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Based on signal amplification strategy of dendritic mesoporous silica nanospheres loaded with CdSe/ZnS quantum dots (DMSN@QDs), an ultrasensitive electrochemiluminescence (ECL) immunosensor with magnetic separation was constructed for the detection of SARS-CoV-2 nucleocapsid protein (NP). DMSN, a mesoporous material with abundant radial pores, large specific surface area and high porosity, can increase the loading capacity of QDs and hinder their aggregation as the nanocarrier. DMSN@QDs with good ECL efficiency were used as signal labels to construct a sandwich immunosensor. The designed ECL immunosensor displayed a good linear relationship for NP concentrations ranging from 0.005 ng mL−1 to 50 ng mL−1, with a limit of detection of 3.33 pg mL−1. The ECL immunosensor was successfully applied to detect NP in human serum samples with satisfactory recovery. This strategy provided a new method for detecting NP and expanded the application field of DMSN. [ABSTRACT FROM AUTHOR]

Ammonia borane (NH3BH3, AB) has attracted attention as a carbon-free energy source owing to its non-toxicity, high solubility in water, and high stability under ambient conditions. Unlike its traditional application as an efficient hydrogen storage material, AB has the potential to be used in alkaline fuel cells directly as an anode fuel. The direct ammonia borane fuel cell (DABFC) with a high equilibrium voltage of 1.616 V possesses high capacity and energy density with a value of 5200 A h kg−1 and 8400 W h kg−1, respectively. The AB oxidation reaction (ABOR) as the anodic reaction of the DABFC is the key to improving the electrochemical performance of the whole fuel cell. Up to now, there has been no report summarizing the direct application of AB as a fuel. In this mini-review, the mechanism, catalysts, applications, and challenges of AB applied as a fuel are discussed. [ABSTRACT FROM AUTHOR]

Ammonia borane (NH3BH3, AB), a carbon-free-energy material, has attracted enormous attention not only as the hydrogen storage source but also as the anodic fuel for direct AB fuel cells (DABFCs). The rational design of electrocatalysts for AB oxidation reaction (ABOR) is the key to improve the electrochemical performance of DABFCs. Herein, copper-doped nickel metaphosphates (Cu–Ni(PO3)2) with modulated electronic structure and abundant lattice defects through tuning dopant ratios are synthesized and applied towards ABOR for the first time. The optimal Cu–Ni(PO3)2 catalyst shows excellent electrocatalytic performance with an onset potential of −0.282 V versus the reversible hydrogen electrode (vs. RHE) which is superior to the published noble-metal and other transition metal electrocatalysts. And the density functional theory (DFT) computations verified that the active sites in the Cu–Ni(PO3)2 towards ABOR are the dopant Cu ions, the optimized Ni ions, and the induced lattice distortions, which indicates that the doping of Cu ions can indeed improve the electrocatalytic activity of the host catalyst Ni(PO3)2. This work provides a new candidate for the electrocatalyst of ABOR. [ABSTRACT FROM AUTHOR]

Engineering delicate structures/morphologies and coordinated components of electrocatalysts are of great importance to optimize physicochemical properties of materials and thus enhance their electrocatalytic performance. Herein, we demonstrate a facile sequential template-engaged strategy for fabricating Co–Ni–Fe phosphide hollow nanoboxes with hierarchical structures and desired hetero-metal compositions (Co–Ni–Fe–P HNBs). Starting from ZIF-67 templates, binary-metal Co–Ni and ternary-metal Co–Ni–Fe HNBs are sequentially synthesized and further phosphidated into hetero-metal Co–Ni–Fe–P HNBs. As-resultant Co–Ni–Fe–P HNBs endow multiple structural and compositional merits that expose abundant active sites, accelerate mass/ion diffusion and optimize adsorption energies of oxygen and hydroxyl groups, thus kinetically promoting electrocatalytic oxygen evolution reaction (OER). Specifically, Co–Ni–Fe–P HNBs disclose remarkable OER activity with an overpotential of 249 mV at 10 mA cm−2 and stability with 86% activity retained over 24 h, which represents one of the toppest values of OER electrocatalysts. This work thus paves an effective protocol to rationally engineer hierarchical and hetero-metal electrocatalysts towards targeted applications. [ABSTRACT FROM AUTHOR]

The rational construction of the chemical composition and morphological structure of electrocatalysts has been considered as the key to their electrochemical performance and energy storage. Herein, we report the facile fabrication of the hierarchical Ni2P–Co2P–Fe2P hybrid hollow nanoprism (abbreviated as NiCoFeP-HN), which could efficiently work as the oxygen evolution reaction (OER) electrocatalyst in the rechargeable Zn–air battery. NiCoFeP-HN was synthesized via an in situ ion exchange reaction of nickel–cobalt precursors with [Fe(CN)6]3− at room temperature and the subsequent phosphorization at 300 °C under N2. The ion exchange procedure was crucial for preserving the nanoprism morphology and enhancing the OER performance. NiCoFeP-HN exhibited satisfactory activity with a small overpotential of 294 mV at 10 mA cm−2 and remarkable stability for over 12 h. Compared to the conventional RuO2 + Pt/C Zn–air battery, the NiCoFeP-HN + Pt/C based Zn–air battery has exhibited superior energy density and much better cycling stability. This work presents a facile and efficient avenue for the construction of hollow nanostructures and hybrid compositions, and provides a promising candidate with good electrochemical performance and energy storage. [ABSTRACT FROM AUTHOR]

The current study reports a new, simple and fast method using a flake-like dysprosium molybdate (Dy2MoO6; FL-DyM) nanostructured material to detect the antibiotic drug metronidazole (METZ). This nanocomposite material was employed on the surface of a glassy carbon electrode (GCE) to develop the electrode (FL-DyM/GCE). Further, the synthesized FL-DyM was systematically characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray diffraction (EDS), elemental mapping, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analyses. Cyclic (CV) and differential pulse voltammetry (DPV) techniques were used to study the electrochemical properties. The FL-DyM/GCE-based sensor demonstrated excellent selectivity and sensitivity for the detection of the drug METZ, which could be attributed to the strong affinity of FL-DyM towards the –NO2 group in METZ, and the good electrocatalytic activity and conductivity of FL-DyM. The fabrication and optimization of the working electrode were accomplished with CV and DPV obtained by scan rate and pH studies. Compared to the bare GCE and other rare-earth metal molybdates, the FL-DyM/GCE sensor displayed a superior electrocatalytic activity response for METZ detection. The sensor demonstrated a good linear relationship over the concentration range of 0.01–2363 μM. The quantification and detection limits were found to be 0.010 μM and 0.0030 μM, respectively. The FL-DyM/GCE sensor displayed excellent selectivity, repeatability, reproducibility, and stability for the detection of METZ in human urine and commercial METZ tablet samples, which validates the new technique for efficient drug sensing in practical applications. [ABSTRACT FROM AUTHOR]

Nb2O5@carbon/reduced graphene oxide (M-Nb2O5@C/rGO) composites are fabricated by annealing the precursor of graphene oxide supported Nb-based metal organic frameworks for the first time. The lithium ion capacitor using M-Nb2O5@C/rGO as the anode and activated carbon as the cathode delivers a high energy density of 71.5 W h kg−1 and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Binder-free electrodes with core–shell structures have shown great potential in a variety of important energy storage systems. In order to endow the core–shell hierarchical structure with enhanced electrochemical properties, rationally designed and fabricated hierarchical structures with controllable morphology and great electrical conductivity are highly desired. In this work, a uniform dendritic S-Co3O4@NiCo2S4 hierarchical structure grown on Ni foam was successfully designed and synthesized via sulfur-doping of Co3O4 (S-Co3O4) as the inner core with enhanced conductivity. The hierarchical electrode exhibited high areal capacity (10.9 mA h cm−2 at a current density of 8 mA cm−2), a good rate performance (72.5% retention after increasing the current densities from 8 to 30 mA cm−2), and excellent cycling stability (97.3% retention after 5000 cycles). Moreover, a hybrid energy storage battery-supercapacitor device, constructed from a S-Co3O4@NiCo2S4 positive electrode and an active carbon (AC) negative electrode, showed high energy density and power density. Contributing to short ion diffusion, large electroactive sites and low contact resistance, our work not only demonstrates a promising electrode for energy storage battery-supercapacitor hybrid (BSH) devices, but also provides an attractive strategy for the design of electrode materials. [ABSTRACT FROM AUTHOR]

It is of great practical importance to design low-cost materials as catalysts for the oxygen reduction reaction (ORR) and as an anode for sodium–ion batteries (SIBs). In this paper, we report a class of nitrogen-doped carbon materials with a three-dimensional nanofibrous network derived from inexpensive biomass bacterial cellulose (BC) for both ORR and SIB applications. The samples were prepared by treating the BC aerogels with various amounts of pyrrole to ensure a uniform coating on the surface of the BC nanofibers, followed by a carbonization process under different temperatures. The products were essentially carbon nanofibers coated by a nitrogen-doped carbon layer and retained the initial structure of BC. The optimum amount of pyrrole was 0.05 mL and the optimum carbonization temperature was 900 °C. Our best catalyst exhibited good electrocatalytic performance and durability in ORR, without the presence of noble metals. An electrode made from the same material has also demonstrated a stable cycling performance and superior rate capability in SIB application. Our work has demonstrated a rational design of electroactive carbon materials from a low-cost precursor. [ABSTRACT FROM AUTHOR]

We have successfully prepared poly (3,4-ethylenedioxythiophene) (PEDOT)/N-doped reduced graphene oxide (N-rGO) by electrodeposition, post-reduction, and doping N atoms with a microorganism (as a green reagent) to modify PEDOT and resolve the exfoliation and fragmentation problems of pristine PEDOT. This modification greatly improves the electrochemical properties of PEDOT, showing great potential for a bio-electrode coating material, which should have excellent electrochemical properties, stability and biocompatibility. The as-prepared PEDOT/N-rGO shows lower impedance, and higher capacitive performance and cyclical stability than pristine PEDOT due to the doping of N-rGO. An MTT assay demonstrates this modified PEDOT has good adhesion, cell viability and proliferation, similar to pristine PEDOT. This indicates that the modification process does not restrain the good biocompatibility of pristine PEDOT, which results from the doping of highly biocompatible N-rGO by this green method. The wrinkled structure, residual oxygen containing functional groups and dopant N atoms of N-rGO lead to the formation of a fluctuating surface and an increase in the hydrophilicity of PEDOT, which increase the specific surface area and cell adhesion in cell culture, respectively. Consequently, this modified PEDOT improves the electrochemical properties, and resolves the exfoliation and fragmentation problems of pristine PEDOT, while still retaining the high biocompatibility of pristine PEDOT, which is promising for a bio-electrode coating material. [ABSTRACT FROM AUTHOR]

Nb2O5@carbon/reduced graphene oxide (M-Nb2O5@C/rGO) composites are fabricated by annealing the precursor of graphene oxide supported Nb-based metal organic frameworks for the first time. The lithium ion capacitor using M-Nb2O5@C/rGO as the anode and activated carbon as the cathode delivers a high energy density of 71.5 W h kg-1 and excellent cycling stability.

The large-scale synthesis of ternary nanocomposite hemin-graphene sheets/poly(3,4-ethylenedioxythiophene) (H-GNs/PEDOT) was achieved via a microwave-assisted method, in which PEDOT was polymerized with graphene oxide and induced with hemin on the H-GNs nanosheets without additional oxidants; meanwhile, graphene oxide was partially reduced simultaneously. The morphology and structure of the as-prepared nanocomposites were characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, and ultraviolet-visible absorption spectroscopy. The H-GNs/PEDOT nanocomposite combines the main excellent properties of the three components, maintaining the peroxidase-like activity of hemin, and displaying a high-speed electron transfer ascribed to the presence of PEDOT and the graphene sheets. The H-GNs/PEDOT exhibited remarkable electrocatalysis towards the reduction of H 2 O 2 due to the direct electron-transfer between the hemin and the modified electrode. The excellent synergic effect enables an enhanced electrochemical performance of the H-GNs/PEDOT modified electrode with good biocompatibility and fast redox property. The novel biomimetic H 2 O 2 biosensor based on the well-designed ternary hybrid H-GNs/PEDOT has a low detection limit (0.08 μM) with a high dynamic response range (10 -7 to 10 -5 M) and a high sensitivity (235 μA mM -1  cm -2 ). The sensor displays good selectivity, repeatability, reproducibility and stability.