Latest ArticlesNanobubble is a rising research field, which attracts more and more attentions due to its potential applications in medical science, catalysis, electrochemistry and etc. To better implement these applications, it is urgent to understand one of the most important mechanisms of nanobubbles, the evolution. However, few attentions have been paid in this aspect because of the methodology difficulties. Here we successfully used dark-field microscopy to study the evolution process of single nanobubbles generated from formic acid dehydrogenation on single Pd-Ag nanoplates. We found some of the nanobubbles in this system can exhibit three distinct states representing different sizes, which can transform among each other. These transitions are not direct but through some intermediate states. Further kinetic analysis reveals complicated mechanisms behind the evolution of single nanobubbles. The results acquired from this study can be applicable to nanobubble systems in general and provide insights into the understanding of mechanisms affecting the stability of nanobubbles and their applications.
Conductive MOFs could exhibit full potential as integrated electrode materials for supercapacitors without interference from additional conductive additives. Here we report an anionic Co-MOF cage with zeolite framework, which was balanced by the redox-active guest [Co(H2O)6]2+ and protonated [(CH3)2NH2]2+ ions. Benefit from the unique ion skeleton structure, Co-MOF exhibits a conductivity higher than most of reported MOFs with the value of 1.42×10-3 S/cm, which can be directly fabricated as electrode for supercapacitors. A maximum specific capacitance of 236.2 F/g can be achieved at a current density of 1 A/g of Co-MOF. Additionally, the electric performance and morphology of this Co-MOF can be modified by cetyltrimethylammonium bromide (CTAB) and the maximum specific capacitance could increase up to 334 F/g at 1 A/g when the ratio of ligand and CTAB is 1:6 (Co-MOF-6). Furthermore, the specific capacitance can retain at 64.04% and 77.92% of the initial value after 3000 cycles of Co-MOF and Co-CTAB-6, respectively. Obviously, the addition of CTAB further improves both capacitance and cycle stability.
Metallic phosphides as a crucial class of metal-like compounds show high electric conductivity and electrochemical properties. It is of significant benefit to understanding the relationship between the electrocatalytic performance and phosphating degree of precursors. In this work, using Co3O4@SiO2 as precursor, core-shell structured CoP@SiO2 nanoreactors with outstanding oxygen evolution reaction performance were synthesized through a facile calcination method. The electrocatalytic performance of CoP@SiO2 modified electrode that treated with 500 mg NaH2PO2 was greatly enhanced. The obtained product displays a low overpotential of 280 mV at a current density of 10 mA/cm2 and a Tafel value 89 mV/dec in alkaline conditions. The easy available CoP@SiO2 with outstanding catalytic performance and stability possesses huge potential in future electrochemical applications.
Supercapacitors with good electrochemical performance and flexibility are in great demand. In this paper, the concept of preparing 3D porous carbon monoliths via direct calcination of melamine sponge is presented. This preparation method is simple and has good control of the structure. Porous carbon composite nickel-manganese oxides can be obtained by hydrothermal method followed with calcination. The electrochemical performances were tested and porous carbon monoliths with NiMn oxides exhibited a specific capacitance of 870 F/g in 1 mol/L KOH at a charge/discharge current density of 0.5 A/g and a capacity retention of 89.9% after 5000 times charge and discharge.
MXene materials have recently attracted considerable attention in energy storage application owing to their metallic conductivity, 2D structure and tunable surface terminations. However, the restacking of 2D MXene nanosheets hinders the ion transport and accessibility to the surface, resulting in adverse effect on their electrochemical performances. Here, with the assistance of hexamethylenetetramine (C6H12N4), 2D Ti3C2Tx MXene nanosheets were fabricated into a 3D architecture with crumbled and porous structure through an electrostatic self-assembly followed by annealing. The resultant 3D structure can expose massive active sites and facilitates the ion transport, which is beneficial for sufficient utilization of the outstanding superiorities of the MXene. Therefore, as a pseudocapacitive material, the 3D crumpled and porous Ti3C2Tx MXene shows a gravimetric capacitance of 333 F/g at 1 A/g, and maintains 261 F/g and 132 F/g at ultrahigh current densities of 100 A/g and 1000 A/g, respectively, revealing promising potential for application in supercapacitors.
Aqueous rechargeable zinc-ion batteries (ARZIBs) are expected to replace organic electrolyte batteries owing to its low price, safe and environmentally friendly characteristics. Herein, we fabricated vanadium-based Na1.25V3O8 nanosheets as a cathode material for ARZIBs, which present a high performance by electrochemical de-sodium at high voltage to form Na2V6O16 phase in the first cycle: high capacity of 390 mAh/g at 0.1 A/g, high rate performance (162 mAh/g at 10 A/g) and superior cycle stability (179 mAh/g with a high capacity retention of 88.2% of the maximum capacity after 2000 cycles). In addition, the cell exhibits a high energy density of 416.9 Wh/kg at 143.6 W/kg, suggesting great potential of the as-prepared Na1.25V3O8 nanosheets for ARZIBs.
Constructing heterostructures by combining COFs and TMD is a new strategy to design efficient photocatalysts for CO2 reduction reaction (CO2RR) due to their good stability, tunable band gaps and efficient charge separation. Based on the synthesis of completely novel C4N-COF in our previous reported work, a new C4N/MoS2 heterostructure was constructed and then the related structural, electronic and optical properties were also studied using first principle calculations. The interlayer coupling effect and charge transfer between the C4N and MoS2 layer are systematically illuminated. The reduced band gap of the C4N/MoS2 heterostructure is beneficial to absorb more visible light. For the formation of type-Ⅱ band alignment, a built-in electric field appears which separates the photogenerated electrons and holes into different layers efficiently and produces redox active sites. The band alignment of the heterostructure ensures its photocatalytic activities of the whole CO2 reduction reaction. Furthermore, the charge density difference and charge carrier mobility confirm the existence of the built-in electric field at the interface of the C4N/MoS2 heterostructure directly. Finally, the high optical absorption indicates it is an efficient visible light harvesting photocatalyst. Therefore, this work could provide strong insights into the internal mechanism and high photocatalytic activity of the C4N/MoS2 heterostructure and offer guiding of designing and synthesizing COF/TMD heterostructure photocatalysts.
Furazan and furoxan represent fascinating explosophoric units with intriguing structures and unique properties. Compared with other nitrogen-rich heterocycles, most poly furazan and furoxan-based heterocycles demonstrate superior energetic performances due to the higher enthalpy of formation and density levels. A large variety of advanced energetic materials have been achieved based on the combination of furazan and furoxan moieties with different kinds of linkers and this review provides an overview of the development of energetic poly furazan and furoxan structures during the past decades, with their physical properties and detonation characteristics summarized and compared with traditional energetic materials. Various synthetic strategies towards these compact energetic structures are highlighted by covering the most important cyclization methods for construction of the hetercyclic scaffolds and the following modifications such as nitrations and oxidations. Given the synthetic availabilities and outstanding properties, energetic materials based on poly furazan and furoxan structures are undoubtedly listed as a promising candidate for the development of new-generation explosives, propellants and pyrotechnics.
D-peptides are recognized as a new class of synthetic chemical drugs and they possess many interesting advantages such as high enzymatic stability, improved oral bioavailability, as well as high binding affinity and specificity. Recently, D-peptide drugs have been attracting increasing attention in both academic and industrial researches over recent years. One D-peptide etelcalcetide has even entered the market that targets the calcium (Ca2+)-sensing receptor (CaSR) to fight secondary hyperparathyroidism. Effective discovery and optimization of D-peptide ligands that can bind to various disease-related targets with high specificity and potency is of great importance for the development of D-peptide drugs. This review surveys the recent method development in this area especially the chemical protein synthesis-assisted high-throughput screening strategies for D-peptide ligands and their application in drug discovery.
Facile achievement of gold nanorods (AuNRs) with controllable longitudinal surface plasmon resonance (LSPR) is of great importance for their applications in various fields. The LSPR of AuNRs is sensitive to their aspect ratio, which is still hard to be precisely tuned by direct synthesis. In this work, we report a simple approach for end-selective etching of AuNRs by a rapid oxidation process with Au(Ⅲ) in cetyltrimethylammonium bromide (CTAB) solution at a mild temperature. The LSPR wavelength and the length of AuNRs blue shifted linearly as a function of the amount of Au(Ⅲ), while the diameter of AuNRs remained nearly constant. The oxidative rate is temperature dependent, and the oxidative process for a desired LSPR can be accomplished within 15 min at 60 ℃. Further investigations indicated that Br- determine the occurrence of the oxidation between AuNRs and Au(Ⅲ), and a small amount of surfactant chain (CTA+) is crucial for stabilizing AuNRs. This method presents a quick but robust strategy for acquiring AuNRs with an arbitrary intermediate LSPR wavelength using the same starting AuNRs, and can be a powerful tool for subsequent applications.
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