Dong Yao

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 Cu(2)ZnSnSe(4), Cu(InGa)Se(2), and CdSe. In the case of Cu(2)ZnSnSe(4), 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.

CsPbxMn1–xCl3 Perovskite Quantum Dots with High Mn Substitution Ratio

CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) are potential emitting materials for illumination and display applications, but toxic Pb is not environment- and user-friendly. In this work, we demonstrate the partial replacement of Pb with Mn through phosphine-free hot-injection preparation of CsPbxMn1-xCl3 QDs in colloidal solution. The Mn substitution ratio is up to 46%, and the as-prepared QDs maintain the tetragonal crystalline structure of the CsPbCl3 host. Meaningfully, Mn substitution greatly enhances the photoluminescence quantum yields of CsPbCl3 from 5 to 54%. The enhanced emission is attributed to the energy transfer of photoinduced excitons from the CsPbCl3 host to the doped Mn, which facilitates exciton recombination via a radiative pathway. The intensity and position of this Mn-related emission are also tunable by altering the experimental parameters, such as reaction temperature and the Pb-to-Mn feed ratio. A light-emitting diode (LED) prototype is further fabricated by employing the as-prepared CsPbxMn1-xCl3 QDs as color conversion materials on a commercially available 365 nm GaN LED chip.

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.

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 MoOx with spiro-OMeTAD as a hole transfer layer. The increased Voc and Jsc 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.

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.

Phosphine-free synthesis of heavy Co2+- and Fe2+-doped Cu2SnSe3 nanocrystals by virtue of alkylthiol-assistant Se powder dissolution

We demonstrate a phosphine-free method to synthesize heavy Co2+- and Fe2+-doped Cu2SnSe3 nanocrystals (NCs) by virtue of alkylthiol-assistant Se powder dissolution in organic solvents. The as-synthesized NCs exhibit a promising increase in photocurrent under AM1.5 illumination. Since the current method is simple and convenient it holds promise for facilitating the progress in photovoltaic devices from Cu-based NCs.

Au-Edged CuZnSe2 Heterostructured Nanosheets with Enhanced Electrochemical Performance

Two-dimensional (2D) nanomaterials and heterostructured nanocrystals (NCs) are two hot topics in current nanoresearch. However, reports on heterostructured NCs with 2D features are still rare. In this work, we demonstrate a one-pot colloidal chemistry route for synthesizing Au-CuZnSe2 heterostructures with spherical Au domains attached to the edge of a sheet of CuZnSe2 . This protocol involves the preferential formation of Au clusters and the seeded growth of CuZnSe2 sheets because of the lattice matching of CuSe with Au. As an example to demonstrate the importance of such heterostructures, the electrochemical performance of Au-CuZnSe2 heterostructured nanosheets is compared with that of heterostructured nanorods, Au NCs, and CuZnSe2 NCs. The heterostructured nanosheets exhibit the best electrochemical activity.

Multifunctional Reversible Fluorescent Controller Based on a One-Dimensional Photonic Crystal

With the aim to build a multifunctional solid fluorescent controller, a one-dimensional photonic crystal and CdSe fluorescent single layer were separated on the opposite sides of quartz substrates. The separation structure remarkably facilitates materials selection for the fluorescent controller, which allows one to freely choose the fluorescent substance and constituents of 1DPC from a wide range of available materials with the best desirable properties and without caring about the interactions between them. Fluorescent enhancement and weakened effect were successfully achieved when the excitation light was irradiated from different sides of the fluorescent device. In addition, the fluorescent intensity can be altered reversibly along with environmental pH values according to the change of a pH-responsive one-dimensional photonic crystal layer, which is quite different from a previously reported quenching mode. Meanwhile, the original position of the photonic stop band is essential for deciding what pH value would produce the best effect of fluorescent control. It provides a way to adjust the effect of fluorescent controller according to certain applied situations. The mechanism of fluorescent variation was confirmed by the assistance of a finite-difference time-domain simulation. Furthermore, this device is also able to modulate fluorescent wavelength and full width at half-maximum by overlapping the photonic stop band and the emission of CdSe. Therefore, this method offers a universal strategy for the fabrication of fluorescent controllers.

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.

Seed-mediated phase-selective growth of Cu2GeS3 hollow nanoparticles with huge cavities

Although significant progress has been achieved in the synthesis of hollow nanoparticles (NPs), research on copper-based multinary chalcogenide (CMC) semiconductor NPs with hollow structures is still less developed. In this work, we demonstrate an effective method for the phase-selective synthesis of cubic Cu2GeS3 hollow NPs (HNPs) with huge cavities and thin shells. This method includes the nucleation of Cu2−xS seeds, followed by unequal diffusion between Cu+ and Ge4+. A common rule for the phase-selective growth of CMC NPs has been revealed: the nucleation step is the crystal phase-determining step in the growth process of CMC NPs, and the sulfur sources govern the crystal phase of the nucleus. Because of their huge cavities, the as-prepared large Cu2GeS3 HNPs are proved to be macroporous materials with a specific surface area of 22.1 m2 g−1. Besides, cubic Cu2GeS3 HNPs with small cavities are also synthesized, following the same method with little modification. By integrating the advantages of the large Cu2GeS3 HNPs (high surface-to-volume area) and the small Cu2GeS3 HNPs (good dispersibility and monodispersity), a new kind of two-layer photoelectrode is prepared. Compared with the photoelectrodes prepared using pure large and small Cu2GeS3 HNPs, the two-layer photoelectrode exhibits superior performance for photoelectrochemistry due to the high interface area of the upper layer and the ideal compactness of the bottom layer.