Large-scale heterogeneous synthesis of monodisperse high performance colloidal CsPbBr_(3)nanocrystals

Colloidal lead halide perovskite nanocrystals(LHP NCs)are promising semiconductor materials for optoelectronic devices,but the high ionicity of LHP NCs makes their crystallization control and post-treatment difficult.Here,phosphonic acids(PAs)are employed as ligands to design a solid-liquid heterogeneous reaction system to regulate the LHP NC crystallization and achieve the desired focusing growth.During the heterogeneous synthesis,the precursors in the liquid phase are responsible for the burst nucleation and initial growth of NCs.Afterwards,the focusing growth of NCs is supported by the precursors released from the solid phase.In addition,the strong binding ability of PAs enables effective passivation of LHP NCs.Without post-treatment,gram-scale monodisperse CsPbBr_(3)NCs having photoluminescence with a full width at half-maximum of 18 nm and a quantum yield of near-unity are obtained.The CsPbBr_(3)NCs covered by a compact ligand layer keep initial quantum yield even after 18 cycles of purification,exhibiting excellent stability against polar solvents,ultraviolet irradiation and heat treatment.As scintillators,the prepared CsPbBr_(3)NCs show strong radioluminescence emission and high-resolution X-ray imaging.

Heterogeneous system synthesis of high quality PbS quantum dots for efficient infrared solar cells

As promising optoelectronic materials,lead sulfide quantum dots(PbS QDs)have attracted great attention.However,their applications are substantially limited by the QD quality and/or complicated synthesis.Herein,a facile new synthesis is developed for highly monodisperse and halide passivated PbS QDs.The new synthesis is based on a heterogeneous system containing a PbCl_(2)-Pb(OA)_(2)solid-liquid precursor solution.The solid PbCl_(2)inhibits the diffusion of monomers and maintains a high oversaturation condition for the growth of PbS QDs,resulting in high monodispersities.In addition,the PbCl_(2)gives rise to halide passivation on the PbS QDs,showing excellent stability in air.The high monodispersity and good passivation endow these PbS QDs with outstanding optoelectronic properties,demonstrated by a 9.43%power conversion efficiency of PbS QD solar cells with a bandgap of~0.95 eV(1,300 nm).We believe that this heterogeneous strategy opens up a new avenue optimizing for the synthesis and applications of QDs.

Effects of inorganic chlorine source on dioxin formation using fly ash from a fluidized bed incinerator

Chlorine source is indispensable for polychlorinated dibenzo-p-dioxin and furan （PCDD/F） formation during municipal solid waste （MSW） incineration. Inorganic chlorine compounds were employed in this study to investigate their effects on PCDD/F formation through heterogeneous synthesis on fly ash surfaces. A fly ash sample obtained from a fluidized bed incinerator was sieved to different size fractions which served as the PCDD/F formation sources. The capability of different metal chlorides which facilitate the formation of PCDDs/Fs was found to follow the trends： Na 〈 Mg 〈 K 〈 AI 〈 Ca, when two particle fractions of 〉177 μm and 104-125 μm were used in the experiments. However, the capability of NaCI, MgCl2 and KCI did not seem much different from each other, whereas CaCl2 and AlCl3 were much more active in PCDD/F formation. NaCl and MgCl2 were relatively effective to produce more PCDDs, while KC1, AICl3 and CaCl2 generated more PCDFs during heterogeneous reactions occurring on fly ash. 2,3,7,8-TCDF was the most significant contributor to the toxicity of the PCDDs/Fs formed from inorganic chlorine sources. Decreasing the sizes of fly ash particles led to more active formation of PCDDs/Fs when NaCl was used as inorganic chlorine in the experiment. The highest PCDDs/Fs produced from particles with size 〈37 μm, while the lowest PCDDs/Fs produced from particles with size 〉177μm. The toxicity generally increased with decreasing size of the fly ash particles. The formation of PCDDs was mainly facilitated by the two size fractions, 104-125 μm and 〈37μm, while the formation of PCDFs was favored by the two other size fractions, 〉177 μm and 53-104 μm.

Microwave-assisted efficient synthesis of azlactone derivatives using 2-aminopyridine-functionalized sphere SiO_2 nanoparticles as a reusable heterogeneous catalyst

In the present work, the highly efficient Erlenmeyer synthesis of azlactones catalyzed by 2- aminopyridine, supported on nano-sphere Si02 is reported. First, the silica nanoparticles were modified with triethoxysilylpropyl chloride and then 2-aminopyridine was attached to the support via covalent linkages. This new heterogenized catalyst was used for efficient microwave-assisted synthesis of azlactone derivatives with Ac20 as a condensing agent under solvent-free conditions. The present method offers advantages including high yields, short reaction times and simple work-up. Also, the catalyst can be easily recycled and reused several times, which makes this method attractive, economic and environmentally-benign.