Unveiling Phenoxazine's Unique Reversible Two-Electron Transfer Process and Stable Redox Intermediates for High-Performance Aqueous Zinc-ion Batteries.

The low specific capacity determined by the limited electron transfer of p-type cathode materials is the main obstruction to their application towards high-performance aqueous zinc-ion batteries (ZIBs). To overcome this challenge, boosting multi-electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p-type material, we unveil the unique reversible two-electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non-aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed-shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non-equivalent hybridized sp2-N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g-1 compared to other p-type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi-electron transfer phenoxazine moieties for high-performance aqueous ZIBs.

Lithium-Induced Oxygen Vacancies in MnO2@MXene for High-Performance Zinc-Air Batteries.

The traditional methods for creating oxygen vacancies in materials present several challenges and limitations, such as high preparation temperatures, limited oxygen vacancy generation, and morphological destruction, which hinder the application of transition metal oxides in the field of zinc-air batteries (ZABs). In order to address these limitations, we have introduced a pioneering lithium reduction strategy for generating oxygen vacancies in δ-MnO2@MXene composite materials. This strategy stands out for its simplicity of implementation, applicability at room temperature, and preservation of the material's structural integrity. This research demonstrates that aqueous Ov-MnO2@MXene-5, with introduced oxygen vacancies, exhibits an outstanding oxygen reduction reaction (ORR) activity with an ORR half-wave potential reaching 0.787 V. DFT calculations have demonstrated that the enhanced activity could be attributed to adjustments in the electronic structure and alterations in adsorption bond lengths. These adjustments result from the introduction of oxygen vacancies, which in turn promote electron transport and catalytic activity. In the context of zinc-air batteries, cells with Ov-MnO2@MXene-5 as the air cathode exhibit outstanding performance, featuring a significantly improved maximum power density (198.3 mW cm-2) and long-term cycling stability. Through the innovative strategy of introducing oxygen vacancies, this study has successfully enhanced the electrochemical catalytic performance of MnO2, overcoming the limitations associated with traditional methods for creating oxygen vacancies. Consequently, this research opens up new avenues and directions for nonprecious metal catalyst application in ZABs.

Catheter ablation versus medical therapy for atrial fibrillation with prior stroke history: a prospective propensity score-matched cohort study.

BACKGROUND: Patients with atrial fibrillation (AF) and prior stroke history have a high risk of cardiovascular events despite anticoagulation therapy. It is unclear whether catheter ablation (CA) has further benefits in these patients. METHODS: AF patients with a previous history of stroke or systemic embolism (SE) from the prospective Chinese Atrial Fibrillation Registry study between August 2011 and December 2020 were included in the analysis. Patients were matched in a 1:1 ratio to CA or medical treatment (MT) based on propensity score. The primary outcome was a composite of all-cause death or ischemic stroke (IS)/SE. RESULTS: During a total of 4.1 ± 2.3 years of follow-up, the primary outcome occurred in 111 patients in the CA group (3.3 per 100 person-years) and in 229 patients in the MT group (5.7 per 100 person-years). The CA group had a lower risk of the primary outcome compared to the MT group [hazard ratio (HR) = 0.59, 95% CI: 0.47-0.74, P < 0.001]. There was a significant decreasing risk of all-cause mortality (HR = 0.43, 95% CI: 0.31-0.61, P < 0.001), IS/SE (HR = 0.73, 95% CI: 0.54-0.97, P = 0.033), cardiovascular mortality (HR = 0.32, 95% CI: 0.19-0.54, P < 0.001) and AF recurrence (HR = 0.33, 95% CI: 0.30-0.37, P < 0.001) in the CA group compared to that in the MT group. Sensitivity analysis generated consistent results when adjusting for time-dependent usage of anticoagulants. CONCLUSIONS: In AF patients with a prior stroke history, CA was associated with a lower combined risk of all-cause death or IS/SE. Further clinical trials are warranted to confirm the benefits of CA in these patients.

A novel esophageal retractor with eccentric balloon during atrial fibrillation ablation.

BACKGROUND: Due to the anatomically adjacent relationship between the left atrium (LA) and esophagus, energy delivery on the posterior wall of LA is limited. The aim of this study was to evaluate the feasibility of a novel esophageal retractor (SAFER) with an inflatable C-curve balloon during atrial fibrillation (AF) ablation. METHOD: Nine patients underwent AF ablation assisted with the SAFER. After inflation, the esophagus was deviated laterally away from the intended ablation site of the posterior wall under local anesthesia. The extent of mechanical esophageal deviation (MED) was evaluated under fluoroscopy, defined as the shortest distance from the trailing esophageal edge to the closest point of the ablation line. Gastroscopy was performed before and after ablation. The target ablation index used in all LA sites including the posterior wall was 400-450 after effective MED. All adverse events during the periprocedural period were recorded. RESULTS: The mean deviation distance achieved 16.2 ± 9.6 mm away from the closest ablation point of the pulmonary vein lesion set. With respect to the individual left and right pulmonary vein lesion sets, the deviation distance was 19.7 ± 11.5 and 12.7 ± 6.8 mm, respectively. The extent of deviation was 0 to 5 mm, 5.1 to 10 mm, or >10 mm in 0(0%), 7(38.9%), and 11(61.1%), respectively. Procedural success was achieved in all patients without acute reconnection. There was only one esophageal complication which manifested as esophageal erosion and this patient experienced throat pain possibly related to the SAFER retractor with no clinical sequelae. CONCLUSION: Esophageal deviation with the novel eccentric balloon is a novel feasible choice during AF ablation, enabling adequate energy delivery to the posterior wall of LA. Additional prospective randomized controlled studies are required for further validation.

Subnanoscale Dual-Site Pd-Pt Layers Make PdPtCu Nanocrystals CO-Tolerant Bipolar Effective Electrocatalysts for Alcohol Fuel Cell Devices.

Finding a high-performance low-Pt bipolar electrocatalyst in actual direct alcohol fuel cells (DAFCs) remains challenging and desirable. Here, we developed a crystalline PdPtCu@amorphous subnanometer Pd-Pt "dual site" layer core-shell structure for the oxygen reduction reaction (ORR) and alcohol (methanol, ethylene glycol, glycerol, and their mixtures) oxidation reaction (AOR) in an alkaline electrolyte (denoted D-PdPtCu). The prepared D-PdPtCu/C achieved a direct 4-electron ORR pathway, a full oxidation pathway for AOR, and high CO tolerance. The ORR mass activity (MA) of D-PdPtCu/C delivered a 52.8- or 59.3-fold increase over commercial Pt/C or Pd/C, respectively, and no activity loss after 20000 cycles. The D-PdPtCu/C also exhibited much higher AOR MA and stability than Pt/C or Pd/C. Density functional theory revealed the intrinsic nature of a subnanometer Pd-Pt "dual site" surface for ORR and AOR activity enhancement. The D-PdPtCu/C as an effective bipolar electrocatalyst yielded higher peak power densities than commercial Pt/C in actual DAFCs.

Structural evolution and strain generation of derived-Cu catalysts during CO2 electroreduction.

Copper (Cu)-based catalysts generally exhibit high C2+ selectivity during the electrochemical CO2 reduction reaction (CO2RR). However, the origin of this selectivity and the influence of catalyst precursors on it are not fully understood. We combine operando X-ray diffraction and operando Raman spectroscopy to monitor the structural and compositional evolution of three Cu precursors during the CO2RR. The results indicate that despite different kinetics, all three precursors are completely reduced to Cu(0) with similar grain sizes (~11 nm), and that oxidized Cu species are not involved in the CO2RR. Furthermore, Cu(OH)2- and Cu2(OH)2CO3-derived Cu exhibit considerable tensile strain (0.43%~0.55%), whereas CuO-derived Cu does not. Theoretical calculations suggest that the tensile strain in Cu lattice is conducive to promoting CO2RR, which is consistent with experimental observations. The high CO2RR performance of some derived Cu catalysts is attributed to the combined effect of the small grain size and lattice strain, both originating from the in situ electroreduction of precursors. These findings establish correlations between Cu precursors, lattice strains, and catalytic behaviors, demonstrating the unique ability of operando characterization in studying electrochemical processes.

Cyanamide Passivation Enables Robust Elemental Imaging of Metal Halide Perovskites at Atomic Resolution.

Lead halide perovskites (LHPs) have attracted a tremendous amount of attention because of their applications in solar cells, lighting, and optoelectronics. However, the atomistic principles underlying their decomposition processes remain in large part obscure, likely due to the lack of precise information about their local structures and composition along regions with dimensions on the angstrom scale, such as crystal interfaces. Aberration-corrected scanning transmission electron microscopy combined with X-ray energy dispersive spectroscopy (EDS) is an ideal tool, in principle, for probing such information. However, atomic-resolution EDS has not been achieved for LHPs because of their instability under electron-beam irradiation. We report the fabrication of CsPbBr3 nanoplates with high beam stability through an interface-assisted regrowth strategy using cyanamide. The ultrahigh stability of the nanoplates primarily stems from two contributions: defect-healing self-assembly/regrowth processes and surface modulation by strong electron-withdrawing cyanamide molecules. The ultrahigh stability of as-prepared CsPbBr3 nanoplates enabled atomic-resolution EDS elemental mapping, which revealed atomically and elementally resolved details of the LHP nanostructures at an unprecedented level. While improving the stability of LHPs is critical for device applications, this work illustrates how improving the beam stability of LHPs is essential for addressing fundamental questions on structure-property relations in LHPs.

Multifunctional polypyrrole@Fe(3)O(4) nanoparticles for dual-modal imaging and in vivo photothermal cancer therapy.

Magnetic Fe3 O4 crystals are produced in situ on preformed polypyrrole (PPY) nanoparticles by rationally converting the residual Fe species in the synthetic system. The obtained PPY@Fe(3)O(4)composite nanoparticles exhibit good photostability and biocompatibility, and they can be used as multifunctional probes for MRI, thermal imaging, and photothermal ablation of cancer cells.

Site-specific growth of Au-Pd alloy horns on Au nanorods: a platform for highly sensitive monitoring of catalytic reactions by surface enhancement Raman spectroscopy.

Surface-enhanced Raman scattering (SERS) is a highly sensitive probe for molecular detection. The aim of this study was to develop an efficient platform for investigating the kinetics of catalytic reactions with SERS. To achieve this, we synthesized a novel Au-Pd bimetallic nanostructure (HIF-AuNR@AuPd) through site-specific epitaxial growth of Au-Pd alloy horns as catalytic sites at the ends of Au nanorods. Using high-resolution electron microscopy and tomography, we successfully reconstructed the complex three-dimensional morphology of HIF-AuNR@AuPd and identified that the horns are bound with high-index {11l} (0.25 < l < 0.43) facets. With an electron beam probe, we visualized the distribution of surface plasmon over the HIF-AuNR@AuPd nanorods, finding that strong longitudinal surface plasmon resonance concentrated at the rod ends. This unique crystal morphology led to the coupling of high catalytic activity with a strong SERS effect at the rod ends, making HIF-AuNR@AuPd an excellent bifunctional platform for in situ monitoring of surface catalytic reactions. Using the hydrogenation of 4-nitrothiophenol as a model reaction, we demonstrated that its first-order reaction kinetics could be accurately determined from this platform. Moreover, we clearly identified the superior catalytic activity of the rod ends relative to that of the rod bodies, owing to the different SERS activities at the two positions. In comparison with other reported Au-Pd bimetallic nanostructures, HIF-AuNR@AuPd offered both higher catalytic activity and greater detection sensitivity.

Graphene substrate-mediated catalytic performance enhancement of Ru nanoparticles: a first-principles study.

The structural, energetic and magnetic properties of Ru nanoparticles deposited on pristine and defective graphene have been thoroughly studied by first-principles based calculations. The calculated binding energy of a Ru(13) nanoparticle on a single vacancy graphene is as high as -7.41 eV, owing to the hybridization between the dsp states of the Ru particles with the sp(2) dangling bonds at the defect sites. Doping the defective graphene with boron would further increase the binding energy to -7.52 eV. The strong interaction results in the averaged d-band center of the deposited Ru nanoparticle being upshifted toward the Fermi level from -1.41 eV to -1.10 eV. Further study reveals that the performance of the nanocomposites against hydrogen, oxygen and carbon monoxide adsorption is correlated to the shift of the d-band center of the nanoparticle. Thus, Ru nanoparticles deposited on defective graphene are expected to exhibit both high stability against sintering and superior catalytic performance in hydrogenation, oxygen reduction reaction and hydrogen evolution reaction.

Site-specific growth of Au particles on ZnO nanopyramids under ultraviolet illumination.

In this work, wurtzite ZnO nanocrystals with unique "pyramid" morphology were firstly prepared via solvothermal synthesis. It was determined that the ZnO nanopyramids are grown along the polar c-axis with the vertexes pointing to the [001] direction. When the mixture of ZnO nanopyramids and Au precursor (HAuCl(4)) was exposed to ultraviolet (UV) illumination, Au particles were site-specifically formed on the vertexes of ZnO nanopyramids. The obtained Au/ZnO nanocomposite showed significantly enhanced photocatalytic activity as compared to the bare ZnO nanopyramids. First-principles based calculations well explained the formation of ZnO nanopyramids as well as the site-specific growth of Au, and revealed that during the photocatalysis process the Au particles can accommodate photoelectrons and thus facilitate the charge separation.

Synthesis, self-assembly, disassembly, and reassembly of two types of Cu2O nanocrystals unifaceted with {001} or {110} planes.

In this work, we describe a solution-based synthesis of monodisperse Cu(2)O nanocrystals with controllable sizes in the nanoscale regime. Two types of nanocrystals, cubes and rhombic dodecahedra unifaceted with either {001} or {110} crystal planes, have been prepared at a 100% morphological yield. In particular, synthetic parameters and formation processes of the Cu(2)O nanocrystals have been investigated in detail, and a range of well-oriented supercrystals/superlattices built from the two types of nanobuilding blocks have been attained for the first time. It has been revealed that n-hexadecylamine used in the present work plays multiple roles: it serves as a chelating ligand to form [Cu(NH(2)C(16)H(33))(4)](2+) complex precursor, as a phase-transferring agent to transfer divalent Cu(2+) ions into the organic phase, as a reducing agent to generate monovalent Cu(+) (i.e., Cu(2)O), as a passivating adsorbate to control crystal morphology, and as a surface capping agent to generate self-assemblies of nanocrystals via van der Waals interaction. Apart from synthesis and self-assembly, disassembly and reassembly of Cu(2)O nanocrystals have also been investigated. The disassembly processes are accompanied with aggregative growths of nanocrystals, which can be attributed to a combined process of "oriented attachment" and Ostwald ripening, leading to permanent engagement and enlargement of nanocrystals. Finally, our self-assembled nanocrystals of Cu(2)O show a lower detection limit, lower operating temperature, and higher sensitivity in ethanol vapor detection, compared with other Cu(2)O-based alcohol sensors reported in the recent literature. A greater depletion layer of carrier and a relatively small contact potential may account for the observed sensing enhancement in the sensors made from the organized Cu(2)O nanocrystals.

Fabrication and surface properties of composite films of SAM/Pt/ZnO/SiO2.

Through synthetic architecture and functionalization with self-assembled monolayers (SAMs), complex nanocomposite films of SAM/Pt/ZnO/SiO2 have been facilely prepared in this work. The nanostructured films are highly uniform and porous, showing a wide range of tunable wettabilities from superhydrophilicity to superhydrophobicity (water contact angles: 0 degrees to 170 degrees ). Our approach offers synthetic flexibility in controlling film architecture, surface topography, coating texture, crystallite size, and chemical composition of modifiers (e.g., SAMs derived from alkanethiols). For example, wettability properties of the nanocomposite films can be finely tuned with both inorganic phase (i.e., ZnO/ SiO2 and Pt/ZnO/SiO2) and organic phase (i.e., SAMs on Pt/ZnO/SiO2). Due to the presence of catalytic components Pt/ZnO within the nanocomposites, surface reactions of the organic modifiers can further take place at room temperature and elevated temperatures, which provides a means for SAM formation and elimination. Because the Pt/ZnO forms an excellent pair of metal-semiconductors for photocatalysis, the anchored SAMs can also be modified or depleted by UV irradiation (i.e., the films possess self-cleaning ability). Potential applications of these nanocomposite films have been addressed. Our durability tests also confirm that the films are thermally stable and structurally robust in modification-regeneration cycles.

Asymmetric ZnO nanostructures with an interior cavity.

As a next level of nanofabrication of inorganic materials, free-standing asymmetric nanostructures with an interior space are highly desirable for new applications. In this work, we demonstrate a wet synthesis scheme for bullet-head-like nanostructures of wurtzite zinc oxide (ZnO). The synthesized asymmetric nanostructures are single crystalline, and each has an interior space. In addition to the exterior geometric anisotropy, it is found that the interior space is located at the upper part of the ZnO nanostructures; a new type of structural anisotropy has thus been revealed. On the basis of the present findings, in principle, this synthetic architecture should be applicable to other II-VI compound semiconductors through stabilizing two or more sets of crystallographic planes in solution media. The possibility of dimerization and higher ordered coupling/growth of the ZnO nanostructures has also been addressed.