We report a solution-processed, ligand supported synthesis of 15-20 nm thick Sb (2−x) BixTe3 nanoplatelets. After complete ligand removal by a facile NH3-based etching procedure, the platelets are spark plasma sintered to a p-type nanostructured bulk material with preserved crystal grain sizes. Due to this nanostructure, the total thermal conductivity is reduced by 60 % in combination with a reduction in electric conductivity of as low as 20 % as compared to the bulk material demonstrating the feasibility of the phonon-glass electron-crystal concept. An enhancement in the dimensionless thermoelectric figure of merit of up to 15 % over state-of-the-art bulk materials is achieved meanwhile shifting the maximum to significantly higher temperatures.Recently, Bi 2 Te 3 based nanostructured materials have received great attention due to their outstanding thermoelectric properties. From the first reports in the 1950s until today, the dimensionless thermoelectric figure of merit (ZT) of such materials at room temperature has been improved threefold. ZT is estimated to require a value of 3 to be competitive with conventional cooling devices and to open up novel pathways for efficient and greener power generation.The record high efficiency of 2.4 was reported for molecular beam epitaxy engineered thin films of Bi 2 Te 3 /Sb 2 Te 3 layers, which may be difficult to use in large-scale applications but convincingly demonstrated the potential for further improvements to come from nanostructured Bi 2 Te 3 based materials [5].In order to fabricate such materials on a macroscopic scale, one conventionally applies high pressure and suitable temperatures to sinter a Bi 2 Te 3 based nanopowder to a dense nanocomposite with preserved crystal grain boundaries. Such nanocomposites have been studied by the means of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) [6] and scanning electron microscopy (SEM) [7]. It is believed that the unique structural details in these materials such as laminated structure, coherent interfaces, nanoprecipitates with defect concentrations and broad size distribution of crystalline domains effect all three parameters of ZT, namely the thermopower, electric and * Electronic address: scheele@chemie.uni-hamburg.de thermal conductivity and can lead to an overall improvement of thermoelectric efficiency.Synthetic strategies to Bi 2 Te 3 based nanopowders can be divided into two approaches: (a) ligandless or (b) ligand supported nanograin growth. Advantages of the former are the absence of organic impurities and the good alloying possibilities by standard semiconductor manipulations. As a matter of this, the ligandless approach was more successful recently and all of the mile stone achievements in enhancing zT as cited above were due this strategy. An instructive summary has been provided recently by Ren and coworkers [8]. However, it is found almost impossible to achieve a good size control and narrow size distribution of nanoparticles by this strategy. This is the major advan...

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A new low-power, compact microwave-induced plasma source for applications in atomic emission spectrometry at atmospheric pressure using microstrip technology is described. The gas channel of about 1 mm 2 is integrated in a fused silica dielectric wafer. The microstrip transmission lines are fabricated by sputtering and electro-plating. For example, a unit operates at an input power of 15 W with an argon gas flow of about 500 ml min −1 at atmospheric pressure. Rotational (OH) and excitation (Fe) temperatures of 650 K and 8000 K, respectively, were measured at these conditions. The emitted radiation can be taken up by an optical fibre positioned in the plasma-gas channel thus enabling an axial observation and coupling to a miniaturized spectrometer. The first devices showed an operation time of at least several hundred hours. Further investigations will lead to even smaller dimensions and lower power consumption and open the way for integrated microwave plasma sources with low detection limits as integrable parts of miniaturized total analytical systems applications.

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A new low-power, small-scale 2.45 GHz microwave plasma source at atmospheric pressure for atomic emission spectrometry based on microstrip technology is described. The MicroStrip Plasma (MSP) source was produced in microstrip technology on a fused-silica wafer and designed as an element-selective detector for miniaturized analytical applications. The electrodeless microwave-induced plasma (MIP) operates at microwave input power of 10-40 W and gas flows of 50-1000 mL.min-1 of Ar. Rotational (OH) and excitation (Fe) temperatures were found to be 650 and 8000 K, respectively. Spatially resolved measurements of the Hg I 253.7-nm atomic emission line with an electronic slitless spectrograph (ESS) showed that a cylindrically symmetric plasma with a diameter of about 1 mm is obtained. With the MSP, Hg could be determined by applying the flow injection cold vapor (FI-CV) technique with a detection limit of 50 pg.ml-1. In terms of the relative standard deviation, a time stability of < 1.4% for 45 replicates within 80 min can be realized at a concentration level of 10 ng.ml-1 of Hg. Hg could be determined in the leachate of a certified standard reference soil (STSD-4) obtained by treatment with aqua regia at the 930 +/- 76 ng.g-1 level. Results obtained by calibration with aqueous solutions of Hg and with standard addition were found to be in good agreement with those of cold-vapor atomic absorption spectrometry.