Al-doped zinc oxide nanocomposites with enhanced thermoelectric properties

ZnO is a promising high figure-of-merit (ZT) thermoelectric material for power harvesting from heat due to its high melting point, high electrical conductivity σ, and Seebeck coefficient α, but its practical use is limited by a high lattice thermal conductivity κ(L). Here, we report Al-containing ZnO nanocomposites with up to a factor of 20 lower κ(L) than non-nanostructured ZnO, while retaining bulklike α and σ. We show that enhanced phonon scattering promoted by Al-induced grain refinement and ZnAl(2)O(4) nanoprecipitates presages ultralow κ ～ 2 Wm( -1) K(-1) at 1000 K. The high α～ -300 μV K(-1) and high σ ～ 1-10(4) Ω(-1 )m(-1) result from an offsetting of the nanostructuring-induced mobility decrease by high, and nondegenerate, carrier concentrations obtained via excitation from shallow Al donor states. The resultant ZT ～ 0.44 at 1000 K is 50% higher than that for the best non-nanostructured counterpart material at the same temperature and holds promise for engineering advanced oxide-based high-ZT thermoelectrics for applications.     

Green synthesis of bi-component copper oxide composites and enhanced photocatalytic performance

A facile and green route was proposed for the synthesis of bi-component copper oxide composite without any templates and additives. The effects of D-(+)-glucose amount, reaction temperature, and reaction time on the morphology and constitution of the products were investigated by SEM, X-ray diffraction, and UV-vis DRS in detail. The results indicate that a series of Cu₂O–CuO bi-component copper oxide composites with various morphologies can be easily obtained. Structure characterisation and photocatalytic tests show that the bi-component Cu₂O–CuO composites exhibited better photodecolouration of methylene blue than those of the Cu₂O, CuO, and Cu–CuO compounds owing to the existence of the synergistic effect between the CuO and Cu₂O.     

One-pot synthesis of Mn-doped goethite composite for enhanced supercapacitor performance and charge storage mechanism

Journal of Materials Science: Materials in Electronics - A simplistic synthesis of Mn & Fe (manganese & iron)-based composites with high surface area for energy storage application...     

Facile synthesis of novel ZnO/RGO hybrid nanocomposites with enhanced catalytic performance for visible-light-driven photodegradation of metronidazole

This study reported the first-time fabrication of uniform ZnO nanoclusters through a facile carbon nanosphere template-assisted approach, where the synthesized ZnO products were further decorated with the prepared reduced graphene oxide (RGO) to form novel ZnO/RGO nanocomposites. The as-synthesized materials were well characterized with the aid of various techniques, before they were used as photocatalysts for the degradation of metronidazole in the aqueous environment. Accordingly, the photocatalytic activity of the ZnO nanoclusters could be enhanced by coupling with RGO, where a large improvement (approx. 32.4% increase compared with pure ZnO) in the visible-light-driven degradation of metronidazole was observed on the prepared ZnO/RGO hybrid nanocomposites. Such study may provide insight into the usage of the ZnO/RGO composite in addressing broader environmental issues. The synthetic route employed in this work might also be extended to a useful technique for the preparation of assemblies of other materials based on nanoscale templates via easily-manipulated solution methods.     

Ion conduction and redistribution at grain boundaries in oxide systems

The review provides a comprehensive overview on the major findings regarding ion redistribution at interfaces in oxide systems and its effects on the electrical transport properties. As far as interfaces are concerned, grain boundaries and hence polycrystalline materials are to the fore. Heterocontacts and hence composites are only considered if relevant for the general understanding. Selected examples refer to oxide ceramics but also to composites. As far as the fundamental properties are concerned, major emphasis is laid on the impact on ion conductivity. Purely electronic effects (e.g. interfaces in semiconductors, boundaries in superconductors, or the formation of two-dimensional electron gases at the interface between two insulators) as well as phenomena related with solid/fluid interfaces are not addressed.     

Facile aqueous synthesis and growth mechanism of CdTe nanorods

Single-crystal CdTe nanorods with diameters of 50-100?nm were synthesized under a surfactant-assisted hydrothermal condition. The experimental results indicated that with a temporal dependence the morphologies of CdTe nanocrystallites changed from nanoparticles to smooth surface nanorods. The crystal structure, morphology and optical properties of the products were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and fluorescence spectrophotometer. Furthermore, the formation mechanisms of the nanorods were investigated and discussed on the basis of the experimental results.     

Facile synthesis and enhanced photocatalytic activity of hierarchical porous ZnO microspheres

In this paper, hierarchical porous ZnO microspheres were successfully synthesized by calcining the microspheric zinc hydroxide carbonate (ZHC) precursor, which were the precipitate products of a hydrothermal reaction by zinc nitrate hexahydrate and urea in the presence of trisodium citrate. The as-prepared ZnO microspheres with diameters of 4-5 μm were assembled by numerous porous nanosheets which had the uniform thickness of about 10 nm. The photocatalytic activity of the ZnO microspheres was evaluated by photodegradation reaction of methylene blue (MB). The as-prepared ZnO microspheres exhibited a significantly enhanced photocatalytic activity than commercial ZnO and TiO₂. This was mainly attributed to the larger specific surface area and stability against aggregation.     

Facile synthesis of zinc hydroxide carbonate flowers on zinc oxide nanorods with attractive luminescent and optochemical performance

A simple synthesis route was designed to fabricate a functional composite, zinc hydroxide carbonate (ZHC) flowers on zinc oxide (ZnO) nanorods. The hydrolysis of hexamethylenetetramine (HMT) can generate various species which are slowly released and gradually change reaction modes in a Zn(NO(3))(2)/HMT solution. As a result, ZnO nanorods and ZHC flowers can be sequentially synthesized and connect very well under constant experimental conditions. The obtained composite has the advantages of both components and exhibits attractive properties. For instance, ZHC flowers on ZnO nanorods exhibit strong blue emission under the excitation of ultraviolet light, and dye-sensitized solar cells with the annealed composite as photoanode achieve much higher conversion efficiency than pure nanorod arrays.     

Rational design,two-step synthesis of Cu2GeS3 crystal with enhanced thermoelectric performance by Te alloying

Journal of Materials Science: Materials in Electronics - Currently, Cu2GeS3 has been obtained through solid-state reaction. However, the pure phase Cu2GeS3 synthesized still faces challenges due to...     

Superparamagnetic magnetite nanocrystals-graphene oxide nanocomposites: facile synthesis and their enhanced electric double-layer capacitor performance

Superparamagnetic magnetite nanocrystals-graphene oxide (FGO) nanocomposites were successfully synthesized through a simple yet versatile one-step solution-processed approach at ambient conditions. Magnetite (Fe3O4) nanocrystals (NCs) with a size of 10-50 nm were uniformly deposited on the surfaces of graphene oxide (GO) sheets, which were confirmed by transmission electron microscopy (TEM) and high-angle annular dark field scanning transmission election microscopy (HAADF-STEM) studies. FGO with different Fe3O4 loadings could be controlled by simply manipulating the initial weight ratio of the precursors. The M-H measurements suggested that the as-prepared FGO nanocomposites have a large saturation magnetizations that made them can move regularly under an external magnetic field. Significantly, FGO nanocomposites also exhibit enhanced electric double-layer capacitor (EDLC) activity compared with pure Fe3O4 NCs and GO in terms of specific capacitance and high-rate charge-discharge.     

Facile synthesis of magnetic iron oxide nanoparticles and their characterization

Magnetic iron oxide nanoparticles are synthesized by suitable modification of the standard synthetic procedure without use of inert atmosphere and at room temperature. The facile synthesis procedure can be easily scaled up and is of important from industrial point of view for the commercial large scale production of magnetic iron oxide nanoparticles. The synthesized nanoparticles were characterized by thermal, dynamic light scattering, scanning electron microscopy and transmission electron microscopy analyses.     

Facile synthesis and gas sensing properties of nanotriangular tin oxide

In the present study we report a simple and convenient chemical route using pentaerythritol as a structure-directing agent for the synthesis of crystalline nanotriangular SnO₂. We propose the scheme for the formation of nanotriangular structures wherein the preliminary spherical nanocrystallites are formed due to the low surface energy associated with them. These spherical nanocrystallites grow into the various linear intermediate shapes like Y, bi and tripods, which finally lead to the triangles, pyramids and bipyramids. Such variation in the structure occurs due to the structure directing pentaerythritol. These polycrystalline SnO₂ nanomaterials with structural peculiarities were tested for the gas sensing characteristics. Their response towards ethanol vapor, H₂ and LPG were investigated. It was found to exhibit high response towards ethanol vapors at the operating temperature of 250 °C.     

Erratum to:Facile fabrication of integrated three-dimensional CMoSe2/reduced graphene oxide composite with enhanced performance for sodium storage

Erratum to Nano Research 2016,9(6):1618-1629 https://doi.org/10.1007/s12274-016-1056-3.The authors regret that Fig.5(d)in page 1625 of the original paper needs to be corrected.The rate capability of C-MoSer electrode was unfortunately mistaken.The correct Fig.5(d)is shown below.The corresponding figure caption and conclusions are not affected and thus not to be changed.The authors would like to apologise for any inconvenience caused.     

Facile synthesis of magnesium oxide nanoplates via chemical precipitation

Magnesium oxide (MgO) nanoplates, which have a thickness of about 10–20 nm and a length of up to 100 nm, are synthesized via chemical precipitation using ammonia hydroxide as precipitator in the presence of a nonionic surfactant polyethylene glycol (PEG 400). The morphologies and structures of the synthesized nanoplates have been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Furthermore, the mechanism for the formation of the nanoplates has been preliminarily discussed. It is believed that the capping molecule of PEG 400, which inhibits crystal growth along the (001) direction due to its selective adsorption, plays a critical role in the formation of the plate-like nanostructures.     

Facile synthesis and thermoelectric studies of n-type bismuth telluride nanorods with cathodic stripping Te electrode

Bismuth telluride (Bi₂Te₃) nanorods (NRs) of n-type thermoelectric materials were prepared using an electrogenerated precursor of tellurium electrode in the presence of Bi³⁺ and mercapto protecting agent in aqueous solution under atmosphere condition. The optimal preparation conditions were obtained with ratio of Bi³⁺ to mercapto group and Te coulomb by photoluminescence spectra. The mechanism for generation of Bi₂Te₃ precursor was investigated via the cyclic voltammetry. The highly crystalline rhombohedral structure of as-prepared Bi₂Te₃ NRs with the shell of Bi₂S₃ was evaluated with high resolution transmission electron microscopy (HRTEM) and powder X-ray diffraction (XRD) spectroscopy. The near-infrared absorption of synthetic Bi₂Te₃ NRs was characterized with spectrophotometer to obtain information of electron at interband transition. The thermoelectric performance of Bi₂Te₃ NRs was assessed with the result of electrical resistivity, Seebeck coefficient, thermal conductivity, and the figure of merit ZT parameters, indicating that thermoelectric performance of as-prepared Bi₂Te₃ nanocrystals was improved by reducing thermal conductivity while maintaining the power factor.     

Facile synthesis of polymer-enveloped ultrasmall superparamagnetic iron oxide for magnetic resonance imaging

Ultrasmall superparamagnetic iron oxide (USPIO) with synthetic polymer, based on magnetite core, was synthesized via facile photochemical in situ polymerization. A possible mechanism of photochemical in situ polymerization was proposed. The obtained polymer-enveloped UPSIO was characterized by transmission electron microscopy (TEM), photo-correlation spectroscopy (PCS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG) analysis and vibrating sampling magnetometer (VSM) measurement. Properties such as ultrasmall particle size, hydrophilicity, strong magnetization and surface characteristics, which are desirable for magnetic resonance imaging (MRI) contrast agents, were evaluated in detail. The resultant USPIO-based MRI contrast agent holds considerable promise in molecular MR tracking, MR immune imaging, cell tracking and targeted intracellular hyperthermia, etc.     

Indium oxide nanocrystals: Capping-agent-free synthesis,size-control mechanism,and high gas-sensing performance

Indium oxide nanocrystals with size of 8–20 nm have been synthesized by annealing the precursor particles at ambient pressure. No surfactants or capping agents were used in the synthesis. Depending on the ripening time of the precursor particles in their mother solution, rough control of the crystal size of the annealed indium oxide was achieved. It is interesting that the size of the annealed indium oxide crystals decreases with prolonging the ripening time of the precursor particles, which is the opposite as expected. We proposed a possible mechanism, that is the pre-disintegrating of the precursor particles happened during the ripening process, to explain the rough control of the crystal size. Promoted by attributes of the crystals such as small size, free of surfactant, and abundant defects, we fabricated indium oxide gas sensors and found that these sensors had good response to NO₂ gas and can achieve a detection limit as low as 20 ppb.