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CuAgSe is a promising thermoelectric (TE) material for its superior carrier mobility and ultralow lattice thermal conductivity. Herein, we present a scalable colloidal method to prepare monodisperse CuAgSe nanocrystals with high yield. The collected powder sample was washed by a sulfur-free reagent of NaNH2 to remove the surface organic ligands (CuAgSe-W) and then annealed (CuAgSe-W-A). Both kinds of ligand-free samples were then hot pressed into dense pellets to measure the TE property. The results revealed that the crystal structure of both samples changed from low-temperature β-phase to high-temperature α-phase at around 465 K. Sample CuAgSe-W shows interesting temperature-dependent transition from N-type to P-type, which could be potentially used as thermal control transistor. Sample CuAgSe-W-A does not display this transition state but it exhibits potential for intermediate temperature TE applications with a figure-of-merit zT reaching 0.68 at 566 K. [ABSTRACT FROM AUTHOR]

Copper-based chalcogenides that contain abundant, low-cost and environmentally-friendly elements, are excellent materials for numerous energy conversion applications, such as photocatalysis, photovoltaics, photoelectricity and thermoelectrics (TE). Here, we present a high-yield and upscalable colloidal synthesis route for the production of monodisperse ternary I-III-VI2 chalcogenides nanocrystals (NCs), particularly stannite CuFeSe2, with uniform shape and narrow size distributions by using selenium powder as the anion precursor and CuCl2•2H2O and FeCl3 as the cationic precursors. The composition, the state of valence, size and morphology of the CuFeSe2 materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), respectively. Furthermore, the TE properties characterization of these dense nanomaterials compacted from monodisperse CuFeSe2 NCs by hot press at 623 K were preliminarily studied after ligand removal by means of hydrazine and hexane solution. The TE performances of the sintered CuFeSe2 pellets were characterized in the temperature range from room temperature to 653 K. Finally, the dimensionless TE figure of merit (ZT) of this Earth-abundant and intrinsic p-type CuFeSe2 NCs is significantly increased to 0.22 at 653 K in this work, which is demonstrated to show a promising TE materialand makes it a possible p-type candidate for medium-temperature TE applications. [ABSTRACT FROM AUTHOR]

CdSe:Eu nanocrystals were successfully synthesized and characterized by transmission electron microscopy, X-ray powder diffraction, and X-ray photoelectric spectroscopy. The CdSe:Eu nanocrystals showed enhanced green electrochemiluminescence (ECL) intensity when compared to pure CdSe nanocrystals. Further, the nanocrystals were used to design an ECL immunosensor for the detection of carcinoembryonic antigen (CEA) that has a linear response over the 1.0 fg·mL to 100 ng·mL CEA concentration range with a 0.4 fg·mL detection limit. The assay was applied to the determination of CEA in human serum samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu2SnSe3 nanocrystals was successfully synthesized by a “hot-injection” protocol. [•] Low-toxicity, inexpensive Se precursor was used. [•] The as-prepared CTSe nanocrystals can be used as promising thermoelectric materials. [ABSTRACT FROM AUTHOR]