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• The problem of overdetermined system of time-varying linear equations is firstly solved with the sixth-order approximation. • Theoretical analysis and experiments are provided to validate the availability and superiority of the proposed algorithm. • Applications of mobile localization are provided to show the applicability and effectiveness of the proposed algorithm. • The proposed algorithm is indicated to be useful for mobile localization of high precision. The challenges of the inefficiency of the existing static least-squares method and the insufficient precision of the existing neural algorithms need to be overcome. With the aid of the ten-instant Zhang time discretization formula, a novel ten-instant discrete-time neural network algorithm is proposed and generalized to the problem-solving of overdetermined system of time-varying linear equations. Theoretical analyses illustrate that the maximal steady-state residual error of the proposed algorithm has an order-6 pattern. Comparative experiment results further substantiate the superiority of the proposed algorithm. Moreover, applications of mobile localization based on the angle of arrival technique and the time difference of arrival technique are provided to display the applicability of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Time-variant Yang-Baxter-like matrix equation (YBLME) with the disturbances of noises is the hotspot in various scientific disciplines. The existing research, either can not handle the noise, or rely on the build-in numerical algorithm provided by MATLAB. Therefore, it is necessary to further study the digital-computer discrete solution of this problem. In this paper, the authors propose a noise-handling ten-instant discrete solution for the time-variant YBLME. By defining the matrix-form error function, Zhang neural network (ZNN) is exploited to design the continuous-time noise-handling ZNN model. For potential digital hardware (i.e., digital computer) realization, a discrete-time ZNN-based noise-handling ten-instant (DTZNH10i) algorithm, which is capable of handling three types of noises, is proposed on the basis of a Zhang time discretization (ZTD) formula. The convergence and precision of the proposed DTZNH10i algorithm are investigated and discussed. Theoretical analyses show the correctness and effectiveness of the proposed algorithm. The paper offers three examples of time-variant YBLME with disturbances of constant, linear, and bounded random noises to illustrate the efficacy and convergence of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Image-text matching is a vital yet challenging task in the field of vision and language. Unlike previous methods that usually adopt a symmetrical network to independently embed images and sentences into a joint latent space, we propose a novel Global-guided Asymmetric Attention Network (GAAN) to represent the two modalities more comprehensively. Specifically, we first design a Global Information-guided Transformer Encoder (GITE) to effectively mitigate the drawback of the lack of contextual information of the region features. Taking full advantage of the image global information, GITE is able to model the regional relations and region-global relations simultaneously, so as to obtain a more accurate visual representation. Then, we adopt a Textual Self-Attention (TSA) module to explore the word-word relations and produce the context-aware word representations. Finally, we deploy an Image-guided Textual Attention (ITA) module to explore the fine-grained correspondence between image regions and sentence words. By using context-aware visual information to guide textual representation learning, we can build asymmetric connections between vision and language to better exploit textual information. Experimental results on two benchmark datasets including MSCOCO and Flickr30k show that GAAN significantly surpasses state-of-the-art methods. [ABSTRACT FROM AUTHOR]

In the phylogenetic tree of RRM-type Rbps (RNA-binding proteins) in cyanobacteria, Rbp1 of Synechocystis 6803, with a single RRM (RNA recognition motif) region and a C-terminal glycine-rich region, and Rbp2, without the C-terminal region, both belong to the cluster I, whereas Rbp3 with a different type of C-terminal region is in the cluster II. Rbp1 is required for the cold adaptability of the cyanobacterium, and Rbp3 is for salt tolerance. Here, we report that the C-terminal region of Rbp1 is not required for the cold adaptability function but the C-terminal region of Rbp3 can direct the RRM of Rbp1 to the salt tolerance function. Bioinformatic and experimental analyses indicate that Rbps in cyanobacteria should be classified as two types. It is the first report for the distinct roles of C-terminal regions of Rbps in stress tolerance of cyanobacteria. [ABSTRACT FROM AUTHOR]

The time-variant matrix inversion (TVMI) problem solving is the hotspot of current research because of its frequent appearance and application in scientific research and industrial production. The generalized inverse problem of singular square matrix and nonsquare matrix can be related to Penrose equations (PEs). The PEs implicitly define the generalized inverse of a known matrix, which is of fundamental theoretical significance. Therefore, the in-depth study of PEs might enlighten problem solving of TVMI in a foreseeable way. For the first time, we construct three different matrix error-monitoring functions based on PEs and propose the corresponding models for TVMI problem solving by using the substitution technique and ZNN design formula. In order to facilitate computer simulation, the obtained continuous-time models are discretized by using ZTD (Zhang time discretization) formulas. Furthermore, the feasibility and effectiveness of the novel Zhang neural network (ZNN) multiple-multiplication model for matrix inverse (ZMMMI) and the PEs-based Getz–Marsden dynamic system (PGMDS) model in solving the problem of TVMI are investigated and shown via theoretical derivation and computer simulation. Computer experiment results also illustrate that the direct derivative dynamics model for TVMI is less effective and feasible. [ABSTRACT FROM AUTHOR]

In recent years, we have seen more and more interest in the field of medical images and shape comparison motivated by the latest advances in microcomputed tomography (μCT) acquisition, modelling, and visualization technologies. Usually, biologists need to evaluate the effect of different root canal preparation systems. Current root canal preparation evaluation methods are based on the volume difference, area difference, and transportation of two root canals before and after treatment. The purpose of root canal preparation is to minimize the volume difference and ensure the complete removal of the smear layer. Previous methods can reflect some general geometric differences, but they are not enough to evaluate the quality of root canal shape. To solve this problem, we proposed a novel root canal evaluation method based on spectrum and eigenfunctions of Steklov operators, which can be served as a better alternative to current methods in root canal preparation evaluation. Firstly, the ideal root canal model was simulated according to the root canal model before and after preparation. Secondly, the Steklov spectrum of the two models was calculated. Thirdly, based on the spectrum and the histogram of the Gaussian curvature on the surface, the weight of each eigenvalue was computed. Therefore, the Steklov spectrum distance (SSD), which measures shape difference between the root canals, was defined. Finally, the calculation method that quantifies the root canal preparation effect of root canals was obtained. Through experiments, our method manifested high robustness and accuracy compared with existing state-of-the-art approaches. It also demonstrates the significance of our algorithm's advantages on a variety of challenging root canals through result comparison with counterpart methods. [ABSTRACT FROM AUTHOR]

Graphical abstract Obtained by a solution-based acid-pasting approach, the composite of perylene diimide and carbon black (PTCDI/CB) exhibits excellent electrochemical performances as the organic cathode material in both lithium and sodium ion batteries. Abstract An acid-pasting approach is developed in this work to fabricate the composite of perylenetetracarboxylic diimide (PTCDI) and carbon black in concentrated sulfuric acid. Different from traditional mechanical mixing, the solution-based fabrication strategy enables the sufficient blending of PTCDI as active component and carbon black as conductive agent in the PTCDI/CB composite. Serving as the cathode material, the PTCDI/CB composite shows excellent electrochemical performances in both lithium ion battery (137 mAh g−1 at 100 mA g−1 and 110 mAh g−1 at 2000 mA g−1) and sodium ion battery (134 mAh g−1 at 100 mA g−1 and 99 mAh g−1 at 1000 mA g−1), which are comparable to the state-of-art organic/inorganic cathode materials. Considering the simplicity of the processing procedures and the low cost of the starting materials, the acid-pasting approach is a highly attractive method for the solution-based manufacturing of organic secondary battery electrodes. [ABSTRACT FROM AUTHOR]

Azide compounds are widely used and especially, polymers bearing pendant azide groups are highly desired in numerous fields. However, harsh reaction conditions are always mandatory to achieve full azidation, causing severe side reactions and degradation of the polymers. Herein, we report the design and preparation of two azide ionic liquids (AILs) with azide anion and triethylene glycol (E3)‐containing cation, [P444E3][N3] and [MIME3][N3]. Compared with the traditional sodium azide (NaN3) approach, both AILs showed much higher reaction rates and functional‐group tolerance. More importantly, they could act as both reagents and solvents for the quantitative azidation of various polymeric precursors under mild conditions. Theoretical simulations suggested that the outstanding performance of AILs originated from the existence of ion pairs during the reaction, and the E3 moieties played a crucial role. Lastly, after the reaction, the AILs could be easily regenerated, presenting a safer, greener, and highly efficient synthesis route for azide polymers. [ABSTRACT FROM AUTHOR]

Azide compounds are widely used and especially, polymers bearing pendant azide groups are highly desired in numerous fields. However, harsh reaction conditions are always mandatory to achieve full azidation, causing severe side reactions and degradation of the polymers. Herein, we report the design and preparation of two azide ionic liquids (AILs) with azide anion and triethylene glycol (E3)‐containing cation, [P444E3][N3] and [MIME3][N3]. Compared with the traditional sodium azide (NaN3) approach, both AILs showed much higher reaction rates and functional‐group tolerance. More importantly, they could act as both reagents and solvents for the quantitative azidation of various polymeric precursors under mild conditions. Theoretical simulations suggested that the outstanding performance of AILs originated from the existence of ion pairs during the reaction, and the E3 moieties played a crucial role. Lastly, after the reaction, the AILs could be easily regenerated, presenting a safer, greener, and highly efficient synthesis route for azide polymers. [ABSTRACT FROM AUTHOR]

Since scene graph can be used as the basis of many high-level vision semantic tasks, scene graph generation has attracted more and more attention of researchers, but most works are limited by the long-tail distribution of dataset, tend to predict those frequent but uninformative predicates such as "on" and "of." From a novel perspective, we found that in the training process, the model would promote the categories included in the batch, while suppressing the categories not in the batch. The long-tailed distribution of the data leads to the continuous suppression of tail categories, thus results in the model bias. In order to solve the problem above, we propose a novel simple and effective method named Batch Equalization Loss, which can be applied to most of the existing models and can bring effective improvement with only a few changes. It is worth noting that our method can achieve a more significant improvement on small batches than on big batches. Extensive experiments on the VG150 dataset show that our work can bring significant improvement on the basis of existing works. Code will be available at GitHub in the near future. [ABSTRACT FROM AUTHOR]

We consider semilinear Neumann problems at resonance. We are concerned with two distinct cases. In the first one, the potential function is unbounded and indefinite. In the second case, the potential function is bounded and the reaction exhibits a concave parametric term near the origin. We prove two existence theorems producing sign-changing solutions. The first main result is a complement of the results obtained by Papageorgiou and Rădulescu (2015) [22] . The second theorem gives an answer to the open question raised by Candito et al. (2016) [4] . Our approach uses variational methods together with flow invariance arguments. [ABSTRACT FROM AUTHOR]

AlCrN coatings were deposited on 316L stainless steel by multi-arc ion plating. The phase structures were controlled and optimised by vacuum annealing at 700 °C, 800 °C, and 900 °C, each for 2 h. The microstructures and morphologies of these coatings were examined by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscope, in association with adhesion strength measurement, residual stress measurement and potentiodynamic polarisation with 3.5% NaCl and 10% H 2 SO 4 solutions. Results show that the solid solution hcp-(Cr, Al)N phase of as-deposited AlCrN coatings decomposes into hcp-AlN and CrN phases, then further decompose into N and Cr with increasing annealing temperature. Metal particles and droplets on the coating surface were gradually removed simultaneously when compared with as-deposited coatings. The highest adhesion strength was obtained after annealing at 700 °C. It decreased with increasing annealing temperature due to the σ-FeCr phase and Cr 2 N phases, and the residual stress decreasing. The potentiodynamic polarisation measurements showed that the corrosion resistance of such coatings was significantly improved after annealing: the coatings annealed at 800 °C showed the best protective efficiency because some corrosion resistance phases (h-AlN, Al 2 O 3 , CrN, and Cr 2 N) were generated. [ABSTRACT FROM AUTHOR]

A controllable self-assembly strategy of positively charged polycyclic aromatic hydrocarbons (PCPAH) towards the formation of rectangle sheets and ribbon-like nanostructures has been achieved by choosing divalent anions with different sizes. In contrast, only rod-like nanostructures are obtained from PCPAH with univalent anions. It is revealed that the divalent anions play a key role in guiding the packing of PCPAH, which provides an unprecedented route to fabricate two-dimensional nanostructures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Heteroatom doped mesoporous carbon/graphene (HMCG) were fabricated by nano-casting technology. [•] In HMCGs, graphene is sandwiched in two heteroatom-doped mesoporous carbon layers. [•] HMCGs exhibited excellent electrochemical performance for the oxygen reduction reaction. [Copyright &y& Elsevier]

Particles and sheets: Polyaniline is used as a linker to couple metal oxides and hydroxides to graphene sheets. Hydrothermal treatment converts these coupled hybrids into nitrogen‐doped 2D carbon nanosheets integrated with size‐controlled metal nanoparticles. This structure gives these 2D nanohybrids promising electrochemical behavior in supercapacitors and oxygen‐reduction reactions. [ABSTRACT FROM AUTHOR]

Partikel und Blätter: Polyanilin dient als Brücke zur Kupplung von Metalloxiden und ‐ hydroxiden mit Graphenschichten. Eine Hydrothermalbehandlung überführt die gekuppelten Hybride in N ‐ dotierte Kohlenstoffnanoblätter, in denen Metallpartikel kontrollierter Größe eingeschlossen sind. Ihre Struktur verleiht diesen 2D ‐ Nanohybriden vielversprechende elektrochemische Eigenschaften in Superkondensatoren und in der Sauerstoffreduktion. [ABSTRACT FROM AUTHOR]

Highlights: [•] Four complexes with multiple helical characters are obtained upon a bis(triazole) ligand and dicarboxylate ligands. [•] The complexes are structurally characterized through single crystal X-ray diffraction. [•] Dicarboxylate coligands play a crucial role in tuning and enriching helical characters of coordination polymers. [ABSTRACT FROM AUTHOR]

Abstract: A novel synthetic method toward nitrogen containing positively charged dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium (DBNT, 1) salts was developed. In this method, the undehydrogenated precursor of DBNT, 14-phenyl-14-dibenzo[a,j]acridinium salt (6), was produced directly from the reaction between 14-phenyl-14-dibenzo[a,j]xanthenylium (2) and amine/aniline in reasonable yield. Various DBNT salts with different alkyl and alkylphenyl chains were synthesized in this two-step method. The self-assembly behavior of two alkylated DBNT salts, 1c and 1f, was studied in this work. Due to the different substituents and counterions, compound 1c formed nanoscale wirelike fibers, and helical aggregates were obtained from 1f, in their methanolic solutions. [Copyright &y& Elsevier]

A novel soft–hard template approach for preparing photoluminescent carbon dots (CDs) with tunable sizes, compositions, crystalline degrees and photoluminescence properties has been developed using four different precursors as carbon sources. The results offer a new strategy for fabrication of monodispersed CDs with well-defined morphology. [ABSTRACT FROM AUTHOR]

Flexible organic electrochemical transistor (OECT) based dopamine (DA) sensors are obtained by using Nafion and reduced graphene oxide wrapped carbonized silk fabric (Nafion/rGO/CSF) as the gate electrode. The resulting OECT sensors manifest excellent detection capability for DA with high sensitivity, broad detection range and high selectivity, which can still be retained under bent states. • Nafion/rGO/CSF is fabricated as the precious metal-free gate electrode for OECT. • Nafion/rGO/CSF based OECT has excellent detection ability for dopamine. • Nafion/rGO/CSF based OECT reserves the sensing performance under bent states. In this work, Nafion and reduced graphene oxide-wrapped carbonized silk fabric (Nafion/rGO/CSF) were fabricated into a precious metal-free gate electrode for organic electrochemical transistor (OECT) sensors. The hierarchical structure of CSF can effectively increase the conductivity of the electrode and avoid the aggregation of rGO and Nafion, giving the Nafion/rGO/CSF-based OECT sensors excellent detection capability towards dopamine (DA) with an ultralow detection limit of 1 nM, a broad detection range from 1 nM – 30 μM and a high selectivity. Moreover, the outstanding electrochemical sensing behaviors of the Nafion/rGO/CSF-based OECT sensor are retainable under bent states and in artificial urine, which will greatly facilitate its application in flexible electronics. The abovemenitoned results indicate that OECT sensors with carbon-based gate electrodes can also obtain high sensitivity comparable to that of precious metal gate electrodes, which, therefore, provides an unprecedented strategy for manufacturing flexible OECT sensors with high performance and low cost. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) provide the opportunity to fabricate flexible biosensors with high sensitivity. However, there are currently very few methods to improve the selectivity of OECT sensors. In this work, nitrogen/oxygen‐codoped carbon cloths (NOCCs) are prepared by the carbonization of polyaniline‐wrapped carbon cloths at 750 °C under different atmospheres. The resulting NOCC electrodes exhibit different electrochemical sensing behaviors toward ascorbic acid (AA) and dopamine (DA), enabling the fabrication of OECT sensors with high sensitivity and selectivity that are comparable to the state‐of‐the‐art OECT sensors for AA and DA. The structural characterization and theoretical calculation reveal that the electrochemical sensing behaviors of the NOCC electrodes are closely related to their surface compositions, providing an unprecedented strategy for the design of flexible OECT sensors with high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of up to 41 Tb cm−2 (256 Tb/in2). The written information is stable during reading at room temperature, but it can also be erased at will, instantly, by proper choice of tunneling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between the tip and substrate. [ABSTRACT FROM AUTHOR]

Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of up to 41 Tb cm−2 (256 Tb/in2). The written information is stable during reading at room temperature, but it can also be erased at will, instantly, by proper choice of tunneling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between the tip and substrate. [ABSTRACT FROM AUTHOR]

Abstract We consider the Brézis–Nirenbergproblem: { − Δ u = | u | 2 ⋆ − 2 u + λ u in Ω , u = 0 on ∂ Ω , where Ω is a smooth bounded domain in R N , N ≥ 3 , 2 ⋆ = 2 N N − 2 is the critical Sobolev exponent and λ > 0. Our main result asserts that if N ≥ 4 then there exists a pair of sign-changing solutions of the problem for every λ ∈ (0 , λ 1 (Ω)) , λ 1 (Ω) being the first eigenvalue of − Δ in Ω with Dirichlet boundary conditions, while if N = 3 then a pair of sign-changing solutions exists for λ slightly smaller than λ 1 (Ω). Our approach uses variational methods together with flow invariance arguments. [ABSTRACT FROM AUTHOR]

A catalyst-free aza-Michael addition/C(sp3)-O bond formation tandem reaction of substituted amino ferrocenes with quinone esters was developed, which provided a green and efficient strategy for the construction of a C(sp3)-O bond from C(sp3)-H, and a series of N-ferrocene-substituted benzodihydrooxazoles were smoothly produced in moderate to excellent yields (up to >99% yield). The mechanism experiments showed that quinone esters performed as both substrate and oxidant. The salient features of this transformation include good functional group tolerance, broad substrate scope and mild conditions. [ABSTRACT FROM AUTHOR]

Review: 130 refs. [ABSTRACT FROM AUTHOR]

Review: 230 refs. [ABSTRACT FROM AUTHOR]

A facile and cost-efficient synthesis approach toward hierarchically porous cobalt aluminum layered double hydroxide with hydrangea flower-like morphology (PCALs) is developed in this work via the hydrothermal treatment of cobalt- and aluminum-containing precursors under basic conditions following etching with NaOH. The architectures and porosities of the obtained PCALs can be easily modified by the fabrication conditions such as the concentration of the starting materials and the time of etching, which can further influence their electrochemical behavior. As the electrode material in a three-electrode supercapacitor, the PCALs can deliver a high capacitance of 550 F g for 1000 cycles with a retention rate over 82% at 10 A g. In addition, the asymmetric capacitor using PCALs as cathode and active carbon as anode also exhibits an excellent capacitance of 103.5 F g at 0.5 A g, indicating their potentials in the applications of energy storages. [ABSTRACT FROM AUTHOR]

Knoevenagel condensation is a powerful tool for the construction of vinylene‐linked covalent organic frameworks. Herein, we established a concise approach to vinylene‐linked COFs by Knoevenagel condensation at the multi‐methyl groups of a pyridine ring through in situ formation of an N‐acyl pyridinium cation in the presence of various acylating reagents. Following this strategy, two vinylene‐linked COFs were constructed using 2,4,6‐trimethylpyridine and multi‐aldehyde‐substituted aromatic derivatives as monomers. The resultant COFs are highly crystalline and assembled into hexagonal lattices with specific surface areas as large as 1915 m2 g−1 (vs. 1972 m2 g−1 of the theoretical value). The stable and abundant pyridine‐decorated regular nanochannels within the COFs allow for catalyzing the esterification of several pharmaceutical intermediates with distinct spatially confined selectivity and recyclability, representing an environmentally friendly catalytic organic transformation. [ABSTRACT FROM AUTHOR]

Knoevenagel condensation is a powerful tool for the construction of vinylene‐linked covalent organic frameworks. Herein, we established a concise approach to vinylene‐linked COFs by Knoevenagel condensation at the multi‐methyl groups of a pyridine ring through in situ formation of an N‐acyl pyridinium cation in the presence of various acylating reagents. Following this strategy, two vinylene‐linked COFs were constructed using 2,4,6‐trimethylpyridine and multi‐aldehyde‐substituted aromatic derivatives as monomers. The resultant COFs are highly crystalline and assembled into hexagonal lattices with specific surface areas as large as 1915 m2 g−1 (vs. 1972 m2 g−1 of the theoretical value). The stable and abundant pyridine‐decorated regular nanochannels within the COFs allow for catalyzing the esterification of several pharmaceutical intermediates with distinct spatially confined selectivity and recyclability, representing an environmentally friendly catalytic organic transformation. [ABSTRACT FROM AUTHOR]

By directly bonding the monolayer organic based electrodes together to assemble the book-like multilayer electrode, increased areal capacity and high flexibility can be achieved. The electrodes represent 5.88 mA h cm−2 at 0.7C and 5.24 mA h cm−2 at 0.2C areal capacity in lithium-ion and sodium-ion batteries, respectively. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) in the electrolyte of aqueous zinc ion batteries (AZIBs) can cause irreversible side reactions in zinc metal anode. Therefore, the accurate detection of the DO concentration in the aqueous electrolyte is crucial for the performance promotion and mechanistic studies of AZIBs. Herein, organic electrochemical transistor (OECT) based DO sensors are developed by utilizing a carbon fiber (CF) derived CF/platinum/Nafion/polydimethylsiloxane composite as the gate electrode and amine-doped poly(3,4-ethylenedioxythiophene): polystyrene sulfonate as the channel semiconductor. Operating at a gate-source voltage of −0.1 V and a drain-source voltage of −0.025 V, the OECT-DO sensor demonstrates a high sensitivity (141 mV decade−1), a low detection limit (0.0011 mg L−1), a wide linear range (0.027–8.7 mg L−1), and good stability, which are attributed to the transconductance capability of OECT. The exceptional performance of the OECT-DO sensor enables the accurate monitoring of DO content in aqueous zinc sulfate electrolyte, which provides an opportunity to gain an insight of the impact of DO concentration on the zinc metal electrode. This study not only provides a cost-effective and efficient solution for detecting DO concentration in aqueous electrolytes, but also explores the potential applications of OECT sensors in the energy storage devices. • OECT sensor for detecting dissolved oxygen (DO) in aqueous electrolyte was fabricated for the first time. • The transconductance capability of OECT-DO effectively improved its DO sensing performances. • OECT-DO showed high sensitivity, low detection limit, wide linear range, and good stability. • The influence of DO in aqueous electrolyte on zinc-ion battery was studied with OECT-DO. [ABSTRACT FROM AUTHOR]

Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron-doped, carbon-coated SnO2/graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO2/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core-shell architecture and B-doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium-ion batteries with a highly stable capacity of 1165 mA h g−1 at 0.1 A g−1 after 360 cycles and an excellent rate capability of 600 mA h g−1 at 3.2 A g−1, and thus outperforms most of the previously reported SnO2-based anode materials. [ABSTRACT FROM AUTHOR]

Two‒dimensional polymeric carbon nitride (2DPCN) is a versatile support for constructing single atom catalysts (SACs). Herein, we demonstrated a facile strategy for constructing atomic Co sites on 2DPCN. Atomic dispersion of Co was confirmed by the aberration‒corrected high angle annular dark field scanning transmission electron microscopy, while the extended X‒ray absorption fine structure spectroscopy analysis precisely corroborated the existence of atomic Co1–N 4 non square planar sites on 2DPCN support. Remarkably, Co1/2DPCN catalyst yielded H 2 at a rate of 28.3mmol H2 h−1 g Co −1, which is approximately 4.2 times higher than that of CoNPs/2DPCN (6.8mmol H2 h−1g Co −1) counterpart. Notably, with 0.75 wt % Pt as a co‒catalyst, H 2 evolution activity for Co1/2DPCN and CoNPs/2DPCN reached as high as 138.6 mmol H2 h−1 g metal −1 and 22.4mmol H2 h−1 g metal −1, respectively, which could be attributed to the synergistic effect of atomic Co1–N 4 sites and Pt. Both DFT calculations and spectroscopic results revealed that as constructed atomic Co1–N 4 sites, reduced band gap energy, improved light harvesting ability and decreased energy barrier for H 2 evolution. [Display omitted] • Demonstrated facile synthesis of Co single atoms on 2D polymeric carbon nitride support (Co1/2DPCN). • XAS analysis revealed the presence of distinct non square planar Co–N 4 atomic sites. • Atomic Co–N 4 sites promoted light absorption and directional charge transfer. • The atomic Co1/2DPCN catalyst achieved 28.3mmol H2 h−1 g Co −1 activity without the assistant of noble metal co‒catalyst. • Proposed H 2 evolution mechanism on the basis of experimental results and DFT calculations. [ABSTRACT FROM AUTHOR]

Embedding heteroatoms into the main backbones of polymeric materials has become an efficient tool for tailoring their structures and improving their properties. However, owing to comparatively harsh heteroatom‐doping conditions, this has rarely been explored in covalent organic frameworks (COFs). Herein, upon aldol condensation of a trimethyl‐substituted pyrylium salt with a tritopic aromatic aldehyde, a two‐dimensional oxonium‐embedded COF with vinylene linkages was achieved, which was further converted to a neutral pyridine‐cored COF by in situ replacement of oxonium ions with nitrogen atoms under ammonia treatment. The two heteroatom‐embedded COFs are conceptually isoelectronic with each other, featuring similar geometric structures but different electronic structures, rendering them capable of catalyzing the visible‐light‐promoted multi‐component synthesis of tri‐substituted pyridine derivatives with good recyclability. [ABSTRACT FROM AUTHOR]

Embedding heteroatoms into the main backbones of polymeric materials has become an efficient tool for tailoring their structures and improving their properties. However, owing to comparatively harsh heteroatom‐doping conditions, this has rarely been explored in covalent organic frameworks (COFs). Herein, upon aldol condensation of a trimethyl‐substituted pyrylium salt with a tritopic aromatic aldehyde, a two‐dimensional oxonium‐embedded COF with vinylene linkages was achieved, which was further converted to a neutral pyridine‐cored COF by in situ replacement of oxonium ions with nitrogen atoms under ammonia treatment. The two heteroatom‐embedded COFs are conceptually isoelectronic with each other, featuring similar geometric structures but different electronic structures, rendering them capable of catalyzing the visible‐light‐promoted multi‐component synthesis of tri‐substituted pyridine derivatives with good recyclability. [ABSTRACT FROM AUTHOR]

The article discusses the novel graphene-inspired synthesis of two-dimensional (2D) sandwichlike, graphene-based conjugated microporous polymers (GMPs). It says that nuclear magnetic resonance (NMR) spectroscopy was conducted to study the molecular structure of GMP-S. It states that the exciton dynamic of MP-S and GMP-S was examined by time-resolved photoluminescence spectroscopy. It mentions that the 2D porous polymers were used in preparing heteroatom-doped 2D porous carbons.

The article discusses a study which proposes a synthetic approach in the production of two-dimensional (2D) conjugated microporous polymers based on graphene. It mentions the methods used for the synthesis of the conjugate that involved the reduction of a graphene oxide sheet (GO) with hydrazine hydrate (RGO), dispersion of bromo-functionalized RGO, and scanning electron microscopy (SEM). It adds that the synthesis method is expected to provide the opportunity to create 2D porous polymers.

A long N-heterocyclic ligand, 2,6-bis(3-(pyrid-3-yl)-1,2,4-triazolyl)pyridine (H2bptp), and Zn(II)/Pb(II) yield {[Zn(bptp)(H2O)] · 2H2O·CH3CN} n (1) and {[Pb(bptp)] · H2O} n (2). Single-crystal X-ray diffraction analysis reveals that 1 and 2 possess 2-D networks containing alternating left- and right-handed helical motifs. Topologically, 1 features a (4,4) topology, while 2 exhibits a (6,3) topology. The bptp2− in 1 and 2 adopts syn-anti and syn-syn conformations, respectively. The results indicate that the long rigid N-heterocyclic ligand can adopt different conformations to coordinate with metals, beneficial to construction of helical structures with diverse topologies. The difference between the photoluminescence properties of the two complexes reveals that metal ions and coordination environment have significant influences on photoluminescence behavior. [ABSTRACT FROM PUBLISHER]

Gas-phase H2 activation by PtO+ and ${\rm PtO}_{2}^{+}$ were studied at the density functional level of theory (DFT) using the relativistic effective core potential (RECP) of Stuttgart basis sets on platinum atom and UB3LYP/6-311+G(2d,2p) level on hydrogen and oxygen atoms. Two reaction profiles corresponding to the doublet and quartet multiplicities were investigated in order to ascertain the presence of some spin inversion during the H2 reduction. The electron-transfer reactivity of the reactions were analyzed using the two-state model, and the strongly crossing behavior on the transition state (TS) area were shown. Finally, the actions of frontier molecular orbitals in minimum-energy crossing point (MECP) have been illuminated briefly. These theoretical results can act as a guide to further theoretical and experimental research. H2 activation mediated by metal oxide cations were found to be an exothermic spin-forbidden process resulting from a crossing between quartet and doublet profiles. To evaluate the spin-forbidden process in the reaction pathway, the spin-obit coupling (SOC) matrix elements are calculated at the MECP with the different potential energy surfaces (PESs) and the probability of crossing between the adiabatic potential-energy surfaces during a single pass through the avoided crossing region was described. Therefore, the intersystem crossing (ISC) at crossing points (CP) occur efficiently because of the large SOC (ca. 85.58 cm-1) involved. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with the stability and periodicity for a class of impulsive neural networks with delays. By means of the Fixed point theory, Lyapunov functional and analysis technique, some sufficient conditions of exponential stability and periodicity are obtained. We can see that impulses do contribution to the stability and periodicity. An example is given to demonstrate the effectiveness of the obtained results. [Copyright &y& Elsevier]

Abstract: This paper is concerned with a class of the impulsive bidirectional associative memories neural networks that possesses a Cohen–Grossberg dynamics incorporates time delays and variable coefficients. The existence of equilibrium point, globally exponential stability and globally exponentially robust stability are investigated by Lyapunov function and Halanay inequality. We can see that impulses do contribution to the exponential stability and robust stability. An illustrative example is given to demonstrate the effectiveness of the obtained results. [Copyright &y& Elsevier]

Some new azo-metal chelates were synthesized using different diazo components, coupling components and metal ions. Their structures were confirmed by IR spectra, MS spectra and UV–Vis spectra. Their solubility in 4-hydroxy-4-methyl-2-pentanone and absorption properties of film were measured. The influence on the difference of absorption maximum from azo-metal chelates to their ligands by diazo components, coupling components and metal ions was studied. [Copyright &y& Elsevier]

Prepared via a solution-based fabrication strategy, the PDI-EDA/CB composites rendered the zinc ion batteries with them as the cathodes obvious performance improvement in rate capability and cycling stability. [Display omitted] Organic electroactive compounds can be applied as alternative cathodes in rechargeable zinc ion batteries (ZIBs) instead of using inorganic cathode materials with low stability or high toxicity. However, many reported organic ZIB cathodes have some limitations, which are their tedious synthesis processes and low yields. In this work, perylene diimide-ethylenediamine/carbon black (PDI-EDA/CB) composites are prepared with a high yield of over 88% under mild conditions via a solution-based processing method. As the organic cathodes in aqueous ZIBs, the PDI-EDA/CB composites have a high specific capacity of 118.0 mA h g−1 at 0.05 A g−1; this capacity can be maintained as 95.0 mA h g−1 even at a high current density of 5.00 A g−1. Also, PDI-EDA/CB has good cycling stability by reserving 70.5% of its initial capacity after 1500 charge-discharge cycles at 1.00 A g−1, outperforming many recently reported ZIB cathodes. As disclosed by the structural and electrochemical characterization of PDI-EDA/CB, its excellent electrochemical performance is due to the zinc ion storage mechanism of PDI-EDA and the solution-based fabrication method. [ABSTRACT FROM AUTHOR]

We developed a simple approach to synthesizing ionic vinylene‐linked two‐dimensional covalent organic frameworks (COFs) through a quaternization‐promoted Knoevenagel condensation at three aromatic methyl carbon atoms of N‐ethyl‐2,4,6‐trimethylpyridinium halide with multitopic aromatic aldehyde derivatives. The resultant COFs exhibited a honeycomb‐like structure with high crystallinity and surface areas as large as 1343 m2 g−1. The regular shape‐persistent nanochannels and the positively charged polymeric frameworks allowed the COFs to be uniformly composited with linear polyethylene oxide and lithium salt, displaying ionic conductivity as high as 2.72×10−3 S cm−1. [ABSTRACT FROM AUTHOR]

We developed a simple approach to synthesizing ionic vinylene‐linked two‐dimensional covalent organic frameworks (COFs) through a quaternization‐promoted Knoevenagel condensation at three aromatic methyl carbon atoms of N‐ethyl‐2,4,6‐trimethylpyridinium halide with multitopic aromatic aldehyde derivatives. The resultant COFs exhibited a honeycomb‐like structure with high crystallinity and surface areas as large as 1343 m2 g−1. The regular shape‐persistent nanochannels and the positively charged polymeric frameworks allowed the COFs to be uniformly composited with linear polyethylene oxide and lithium salt, displaying ionic conductivity as high as 2.72×10−3 S cm−1. [ABSTRACT FROM AUTHOR]

• Two ionic cuprous complexes with thermally activated delayed fluorescence were synthesized. • Both complexes exhibit high contributions of TADF (83 and 80%, respectively) and PLQYs (47.5 and 60.5%, respectively) in the solid state at ambient temperature. • The small exchange energy caused by the pronounced spatial separation between HOMOs and LUMOs leads to a small Δ E ST and TADF at ambient temperature. • The OLEDs based on both complexes exhibit good performance and very mild efficiency roll-off. Herein two novel ionic cuprous complexes [Cu(POP)(Pytzb)]BF 4 (Cu1 , POP = bis(2-diphenylphosphinophenyl)ether, Pytzb = 2-(1-(benzyl)-1H-1,2,3-triazol-4-yl)pyridine) and [Cu(Xantphos)(Pytzb)]BF 4 (Cu2 , Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) have been synthesized in reasonable yields, and their crystal structure, UV absorption and photoluminescent properties, as well as electrochemical behaviors were investigated. At 300 K, both Cu1 and Cu2 in solid state exhibit outstanding green luminescence peaked at 533 and 526 nm, respectively, with significantly high photoluminescent quantum yields (PLQYs, 47.5 and 60.5%, respectively). Detailed exploration of emission decay times for Cu1 and Cu2 in dependence of temperature demonstrates that the two complexes are typical thermally activated delayed fluorescence (TADF) materials at ambient temperature with TADF proportions of 83 and 80%, respectively. The two complexes were employed as dopants in solution-processed electroluminescent devices. Thermally activated delayed fluorescence (TADF) of two new ionic cuprous complexes bearing 1,2,3-triazole ligand has been realized. Especially, both complexes exhibit high contributions of TADF (83 and 80%, respectively) and PLQYs (47.5 and 60.5%, respectively) in the solid state at ambient temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

The polarity of a semiconducting molecule affects its intrinsic photophysical properties, which can be tuned by varying the molecular geometry. Herein, we developed a D3h‐symmetric tricyanomesitylene as a new monomer which could be reticulated into a vinylene‐linked covalent organic framework (g‐C54N6‐COF) via Knoevenagel condensation with another D3h‐symmetric monomer 2,4,6‐tris(4′‐formyl‐biphenyl‐4‐yl)‐1,3,5‐triazine. Replacing tricyanomesitylene with a C2v‐symmetric 3,5‐dicyano‐2,4,6‐trimethylpyridine gave a less‐symmetric vinylene‐linked COF (g‐C52N6‐COF). The octupolar conjugated characters of g‐C54N6‐COF were reflected in its scarce solvatochromic effects either in ground or excited states, and endowed it with more promising semiconducting behavior as compared with g‐C52N6‐COF, such as enhanced light‐harvesting and excellent photo‐induced charge generation and separation. Along with the matched energy level, g‐C54N6‐COF enabled the two‐half reactions of photocatalytic water splitting with an average O2 evolution rate of 51.0 μmol h−1 g−1 and H2 evolution rate of 2518.9 μmol h−1 g−1. Such values are among the highest of state‐of‐the‐art COF photocatalysts. [ABSTRACT FROM AUTHOR]

The polarity of a semiconducting molecule affects its intrinsic photophysical properties, which can be tuned by varying the molecular geometry. Herein, we developed a D3h‐symmetric tricyanomesitylene as a new monomer which could be reticulated into a vinylene‐linked covalent organic framework (g‐C54N6‐COF) via Knoevenagel condensation with another D3h‐symmetric monomer 2,4,6‐tris(4′‐formyl‐biphenyl‐4‐yl)‐1,3,5‐triazine. Replacing tricyanomesitylene with a C2v‐symmetric 3,5‐dicyano‐2,4,6‐trimethylpyridine gave a less‐symmetric vinylene‐linked COF (g‐C52N6‐COF). The octupolar conjugated characters of g‐C54N6‐COF were reflected in its scarce solvatochromic effects either in ground or excited states, and endowed it with more promising semiconducting behavior as compared with g‐C52N6‐COF, such as enhanced light‐harvesting and excellent photo‐induced charge generation and separation. Along with the matched energy level, g‐C54N6‐COF enabled the two‐half reactions of photocatalytic water splitting with an average O2 evolution rate of 51.0 μmol h−1 g−1 and H2 evolution rate of 2518.9 μmol h−1 g−1. Such values are among the highest of state‐of‐the‐art COF photocatalysts. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) olefin-linked covalent organic frameworks (COFs) with excellent π-electron communication and high stability are emerging as promising crystalline polymeric materials. However, because of the limited species of COFs, their characteristics, processability and potential applications have not been completely understood and explored. In this work, we prepared two novel olefin-linked 2D COFs through Knoevenagel condensation of 2,4,6-trimethyl-1,3,5-triazine with tritopic triazine-cored aldehydes. The resulting COFs exhibit highly crystalline honeycomb-like structures stacked from hexagonal-latticed polymeric layers and display well-defined nanofibrillar morphologies with the uniform diameters of ca. 80 nm and ultra-lengths up to several micrometers. Such COF nanofibers can be readily composited with carbon nanotubes into high-quality continuous thin films, which are further compacted by a typical hot-pressing process to enhance their densities and mechanical strength without changing their fibrous microstructures. Such film-fabricated interdigital microelectrodes and the ionogel electrolyte are assembled into planar micro-supercapacitors (MSCs), which exhibit an outstanding areal capacitance of 44.3 mF cm−2, large operating voltage window of 2.5 V, high volumetric energy density of 38.5 mWh cm−3 as well as excellent cycling stability. [ABSTRACT FROM AUTHOR]