Co3O4 Hollow Polyhedrons as Bifunctional Electrocatalysts for Reduction and Evolution Reactions of Oxygen

It is very important to exploit low‐cost and efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts for the development of renewable‐energy conversion and storage techniques. Although much attention has been made to develop efficient catalysts for ORR and OER, it is still highly desired to create new bifunctional catalysts. In this study, Co₃O₄ hollow polyhedrons are synthesized as efficient bifunctional electrocatalysts for ORR and OER by simple one‐step annealing Co‐centered metal–organic frameworks (ZIF‐67). Due to the large specific surface areas and high porosity, the as‐prepared Co₃O₄ hollow polyhedrons exhibit excellent electrocatalytic activities for ORR and OER in alkaline media. Co₃O₄ hollow polyhedrons show higher peak current density (0.61 mA cm^?2) with four‐electron pathway than Co₃O₄ particles (0.39 mA cm^?2), better methanol tolerance and superior durability (82.6%) than commercial Pt/C electrocatalyst (58.6%) for ORR after 25 000 s. In addition, Co₃O₄ hollow polyhedrons also display excellent OER performances with smaller overpotential (536 mV) for 10 mA cm^?2 than Co₃O₄ particles (593 mV) and superior stability (86.5%) after 25 000 s. This facile one‐step strategy based on metal–organic frameworks self‐sacrificed templates can be used to develop the promising well‐defined porous hollow metal oxides electrode materials for energy conversion and storage technologies.     

A High‐Performance Anode Material for Li‐Ion Batteries Based on a Vertically Aligned CNTs/NiCo2O4 Core/Shell Structure

3D vertically aligned carbon nanotubes (CNTs)/NiCo₂O₄ core/shell structures are successfully synthesized as binder‐free anode materials for Li‐ion batteries (LIBs) via a facile electrochemical deposition method followed by subsequent annealing in air. The vertically aligned CNTs/NiCo₂O₄ core/shell structures are used as binder‐free anode materials for LIBs and exhibit high and stable reversible capacity (1147.6 mAhg^?1 at 100 mAg^?1), excellent rate capability (712.9 mAh g^?1 at 1000 mAg^?1), and good cycle stability (no capacity fading over 200 cycles). The improved performance of these LIBs is attributed to the unique 3D vertically aligned CNTs/NiCo₂O₄ core/shell structures, which support high electron conductivity, fast ion/electron transport in the electrode and at the electrolyte/electrode interface, and accommodate the volume change during cycling. Furthermore, the synthetic strategy presented can be easily extended to fabricate other metal oxides with a controlled core/shell structure, which may be a promising electrode material for high‐performance LIBs.     

Preparation of Highly Stable and Photoluminescent Cadmium-Free InP/GaP/ZnS Core/Shell Quantum Dots and Application to Quantitative Immunoassay

Indium phosphide (InP) quantum dots (QDs) are ideal substitutes for widely used cadmium-based QDs and have great application prospects in biological fields due to their environmentally benign properties and human safety. However, the synthesis of InP core/shell QDs with biocompatibility, high quantum yield (QY), uniform particle size, and high stability is still a challenging subject. Herein, high quality (QY up to 72%) thick shell InP/GaP/ZnS core/shell QDs (12.8 ± 1.4 nm) are synthesized using multiple injections of shell precursor and extension of shell growth time, with GaP serving as the intermediate layer and 1-octanethiol acting as the new S source. The thick shell InP/GaP/ZnS core/shell QDs still keep high QY and photostability after transfer into water. InP/GaP/ZnS core/shell QDs as fluorescence labels to establish QD-based fluorescence-linked immunosorbent assay (QD-FLISA) for quantitative detection of C-reactive protein (CRP), and a calibration curve is established between fluorescence intensity and CRP concentrations (range: 1–800 ng mL⁻¹, correlation coefficient: R² = 0.9992). The limit of detection is 2.9 ng mL⁻¹, which increases twofold compared to previously reported cadmium-free QD-based immunoassays. Thus, InP/GaP/ZnS core/shell QDs as a great promise fluorescence labeling material, provide a new route for cadmium-free sensitive and specific immunoassays in biomedical fields.     

NiWO3 Nanoparticles Grown on Graphitic Carbon Nitride (g‐C3N4) Supported Toray Carbon as an Efficient Bifunctional Electrocatalyst for Oxygen and Hydrogen Evolution Reactions

Catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are at the heart of water oxidation reactions. Despite continuous efforts, the development of OER/HER electrocatalysts with high activity at low cost remains a big challenge. Herein, a composite material consisting of TC@WO₃@g‐C₃N₄@Ni‐NiO complex matrix as a bifunctional electrocatalyst for the OER and HER is described. Though the catalyst has modest activity for HER, it exhibits high OER activity thereby making it a better nonprecious electrocatalyst for both OER and HER and is further improved by g‐C₃N₄. The catalytic activity arises from the synergetic effects between WO₃, Ni‐NiO, and g‐C₃N₄. A Ni‐NiO alloy and WO₃ nanoparticles decorated on the g‐C₃N₄ surface supported toray carbon (TC) matrix (TC@WO₃@g‐C₃N₄@Ni‐NiO) by a facile route that show an excellent and durable bifunctional catalytic activity for OER and HER in the alkaline medium are developed. This carbon nitride with binary metal/metal‐oxide matrix supported with TC exhibit an overpotential of 0.385 and 0.535 V versus RHE at a current density of 10 mA cm^?2 (Tafel slopes of 0.057 and 0.246 V dec^?1 for OER and HER, respectively), in 0.1 m NaOH . The catalyst is tested in water electrolysis for 17 h.     

Tb(Asprin)_3Phen/SiO_2壳/核型纳米材料的合成和光学性质

利用W/O微乳液方法合成了直径为40 nm的具有类壳/核结构的Tb(Asprin)3Phen/SiO2纳米球.透射电子显微镜(TEM)证实了该纳米球具有尺寸均一,分散性好的特点.另外,通过TEOS与APS在微乳液中同时水解,在材料的表面引入了大量的氨基,为材料的生物应用提供了有利的条件.红外光谱(FT-IR)和光致发光光谱分析也显示了这种材料在生物领域中有着潜在的应用前景.     

MFe2O4 and MFe@Oxide Core–Shell Nanoparticles Anchored on N‐Doped Graphene Sheets for Synergistically Enhancing Lithium Storage Performance and Electrocatalytic Activity for Oxygen Reduction Reactions

The intrinsically low electric conductivity and self‐aggregation of MFe₂O₄ during charge/discharge affect their lithium storage performance and electrocatalytic activity. To mitigate these problems, it is shown that N‐doped graphene sheets (NGS), as a highly conductive platform, finely disperse the MFe₂O₄ nanoparticles and rapidly shuttle electrons to and from the MFe₂O₄ nanoparticles. Moreover, by forming a metal@oxide core–shell nanostructure, fast electron transfer from the exterior oxide layer to NGS is achieved. Introducing NGS into MFe₂O₄ allows the composites to exhibit the comparable specific capacity (based on the total mass) to MFe₂O₄, although over 10 wt% of NGS contributes a low specific capacity of around 320–400 mAh g^?1. More importantly, introducing NGS significantly increases the cycling stability performance: 97.5% (CoFe₂O₄/NGS) and ≈100% (NiFe₂O₄/NGS) of the specific capacities have been retained after 80 cycles, far higher than the capacity retentions of CoFe₂O₄ (35.3%) and NiFe₂O₄ (43.7%) tested under otherwise identical conditions. Also demonstrated are the excellent rate capabilities of the composites. For catalyzing the oxygen reduction reaction, the activity is significantly improved when the MFe₂O₄ nanoparticles are transformed into metal@oxide core–shell nanostructure, mainly because the core–shell nanostructure exhibits lower charge transfer resistance.     

A facile one-pot ultrasound assisted for an efficient synthesis of benzo[g]chromenes using Fe3O4/polyethylene glycol (PEG) core/shell nanoparticles

In this research, a general synthetic method for the synthesis of benzo[g]chromenes has been developed using Fe₃O₄/polyethylene glycol (PEG) core/shell nanoparticle under ultrasonic irradiations. Compared to the conventional methods, ultrasound procedure showed several advantages including mild reaction conditions, high yield products, short reaction times, reusability of the catalyst and little catalyst loading.