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The introduction of spinel phase to form the layered-spinel structure (LSS) is an effective way to improve the electrochemical performance of Li- and Mn-rich layered oxides (LMR). But is this structure universal for all LMR systems? In this work, different Mn/Ni ratio systems with the LSS are discussed in detail. It is found that, high discharge capacity (200.8 mA h g−1 at 1C rate; 1C = 250 mA h g−1) as well as high capacity-retention (94% at 1C rate after 100 cycles) can be achieved by forming the LSS for low-Ni system (Mn/Ni = 5.0). However, the capacity retention decreases severely in the high-Ni system (Mn/Ni = 3.5, 2.6). For example, when the ratio of Mn/Ni is 3.5, the capacity-retention of the layered-spinel sample was only 65.8%, compared to the 83% of the original LMR sample. The Ex-situ XRD, XPS, and HRTEM results demonstrate that the introduction of spinel phase in high-Ni system accelerates the transition and collapse of the crystal structure. This work provides guidance for optimizing the proportions of elements and the design of structures for the LMR.

The continuous growth of the solid-electrolyte interface (SEI) and material crushing are the fundamental issues that hinder the application of Ge anodes in lithium-ion batteries. Solving Ge deformation crushing during discharge/charge cycles is challenging using conventional carbon coating modification methods. Due to the chemical stability and high melting point of carbon (3500 °C), Ge/carbon hybridization at the atomic level is challenging. By selecting a suitable carbon source and introducing an active medium, we have achieved the Ge/carbon doping at the atom-level, and this Ge/carbon anode shows excellent electrochemical performance. The reversible capacity is maintained at 1127 mAh g-1 after 1000 cycles (2 A g-1 (2-71 cycles), 4 A g-1 (72-1000 cycles)) with a retention of 84 % compared to the second cycle. The thickness of the SEI is only 17.4 nm after 1000 cycles. The excellent electrochemical performance and stable SEI fully reflect the application potential of this material.

Binders have been confirmed to play a significant role in improving the cycling performance of Si anode. Some of natural biogum binders are exploited and related progresses are also achieved. However, the distinction of characteristics among different biogum binders as well as corresponding mechanisms and principles still remain to be elucidated. In this study, gum arabic (GA), guar gum (GG), and xanthan gum (XG) are selected for comparison. The highest initial Coulombic efficiency (ICE) of 90.4% is obtained with GA owing to diverse multiple interactions with Si nanoparticles to form a homogeneous covering that could protect Si core against being exposed to electrolyte and generating SEI film, as well as strong covalent network to suppress the isolation of Si, while plastic damage occurs during repeated volume change of Si because of irreversible bonding nature. By contrast, hydrogen bonding between polar –OH groups with self-healing nature provides Si anodes with GG and XG better cycling stability, while the optimized capacity of 1323 mAh g−1 after 100 cycles is retained with GG due to the extra ability to transfer Li+. This study provides the design and selection principles for binders applied in Si anodes of lithium-ion batteries.

A binder is an important component in lithium-ion batteries and plays a significant role in maintaining the properties of active substances. Most studies in the field of binders have only focussed on physical properties such as bonding performance. Here, a polyacrylic acid-modified binder was designed and adapted to Li[Ni0.8Co0.1Mn0.1]O2, which enhanced the electrochemical stability of Li[Ni0.8Co0.1Mn0.1]O2 from 30.2 to 66.6% (300 cycles at 1 C). We for the first time discovered that this was caused by a chemical reaction between polyacrylic acid and the residual lithium on the surface during the cycling, which formed a lithium propionic acid coating layer and maintained the stability of the layered structure.

Nickel-rich layered transition metal oxides are considered as promising cathode candidates to construct next-generation lithium-ion batteries to satisfy the demands of electrical vehicles, because of the high energy density, low cost, and environment friendliness. However, some problems related to rate capability, structure stability, and safety still hamper their commercial application. In this Review, beginning with the relationships between the physicochemical properties and electrochemical performance, the underlying mechanisms of the capacity/voltage fade and the unstable structure of Ni-rich cathodes are deeply analyzed. Furthermore, the recent research progress of Ni-rich oxide cathode materials through element doping, surface modification, and structure tuning are summarized. Finally, this review concludes by discussing new insights to expand the field of Ni-rich oxides and promote practical applications.

Au(I)-catalyzed selective reactions of Et- and tBu-substituted propiolates (1a and 1a′) with 1,2-benzisoxazole(2a) provide a new strategy for purposefully access to desired bioactive heterocycles. ...

N-doped straw sheaf–like porous MnO@C composite is synthesized through a L-histidine-assisted hydrothermal method with consequent annealing in Ar. The straw sheaf–like porous structure is assembled by MnO nanoparticles with a diameter of ~ 15 nm and be uniformly wrapped in amorphous N-doped carbon matrix. MnO@C-N displays attractive electrochemical properties when used as anode of lithium-/sodium-ion batteries. A high reversible capacity of 832.5 mA h g−1 could be obtained at 100 mA g−1 in LIBs and 250 mA h g−1 at 50 mA g−1 with outstanding cycling stability in SIBs. The study also compared MnO@C-N with commercial MnO particles in LIBs and shows that MnO@C-N anode has excellent cycling performance with 614.0 mA h g−1 retained after 200 cycles. However, commercial MnO displays only 413.5 mA h g−1 after 132 cycles. The present synthesis strategy opens the possibility of fabricating MnO@C-N nanocomposites for high-performance batteries.

CoNi-contained nanosheets can be prepared by dealloying CoNiAl alloys in aqueous NaOH solution in the presence of H2O2, and upon annealing sample exhibits dendritic NiCo2O4 micro-nanostructure. The effect of H2O2 solution on the structure, morphology, and electrochemical performances of the resulting products is studied systematically. These results indicate that the H2O2 solution mainly influences the morphology of the NiCo2O4. When tested as anode materials for lithium-ion batteries (LIBs), the obtained NiCo2O4 sample shows high specific capacity, excellent rate property, and superb cycling stability. A reversible capacity is still maintained at 1016.9 mAh/g after 100 cycles at a current density of 100 mA/g. Even at a current rate of 1000 mA/g, the capacity can reach to 691.4 mAh/g. The outstanding electrochemical properties of the NiCo2O4 anode make them promising anode materials of LIBs and other energy storage applications.

Metal sulfides with high capacity have been considered as candidates for efficient sodium-ion storage. However, their undesirable rate capability and fast capacity fading hinder their commercial applications. Herein, we prepared a platelet-like CuS material with twin crystals. The edges of the platelet are composed of single crystal structures, and the interior of platelet contains twin crystal structures. Due to its structural and compositional advantages, this platelet-like CuS material with twin crystal structures manifests superior rate performance (420 mA h g−1 at 0.05 A g−1 and 277 mA h g−1 at 5 A g−1) and excellent cycling stability without capacity decay after around 500 cycles at 2 A g−1.

In practice, high fidelity fluorescence imaging in vivo faces many issues, for example: (1) the fluorescence background of the probe is bleached by the wide intensity scale of fluorescence microscopy, displaying an inherent false negative background (FNB); and (2) the dosage of the probe has to be increased to achieve sufficient intensity for in vivo imaging, causing a vicious cycle that exacerbates the FNB. Herein, we constructed a fluorophore (F)–electron donor (D)–electron regulator (R) system, and thereby developed a dual modulation strategy for the de novo design of high fidelity probes. Using cross-talk modulation, the probe allows: (1) enhanced ESET (excited state electron transfer) from F to D, which minimizes the inherent FNB based on synergistic PET (photo induced electron transfer); and (2) the inhibition of PET and weakening of ESET from F to D to maximize the reporting intensity to further reduce the FNB, which is additionally enhanced by an overdose of the probe. To test the implementation, we constructed a 7-hydroxy-2-oxo-2H-chromene-3-carbaldehyde (HPC) series of probes, with HPC (F) as the fluorophore, 2-hydrazinylpyridine, which was screened as an electronically adjustable donor (D), and electronic regulators (R). In particular, HPC-7 and HPC-8 provided cell/zebrafish imaging with negligible background even using the rather low fluorescence scale of microscopy (a region for revealing hidden background). Interestingly, with the specificity of HPC for reporting zinc, we achieved probe HPC-5, which possesses both an ultralow inherent FNB and optimal reporting intensity for tissue and in vivo imaging, enabling the in vivo imaging of zinc in mice for the first time. Under this high-fidelity mode, the fluorescence monitoring of zinc ions during the development of liver cancer in mice was successfully performed. We envision that the dual modulation strategy with the F–D–R system could provide a useful concept for the de novo design of practical probes., We engineered a cross-talk electron transfer strategy using an F–D–A system to reduce the false negative background for high fidelity imaging in vivo.

A novel efficient photoelectrochemical (PEC) sensor was assembled for curcumin (Cur) detection using 2-mercaptoacetic acid (TGA)-capped CdTe nanoparticles and nickel tetra-amined phthalocyanine-linked graphene oxide (TGA-CdTe@NiTAPc-Gr). The TGA-CdTe nanoparticles could be firmly immobilized on the thin film structure of NiTAPc-Gr in a hydrogen-bonded manner, thus producing the proposed PEC sensor with a high photoelectrochemical activity of TGA-CdTe nanoparticles and excellent stability of NiTAPc-Gr. The TGA-CdTe@NiTAPc-Gr thin film showed a stronger blue light absorption property than the individual precursors, and this resulted in the sensitive detection of Cur ranging from 0.25–100 μM with a detection limit of 12.50 nM. In addition, the PEC sensor exhibited a high sensitivity and selectivity and quite good reproducibility. Thus, it shows potential for Cur detection in real samples.

Three kinds of Cu-Sn alloy anodes with different current collectors for lithium ion batteries had been directly prepared by cost-effective and easy to scale-up electro-deposition method. Both the self-standing electrode and the electrode with polypyrrole (PPy) current collector had effects on enhancing the cycle stability and increasing the gravimetric energy density. However, due to the poor conductivity of PPy and the low crystallinity structure of Cu-Sn alloy layer, the high rate performance of Cu-Sn alloy electrode with PPy current collector was unsatisfactory, while the self-standing electrode not only greatly increased the cycle stability and energy density of the whole electrode to a large extent, but also exhibited superior high-current cycle performance. Even cycled at a current density of 6 A g−1 after 700 cycles, the self-standing electrode could still maintain a specific capacity of 332 mA h g−1, which illustrated the potential application prospect of self-standing electrode with higher energy density and power density.

The unexpected oxyamination reaction of O, ω-unsaturated alkoxyamines was found experimentally. The mechanistic issues were studied by DFT calculations. It is suggested that the reaction undergoes [3 + 2] cyclic addition, O N bond cleavage, C N reductive elimination, and the Rh N unit protonation, generating the product and regenerating the active catalyst. The nitrene Rh(V) species containing a Rh C bond rather than a Rh O bond was suggested to be involved in the reaction mechanism. Why the substrate A with X = O but not X = C undergoes oxyamination reaction was rationalized based on the suggested reaction mechanism.

Neuromorphic computing holds promise for building next-generation intelligent systems in a more energy-efficient way than the conventional von Neumann computing architecture. Memristive hardware, which mimics biological neurons and synapses, offers high-speed operation and low power consumption, enabling energy- and area-efficient, brain-inspired computing. Here, recent advances in memristive materials and strategies that emulate synaptic functions for neuromorphic computing are highlighted. The working principles and characteristics of biological neurons and synapses, which can be mimicked by memristive devices, are presented. Besides device structures and operation with different external stimuli such as electric, magnetic, and optical fields, how memristive materials with a rich variety of underlying physical mechanisms can allow fast, reliable, and low-power neuromorphic applications is also discussed. Finally, device requirements are examined and a perspective on challenges in developing memristive materials for device engineering and computing science is given.

Metal sulfides have been intensively investigated for efficient sodium‐ion storage due to their high capacity. However, the mechanisms behind the reaction pathways and phase transformation are still unclear. Moreover, the effects of designed nanostructure on the electrochemical behaviors are rarely reported. Herein, a hydrangea‐like CuS microsphere is prepared via a facile synthetic method and displays significantly enhanced rate and cycle performance. Unlike the traditional intercalation and conversion reactions, an irreversible amorphization process is evidenced and elucidated with the help of in situ high‐resolution synchrotron radiation diffraction analyses, and transmission electron microscopy. The oriented (006) crystal plane growth of the primary CuS nanosheets provide more channels and adsorption sites for Na ions intercalation and the resultant low overpotential is beneficial for the amorphous Cu‐S cluster, which is consistent with the density functional theory calculation. This study can offer new insights into the correlation between the atomic‐scale phase transformation and macro‐scale nanostructure design and open a new principle for the electrode materials' design., A hydrangea‐like CuS microsphere with high geometrical symmetry and oriented (006) crystal plane growth is successfully constructed through a facile synthetic route. The oriented (006) crystal plane growth of the primary CuS nanosheets provide more channels and adsorption sites for Na ions intercalation, and the resultant low overpotential is beneficial for the amorphous Cu‐S cluster.

Organisms have built up immunological systems, where mitochondrial SO2 plays conflicting roles in regulating cell apoptosis. However, no exploration on the influence and regulating principle of mitochondrial SO2 to the specific apoptosis type can be found, which brings about a challenge to fluorescent probes. Herein, we optimize the fluorophore and develop a new fluorescent probe FHMI ((E)-4-(3-formyl-4-hydroxystyryl)-1-methylpyridin-1-iumiodide) by equipping an ICT (intramolecular charge transfer) fluorophore HMII ((E)-4-(4-hydroxystyryl)-1-methylpyridin-1-ium iodide) with an aldehyde group that serves as both fluorescence quencher and reporting group. After the optimization, although the nonconjugated electron donor is formed when sensing SO2, the preset ICT fluorophore HMII is permitted to release the fluorescence at the enlarged wavelength. Compared with the traditional design, the probe FHMI exhibits obvious enhanced fluorescence with large red shift. FHMI is successfully applied to the mechanistic e...

Density functional theory (DFT) calculations have been performed to unravel the detailed mechanism of the CpRe(CO)3-catalyzed coupling reaction of CO2 with chloromethyloxirane (R). The mechanisms proposed in previous literature have been examined. However, the computed results seem not to completely rationalize the experimental findings. Alternatively, by performing an exhaustive search on the potential energy surface, we presented a novel CO-assisted mechanism, which provides an effective access to the catalytic coupling. The newly established mechanism involves the C O bond cleavage of R from the less hindered side, release of one CO ligand, CO2 insertion, re-coordination of the dissociated CO ligand, another CO ligand shift, reductive elimination with simultaneous migration of carbonyl substituent, resulting in P and regeneration of CpRe(CO)2. Two CO ligands attached to CpRe(CO)2 play significant roles in lowering the key CO2 insertion and reductive elimination: (i) One CO ligand dissociation prior to CO2 insertion contributes to reduce the electron density on the Re metal, facilitating the CO2 O atom nucleophilic attack. (ii) After performing the migration, another initially inactive CO ligand serves as a carbonyl substituent, which lowers the energy penalty for later reductive elimination through the resultant extra π-interaction and the smaller ring tension energy involved in TS. The theoretical results provide insight into the mechanism of the important coupling reaction and rationalize well the experimental observations.

Density functional theory (DFT) calculations have been performed to study the Pd-catalyzed C-H functionalization of (E)-N-methoxy cinnamamide (E1), which selectively provides the α-C-H activation products (EP as minor product and its C═C rotation isomer ZP' as major product). Three crucial issues are solved: (i) The detailed mechanism leading to ZP' is one issue. The computational analyses of the mechanisms proposed in previously experimental and theoretical literature do not seem to be consistent with the experimental findings due to the high barriers involved. Alternatively, we present a novel oxidation/reduction-promoted mechanism featuring the Pd(0) → Pd(II) → Pd(0) transformation. The newly proposed mechanism involves the initial coordination of the active catalyst PdL2 (L = t-BuCN) with the C═C bond in EP, followed by the oxidative cyclization/reductive decyclization-assisted C═C double-bond rotation processes resulting in ZP' and regeneration of PdL2. (ii) The origin of the product E/Z selectivity is the second issue. On the basis of the calculated results, it is found that, at the initial stage of the reaction, EP is certainly completely generated, while no ZP' formation occurred. Once E1 is used up, EP immediately acts as the partner of the new catalytic cycle and sluggishly evolves into ZP'. A small amount of generated ZP' would reversibly transform to EP due to the higher barrier involved. (iii) The intrinsic reasons for the regioselectivity are the third issue. The calculated results indicate that the regioselectivity for α-C-H activation is mainly attributed to the stronger electrostatic attraction between the α-C and the metal center.

Density functional theory (DFT) calculations have been conducted to unravel the mechanisms and chemoselectivities of Au-catalyzed diazo-based couplings with phenyl unsaturated aliphatic alcohols: the propargyl alcohol Ba resulting in the [4 + 1]-cycloaddition product P4a and the allyl alcohol Db giving the [2,3]-σ rearrangement species P5b. P4a formation involves a catalyst interaction with phenyldiazoacetate, N2 release, a hydroxyl O nucleophilic attack of Ba, a [1,4]-H shift, coordination isomerization, 5-endo-dig cyclization, a [4,1]-H shift and a H2O-assisted [1,3]-H shift. After the [4,1]-H shift, the slightly less favorable five-membered ring-opening possibly follows to afford trace P5a ([2,3]-σ rearrangement product), which would be kept in solution due to subsequent irreversible evolution. In addition, the Ba-involved chemoselectivity was probed and explained as follows: (i) both large H(hydroxyl)⋯C(carbene) electrostatic repulsion and strong three-membered ring strain involved in the TS make the formation of the O–H insertion product P1a difficult and (ii) the nucleophilic attack from the C2 atom of Ba brings about a structural twisting and thus increases the energy penalty forming the cyclopropenation product P2a. On the other hand, compared with the sp-C2 atom of Ba, the sp2-C2 atom of Db greatly facilitates the five-membered ring-opening step because of the presence of an extra pπ–pπ orbital overlap and eventually provides P5b exclusively.

High catalytic performance of a single-atom transition metal ion (TMx+) anchored on the two-dimensional (2D) C2N lattice is predicted for HCOOH dehydrogenation. Considering the Co2+, Cu2+ and Ni2+ non-noble metal ions supported by C2N, we use density functional theory to demonstrate dehydrogenation energy barriers as low as those for pure Pt and Pd catalysts. The high catalytic performance is ascribed to the reaction occurring through a dual-active center composed of TMx+ and a nearby N atom of C2N. Specifically, C2N–Co2+ in the low spin state (S = 1/2) greatly promotes HCOOH dehydrogenation by decreasing the barrier of the rate-determining step to only 0.30 eV, mainly due to the strong ability of TMx+ to extract charges from HCOOH and C2N. The obtained mechanistic insights help the rational design of single-atom based transition metal ion catalysts supported by 2D materials.

Herein, the reaction mechanisms for the rhodium-catalyzed regioselective C7-functionalization of N-acyl indole are theoretically investigated by employing density functional theory (DFT) calculations. The role of the additive AgNTf2 in enhancing the reactivity and selectivity for the C7–H functionalization of N-acyl indole is clarified by calculations. The origins of the effect of the substituent group at the 6-position of N-acyl indole on the regioselectivity are explored by analyzing the electron and steric effects. The 7-olefination product is preferred for the H-substituted substrate (reaction A), which is attributed to the greater nucleophilicity of the C7 atom in comparison to that of the C2 atom. This facilitates the subsequent electrophilic attack of the Rh center. In reaction B with the CF3-substituted substrate, the 2-olefination product is preferred over the 7-olefination product mainly because of the stronger steric effects in TS2(C7)F compared with that in TS2(C2)F.

SiO2 is one of the critical raw materials for preparing Si anode. The direct use of porous Si made from SiO2 in LIBs is challenging. Although carbon cladding can improve the cycling performance of Si anode materials made from SiO2, the surface coating cannot address the comminution inside the material during repeated volume deformation. For the first time, we prepared an in-situ doped Si/carbon anode material that uses SiO2 and CO2 as Si and carbon sources and Mg as the reduction medium (Mg2Si + CO2 → MgO + Si + C). The in situ embedded carbon completes the nanosizing of Si (less than50 nm) and forms a three-dimensional (3-D) carbon network that enhances electrical conductivity and acts as a buffer layer. After 500 cycles at 0.5 A g−1, the discharge specific capacity is 912 mAh g−1, and the capacity still has 1487 mAh g−1 even at 4 A g−1. The simple method of preparing Si/carbon composite material in situ provides a new idea for modifying Si-based anode material and provides a valuable reference for carbon doping.

Shuttle effect is the core problem in lithium-sulfur battery, which makes internally poor dynamics and bad cycle stability of the lithium-sulfur battery (Li–S battery). In this study, a sheet nitrogen-doped vanadium dioxide material that roots in a metal-organic framework (SVO) was designed and synthesized. SVO has a unique two-dimensional structure and uniform distribution of metal sites. It leads to the adsorption-catalytic synergistic effect that can efficiently anchor polysulfides and promote sulfur conversion kinetics to significantly alleviate the shuttle effect. With the metal-organic framework precursor synthesized under mild conditions of room temperature and pressure, the SVO materials used to modify the separator can be simply obtained by calcination. Especially, the modified material exhibits excellent electrochemical performance with only 0.081% degradation of capacity per cycle at 1C after 500 cycles. Even under a harsh condition (sulfur loading = 6.3 mg cm−2, E/S = 5), the battery with SVO/AB separator is available to reach an area capacity of about 4.16 mAh cm−2 at 0.1C. Meantime, as for the anode side, SVO/AB separator can be used as lithium-ion guides to keep stable lithium-ion stripping/plating and inhibit the growth of lithium dendrite. The battery with SVO/AB separator also shows superior performance under high and low temperatures.

The mechanisms and chemo- and regioselectivities of divergent (Ni(cod)2/PCy3)-mediated/-catalyzed C(sp3)–F bond activation of 2-trifluoromethyl-1-alkenes (1) with alkynes (2) were investigated by density functional theory (DFT) calculations. The nickel-mediated/-catalyzed reaction involves sequential ligand exchange, alkene coordination, oxidative cyclization (1 + Ni(0) + 2), and first β-F(C(sp3)) elimination to give a common and requisite alkenylnickel(II) species, which bifurcates into either stoichiometric defluorinative [3 + 2] cycloaddition product 3 or catalytic defluorinative coupling products (nonmethylated 5, monomethylated 8, or trimethylated 9) depending on the absence and presence of additional reagents (Et3SiH, ZnMe2, and AlMe3). The Et3SiH-induced formation of 5 is found to be a result of facile metathesis relative to the 5-endo insertion leading to 3. Because of the presence of an F→Zn/Al interaction, ZnMe2/AlMe3 brings the methyl into defluorinative coupling products. In the stoichiometric...

A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials.

Benzene ring functionalization provides useful alternatives to access indole derivatives and has received much attention in recent years. In this work, the mechanism of Pt(II)-catalyzed cyclization/alkynylation of benziodoxole with pyrrole homopropargylic ethers to generate C5-alkenylated indole derivatives has been studied with the aid of density functional theory (DFT) calculations. We found that five-membered-ring cyclization/six-membered-ring cyclization is competitive in the formation of an indole skeleton. The following aromatization stage prefers the reaction sequence bicarbonate-assisted deprotonation at the C3a position, H2CO3-promoted methoxy elimination at the C7 position, and bicarbonate-assisted deprotonation at the C6 position. In the last alkynylation stage, the oxidative substitution mechanism assisted by H2CO3 is found to be favored over the previously proposed 1,2-iodo shift and oxidative addition. The overall rate-determining step is oxidative substitution. Additionally, an interesting ...

Intracellular reactive sulfur species and reactive oxygen species play vital roles in immunologic mechanism. As an emerging signal transmitter, SO2 can be generated as the anti-oxidant, while SO2 is also a potential oxidative stress-inducer in organism. Aiming to elucidate in-depth the dichotomous role of SO2 under oxidative stress, we designed a dual-response fluorescent probe that enabled the respective or successive detection of SO2 and ClO−. The probe itself emits the red fluorescence (625 nm) which can largely switch to blue (410 nm) and green fluorescence (500 nm) respectively in response to SO2 and ClO−, allowing the highly selective and accurate ratiometric quantification for both SO2 and ClO− in cells. Moreover the ultrafast (SO2

A rapid, accurate and sensitive method, using the stable isotope labeling (SIL), microwave-assisted dispersive liquid-liquid micro extraction (MADLLME) and the ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), was developed and validated for the determination of hydroxyl UV Filters in environmental water samples. A pair of new isotopic tags D0-/D3-1-methylindole-3-acetic acid (D0-/D3-MIAA) is synthesized, with which a simple yet efficient pretreatment MADLLME-SIL is developed. Under the optimized conditions (80℃, 240W, 180s), the sample pretreatment including analyte extraction, pre-concentration and isotope labeling can be finished conveniently in only 9min. D0-/D3-MIAA labeling improves the chromatographic retention by strengthening the hydrophobicity and enhances the MS response for 3-4 orders of magnitude. Excellent linearity is established by the H/D ratios of 1/10-10/1 with the correlation coefficients >0.9990. The quite low detection limits (0.54-1.79ng/L) are achieved, ensuring the trace detection. This method is successfully applied to a series of environmental water samples. The recoveries (93.2%~103.5%) are significantly improved and the analysis time is largely reduced (

Probe for α-ketoglutaric acid (α-KA) usually provides low sensitivity, invisible colour change and complex procedure with surfacants, which limits the accurate, sensitive quantification and mornitoring of α-KA in biological samples. Essentially different from the routine sensing mechanism, a special mechanism of photo-induced electron transfer (PET) combining with large absorption red-shift (rather than emission) has been designed to develop a facile yet multifunctional probe for the simultaneous fluorimetric, absorption-ratiometric and colorimetric detections of α-KA in biological samples. Effective inhibition of PET ensured the intense fluorescence turn-on (60 fold) and qutie low detection limit (0.9 μM) for α-KA without need of any surfacants. Dramatical colour change caused by the large absorption red shift (100 nm) from UV–vis region enabled the colormetric analysis of α-KA by naked-eye. Meanwhile, the large absorption red shift also contributed to the ratiometric detection, allowing for the accurate quantification of α-KA in complex biological sample. With this probe, ratiometric detection, naked eye mornitoring and imaging of α-KA in serum, living cells and tissues are realized for the first time.

Density functional theory (DFT) calculations have been performed to unravel the mechanism of Lewis-acid-induced Ni(cod)2-catalyzed selective coupling reactions of one diketene and two alkynes. Complex mixtures (unsymmetrical phenylacetic acid P1, symmetrical phenylacetic acid P2 and (3E)-4-ethyl-5-methylene-3-heptenoic acid P3) were obtained in the absence of Et2Al(OEt). P1 formation involves C(sp2)-O oxidative addition of diketene, twice alkyne insertion, intramolecular C═C insertion, acidolysis, and β-H elimination. For P2/P3 formation, the common key issue related to the C═C double bond cleavage of the substrate diketene was explored and found that it was accomplished via a four-membered-ring-closure/four-membered-ring-opening process. And then, P2 was produced via the second alkyne insertion while P3 was accessed by a stoichiometric reaction with HCl. The Et2Al(OEt)-induced chemoselectivity was also probed. It is found that the Ni–O (from Al reagent) bonding facilitates the second alkyne insertion, an...

Density functional theory (DFT) calculations have been conducted to elucidate the detailed mechanism of Pd-Catalyzed intramolecular Heck reaction of N-vinylacetamides. Pd(PPh3)2 and (PPh3)PdOAc−, generated in situ from Pd(OAc)2/PPh3, are predicted to be the active Pd(0) catalyst. The reaction undergoes C(aryl) Br oxidative addition, alkene insertion, β-N group elimination, and nitrogen protonation. The C H activation of Et3N, which is requisite for nitrogen protonation, was explored emphatically. An ion-pair intermediate containing both an anionic Pd(II) complex (a 16e 4-coordinate square planar structure) and a cationic moiety Et2N CHCH3+ was found to be involved in the C H activation. The nitrogen atom of Et3N plays a crucial role in stabilizing the cationic moiety by means of its lone pair to afford a N C double bond, and thus ruling out the possibility of the β-C H bond activation. Additionally, the high chemoselectivity for P1 rather than P2 and P3 were rationalized theoretically.

Terminal alkenes were selectively cleaved into ketones and aldehydes catalyzed by a binuclear copper catalyst bearing a simple salicylate ligand with O2 as the oxidant. The reaction was carried out under an atmosphere of O2 (balloon) with 0.5 mol% of catalyst and could be performed on a gram scale, providing a convenient and practical method for the cleavage of terminal alkenes into carbonyl compounds.

We report on a dual ratiometric two-photon fluorescent probe for in situ sensing of mitochondrial CE activity and pH. Using the probe it is possible to visualize the CE-mediated acidification of hepatoma cells and hepatic tissues during medication with antipyretic anti-inflammatory drugs.

The Rh(III)-catalyzed oxidative coupling of oxime ether (S1) and cyclopropanol (S2) with Cu(II) as the oxidant features the combination of C-H activation and strained ring opening. The sequential order of C-H activation versus ring opening was investigated with the aid of density functional theory calculations. Prior ring opening due to the release of ring strain is found to be favored over the prior C-H activation. For the prior ring-opening mechanisms, the outer-sphere concerted metalation-deprotonation (CMD) mechanism in C-H bond activation is energetically favored. The outer-sphere CMD mechanism proposed in this work favors solvent effects and affords the N→Rh binding that allows a directing role of the Schiff base group. In conclusion, the reaction was suggested to undergo prior ring opening followed by C-H activation via the outer-sphere CMD mechanism.

As one of the most prospective transitional metal oxide cathode materials for sodium-ion batteries (SIBs), P2-type Na2/3Ni1/3Mn2/3O2 layered oxide generally suffers from sluggish Na+ kinetics and complicated structural evolution. Here, a stable Co-free P2-Na2/3Li1/9Ni2/9Mn2/3O2 cathode material with multilayer oriented stacking nanoplates is reported, which exhibits high hydrostability realized by partial Li element substitution for Ni. A prominent rate capability (71.7% capacity retention at 5 C compared to 0.2 C), an excellent cycling stability (78.7% capacity retention at 2 C after 300 cycles) and a promoted performance even at a higher cutoff potential of 4.4 V were displayed owing to bifunctional strategy of chemical substitution coupled with structure modulation, and the as-synthesized material retains its original structure and electrochemical performance after being aged in water. Moreover, dominant Na+ capacitive storage mechanism, high thermostability and complete solid-solution reaction are explicitly elucidated through quantitative calculation of electrochemical kinetics and in-situ X-ray diffraction technique. These findings reveal the importance of rational chemical substitution and structure modulation strategy, and inspire novel design of high-performance cathode materials for rechargeable SIBs.

As a safe and sustainable cathode material for reversible Na-ion storage, the electrochemical performance of Na3.32Fe2.34(P2O7)2 with high operational safety can be enhanced via ion-doping engineering strategy. However, the rationale behind has remained unclear. In this study, we partially replace the Na+ and Fe2+ cations with K+ and Mg2+, respectively, where the K+ and Mg2+ dopants serve as pillars to support the crystallographic framework and thus reduce potential hysteresis. It is found that, compared to K doping at the Na site, Mg doping at the Fe site contributes to a more stable crystal structure and renders higher rate capability and cycling stability due to the inhibition of Fe migration and the reduction of structural disorder. The cation pillar strategy reported herein may shed light on enhancing cycling performance of other cathode materials for stable storage of not only Na ions but also other metals.

Due to the highest theoretical specific capacity of 4200 mA h g−1 for Li4.4Si, silicon(Si)-based materials could fulfill the increasing demands of high-energy lithium-ion batteries (LIBs). However, the intrinsic huge volume expansion during the lithiation/delithiation process results in rapid capacity decay and short cycle life and restricts the satisfactory electrical performance of Si-based anodes. Binder plays an important role of maintaining the contact integrity between active material, conductive additive and the current collector, thereby reducing the pulverization of the Si particles during charge/discharge. Here, the review systematically summarizes the synthesis methods, design principles and working mechanisms, including chemical composition, superstructure, and various interactions between different functional moieties of synthetic binders and natural biomass binders, to reveal the structure-composition-performance relationship, offer practical solutions to challenging problems associated with defects of Si-based electrode materials in LIBs and aim at exploiting new family of binders that could be used in industrial level as well as providing design principles for other electrode binders in rechargeable batteries.

The storage of renewable energy depends largely on sustainable technologies such as sodium-ion batteries with high safety, long lifespan, low cost, and non-toxicity. Pyrophosphate Na3.32Fe2.34(P2O7)2 cathode could meet this requirement, however, its structural stability needs to be further enhanced for practical purposes. To overcome this problem, Na-deficient Na3.32Fe2.11Ca0.23(P2O7)2 with exceptional stability is prepared by Ca selective doping in this work. In operando synchrotron-based X-ray diffraction (SXRD) and in situ X-ray absorption near edge spectroscopy (XANES) results reveal that the prepared Na3.32Fe2.11Ca0.23(P2O7)2 is a single-phase solid-solution reaction with high reversibility. A strong correlation between the voltage curve and lattice parameters is deciphered for the first time. Additionally, the atomic-doping-engineering strategy could significantly enhance the thermal and electrochemical stability of the electrode materials, contributing to their good structural reversibility and enhanced operational safety. Specifically, after 1000 cycles at 1 C, the Ca doped electrode achieves a high capacity retention of 81.7%, which is much better than that of the un-doped electrode (15.5%). Our work may pave a new avenue for designing safe and low-cost cathode materials for battery applications with long cycle life.

One of the most prevalent forms of dementia is Alzheimer's disease (AD) which causes severe memory impairment within humans. As such, research into the early diagnosis of AD is essential to help treatment, which has led to significant advances in fluorescence imaging. Unfortunately, modern medicine and biology place increasingly strict requirements for fluorescent probes. Therefore, over recent years, researchers have taken strides to develop novel fluorescent molecular probes, with properties suitable for modern clinical applications, including low phototoxicity, weak background interference, deep tissue penetration, enhanced specificity, strong binding affinity, and suitable permeability through the blood–brain barrier (BBB). From these recent research results, many novel concepts for molecular design and fluorescence techniques have emerged. Herein, we present strategies towards the development of probes capable of meeting the advanced clinical requirements. As part of this review, we will summarize the characteristic enzymes and proteins involved in AD progression, including Amyloid-β, β-secretase, tau protein, monoamine oxidases, and methionine sulfoxide reductase. Then, we will evaluate some of the early probes and summarize the recent advancements made in the design of probes suitable for clinical applications, from which several strategies have emerged, such as increasing permeability to the blood–brain barrier, enhancing specificity by boosting binding affinity, and improving optical properties for in vivo imaging, etc. Then to conclude current strategies for early stage diagnosis of AD will be presented, and the opportunities as well as the remaining challenges will be outlined.

Gold-catalyzed cyclization of 2-alkynyl-N-propargylanilines provides a step-economic method for the construction of three-dimensional indolines. In this article, the M06 functional of density functional theory was employed to gain deeper insights into the reaction mechanism and the associated intriguing experimental observations. The reaction was found to first undergo Au(I)-induced cyclization to form an indole intermediate, 1,3-propargyl migration, and substitution with the substrate 2-alkynyl-N-propargylaniline (R1) to generate the intermediate product P1, an allene species. Subsequently, Au(I)-catalyzed conversion of P1 into the final product P2, an indoline compound, occurs first through direct cyclization rather than via the previously proposed four-membered carbocycle intermediate. Thereafter, water-assisted oxygen heterocycle formation and proton transfer generate the final product. The calculated activation free energies indicate that P1 formation is 5.9 times slower than P2 formation, in accordance with the fact that P1 formation is rate-limiting. Futhermore, the intriguing experimental phenomenon that P2 can be accessed only after almost all the substrate R1 converts to P1 although P1 formation is rate-limiting was rationalized by employing an energetic span model. We found the initial facile cyclization to form a highly stable indole intermediate in the formation of P1 is the key to the intriguing experimental phenomenon.

With the aid of density functional theory (DFT) calculations, the Pd-catalyzed reactions of aryl iodide with unsymmetrical alkyne leading to two products containing C(sp 3 )−I bond ( P3 and P4 ) and one product containing a three-membered carbocyclic unit ( P5 ), have been studied theoretically. It is found that both the alkyne insertion and the subsequent C C bond insertion involved in the reaction are the major thermodynamic driving forces. The alkyne insertion instead of the C(sp 3 )−I reductive elimination is predicted to be rate-determinant. Similar barrier heights calculated for the two insertion modes of unsymmetrical internal alkyne ( TS 3-4 and TS 3′-4′ ) lead to the products P3 (47.2%) and P4 + P5 (48.8%) having similar product yields. The intriguing formation of the product containing a three-membered carbocyclic unit ( P5 ) was investigated in details. The second alkene insertion is found to be kinetically more favored than the C(sp 3 )−I reductive elimination, leading to product P5 (39.0%) more productive than P4 (9.8%). The remarkably thermodynamically favored β−H elimination is the key factor enabling formation of P5 . Why significant bulky phosphine ligand such as P(t-Bu) 3 instead of small one such as P(Me) 3 was employed experimentally have also been rationalized based on our calculation results.

Pd-catalyzed decarboxylative Heck-type coupling of 3-chlorobenzo[b]thiophene-2-carboxylic acids with styrenes have been developed as an efficient strategy for the construction of functionalized benzo[b]thiophenes. Theoretical analysis shows that AgCl generated during the reaction, instead of Pd, π-coordinates with the carboxyl O atom, making easy the rate-determining CO2 dissociation. The divergent reactivities of the Cl-substituted and H-substituted 3-benzo[b]thiophene-2-carboxylic acids are mainly due to the presence of the Cl substituent, which reduces the adjacent π-π interplay, thereby significantly contributing to decarboxylation. Therefore, the presence of both AgCl and the Cl substituent are of key importance in ensuring the occurrence of the reaction under the given conditions.

A theoretical and computational study was performed on the nitrene-participating three-component carboamination of dienes. The reaction proceeds mainly through C–H activation, olefin insertion, metal nitrenoid formation, and selective C N coupling. The role of solvent effect enables the extrusion of carbon dioxide to generate the key metal nitrenoid being not concerted but stepwise. The Rh = N was indicated by HOMO-LUMO interactions that the backdonation is dominant and hence showing the electron withdrawing behavior of nitrene. Regioselectivity for C C bond formation, E-type product, and 1,4-carboamination was discussed.

Layered manganese oxides cathodes of sodium-ion batteries show high energy density, but limited stability and rate capacity. Our previous studies have evidenced that layer-tunnel hybrid structure possesses both better rate performance and cyclic stability. Nevertheless, the complex phase transition is still ineluctable, leading to unsatisfying cycling performance. Be different from the previous study of ion-doping, this study demonstrates that the highly Na+-conductive Na2Ti6O13 coating can also effectually suppress the phase transition and improve the structure stability, air stability. Notably, the 3 wt % Na2Ti6O13 coated sample exhibits a primary capacity of 175.6 mA h g−1at 0.1 C between 2.0 and 4.1 V. And a capacity retention of 86.7% at 2C after 100 cycles. The Raman results show that the local lattice distortion around Mn3+ and Mn4+ ions is effectively suppressed. And the air stability also has been significantly improved. This study could provide a valid tactics into the surface modification of high-performance composite structure cathode materials for SIBs.

Polymer-ceramic composite electrolyte is an effective solution for developing high-performance and flexible all-solid-state lithium metal battery. However, the key bottleneck of composite electrolyte including low ionic conductivity and high interfacial impedance have impeded their industrialization in solid electrolyte lithium batteries. Here we present a polymer-ceramic hybrid electrolyte (polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF)/Li6.4La3Zr1.4Ta0.6O12 (LLZTO)) is designed and modified by trace amount of liquid electrolyte. The addition of PVDF can not only reduce the crystallinity of PEO polymer, but also intensify the affinity between liquid electrolyte and the composite electrolyte. Furthermore, the interfacial modification can synchronously achieve the intimate connection, low interfacial impedance between the electrodes and solid electrolytes by forming the viscoelastic and stable layer. Due to the artful design, the solid-state battery deliver excellent performance. The Li symmetric cells show excellent interface stability without short circuits for 1000h. The assembled LiFePO4/Li cells exhibit a discharge capacity of 160.1 mA h g−1 after 200 cycles at 0.4C and 143.3 mA h g−1 at 5C. The composite solid electrolyte provides an effective and feasible methods to solve the interfacial issues and develop high performance solid lithium metal batteries.

Li- and Mn-rich layered cathode materials (LMR) have been widely studied for their ultrahigh energy density. Unfortunately, the rapid potential decay and capacity degradation during cycling hinder their commercialization process. In this work, Mg2+ cation and PO43− polyanion dual elements coupling effect induced lattice modification strategy is developed to address these drawbacks for a typical lithium-rich material. The structural characteristic, chemical composition, valence state and elemental distribution of the materials are investigated by scanning electron microscopy, X-ray diffraction, inductively coupled plasma optical emission spectroscopy, focused ion beam and high-resolution transmission electron microscopy, respectively. Mg2+ and PO43− co-modified lithium-rich cathode material shows excellent electrochemical properties. It provides an improved initial coulombic efficiency of 87 % and ultrahigh initial discharge capacity of 307 mA h g-1 during a cut-off voltage of 2.0–4.8 V and a current density of 25 mA g-1. In conclusion, the Mg2+ and PO43− co-modified material exhibits not only significantly improved rate performance (150.7 mA h g−1 @ 5 C) but also markedly improved cycling stability (83 % @ 1 C @ 300 cycles).

Although the properties of high energy density and low costs have contributed the extensive research of Lithium-rich layered oxide materials as a candidate of next-generation cathode materials in lithium-ion batteries, present poor cyclic life, and fast voltage fade hinder their large-scale commercial applications. Here, we propose a novel cation/anion (Na+/PO43-) co-doping approach to mitigate the discharge capacity and voltage fade of Co-free Li1.2Ni0.2Mn0.6O2 cathode. Results show that the synergistic effect of cation/anion can obviously promote the long cycle stability and rate performance by inhibiting the phase transformation of layered structure to spinel or rock-salt structure and stabilizing the well-order crystal structure during long cycle. The co-doped sample exhibits an outstanding cycle stability (capacity retention of 86.7% after 150 cycles at 1 C) and excellent rate performance (153 mAh g−1 at 5 C). The large ionic radius of Na+ can expand the Li slab for accelerating the Li diffusion and the large tetrahedral PO43- polyanions with high electronegativity stabilize the local structure for improving the electrochemical performance.

Mass spectrum (MS) is one of the most commonly used tools for qualitative and quantitative analysis of glycans. However, due to the complexity of biological samples and the low ionization efficiency of glycans, these need to be purified and derivatized prior to MS analysis. Existing purification strategies require a combination of multiple methods and are cumbersome to operate. Here, we propose a new method for the purification of glycoprotein N/O-glycans and their derivatives using a hand-packed absorbent cotton hydrophilic interaction chromatography column (HILIC). The method's reliability and applicability were verified by purifying N/O-glycans and the derivatives of standard glycoproteins, such as chicken albumin and porcine stomach mucin. Stable isotope labelling was used to compare the glycans’ recovery following different purification methods. Absorbent cotton HILIC was also successfully applied for the analysis of human serum and fetal bovine serum glycoprotein N-glycans. Finally, testing revealed high binding capacity (9 mg/g−1 maltohexaose/absorbent cotton) and good recovery (average recovery was 91.7%) of glycans. Compared with traditional procedures, the proposed purification method offers considerable advantages, such as simplicity, high efficiency, economy, universality, and broad applicability for the pretreatment of glycans and their derivatives in biological samples prior to MS analysis.

Density functional theory (DFT) calculations were used to explore the Au(I)-catalyzed selective [4 + 1] annulations of cyclopropyl- and H-substituted 1,4-diyn-3-ols with isoxazole. The results indicated that after the N-nucleophilic attack of isoxazole, instead of obtaining the α–hydroxy gold carbene intermediate proposed experimentally, a concerted three-step forward product by isoxazole O[sbnd]N cleavage, 1,2-phenylalkyne shift and the hydroxyl H shift was identified as the key intermediate, for the reaction proceeding either via an Au-assisted C[dbnd]C double-bond rotation to produce the Z-isomeric enone or via two different Au-assisted C[dbnd]C rotations to furnish the E-configured enone depending on the substituents used. Further theoretical investigations indicated that the chemoselective step is the nucleophilic cyclization but not the C[dbnd]C double-bond rotation. The chemoselective preference for the Z-configured product using the cyclopropyl substitutent was attributed to two factors: i) the additional O[tbnd]H[sbnd]N hydrogen bonding interaction stabilizes the rate-determining cyclization TS leading to the Z-product, and ii) further Z-E product-isomerization is blocked due to significant structural deformation being involved. In contrast, using the H substituent results in a reversed chemoselectivity with exclusive formation of the E-configured enone, which is closely related to the smaller entropy effects involved.