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Field experiments of nitrogen (N) treatment at five different application rates (0, 75, 150, 225, and 300 kg ha−1) were conducted under pot-seedling mechanical transplanting (PMT) in 2018 and 2019. Two high-quality and high-yielding hybrids of indica rice, Huiliangyou 898 and Y Liangyou 900, were used in this study. The N nutrition index (NNI) and accumulated N deficit (Nand), used to assess the N nutrition status in real-time, were calculated for the indica cultivars under PMT with a critical nitrogen concentration (Nc) dilution model based on shoot dry matter (DM) during the whole rice growth stage. The relationships between NNI and Nand with relative yield (RY) were determined, and accurate N application schemes were developed for hybrids indica rice under PMT. The results indicated that high application rate of N-fertilizer significantly increased the concentrations of shoot DM and N in aboveground organs during the observed stages in the two cultivars for two years (P

Anaerobic methane oxidation is coupled to the reduction of electron acceptors, such as sulfate, and contributes to their biogeochemical cycling in the environment. However, whether arsenate acts as an alternative electron acceptor of anaerobic methane oxidation and how this influences global arsenic transformations remains elusive. Here, we present incubations of arsenate-contaminated wetland soils from seven provinces in China. Using isotopically labelled methane, we find that anaerobic methane oxidation was linked to arsenate reduction at a rate approaching the theoretical arsenic/methane stoichiometric ratio of 4. In microcosm incubations with natural wetland soils, we find that the coupled pathway of anaerobic methane oxidation and arsenate reduction contributed 26 to 49% of total arsenic release from soils, with arsenic in the more soluble and toxic form arsenite. Comparative gene quantification and metagenomic sequencing suggest that the coupled pathway was facilitated by anaerobic methanotrophs, either independently or synergistically with arsenate-reducing bacteria through reverse methanogenesis and respiratory arsenate reduction. Further bioinformatic analyses show that genes coding for reverse methanogenesis and respiratory arsenate reduction are universally co-distributed in nature. This suggests that coupling of anaerobic methane oxidation and arsenate reduction is a potentially global but previously overlooked process, with implications for arsenic mobilization and environmental contamination. The coupling of anaerobic oxidation of methane and arsenate reduction is an important pathway of releasing arsenic from soils, according to incubation experiments of arsenate-contaminated wetland soils.

Li-rich layered oxides (LLOs) are promising cathodes for lithium-ion batteries because of their high energy density provided by anionic redox. Although great improvements have been achieved in electrochemical performance, little attention has been paid to the energy density stability during fast charging. Indeed, LLOs have severe capacity fading and voltage decay especially at a high state of charge (SOC), disabling the application of the frequently used constant-current-constant-voltage mode for fast charging. Herein, we address this problem by manipulating the external electric field and tensile strain induced by lattice expansion effect in nanomaterials under the guidance of theoretical calculations, which indicate that LLOs at high SOC have almost a zero band gap and a low oxygen formation energy. This strategy will weaken polarization, stabilize lattice oxygen, and restrict phase transition simultaneously. Thus, the energy density during fast charging can be highly stabilized. Therefore, it may be of great value for the practical application of layered cathodes.

An Ugi, novel pseudo-Knoevenagel, ring expansion cascade reaction was discovered and utilized for the synthesis of aziridinyl succinimides in one-pot. Subsequently, densely functionalized aziridines and maleimides have been designed and synthesized through similar cascade reactions. The target compounds were prepared by means of a mild reaction and a simple operation procedure, which could be applicable to a broad scope of starting materials. This series of novel cascade reactions generates opportunities for the tailored synthesis of a wide range of biologically active scaffolds through tuneable Ugi inputs. Discovery of compound 8i with comparable potency to sorafenib in liver cancer cell lines could provide a new avenue for liver cancer drug discovery.

Li metal anodes are undergoing a renaissance due to their ultra-high specific capacity and the lowest reduction potential. However, the practical application of Li-metal anodes is still challenged by Li dendrite growth and low coulombic efficiency (CE). Herein, a gradient Si-modified carbon paper (GSCP) made via magnetic sputtering is proposed to address these issues, in which the content of lithiophilic Si gradually decreases from the bottom to the top of the 3D host. Such a gradient lithiophilic structure can cause the Li metal to selectively nucleate and grow at the bottom first and then to the top part of GSCP, realizing stable Li plating/stripping and high space utilization of the 3D host simultaneously. Therefore, the designed GSCP composite anode achieves average CEs of 99.0% (400 cycles) and 97.0% (150 cycles) at 1 and 5 mA cm−2, respectively, and a prolonged lifespan (1350 h) with a low overpotential (∼15 mV). Remarkably, the GSCP@Li‖Li4Ti5O12 full cell exhibits high capacity retention of 84.5% after 5000 cycles at a 10C rate.

The electronic and optical properties of graphane, silicane and MoS2 bilayers, as well as the graphane/MoS2 and silicane/MoS2 hetero-bilayers, are calculated by the first-principles method. The interlayer interactions of all the bilayer systems are shown to be mainly van der Waals. Both the graphane/MoS2 and silicane/MoS2 hetero-bilayers belong to the type-II heterostructure, which can be utilized in photo-voltaic devices due to the efficient spatial separation of electrons and holes. For optical properties, the distinctions for the imaginary parts of the dielectric function e 2 ( ω ) between the monolayer and bilayer systems for both the graphane and silicane are more evident in electric vector E||z. However, the differences between e 2 ( ω ) of the monolayer and bilayer MoS2 materials are more significant in E||x. Broader light absorption ranges of the hetero-bilayers are reached, which can also improve the charge separation of the electron-hole pairs.

By performing the first-principles calculations, we explore the dissolution and diffusion of hydrogen (H) in hexagonal closed packed zirconium (Zr) as well as its interaction with vacancy. We show that the tetrahedral (TE) interstitial site is the favorable trapping site for a single H atom with the solution energy of −0.45 eV. Such a negative solution energy is due to the strong electronic bond between H and neighboring Zr atoms. Moreover, the energy barrier for the migration of H from a TE site to its 1NN and 2NN TE site is 0.12 eV and 0.42 eV, respectively. It is noteworthy that the first path only slightly contributes to the experimentally measured H diffusivity in Zr, because the H atom is trapped by two nearest neighboring TE sites. Thus, the effective activation energy for H diffusion in Zr should be mainly determined by the second path, and the corresponding energy barrier is 0.42 eV. Furthermore, since the electronic density (available volume) in vacancy is lower (larger) than that of interstitial site, vacancy is a strong trap for H atoms in Zr. We demonstrate that the maximum of 8 H atoms can be accommodated in a mono-vacancy without the observation of H2 molecule. These results can provide a basis to develop Zr materials in nuclear cladding devices.

The short operation lifetime is a major factor which hinders the large-scale commercialization of phosphorescent organic light-emitting diodes (OLEDs). Unveiling the intrinsic degradation mechanism of phosphorescent material may be a feasible method for exploring the determined factors of operation lifetime. In this article, the ligand dissociation reactions and phosphorescent quantum yields of various bidentate Pt (II) complexes were investigated by means of the density functional theory (DFT) and time-dependent (TD)-DFT. The calculated results indicate for phosphorescent quantum yields, sulphur heterocycle can facilitate the radiative decay process and suppress the temperature-dependent nonradiative channel. In the aspect of ligand dissociation reactions, the corresponding dissociations of Pt (II) complexes can be effectively avoided via changing the coordinate forms of ligands. In addition, the relationship between geometric tailor and stability, emission color was also taken into account. An analysis of computed results can conclude that the electron-withdrawing and electron-dominating substituents can tune the emissive wavelengths from 477 to 624 nm and cause minor effect on the stability. This investigation could some meaningful information for designing stable Pt (II) complexes.

Li-rich layered oxides have been in focus because of their high specific capacity. However, they usually suffer from poor kinetics, severe voltage decay, and capacity fading. Herein, a long-neglect...

A type of rock landslide is very common in practical engineering, whose stability is mainly controlled by the rock bridge between the steep tensile crack at the crest and the low-inclination weak discontinuities at the toe (namely, ligament is the term for the locking section in the slope). To obtain a deeper understanding into the failure process of this kind of landslide, twenty-four physical slope models containing a steep-gentle discontinuity pair (a steep crack in the upper part and a low-inclination discontinuity in the lower part) were tested by applying vertical loads at the crests. The results indicate that the inclination angle of the ligament (θ) has great influence on the failure and stability of this type of rock slope. With the change of θ, three failure patterns (five subtypes) concerning the tested slopes can be observed, i.e., tensile failure of the ligament (Type 1), tension-shear failure of the ligament (Type 2) and two-stage failure of the main body (Type 3). The failure process of each failure mode presents five stages in terms of crack development, vertical load, horizontal/vertical displacements and strains in the ligaments. The specific range of the ligament angle between different failure patterns is summarized. The discussion on the failure resistances and ductility of different failure patterns, and the guiding significances of the experimental findings to the stability evaluation and the reinforcement were conducted.

Exploration of Li-rich transition-metal (TM) oxides with active anionic redox reaction has paved a promising way for the design of high-capacity Li-ion battery cathode materials. In the present wor...

Li-rich layered oxides (LRLO) with high specific capacity over 250 mA h g−1 are attractive cathode material candidates for the next-generation high performance lithium-ion batteries. However, LRLO always suffers from low initial Coulombic efficiency, poor cycling and rate properties. Herein, unique double-shell LRLO hollow microspheres with sandwich-like carbon@spinel@layered@spinel@carbon shells (LRLO-500@S@C) were successfully synthesized via a facile template-free method, followed by carbothermal reduction treatment. The fabricated LRLO-500@S@C cathode delivers a high initial charge capacity of 312.5 mA h g−1 with a large initial Coulombic efficiency of 89.7%. After cycling 200 times, large and stable discharge capacities of 228.3 mA h g−1 and 196.1 mA h g−1 can be obtained at 1.0 C and 5.0 C, respectively. Moreover, coin-type full cell with LRLO-500@S@C as cathode and Li4Ti5O12 as anode delivers outstanding lithium storage properties. The impressive electrochemical performances of LRLO-500@S@C cathode material can be attributed to its multiscale coordinated design based on hierarchical double-shell hollow construction, the special layered@spinel@carbon heterostructured shells and the introduced oxygen vacancies, which benefit to shorten Li-ion diffusion paths, strengthen structural stability and reduce side reactions.

Lattice oxygen activity plays a dominant role in balancing discharge capacity and performance decay of lithium-rich layered oxide cathodes (LLOs). On the basis of density functional theory (DFT) and tight-binding theory, the activity of lattice oxygen can be improved by tensile strain and suppressed by compressive strain. To verify this conclusion, LLOs with large lattice parameters (L-LLOs) were synthesized taking advantage of the lattice expansion effect in nanomaterials. Compared with conventional LLOs with small lattice parameters (S-LLOs), particles in L-LLOs are imposed by tensile strain. L-LLOs show a larger initial discharge capacity and decay faster in the prolonged cycles than S-LLOs. Actually, most of the modified methods in LLOs can come down to strain-induced changes in lattice parameters. We believe this conclusion is a useful guideline to understand and tailor the lattice oxygen activity and may be generalized to other layered oxide cathodes involving anionic redox.

Recently, the square planar ${\mathrm{MoS}}_{2}$ monolayer, which exhibits the Cairo pentagonal tiling (termed as $1\mathrm{P}\text{\ensuremath{-}}{\mathrm{MoS}}_{2}$), was identified as an intrinsic quantum anomalous Hall (QAH) insulator. However, there is a paucity of theoretical work concerning a suitable substrate to support its nontrivial electron transport properties, which is the prerequisite for practical applications. Here. we demonstrate that CuI(001) serves an excellent substrate candidate for epitaxial growth of the $1\mathrm{P}\text{\ensuremath{-}}{\mathrm{MoS}}_{2}$ sheet by showing that the intrinsic ferromagnetism and the QAH state of $1\mathrm{P}\text{\ensuremath{-}}{\mathrm{MoS}}_{2}$ remain unaltered in the $1\mathrm{P}\text{\ensuremath{-}}{\mathrm{MoS}}_{2}$/CuI(001) system. Further analyses of the strain effect on $1\mathrm{P}\text{\ensuremath{-}}{\mathrm{MoS}}_{2}$ reveal that the QAH is robust within a strain range from $\ensuremath{-}$ 2% to 2%. Our findings will inspire the experimental realization of QAH effects in two-dimensional (2D) pentagon-based materials.

One-dimensional (1D) selenium and tellurium crystalize in helical chainlike structures and thus exhibit fascinating properties. By performing first-principles calculations, we have researched the linear and nonlinear optical (NLO) properties of 1D Se and Te, and find that both systems exhibit pronounced NLO responses. In particular, 1D Se is found to possess a large second-harmonic generation coefficient with the χ value being up to 7 times larger than that of GaN, and is even several times larger than that of the bulk counterpart. On the other hand, 1D Te also produces significant NLO susceptibility χ which exceeds that of bulk GaN by 5 times. Furthermore, 1D Te is shown to possess a prominent linear electro-optic coefficient rxxx(0). In particular, the Te chain exhibits a large shift current response and the maximum is twice as large as the maximal photovoltaic responses obtained from BaTiO3. Therefore, 1D Se and Te may find potential applications in solar energy conversion, electro-optical switches, and so on. Finally, the much stronger NLO effects of 1D Se and Te are attributed to their one-dimensional structures with high anisotropy, strong covalent bonding and lone-pair electrons. These findings will contribute further to experimental studies and the search for excellent materials with large NLO effects.

The mechanism and charge effect of cycloisomerization of ω-alkynylfuran (Hashmi phenol synthesis) catalyzed by single-walled helical gold nanotubes (Au SWNTs) have been systematically investigated via density functional theory. Cycloisomerization of ω-alkynylfuran occurs by the 5-exo Friedel–Crafts-type (FCT) mechanism, namely 5-exo cyclization, furan ring opening, and ring closing of the dienone carbene–gold intermediate. The reactions with Au(6,0), Au(6,1), Au(6,2) and Au(6,3) SWNTs show low energy barriers along the 5-exo FCT path in acetonitrile solvent, but have different the rate-determining steps. From an energy perspective, the reaction rate-determining step catalyzed by Au(6,0) and Au(6,3) is the ring-closing of dienone carbine-gold intermediate, but that of Au(6,1) and Au(6,2) is the IM5 dissociation from the Au SWNTs, which can be attributed to the diversity of the d-band centers of the Au(6,m) SWNTs. The effect of the charge of the Au SWNTs on the catalytic activity was also investigated. Theoretical analysis shows a prominent charge effect, where the cationic Au(6,0), Au(6,3) SWNTs and anionic Au(6,1), Au(6,2) SWNTs are more favorable for the Hashmi phenol synthesis reaction. This results can be attributed to the Au(6,0) and Au(6,3) SWNTs with positive charge can reduce the adsorption energy of the substrate on the catalyst surface and decrease the energy barrier of the cyclization process and ring-closing step. Besides, the Au(6,1) and Au(6,2) with an anion could obviously decrease the dissociation energy of IM5 which is help for the Hashmi phenol reaction. Theoretical analysis shows that the structure and charge effects could influence the catalytic activity of Au(6,m) SWNTs toward Hashmi phenol synthesis. This work will provide insight into cycloisomerization of ω-alkynylfuran and valuable information for application of Au SWNTs in catalysis.

The importance of martensitic transformations has led to tremendous efforts to explore the microscopic martensitic transition paths. There are five possible transformation paths (for γ → α transition) known for Fe at present, and at an arbitrary activation energy, any of the five paths might be followed. It then becomes considerably difficult to monitor the microscopic phase transition mechanism in experiments. Therefore, it is helpful to realize only one of the paths in a physical process. Based on first-principles calculations, we show that at suitable activation energies the Nishiyama–Wassermann (N–W) transformation path can be realized without the involvement of the Bain path, since the condition ENW(θ) < E < EBain can be satisfied by pure Fe. E is the activation energy of the system, and ENW(θ) and EBain are the energy barriers for the N–W and Bain transformations, respectively. In particular, the potential energy surface (PES) for the N–W transformation has been calculated as being four-dimensional, i.e., E = E(a,b,c,θ), where (a, b, c) are the lattice constants and θ is the shear angle involved in the shear distortion of the N–W path.

Molecular cages have attracted great attention because of their fascinating topological structures and well-defined functional cavities. These discrete cages were usually fabricated by coordination assembly approach, a process employing directional metal-ligand coordination bonds due to the nature of the divinable coordination geometry and the required lability to encode dynamic equilibrium/error-correction. Compared to these coordination molecular cages with mononulcear metal-nodes, an increasing number of molecular cages featuring dinuclear and then polynuclear metal-cluster nodes have been synthesized. These metal-cluster-based coordination cages (MCCCs) combine the merits of both metal clusters and the cage structure, and exhibit excellent performances in catalysis, separation, host-guest chemistry and so on. In this review, we highlight the syntheses of MCCCs and their potential functions that is donated by the metal-cluster nodes.

Understanding the mechanism of the catalytic reaction is an effective way to design new high-performance catalysts. The mechanisms of alkyne/olefin hydrogenations catalyzed by a nonclassical Co–N2 ...

Understanding the mechanism of a catalytic reaction is of fundamental importance not only scientifically but also technologically to the design of high-performance catalysts. In this work, the mechanisms of 1-phenyl-1-propyne and cis-β-methylstyrene hydrogenations catalyzed by Cu55 and ligand-coated Cu55 are explored in detail by means of density functional theory (DFT). The calculated results indicate that the semihydrogenation selectivity of the catalyst can be effectively controlled by employing a suitable ligand. That is, the PCy3 and PPh3 ligands used to coat Cu55 can largely raise the energy barrier of the rate-determining step for cis-β-methylstyrene hydrogenation. By the study of energy decomposition analysis (EDA) and charge density difference, it can be found that the deformation energies of the substrate fragments play a crucial role in the energy barriers of the rate-determining steps. The large hindrance effect of the ligands is beneficial for improving the semihydrogenation selectivity of the catalysts. This study provides significant information for future catalyst design and on the physical origin of the phosphine ligand-coated nanoparticle catalysis for semihydrogenation.

The first catalyst-free post-Ugi cascade methodology was developed for expeditious access to structurally diverse and complex pyrazole-pyrazines in one-pot. This novel cascade reaction features an intramolecular N2-arylation of pyrazoles with allenes at the C-β position of triple bond. Screening in the colorectal cancer cell lines HCT116 and SW620 validated the feasibility of the methodology for generating bioactive compounds. The lead compound 7h which is active against HCT116 and SW620 with IC50 of 1.3 and 1.8 µM, respectively, can be synthesized and purified in a gram process synthetic scale in 7 hours. The mechanical studies indicated that compound 7h can induce cell cycle arrest in the G2/M phase and inhibit proliferation and viability in human colon cancer cells. Overall, compound 7h is represented as a promising starting point for the development of new anti-colorectal cancer drugs.

LiCrO2 and NaCrO2 have been well-studied as cathode materials in lithium and sodium ion batteries, while the studies on LiCrS2 and NaCrS2 are relatively rare. In this work, a comparative study on the electronic structures and redox reactions in oxides (LiCrO2, NaCrO2) and sulfides (LiCrS2, NaCrS2) is performed. A first-principles method has been used to calculate the Bader charge transfer, the electronic structures and the magnetic moments during the entire delithiation or desodiation process. The Bader charge analysis suggests that all the S, O and Cr ions in LiCrX2 and NaCrX2 participate in the redox reactions, where the loss of electrons of S ions is clearly larger than that of O ions. Besides, the redox processes of Cr ions are of much less significance. It is noted that, in the sulfides, Cr ions even gain a small portion of electrons rather than losing electrons during the extraction of Li/Na ions. All the charge transfer happens between the S-3p/O-2p and the Cr-3d bands. The redox reactions of O or S ions originate from the energy levels of O/S being pushed towards/across the Fermi surface due to the strong p–d hybridization.

For phosphorescent emitters, the rigidity of the geometry is a crucial indicator, which can directly determine the non-radiative decay rate. In this article, density functional theory (DFT) calculations were performed to investigate the influence of the small substituent groups on the rigidities of tridentate Pt(ii) complexes in detail. The calculated results indicate that the small substituent groups can serve as geometric controllers to suppress the structural distortion on going from the ground state (S0) to the lowest-lying triplet excited state (T1) (Jahn-Teller distortion). For instance, when electron-donating substituent groups, including -NH2, -N(CH3)2 and -OCH3, were employed, the rigidities of the corresponding Pt(ii) complexes can be effectively enhanced because the highest occupied molecular orbital (HOMO)-HOMO-1 energy gaps could be increased. Different from the electron-donating substituent groups, electron-withdrawing substituent groups, i.e., -NO2 and -COCH3, can cause a negligible change in HOMO and HOMO-1 energies during the S0 → T1 transition process, and therefore, for Pt-NO2 and Pt-COCH3, no Jahn-Teller distortion occurs. According to the calculated results, the rigidities of tridentate Pt(ii) complexes could be raised via tuning the energies of the frontier molecular orbital (FMO) with the help of small substituent groups.

Removal of NO and Hg0 simultaneously was achieved on Nb-modified MnTiOx catalyst. Experimental results revealed that high NO conversion (>95%) and Hg0 oxidation (>95%) in 200–300 °C were available on Mn0.15Nb0.02TiOx catalyst with a GHSV of 108,000 h−1. The excellent catalytic performance of Mn0.15Nb0.02TiOx catalyst should be originated from its high reducibility and massive surface chemisorbed oxygen species. Moreover, the introduction of Nb into MnTiOx catalyst greatly enhanced its resistance to SO2 and H2O. Neither gaseous Hg0 nor HgO formed on catalyst surface could affect the NH3-SCR reaction. NO had a promotion effect on Hg0 oxidation, while NH3 was detrimental to Hg0 oxidation owing to the inhibited adsorption of Hg0 by NH3. Under SCR reaction conditions, an inhibition impact on Hg0 oxidation could be detected, but this negative effect could be avoided by using more catalyst sample.

Unveiling the reaction mechanism is significant for developing high-performance catalysts. In this paper, a series of precisely controlled PdxM147-x (M = Cu, Pt, Au, Rh, Ru) dendrimer encapsulated nanoparticles (DENs) has been successfully synthesized. The mechanisms of PdxM147-x as catalysts for Suzuki cross-coupling reactions were investigated by combining experimental and theoretical methods. The experimental results indicate that Pd74Cu73 DEN shows similar activity to Pd147 DEN and excellent substrate adaptability under mild reaction conditions. Moreover, the Cu component can play an important role in tuning the catalytic activity of PdxCu147-x DEN. Density functional theory (DFT) calculations illustrate that the similar activities of the Pd147 and Pd74Cu73 DENs originate from the comparable energy barriers of the rate-determining steps. The partial density of states (PDOS) and electron density differences demonstrate that Cu decreases the intensities of the valence orbitals of the top and edge Pd atoms and weakens orbital interactions between the intermediates and Pd74Cu73 DEN, leading to low desorption energies of the products. This work can provide a promising strategy to reduce the cost of Pd catalysts in Suzuki cross-coupling reactions.

A novel three-component cascade reaction was discovered and developed to synthesize pyridodiindoles with the assistance of microwave irradiation. A collection of pyridodiindoles was prepared by means of the mild reaction and simple operation procedure, which could be applicable to a broad scope of functional aldehydes. Screening demonstrated that compound 5g exhibited a good potency in HCT116 cell lines, and this work validated the feasibility of this novel reaction for generating promising bioactive compounds.

In this study, NH3 treatment of CeO2 was found to significantly enhance its NH3-SCR performance. The NH3-treated CeO2 was characterized by BET, XRD, TPR and XPS. The obtained results revealed the excellent SCR activity and stability of CeO2 catalyst treated by NH3 should be originated from the dropped crystallinity, better reducibility, along with the production of more Ce3+ and surface adsorbed oxygen. Furthermore, in situ DRIFT study has been carried out and the results indicated that the Langmuir-Hinshelwood (L-H) mechanism could be applied for explaining the SCR reaction route over CeO2-N.

Xueshuan Xinmaining Tablet (XXT) is a widely used traditional Chinese medicine for the treatment of stroke, chest pain, coronary heart disease, and angina pectoris caused by blood stasis. Having a multiple-component preparation, it is still far from meeting the requirements of modernization and standardization because its detailed chemical basis and action mechanism have not been clarified. In this work, the different batches of XXT samples were analyzed by HPLC and the typical sample was analyzed by UPLC-ESI-Q-TOF/MS to understand its chemical profiling. As a result, 77 chromatographic peaks were detected, among which 63 constituents were identified or tentatively characterized based on the comparison of retention time and UV spectra with authentic compounds as well as by summarized MS fragmentation rules and matching of empirical molecular formula with those of published components. This is the first systematic report on the chemical profiling of the commercial XXT products, which provides the sufficiently chemical evidence for the global quality evaluation of XXT products.

Herein, the radiative and non-radiative decay processes of six carborane-based Pt(II) complexes were explored with the help of the density functional theory and time-dependent density functional theory. In order to interpret the influence of non-metal heavy atoms on the phosphorescent quantum yields, the determined factors, i.e., the ZFS (zero-point filed splitting) parameters, radiative decay rate constants and photodeactivation mechanisms, were unveiled. The results indicate that the spin-orbital coupling effects can be slightly regulated via introducing the non-metal heavy atoms into the carborane. Also, the non-metal heavy atoms substituents could cause slightly decrease of the energy barriers between the 3ES and 3MC excited states, and thus, for Pt-6, a fast non-radiative decay process may occur. Moreover, compared with the Pt-1, the rotation of methyl in Pt-2 ∼ 5, can be effectively restricted with the aid of hydrogen bonding and halogen bonding, which is beneficial for obtaining small non-radiative decay rate constants. Accordingly, it provides a strategy for realizing the restriction of small group rotation to achieve the high-efficient phosphorescent emitters.

A small series of hydantoins was efficiently synthesized via a two-step Ugi/cyclization reaction sequence using alkyne group as a leaving group under basic conditions. This microwave-assisted one-pot cyclization strategy could be applicable to other multicomponent reactions (MCRs) for synthesizing bioactive and drug-like hydantoins.

Freestanding silicene has been predicted to possess graphene-like electronic structures with a Dirac cone; however, the gapless nature of silicene limits its applications in silicon-based electronics. On the other hand, it is also important to find a substrate that can support silicene, which keeps the required features thereof. Here, based on the first-principles calculations, we show that an α-phase bismuth-passivated Si surface, i.e., S i ( 111 ) 3 × 3 − B i , is semiconducting with a band-gap greater than 0.75 eV which could then be an appropriate surface to support silicene. For the adsorption of silicene on the passivated Si surface, s i l i c e n e / S i ( 111 ) 3 × 3 − B i , three adsorption sites of silicene, i.e., the hollow site (H-site) and the two top sites (TL-site and TH-site), are discussed. Silicene absorbed on the H-site can open a band gap (0.174 eV) for the silicene layer, and the Dirac cone of silicene disappeared. For the TL-site model, a semiconducting character of the system with a very small band gap (31 meV) is found. For the silicene on the TH-site, the interaction between the silicene layer and the passivated Si(111) surface is very weak, suggesting that such a Bi-passivated surface S i ( 111 ) 3 × 3 − B i can support silicene, meanwhile, keeping the main features of silicene thereof. The present study suggests that a Bi-passivated Si(111) surface could be used to support silicene and open a small band gap at the silicene layer.

Controlling the photostability of the organometallic complex is vital for obtaining the long-lasting phosphorescent organic light-emitting diode. In this article, the density functional theory was employed to investigate the photostabilities of a series of tridentate Pt(II) complexes in the triplet–triplet annihilation (TTA) processes. The calculated results indicate that the existence of the Pt–C*(NHC) bond can increase the Gibbs free main ligand dissociation energy to avoid the main ligand dissociation during the TTA process. According to the Wiberg bond order and electron localization function, the positive effect of the Pt–C*(NHC) bond originates from the strong d and p orbital interactions and more electron localization between C*(NHC) and Pt atoms. In addition, the study in this article also manifests that the auxiliary ligands with strong electron-withdrawing/-donating properties can facilitate the electron localization, leading to the increase of photostabilities for the tridentate Pt(II) complexe...

A post-Ugi diastereoselective one-pot cascade reaction requiring no metal catalyst was developed. The reaction scope was wide with mild conditions and good yields. A collection of spiroindolines was prepared by the protocol and screening tests in several difficult-to-inhibit cancer cell lines were conducted. The relationship of structure and anticancer activities was promising and in the Huh7 cell lines compound 16 j is more potent than Vinbalstine. The cyclization design strategy could be applicable to other multicomponent reactions (MCRs) for synthesizing bioactive and drug-like heterocycles.

Searching for new cathode materials is very important in the field of Na-ion batteries. Transition metal sodium orthosilicates have attracted much attention due to the significant progress made in its analog of lithium orthosilicates. In this work, density functional theory (DFT) calculations are performed to study the structural stabilities, electronic and electrochemical properties of Na2FeSiO4 polymorphs, and their corresponding desodiated products Na x FeSiO4. Our results show that formation energies of all the calculated structures differ substantially upon removal of Na, indicating that phase transformations should happen during the desodiation for different polymorphs. NaFeSiO4 is the only energetically stable intermediate phase among the cases, leading to two theoretically voltage plateaus, i.e., ~ 2.0 V (2 ≥ x ≥ 1) and ~ 4.5 V (1 ≥ x ≥ 0) in Na x FeSiO4, respectively. Moreover, the oxidation of Fe2+ to Fe3+ ions is observed during the removal of the first Na ion, while both the oxidation of O and Fe ions occur during the further desodiation.

Unveiling the acetylene adsorption is crucial for designing novel and highly active catalyst for the semihydrogenation of alkyne. In order to achieve this goal, we have studied C 2 H 2 adsorption on the various nanoporous gold models in detail, including the Au(100), Au(111) and Au(321) slab models. The calculated results indicate that the C atoms of C 2 H 2 experience rehybridization from sp toward sp 2 /sp 3 when the adsorption occurs on bridge and hollow sites, which can be illustrated via the projected density of state (PDOS) and crystal orbital Hamilton population (COHP). Meanwhile, the formation of σ(Au C) bond is beneficial for facilitating acetylene adsorption and the kink Au atom plays an important role for the C 2 H 2 adsorption. In addition, for C 2 H 2 adsorption on the Ag doped nanoporous gold, the configurations strongly depend on the position of superficial unsubstituted Au atoms. Further, the inversely relationship has been found between the adsorption energies and number of the Ag substituents, demonstrating that the superficial Ag substituents are harmful for C 2 H 2 adsorption and activation.

Solid crystalline materials have long range order in their atomic arrangement while liquids have short range order, and the transition between them is usually caused by heat and/or pressure. Herein, we report the finding that chemical processes may play a similar role as heat and initiate liquid-like behavior of crystalline nanomaterials at a temperature far below their melting points. When the straight Cu/CuAu crystalline nanocables are dispersed in organic amine at 80 °C under ambient conditions, the continuous oxidation of Cu atoms on the surface and diffusion of Cu atoms from the core to the surface would break up the long-range ordered arrangement of atoms and lead to the transformation of an anisotropic crystal into an isotropic liquid-like state, which resulted in the evolution of the straight morphology of the nanocables into periodic wavy structures following the Rayleigh instability. It was also demonstrated that periodic wavy Cu@CuAu nanocables exhibit much better catalytic activity than straight Cu@CuAu nanocables towards the reduction of p-nitrophenol into p-aminophenol by NaBH4. Our results not only provide new insights into the transition between a solid crystal and a liquid-like state at the nanoscale, but also facilitate the development of new strategies for the synthesis of functional nanomaterials.

Structural phase transitions of electrode materials are responsible for poor reversibility during charge/discharge cycling in Li-ion batteries. Using previously developed structural databases, we investigate a structural landscape for LixFeSiO4 systems at x = 1. Starting with low-energy Li2FeSiO4 crystal structures, we explore the crystal structures of the material in different states of charge. The as-prepared Li2FeSiO4 materials adopt low energy structures characterized by two-dimensional (2D) Fe-Si networks. After the removal of one Li per formula unit to form LiFeSiO4, the structures with three-dimensional (3D) diamond-like Fe-Si networks become more energetically favorable without a significant impact on the charge capacity, which agrees with previous experimental and theoretical work. However, we reveal that the structure with a 3D diamond-like Fe-Si network can further transform into a new structure at x = 1. And the Li atom is hard to reinsert into these new structures. Consequently the system is prevented from returning to the Li2FeSiO4 state. We believe that the formation of this new structure plays an important role in the loss of reversible capacity of Li2FeSiO4 electrode materials.

The main purpose of this study was to investigate the active components of the Chinese medicine formula Shenqi San (SS) by high performance liquid chromatography with diode array detector and electrospray ionization-hybrid quadrupole time-of-flight mass spectrum (HPLC-DADESI- QTOF-MS), and demonstrate the anticancer mechanism of SS on human lung adenocarcinoma A549 cells by evaluating the cell proliferation and apoptosis induction. The chloroform extraction of SS (CE-SS) was extracted from SS, while HPLC-DAD-ESI-QTOF-MS assay was performed to identify components of CE-SS. MTT assay was used to quantify the proliferation of A549 cells with the treatment of CE-SS. Apoptosis analysis was carried out by detecting phosphatidylserine (PS) externalization using the Annexin V-FITC Apoptosis Detection Kit and the stained cells were analyzed with a flow cytometer. DAPI staining assay was carried out to observe morphological characteristics of apoptotic cells. Western blotting was used to detect the expression of important signaling proteins including caspase-3, -8, -9, p53, Bax and Bcl-2. Eight compounds were identified through HPLC-DAD-ESI-QTOF-MS analysis and 3-pyridine carboxylic acid, barbatin C, scutebarbatine F and barbatine D might be the main compounds responsible for the antitumor effect of CE-SS. CE-SS suppressed the proliferation of lung cancer A549 cells in a time- and dose-dependent manner. By Annexin V-FITC/PI double staining, we found that treatment with CE-SS induced apoptosis in A549 cells. After 24-h exposure to CE-SS, the expression of cleaved-caspase-9, cleaved-caspase-8 and cleaved-caspase-3 protein was activated, the expression of p53 protein increased while the ratio of Bax/Bcl-2 also increased. This study identified the eight compounds of CE-SS, and demonstrated their anticancer effect on human lung adenocarcinoma A549 cells via induction of apoptosis.

In the present article, the mechanism of 1,6-enyne cycloisomerization catalyzed by the planar Au 8 cluster was investigated in details by means of density functional theory. The effects of the size and shape of the gold nanoclusters (Au 7-20 ) on their catalysis of 1,6-enyne cycloisomerization were also studied. The computational results indicate that the main reaction channels of the 1,6-enyne cycloisomerization on the Au 8 cluster are the 5–exo–anti–cycloisomerization, and the single cleavage pathway is slightly more feasible than the double cleavage pathway. The selectivity of 1,6-enyne cycloisomerization catalyzed by the gold clusters is controlled by the orbital interaction between the gold atoms and the carbene fragment in the migration of CH 2 group. In addition, the influence of coordinate environment of the gold atoms on adsorption energy, catalytic activity, and regio-selectivity were amply interpreted as well.

Ti 2 Nb 10 O 29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate capability. To tackle this issue, a Cr 3+ –Nb 5+ co-doping is employed, and a series of Cr x Ti 2–2 x Nb 10+ x O 29 compounds are prepared. The co-doping does not change the Wadsley–Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li + -ion diffusion coefficients. Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties. During the first cycle at 0.1 C, the optimized Cr 0.6 Ti 0.8 Nb 10.6 O 29 sample delivers a large reversible capacity of 322 mAh g −1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g −1 , while that of Ti 2 Nb 10 O 29 is only 80 mAh g −1 . Furthermore, Cr 0.6 Ti 0.8 Nb 10.6 O 29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.

Carbon nanotubes (CNTs) are of great interest for many potential applications because of their extraordinary electronic, mechanical and structural properties. However, issues of chaotic staking, high cost and high energy dissipation in the synthesis of CNTs remain to be resolved. Here we develop a facile, general and high-yield strategy for the oriented formation of CNTs from metal-organic frameworks (MOFs) through a low-temperature (as low as 430 °C) pyrolysis process. The selected MOF crystals act as a single precursor for both nanocatalysts and carbon sources. The key to the formation of CNTs is obtaining small nanocatalysts with high activity during the pyrolysis process. This method is successfully extended to obtain various oriented CNT-assembled architectures by modulating the corresponding MOFs, which further homogeneously incorporate heteroatoms into the CNTs. Specifically, nitrogen-doped CNT-assembled hollow structures exhibit excellent performances in both energy conversion and storage. On the basis of experimental analyses and density functional theory simulations, these superior performances are attributed to synergistic effects between ideal components and multilevel structures. Additionally, the appropriate graphitic N doping and the confined metal nanoparticles in CNTs both increase the densities of states near the Fermi level and reduce the work function, hence efficiently enhancing its oxygen reduction activity. The viable synthetic strategy and proposed mechanism will stimulate the rapid development of CNTs in frontier fields.

We present an improved genetic algorithm (GA) for crystal structural prediction based on empirical potentials with a higher convergence rate. Some of the existed methods for crystal structure prediction via GA are much likely to suffer from stagnation during evolution, with a consequent loss of productivity and search depth. Some approaches, which include penalizing similar or identical structures in each generation to keep a rich diversity of structure in the population, and adjusting structures according to the possible space groups to skip the noise on the energy surface, are introduced herein to improve the GAs performance. Furthermore, the application of coevolution strategy between atomic positions and unit cell sizes and shapes via the local minimizer greatly reduces the computational cost. This has displayed an improvement in the quality of results found for the theoretical prediction of simple model crystal structures. The performance of the method is illustrated by successful identifications of known carbon and silicon carbide systems, but also gives some new promising structures (e.g., 2D structures). The high success rate of prediction demonstrates the dependability of this methodology and indicates the great potential of our method as a useful technique on crystal structure prediction.

A series of compounds containing the benzoxazepine-isoquinoline scaffold was synthesized in a one-pot procedure via an Ugi reaction followed by tautomerization reaction between the keto and enol forms and intramolecular nucleophilic substitution. The microwave-assisted strategy allowed the facile synthesis of a library of target compounds and is applicable to the construction of diverse libraries of related compounds for high throughput screening in medicinal chemistry.

Silicon carbide materials, as leading wide band gap semiconductors, hold significant importance in semiconductor technologies. Herein, diamond-like 3D materials with low density, but high elasticity properties, have been designed from first-principles calculations. They are porous single-crystalline materials composed of sp3 -hybridized silicon (or germanium) and sp-type C≡C (or B≡N) linear moieties; their stabilities are comparable to those of recently prepared SiC4 materials. Moreover, such wide band gap semiconductors have strong absorption over a wide UV range and exhibit superlight, superflexible, and incompressible mechanical properties, and their optoelectronic and mechanical properties can be well tuned through structural modifications. Such features provide high potential for practicable application under extreme conditions, and suggest promising applications for the design of UV optoelectronic devices.

A series of quinolino[3,4-b]quinoxalin-6(5H)-ones have been synthesized using an Ugi/deprotection/cyclization (UDC) strategy, followed by a nucleophilic aromatic substitution reaction. This facile microwave-assisted method provided good yields and could potentially be used for the construction of a diverse library of quinolino[3,4-b]quinoxalin-6(5H)-ones for high-throughput screening in medicinal chemistry.

We considered the geometric and electronic properties of C 20 molecule adsorbed on various two-dimensional (2D) substrates surfaces, such as graphene, silicene, germanene, stanene, BN and MoS 2 by using first-principles calculations based on the density functional theory. For each case, we have considered three adsorption configurations of C 20 molecule, i.e. top-site (T), hallow-site (H) and bridge site (B), respectively. Our results show that C 20 's are strongly bound to silicene, germanene and stanene, however, the adsorbed C 20 molecules have only weak interactions with graphene, BN and MoS 2 substrates. Moreover, charge density plot implies substantial charge transfer taking place between the constituents of C 20 and the substrate of silicene, germanene and stanene. Results indicate that the buckling structure of the 2D material plays important role in determining the reactivity of a 2D substrate.

An Ugi, novel pseudo-Knoevenagel, ring expansion cascade reaction was discovered and utilized for the synthesis of aziridinyl succinimides in one-pot. Subsequently, densely functionalized aziridines and maleimides have been designed and synthesized through similar cascade reactions. The target compounds were prepared by means of a mild reaction and a simple operation procedure, which could be applicable to a broad scope of starting materials. This series of novel cascade reactions generates opportunities for the tailored synthesis of a wide range of biologically active scaffolds through tuneable Ugi inputs. Discovery of compound 8i with comparable potency to sorafenib in liver cancer cell lines could provide a new avenue for liver cancer drug discovery.

Few-layer selenium and tellurium films have been recently prepared, and they provide a new platform to explore novel properties of two-dimensional (2D) elemental materials. In this work, we have performed a systematic first-principles study on the electronic, linear, and nonlinear optical (NLO) properties of atomically thin selenium and tellurium films within the density-functional theory with the generalized gradient approximation plus scissors correction using the band gaps from the relativistic hybrid Heyd-Scuseria-Ernzerhof functional calculations. Interestingly, we find that few-layer Se and Te possess large second-harmonic generation (SHG), linear electro-optic effect, and bulk photovoltaic effect. In particular, trilayer (TL) Te possesses large SHG coefficient, being more than 65 times larger than that of GaN, a widely used NLO material. Bilayer (BL) Te has huge static SHG coefficient, being more than 100 times larger than that of GaN. Furthermore, monolayer (ML) Se possesses large SHG coefficient. Moreover, we predict that TL Te exhibits strong bulk photovoltaic effect (BPVE), being greater than that of GeS, a polar system with the largest BPVE found so far. Although the shift current conductivities of bulk and 2D Se are comparable, the shift current conductivities of TL Te are five times larger than those of bulk Te. Finally, an analysis of the calculated electronic band structures indicates that the strong NLO responses of 2D Se and Te materials are primarily derived from their low-dimensional structures with high anisotropy, directional covalent bonding, lone-pair electrons, and relatively small band gaps. These findings provide a practical strategy to search for excellent NLO and BPVE materials., Comment: 15pages 12figures