Noncrystalline Hybrid Lead Halides with Liquid-Polymer Characteristics

Hybrid lead halide (HLH) semiconductors, particularly those featuring perovskite and its derivative structures, have been popular materials with many promising optoelectronic applications. In general, HLHs are predominantly crystalline solids, whether they are bulk single crystals, microcrystals, or nanocrystals. This paper shows that when some short-chain Jeffamine, a widely used polyetheramine, is used as the organic species, the resultant HLH would become noncrystalline with unusual liquid-polymer-like characteristics. In this material, Jeffamine ammoniums and lead halide octahedron frameworks are both arranged amorphously, while its optical properties are similar to those of crystalline HLHs. In contrast to conventional organic species, Jeffamine exhibits a disordered molecular packing, which is believed to account for the peculiar characteristics of the HLH products. Through A-site engineering with Jeffamine, even classic lead halide perovskites such as CsPbBr3 can acquire partial noncrystallinity and transform into a liquid-polymer-like form. This discovery demonstrates that Jeffamine as a novel organic species would confer liquid-polymer properties to the products, which may provide a strategy to transform HLH materials and classic halide perovskites into special “liquid semiconductors”, thereby potentially enabling new processing techniques and new designs of soft electronics

Alkylthiol-Enabled Se Powder Dissolution in Oleylamine at Room Temperature for the Phosphine-Free Synthesis of Copper-Based Quaternary Selenide Nanocrystals

Enhancement of Se solubility in organic solvents without the use of alkylphosphine ligands is the key for phosphine-free synthesis of selenide semiconductor nanocrystals (NCs). In this communication, we demonstrate the dissolution of elemental Se in oleylamine by alkylthiol reduction at room temperature, which generates soluble alkylammonium selenide. This Se precursor is highly reactive for hot-injection synthesis of selenide semiconductor NCs, such as Cu₂ZnSnSe₄, Cu­(InGa)­Se₂, and CdSe. In the case of Cu₂ZnSnSe₄, for example, the as-synthesized NCs possessed small size, high size monodispersity, strong absorbance in the visible region, and in particular a promising increase in photocurrent under AM1.5 illumination. The current preparation of the Se precursor is simple and convenient, which will promote the synthesis and practical applications of selenide NCs

Phosphine-Free Synthesis of Metal Chalcogenide Quantum Dots by Directly Dissolving Chalcogen Dioxides in Alkylthiol as the Precursor

Semiconductor quantum dots (QDs) are competitive emitting materials in developing new-generation light-emitting diodes (LEDs) with high color rendering and broad color gamut. However, the use of highly toxic alkylphosphines cannot be fully avoided in the synthesis of metal selenide and telluride QDs because they are requisite reducing agents and solvents for preparing chalcogen precursors. In this work, we demonstrate the phosphine-free preparation of selenium (Se) and tellurium (Te) precursors by directly dissolving chalcogen dioxides in the alkylthiol under the mild condition. The chalcogen dioxides are reduced to elemental chalcogen clusters, while the alkylthiol is oxidized to disulfides. The chalcogen clusters further combine with the disulfides, generating dispersible chalcogen precursors. The resulting chalcogen precursors are suitable for synthesizing various metal chalcogenide QDs, including CdSe, CdTe, Cu₂Te, Ag₂Te, PbTe, HgTe, and so forth. In addition, the precursors are of high reactivity, which permits a shorter QD synthesis process at lower temperature. Owing to the high quantum yield (QYs) and easy tunability of the photoluminescence (PL), the as-synthesized QDs are further employed as down-conversion materials to fabricate monochrome and white LEDs

Facile Synthesis of Cu₂GeS₃ and Cu₂MGeS₄ (M = Zn, Mn, Fe, Co, and Ni) Hollow Nanoparticles, Based on the Nanoscale Kirkendall Effect

Hollow nanostructures have shown charming properties beyond their solid counterparts, but the synthesis of multinary chalcogenide semiconductors with hollow nanostructures remains challenging, because of their complex components. In this work, we demonstrate a facile one-pot method to synthesize Cu₂GeS₃ hollow nanoparticles (NPs) based on Kirkendall effect by using dissolved GeO₂ as the Ge source. A theory model according to the diffusion kinetic and reaction kinetic is established to investigate the growth mechanism of Cu₂GeS₃ hollow NPs. By using Cu₂GeS₃ hollow NPs as the template, quaternary Cu₂MGeS₄ (M = Zn, Ni, Co, Fe and Mn) hollow NPs are further produced, which are more difficult to prepare, because of their excessive ion species. Furthermore, Cu₂GeS₃ hollow NP-based gas sensors are prepared, which exhibit outstanding sensitivity for the detection of ethanol gas, because of their large surface-to-volume ratio and small grain size

Improvement in Open-Circuit Voltage of Thin Film Solar Cells from Aqueous Nanocrystals by Interface Engineering

In this work, improved solar cells from aqueous CdTe NCs is achieved by replacing evaporated MoO_<i>x</i> with spiro-OMeTAD as a hole transfer layer. The increased <i>V</i>_oc and <i>J</i>_sc can be attributed to interfacial dipole effect and reduced back recombination loss, respectively. A high PCE of 6.56% for solar cells from aqueous NCs is obtained by optimizing the microstructure further

Conducting the Temperature-Dependent Conformational Change of Macrocyclic Compounds to the Lattice Dilation of Quantum Dots for Achieving an Ultrasensitive Nanothermometer

We report a ligand decoration strategy to enlarge the lattice dilation of quantum dots (QDs), which greatly enhances the characteristic sensitivity of a QD-based thermometer. Upon a multiple covalent linkage of macrocyclic compounds with QDs, for example, thiolated cyclodextrin (CD) and CdTe, the conformation-related torsional force of CD is conducted to the inner lattice of CdTe under altered temperature. The combination of the lattice expansion/contraction of CdTe and the stress from CD conformation change greatly enhances the shifts of both UV–vis absorption and photoluminescence (PL) spectra, thus improving the temperature sensitivity. As an example, β-CD-decorated CdTe QDs exhibit the 0.28 nm shift of the spectra per degree centigrade (0.28 nm/°C), 2.4-fold higher than those of monothiol-ligand-decorated QDs

One-Step Preparation of Cesium Lead Halide CsPbX₃ (X = Cl, Br, and I) Perovskite Nanocrystals by Microwave Irradiation

CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) are competitive emitting materials for illumination and display because of their outstanding photophysical properties. However, the conventional synthetic approaches suffer from low yields, complex procedures, and toxic chemicals. In this work, we demonstrate a one-step microwave-assisted approach to prepare CsPbX₃ NCs. The homogeneous heating and rapid temperature increment of microwave preparation facilitate the growth of CsPbX₃ NCs, producing the NCs with high photoluminescence quantum yields up to 90%, narrow emission full-width at half-maximum, and emission color tunable from blue to red. By optimizing the preparation conditions of the microwave-assisted approach, CsPbX₃ NCs with cation- and halide anion-controlled emission properties, tunable reaction rate, and enhanced stability are prepared. Light-emitting diode (LED) prototypes are further fabricated by employing the as-prepared CsPbX₃ NCs as the color conversion materials on commercially available 365 nm GaN LED chips

Icaritin increased but not induced alkaline phosphatase (ALP) activity during osteogenic differentiation of MSCs.

<p>(A) MSCs treated with Icaritin (10∧-8 M to 10∧-5 M) in absence of OS or in presence of OS for 3, 7 and 10 days respectively, then the cells were lysed and ALP activity assay was performed (OS: osteogenic supplements, ** p<0.01versus control; # p<0.05 and ## p<0.01 versus other group). (B) MSCs were treated the same as in (A) for 10 days, then ALP was stained with BCIP/NBT kit.</p

Icaritin promoted but not induced mineralization in osteogenic differentiation of MSC.

<p>(A) MSCs treated with Icaritin (10∧-8 M to 10∧-5 M) in absence of OS or in presence of OS for 16 days, then the calcium deposits were stained by Alizarin Red S (ARS). (B) The Alizarin Red S in (A) was eluted by 10% (wt/vol) cetylpyridinium chloride, and the concentrations were determined by absorbance measurement at 562 nm (** p<0.05).</p

Icaritin did not affect the proliferation, migration, and tube-like structure formation by HUVECs.

<p>(A) HUVECs were treated with the indicated concentrations of icaritin for 1, 2 and 3 days, and cell proliferation was determined by MTT assay, H₂O and DMSO served as negative controls, FGF2 served as positive control. (B) Quantification of chemotatic migration in HUVECs treated with Icaritin (10∧-6 M) or FGF2 in Transwell plates for 12 h. (C) Tube formation in HUVECs cultured on a layer of Matrigel with or without Icaritin (10∧-6 M) or FGF2 for 16 h observed using an inverted phase contract microscope with a video graphic system. (D) Tube length in (C) was quantitated using Image-Pro Plus software.</p