We herein report the large-scale synthesis of Bi 2 Te 32x Se x (0.6 ¡ x ¡ 0.75) nanoplatelets through a hydrothermal method and subsequent spark plasma sintering. The effect of selenium alloying and the spark plasma sintering temperature on the thermoelectric properties of the Bi 2 Te 3 nanostructured bulk materials were investigated. The results indicate that compared to samples fabricated in an autoclave, preparing Bi 2 Te 32x Se x in glass beaker with suitable Se alloying and appropriate sintered temperature is an efficient way to reduce the lattice thermal conductivity due to a large number of Bi 2 TeO 5 nanodots with sizes of around 10 nm. Meanwhile, a decrease in electrical resistivity due to increase in carrier mobility and an enhancement of the Seebeck coefficient attribute to decrease in carrier concentration were observed. As a result, the thermoelectric figure-of-merit, ZT, is significantly improved and the maximum value reaches 0.96 for Bi 2 Te 2.25 Se 0.75 at 490 K.

Bi2Te3-based thermoelectric materials with large thermoelectric figure of merit, ZT, at elevated temperatures are advantageous in power generation by using the low-grade waste heat. Here, we show that incorporation of small proportion (0.3 vol. %) of nanophase Cu2Se into BiSbTe matrix causes an enhanced high-temperature thermopower due to elevated energy filtering of carriers and inhibition of minority transport besides enhanced phonon blocking from scattering at interfaces, which concurrently result in an ∼20% increase in the power factor and an ∼60% reduction in the lattice thermal conductivity at 488 K. As a result, ZT = 1.6 is achieved at 488 K in the composite system with 0.3 vol. % of Cu2Se. Significantly, its ZT is larger than unit in broad high-temperature range (e.g., ZT = 1.3 at 400 K and ZT = 1.6 at 488 K), which makes this material to be attractive for applications in energy harvesting from the low-grade waste heat.

Few-photon induced ultrafast dynamics in acetylene (C2H2) leading to several dissociation channels—deprotonation (H++C2H+ and H++C2H2+), symmetric break-up (CH++CH+) and isomerization (C++CH2+)-–were investigated employing the (XUV; extreme ultra-violet)-pump–(XUV; extreme ultra-violet)-probe scheme at the free-electron laser in Hamburg, combined with multi-hit coincidence detection. The kinetic energy releases and fragment-ion momentum distributions for various decay channels are presented. The C++CH2+ and H++C2H2+ channels reveal clear signatures of ultrafast molecular mechanisms, demonstrating potential applications of our pump-probe technique to complex systems in order to study a large variety of ultrafast phenomena in the XUV regime.