Nanocomposites with constituent sizes of <50nm are considered as a promising approach to enhance the figure of merit of bulk thermoelectric materials. A simple route involving hydrothermal synthesis and hot pressing was used in this work to prepare Bi2Te3∕Sb2Te3 bulk nanocomposites. It is shown that the composites have a laminated structure composed of Bi2Te3 and Sb2Te3 nanolayers with the thickness varying alternately between 5 and 50nm. The transport measurements indicate that the nanoscale laminated structure improves the thermoelectric performance with the maximal dimensionless figure of merit of 1.47 for the nanocomposite hot pressed from Bi2Te3 and Sb2Te3 nanopowders.

Symmetric hierarchical PbTe superstructures, including hopper cubes, flower-like structures, and dendritic structures, have been successfully fabricated by a facile alkaline hydrothermal method. Field emission scanning electron microscopy and transmission electron microscopy observations show that the PbTe hierarchical structures can be controlled by changing reaction temperature, reaction time, concentration of NaOH, and the kind of surfactants. The formation mechanism was investigated on the basis of the time-dependent experiment and the shape evolution. It is proposed that the formation of PbTe hopper cubic structures is due to the Berg effect induced concentration fluctuation of reactant ions, and the instability of growing fronts of crystals leads to the hierarchical dendritic morphologies. NaOH plays a crucial role in the formation stage. The Fourier transform infrared spectrum analysis showed that the band gap value of the PbTe hierarchical microcrystals was about 0.29 eV.

We synthesize Au@Ag core/shell nanoparticles (NPs) using a Au NP assisted Tollens reaction. The as-synthesized NPs are used for the colorimetric cyanide sensing with a detection limit of 0.4 μM. The bimetallic NPs are immobilized into agarose gels as portable "test strips".

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