Increasing the amount of active sites and enhancing their intrinsic activity are two basic strategies for designing electrocatalytic materials. [3,18] Nanostructured electrocatalytic materials have been extensively studied because of their high specific surface area. [6,9,10] Amorphous materials have also been widely explored in the field of electrocatalysis because of their specific structure and property. [19][20][21][22][23] In comparison with crystal materials, amorphous materials have the following characteristics. First, amorphous materials have long-range disorder and short-range order intrinsic structural characteristics and possess rich defects and active sites. [19][20][21][22][23][24][25] Second, the chemical composition of amorphous materials can be regulated in a wide range, [26] thereby fine tuning the electronic structure of catalysts. Third, amorphous materials possess isotropic property and can provide homogenous active sites during chemical reaction, [27] thereby favoring the regulation of reactant selectivity. Lastly, amorphous materials are usually prepared under mild conditions, which are conducive to the large-scale application of these materials. [28] Metal-organic frameworks (MOFs) are novel coordination compound materials with periodic and porous structures in which metal cations act as a coordination center and organic molecules serve as ligands. [29][30][31][32][33][34][35][36][37][38] Various MOF-derived materials, such as metal oxides, metal sulfides, and metal/carbon composites, have been prepared by heat treatment, hydrothermal/solvothermal treatment, or other treatment approaches for an MOF precursor. [39][40][41][42][43][44][45] The composition, morphological characteristics, and structure of MOF-derived materials can be effectively regulated. [39,40] MOF-derived materials can maintain the structural diversity and porosity characteristics of MOFs and effectively improve their conductivity and stability. [39,40] The structure and chemical property of MOF-derived materials can be regulated by MOF precursor design and treatment control. [39,40] Therefore, MOF-derived materials have good application prospects in electrochemical energy storage, electrochemical energy conversion, and electrochemical sensors. [46][47][48][49] As a typical representative of zeolitic imidazolate framework MOF material, ZIF-67 has been extensively studied as a precursor for derivative preparation. [50] Moreover, ZIF-67 derivatives have received more and more attentions in the field of electrocatalysis. [51][52][53][54][55][56] In the present study, an amorphous intermediate derivative was prepared using a ZIF-67 hollow sphere (HS-ZIF-67) as a precursor via low-temperature heat treatment Increasing active sites is an effective method to enhance the catalytic activity of catalysts. Amorphous materials have attracted considerable attention in catalysis because of their abundant catalytic active sites. Herein, a series of derivatives is prepared via the low-temperature heat treatment of ZIF-67 hollow sphere at ...
HIGHLIGHTS • The electrochemical properties of M x Se y (M = Fe, Co, Ni) and their Composites have been discussed. • The synthetic methods and morphologies have been summarized. • The future directions and application prospect of M x Se y (M = Fe, Co, Ni) and their composites are given. ABSTRACT Transition-metal selenides (M x Se y , M = Fe, Co, Ni) and their composites exhibit good storage capacities for sodium and lithium ions and occupy a unique position in research on sodium-ion and lithium-ion batteries. M x Se y and their composites are used as active materials to improve catalytic activity. However, low electrical conductivity, poor cycle stability, and low rate performance severely limit their applications. This review provides a comprehensive introduction to and understanding of the current research progress of M x Se y and their composites. Moreover, this review proposes a broader research platform for these materials, including various bioelectrocatalytic performance tests, lithium-sulfur batteries, and fuel cells. The synthesis method and related mechanisms of M x Se y and their composites are reviewed, and the effects of material morphologies on their electrochemical performance are discussed. The advantages and disadvantages of M x Se y and their composites as well as possible strategies for improving the storage and conversion of electrochemical energy are also summarized.
Small‐molecule‐based second near‐infrared (NIR‐II) activatable fluorescent probes can potentially provide a high target‐to‐background ratio and deep tissue penetration. However, most of the reported NIR‐II activatable small‐molecule probes exhibit poor versatility owing to the lack of a general and stable optically tunable group. In this study, we designed NIRII‐HDs, a novel dye scaffold optimized for NIR‐II probe development. In particular, dye NIRII‐HD5 showed the best optical properties such as proper pKa value, excellent stability, and high NIR‐II brightness, which can be beneficial for in vivo imaging with high contrast. To demonstrate the applicability of the NIRII‐HD5 dye, we designed three target‐activatable NIR‐II probes for ROS, thiols, and enzymes. Using these novel probes, we not only realized reliable NIR‐II imaging of different diseases in mouse models but also evaluated the redox potential of liver tissue during a liver injury in vivo with high fidelity.
The glass carbon electrode modified by N-doped carbon quantum dots (NCQD) (NCQD/GCE) has been used to detect dopamine (DA) with broad linear range and low detection limit.
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