Improvement of thermoelectric properties and their correlations with electron effective mass in Cu1.98SxSe1−x

Abstract

Sulphur doping effects on the crystal structures, thermoelectric properties, density-of-states, and effective mass in Cu1.98SxSe1−x were studied based on the electrical and thermal transport property measurements, and first-principles calculations. The X-ray diffraction patterns and Rietveld refinements indicate that room temperature Cu1.98SxSe1−x (x = 0, 0.02, 0.08, 0.16) and Cu1.98SxSe1−x (x = 0.8, 0.9, 1.0) have the same crystal structure as monoclinic-Cu2Se and orthorhombic-Cu2S, respectively. Sulphur doping can greatly enhance zT values when x is in the range of 0.8≤ × ≤1.0. Furthermore, all doped samples show stable thermoelectric compatibility factors over a broad temperature range from 700 to 1000 K, which could greatly benefit their practical applications. First-principles calculations indicate that both the electron density-of-sates and the effective mass for all the compounds exhibit non-monotonic sulphur doping dependence. It is concluded that the overall thermoelectric performance of the Cu1.98SxSe1−x system is mainly correlated with the electron effective mass and the density-of-states.

Designing Stimuli‐Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

“…Zhao et al demonstrated the synthesis of poly ( dl ‐lactic‐ co ‐glycolic acid) (PLGA)‐encapsulated doxorubicin (DOX) and NaYF 4 :Yb,Er@NaGdF 4 for pH responsive drug delivery and cancer cell imaging. [ 24 ] Wang et al revealed the use of a novel ZnO‐functionalized UCNP for multifunctional cancer theranostics applications, including magnetic resonance imaging (MRI), upconversion luminescence (UCL) imaging, computed tomography (CT), and pH‐modulated drug release. The ZnO holds the anti‐cancer drug within the UCNPs pores until the ZnO is dissolved in the acidic pH of the TME to affect a pH‐responsive drug delivery.…”

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