查看更多>>摘要：Spiking neural networks(SNNs)have superior energy efficiency due to their spiking signal transmission,which mimics biological nervous systems,but they are difficult to train effectively.Although surrogate gradient-based methods offer a workable solution,trained SNNs frequently fall into local minima because they are still primarily based on gradient dynamics.Inspired by the chaotic dynamics in animal brain learning,we propose a chaotic spiking backpropagation(CSBP)method that introduces a loss function to generate brain-like chaotic dynamics and further takes advantage of the ergodic and pseudo-random nature to make SNN learning effective and robust.From a computational viewpoint,we found that CSBP significantly outperforms current state-of-the-art methods on both neuromorphic data sets(e.g.DVS-CIFAR10 and DVS-Gesture)and large-scale static data sets(e.g.CIFAR100 and ImageNet)in terms of accuracy and robustness.From a theoretical viewpoint,we show that the learning process of CSBP is initially chaotic,then subject to various bifurcations and eventually converges to gradient dynamics,consistently with the observation of animal brain activity.Our work provides a superior core tool for direct SNN training and offers new insights into understanding the learning process of a biological brain.
查看更多>>摘要：Non-centrosymmetric topological material has attracted intense attention due to its superior characteristics as compared with the centrosymmetric one,although probing the local quantum geometry in non-centrosymmetric topological material remains challenging.The non-linear Hall(NLH)effect provides an ideal tool to investigate the local quantum geometry.Here,we report a non-centrosymmetric topological phase in ZrTe5,probed by using the NLH effect.The angle-resolved and temperature-dependent NLH measurement reveals the inversion and ab-plane mirror symmetries breaking at＜30 K,consistently with our theoretical calculation.Our findings identify a new non-centrosymmetric phase of ZrTe5 and provide a platform to probe and control local quantum geometry via crystal symmetries.
查看更多>>摘要：Surface electrons in axion insulators are endowed with a topological layer degree of freedom followed by exotic transport phenomena,e.g.,the layer Hall effect.Here,we propose that such a layer degree of freedom can be manipulated in a dissipationless way based on the antiferromagnetic MnBi2Te4 with tailored domain structure.This makes MnBi2Te4 a versatile platform to exploit the'layertronics'to encode,process and store information.Importantly,the layer filter,layer valve and layer reverser devices can be achieved using the layer-locked chiral domain wall modes.The dissipationless nature of the domain wall modes makes the performance of the layertronic devices superior to those in spintronics and valleytronics.Specifically,the layer reverser,a layer version of the Datta-Das transistor,also fills up the blank in designing the valley reverser in valleytronics.Our work sheds light on constructing new generation electronic devices with high performance and low-energy consumption in the framework of layertronics.
查看更多>>摘要：Magnetic structure plays a pivotal role in the functionality of antiferromagnets(AFMs),which not only can be employed to encode digital data but also yields novel phenomena.Despite its growing significance,visualizing the antiferromagnetic domain structure remains a challenge,particularly for non-collinear AFMs.Currently,the observation of magnetic domains in non-collinear antiferromagnetic materials is feasible only in Mn3Sn,underscoring the limitations of existing techniques that necessitate distinct methods for in-plane and out-of-plane magnetic domain imaging.In this study,we present a versatile method for imaging the antiferromagnetic domain structure in a series of non-collinear antiferromagnetic materials by utilizing the anomalous Ettingshausen effect(AEE),which resolves both the magnetic octupole moments parallel and perpendicular to the sample surface.Temperature modulation due to AEE originating from different magnetic domains is measured by lock-in thermography,revealing distinct behaviors of octupole domains in different antiferromagnets.This work delivers an efficient technique for the visualization of magnetic domains in non-collinear AFMs,which enables comprehensive study of the magnetization process at the microscopic level and paves the way for potential advancements in applications.
查看更多>>摘要：Lithiated organic cathode materials show great promise for practical applications in lithium-ion batteries owing to their Li-reservoir characteristics.However,the reported lithiated organic cathode materials still suffer from strict synthesis conditions and low capacity.Here we report a thermal intermolecular rearrangement method without organic solvents to prepare dilithium hydroquinone(Li2Q),which delivers a high capacity of 323 mAh g-1 with an average discharge voltage of 2.8 V.The reversible conversion between orthorhombic Li2Qand monoclinic benzoquinone during charge/discharge processes is revealed by in situ X-ray diffraction.Theoretical calculations show that the unique Li-O channels in Li2Qare beneficial for Li+ion diffusion.In situ ultraviolet-visible spectra demonstrate that the dissolution issue of Li2Qelectrodes during charge/discharge processes can be handled by separator modification,resulting in enhanced cycling stability.This work sheds light on the synthesis and battery application of high-capacity lithiated organic cathode materials.
查看更多>>摘要：The development of strong sensitizing and Earth-abundant antenna molecules is highly desirable for CO2 reduction through artificial photosynthesis.Herein,a library of Zn-dipyrrin complexes(Z-1-Z-6)are rationally designed via precisely controlling their molecular configuration to optimize strong sensitizing Earth-abundant photosensitizers.Upon visible-light excitation,their special geometry enables intramolecular charge transfer to induce a charge-transfer state,which was first demonstrated to accept electrons from electron donors.The resulting long-lived reduced photosensitizer was confirmed to trigger consecutive intermolecular electron transfers for boosting CO2-to-CO conversion.Remarkably,the Earth-abundant catalytic system with Z-6 and Fe-catalyst exhibits outstanding performance with a turnover number of＞20 000 and 29.7％quantum yield,representing excellent catalytic performance among the molecular catalytic systems and highly superior to that of noble-metal photosensitizer Ir(ppy)2(bpy)+under similar conditions.Experimental and theoretical investigations comprehensively unveil the structure-activity relationship,opening up a new horizon for the development of Earth-abundant strong sensitizing chromophores for boosting artificial photosynthesis.
查看更多>>摘要：A small fraction of NOx(＜1％)always exists in CO2 feedstock(e.g.exhausted gas),which can significantly reduce the efficiency of CO2 electroreduction by～30％.Hence,electrochemical denitrification is the precondition of CO2 electroreduction.The pH effect is a key factor,and can be used to tune the selectivity between N2 and N2O production in electrochemical denitrification.However,there has been much controversy for many years about the origin of pH dependence in electrocatalysis.To this end,we present a new scheme to accurately model the pH dependence of the electrochemical mechanism.An extremely small pH variation from pH 12.7 to pH 14 can be accurately reproduced for N2O production.More importantly,the obviously different pH dependence of N2 production,compared to N2O,can be attributed to a cascade path.In other words,the N2 was produced from the secondary conversion of the as-produced N2O molecule(the major product),instead of the original reactant NO.This is further supported by more than 35 experiments over varying catalysts(Fe,Ni,Pd,Cu,Co,Pt and Ag),partial pressures(20％,50％and 100％)and potentials(from-0.2 to 0.2 V vs.reversible hydrogen electrode).All in all,the insights herein overturn long-lasting views in the field of NO electroreduction and suggest that rational design should steer away from catalyst engineering toward reactor optimization.
查看更多>>摘要：Vesicle,a microscopic unit that encloses a volume with an ultrathin wall,is ubiquitous in biomaterials.However,it remains a huge challenge to create its inorganic metal-based artificial counterparts.Here,inspired by the formation of biological vesicles,we proposed a novel biomimetic strategy of curling the ultrathin nanosheets into nanovesicles,which was driven by the interfacial strain.Trapped by the interfacial strain between the initially formed substrate Rh layer and subsequently formed RhRu overlayer,the nanosheet begins to deform in order to release a certain amount of strain.Density functional theory(DFT)calculations reveal that the Ru atoms make the curling of nanosheets more favorable in thermodynamics applications.Owing to the unique vesicular structure,the RhRu nanovesicles/C displays excellent hydrogen oxidation reaction(HOR)activity and stability,which has been proven by both experiments and DFT calculations.Specifically,the HOR mass activity of RhRu nanovesicles/C are 7.52 A mg(Rh+Ru)-1 at an overpotential of 50 mV at the rotating disk electrode(RDE)level;this is 24.19 times that of commercial Pt/C(0.31 mAmgpt-1).Moreover,the hydroxide exchange membrane fuel cell(HEMFC)with RhRu nanovesicles/C displays a peak power density of 1.62 W cm-2 in the H2-O2 condition,much better than that of commercial Pt/C(1.18 W cm-2).This work creates a new biomimetic strategy to synthesize inorganic nanomaterials,paving a pathway for designing catalytic reactors.
查看更多>>摘要：Multi-boron-embedded multiple resonance thermally activated delayed fluorescence(MR-TADF)emitters show promise for achieving both high color-purity emission and high exciton utilization efficiency.However,their development is often impeded by a limited synthetic scope and excessive molecular weights,which challenge material acquisition and organic light-emitting diode(OLED)fabrication by vacuum deposition.Herein,we put forward a B-N covalent bond-involved π-extension strategy via post-functionalization of MR frameworks,leading to the generation of high-order B/N-based motifs.The structurally and electronically extended π-system not only enhances molecular rigidity to narrow emission linewidth but also promotes reverse intersystem crossing to mitigate efficiency roll-off.As illustrated examples,ultra-narrowband sky-blue emitters(full-width at half-maximum as small as 8 nm in n-hexane)have been developed with multi-dimensional improvement in photophysical properties compared to their precursor emitters,which enables narrowband OLEDs with external quantum efficiencies(EQEmax)of up to 42.6％,in company with alleviated efficiency decline at high brightness,representing the best efficiency reported for single-host OLEDs.The success of these emitters highlights the effectiveness of our molecular design strategy for advanced MR-TADF emitters and confirms their extensive potential in high-performance optoelectronic devices.
查看更多>>摘要：Fiber electronics with flexible and weavable features can be easily integrated into textiles for wearable applications.However,due to small sizes and curved surfaces of fiber materials,it remains challenging to load robust active layers,thus hindering production of high-sensitivity fiber strain sensors.Herein,functional sensing materials are firmly anchored on the fiber surface in-situ through a hydrolytic condensation process.The anchoring sensing layer with robust interfacial adhesion is ultra-mechanically sensitive,which significantly improves the sensitivity of strain sensors due to the easy generation of microcracks during stretching.The resulting stretchable fiber sensors simultaneously possess an ultra-low strain detection limit of 0.05％,a high stretchability of 100％,and a high gauge factor of433.6,giving 254-folds enhancement in sensitivity.Additionally,these fiber sensors are soft and lightweight,enabling them to be attached onto skin or woven into clothes for recording physiological signals,e.g.pulse wave velocity has been effectively obtained by them.As a demonstration,a fiber sensor-based wearable smart healthcare system is designed to monitor and transmit health status for timely intervention.This work presents an effective strategy for developing high-performance fiber strain sensors as well as other stretchable electronic devices.
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