Novel Self-Assembled MgO Nanosheet and Its Precursors

A novel self-assembled microstructure, nestlike Mg5(CO3)4(OH)2·4H2O spheres, is formed by a self-assembly of nanosheets in the hydrothermal process. MgO with the similar morphology can be obtained by calcination of nestlike Mg5(CO3)4(OH)2·4H2O. MgO precursors with a uniform, ellipsoid-shaped, and smooth surface or flowerlike architecture, built by individual thin sheets, can be well-obtained by carefully controlling pH values of the initial reaction solution. The nestlike MgO exhibits a unique geometrical shape; its surface is composed of uniform MgO nanosheets. The unique MgO microstructure with high surface areas may possess promising applications as the sorbent for chemisorption and destructive adsorption of various pollutants

A Modified Electroless Deposition Route to Dendritic Cu Metal Nanostructures

Metal Cu nanomaterials are highly desirable for being used in many applications and most widely used in electrical conductivity much more than silver and gold because of its low price and stability at high frequencies. In this paper, a modified electroless deposition strategy has been discovered for the first synthesis of novel Cu dendritic nanostructures. We have adopted the diffusion-limited growth and oriented attachment mechanism, which take effect equally during the nucleation and growth process, to account for the formation mechanism of the unique Cu dendritic nanostructures. The obtained Cu dendritic nanostructures can bring wide applications in optics, gas sensors, catalysts, information storage, and other related fields and sheds new insights to understand the formation process of fractal dendritic structures in the natural and synthetic world. Most importantly, the method reported in this work provides a new principle for the designing synthesis of dendritic metal nanomaterials and can be regarded as a general way to fabricate other nanomaterials

General, Spontaneous Ion Replacement Reaction for the Synthesis of Micro- and Nanostructured Metal Oxides

A novel spontaneous ion replacement route based on the solubility difference as the driving force to synthesize a number of metal oxides has been established. We present a comprehensive study on the ion replacement reaction for chemical synthesis of micro- and nanostructured Mn2O3, ZnO, CuO, CdO, Al2O3, and CaO samples. This novel approach described herein is derived from the solubility difference between two carbonate salts, in which a metal cation can be driven from one liquid phase into another solid phase in the solution system. The resulting metal carbonate salts are initially formed and subsequently calcined to form highly crystallined metal oxides. The variation of pH values, reaction temperature, and reagent shapes can vary the solubility of these two carbonate salts, which thus changes the final morphology of metal oxides. The present work makes a progress to simply and mildly synthesize metal oxides with various morphologies, due to the fact that materials with a desired morphology are a key engineering step toward their shape-dependent chemical and physical properties

Room Temperature Fabrication of Hollow ZnS and ZnO Architectures by a Sacrificial Template Route

Hollow ZnS and ZnO architectures are fabricated by employing Zn5(CO3)2(OH)6 microspheres as the sacrificial template. Zn5(CO3)2(OH)6 microspheres can be effectively converted into the core/shell structured ZnO/ZnS composites (in the Na2S solution) and hollow ZnO architectures (in the KOH solution), by a spontaneous ion replacement reaction at room temperature. Removing the core by the KOH treatment of core/shell structured ZnO/ZnS, hollow ZnS spheres with different shell thicknesses can be effectively achieved. The obtained hollow ZnO architectures exhibit unique geometrical shapes, and their walls are composed of nanocrystals, which are connected to each other to form their hemispherical or circular shape. A possible formation process from Zn5(CO3)2(OH)6 microspheres to core/shell structured ZnO/ZnS composites is proposed by arresting a series of intermediate morphologies

Morphosynthesis of Hierarchical Hydrozincite with Tunable Surface Architectures and Hollow Zinc Oxide

Hydrozincite (Zn5(CO3)2(OH)6) microspheres with a tunable surface architecture have been successfully synthesized via a homogeneous precipitation method under solvothermal conditions. For a smooth hydrozincite microsphere, various building blocks such as nanocubes, nanorods, and nanosheets are arranged to cover a spherical surface by concisely controlling reaction time and the volume of ethylene glycol. Hexagonal Zn5(CO3)2(OH)6 with nanostep structures are also prepared without any additives. The hollow ZnO microspheres with a porous surface have been successfully fabricated via a solution-based method by the room-temperature treatment of filled Zn5(CO3)2(OH)6 microspheres composed of nanocubes. A possible growth mechanism of these hollow ZnO microspheres is proposed. The similar filled ZnO microspheres can also be obtained by a direct pyrolysis of Zn5(CO3)2(OH)6 microspheres composed of nanocubes at 450 °C

Conversion of ZnO Nanorod Arrays into ZnO/ZnS Nanocable and ZnS Nanotube Arrays via an in Situ Chemistry Strategy

Vertically aligned ZnO nanorods with uniform diameter and length have been synthesized on a zinc foil substrate with ammonium persulfate as oxidant via a facile, larger scale production and inexpensively synthesized method without any templates or additives. SEM and XRD studies indicate that ZnO nanorods are well-oriented along the c-axis. The PL spectrum indicates that our as-synthesized ZnO nanorods with a stronger and wider green emission are promising candidates as electron nanoconductors in nano-optoelectronic devices. Furthermore, by an effective thioglycolic acid-assisted solution route, well-aligned ZnO/ZnS nanocable and ZnS nanotube arrays have been successfully synthesized. ZnS nanotubes show a perfect hexagonal and obvious tubular shape. Our present strategy shows mild growth conditions and good reproducibility

An Efficient Bifunctional Electrocatalyst for a Zinc–Air Battery Derived from Fe/N/C and Bimetallic Metal–Organic Framework Composites

Efficient bifunctional electrocatalysts with desirable oxygen activities are closely related to practical applications of renewable energy systems including metal–air batteries, fuel cells, and water splitting. Here a composite material derived from a combination of bimetallic zeolitic imidazolate frameworks (denoted as BMZIFs) and Fe/N/C framework was reported as an efficient bifunctional catalyst. Although BMZIF or Fe/N/C alone exhibits undesirable oxygen reaction activity, a combination of these materials shows unprecedented ORR (half-wave potential of 0.85 V as well as comparatively superior OER activities (potential@10 mA cm^–2 of 1.64 V), outperforming not only a commercial Pt/C electrocatalyst but also most reported bifunctional electrocatalysts. We then tested its practical application in Zn–air batteries. The primary batteries exhibit a high peak power density of 235 mW cm^–2, and the batteries are able to be operated smoothly for 100 cycles at a curent density of 10 mA cm^–2. The unprecedented catalytic activity can be attritued to chemical coupling effects between Fe/N/C and BMZIF and will aid the development of highly active electrocatalysts and applications for electrochemical energy devices

Near-IR Photoresponse in New Up-Converting CdSe/NaYF₄:Yb,Er Nanoheterostructures

Near-IR Photoresponse in New Up-Converting CdSe/NaYF4:Yb,Er Nanoheterostructure

Single-Atom Iron as Lithiophilic Site To Minimize Lithium Nucleation Overpotential for Stable Lithium Metal Full Battery

High lithium nucleation overpotential on a lithiophobic matrix results in uncontrollable growth of lithium dendrites and thus restricts the wide application of lithium-metal batteries. Herein, the single-atom iron in a N-doped carbon matrix (FeSA-N-C) is first reported as a lithiophilic site to minimize Li nucleation overpotential from 18.6 mV to a very low value of 0.8 mV. Molecular dynamics simulations quantitatively confirmed the excellent affinity between Li ions and FeSA-N-C in the atomic level. Induced by the homogeneously distributed FeSA-N in the carbon substrate, uniform and stable metallic Li plating/stripping behaviors are realized and lithium dendrite growth is greatly suppressed. The proposed strategy of using single-atom iron as a lithiophilic site to minimize lithium nucleation overpotential opens a promising avenue for solving intrinsic problems of Li-metal-based batteries