Graphene, because of its excellent mechanical, electrical, chemical, physical properties, sparked great interest to develop and extend its applications. Particularly, graphene based field-effect transistors (GFETs) present exciting and bright prospects for sensing applications due to their greatly higher sensitivity and stronger selectivity. This Review highlights a selection of important topics pertinent to GFETs and their application in electronic sensors. This article begins with a description of the fabrications and characterizations of GFETs, and then introduces the new developments in physical, chemical, and biological electronic detection using GFETs. Finally, several perspective and current challenges of GFETs development are presented, and some proposals are suggested for further development and exploration.
In this work, a facile hydrothermal approach for the shape-controlled synthesis of NiCo2S4 architectures is reported. Four different morphologies, urchin-, tube-, flower-, and cubic-like NiCo2S4 microstructures, have been successfully synthesized by employing various solvents. The obtained precursors and products have been characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. It is revealed that the supersaturation of nucleation and crystal growth is determined by the solvent polarity and solubility, which can precisely control the morphology of NiCo2S4 microstructures. The detailed electrochemical performances of the various NiCo2S4 microstructures are investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The results indicate that the tube-like NiCo2S4 exhibits promising capacitive properties with high capacitance and excellent retention. Its specific capacitance can reach 1048 F g(-1) at the current density of 3.0 A g(-1) and 75.9% of its initial capacitance is maintained at the current density of 10.0 A g(-1) after 5000 charge-discharge cycles.
Using a simple hydrothermal route coupled with a carbonization treatment, one-dimensional NiCo 2 S 4 @MnO 2 heterostructures have been fabricated successfully.Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) measurements showed that MnO 2 nanoflakes uniformly wrapped on the surface of NiCo 2 S 4 nanotube and formed core-shell heterostructured nanotubes, which combine both advantages of NiCo 2 S 4 such as excellent cycle stability and MnO 2 with high capacity. Serving as supercapacitor electrode, the NiCo 2 S 4 @MnO 2 heterostructures give a remarkable specific capacitance (1337.8 F/g at the current density of 2.0 A/g) and excellent cycling stability (remaining 82% after 2000 cycles) due to their synergistic effects of NiCo 2 S 4 and MnO 2 . Such unique nanoarchitectures demonstrate potential applications in energy storage electrodes and inspire researchers continue to focus on heterostructured materials.
Hierarchical mesoporous spinel NiCo₂O₄ was synthesized by a facile hydrothermal method assisted by polyvinylpyrrolidone (PVP) and a post annealing treatment. The synthesized hierarchical mesoporous NiCo₂O₄ presents a hierarchical mesoporous structure with diameters of 5.0 and 25 nm, respectively. Compared to conventional flower-like NiCo₂O₄, the hierarchical mesoporous structured NiCo₂O₄ exhibits excellent supercapacitor performance. The specific capacitance can reach 1619.1 F g(-1) at a current density of 2.0 A g(-1). When the current density is increased to 10.0 A g(-1), a specific capacitance of 571.4 F g(-1) can be obtained. Furthermore, the hierarchical mesoporous structured NiCo₂O₄ presents excellent stability. The outstanding electrochemical performance of the hierarchical mesoporous NiCo₂O₄ reveals its potential to be a promising material for use in supercapacitors, and also inspires continued research on binary metal oxides as energy transformation materials.
A NiCo2O4/NiO-HD nanocage is synthesized using MOF as a precursor and self-sacrificing template. A lithium-ion battery anode based this novel nanomaterial exhibits outstanding capacity, cycling stability and rate performance.
Despite the fascinating Li storage properties of organic carbonyl compounds, e.g., high therotical capacity and fast kinetics, it is still lack of a facile and effective way that capable of large‐scale producion of advanced carbonyl cathodes for Li‐ion batteries (LIBs). Here, a generic strategy is proposed by combining sonication and hydrothermal techniques for scalable synthesis of high performance organic carbonyl cathodes for LIBs. A series of commercialized vat dyes with abundant electroactive conjugated carbonyl groups are confined in between the graphene layers, forming a compatible 3D hybrid architecture. The unique structure affords good Li+ ions accessibility to the electrode and short Li+ ions diffusion length. Meanwhile, each sandwiched graphene layer functions as a miniature current collector, ensuring fast electron transport throughout the entire electrode. Consequently, the cathodic performances of LIBs using the composites as electrodes, for example, Vat Green 8/graphene, Vat Brown BR/graphene, and Vat Olive T/graphene, possess high specific capacity, exceptional cycling stability, and excellent rate capability. The effect of vat dye content on the morphology, structure, and the final electrochemical performance of the composites is investigated as well. This work provides a versatile and low‐cost platform for large‐scale development of advanced organic‐based electrodes toward sustainable energy fields.
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