Chiral Morphology Research Articles

Chiral 432 Helicoid II Nanoparticle Synthesized with Glutathione and Poly(T)20 Nucleotide

AbstractFinding a novel method to generate a chiral plasmonic material has been highlighted in the last decades for its unique light‐matter interactions. Recently, an aqueous based peptide directed synthesis of chiral plasmonic gold nanoparticle with exceptional chiroptic response has been reported. Especially, the facile and precise control of chirality using biomolecules allows potential expansion of chiral metamaterial synthesis. In this work, we show a significant enhancement of chiroptic response by simultaneous introduction of multiple bio‐molecular chiral modifiers, glutathione and homooligonucleotide containing thymine. Compared to previously synthesized single chiral plasmonic nanoparticles using only glutathione molecules, further addition of an oligonucleotide into the growth solution induces a two‐fold increase of dissymmetric factor. We believe that the presented synthetic method proposes an effective route of chiral metamaterial morphology and property control for versatile applications.

Chirality control of inorganic materials and metals by peptides or amino acids

In this review, we exploit recent investigations to identify the exceptional roles of amino acids and peptides in chirality, based on local atomic conformation to macroscopic chiral morphology.

Chiral Surface and Geometry of Metal Nanocrystals.

Chirality is a basic property of nature and has great importance in photonics, biochemistry, medicine, and catalysis. This importance has led to the emergence of the chiral inorganic nanostructure field in the last two decades, providing opportunities to control the chirality of light and biochemical reactions. While the facile production of 3D nanostructures has remained a major challenge, recent advances in nanocrystal synthesis have provided a new pathway for efficient control of chirality at the nanoscale by transferring molecular chirality to the geometry of nanocrystals. Interestingly, this discovery stems from a purely crystallographic outcome: chirality can be generated on high-Miller-index surfaces, even for highly symmetric metal crystals. This is the starting point herein, with an overview of the scientific history and a summary of the crystallographic definition. With the advance of nanomaterial synthesis technology, high-Miller-index planes can be selectively exposed on metallic nanoparticles. The enantioselective interaction of chiral molecules and high-Miller-index facets can break the mirror symmetry of the metal nanocrystals. Herein, the fundamental principle of chirality evolution is emphasized and it is shown how chiral surfaces can be directly correlated with chiral morphologies, thus serving as a guide for researchers in chiral catalysts, chiral plasmonics, chiral metamaterials, and photonic devices.

Static and dynamic properties of pre-twisted leaves and stalks with varying chiral morphologies

The mechanical properties and biological functions of tissues and organs in plants are closely related to their structural forms. In this study, we have performed systematic measurements and found that the leaves and stalks of several species of emergent plants exhibit morphologies of twisting and gradient chirality. Inspired by the experimental findings, we investigate, both theoretically and numerically, the static bending and vibrational properties of these plant organs. By modeling the leaves and stalks as pre-twisted cantilever beams, the effects of the cross-sectional geometry, loading condition, handedness perversion, twisting configuration, and morphological gradient, on their mechanical behavior are evaluated. Our analysis reveals that both static and dynamic responses of the beams can be easily tuned by changing their structural parameters. For any part of the beams, its chiral morphology has more significant influences on the overall structural performance (e.g., bending stiffness and natural frequencies) if it is closer to the clamped end. This work not only deepens our understanding of the structure–property–function interrelations of chiral plants, but also holds potential applications in the bio-inspired design of innovative devices and structures.

Bioinspired Toolkit Based on Intermolecular Encoder toward Evolutionary 4D Chiral Plasmonic Materials.

Over the last two decades, nanophotonics, including plasmonics and metamaterials, have promised compelling opportunities for exotic control over light-matter interactions. The strong chiral light-matter interaction is a representative example. Three-dimensional (3D) chirality has existed naturally only in organic molecules and bio-organisms, but a negligible chiroptic effect was attained with these naturally occurring materials because of their small absorption cross sections. However, inspired by biological chirality, nanophotonic chiral materials have greatly expanded the design space of accessible chiroptic effects (e.g., pushing the chiral light-matter interaction to an exceptional regime, such as a broad-band circular polarizer, negative refractive index, and sensitive chiral sensing). Nevertheless, it is still a challenge to achieve precisely defined and dynamically reconfigurable chiral morphologies that further increase the chiroptic effect. Biological systems continue to inspire approaches to the design and synthesis of precisely defined 3D nanostructures. In particular, a living organism can program the evolutionary pathway of highly complexed 3D chiral morphology precisely from the molecular scale to the macroscopic scale while simultaneously enabling dynamic reconfiguration of their chirality. What if we could harness the power of biological selectivity and evolutionary capability in synthesizing chiral plasmonic materials? We envisioned that platform technology mimicking biological principles would enable control of 3D chiral structures for effective plasmonic interactions with polarized light and further impart the concept of time-dependent evolution (3D + 1D = 4D) to bring about responsive and dynamic changes in chiral plasmonics. In this Account, we review our efforts to develop the biomolecule-based synthesis of 3D chiral plasmonic materials and share the vision that as in biological systems, chirality can be programmed at the molecular level and hierarchically transferred at multiple scales to develop macroscopic chirality. Accompanied by a biomimetic time-dependent chirality of singular plasmonic nanometals, we also summarize recent achievements in the chemistry and nanophotonics communities pursuing 4D plasmonics that are closely related to our research. The biomimetic and bioinspired approaches discussed in this Account will provide new synthetic insights into implementing chiral nanomaterials and extend the range of accessible nanophotonic design. We hope that the molecular encoding approach will be useful to achieve dynamic light-matter interactions at unprecedented dimensions, time scales, and chirality.

Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

AbstractNano‐ and microsized chiral materials are receiving significant attention because of their unique characteristics, which include chiroptical activities and enantioselective interactions with living materials. However, the realization of chiral morphologies in such small‐scale materials has been an issue because of the complicated fabrication methods and limited material selection. In this study, a facile and reproducible method is developed for fabricating 3D chiral microwrinkles with twisted shapes by asymmetric and biaxial buckling. Soft polydimethylsiloxane (PDMS) substrates are asymmetrically stretched with angled biaxial strains and exposed to UV/ozone to prepare hard silica layers on top of the PDMS substrates to induce microwrinkles. The chiral shapes are controlled by changing the angle (θ) between the two strain axes and the UV/ozone exposure times (t1, t2) in each stage of buckling. The 3D chiral microwrinkles are shaped like “fusilli pasta” and occupy an area of 1.5 cm × 1.5 cm. The patterned area can be easily scaled, and no innate chiral biomaterial is necessary. This method could be widely extended to the fabrication of diverse types of chiral materials for advanced optical and bio‐applications.

Cysteine Induced Chiral Morphology in Palladium Nanoparticle

AbstractNew morphology of palladium nanoparticles is demonstrated by utilizing the interaction of amino acid and palladium metallic surface. Chiral cysteine molecules induce chiral spiral structure evolution. The resulting spiral palladium nanoparticles show rotational direction preference with respect to the handedness of the added cysteine molecule. The strong correlation of the resulting morphologies with surfactant and cysteine concentration exists for effective generation of chirality. Synthesized chiral palladium nanoparticles are around 100 nm sized cubic based nanoparticles with each face of the cube containing a spiral structure. Generation of nanoparticle morphology is studied through growth of time‐dependent morphology evolution with statistical analysis of spiral structure formation. The reported synthesis method can provide a new route to nanomaterial design for enantioselective catalysis and sensing.

Facile synthesis of chiral (right-handed) calcium carbonate with exceptional enantioseparation performance of dibenzoyltartaric acid

The chiral morphology of calcium carbonate (mainly vaterite) was successfully synthesized by using CaCl2 under l-aspartic acid guiding by diffusion of in-site generation of CO2 and NH3 from (NH4)2CO3 and NH3·H2O. Its structure was characterized by XRD, SEM/TEM and FT-IR, it indicated that the helical-shaped chiral calcium carbonate was uniform in a diameter of 10–20 μm and height of 1 μm, and tortuous nanosheets with a thickness of 50 nm were evolved more abundant from center to edge in counterclockwise. The enantioseparation performance for racemic dibenzoyltartaric acid was evaluated, the chiral calcium carbonate showed certain recognition ability for l-dibenzoyltartaric acid due to its better matching with l-dibenzoyltartaric acid molecules in stereochemical structure. Chiral separation ability for dibenzoyltartaric acid could be significantly improved by dibutyl maleate modification of chiral calcium carbonate; the maximal ee values for dibenzoyltartaric acid increased from 20.62% to 62.15%. The synergism of chiral helical-shaped suprastructure, large proportion of vaterite and modification of surface by functional group resulted in the excellent enantiomer separation.

Circularly polarized thermal emission from chiral metasurface in the absence of magnetic field

We report on the thermal radiation source which emits circularly polarized thermal radiation in the absence of an external magnetic field. The geometry of thermal source includes a photonic crystal slab waveguide with chiral morphology. We show that due to the absence of a mirror symmetry of such metasurface, the thermally generated electromagnetic waves are circularly polarized with the circular polarization degree of 0.87. Using the Fourier modal method we study the structure eigenmodes and analyze the field distributions in them.

Chirality-controlled crystallization via screw dislocations

Chirality plays an important role in science from enantiomeric separation in chemistry to chiral plasmonics in nanotechnology. However, the understanding of chirality amplification from chiral building blocks to ordered helical superstructures remains a challenge. Here, we demonstrate that topological defects, such as screw dislocations, can drive the chirality transfer from particle to supramolecular structure level during the crystallization process. By using a model system of chiral particles, which enables direct imaging of single particle incorporation into growing crystals, we show that the crystallization kinetic pathway is the key parameter for monitoring, via the defects, the chirality amplification of the crystalline structures from racemic to predominantly homohelical. We provide an explanation based on the interplay between geometrical frustration, racemization induced by thermal fluctuations, and particle chirality. Our results demonstrate that screw dislocations not only promote the growth, but also control the chiral morphology and therefore the functionality of crystalline states.

Revealing chiral cell motility by 3D Riesz transform-differential interference contrast microscopy and computational kinematic analysis

Left–right asymmetry is a fundamental feature of body plans, but its formation mechanisms and roles in functional lateralization remain unclear. Accumulating evidence suggests that left–right asymmetry originates in the cellular chirality. However, cell chirality has not yet been quantitatively investigated, mainly due to the absence of appropriate methods. Here we combine 3D Riesz transform-differential interference contrast (RT-DIC) microscopy and computational kinematic analysis to characterize chiral cellular morphology and motility. We reveal that filopodia of neuronal growth cones exhibit 3D left-helical motion with retraction and right-screw rotation. We next apply the methods to amoeba Dictyostelium discoideum and discover right-handed clockwise cell migration on a 2D substrate and right-screw rotation of subcellular protrusions along the radial axis in a 3D substrate. Thus, RT-DIC microscopy and the computational kinematic analysis are useful and versatile tools to reveal the mechanisms of left–right asymmetry formation and the emergence of lateralized functions.

Chiral Morphology of Calcium Carbonate Mineralized in Agarose Gel

Calcareous crystallites with chiral morphology are difficult to obtain in vitro. Using the d‐form of aspartic acid as crystal modifier, calcium carbonate with chiral morphology has been obtained in agarose gel. We show that the formation of the chiral morphology of crystallites does not necessarily involve complicated cellular processes.

A DFT study of hypercoordinated copper silicide nanotubes

Abstract The stability and electronic structures of copper silicide nanotubes (CuSiNTs) are calculated using first-principles density functional theory. Here these CuSiNTs of various different diameters, chiral vectors and morphologies were obtained by rolling up a novel two-dimensional hypercoordinated Cu2Si monolayer with high stability (Yang et al., J. Am. Chem. Soc. 137 (2015) 2757−2762). Electronic structure calculations showed that these CuSiNTs are conductors independent of their chiral vectors, diameters and morphologies. In addition, molecular dynamics (MD) simulations of the (6, 0) tube and the (8, 4) tube were performed. It was found that the (8, 4) tube has very good thermal stability and that its structure does not break down during MD simulations at initial temperatures up to 1500 K. Based on their electrical conductivity and good thermal stability, these CuSiNTs are promising candidates to envision application as metallic connections in nanoscale electronic devices.

A semi-combinatorial approach for investigating polycatenar ligand-controlled synthesis of rare-earth fluoride nanocrystals.

Rare-earth nanocrystals (RE NCs) are a valuable class of nanomaterials due to their ability to bring the attractive properties of rare earth bulk crystals to biomedical applications and solution-processable engineering. Of the bottom-up synthesis approaches, solvothermal methods yield highly crystalline and monodisperse RE NCs. Herein, we report a polycatenar ligand controlled synthesis of RE NCs using a semi-combinatorial approach with a microreactor setup that enables the investigation of the influences of several reaction parameters on the growth of the RE NCs. This approach enabled the discovery of conditions that yield highly monodisperse elongated plates with neutral, positive, and negative curvatures, as well as provide evidence of the formation of chiral morphologies.

Supramolecular Chirality: Vesicle-to-Chiral Helix Transition of the Micelles Consisting of a Sugar-Bearing Calix[4]arene Surfactant.

Supramolecular self-assembly and the resulting chiral transfer from the molecular level to the nanoscale is a major topic in modern supramolecular chemistry. We synthesized a galactose-bearing calix[4]arene surfactant (chiral) and mixed it with a primary amine-bearing analogue (achiral). The mixture showed strong induced circular dichroism (ICD) at an almost 3:2 molar ratio of the two surfactants, and exothermic heat was observed upon mixing. The magnitude of ΔH was comparable to that of van der Waals interactions. This phenomenon indicated that the ICD can be ascribed to the formation of a new supramolecular assembly in which the stoichiometric interaction between the two molecules leads to complexation and the resultant complex has chiral morphology. Transmission electron microscopy and small-angle X-ray scattering showed that the galactose-bearing surfactant forms vesicles, and the mixing induces a transition from the vesicles to threadlike cylinders with a diameter of ∼3.0 nm. We presume that these cylinder are twisted because of chiral transfer from the chiral galactose moiety and show ICD.

Chirality-dependent flutter of Typha blades in wind.

Cattail or Typha, an emergent aquatic macrophyte widely distributed in lakes and other shallow water areas, has slender blades with a chiral morphology. The wind-resilient Typha blades can produce distinct hydraulic resistance for ecosystem functions. However, their stem may rupture and dislodge in excessive wind drag. In this paper, we combine fluid dynamics simulations and experimental measurements to investigate the aeroelastic behavior of Typha blades in wind. It is found that the chirality-dependent flutter, including wind-induced rotation and torsion, is a crucial strategy for Typha blades to accommodate wind forces. Flow visualization demonstrates that the twisting morphology of blades provides advantages over the flat one in the context of two integrated functions: improving wind resistance and mitigating vortex-induced vibration. The unusual dynamic responses and superior mechanical properties of Typha blades are closely related to their biological/ecosystem functions and macro/micro structures. This work decodes the physical mechanisms of chirality-dependent flutter in Typha blades and holds potential applications in vortex-induced vibration suppression and the design of, e.g., bioinspired flight vehicles.

Microscopic origin of chiral shape induction in achiral crystals.

In biomineralization, inorganic materials are formed with remarkable control of the shape and morphology. Chirality, as present in the biomolecular world, is therefore also common for biominerals. Biomacromolecules, like proteins and polysaccharides, are in direct contact with the mineral phase and act as modifiers during nucleation and crystal growth. Owing to their homochirality--they exist only as one of two possible mirror-symmetric isomers--their handedness is often transferred into the macroscopic shape of the biomineral crystals, but the way in which handedness is transmitted into achiral materials is not yet understood at the atomic level. By using the submolecular resolution capability of scanning tunnelling microscopy, supported by photoelectron diffraction and density functional theory, we show how the chiral 'buckybowl' hemibuckminsterfullerene arranges copper surface atoms in its vicinity into a chiral morphology. We anticipate that such new insight will find its way into materials synthesis techniques.

Alternate nonmagnetic and magnetic multilayer nanofilms deposited on carbon nanocoils by atomic layer deposition to tune microwave absorption property

In this study, alternate nonmagnetic Al2O3 and magnetic Fe3O4 multilayer nanofilms with precisely controlled thickness were deposited on carbon nanocoils by atomic layer deposition. The as-synthesized composites exhibit superior microwave absorption performance, which can be flexibly tuned by varying the thickness of each individual layer or the number of layers. The excellent absorption performance arises from the effective impedance matching, alternate multilayer nanostructure and chiral morphology of the samples, and efficient magnetic loss from magnetic constituents. Our work demonstrates a new strategy to tune microwave absorption performance and this method can be extended to exploit other excellent microwave absorbers with alternate multilayer hetero-nanostructures owing to the convenient control of electromagnetic parameters.

Synergistic Effects of Chiral Morphology and Reconfiguration in Cattail Leaves

Cattail, a type of herbaceous emergent aquatic macrophyte, has upright-standing leaves with a large slenderness ratio and a chiral morphology. With the aim of understanding the effect of chiral morphology on their mechanical behavior, we investigated, both experimentally and theoretically, the twisting chiral morphologies and wind-adaptive reconfigurations of cattail leaves. Their multiscale structures were observed by using optical microscope and scanning electron microscopy. Their mechanical properties were measured by uniaxial tension and three-point bending tests. By modeling a chiral leaf as a pre-twisted cantilever-free beam, fluid dynamics simulations were performed to elucidate the synergistic effects of the leaf's chiral morphology and reconfiguration in wind. It was observed that the leaves have evolved multiscale structures and superior mechanical properties, both of which feature functionally gradient variations in the height direction, to improve their ability to resist lodging failure by reducing the maximal stress. The synergistic effect of chiral morphology and reconfiguration can greatly improve the survivability of cattail plants in wind.

Strong Local Chiroptical Response in Racemic Patchy Silver Films: Enabling a Large-Area Chiroptical Device

Ag glancing angle depositions on polycrystalline colloid monolayers can produce a variety of chiral or achiral Ag nanostructures in different colloid monolayer domains, whose geometric shapes strongly depend on the monolayer orientations. The morphological and chiroptical properties of these Ag nanostructures in different colloid monolayer domains are investigated both experimentally and theoretically, and their relationship has been revealed. Extremely strong local circular dichroism is observed for the domains with obviously chiral morphologies. Under the guidance of this individual domain study, large-area chiral metamaterials can be fabricated on the monocrystalline monolayers with strong, uniform, and tunable chiroptical response, which can be potentially developed into optical devices.