Heterostructured Cu2S-In2S3 nanocrystals with various shapes and compositions were synthesized by a high-temperature precursor-injection method using the semiconductor nanocrystal Cu1.94S as a catalyst. The intrinsic cationic deficiencies formed at high temperature by Cu ions made the Cu1.94S nanocrystal a good candidate for catalyzing the nucleation and subsequent growth of In 2S3 nanocrystals, eventually leading to the formation of heterostructured Cu2S-In2S3 nanocrystals. Gelification of the reaction systems, which were composed of different types of nanocrystal precursors and solvent, was found to be a very effective measure for controlling the growth kinetics of the heterostructured particles. Consequently, matchsticklike Cu2S3-In2S3 heterostructured nanorods, teardroplike quasi-core/shell Cu2S@In2S3 nanocrystals, and pencil-like In2S3 nanorods were successfully obtained by manipulating the gelification of the reaction system; this formed a solid experimental basis for further discussion of the growth mechanisms for differently shaped and structured nanocrystals. By reaction with 1,10-phenanthroline, a reagent that strongly and selectively binds to Cu(+), a compositional transformation from binary matchsticklike Cu2S-In2S3 nanorods to pure In2S3 nanorods was successfully achieved.

Low-threshold two-photon-pumped (TPP) perovskite microcavity lasers are achieved in crystal perovskite 1D or 2D microstructures fabricated through a liquid-phase self-assembly method assisted by two distinct surfactant soft templates. The lasing actions from the perovskite materials exhibit a shape-dependent microcavity effect, which is subsequently utilized for the modulation of the lasing modes and for the achievement of two-photon-pumped single-mode perovskite microlasers.

Morphology control represents an important strategy for the development of functional nanomaterials and has yet to be achieved in the case of promising lead-free double perovskite materials so far. In this work, high-quality Cs 2 AgBiX 6 (X = Cl, Br, I) two-dimensional nanoplatelets were synthesized through a newly developed synthetic procedure. By analyzing the optical, morphological, and structural evolutions of the samples during synthesis, we elucidated that the growth mechanism of lead-free double perovskite nanoplatelets followed a lateral growth process from mono-octahedral-layer (half-unit-cell in thickness) cluster-based nanosheets to multilayer (three to four unit cells in thickness) nanoplatelets. Furthermore, we demonstrated that Cs 2 AgBiBr 6 nanoplatelets possess a better performance in photocatalytic CO 2 reduction compared with their nanocube counterpart. Our work demonstrates the first example with two-dimensional morphology of this important class of lead-free perovskite materials, shedding light on the synthetic manipulation and the application integration of such promising materials.

Indium phosphide (InP) core/shell quantum dots (QDs) without intrinsic toxicity have shown great potential to replace the widely applied cadmium‐containing QDs in next‐generation commercial display and lighting applications. However, it remains challenging to synthesize InP core/shell QDs with high quantum yields (QYs), uniform particle size, and simultaneously thicker shell thickness to reduce nonradiative Förster resonant energy transfer (FRET). Here, thick InP‐Based QLEDs shell InP/GaP/ZnS//ZnS core/shell QDs with high stability, high QY (≈70%), and large particle size (7.2 ± 1.3 nm) are successfully synthesized through extending the growth time of shell materials along with the timely replenishment of shelling precursor. The existence of GaP interface layer minimizes the lattice mismatch and reduces interfacial defects. While thick ZnS shell, which suppresses the FRET between closely packed QDs, ensures high PL QY and stability. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on InP core/shell QDs with the peak external quantum efficiency and current efficiency of 6.3% and 13.7 cd A−1, respectively, which are the most‐efficient InP‐based green quantum dot light‐emitting diodes (QLEDs) till now. This work provides an effective strategy to further improve heavy‐metal‐free QLED performance and moves a significant step toward the commercial application of InP‐based electroluminescent device.

Mesostructured metallic substrates composed of square pyramidal pits are shown to confine localized plasmons. Plasmon frequency tuning is demonstrated using white light reflection spectroscopy with a wide range of structure dimensions from 400 to 3000 nm. Using a simple plasmon cavity model, we demonstrate how the individual pit morphology and not their periodicity controls the resonance frequencies. By measuring the surface-enhanced Raman scattering ͑SERS͒ signals from monolayers of benzenethiol on the same range of mesostructures, we extract a quantitative connection between absorption, field enhancement, and SERS signals. The match between theory and experiment enables effective design of plasmon devices tailored for particular applications, such as optimizing SERS substrates. DOI: 10.1103/PhysRevB.76.035426 PACS number͑s͒: 73.20.Mf, 42.70.Qs, 72.15.Rn, 81.07.Ϫb Raman scattering is a crucial spectroscopic technique for identifying molecules through their vibrational resonances and has increasingly important applications in monitoring low concentrations of impurities or trace biomolecules.1-3 It has also been suggested for direct monitoring of coupling of molecular distortions and electronic transport in molecular electronics. [4][5][6] However, the terribly weak Raman cross section has always made such application problematic. The enormous enhancement in cross section when the molecules are held close to a metal surface with nanoscale roughness 7,8 has driven the hope that surface-enhanced Raman scattering ͑SERS͒ will become a viable and reproducible diagnostic. While improvements have been made in terms of enhancement factor, reproducibility, and in understanding that plasmons underpin such enhancements, 9 it is unclear how to precisely design nanostructures to optimize the Raman signatures. Over the last five years, we have shown that mesostructured metal films comprised of arrays of voids form excellent surfaces for localizing plasmons while retaining strong coupling to external light.10-13 Recently, we showed, using angularly resolved SERS on such void substrates, that incident photons are transducted both into and out of molecules via plasmons, 14 giving hope that reproducible substrates can be designed for specific applications. While most SERS research has focused on using the nanoscale junctions between metallic particles such as colloids 15 or lithographic arrays 16 that have broad plasmon resonances which can only be tuned through control of shape anisotropy or gap dimensions, the voids show strong sharp tunable plasmon resonances. Previous work has shown that optimized samples possess plasmon absorption that lies between the laser wavelength and outscattered Raman emission; 17-19 however, they are unable to make clear the quantitative link between plasmon resonant absorption and SERS emission.In this paper, we present calibrated spectroscopic measurements on systematically engineered plasmonic mesostructured metal surfaces. We show the quantitative connection between the resonance arising from ...

A simple one-pot method is developed to prepare size- and shape-controlled copper(I) sulfide (Cu(2)S) nanocrystals by thermolysis of a mixed solution of copper acetylacetonate, dodecanethiol and oleylamine at a relatively high temperature. The crystal structure, chemical composition and morphology of the as-obtained products are characterized by powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The morphology and size of the Cu(2)S nanocrystals can be easily controlled by adjusting the reaction parameters. The Cu(2)S nanocrystals evolve from spherical to disk-like with increasing reaction temperature. The spherical Cu(2)S nanocrystals have a high tendency to self-assemble into close-packed superlattice structures. The shape of the Cu(2)S nanodisks changes from cylinder to hexagonal prism with prolonged reaction time, accompanied by the diameter and thickness increasing. More interestingly, the nanodisks are inclined to self-assemble into face-to-face stacking chains with different lengths and orientations. This one-pot approach may extend to synthesis of other metal sulfide nanocrystals with different shapes and sizes.

We devised a hot-injection synthesis to prepare colloidal double-perovskite Cs 2 NaBiCl 6 nanocrystals (NCs). We also examined the effects of replacing Na + with Ag + cations by preparing and characterizing Cs 2 Na 1– x Ag x BiCl 6 alloy NCs with x ranging from 0 to 1. Whereas Cs 2 NaBiCl 6 NCs were not emissive, Cs 2 Na 1– x Ag x BiCl 6 NCs featured a broad photoluminescence band at ∼690 nm, Stokes-shifted from the respective absorption by ≥1.5 eV. The emission efficiency was maximized for low Ag + amounts, reaching ∼3% for the Cs 2 Na 0.95 Ag 0.05 BiCl 6 composition. Density functional theory calculations coupled with spectroscopic investigations revealed that Cs 2 Na 1– x Ag x BiCl 6 NCs are characterized by a complex photophysics stemming from the interplay of (i) radiative recombination via trapped excitons localized in spatially connected AgCl 6 –BiCl 6 octahedra; (ii) surface traps, located on undercoordinated surface Bi centers, behaving as phonon-assisted nonradiative decay channels; and (iii) a thermal equilibrium between trapping and detrapping processes. These results offer insights into developing double-perovskite NCs with enhanced optoelectronic efficiency.

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