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Background: Liver and tumor segmentation from CT images is a complex and crucial step in achieving full-course adaptive radiotherapy and also plays an essential role in computer-aided clinical diagnosis systems. Deep learning-based methods play an important role in achieving automatic segmentation. Objective: This research aims to improve liver tumor detection performance by proposing a dual path feature extracting strategy and employing Swin-Transformer. Methods: The hierarchical Swin-Transformer is embedded into the encoder and decoder and combined with CNN to form a dual coding path structure incorporating long-range dependencies and multi-scale contextual connections to capture coarse-tuned features at different semantic scales. The features of the two encoding paths and the upsampling path are fused, tested and validated with LITS and in-house datasets. Results: The proposed method has a DG of 97.95% and a DC of 96.2% for liver segmentation; a DG of 80.6% and a DC of 68.1% for tumor segmentation; and a classification study of the tumor dataset shows a DG of 91.1% and a DC of 87.2% for large and continuous tumors and a DG of 71.7% and a DC of 66.4% for small and scattered tumors. Conclusions: Swin-Transformer can be used as a robust encoder for medical image segmentation networks and, combined with CNN networks, can better recover local spatial information and enhance feature representation. Accurate localization before segmentation can achieve better results for small and scattered tumors.

Electrochemical CO2 conversion is a promising way for sustainable chemical fuel production, yet the conversion efficiency is strongly limited by the sluggish kinetics and complex reaction pathways. Here we report the ultrathin conjugated metalloporphyrin covalent organic framework epitaxially grown on graphene as a two-dimensional van der Waals heterostructure to catalyze CO2 reduction. Operando X-ray absorption and density functional theory calculations reveal the strong interlayer coupling leads to electron-deficient metal centers and speeds up electrocatalysis. The Co(III)-N4 centers exhibit a CO Faradaic efficiency of 97% at a partial current density of 8.2 mA cm-2 in an H-cell, along with a stable running over 30 h. The selectivity of CO approached 99% with a partial current density of 191 mA cm-2 in a liquid flow cell, and the turnover frequency achieved 50 400 h-1 at -1.15 V vs RHE, outperforming most reported organometallic frameworks. This work highlights the key role of strong electronic coupling between van der Waals layers for accelerating the dynamics of CO2 conversion. This work is funded by the Natural Science Foundation of China (Grants 21872039 and 22072030), Science and Technology Commission of Shanghai Municipality (Grants 18JC1411700, 19DZ2270100, and 22520711100), and the Fundamental Research Funds for the Central Universities (20720220008).

Aqueous aluminum metal batteries (AMBs) are regarded as one of the most sustainable energy storage systems among post-lithium-ion candidates, which is attributable to their highest theoretical volumetric capacity, inherent safe operation, and low cost. Yet, the development of aqueous AMBs is plagued by the incapable aluminum plating in an aqueous solution and severe parasitic reactions, which results in the limited discharge voltage, thus making the development of aqueous AMBs unsuccessful so far. Here, we demonstrate that amorphization is an effective strategy to tackle these critical issues of a metallic Al anode by shifting the reduction potential for Al deposition. The amorphous aluminum (a-Al) interfacial layer is triggered by an in situ lithium-ion alloying/dealloying process on a metallic Al substrate with low strength. Unveiled by experimental and theoretical investigations, the amorphous structure greatly lowers the Al nucleation energy barrier, which forces the Al deposition competitive to the electron-stealing hydrogen evolution reaction (HER). Simultaneously, the inhibited HER mitigates the passivation, promoting interfacial ion transfer kinetics and enabling steady aluminum plating/stripping for 800 h in the symmetric cell. The resultant multiple full cells using Al@a-Al anodes deliver approximately a 0.6 V increase in the discharge voltage plateau compared to that of bare Al-based cells, which far outperform all reported aqueous AMBs. In both symmetric cells and full cells, the excellent electrochemical performances are achieved in a noncorrosive, low-cost, and fluorine-free Al2(SO4)3 electrolyte, which is ecofriendly and can be easily adapted for sustainable large-scale applications. This work brings an intriguing picture of the design of metallic anodes for reversible and high-voltage AMBs. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) C.Y. acknowledges funding supported by the National Natural Science Foundation of China (grant no. 52101246) and the Fundamental Research Funds for the Central Universities (grant no. 5710010721). Q.Y. acknowledges funding support from the Singapore MOE AcRF Tier 1 grant no. 2020-T1-001- 031 and the Singapore A*STAR project A19D9a0096. G.Y. acknowledges funding support from the Camille Dreyfus Teacher-Scholar Award and the Welch Foundation Award F1861.

Synthesizing urea from nitrate and carbon dioxide through an electrocatalysis approach under ambient conditions is extraordinarily sustainable. However, this approach still lacks electrocatalysts developed with high catalytic efficiencies, which is a key challenge. Here, we report the high-efficiency electrocatalytic synthesis of urea using indium oxyhydroxide with oxygen vacancy defects, which enables selective C-N coupling toward standout electrocatalytic urea synthesis activity. Analysis by operando synchrotron radiation-Fourier transform infrared spectroscopy showcases that *CO2NH2 protonation is the potential-determining step for the overall urea formation process. As such, defect engineering is employed to lower the energy barrier for the protonation of the *CO2NH2 intermediate to accelerate urea synthesis. Consequently, the defect-engineered catalyst delivers a high Faradaic efficiency of 51.0%. In conjunction with an in-depth study on the catalytic mechanism, this design strategy may facilitate the exploration of advanced catalysts for electrochemical urea synthesis and other sustainable applications. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) C.Y. acknowledges funding supported by the National Natural Science Foundation of China (Grant 52101246) and the Fundamental Research Funds for the Central Universities (Grant 5710010721). Q.Y. acknowledges funding support from Singapore MOE AcRF Tier 1 Grant 2020-T1-001-031 and Singapore A*STAR project A19D9a0096. G.Y. acknowledges funding support from the Camille Dreyfus TeacherScholar Award and Welch Foundation Award F-1861. The authors acknowledge computing resources from the National Supercomputing Centre, Singapore. This work is also supported by the Users with Excellence program of Hefei Science Center of CAS (2020HSC-UE003) and the Fundamental Research Funds for the Central Universities (WK2310000099).

Chemical doping is verified to be a promising strategy to regulate local electron distribution and further promote the poor intrinsic catalytic activity of graphdiyne. However, the current doping approach still faces problems such as precise doping for creating active sites and the destruction of graphdiyne skeleton calling for high temperature. Here, we achieved charge redistribution on graphdiyne surface through molecule functionalization. A p-type molecule–F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) was introduced and the site-defined functionalization was accomplished. Theoretical calculations showed that the charge transfer ability is improved and graphdiyne becomes positively charged. The oxygen reduction electrocatalysis was conducted as a proof of principle, where the electronic states of sp hybridized C active site was tuned toward favorable reaction intermediates’ adsorption. Such work from both theoretical prediction and experimental validation, found that molecule functionalization is effective to promote the electrocatalytic oxygen reduction, which creates new possibilities for graphdiyne’s applications in different electrochemical reactions.

Our work indicates that the decoupling relationship and distinctive temperature dependence of thermoelectric parameters can be obtained by regulating molecular arrangements and electronic structures of charge-transfer salts.

The scarcity of two-dimensional (2D) magnetic nanostructures has hindered their applications in spintronics, which is attributed to that most magnetic materials exhibit non-van der Waals (nvdWs) structure and it is hard to reduce their thickness to 2D nanostructures. Thus it is eager to develop a promising strategy for free-standing 2D magnetic nvdWs nanostructures. We have achieved free-standing 2D nvdWs hexagonal FeSe with a thickness of 2.9 nm by the reaction between oleylamine-Se complex and Fe2+ with the assistance of Cl-, where the synergetic effects of Cl- and -NH2 lead to the anisotropic growth. Inspiringly, the 2D hexagonal FeSe exhibits intrinsic antiferromagnetic order rooted in Fe2+ and semiconductor nature. In addition, the temperature variation would result in the chemical environment changes of Fe2+, responsible for the temperature-dependent magnetic transitions. This work promotes the potential applications of 2D hexagonal FeSe and the preparation of other 2D nvdWs materials.

Interlayer interactions are proved to be essential in determining the accurate active site of metal–benzenehexathiol (M–BHT) for hydrogen evolution and Mo–BHT is predicted to be a new promising member of the family of highly active M–BHT catalysts.

A large database is desired for machine learning (ML) technology to make accurate predictions of materials physicochemical properties based on their molecular structure. When a large database is not available, the development of proper featurization method based on physicochemical nature of target proprieties can improve the predictive power of ML models with a smaller database. In this work, we show that two new featurization methods, volume occupation spatial matrix and heat contribution spatial matrix, can improve the accuracy in predicting energetic materials’ crystal density ( ρ c r y s t a l ) and solid phase enthalpy of formation ( H f , s o l i d ) using a database containing 451 energetic molecules. Their mean absolute errors are reduced from 0.048 g / c m 3 and 24.67 k c a l / m o l to 0.035 g / c m 3 and 9.66 k c a l / m o l , respectively. By leave-one-out-cross-validation, the newly developed ML models can be used to determine the performance of most kinds of energetic materials except cubanes. Our ML models are applied to predict ρ c r y s t a l and H f , s o l i d of CHON-based molecules of the 150 million sized PubChem database, and screened out 56 candidates with competitive detonation performance and reasonable chemical structures. With further improvement in future, spatial matrices have the potential of becoming multifunctional ML simulation tools that could provide even better predictions in wider fields of materials science.

With ever-increasing energy consumption and continuous rise in atmospheric CO2 concentration, electrochemical reduction of CO2 into chemicals/fuels is becoming a promising yet challenging solution. Sn-based materials are identified as attractive electrocatalysts for the CO2 reduction reaction (CO2 RR) to formate but suffer from insufficient selectivity and activity, especially at large cathodic current densities. Herein, we demonstrate that Cu-doped SnS2 nanoflowers can undergo in situ dynamic restructuring to generate catalytically active S-doped Cu/Sn alloy for highly selective electrochemical CO2 RR to formate over a wide potential window. Theoretical thermodynamic analysis of reaction energetics indicates that the optimal electronic structure of the Sn active site can be regulated by both S-doping and Cu-alloying to favor formate formation, while the CO and H2 pathways will be suppressed. Our findings provide a rational strategy for electronic modulation of metal active site(s) for the design of active and selective electrocatalysts towards CO2 RR. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) We acknowledge the funding support from Singapore Ministry of Education AcRF Tier 1: RG5/20 and RG4/20; Tier 2: MOET2EP10120-0002, and Agency for Science, Technology and Research (A*Star) AME IRG: A20E5c0080.Great thanks are given to the Facility for Analysis, Characterization, Testing and Simulation (FACTS) of Nanyang Technological University, Singapore. We also like to acknowledge 111 project (D18023 ) from Zhengzhou University for their support of this work.

Aromatic interactions are commonly involved in the assembly of naturally occurring building blocks, and these interactions can be replicated in an artificial setting to produce functional materials. Here we describe a colorimetric biosensor using co-assembly experiments with plasmonic gold and surfactant-like peptides (SLPs) spanning a wide range of aromatic residues, polar stretches, and interfacial affinities. The SLPs programmed in DDD−(ZZ)x−FFPC self-assemble into higher-order structures in response to a protease and subsequently modulate the colloidal dispersity of gold leading to a colorimetric readout. Resultsshow the strong aggregation propensity of the FFPC tail without polar DDD head. The SLPs were specific to the target protease, i.e., Mpro, a biomarker for SARS-CoV-2. This system is a simple and visual tool that senses Mproin phosphate buffer, exhaled breath condensate, and saliva with detection limits of 15.7, 20.8, and 26.1 nM, respectively. These results may have value in designing other protease testing methods. Submitted/Accepted version The authors thank internal funding from the UC Office of the President (R00RG2515) and the National Institutes of Health (R01 DE031114; R21 AG065776-S1; R21 AI157957) for financial support. This work was also supported by National Science Foundation (DMR-2011924) via equipment in the UC San Diego Materials Research Science and Engineering Center (UCSD MRSEC). M.N.C. was supported by NIT under T32 CA15391.M.R. acknowledges the Wallonie-Bruxelles International (WBI) of the Fédération Wallonie-Bruxelles for financial support. The electron microscopy work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) of University of California San Diego, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (Grant ECCS-1542148). The MANTA analysis work was supported by the National Institutes of Health (S10 OD023555).

Solid polymer electrolytes (SPEs), which are favorable to form intimate interfacial contacts with electrodes, are promising electrolyte of choice for long-cycling lithium metal batteries (LMBs). However, typical SPEs with easily oxidized oxygen-bearing polar groups exhibit narrow electrochemical stability window (ESW), making it impractical to increase specific capacity and energy density of SPE based LMBs with charging cut-off voltage of 4.5 V or higher. Here, a polyfluorinated crosslinker has been applied to enhance oxidation resistance of SPEs via inductive electron-withdrawing effect of polyfluorinated segments transmitted through crosslinked networks. As a result, polyfluorinated crosslinked SPE exhibits a wide ESW, and the Li|SPE|LiNi0.5Co0.2Mn0.3O2 cell with a cutoff voltage of 4.5 V delivers a high discharge specific capacity of ~ 164.19 mAh g− 1 at 0.5 C and capacity retention of ~ 90% after 200 cycles. This work opens a new direction in developing SPEs for long-cycling high-voltage LMBs by using polyfluorinated crosslinking strategy.

A universal atomic layer confined doping strategy is developed to prepare Bi

Electrochemical CO2 reduction (CO2R) is a sustainable way of producing carbon-neutral fuels, yet the efficiency is limited by its sluggish kinetics and complex reaction pathways. Developing active, selective, and stable CO2R electrocatalysts is challenging and entails intelligent material structure design and tailoring. Here we show a graphdiyne/graphene (GDY/G) heterostructure as a 2D conductive scaffold to anchor monodispersed cobalt phthalocyanine (CoPc) and reduce CO2 with an appreciable activity, selectivity, and durability. Advanced characterizations, e.g., synchrotron-based X-ray absorption spectroscopy (XAS), and density functional theory (DFT) calculation disclose that the strong electronic coupling between GDY and CoPc, together with the high surface area, abundant reactive centers, and electron conductivity provided by graphene, synergistically contribute to this distinguished electrocatalytic performance. Electrochemical measurements revealed a high FECO of 96% at a partial current density of 12 mA cm-2 in a H-cell and an FECO of 97% at 100 mA cm-2 in a liquid flow cell, along with a durability over 24 h. The per-site turnover frequency of CoPc reaches 37 s-1 at -1.0 V vs RHE, outperforming most of the reported phthalocyanine- and porphyrin-based electrocatalysts. The usage of the GDY/G heterostructure as a scaffold can be further extended to other organometallic complexes beyond CoPc. Our findings lend credence to the prospect of the GDY/G hybrid contributing to the design of single-molecule dispersed CO2R catalysts for sustainable energy conversion.

Understanding the interactions between metallic lithium (Li) and the anchoring sites/groups is essential for the design of stable host materials and artificial interphases in lithium metal batteries (LMBs). Here, we investigate the interactions of lithium with the polar organic functional groups in copper(II) hexadecafluorophthalocyanine (F16CuPc) and copper(II) phthalocyanine (CuPc) through the combination of in-situ X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrotron-based near-edge X-ray absorption fine structures (NEXAFS), and density functional theory (DFT) calculations. It is revealed that the highly polar C-F bonds can anchor the Li atom via ionic Li-F interaction around the outer aza bridge N atoms in F16CuPc, while Li tends to interact with the inner pyrrolic N atoms around the central Cu in CuPc. The central Cu(II) ions in both molecules are reduced to Cu(I) upon interaction with Li. Electrons are transferred from Li to the lowest unoccupied molecular orbitals (LUMO) of both F16CuPc and CuPc molecules, as revealed by the UPS and NEXAFS measurements. Our systematic study can shed light on the design of anode materials by adding polar functional groups for applications in lithium metal batteries (LMBs). Ministry of Education (MOE) The authors acknowledge the financial support from the Natural Science Foundation of China (U2032147), Singapore MOE Tier II grant R143-000-A29-112, and Academic Research Fund Tie I grant RG104/18.

Mitigating nitrogen oxide emissions is critical to tackling global warming and improving air quality. Electrochemically converting nitrogen oxide pollutants into value-added fuels such as ammonia (NH3) and hydroxylamine (NH2OH) is of great significance, yet the efficiency is hindered by complex reaction pathways and sluggish kinetics. Here, we demonstrated monodispersed transition-metal sites, e.g., iron (Fe) and nickel (Ni), with atomically precise coordination environments to electrocatalyze nitric oxide conversion with remarkable selectivity, activity, and durability. We observed that metal centers strongly regulate the nitrogen-product distribution. In particular, Ni preferred NH3 production with a high yield rate of 1.6 mmol mg−1 h−1, whereas Fe exhibited a superior selectivity toward NH2OH, approaching a record-high production rate of 3.1 mmol mg−1 h−1 with a selectivity of 83.5%. Operando Fourier transform infrared spectroscopy revealed different NO adsorption capabilities of single-atomic Ni and Fe, which can well explain the different reduction pathways according to the theoretical calculations. Submitted/Accepted version This work is funded by the National Natural Science Foundation of China (grants 21872039 22072030, and 22272029), the Science and Technology Commission of Shanghai Municipality (grants 21DZ2260400 and 22520711100), and the Fundamental Research Funds for the Central Universities (20720220008). We are thankful for financial support from the Academic Research Fund Tier 1 (no. RG10/21) and the computing resources from National Supercomputing Centre Singapore.

Summary Aqueous electrochemical CO2 reduction (CO2R) on Cu can generate a variety of valuable fuels, yet challenges remain in the improvement of electrosynthesis pathways for highly selective fuel production. Mechanistically, understanding CO2R on Cu, particularly identifying the product-specific active sites, is crucial. Herein, we rationally designed and fabricated nine large-area single-crystal Cu foils with various surface orientations as electrocatalysts and identified the voltage- and facet-dependent CO2R selectivities. Operando grazing incidence X-ray diffraction (GIXRD) and electron back-scattered diffraction (EBSD) were applied to track the top-surface reconstructions of Cu, and we correlate the structural evolution with the change of product selectivities. We extracted three distinct structural descriptors, including crystal facet, atomic coordination number, and step-terrace angle, to reveal the intrinsic structure-function relationships and uniquely identify the specific product-producing sites for CO2R. Our work guides the rational design of Cu-based CO2R electrocatalysts and, more importantly, establishes a paradigm to understand the structure-function correlation in catalysis.

Heterogeneous single-atom catalysis has attracted great research interest in recent years. The atomically dispersed metal atoms, which are generally active sites in single-atom catalysts, could result in unconventional reaction mechanisms due to the site confinement of reaction intermediates. Their coordination environments substantially affect their activities through tuning the adsorption of reaction intermediates. Two kinds of coordination effects were discussed here: intrinsic coordination and dynamic coordination. The intrinsic coordination is formed in the synthesis process of the catalyst, and the dynamic coordination refers to the in situ coordination of an atom or a group introduced during catalysis. The charge capacity of the active site and solvation effect also play an important role in the adsorption of reactants and intermediates on single-atom catalysts. Ministry of Education (MOE) Submitted/Accepted version We thank the financial support from the Academic Research Fund Tier 1 (RG8/20) and the computing resources from National Supercomputing Centre Singapore. This work is also funded by the Natural Science Foundation of China (Grant 21872039) and the Science and Technology Commission of Shanghai Municipality (Grant 18JC1411700).

Electrocatalytic dinitrogen reduction reaction (N2RR) is an emerging route for ammonia synthesis at ambient conditions. Albeit the “π back-donation” process enables N2RR activity on transition metals with empty d-orbitals, given its dilemma in overcoming hydrogen evolution reaction (HER) competition, exploring p-block-element-based catalysts with relatively inferior HER activity is achievable for high selectivity. The challenge lies in designing rational structure to improve N2RR activity. Here, we synergistically integrate oxygen vacancy (VO) with hydroxyl on Bi4O5I2 (VO-Bi4O5I2-OH), which render this p-block-element-based material active to mimic “π back-donation” behavior because of sufficient vacant orbitals. In neutral media, the electrocatalytic N2RR performance of VO-Bi4O5I2-OH in terms of splendid faradic efficiency (32.4%) is superior to most of the prior reports using p-block-element-based catalysts. Our findings show a new strategy toward standout N2RR activity, which holds great potential in exploiting other p-block-element-based electrocatalysts. Ministry of Education (MOE) Accepted version Q.Y. acknowledges the funding support from Singapore MOE AcRF Tier 1 Grant Nos. RG113/15 and 2016-T1-002-065, and Tier 2 under Grant Nos. 2017-T2-2-069 and 2018-T2-01-010. The authors greatly thank the Facility for Analysis, Characterization, Testing and Simulation (FACTS) of Nanyang Technological University, Singapore, for using their TEM, SEM, and XRD equipment.

In nanoparticle self-assembly, the current lack of strategy to modulate orientational order creates challenges in isolating large-area plastic crystals. Here, we achieve two orientationally distinct supercrystals using one nanoparticle shape, including plastic crystals and uniform metacrystals. Our approach integrates multi-faceted Archimedean polyhedra with molecular-level surface polymeric interactions to tune nanoparticle orientational order during self-assembly. Experiments and simulations show that coiled surface polymer chains limit interparticle interactions, creating various geometrical configurations among Archimedean polyhedra to form plastic crystals. In contrast, brush-like polymer chains enable molecular interdigitation between neighboring particles, favoring consistent particle configurations and result in uniform metacrystals. Our strategy enhances supercrystal diversity for polyhedra comprising multiple nondegenerate facets.

Organic anode materials have attracted considerable interest owing to their high tunability by adopting various active functional groups. However, the interaction mechanisms between the alkali metals and the active functional groups in host materials have been rarely studied systematically. Here, a widely used organic semiconductor of perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) was selected as a model system to investigate how alkali metals interact with imide functional groups and induce changes in chemical and electronic structures of PTCDI. The interaction at the alkali/PTCDI interface was probed by in-situ X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrotron-based near edge X-ray absorption fine structure (NEXAFS), and corroborated by density functional theory (DFT) calculations. Our results indicate that the alkali metal replaces the hydrogen atoms in the imide group and interact with the imide nitrogen of PTCDI. Electron transfer induced gap states and downward band-bending like effects are identified on the alkali-deposited PTCDI surface. It was found that Na shows a stronger electron transfer effect than Li. Such a model study of alkali insertion/intercalation in PTCDI gives insights for the exploration of the potential host materials for alkali storage applications.

The effect of surface tensile strain on the photocatalysis is an open question. In this work, strain engineering has been demonstrated to promote the performance of photocatalysis by curved 2D mate...

Ideal electromagnetic (EM) wave absorption materials should exhibit strong absorption peaks and broad effective absorption bandwidths, which are important for EM protection and the stealth technology. Despite considerable advancements in this field in recent years, EM absorption materials have not reached their full potential to meet all the above-mentioned requirements, especially the broad absorption bandwidth at low frequencies. Herein, we synthesized a Co-doped NiZn ferrite (CNZFO)/polyaniline (PANI) on Ti3C2TX MXene composite with a hierarchical structure via three facile steps: exfoliation, hydrothermal process, and modified interfacial polymerization. The CNZFO particles and PANI chains as well as the small number of TiO2 particles uniformly grafted between the Ti3C2TX layers formed a unique sandwich-like structure. The multiple-layer composite showed excellent EM wave absorption with a maximum reflection loss (RL) of −37.1 dB at only 2.2 mm. It showed an effective bandwidth (RL

Graphene oxide/silica (GO/SiO2) multilayers could be successfully deposited onto a carbon fiber (CF) surface via a convenient and efficient layer-by-layer (LbL) self-assembly approach. It is possib...

Highly functionalized materials at the nanoscale on optical fibers offer notable opportunities to construct "lab-on-fiber" functional devices with unusual properties. However, it is extremely difficult to fabricate nanostructures with special morphology on a thin cylindrical optical fiber surface using the commonly used physical lithography techniques. Meanwhile, it is vital to maintain the plasmonic properties of Ag-riched particles while improving their stability. Herein, we design a facile strategy for the fabrication of Au-Ag bimetallic nanorings (Au-Ag NRs) immobilized on optical fibers for enhanced plasmonic properties. Ag NPs are first grownin situon an optical fiber surface through chelation and redox of polydopamine (PDA) to metal ions, and then are quickly converted into Au-Ag NRs by a galvanic replacement reaction and metal deposition. This conversion only takes 3.5 min, while the formed Au-Ag NRs exhibit outstanding localized surface plasmon resonance (LSPR) sensitivity (2204 nm per RIU) and oxidation resistance, and Au and Ag atoms are distributed uniformly in the nanorings. Furthermore, a novel and interesting formation process of the nanorings including deformation, spallation, growth in the gaps, and ring formation is studied. These findings provide a way to grow bimetallic nanorings on optical fibers, which are promising candidates for photoelectric "lab-on-fiber" devices. This work was supported by the Hainan Provincial Natural Science Foundation of China (No. 519QN179) and the National Natural Science Foundation of China (No. 21621004 and 51473115).

The bulk photovoltaic (BPVE) effect in crystals lacking inversion symmetry offers great potential for optoelectronic applications due to its unique properties, such as above-band-gap photovoltage and switchable photocurrent. Because of their large spontaneous polarizations, ferroelectric materials are ideal platforms for studying the BPVE. However, identifying the origin of an experimentally observed photovoltaic response is often challenging due to the entanglement between bulk and interface effects, leading to much debate in the field. This issue is particularly pronounced in vertical heterostructures, where the two effects are comparable. Here, we report crossover between bulk- and interface-dominant responses in vertical BiFeO3 heterostructures when changing the photon energy. We show that well-above-band-gap excitation leads to a bulk photovoltaic response, but band-edge excitation requires interface band bending to separate the photocarriers. Our findings not only help to clarify contradicting reports in the literature, but also lay the foundation for a deeper understanding of the ferroelectric photovoltaic effect and its applications in various devices. Ministry of Education (MOE) Published version L.Y. acknowledges startup funds from Soochow University and support from Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions. L.Y. also acknowledges support from the National Natural Science Foundation of China (Grants No. 11774249 and 12074278), the Natural Science Foundation of Jiangsu Province (Grant No. BK20171209), and the Key University Science Research Project of Jiangsu Province (Grants No. 18KJA140004 and 20KJA140001). J.W. acknowledges support from the Ministry of Education, Singapore (Grant No. AcRF Tier 1 189/18); a startup grant from the Southern University of Science and Technology (SUSTech), China; and support from the National Natural Science Foundation of China (Grant No. 12074164).