ABSTRACT
Identification of novel materials with enhanced thermoelectric (TE) performance is critical for advancing TE research. In this direction, this is the first report on TE properties of low-cost, nontoxic, and abundant core-shell Cu@Cu2O nanocomposites synthesized using a facile and cheap solution-phase method. They show ultralow thermal conductivity of nearly 10-3 of the copper bulk value, large thermopower of â¼373 µVK-1, and, consequently, a TE figure of merit of 0.16 at 320 K which is larger than those of many of the potential TE materials such as PbTe, SnSe, and SiGe, showing its potential for TE applications. The ultralow thermal conductivity is mainly attributed to the multiscale phonon scattering from intrinsic defects in Cu2O, grain boundaries, lattice-mismatched interface, as well as dissimilar vibrational properties. The large thermopower is associated with a sharp modulation in carrier density of states due to charge transfer between Cu and Cu2O nanoparticles and carrier energy filtering. They are tuned by varying the trioctylphosphine concentration.
ABSTRACT
The microfluidic approach emerges as a new and promising technology for the synthesis of nanomaterials. A microreactor allows a variety of reaction conditions to be quickly scanned without consuming large amounts of raw material. In this study, we investigated the synthesis of water soluble 1-thioglycerol-capped Mn-doped ZnS nanocrystalline semiconductor nanoparticles (TG-capped ZnS:Mn) via a microfluidic approach. This is the first report for the successful doping of Mn in a ZnS semiconductor at room temperature as well as at 80 °C using a microreactor. Transmission electron microscopy and x-ray diffraction analysis show that the average particle size of Mn-doped ZnS nanoparticles is â¼3.0 nm with a zinc-blende structure. Photoluminescence, x-ray photoelectron spectroscopy, atomic absorption spectroscopy and electron paramagnetic resonance studies were carried out to confirm that the Mn(2+) dopants are present in the ZnS nanoparticles.
