Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries

Zinc oxide can be called a multifunctional material thanks to its unique physical and chemical properties. The first part of this paper presents the most important methods of preparation of ZnO divided into metallurgical and chemical methods. The mechanochemical process, controlled precipitation, sol-gel method, solvothermal and hydrothermal method, method using emulsion and microemulsion enviroment and other methods of obtaining zinc oxide were classified as chemical methods. In the next part of this review, the modification methods of ZnO were characterized. The modification with organic (carboxylic acid, silanes) and inroganic (metal oxides) compounds, and polymer matrices were mainly described. Finally, we present possible applications in various branches of industry: rubber, pharmaceutical, cosmetics, textile, electronic and electrotechnology, photocatalysis were introduced. This review provides useful information for specialist dealings with zinc oxide.

Zinc Oxide-From Synthesis to Application: A Review.

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

There is a growing interest in the conversion of water and solar energy into clean and renewable H2 fuels using earth-abundant materials due to the depletion of fossil fuel and its serious environmental impact. This critical review highlights some key factors influencing the efficiency of heterogeneous semiconductors for solar water splitting (i.e. improved charge separation and transfer, promoted optical absorption, optimized band gap position, lowered cost and toxicity, and enhanced stability and water splitting kinetics). Moreover, different engineering strategies, such as band structure engineering, micro/nano engineering, bionic engineering, co-catalyst engineering, surface/interface engineering of heterogeneous semiconductors are summarized and discussed thoroughly. The synergistic effects of the different engineering strategies, especially for the combination of co-catalyst loading and other strategies seem to be more promising for the development of highly efficient photocatalysts. A thorough understanding of electron and hole transfer thermodynamics and kinetics at the fundamental level is also important for elucidating the key efficiency-limiting step and designing highly efficient solar-to-fuel conversion systems. In this review, we provide not only a summary of the recent progress in the different engineering strategies of heterogeneous semiconductors for solar water splitting, but also some potential opportunities for designing and optimizing solar cells, photocatalysts for the reduction of CO2 and pollutant degradation, and electrocatalysts for water splitting.

Engineering heterogeneous semiconductors for solar water splitting

Ultrathin two-dimensional (2D) nanosheets of layered transition metal dichalcogenides (TMDs), such as MoS2, TiS2, TaS2, WS2, MoSe2, WSe2, etc., are emerging as a class of key materials in chemistry and electronics due to their intriguing chemical and electronic properties. The ability to prepare these TMD nanosheets in high yield and large scale via various methods has led to increasing studies on their hybridization with other materials to create novel functional composites, aiming to engineer their chemical, physical and electronic properties and thus achieve good performance for some specific applications. In this critical review, we will introduce the recent progress in hybrid nanoarchitectures based on 2D TMD nanosheets. Their synthetic strategies, properties and applications are systematically summarized and discussed, with emphasis on those new appealing structures, properties and functions. In addition, we will also give some perspectives on the challenges and opportunities in this promising research area.

Two-dimensional transition metal dichalcogenide nanosheet-based composites.

A novel composite consisting of graphene-like MoS₂ nanosheets and ultrasmall Fe₃O₄ nanoparticles (≈3.5 nm) is synthesized as an anode for lithium ion battery application. In such composite anode, MoS₂ nanosheets provide flexible substrates for the nanoparticle decoration, accommodating the volume changes of Fe₃O₄ during cycling process; while Fe₃O₄ nanoparticles primarily act as spacers to stabilize the composite structure, making the active surfaces of MoS₂ nanosheets accessible for electrolyte penetration during charge/discharge processes. Owing to the high reversible capacity provided by the MoS₂ nanosheets and the superior high rate performance offered by ultrasmall Fe₃O₄ nanoparticles, superior cyclic and rate performances are achieved by FeFe₃O₄/MoS₂ anode during the subsequent electrochemical tests, delivering 1033 and 224 mAh g⁻¹ at current densities of 2000 and 10,000 mA g⁻¹, respectively.

Ultrasmall Fe₃O₄ nanoparticle/MoS₂ nanosheet composites with superior performances for lithium ion batteries.

ZnO nanoparticles have been studied for potential cell labeling applications over the past several years. However, little progress has been made because of the limited emission color and poor water stability of ZnO nanoparticles. In this work, ZnO nanoparticles with various emission colors, including blue, green, yellow, and orange, were synthesized through an ethanol-based precipitation method. The emission color of the ZnO nanoparticles could be tuned by adjusting the pH value of the precipitation solution. The as-prepared ZnO nanoparticles were then encapsulated with silica to form ZnO@silica core shell nanoparticles, to improve the water stability of the ZnO nanoparticles. The visible emissions of the ZnO nanoparticles were well retained after they had been coated with silica shells. The resultant ZnO@silica core shell nanoparticles exhibited low cytotoxity and were promising in cell labeling applications.

Synthesis of ZnO Nanoparticles with Tunable Emission Colors and Their Cell Labeling Applications

AgInS2 nanocrystals have attracted intense attention due to their promising applications in printable solar cells, light-emitting diode (LED), and biological labeling. Although much effort has been made to develop various synthesis methods to prepare AgInS2 nanocrystals, it remains a goal to obtain high quality AgInS2 nanocrystals. In this work, Zn-doped AgInS2 nanocrystals were synthesized by diffusing Zn into the preformed AgInS2 seeds at high temperature in solution. The resulting Zn-doped AgInS2 nanocrystals had well-defined spherical morphology with narrow size distribution. By varying the reaction temperature, the emission wavelengths of the obtained Zn-doped AgInS2 nanocrystals could be adjusted from 520 to 680 nm. The quantum yield of the obtained alloyed nanocrystals could reach 41%, which was reasonably good as compared to those of the previously reported. The obtained Zn-doped AgInS2 nanocrystals showed promising applications in cell labeling.

Synthesis of Zn-Doped AgInS2 Nanocrystals and Their Fluorescence Properties

Gene transfer using self-assembled ternary complexes of cationic magnetic nanoparticles, plasmid DNA and cell-penetrating Tat peptide

We report the synthesis of a novel hollow porous Fe3O4 bead–rGO composite structure for lithium ion battery anode application via a facile solvothermal route. The formation of hollow porous Fe3O4 beads and reduction of graphene oxide (GO) into rGO were accomplished in one step by using ethylene glycol (EG) as a reducing agent. In this composite structure, the hollow porous Fe3O4 beads were either chemically attached or tightly wrapped with rGO sheets, leading to a strong synergistic effect between them. As a result, the obtained Fe3O4–rGO composite electrodes could deliver a reversible capacity of 1039 mA h g−1 after 170 cycles between 3 V and 50 mV at a current density of 100 mA g−1, with an increment of 30% compared to their initial reversible capacity, demonstrating their superior cycling stability.

Xiaosheng Tang

Papers

Ultrasmall Fe₃O₄ nanoparticle/MoS₂ nanosheet composites with superior performances for lithium ion batteries.

Synthesis of ZnO Nanoparticles with Tunable Emission Colors and Their Cell Labeling Applications

Synthesis of Zn-Doped AgInS2 Nanocrystals and Their Fluorescence Properties

Gene transfer using self-assembled ternary complexes of cationic magnetic nanoparticles, plasmid DNA and cell-penetrating Tat peptide

One-step synthesis of hollow porous Fe3O4 beads–reduced graphene oxide composites with superior battery performance