational property of constrained polymers. The conformational properties of the polymers close to the walls exhibit different features. The density profiles of polymers are enhanced near the wall of the nanocylinder, which shows that the packing densities differ near the wall and far from the wall. The highest densities near the wall of the nanocylinder decrease with increasing radius of the nanocylinder. Furthermore, the density excess is not only near the wall of the nanocylinder, but also shifts to the center of the nanocylinder at lower temperatures. The radius of gyration and the bond length of polymers in the nanocylinder show that the polymer chains tend to extend along the axis of the nanocylinder in highly confined nanocylinder and contract at lower temperature. Our results are very helpful in understanding the packing induced physical behaviors of polymers in nanocylinders, such as glass transition, crystallization,etc.

Balancing sub‐reaction activity to boost electrocatalytic urea synthesis using a metal‐free electrocatalyst

Electrocatalytic urea synthesis via coupling of nitrate with CO_(2)is considered as a promising alternative to the industrial urea synthetic process.However,the requirement of sub-reaction(NO_(3)RR and CO_(2)RR)activities for efficient urea synthesis is not clear and the related reaction mechanisms remain obscure.Here,the construction,breaking,and rebuilding of the sub-reaction activity balance would be accompanied by the corresponding regulation in urea synthesis,and the balance of sub-reaction activities was proven to play a vital role in efficient urea synthesis.With rational design,a urea yield rate of 610.6 mg h−1 gcat.−1 was realized on the N-doped carbon electrocatalyst,superior to that of noble-metal electrocatalysts.Based on the operando SRFTIR measurements,we proposed that urea synthesis arises from the coupling of^(*)NO and^(*)CO to generate the key intermediate of^(*)OCNO.This work provides new insights and guidelines into urea synthesis from the aspect of activity balance.

The bloom of natural product chemistry in China

Natural product chemistry is an important area across chemistry,biology,and pharmaceutical sciences.The discovery of natural products through isolation and structural elucidation expands the chemical space of biologically active molecules in an unparallel fashion;numerous medicinally relevant compounds arise from natural product scaffolds.The chemical synthesis of natural products advances the development of organic chemistry from the theoretical,

Cell mechanics and energetic costs of collective cell migration under confined microchannels

Mechanical force between cells relates to many biological processes of cell development.The cellular collective migration comes from cell-cell cooperation,and studying the intercellular mechanical properties helps elucidate collective cell migration.Herein,we studied cell-cell junctions,intercellular tensile force and the related cellular energetic costs in confined microchannels.Using the intercellular force sensor,we found that cells adapt to different confinement environments by regulating intercellular force,and thereby the relationship between collective cell migration and cell-cell junction were verified.Through the observation of cell orientation,actomyosin contractility,energetic costs,and glucose uptake,we can make a reasonable explanation of cell-force driven migration in different confined environments.Under highly confined conditions,the intercellular force and energetic costs are greater,and the cell orientation is more orderly.The collective migration behavior in confined spaces is closely related to the intercellular force and energetic costs,which is helpful to understand the collective migration behaviors in various confined spaces.

Controlled growth and photoconductive properties of hexagonal SnS2 nanoflakes with mesa-shaped atomic steps

We demonstrated the controlled growth of two-dimensional （2D） hexagonal tin disulfide （SnS2） nanoflakes with stacked monolayer atomic steps. The morphology was similar to flat-topped and step-sided mesa plateaus or step pyramids. The SnS2 nanoflakes were grown on mica substrates via an atmospheric-pressure chemical vapor deposition process using tin monosulfide and sulfur powder as precursors. Atomic force microscopy （AFM）, electron microscopy, and Raman characterizations were performed to investigate the structural features, and a sequential layer-wise epitaxial growth mechanism was revealed. In addition, systematic Raman characterizations were performed on individual SnS2 nanoflakes with a wide range of thicknesses （1-100 nm）, indicating that the A1g peak intensity and Raman shifts were closely related to the thickness of the SnS2 nanoflakes. Moreover, photoconductive AFM was performed on the monolayer-stepped SnS2 nanoflakes, revealing that the flat surface and the edges of the SnS2 atomic steps had different electrical conductive properties and photoconductive behaviors. This is ascribed to the dangling bonds and defects at the atomic step edges, which caused a height difference of the Schottky barriers formed at the interfaces between the PtIr-coated AFM tip and the step edges or the flat surface of the SnS2 nanoflakes. The 2D SnS2 crystals with regular monolayer atomic steps and fast photoresponsivity are promising for novel applications in photodetectors and integrated optoelectronic circuits.

Fabrication of nanozyme@DNA hydrogel and its application in biomedical analysis

Nanozymes have received great attention owing to the advantages of easy preparation and low cost. Unlike natural enzymes that readily adapt to physiological environments, artificial nanozymes are apt to passivate in complex clinical samples （e.g., serum）, which may damage the catalytic capability and consequently limit the application in biomedical analysis. To conquer this problem, in this study, we fabricated novel nanozyme@DNA hydrogel architecture by incorporat^ng nanozymes into a pure DNA hydrogel. Gold nanoparticles （AuNPs） were adopted as a model nanozyme. Results indicate that AuNPs incorporated in the DNA hydrogel retain their catalytic capability in serum as they are protected by the hydrogel, whereas AuNPs alone totally lose the catalytic capability in serum. The detection of hydrogen peroxide and glucose in serum based on the catalysis of the AuNPs@DNA hydrogel was achieved. The detection limit of each reaches 1.7 and 38 ~M, respectively, which is equal to the value obtained using natural enzymes. Besides the mechanisms, some other advantages, such as recyclability and availability, have also been explored. This nanozyme@DNA hydrogel architecture may have a great potential for the utilization of nanozymes as well as the application of nanozymes for biomedical analysis in complex physiological samples.

Ultrafast one-step synthesis of N and Ti^3＋ codoped TiO2 nanosheets via energetic material deflagration

An energetic-material （NAN3） deflagration method for preparing N- and Ti3＋-codoped TiO2 nanosheets （NT-TiO2） was developed. In this method, N radicals filled the crystal lattice, and Na clusters captured partial O from TiO2. The deflagration process was fast and facile and can be completed within 〈 I s after ignition. The obtained NT-TiO2 exhibited rough surfaces with nanopits and nanoholes. The doping concentration can be regulated by controlling the NaN3 addition. The NT-TiO2 samples showed significant enhancements in the visible-light absorption and photoelectric response. The simultaneously produced N radicals and Na clusters from NaN3 deflagration served as N sources and reduction agents, respectively. Additionally, the high deflagration temperature/ pressure improved the reactivity of N radicals and Na dusters. Thus, the present NaN3 deflagration method was demonstrated as an ultrafast and effective approach to fabricate NT-TiO2 with a visible-light response. The proposed NaN3 deflagration method allows the ultrafast synthesis of new functional materials via the efficient deflagration of energetic materials.

Visualizing nanopore blinkings in parallel:a high-throughput nanopore array potential for ultra-rapid DNA sequencing

Upon finishing the sequencing of the first complete human genome in 2004[1],the demand for fast DNA reading with less than$1,000 has been fueled by the ever-increasing awareness for personalized medicine and clinical diagnosis[2,3].Plenty of sequencing techniques,from the original Sanger sequencing method to novel sequencing-by-synthesis technologies(Roche,Solexa,SOLi D,etc.)[3],have been developed rapidly in past decades,which are sug-

Michael addition-based cyclization strategy in the total synthesis of Lycopodium alkaloids

Lycopodium alkaloids, a unique family of biologically important natural products isolated and characterized from various species of Lycopodium(sensu lato), have attracted extensive attention from chemists and pharmacists in the past three decades. Michael addition-based cyclization has been successfully employed as an elegant and efficient ring-construction protocol of constructing key cyclohexanone intermediates in the total synthesis of Lycopodium alkaloids. This mini-review chooses and summarizes several representative total syntheses of various Lycopodium alkaloids in which intramolecular Michael addition severed as the key methodology.

Self-assembly of Amphiphilic Diblock Copolymers Induced by Liquid-Liquid Phase Separation

The liquid-liquid phase separation(LLPS)widely exists in biology,synthetic chemistry,crystallization kinetics and other fields,and it is very important to realize the related functions.The research on the competition between LLPS and micellization/vesiculation has made considerable progress.However,the way to effectively control the formation paths from homogeneous state to aggregates has not been completely solved,which is vital to determine its structure and properties and even its future functions.Here we describe the phenomenon of LLPS and its effect on the dynamic process of self-assembly of amphiphilic diblock copolymers(BCPs).Starting from the establishment of phase diagram,we explore the existence conditions of LLPS state,the internal morphology and external size of large droplets,and its significant implications to the dynamic path of vesicle formation.Vesicles formed via LLPS have larger sized outer dimensions and inner cavities,and contain more solvents during certain stages.The detailed research of LLPS and its self-assembly simulation has contributed to completing its theoretical basis and practical applications in the future in various fields.

Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy: a Powerful Technique for Bioanalysis

Attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS)has recently been proven to be a powerful tool for bioanalysis.It enables in situ and in real-time observation of dynamic processes occurring on specific interface,revealing rich structural and functional information of biomolecules at sub monolayer level.The aim of this general review was to give an overview of the cutting edge applications of ATRSEIRAS.We start with description of the basic configuration of the standard ATR-SEIRAS platform.The enhanced mechanisms and methods to fabricate enhanced substrates are then presented.We discuss the recent developments,challenges and applications of ATR-SEIRAS in bioanalysis,mainly focusing on DNA analysis,protein behavior and cell properties.Finally,further development of the ATRSEIRAS technique with enhanced sensitivity,improved time and spatial resolutions will be prospected.

Stable pillar[5]arene-based pseudo[1]rotaxanes formed in polar solution

Mono-alkyl-functionalized pillar[5]arenes PI, P2, and P3 were synthesized by click reaction, which exhibited different self-assembly behavior in polar solvent DMSO. Stable pseudo[ 1 ]rotaxane was formed by the self-complexation from P1 or P2, whereas, concentration-dependent pseudorotaxane structures were generated by P3 which bearing more flexible side chain. Interestingly, the obtained pseudo[1]rotaxanes exhibited a dynamic fast assembly process upon adding NaBF4, resulting in the formation of Na＋-induced pseudorotaxanes.

MiRNA-203 suppresses tumor cell proliferation, migration and invasion by targeting Slug in gastric cancer

Snail, a family of zinc finger transcription factors, plays an important role in morphogenesis and embryogenesis. Snail zinc finger family 2 （SNAI2 or Slug） has been demonstrated to regulate carcinogenesis of several human cancers including breast, prostate, head, neck,

Synthesis of Two Coumarins Isolated from Aster praealtus

Two coumarins isolated from Aster praealtus were synthesized via a direct coupling of the corresponding cyclohexyl carbinol with a coumarin-derived aryl bromide or iodide, a very difficult etherification due to the excess steric congestion around the carbinol and the low reactivity of the aryl halide that frustrated many seemingly feasible protocols. Unequivocal ^1H and ^13C NMR data for these compounds were thus made available for the first time. Uncertainty and errors in ^1H and ^13C NMR data in previous reports are also eliminated and revealed, respectively.

Photo-stability and Photo-damage of SPASER Nanoparticles under Nanosecond Pulsed-laser

Comprehensive Summary SPASER nanoparticle(NP),with small size,ultranarrow spectral-line and good biocompatibility,is a potential biomedical nanoprobe.However,owning to the striking light absorption capacity of Au-resonator,huge energy could accumulate under strong pumping-laser,which would lead to poor photo-stability and unexpected photo-damage to SPASER NP,and is harmful to its future practical application but hasn't been systematically studied in experiment.

Unsteady Dynamics of Vesicles in a Confined Poiseuille Flow

The dynamic behaviors of a single vesicle bounded by the cylindrical wall in a Poiseuille flow were investigated by considering different confinements and dimensionless shear rates. By observing the evolution of two adjacent particles attached to the internal and external surfaces of the spherical vesicles, we found they had the same frequency. The vorticity trajectories formed by the time-tracing of the particles on the membrane are parallel, which can be identified as the unsteady rolling motion of the membranes due to the unfixed axis. The dynamic behaviors of vesicles are associated with the confinement degree and the dimensionless shear rate. The smaller dimensionless shear rate will result in the slower frequency of the rolling by examining the velocity of the rolling. The weakened rolling motion under stronger confinements is observed by measuring the evolution of the orientation angles. The changes of revolution axes over time can be interpreted by the lateral excursion of the center of mass on the orthogonal plane of the flow.

Dimeric G-quadruplex DNA Structure in the Proximal Promoter of VEGFR-2 Reveals a New Drug Target to Inhibit Tumor Angiogenesis

Vascular endothelial growth factor(VEGF)regulates tumor angiogenesis,which is active on the endothelium via VEGF receptor 2(VEGFR-2).The proximal promoter region of VEGFR-2(termed as VEGFR-2 DNA)is guanine-rich,forming G-quadruplex(G4)structures.Here,we demonstrate that VEGFR-2 DNA consists of one symmetrically dimeric 14-mer G4-DNA and one 12-mer sequence-palindromic dsDNA.This G4-DNA adopts an unprecedented folding with five stacked tetrads linked by four broken strands.Its 5’-end part contains an A-tetrad A^(1)•A^(4)•A^(1’)•A^(4’)and one G-tetrad G^(3)•G^(5)•G^(3’)•G^(5’)with two V-shaped loops and two one-nt edge-type loops.Its 3’-end part includes three G-tetrads G^(10)•G^(6)•G^(10’)•G^(6’),G^(11)•G^(7)•G^(11’)•G^(7’)(central)and G^(12)•G^(8)•G^(12’)•G^(8’)spanned by two double-chain-reversal one-nt(C^(9)or C^(9’))loops.Bases G^(13)and G^(13’)stack with G-tetrad G^(12)•G^(8)•G^(12’)•G^(8’).These characteristics make this G4-DNA more stable than reported VEGFR-17T G4 structure.The dsDNA connects with G4-DNA without any interactions,generating a linear assembly with G4-DNA structural bulges.These studies uncover new structural features of VEGFR-2 DNA as a potential drug target by inhibiting VEGFR-2 expression,thereby tumor angiogenesis.