Deriving Chiroptical Properties from Intrinsically Achiral Building Blocks of One-Dimensional CsPbBr Perovskite Nanowires.

Chirality is a ubiquitous feature in biological systems and occurs even in certain inorganic crystals. Interestingly, some inorganic nanocrystals have been shown to possess chirality, despite their achiral bulk forms. However, the mechanism of chirality formation and chiroptical responses in such nanocrystals is still ambiguous due to the presence of chiral organic ligands used to passivate such nanocrystals.

CsPbBr Perovskite Crack Platelet Nanocrystals and Their Biexciton Generation.

Lead halide perovskite nanocrystals have been extensively studied in recent years as efficient optical materials for their bright and color-tunable emissions. However, these are mostly confined to their 3D nanocrystals and limited to the anisotropic nanostructures. By exploring the Cs-sublattice-induced metal(II) ion exchange with Pb(II), crack CsPbBr perovskite platelet nanocrystals having polar surfaces in all three directions are reported here, which remained different than reported standard square platelets.

Partial Chemicalization of Nanoscale Metals: An Intra-Material Transformative Approach for the Synthesis of Functional Colloidal Metal-Semiconductor Nanoheterostructures.

Heterostructuring colloidal nanocrystals into multicomponent modular constructs, where domains of distinct metal and semiconductor phases are interconnected through bonding interfaces, is a consolidated approach to advanced breeds of solution-processable hybrid nanomaterials capable of expressing richly tunable and even entirely novel physical-chemical properties and functionalities. To meet the challenges posed by the wet-chemical synthesis of metal-semiconductor nanoheterostructures and to overcome some intrinsic limitations of available protocols, innovative transformative routes, based on the paradigm of partial chemicalization, have recently been devised within the framework of the standard seeded-growth scheme. These techniques involve regiospecific replacement reactions on preformed nanocrystal substrates, thus holding great synthetic potential for programmable configurational diversification.

Vertex-Oriented Cube-Connected Pattern in CsPbBr Perovskite Nanorods and Their Optical Properties: An Ensemble to Single-Particle Study.

The design of cube-connected nanorods is accomplished by connecting seed nanocrystals of a defined shape in a particular orientation or by etching selective facets of preformed nanorods. In lead halide perovskite nanostructures, which retain mostly a hexahedron cube shape, such patterned nanorods can be designed with the anisotropic direction along the edge, vertex, or facet of seed cubes. Combining the Cs-sublattice platform for transforming metal halides to halide perovskites with facet-specific ligand binding chemistry, herein, vertex-oriented patterning of nanocubes in one-dimensional (1D) rod structures is reported.

Hexahedron Symmetry and Multidirectional Facet Coupling of Orthorhombic CsPbBr Nanocrystals.

The cube shape of orthorhombic phase CsPbBr nanocrystals possesses the ability of selective facet packing that leads to 1D, 2D, and 3D nanostructures. In solution, their transformation with linear one-dimensional packing to nanorods/nanowires is extensively studied. Here, multifacet coupling in two directions of the truncated cube nanocrystals to rod couples and then to single-crystalline rectangular rods is reported.

Chemically Sculpturing the Facets of CsPbBr Perovskite Platelet Nanocrystals.

The facet chemistry of lead halide perovskite nanocrystals is critically important for determining their shape and interface ligand binding. In colloidal nanocrystals, these are mostly controlled by adopting specific synthetic strategies with a selection of the appropriate reactants. However, using selected ligands, the surface of preformed nanocrystals can be reconstructed without altering the crystal phase and lattice structure of their core.

Facet Engineering for Amplified Spontaneous Emission in Metal Halide Perovskite Nanocrystals.

Auger recombination and thermalization time are detrimental in reducing the gain threshold of optically pumped semiconductor nanocrystal (NC) lasers for future on-chip nanophotonic devices. Here, we report the design strategy of facet engineering to reduce the gain threshold of amplified spontaneous emission by manyfold in NCs of the same concentration and edge length. We achieved this hallmark result by controlling the Auger recombination rates dominated by processes involving NC volume and thermalization time to the emitting states by optimizing the number of facets from 6 (cube) to 12 (rhombic dodecahedron) and 26 (rhombicuboctahedrons) in CsPbBr NCs.

Nucleophile-Controlled Halide Release from the Substitution Reaction of Haloketone for Facet Tuning and Manganese Doping in CsPbCl Nanocrystals.

Halide content of the reaction medium not only enhances the brightness of CsPbCl nanocrystals but also, control the shape modulations as well as doping Mn(II) in these host nanocrystals. Correlating both the shape effect and doping, herein, an reaction of nucleophile-controlled halide release was explored for monitoring facets modulations and doping in CsPbCl nanocrystals. This was performed using alkyl amine as nucleophile which reacted with α-halo ketone, phenacyl chloride, to release chloride ions.

Epitaxial Orientation Angle Tuned Disk-on-Rod Nanoheterostructures for Boosting Charge Transfer.

Controlling the compositions of Se(VI) and Te(VI) ions in a 2D disk on 1D structures of Sb(V) chalcogenides, disk-on-rod heterostructures having three different epitaxial angles with different surface facets are reported. Te injection temperature determined the composition, ensuring heterostructure formation with trigonal SbSeTe disks on orthorhombic SbSe rods having orientation angles 180°, 135°, and 90°. The growth kinetics of disks connected at one/two heads of parent rods is manipulated using an Se precursor as a limiting reagent.

Tuning Crystal Plane Orientation in Multijunction and Hexagonal Single Crystalline CsPbBr Perovskite Disc Nanocrystals.

Two-dimensional-shaped CsPbBr platelet nanocrystals are widely studied for their bright high energy emission and self-assembly. These nanostructures are in orthorhombic phase, have a square shape, and have the vertical axis [001] perpendicular to the basal plane. Moreover, these are mostly single-crystalline structures with a continuous lattice and appear like slices of cube nanocrystals.

Transformation of Metal Halides to Facet-Modulated Lead Halide Perovskite Platelet Nanostructures on A-Site Cs-Sublattice Platform.

The conversion of metal halides to lead halide perovskites with B-site metal ion diffusion has remained a convenient approach for obtaining shape-modulated perovskite nanocrystals. These transformations are typically observed for materials having a common A-site Cs-sublattice platform. However, due to the fast reactions, trapping the interconversion process has been difficult.

Equilibriums in Formation of Lead Halide Perovskite Nanocrystals.

Physical insights related to ion equilibrium involved in the synthesis of lead halide perovskite nanocrystals remain key parameters for regulating the phase stability and luminescence intensity of these emerging materials. These have been extensively studied since the development of these nanocrystals, and different reaction processes controlling the formation of CsPbX nanocrystals are largely understood. However, growth kinetics related to the formation of these nanocrystals have not been established yet.

Development of an Efficient Immunosensing Platform by Exploring Single-Walled Carbon Nanohorns (SWCNHs) and Nitrogen Doped Graphene Quantum Dot (N-GQD) Nanocomposite for Early Detection of Cancer Biomarker.

In this work, a novel electrochemical immunosensor based on nitrogen doped graphene quantum dot (N-GQD) and single-walled carbon nanohorns (SWCNHs) was developed for the detection of α-fetoprotein (AFP), a cancer biomarker. Thus, to fabricate the platform of the immunosensor, nanocomposite architecture was developed by decorating N-GQD on the surface of the SWCNHs. The resulting hybrid architecture (N-GQD@SWCNHs) functioned as an exceptional base for the immobilization of antibody (Anti-AFP) through carbodiimide reaction with good stability and bioactivity.

Cs-Lattice Extension and Expansion for Inducing Secondary Growth of CsPbBr Perovskite Nanocrystals.

The increase of the stability of perovskite nanocrystals with respect to exposure to polar media, layers growth, or shelling with different materials is in demand. While these are widely studied for metal chalcogenide nanocrystals, it has yet to be explored for perovskite nanocrystals. Even growth of a single monolayer on any facet or on the entire surface of these nanocrystals could not be established yet.

Chemically Spiraling CsPbBr Perovskite Nanorods.

Light emitting lead halide perovskite nanocrystals are currently emerging as the workhorse in quantum dot research. Most of these reported nanocrystals are isotropic cubes or polyhedral; but anisotropic nanostructures with controlled anisotropic directions still remain a major challenge. For orthorhombic CsPbBr, the 1D shaped nanostructures reported are linear and along either of the axial directions ⟨100⟩.

Introducing B-Site Cations by Ion Exchange and Shape Anisotropy in CsPbBr Perovskite Nanostructures.

Lead halide perovskite nanocrystals, whether formed by their own nucleation and growth or by ion diffusion into the lattice of others, are still under investigation. Moreover, beyond isotropic nanocrystals, fabricating anisotropic perovskite nanocrystals by design has remained difficult. Exploring the lattice of orthorhombic-phase CsZnBr with the complete replacement of Zn tetrahedra by Pb octahedra, dimension-tunable anisotropic nanocrystals of CsPbBr are reported.

α-Halo Ketone for Polyhedral Perovskite Nanocrystals: Evolutions, Shape Conversions, Ligand Chemistry, and Self-Assembly.

Bright lead halide perovskite nanocrystals, which have been extensively studied in the past 5 years, are mostly confined to a six faceted hexahedron (cube/platelet) shape. With variations of ligand, precursor, reaction temperature, and surface modification, their brightness has been enhanced and phase became stable, but ultimate nanocrystals still retained the hexahedron cube or platelet shape in most of the hot injection reactions. In contrast, by exploration of α-halo ketone in amine as a halide precursor, different shaped nanocrystals without compromising the photoluminescence quantum yield (PLQY) are reported.

Doping the Smallest Shannon Radii Transition Metal Ion Ni(II) for Stabilizing α-CsPbI Perovskite Nanocrystals.

Red emitting α-CsPbI nanocrystals are highly phase sensitive to ambient exposure, and B-site doping with suitable cations is adopted as one of the most feasible approaches for their phase stability. There are several reports herein: Ni(II) ions having the smallest transition metal Shannon radii were explored for doping in these nanocrystals. This successfully stabilized the cubic phase and retained the intense emission of nanocrystals for nearly 2 months.

Presence of Metal Chloride for Minimizing the Halide Deficiency and Maximizing the Doping Efficiency in Mn(II)-Doped CsPbCl Nanocrystals.

Pretreatment using metal chlorides during the formation of halide deficient free perovskite nanocrystals is reported. Among several metal chlorides, Cu(II)Cl was observed to be ideal for the synthesis of highly emitting CsPbCl nanocrystals at high reaction temperature. Because high temperature remained more favorable for the dopant insertion, doping of Mn(II) was carried out under this halide-rich system, and nearly 68% photoluminescence quantum yield was recorded.

Insights of Diffusion Doping in Formation of Dual-Layered Material and Doped Heterostructure SnS-Sn:SbS for Sodium Ion Storage.

Insights into the formation mechanism of a dual-layered and doped heterostructure material SnS-Sn:SbS are reported. In the presence of mixed alkyl thiols, first nanotubes of SbS were formed, and upon introduction of Sn(IV), SnS was deposited onto the surface of these tubular structures. Upon further annealing at a constant temperature, sluggish transformation resulted in a Sn(II)S-Sn(IV) doped SbS heterostructure, which finally turned to flake-like layered doped SbS nanostructures.

Predominated Thermodynamically Controlled Reactions for Suppressing Cross Nucleations in Formation of Multinary Substituted Tetrahedrite Nanocrystals.

Group I-II-V-VI semiconducting CuM SbS (M = Zn, Cd, Mn and Cu) substituted tetrahedrite nanostructures remain a new class of multinary materials that have not been widely explored yet. Having different ions, the formation process of these nanostructures always has the possibility of formation of cross nucleations. Minimizing the reaction time, herein, a predominantly thermodynamic control approach is reported, which decouples the quaternary nucleations from their possible cross nucleations.