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Compared to binary PbSe or PbS nanocrystals (NCs), ternary PbSe1−xSx alloyed NCs have unique electronic and optical properties such as high quantum efficiency, narrow band edge, and fast response time, and are widely used in infrared optoelectronic devices. In this work, high-quality composition-tunable monodisperse ternary PbSe1−xSx alloyed NCs were synthesized by employing cation exchange from host CdSe1−xSx alloyed NCs, which were pre-fabricated by using cadmium oxide, myristic acid and 1-octadecene (ODE) solutions of selenium/sulphur powders (Se/S-ODE), excluding toxic phosphine-containing solvents. The alloyed nature of PbSe1−xSx NCs was confirmed using powder X-ray diffraction (XRD). XRD patterns and field emission transmission electron microscopy (FETEM) images demonstrated that the average diameters of the resulting PbSe1−xSx alloyed NCs were not more than 5 nm, and ultraviolet-visible-near infrared (UV-vis-NIR) absorption spectra indicated that the NC size, hence the band gap, bared a linear relationship with the first absorption peak position. The temporal evolution of the absorption spectra revealed that the PbSe1−xSx alloyed NCs were air-stable due to the hybrid surface passivation of Cl− and Cd2+. X-ray fluorescence results indicated that slight stoichiometric deviations of PbSe1−xSx NCs occurred but never exceeded 15% of the expected composition, based on the amount of introduced hosts. [ABSTRACT FROM AUTHOR]

MoSe2 represents important layered transition metal dichalcogenides (TMDs) that have high electrocatalytic activity in the hydrogen evolution reaction (HER). A key issue to achieve excellent electrochemical properties of MoSe2 is to synthesize nanostructures that are composed of few-layered MoSe2 with abundant exposure of active edge sites. Nanoflowers of layered materials are promising building blocks for photocatalysis due to their large specific surface area and a wealth of exposed edge sites. In this work, free-standing colloidal MoSe2 nanoflowers, with a size of 250 nm, were synthesized by employing a quick and nontoxic phosphine-free solution-processing approach. Oleic acid (OA), 1-octadecene (ODE) and 1-octylamine (OLA) were primarily used as solvents to control the morphology of MoSe2 nanostructures. Experimental results revealed that the shape evolution of MoSe2 nanostructures started with a first fast precipitation of amorphous materials followed by crystallization of a few layers of nanosheets. The prepared MoSe2 nanoflowers demonstrated excellent HER activities with low overpotentials and small Tafel slopes, and the chronopotentiometry responses revealed good stability, making them promising materials for the electrocatalytic HER. [ABSTRACT FROM AUTHOR]

A low cost and large scale synthetic approach was developed for colloidal PbS quantum dots (QDs). The heat up strategy was adapted for large scale production, thioacetamide in oleylamine (OLA) was used as the sulphur precursor for low cost and safe synthesis, and PbCl2 in OLA was used as the lead precursor for a well passivated surface. Due to the balance between the diffusion coefficient and monomer oversaturation generated by the dissolution of small particles, an optimum growth temperature exists in the new synthesis. The synthesis was easily scaled up to produce 18 g of PbS QDs from one reaction batch, with a high chemical yield of ∼80% and the as synthesized QDs exhibit a high photoluminescence quantum yield of ＞40% and excellent air-stability of at least 60 days, due to the Cl− and oleate co-passivation. [ABSTRACT FROM AUTHOR]