Nickel-Doped Ultrathin K‑Birnessite Manganese Oxide Nanosheet As Pseudocapacitor Electrode with Excellent Cycling Stability for High-Power Pesudocapacitors

We herein report a kind of nickel-doped ultrathin δ-MnO₂ nanosheets prepared using a facile chemical bath deposition method. The obtained δ-MnO₂ materials have 2D ultrathin nanosheet structures with a few atomic layers. Electrochemical measurements indicate that an appropriate amount of nickel doping can remarkably improve the specific capacitance of the δ-MnO₂ and that 1.0 mol % nickel-doped δ-MnO₂ nanosheets display the best specific capacitance of 337.9 F g^–1 at 1 A g^–1. The specific capacitance can maintain at 158 F g^–1 even as the current density increases to 20 A g^–1, demonstrating that the electrode material possesses good rate performance. In addition, the discharge capacity fading from 160.9 to 158.8 F g^–1 is slight after 4000 cycles, and the corresponding capacitance retention is as high as 98.6%. The good rate capacity and stability of the δ-MnO₂ nanosheets can be attributed to the ultrathin structure of a few atomic layers which provides large surface areas and lots of reactive active sites. Moreover, the appropriate amount of nickel ion doping at atomic level improves the conductivity of the δ-MnO₂ material

One-Pot Synthesis of Monodisperse Noble Metal @ Resorcinol-Formaldehyde (M@RF) and M@Carbon Core–Shell Nanostructure and Their Catalytic Applications

We demonstrate that noble metal @ RF core–shell nanostructures can be obtained through a facile one-pot synthesis approach in the absence of any additional surfactants. Monodisperse metal@RF core–shell nanostructures can be produced within 1 h on a large scale. Both the core size and shell thickness can be readily tuned by altering the reaction parameters. Systematic studies reveal that resorcinol could have several functions: it could act as a reactant to form RF resin, and it also could passivate the surface of metallic nanoparticles to prevent them from aggregating. Additionally, for the first time, our results suggest that resorcinol may act as a reducing agent that can reduce metal salts to form metal nanoparticles. The core–shell nanoparticles can be carbonized into M@carbon nanostructures, which have shown great performance in the catalytic hydrogenation of chlorobenzene. This work not only will help to achieve the controllable synthesis of noble metal@RF resin and M@carbon core–shell nanostructures but also will promote research into other RF-based nanostructures and their catalytic applications

Self-Assembly of CdS/CdIn₂S₄ Heterostructure with Enhanced Photocascade Synthesis of Schiff Base Compounds in an Aromatic Alcohols and Nitrobenzene System with Visible Light

A series of novel CdS/CdIn2S4 composite materials were prepared via a one-pot solvothermal process. The as-obtained photocatalysts were characterized by several techniques and the photocatalytic properties of CdS/CdIn2S4 photocatalysts were studied by photocascade synthesis of Schiff base compounds in a photocatalytic reaction system of aromatic alcohols and nitrobenzene irradiated with visible light. The results reveal that the resulting CdS/CdIn2S4 heterostructure samples show outstanding photocatalytic activities toward the photocascade production of Schiff base compounds in an aromatic alcohols and nitrobenzene reaction system irradiated with visible light. An optimized 50.0% CdS/CdIn2S4 heterostructure sample shows the highest Schiff base yield of 42.0% irradiated with visible light for 4 h, which is approximately 19.1 and 1.54 times higher than those of sole CdS and CdIn2S4 samples, respectively. The fabrication of heterogeneous structure improves the spatial separation and migration of photoinduced electron–hole pairs, thus contributing to the enhancement of photocatalytic properties. We foresee that this finding can offer a strategy to develop heterostructure composites for efficient synthesis of organics by photocatalysis under mild conditions

Fluorine-doped graphene with outstanding electrocatalytic performance for highly efficient oxygen reduction reaction in alkaline solution

Doping carbon materials have proved to be the front runners to substitute for Pt as oxygen reduction reaction (ORR) catalysts. Fluorine-doped graphene (FG) has rarely been used as ORR catalyst because of the difficulty in preparation. Herein, we report FG sheets prepared by a thermal pyrolysis GO process in the presence of zinc fluoride (ZnF2) as an efficient electrocatalyst for ORR in the alkaline medium. The results show that the pyrolysis temperature seriously affected the doped fluoride amount and morphology of catalyst. It is found that the FG-1100 catalyst possesses a more positive onset potential, higher current density and better four-electron process for ORR than other FG samples. FG-1100 displays an outstanding ORR catalytic activity that is comparable to that of the commercial Pt/C catalyst. Also, its durability and methanol tolerance ability are superior to those of the commercial Pt/C. The excellent ORR catalytic performance is closely related to its higher doped fluorine amount and wrinkle morphology. The FG catalyst can be developed as a low-cost, efficient and durable catalyst as a viable replacement for the Pt/C catalyst, promoting the commercialization of fuel cells

Encapsulated Silver Nanoparticles Can Be Directly Converted to Silver Nanoshell in the Gas Phase

We report, for the first time, that an encapsulated silver nanoparticle can be directly converted to a silver nanoshell through a nanoscale localized oxidation and reduction process in the gas phase. Silver can be etched when exposed to a mixture of NH₃/O₂ gases through a mechanism analogous to the formation of aqueous Tollens’ reagent, in which a soluble silver–ammonia complex was formed. Starting with Ag@resorcinol-formaldehyde (RF) resin core–shell nanoparticles, we demonstrate that RF-core@Ag-shell nanoparticles can be prepared successfully when the etching rate and RF thickness were well controlled. Due to the strong surface plasmon resonance (SPR) coupling effect among neighboring silver nanoparticles, the RF@Ag nanoparticle showed great SPR and SERS performance. This process provides a general route to the conversion of Ag-core to Ag-shell nanostructures and might be extended to other systems

Atomically Dispersed Mg–N–C Material Supported Highly Crystalline Pt₃Mg Nanoalloys for Efficient Oxygen Reduction Reaction

Single-atom or atomically dispersed metal materials have emerged as highly efficient catalysts, but their potential as excellent supports has rarely been reported. In this work, we prepared Mg–N–C materials derived from annealing of a Mg-based metal–organic framework (MOF). By introducing Pt, Mg–N–C not only serves as a platform for anchoring Pt nanoparticles but also facilitates the integration of Mg into the Pt face-centered cubic lattice, resulting in the formation of highly crystalline Pt3Mg nanoalloys via the metal–support interfacial interaction. Synchrotron radiation-based X-ray absorption spectroscopy (XAS) enables us to study the interfacial interaction and the surface electronic structure of this intricate system. The formation of Pt3Mg nanoalloys induces a downshift of the Pt d-band (gaining d-charge), as revealed by the decrease in the Pt L3-edge white-line (WL) area under the curve. This downshift can weaken the binding of oxygen reduction reaction (ORR) intermediates, hence improving the ORR performance

<i>In Situ</i> Molecular Engineering Strategy to Construct Hierarchical MoS₂ Double-Layer Nanotubes for Ultralong Lifespan “Rocking-Chair” Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc ion batteries (AZIBs) have gained considerable attention owing to their low cost and high safety, but dendrite growth, low plating/stripping efficiency, surface passivation, and self-erosion of the Zn metal anode are hindering their application. Herein, a one-step in situ molecular engineering strategy for the simultaneous construction of hierarchical MoS2 double-layer nanotubes (MoS2-DLTs) with expanded layer-spacing, oxygen doping, structural defects, and an abundant 1T-phase is proposed, which are designed as an intercalation-type anode for “rocking-chair” AZIBs, avoiding the Zn anode issues and therefore displaying a long cycling life. Benefiting from the structural optimization and molecular engineering, the Zn2+ diffusion efficiency and interface reaction kinetics of MoS2-DLTs are enhanced. When coupled with a homemade ZnMn2O4 cathode, the assembled MoS2-DLTs//ZnMn2O4 full battery exhibited impressive cycling stability with a capacity retention of 86.6% over 10 000 cycles under 1 A g–1anode, outperforming most of the reported “rocking-chair” AZIBs. The Zn2+/H+ cointercalation mechanism of MoS2-DLTs is investigated by synchrotron in situ powder X-ray diffraction and multiple ex situ characterizations. This research demonstrates the feasibility of MoS2 for Zn-storage anodes that can be used to construct reliable aqueous full batteries

Additional file 1 of An explainable artificial intelligence framework for risk prediction of COPD in smokers

Additional file 1: Supplementary Table S1. Sampling process of survey subjects for COPD surveillance in China. Supplementary Table S2. Parameter setting. Supplementary Table S3. Detection rate of COPD with categorical variable of different populations. Supplementary Table S4. Detection rate of COPD with continuous variable of different populations. Supplementary Table S5. Sample situation. Supplementary Table S6. Distribution of train/test data

Unveiling the Local Structure and Electronic Properties of PdBi Surface Alloy for Selective Hydrogenation of Propyne

Building a reliable relationship between the electronic structure of alloyed metallic catalysts and catalytic performance is important but remains challenging due to the interference from many entangled factors. Herein, a PdBi surface alloy structural model, by tuning the deposition rate of Bi atoms relative to the atomic interdiffusion rate at the interface, realizes a continuous modulation of the electronic structure of Pd. Using advanced X-ray characterization techniques, we provide a precise depiction of the electronic structure of the PdBi surface alloy. As a result, the PdBi catalysts show enhanced propene selectivity compared with the pure Pd catalyst in the selective hydrogenation of propyne. The prevented formation of saturated β-hydrides in the subsurface layers and weakened propene adsorption on the surface contribute to the high selectivity. Our work provides in-depth understanding of the electronic properties of surface alloy structure and underlies the study of the electronic structure–performance relationship in bimetallic catalysts

Assembly, Two-Photon Absorption, and Bioimaging of Living Cells of A Cuprous Cluster

A novel cuprous­(I) cluster Cu4I4L4 (L = (E)-(4-diethylanilino-styryl)­pyridine) bearing strong two-photon absorption (TPA) was obtained using a facile assembly method, and the crystal structure has been determined. Quantum chemical calculations using time-dependent density functional theory (TD-DFT) reveals that the combination of the organic ligands with the three-dimensional Cu4I4 core extends the electronic delocalization in the cluster, leading to strong two-photon absorption action. The TPA cross sections (Φσ2) of Cu4I4L4 were enhanced with increasing polarity of solvents, which is quite different from the solvent effects on TPA in the literature. Compared to its free ligand, the cluster Cu4I4L4 exhibits larger peak TPA cross sections in the near-infrared region, longer fluorescence lifetimes, higher quantum yield and photostability, lower cytotoxicity, and brighter two-photon fluorescent (TPF) bioimaging. These integrated advantages make it desirable to be applied as a two-photon fluorescent probe for labeling the nucleic acids in live cells