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M-doped zinc oxide (ZnO) (M 5 Al and/or Ni) thermoelectric materials were fully densified at a temperature lower than 10001C using a spark plasma sintering technique and their microstructural evolution and thermoelectric characteristics were investigated. The addition of Al 2 O 3 reduced the surface evaporation of pure ZnO and suppressed grain growth by the formation of a secondary phase. The addition of NiO promoted the formation of a solid solution with the ZnO crystal structure and caused severe grain growth. The co-addition of Al 2 O 3 and NiO produced a homogeneous microstructure with a good grain boundary distribution. The microstructural characteristics induced by the co-addition of Al 2 O 3 and NiO have a major role in increasing the electrical conductivity and decreasing the thermal conductivity, resulting from an increase in carrier concentration and the phonon scattering effect, respectively, and therefore improving the thermoelectric properties. The ZnO specimen, which was sintered at 10001C with the co-addition of Al 2 O 3 and NiO, exhibited a ZT value of 0.6 Â 10 À3 K À1 , electrical conductivity of 1.7 Â 10 À4 X À1 . m À1 , the thermal conductivity of 5.16 W . (m . K) À1 , and Seebeck coefficient of À425.4 lV/K at 9001C. The ZT value obtained respects the 30% increase compared with the previously reported value, 0.4 Â 10 À3 K À1 , in the literature. J ournal

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Graphene oxide quantum dots (GOQDs) are usually prepared using expensive carbon precursors such as carbon nanotubes (CNT) or graphene under the strong acidic condition, which requires an additional purifying process. Here, we first develop a facile pulsed laser ablation in liquid (PLAL) technique for preparing GOQDs using earth-abundant and low-cost coal as a precursor. Only ethanol and coal are used to produce GOQDs with excellent optical properties. The prepared GOQDs exhibit excellent optoelectronic properties which can be successfully utilized in bioimaging applications.

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