In Situ Modulation of Oxygen Vacancies on 2D Metal Hydroxide Organic Frameworks for High-Efficiency Oxygen Evolution Reaction.

The discovery of non-precious catalysts for replacing the precious metal of ruthenium in the oxygen evolution reaction (OER) represents a key step in reducing the cost of green hydrogen production. The 2D d-MHOFs, a new 2D materials with controllable oxygen vacancies formed by controlling the degree of coordination bridging between metal hydroxyl oxide and BDC ligands are synthesized at room temperature, exhibit excellent OER properties with low overpotentials of 207  mV at 10 mA cm-2 . High-resolution transmission electron microscopy images and density functional theory calculations demonstrate that the introduction of oxygen vacancy sites leads to a lattice distortion and charge redistribution in the catalysts, enhancing the OER activity of 2D d-MHOFs comprehensively. Synchrotron radiation and in situ Raman/Fourier transform infrared spectroscopy indicate that part of oxygen defect sites on the surface of 2D d-MHOFs are prone to transition to highly active metal hydroxyl oxides during the OER process. This work provides a mild strategy for scalable preparation of 2D d-MHOFs nanosheets with controllable oxygen defects, reveals the relationship between oxygen vacancies and OER performance, and offers a profound insight into the basic process of structural transformation in the OER process.

Spatiotemporal convolution sleep network based on graph attention mechanism with automatic feature extraction.

BACKGROUND AND OBJECTIVE: Graph neural networks (GNNs) are widely used for automatic sleep staging. However, the majority of GNNs are based on spectral approaches, as far as we know, which heavily depend on the Laplacian eigenbasis determined by the graph structure with a large computing cost. METHODS: We introduced a non-spectral approach named graph attention networks v2 (GATv2) as the core of our network to extract spatial information (S-GATv2 in our work), which is more flexible and intuitive than the routined spectral method. Meanwhile, to resolve the issue of weak generalization of using traditional feature extraction, the multi-convolutional layers are implemented to automatically extract features. In this work, the proposed spatiotemporal convolution sleep network (ST-GATv2) consists of multi-convolution layers and a GATv2 block. Of note, the graph attention technique to the time domain was applied to construct temporal GATv2 (T-GATv2), which intends to capture the connection between two channels in the adjacent sleep stages. Besides, the modified function is further proposed to capture the hidden changing trend information by the difference in the feature's value of the two adjacent stages. RESULTS: In our experiment, we used the SS3 datasets in the MASS as our test datasets to compare with other advanced models. Our result reveals our model achieves the highest accuracy at 89.0 %. Besides, the proposed T-GATv2 block and modified function bring an approximate 0.5 % improvement in Kappa and F1-score. CONCLUSIONS: Our results support the potential of graph attention mechanisms and creative blocks (T-GATv2 and modified function) in sleep classification. We suggest the proposed ST-GATv2 model as an effective tool in sleep staging in either healthy or diseased states.

Extremely negative emotion interferes with cognition: Evidence from ERPs and time-varying brain network.

In recent years, the relationship between emotion and cognition was a hot topic. However, it remains unclear which specific emotions can significantly interfere with cognition and how they do so. In this study, we designed a novel Affective Stroop experiment paradigm to investigate these issues. The extremely negative (EN), moderately negative (MN), moderately positive (MP), extremely positive (EP) and neutral pictures were displayed before Stroop tasks. The behavioral results revealed that EN emotion significantly interfered with cognitive performance compared to other types of emotions, with a significant increase in reaction time under the EN emotion condition (P < 0.05). Furthermore, the dynamic brain mechanisms were analyzed from both Event-Related Potential (ERP) and time-varying brain network perspectives. Results showed that EN emotion evoked larger N2, P3, and LPP amplitudes in the frontal, parietal, and occipital brain regions. In contrast, the Stroop task under EN condition led to smaller N2, P3, and LPP amplitudes compared to neutral condition. This indicates that EN emotion was prioritized and consumed more cognitive resources relative to neutral emotion. During the P3 and LPP stages, we observed enhanced bottom-up connections between the parietal and frontal regions while the processing of EN emotion. Additionally, there were stronger top-down cognitive control connections from the frontal to the occipital regions while processing the Stroop task under EN condition. These findings consistently suggest that EN emotion interferes with cognition by consuming more cognitive resources, and the brain needs to enhance cognitive control to support Stroop task execution.

Synthesis of a ZnO nanowire array within minutes.

A ZnO nanowire array was successfully synthesized within 10 minutes, for the first time, through electrodeposition of a Zn nanocrystal coating followed by a microwave hydrothermal treatment, representing the cheapest and fastest route from aqueous solutions so far. This simple, economical, efficient, flexible and scalable method shows attractive prospects for industrial application.

EEG Network Analysis of Depressive Emotion Interference Spatial Cognition Based on a Simulated Robotic Arm Docking Task.

Depressive emotion (DE) refers to clinically relevant depressive symptoms without meeting the diagnostic criteria for depression. Studies have demonstrated that DE can cause spatial cognition impairment. However, the brain network mechanisms underlying DE interference spatial cognition remain unclear. This study aimed to reveal the differences in brain network connections between DE and healthy control (HC) groups during resting state and a spatial cognition task. The longer operation time of the DE group during spatial cognition task indicated DE interference spatial cognition. In the resting state stage, the DE group had weaker network connections in theta and alpha bands than the HC group had. Specifically, the electrodes in parietal regions were hubs of the differential networks, which are related to spatial attention. Moreover, in docking task stages, the left frontoparietal network connections in delta, beta, and gamma bands were stronger in the DE group than those of the HC group. The enhanced left frontoparietal connections in the DE group may be related to brain resource reorganization to compensate for spatial cognition decline and ensure the completion of spatial cognition tasks. Thus, these findings might provide new insights into the neural mechanisms of depressive emotion interference spatial cognition.

Biocompatible Ruthenium Single-Atom Catalyst for Cascade Enzyme-Mimicking Therapy.

Rationally constructing single-atom enzymes (SAEs) with superior activity, robust stability, and good biocompatibility is crucial for tumor therapy but still remains a substantial challenge. In this work, we adopt biocompatible carbon dots as the carrier material to load Ru single atoms, achieving Ru SAEs with superior multiple enzyme-like activity and stability. Ru SAEs behave as oxidase, peroxidase, and glutathione oxidase mimics to synchronously catalyze the generation of reactive oxygen species (ROS) and the depletion of glutathione, thus amplifying the ROS damage and finally causing the death of cancer cells. Notably, Ru SAEs exhibit excellent peroxidase-like activity with a specific activity of 7.5 U/mg, which surpasses most of the reported SAEs and is 20 times higher than that of Ru/C. Theoretical results reveal that the electrons of the Ru 4d orbital in Ru SAEs are transferred to O atoms in H2O2 and then efficiently activate H2O2 to produce •OH. Our work may provide some inspiration for the design of SAEs for cancer therapy.

Sulfonation Mechanism of Polysulfone in Concentrated Sulfuric Acid for Proton Exchange Membrane Fuel cell Applications.

The sulfonated polysulfone is a competitive proton-conducting material for proton exchange membrane fuel cells because of its relatively low cost and adequate performance compared with the perfluorinated sulfonic acid ionomers. This material can be economically synthesized by postsulfonation of commercial polysulfone; however, the inadequate sulfonation degree and the chain-scission degradation during sulfonation prevent the further optimization of its overall performance. In this work, the sulfonation mechanism of polysulfone is studied in terms of the transition state and activation energy based on density functional theory calculations, and the optimization of sulfonation processing parameters are discussed.

Polyvinylpyrrolidone-Coordinated Single-Site Platinum Catalyst Exhibits High Activity for Hydrogen Evolution Reaction.

The essence of developing a Pt-based single-atom catalyst (SAC) for hydrogen evolution reaction (HER) is the preparation of well-defined and stable single Pt sites with desired electrocatalytic efficacy. Herein, we report a facile approach to generate uniformly dispersed Pt sites with outstanding HER performance via a photochemical reduction method using polyvinylpyrrolidone (PVP) molecules as the key additive to significantly simplify the synthesis and enhance the catalytic performance. The as-prepared catalyst displays remarkable kinetic activities (20 times higher current density than the commercially available Pt/C) with excellent stability (76.3 % of its initial activity after 5000 cycles) for HER. EXAFS measurements and DFT calculations demonstrate a synergetic effect, where the PVP ligands and the support together modulate the electronic structure of the Pt atoms, which optimize the hydrogen adsorption energy, resulting in a considerably improved HER activity.

Construction of highly accessible single Co site catalyst for glucose detection.

The development of high-performance glucose sensors is an urgent need, especially for diabetes mellitus diagnosis. However, the glucose monitoring is conventionally operated in an invasive finger-prick manner and their noninvasive alternatives largely suffered from the relatively poor sensitivity, selectivity, and stability, resulted from the lack of robust and efficient catalysts. In this paper, we design a concave shaped nitrogen-doped carbon framework embellished with single Co site catalyst (Co SSC) by selectively controlling the etching rate on different facet of carbon substrate, which is beneficial to the diffusion and contact of analyte. The Co SSC prompts a significant improvement in the sensitivity of the solution-gated graphene transistor (SGGT) devices, with three orders of magnitude better than those of SGGT devices without catalysts. Our findings expand the field of single site catalyst in the application of biosensors, diabetes diagnostics and personalized health-care monitoring.

Ambient Synthesis of Single-Atom Catalysts from Bulk Metal via Trapping of Atoms by Surface Dangling Bonds.

Single-atom catalysts (SACs) feature the maximum atom economy and superior performance for various catalysis fields, attracting tremendous attention in materials science. However, conventional synthesis of SACs involves high energy consumption at high temperature, complicated procedures, a massive waste of metal species, and poor yields, greatly impeding their development. Herein, a facile dangling bond trapping strategy to construct SACs under ambient conditions from easily accessible bulk metals (such as Fe, Co, Ni, and Cu) is presented. When mixing graphene oxide (GO) slurry with metal foam and drying in ambient conditions, the M0 would transfer electrons to the dangling oxygen groups on GO, obtaining Mδ+ (0 < δ < 3) species. Meanwhile, Mδ+ coordinates with the surface oxygen dangling bonds of GO to form MO bonds. Subsequently, the metal atoms are pulled out of the metal foam by the MO bonds under the assistance of sonication to give M SAs/GO materials. This synthesis at room temperature from bulk metals provides a versatile platform for facile and low-cost fabrication of SACs, crucial for their mass production and practical application in diverse industrial reactions.

Shockley Partial Dislocation-Induced Self-Rectified 1D Hydrogen Evolution Photocatalyst.

Photocatalytic stability and efficient charge separation are key factors to photocatalytic performance for visible-light-driven H2 evolution from water. Here, we report a whole novel self-rectified photocatalyst constructed from the Shockley partial dislocation-induced multiple faults, using a ternary chalcogenide, that is, Cd0.8Zn0.2S nanorod as a model material. The introduction of multiple faults, which are typical planar defects, constructs a nanorectifier that aligns along the axial direction and constitutes a relatively ordered superstructure. The band bending and Fermi-level flattening at the nanorectifier would cause the photogenerated charge carriers to be transferred reversely at the axial direction on account of the charge type and then realize the separation of the charge carriers.

Thermal Emitting Strategy to Synthesize Atomically Dispersed Pt Metal Sites from Bulk Pt Metal.

Developing a facile route to access active and well-defined single atom sites catalysts has been a major area of focus for single atoms catalysts (SACs). Herein, we demonstrate a simple approach to generate atomically dispersed platinum via a thermal emitting method using bulk Pt metal as a precursor, significantly simplifying synthesis routes and minimizing synthesis costs. The ammonia produced by pyrolysis of Dicyandiamide can coordinate with platinum atoms by strong coordination effect. Then, the volatile Pt(NH3) x can be anchored onto the surface of defective graphene. The as-prepared Pt SAs/DG exhibits high activity for the electrochemical hydrogen evolution reaction and selective oxidation of various organosilanes. This viable thermal emitting strategy can also be applied to other single metal atoms, for example, gold and palladium. Our findings provide an enabling and versatile platform for facile accessing SACs toward many industrial important reactions.

Biocoordination Polymer Cross-Linking Structure to a 3D Star Topology Inorganic Photocatalyst Nanocrystal with Improved Hydrogen Evolution Performance.

An inorganic photocatalyst with a novel 3D star topology (ST) framework was obtained via multiple cross-linking of biocoordination polymers in one-step solvothermal conditions. It possessesd a large surface area (149.36 m2·g-1), among the highest value of the current reports, and represented the quantum size effect because of its 3D ST structure. The amino acid l-cysteine was introduced into the synthesis system to lead generation of the biometic coordination polymer through the amino acid dehydrate condensation and multiple cross-linking.

Doping effect of non-metal group in porous ultrathin g-C3N4 nanosheets towards synergistically improved photocatalytic hydrogen evolution.

Searching for effective approaches of accelerating charge separation and broadening optical absorption is critical for designing a high-performance photocatalytic system. Herein, a photocatalyst based on the non-metal group doped porous ultrathin g-C3N4 nanosheets (CNB NS) was prepared through a combined methodology of precursor reforming and thermal condensation. The synergistic effect of non-metal group doping and porous ultrathin nanosheet-architecture not only endow the material with improved light harvesting and regulated band structure, but also facilitate the electron-hole pair separation, supplying numerous active reactive sites and electron diffusion channels. As a result, the CNB NS photocatalyst exhibits a highly efficient photocatalytic H2 performance (the apparent quantum efficiency is 7.45% at 420 nm) and stability in water under the visible light, which is approximately 13 times higher than that of pure g-C3N4. This study may open a new perspective for designing the non-metal group doped g-C3N4 photocatalyst and further fabricate other advanced photocatalytic materials.

Whole-Visible-Light Absorption of a Mixed-Valence Silver Vanadate Semiconductor Stemming from an Assistant Effect of d-d Transition.

Wide-light absorption is important to semiconductors exploited in many applications such as photocatalysts, photovoltaic devices, and light-emitting diodes, which can effectively improve solar energy utilization. Especially for photocatalysts, the development and design of new semiconductors that harvest the whole-visible-light region (λ = 400-800 nm) is rarely reported, which is still a tremendous challenge up to now. Here we realize whole-visible-light absorption up to 900 nm for a semiconductor by means of construction of a mixed-valence Ag0.68V2O5, which results from an assistant effect of d-d transition. Ag0.68V2O5 serving as a photocatalyst obviously exhibits photoelectrochemical and photocatalytic properties. Our results provide a brand-new feasible design strategy to broaden the light absorption of semiconductors and highlight a route to further make the best use of the full solar spectrum.

A Novel Mesoporous Single-Crystal-Like Bi2WO6 with Enhanced Photocatalytic Activity for Pollutants Degradation and Oxygen Production.

The porous single-crystal-like micro/nanomaterials exhibited splendid intrinsic performance in photocatalysts, dye-sensitized solar cells, gas sensors, lithium cells, and many other application fields. Here, a novel mesoporous single-crystal-like Bi2WO6 tetragonal architecture was first achieved in the mixed molten salt system. Its crystal construction mechanism originated from the oriented attachment of nanosheet units accompanied by Ostwald ripening process. Additionally, the synergistic effect of mixed alkali metal nitrates and electrostatic attraction caused by internal electric field in crystal played a pivotal role in oriented attachment process of nanosheet units. The obtained sample displayed superior photocatalytic activity of both organic dye degradation and O2 evolution from water under visible light. We gained an insight into this unique architecture's impact on the physical properties, light absorption, photoelectricity, and luminescent decay, etc., that significantly influenced photocatalytic activity.

Durability, inactivation and regeneration of silver tetratantalate in photocatalytic H2 evolution.

The prepared Ag2Ta4O11 photocatalyst exhibits durable activity for H2 production from water. We investigated the durability, inactivation and regeneration mechanism in depth. This work provides a new perspective and makes an important step for the research on Ag-based photocatalysts.

An advanced Ag-based photocatalyst Ag2Ta4O11 with outstanding activity, durability and universality for removing organic dyes.

Constructing Ag-based photocatalysts by the incorporation of Ag(+) ions into metal/nonmetal oxides for removing organic pollutants is a recently developed strategy, but overcoming their own photocorrosion is still a tremendous challenge. In this work, an advanced Ag-based photocatalyst Ag2Ta4O11 is obtained by this strategy, which exhibits improved photocatalytic activity compared with Ta2O5 and the universality for degrading several organic dyes. Importantly, the Ag2Ta4O11 photocatalyst has outstanding durability and reusability, which indicates that it has potential application prospects for organic wastewater treatment in the printing and dyeing industry.

Higher visible photocatalytic activities of nitrogen doped In2TiO5 sensitized by carbon nitride.

N-doped In(2)TiO(5) modified by carbon nitride (CN) composite (NICN) has been prepared by the pyrogenation of the mixture of urea and In(2)TiO(5) through a polymerizable complex (PC) method. The powder samples were characterized by XRD, FESEM, TEM, UV-vis, and XPS. It is shown by XRD that the precursor sintered at 1000°C is pure and nitrogen dopant does not change the crystal structure of In(2)TiO(5). FESEM and TEM reveal a hole-like morphology of the prepared NICN. With the increase of nitrogen content, the light absorption onset of In(2)TiO(5) shifts from 410 nm to 450 nm, revealing significant narrowing of the band gap. XPS results suggest that only 2.2% of the nitrogen atoms were doped into In(2)TiO(5) through the urea pyrogenation method. Furthermore, the decomposition of Rhodamine B (Rh-B) under visible light reveals that Rh-B can be degraded completely within 20 min and recycling experiments indicate NICN has stable structure and durable photocatalytic activity, suggesting a promising utilization of such photocatalyst under visible light. Finally, an innovative mechanism of N-doped In(2)TiO(5) sensitized by carbon nitride polymer is proposed.