Hollow Nitrogen-doped Fe3O4/Carbon Nanocages with Hierarchical Porosities as Anode Materials for Lithium-ion Batteries

Biofuel cell-based self-powered immunosensor for detection of 17β-estradiol by integrating the target-induced biofuel release and biogate immunoassay

A novel biofuel cell (BFC)-based self-powered electrochemical immunosensing platform was developed by integrating the target-induced biofuel release and biogate immunoassay for ultrasensitive 17β-estradiol (E2) detection. The carbon nanocages/gold nanoparticle composite was employed in the BFCs device as the electrode material, through which bilirubin oxidase and glucose oxidase were wired to form the biocathode and bioanode, respectively. Positively charged mesoporous silica nanoparticles (PMSN) were encapsulated with glucose molecules as biofuel and subsequently coated by the negatively charged AuNPs-labelled anti-E2 antibody (AuNPs-Ab) serving as a biogate. The biogate could be opened efficiently and the trapped glucose released once the target E2 was recognized and captured by AuNPs-Ab due to the decreased adhesion between the antigen-antibody complex and PMSN. Then, glucose oxidase oxidized the glucose to produce a large number of electrons, resulting in significantly increased open-circuit voltage (EOCV). Promisingly, the proposed BFC-based self-powered immunosensor demonstrated exceptional sensitivity for the detection of E2 in the concentration range from 1.0 pg mL-1 to 10.0 ng mL -1, with a detection limit of 0.32 pg mL-1 (S/N = 3). Furthermore, the prepared BFC-based self-powered homogeneous immunosensor showed significant potential for implementation as a viable prototype for a mobile and an on-site bioassay system in food and environmental safety applications.

A self-powered electrochemical aptasensor for the detection of 17β-estradiol based on carbon nanocages/gold nanoparticles and DNA bioconjugate mediated biofuel cells

17β-Estradiol (E2) is an important endogenous estrogen, which disturbs the endocrine system and poses a threat to human health because of its accumulation in the human body. Herein, a biofuel cell (BFC)-based self-powered electrochemical aptasensor was developed for E2 detection. Porous carbon nanocage/gold nanoparticle composite modified indium tin oxide (CNC/AuNP/ITO) and glucose oxidase modified CNC/AuNP/ITO were used as the biocathode and bioanode of BFCs, respectively. [Fe(CN)6]3- was selected as an electroactive probe, which was entrapped in the pores of positively charged magnetic Fe3O4 nanoparticles (PMNPs) and then capped with a negatively charged E2 aptamer to form a DNA bioconjugate. The presence of the target E2 triggered the entrapped [Fe(CN)6]3- probe release due to the removal of the aptamer via specific recognition, which resulted in the transfer of electrons produced by glucose oxidation at the bioanode to the biocathode and produced a high open-circuit voltage (EOCV). Consequently, a "signal-on" homogeneous self-powered aptasensor for E2 assay was realized. Promisingly, the BFC-based self-powered aptasensor has particularly high sensitivity for E2 detection in the concentration range of 0.5 pg mL-1 to 15 ng mL-1 with a detection limit of 0.16 pg mL-1 (S/N = 3). Therefore, the proposed BFC-based self-powered electrochemical aptasensor has great promise to be applied as a successful prototype of a portable and on-site bioassay in the field of environment monitoring and food safety.

Tailored synthesis of NdMnxFe1-xO3 perovskite nanoparticles with oxygen-vacancy defects for lithium-ion battery anodes

In this study, we synthesize nanostructured NdMnxFe1-xO3 perovskites using a facile method to produce materials for the high-working-efficiency anodes of Li-ion batteries. A series of characterization assessments (e.g., X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron microscopy) were conducted, and the results confirmed the efficacious partial replacement of Fe ions with Mn ions in the NdFeO3 perovskite structure, occurrence of both amorphous and crystalline structures, presence of oxygen vacancies (VO), and interconnection between nanoparticles. The possibility of Mn ion replacement significantly affects the size, amount of VO, and ratio of amorphous phase in NdMnxFe1-xO3 perovskites. The NdMnxFe1-xO3 perovskite with x = 0.3 presents a notable electrochemical performance, including low charge transfer resistance, durable Coulombic efficiency, first-rate capacity reservation, high pseudo-behavior, and elongated 150-cycle service life, whereas no discernible capacity deterioration is observed. The reversible capacity of the anode after the 150th-cylcle was 713 mAh g-1, which represents a high-capacity value. The outstanding electrochemical efficiency resulted from the optimum presence of VO, interconnection between the nanoparticles, and distinctive properties of the NdFeO3 perovskite. The interconnection between nanoparticles was advantageous for forming a large electrolyte-electrode contact area, improving Li-ion diffusion rates, and enhancing pseudocapacitive effect. The attributes of perovskite crystals, coexistence of Mn and Fe throughout the charge/discharge process, and optimum VO precluded the electrode devastation that caused the Li2O-phase decomposition catalysis, enabling favorable reversible Li storage.

Composition Optimization and Microstructure Design in MOFs-Derived Magnetic Carbon-Based Microwave Absorbers: A Review

Magnetic carbon-based composites are the most attractive candidates for electromagnetic (EM) absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magnetic branches. Metal-organic frameworks (MOFs) have demonstrated their great potential as sacrificing precursors of magnetic metals/carbon composites, because they provide a good platform to achieve high dispersion of magnetic nanoparticles in carbon matrix. Nevertheless, the chemical composition and microstructure of these composites are always highly dependent on their precursors and cannot promise an optimal EM state favorable for EM absorption, which more or less discount the superiority of MOFs-derived strategy. It is hence of great importance to develop some accompanied methods that can regulate EM properties of MOFs-derived magnetic carbon-based composites effectively. This review comprehensively introduces recent advancements on EM absorption enhancement in MOFs-derived magnetic carbon-based composites and some available strategies therein. In addition, some challenges and prospects are also proposed to indicate the pending issues on performance breakthrough and mechanism exploration in the related field.

Progress in Iron Oxides Based Nanostructures for Applications in Energy Storage

The demand for green and efficient energy storage devices in daily life is constantly rising, which is caused by the global environment and energy problems. Lithium-ion batteries (LIBs), an important kind of energy storage devices, are attracting much attention. Graphite is used as LIBs anode, however, its theoretical capacity is low, so it is necessary to develop LIBs anode with higher capacity. Application strategies and research progresses of novel iron oxides and their composites as LIBs anode in recent years are summarized in this review. Herein we enumerate several typical synthesis methods to obtain a variety of iron oxides based nanostructures, such as gas phase deposition, co-precipitation, electrochemical method, etc. For characterization of the iron oxides based nanostructures, especially the in-situ X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy are elaborated. Furthermore, the electrochemical applications of iron oxides based nanostructures and their composites are discussed and summarized.

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A novel spring-structured coaxial hierarchical SiO2@Co3O4 nanowire as a lithium-ion battery anode and its in situ real-time lithiation

High capacity and stable anodes are demanded since the current graphite-based anode does not meet the high-performance requirements of emerging Li-ion battery systems. Herein, we present a novel spring-shaped hierarchical SiO₂@Co₃O₄ nanowire composite, which exhibits good Li-storage performance. The special structure is able to effectively accommodate the change in structure during charge-discharge, and the coaxial hierarchical morphology enables rapid Li⁺ ion and electron transfer. The spring-shaped SiO₂@Co₃O₄ anode exhibits a capacity of 770 mAh g^-1, along with a high Coulombic efficiency of 99.8% after 400 cycles. A stable rate performance even after three rounds of measurements is also achievable. In addition, the real-time lithiation of the SiO₂@Co₃O₄ composite is investigated through an in situ transmission electron microscopy technology, which demonstrates the stable structure of the spring-shaped SiO₂@Co₃O₄ composite during the rapid lithiation process.

3D Hollow Porous Spherical Architecture Packed by Iron-Borate Amorphous Nanoparticles as High-Performance Anode for Lithium-Ion Batteries

Three-dimensional hollow porous spherical architecture packed by iron-borate amorphous nanoparticles as an anode for lithium-ion batteries is first prepared through a simple method. The anode exhibits a high Coulombic efficiency and an ultralong cycle life under high rate, delivering outstanding reversible capacity of 1170 mAh g^-1 after 360 cycles at 100 mA g^-1 and 1160 mAh g^-1 after 750 cycles at 200 mA g^-1. The iron-borate anode has a prominent ultralong cycle life. The reversible capacity can still remain at about 600 mAh g^-1 even after 3500 cycles at 2000 mA g^-1, which maintains an outstanding capacity and delivers a much longer cycle life than that of the reported iron-based oxide anodes measured at same current density only within 1000 cycles. The hollow porous structure offers efficient electron-transport and Li⁺-diffusion paths and buffers the structural strains to alleviate excessive pulverization of the anode materials. Large specific surface area of the hollow porous structure increases the contact area between the anode and electrolyte, providing more reaction sites. More importantly, the amorphous characteristics of the iron-borate anode possess higher density of active sites and improved faster reaction kinetics. This work demonstrates that the hollow porous iron-borate particle anode allows mass production and is one of the most attractive anodes in energy-storage applications.

Energy storage materials derived from Prussian blue analogues

Prussian blue analogues (PBAs) with open frameworks have drawn much attention in energy storage fields due to their tridimensional ionic diffusion path, easy preparation, and low cost. This review summarizes the recent progress of using PBAs and their derivatives as energy storage materials in alkali ions, multi-valent ions, and metal-air batteries. The key factors to improve the electrochemical performance of PBAs as cathode materials in rechargeable batteries were firstly discussed. Several approaches for performance enhancement such as controlling the amounts of vacancies and coordinated water, optimizing morphologies, and depositing carbon coating are described in details. Then, we highlighted the significance of their diverse architectures and morphologies in anode materials for lithium/sodium ion batteries. Finally, the applications of Prussian blue derivatives as catalysts in metal-air batteries are also reviewed, providing insights into the origin of favorable morphologies and structures of catalyst for the optimal performance.

Nitrogen-Doped Yolk-Shell-Structured CoSe/C Dodecahedra for High-Performance Sodium Ion Batteries

In this work, nitrogen-doped, yolk-shell-structured CoSe/C mesoporous dodecahedra are successfully prepared by using cobalt-based metal-organic frameworks (ZIF-67) as sacrificial templates. The CoSe nanoparticles are in situ produced by reacting the cobalt species in the metal-organic frameworks with selenium (Se) powder, and the organic species are simultaneously converted into nitrogen-doped carbon material in an inert atmosphere at temperatures between 700 and 900 °C for 4 h. For the composite synthesized at 800 °C, the carbon framework has a relatively higher extent of graphitization, with high nitrogen content (17.65%). Furthermore, the CoSe nanoparticles, with a size of around 15 nm, are coherently confined in the mesoporous carbon framework. When evaluated as novel anode materials for sodium ion batteries, the CoSe/C composites exhibit high capacity and superior rate capability. The composite electrode delivers the specific capacities of 597.2 and 361.9 mA h g^-1 at 0.2 and 16 A g^-1, respectively.