Convenient Controllable Synthesis of Inorganic 1D Nanocrystals and 3D High-Ordered Microtubes

A "concentration-induced self-assembly" strategy for Ag x H3-x PMo12O40 nanorods: synthesis, photoelectric properties and photocatalytic applications

Polyoxometalates (POMs) as molecule-based metal oxides have exhibited significant application in catalysis and materials science, but the synthesis of pristine POM nanomaterials still remains a challenge. In this work, we find a novel strategy of concentration-induced self-assembly for gaining pristine POM nanorods Ag _x H_3-x PMo₁₂O₄₀ (denoted as AgHPMo₁₂), which are synthesized only from both POMs and silver ion Ag⁺ in an aqueous solution at room temperature. The controllable concentrations of the cationic and anionic components in the aqueous solution become the critical factor for the successful synthesis. In addition, the photoelectric properties of AgHPMo₁₂ nanorods were investigated as compared to those of AgHPMo₁₂ particles, indicating a superior photoelectric performance of AgHPMo₁₂ nanorods to AgHPMo₁₂ particles. Furthermore, AgHPMo₁₂ nanorods/phthalocyanine heterojunction photocatalysts were prepared for evaluating photocatalytic degradation of tetracycline hydrochloride, showing an efficient photocatalytic performance due to the advantages of the nanorods and type II heterostructure.

Synthesis and spectroscopic properties of silver-fluorescein co-doped phosphotungstate hollow spheres

Herein, silver-fluorescein co-doped phosphotungstate hollow spheres have been successfully synthesized using a chemical precipitation method by introducing silver ions and fluorescein at room temperature. This hybrid nanomaterial possesses a uniform structure, exhibiting a strong emission spectrum with a peak centered at 517 nm. It is anticipated that silver and fluorescein as functionalized dopants for the phosphotungstate hollow sphere structure would provide this material with multiple properties. The control experiments indicate that fluorescein plays a key role in the formation of the hollow sphere structure. Hence, the co-doping strategy is proposed to be a general method to endow polyoxometalate nanomaterials with new structures, new functions and potential applications in bioimaging, fluorescent chemical sensors, and antibacterial or optoelectronic devices.

Self-supported tungsten/tungsten dioxide nanowires array as an efficient electrocatalyst in the hydrogen evolution reaction

A tungsten/tungsten dioxide nanowires array was constructed on a carbon paper through the thermal annealing of tungsten trioxide, and was proven to be an efficient hydrogen evolution cathode with strong durability in acidic solutions.

Blue emitting ZnO nanostructures grown through cellulose bio-templates

This paper presents a green and cost-effective recipe for the synthesis of blue-emitting ZnO nanoparticles (NPs) using cellulose bio-templates. Azadirachta indica (neem) leaf extract prepared in different solvents were used as biological templates to produce nanostructures of wurtzite ZnO with a particle size ~12-36 nm. A cellulose-driven capping mechanism is used to describe the morphology of ZnO NPs. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and photoluminescence (PL) studies showed that solvents affect the growth process and the capping mechanism of bio-template severely. Structural changes in ZnO NPs were evident with variation in pH, dielectric constants (DC) and boiling points (BP) of solvents. Furthermore, an energy band model is proposed to explain the origin of the blue emission in the as-obtained ZnO NPs. PL excitation studies and the theoretical enthalpy values of individual defects were used to establish the association between the interstitial-zinc-related defect levels and the blue emission. Copyright © 2015 John Wiley & Sons, Ltd.

Ultralong H2V3O8 nanowire bundles as a promising cathode for lithium batteries

In situ transport measurement of a single nanowire demonstrates that the H₂V₃O₈ nanowire possesses good electrical transport properties.

Morphogenesis of polyoxometalate cluster-based materials to microtubular network architectures

Pressed pellets of polyoxometalate (POM)-based materials are shown to undergo morphogenesis to produce microtubular network architectures without the need for a large single crystal precursor. The compression of the POM material into a pellet lowers the solubility sufficiently to allow tube initiation and growth from POMs that would otherwise be too soluble in their native crystalline state, thus yielding hollow, highly controllable, tubes of diameter 10-100 μm.

Sonocatalytic epoxidation of alkenes by vanadium-containing polyphosphomolybdate immobilized on multi-wall carbon nanotubes

A Keggin type polyoxometalate (POM) has been immobilized in the unique network structure of multi-wall carbon nanotubes (CNTs). The vanadium-containing polyphosphomolybdate (PVMo) supported on CNTs, which was prepared by a one-step solid-state reaction, was characterized by FT-IR, XRD, SEM and elemental analyses. These uniform nanoparticles have an average size 20-30nm. Furthermore, due to the chemical interaction between PVMo and carboxylic acid groups, PVMo nanoparticles were successfully immobilized on the CNTs. Moreover, the obtained composite was found as an efficient catalyst for oxidation of hydrocarbons under reflux and ultrasonic irradiation (US) conditions.

Facile and controllable synthesis of polyoxometalate nanorods within polyelectrolyte matrix

Well dispersed polyoxometalate nanorods have been selectively and controllably synthesized within the polyelectrolyte (PE) films via a layer-by-layer (LbL) adsorption-precipitation method. The PE matrix was fabricated by LbL self-assembly technology and then the multilayer films containing polyoxometalate nanorods were constructed by repetitive adsorption of polyanions and subsequent precipitation with counter ions-tetraethylammonium bromide (TEAB). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was used to observe the variation of size and morphology of the nanorods. The growth process and composition of the multilayer films containing nanorods were also studied.

Facile Hydrogen Evolution Reaction on WO3Nanorods

Tungsten trioxide nanorods have been generated by the thermal decomposition (450 °C) of tetrabutylammonium decatungstate. The synthesized tungsten trioxide (WO₃) nanorods have been characterized by XRD, Raman, SEM, TEM, HRTEM and cyclic voltammetry. High resolution transmission electron microscopy and X-ray diffraction analysis showed that the synthesized WO₃nanorods are crystalline in nature with monoclinic structure. The electrochemical experiments showed that they constitute a better electrocatalytic system for hydrogen evolution reaction in acid medium compared to their bulk counterpart.

Keggin POM Microtubes: a Coincident Product of Crystal Growth and Species Transformation

Microtubes of alpha-K4SiW12O40 with the length around 1 cm and inner diameter and wall thickness in the ranges of 7-55 mum and 3-15 mum, respectively, were copiously fabricated by a one-step, template-free aqueous synthesis. The formation mechanism is discussed. The discovered tubular structure of the polyoxometalate is believed to be promising for use in templates, as a precursor of tungsten oxide ceramic microtubes, and for other uses associated with tubular structures.

Synthesis and Evolution of PbS Nanocrystals through a Surfactant-Assisted Solvothermal Route

We present a surfactant-assisted solvothermal approach for the controllable synthesis of a PbS nanocrystal at low temperature (85 degrees C). Nanotubes (400 nm in length with an outer diameter of 30 nm), bundle-like long nanorods (about 5-15 mum long and an average diameter of 100 nm), nanowires (5-20 mum in length and with a diameter of 20-50 nm), short nanorods (100-300 nm in length and an axial ratio of 5-10), nanoparticles (25 nm in width with an aspect ratio of 2), and nanocubes (a short axis length of 10 nm and a long axis length of 15 nm) were successfully prepared and characterized by transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction pattern. A series of experimental results indicated that several experimental factors, such as AOT concentration, ratio of [water]/[surfactant], reaction time, and ratio of the reagents, play key roles in the final morphologies of PbS. Possible formation mechanisms of PbS nanorods and nanotubes were proposed.

Layer-by-Layer Assembly of Polyoxometalates into Microcapsules

The polyoxometalate (POM) chemistry world has been experiencing an unparalleled development of rapid synthesis of new compounds and slow development of POM-based functional materials and devices. Meanwhile, researchers in the microcapsule world, encouraged by the introduction of the layer-by-layer method, are pursuing good components for constructing functional capsule devices. Here, in view of the versatile properties that POM-based microcapsules may possess, various types of POM-polyelectrolyte composite microcapsules were constructed using the layer-by-layer method. Microscopy reveals that polyoxometalates form nanoparticles on the shell in the presence of cationic polyelectrolytes. These nanoparticles connected with polyelectrolytes constitute the shell and support the microcapsule from collapse after drying, and this is an interesting characteristic different from those of common composite and polyelectrolyte capsules. Fourier transform infrared (FTIR), UV-vis absorption, and X-ray photoelectron spectroscopy (XPS) were used to examine the properties of the POMs in the microcapsules. The obtained microcapsules exhibit higher thermal stability than polyelectrolyte microcapsules. Furthermore, the functions of POMs were maintained when they were assembled into microcapsules. It is proved that microcapsules bearing POMs with redox activity can provide a reduction environment, which can lead to the realization of in situ synthesis of materials, and that microcapsules with photoluminescent POMs as a component can also have a photoluminescent property, providing a way to develop functional capsule devices. This work may provide an opportunity to enrich both the polyoxometalate chemistry and the capsule field.

Controllable Fabrication of Carbon Nanotube and Nanobelt with a Polyoxometalate-Assisted Mild Hydrothermal Process

Carbon nanotubes, carbon nanobelts, and carbon nanoparticles can be prepared directly from active carbon powders by a polyoxometalates (POMs)-assisted mild hydrothermal process. After the hydrothermal reaction the POMs are changed into heteropoly blues, which can be converted into the POMs by a small amount of H2O2 solution.

A Simple and General Method for the Synthesis of Multicomponent Na2V6O16·3H2O Single-Crystal Nanobelts

Multicomponent Na2V6O16.3H2O (barnesite) single-crystalline nanobelts were synthesized by a direct reaction-crystallization growth of bulk V2O5 and NaF powders under hydrothermal treatment without using any templates or catalysts. This new strategy could be extended to prepare other one-dimensional multicomponent nanomaterials including ammonium, alkali-metal or alkali-earth metal vanadium oxide bronzes and other transition metal oxyfluorides. This is an efficient and mild solution method with clear advantages over the traditional high-temperature approach for the large-scale production of 1D multicomponent nanomaterials. The applicability of this approach toward the preparation of other inorganic systems, such as tungstates and molybdates, will be explored.