While the classical mechanism for the growth of colloidal chalcogenide nanocrystals is largely understood, fundamental insights for the growth of perovskite nanocrystals still remain elusive. Using nanoclusters of ∼0.6 nm diameter as monomers and growing to more than 25 nm in a single reaction, herein, the step growth process of perovskite CsPbBr 3 nanocrystals is reported. This is performed with a step-rise of the reaction temperature with correlating annealing time. The growth is so precise that ∼0.6 nm (nearly one unit cell) increments were successively monitored in parallel with the conversion of clusters to nanowires and then to thickness tunable platelets and finally to size-tunable cube-shaped nanostructures. The entire reaction was monitored optically and microscopically, and their step growths were correlated. From these observations, the possible growth mechanism for perovskite nanocrystals along with their shape transformations was proposed.

Highly emissive isotropic CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals are typically observed in a six-faceted cube shape. When a unique approach is adopted and the reaction medium is enriched with halides, arm growth on all six facets was carried out and reported. Analysis suggested that these armed nanostructures were obtained from intermediate polyhedron shaped structures having 26 facets, and these were formed under halide-deficient conditions. Surface energy calculations further supported the possible existence of all facets for both of these structures under different halide composition environments. The entire study was first explored for CsPbBr3 and then extended to CsPbCl3; however, for CsPbI3 nanocrystals, Sr­(II) dopant was used for obtaining stable emission. Arm lengths could also be tuned with a function of reaction temperature for CsPbBr3. Formation of stable facets in polyhedron shaped nanostructures and their transformation to respective hexapods under halide-deficient and halide-rich conditions add new fundamental concepts for these nanostructures and their shape evolutions.

We report the synthesis of colloidal CsPbX3–Pb4S3Br2 (X = Cl, Br, I) nanocrystal heterostructures, providing an example of a sharp and atomically resolved epitaxial interface between a metal halide perovskite and a non-perovskite lattice. The CsPbBr3–Pb4S3Br2 nanocrystals are prepared by a two-step direct synthesis using preformed subnanometer CsPbBr3 clusters. Density functional theory calculations indicate the creation of a quasi-type II alignment at the heterointerface as well as the formation of localized trap states, promoting ultrafast separation of photogenerated excitons and carrier trapping, as confirmed by spectroscopic experiments. Postsynthesis reaction with either Cl– or I– ions delivers the corresponding CsPbCl3–Pb4S3Br2 and CsPbI3–Pb4S3Br2 heterostructures, thus enabling anion exchange only in the perovskite domain. An increased structural rigidity is conferred to the perovskite lattice when it is interfaced with the chalcohalide lattice. This is attested by the improved stability of the metastable γ phase (or “black” phase) of CsPbI3 in the CsPbI3–Pb4S3Br2 heterostructure.

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Antimonene, an emerging two‐dimensional material, has garnered tremendous interest due to its intriguing structure and fascinating electronic properties. However, the synthesis of high‐quality few‐layer antimonene nanosheets, which can only be produced by exfoliation or epitaxial growth on exotic substrates, has greatly hindered the development of this new field. Herein, few‐layer hexagonal and functionalized antimonene nanosheets were successfully prepared from SbCl3 solutions for the first time by exclusively promoting their anisotropic growth in a colloidal solution. Oleylamine was selected as the reducing agent, rather than oleic acid, and dodecylthiol was key to preventing the formation of antimony oxide. Additionally, halide ions adsorbed on the surface also influenced the anisotropic growth of hexagonal antimonene nanosheets. Atomic force microscopy (AFM) revealed that the sheets were ≈5 nm thick; Raman spectroscopy and X‐ray diffraction (XRD) revealed a rhombohedral atomic structure (β‐Sb) with excellent stability.

Phosphor with extremely narrow emission line widths, high brightness, and wide color emission tunability in visible regions is required for display and lighting applications, yet none has been reported in the literature so far. In the present study, single-sized lead halide perovskite (APbX 3; A = CH3NH3 and Cs; X = Cl, Br, and I) nanocrystalline (NC) phosphors were achieved for the first time in a one-pot reaction at room temperature (25 °C). The size-dependent samples, which included four families of CsPbBr3 NCs and exhibited sharp excitonic absorption peaks and pure band gap emission, were directly obtained by simply varying the concentration of ligands. The continuity of the optical spectrum can be successively tuned over the entire UV-visible spectral region (360-610 nm) by preparing CsPbCl3, CsPbI3, and CsPb(Y/Br)3 (Y = Cl and I) NCs with the use of CsPbBr3 NCs as templates by anion exchange while maintaining the size of NCs and high quantum yields of up to 80%. Notably, an emission line width of 10-24 nm, which is completely consistent with that of their single particles, indicates the formation of single-sized NCs. The versatility of the synthetic strategy was validated by extending it to the synthesis of single-sized CH3NH3PbX 3 NCs by simply replacing the cesium precursor by the CH3NH3 X precursor.

CsPbBr 3 nanoclusters have been synthesized by several groups and mostly employed as single-source precursors for the synthesis of anisotropic perovskite nanostructures or perovskite-based heterostructures. Yet, a detailed characterization of such clusters is still lacking due to their high instability. In this work, we were able to stabilize CsPbBr 3 nanoclusters by carefully selecting ad hoc ligands (benzoic acid together with oleylamine) to passivate their surface. The clusters have a narrow absorption peak at 400 nm, a band-edge emission peaked at 410 nm at room temperature, and their composition is identified as CsPbBr 2.3 . Synchrotron X-ray pair distribution function measurements indicate that the clusters exhibit a disk-like shape with a thickness smaller than 2 nm and a diameter of 13 nm, and their crystal structure is a highly distorted orthorhombic CsPbBr 3 . Based on small- and wide-angle X-ray scattering analyses, the clusters tend to form a two-dimensional (2D) hexagonal packing with a short-range order and a lamellar packing with a long-range order.

Non-cadmium" dual emissive QDs have been directly synthesized using a one-pot hot-injection technique. A white LED was successfully fabricated using a commercial blue-LED chip combined with the optimal QDs. ABSTRACTThe global demand for resource sustainability is growing. Thus, the development of single-source environment-friendly colloidal semiconductor nanocrystal (NC) phosphors with broadband emission is highly desirable for use as color converters in white light-emitting diodes (WLEDs). We report herein the gram-scale synthesis of single-source, cadmium-free, dual-emissive Mn-doped Zn-Cu-In-S NCs (d-dots) by a simple, non-injection, and low-cost approach in one-pot fashion. This synthesis approach led to the formation of NCs with continuously varying compositions in a radial direction because the reactivity of precursors totally differed among these precursors. Consequently, d-dots exhibited two emission bands, one of which was due to Mn-related emissions and the other was due to the band edge of Zn-Cu-In-S NCs. Emission peaks assigned to band edge were tunable by simple control of particle size and composition. The prepared d-dots also exhibited the characteristic zero self-absorption, a quantum yield of 46%, and good thermal stability. A combination of a commercial blue LED chip with optimal d-dots as color converters gave a high color rending index of up to 90, Commission International de l'Eclairage color coordinates of (0.332, 0.321), and correlated color temperature of 5680 K. These results suggested that this cadmium-free, excellent thermally stable single-phase d-dot phosphor had potential applications in WLEDs. Nano Research DOI () Research Article| www.editorialmanager.com/nare/default.asp 2 Nano Res.