Chiral Nanoceramics

Enantioselective Membranes for Pharmaceutical Applications: A Comprehensive Review

In the past decade, significant advances have been made in the field of chiral separation, which is crucial for biological and pharmaceutical applications. Enantioselective membranes have emerged as a promising platform for efficient chiral separation due to their unique properties such as large surface area, tunable pore size, and high selectivity. These membranes are particularly effective in separating enantiomers because of their ability to facilitate selective interactions between the membrane material and chiral molecules. This article provides a comprehensive review of the recent progress in enantioselective membranes for chiral separation. Key topics discussed include various membrane fabrication methods, functionalization approaches, and the characterization of membrane properties, specifically in the context of applications like drug delivery, biomolecule separation, and pharmaceutical analysis. Furthermore, the review addresses the current challenges, potential solutions, and future prospects in this rapidly evolving field, highlighting the direction for upcoming research.

Living Hybrid Exciton Materials: Enhanced Fluorescence and Chiroptical Properties in Living Supramolecular Polymers with Strong Frenkel/Charge-Transfer Exciton Coupling

A family of chiral perylene diimides (PDIs) was newly developed as excellent circularly polarized luminescence (CPL) materials. They are asymmetrically derivatized with a double-alkyl-chained L- or D-glutamate unit and a linear or branched alkyl chain. When water is added to the tetrahydrofuran (THF) solution of glutamate-PDI-linear-alkyl chain compounds, kinetically formed H-aggregates are formed in globular nanoparticles (NPs). These NPs undergo spontaneous transformation into thermodynamically stable nanotubes via helical nanostructures, which showed structured broad spectra originating from the strong coupling of delocalized Frenkel excitations (FE) and charge transfer excitations (CTE). Significant enhancement of circular dichroism (CD), fluorescence quantum yield, and circularly polarized luminescence (CPL) with luminescence dissymmetry factor (glum) are observed during the transformation of NPs to the FE/CTE-coupled helical and tubular structures. This transformation process is significantly accelerated by applying physical stimuli, i.e., ultrasonication or adding helical aggregates as seed crystals, a feature unique to living supramolecular polymerization. Meanwhile, the branched chain-containing PDIs only form H-aggregates and did not show FE/CTE hybrid exciton states with living supramolecular polymerization properties. This study unveils that suitably designed chiral PDI derivatives show FE/CTE coupling accompanied by high fluorescence quantum yields, enhanced chiroptical properties, and supramolecular living polymerization characteristics.

Enantioselective adsorption on chiral ceramics with medium entropy

Chiral metal surfaces provide an environment for enantioselective adsorption in various processes such as asymmetric catalysis, chiral recognition, and separation. However, they often suffer from limitations such as reduced enantioselectivity caused by kink coalescence and atomic roughness. Here, we present an approach using medium-entropy ceramic (MEC), specifically (CrMoTa)Si2 with a C40 hexagonal crystal structure, which overcomes the trade-off between thermal stability and enantioselectivity. Experimental confirmation is provided by employing quartz crystal microbalance (QCM), where the electrode is coated with MEC films using non-reactive magnetron sputtering technology. The chiral nature is verified through transmission electron microscopy and circular dichroism. Density-functional theory (DFT) calculations show that the stability of MEC films is significantly higher than that of high-index Cu surfaces. Through a combination of high-throughput DFT calculations and theoretical modeling, we demonstrate the high enantioselectivity (42% e.e.) of the chiral MEC for serine, a prototype molecule for studying enantioselective adsorption. The QCM results show that the adsorption amount of L-serine is 1.58 times higher than that of D-serine within a concentration range of 0-60 mM. These findings demonstrate the potential application of MECs in chiral recognition.

A Family of Twisted Chiral Engineered Inorganic Nanoarchitectures

Chiral inorganic materials possess unique asymmetric properties that could significantly impact various fields. However, their practical application has been hindered by challenges in creating structurally robust chiral materials. We report the synthesis of well-defined chiral-shaped hollow cobalt oxide nanostructures, extendable to a family of chalcogenides including sulfide, selenide, and telluride through topological transformations. Taking chiral cobalt oxide nanostructures as a representative material, we demonstrate precise control over their chiral architectures, enabling fine-tuning of parameters, such as twist degrees, handedness, and compositions. These chiral nanostructures exhibit high spin selectivity effects that influence the electron transfer processes in catalytic reactions. Leveraging this spin-selective behavior, the chiral cobalt oxide nanoarchitectures demonstrate enhanced electrocatalytic performance in the oxygen evolution reaction compared to their achiral counterparts. Our findings not only expand the library of chiral inorganic materials but also advance the application of chiral effects in fields such as catalysis, spintronics, and beyond.

Topology of Gemini-shaped Hexagonal Heterojunction for Efficient Stereoconvergent Transformation via Dynamic Kinetic Resolution

Despite recent advances in the combination of kinetic resolution and racemization for efficient stereoconvergent transformation, the poor stability and limited reaction activities of the products restrict their wide application in industrial production. To overcome these problems, Gemini-shaped hexagons with para-heterojunctions for one-dimensional and two-dimensional supramolecular polymers were designed via hydrogen-bonding adhesion by racemization catalyst 1 and kinetic resolution 2 in this work. The polymers from the assembly of Gemini-shaped hexagons exhibit rapid catalytic behaviour with efficient selectivity for the desired configuration in the synthesis of tertiary alcohols with contiguous stereocenters through dynamic kinetic resolution for the nanoscale heterojunctions of dissimilar catalysts. Among them, the developed 2D polymers gave outstanding enantioselectivities and diastereoselectivities (>99 % ee, 20 : 1 dr) through the cooperation of adjacent dissimilar catalysts. The heterojunctions varying dimensions and distances of dissimilar catalysts provide new insight for increasing the enantioselectivity of chiral organocatalysts.

Synthesis of chiral graphene structures and their comprehensive applications: a critical review

From a molecular viewpoint, chirality is a crucial factor in biological processes. Enantiomers of a molecule have identical chemical and physical properties, but chiral molecules found in species exist in one enantiomer form throughout life, growth, and evolution. Chiral graphene materials have considerable potential for application in various domains because of their unique structural framework, properties, and controlled synthesis, including chiral creation, segregation, and transmission. This review article provides an in-depth analysis of the synthesis of chiral graphene materials reported over the past decade, including chiral nanoribbons, chiral tunneling, chiral dichroism, chiral recognition, and chiral transfer. The second segment focuses on the diverse applications of chiral graphene in biological engineering, electrochemical sensors, and photodetectors. Finally, we discuss research challenges and potential future uses, along with probable outcomes.

Macroscopic homochiral helicoids self-assembled via screw dislocations

Chirality is a fundamental property in nature and is widely observed at hierarchical scales from subatomic, molecular, supramolecular to macroscopic and even galaxy. However, the transmission of chirality across different length scales and the expression of homochiral nano/microstructures remain challenging. Herein, we report the formation of macroscopic homochiral helicoids with ten micrometers from enantiomeric pyromellitic diimide-based molecular triangle (PMDI-Δ) and achiral pyrene via a screw dislocation-driven co-self-assembly. Chiral transfer and expression from molecular and supramolecular levels, to the macroscopic helicoids, is continuous and follows the molecular chirality of PMDI-Δ. Furthermore, the screw dislocation and chirality transfer lead to a unidirectional curvature of the helicoids, which exhibit excellent circularly polarized luminescence with large |glum| values up to 0.05. Our results demonstrate the formation of a homochiral macroscopic organic helicoid and function emergence from small molecules via screw dislocations, which deepens our understanding of chiral transfer and expression across different length scales.

Direct Readout of Homo- vs Heterochiral Ligand Shell of Quantum Dots

The chiroptical activity of various semiconductor inorganic nanocrystalline materials has typically been tested using circular dichroism or circularly polarized luminescence. Herein, we report on a high-throughput screening method for identifying and differentiating chiroptically active quantum-sized ZnO crystals using Raman spectroscopy combined with principal component analysis. ZnO quantum dots (QDs) coated by structurally diverse homo- and heterochiral aminoalcoholate ligands (cis- and trans-1-amino-2-indanolate, 2-amino-1-phenylethanolate, and diphenyl-2-pyrrolidinemethanolate) were prepared using the one-pot self-supporting organometallic procedure and then extensively studied toward the identification of specific Raman fingerprints and spectral variations. The direct comparison between the spectra demonstrates that it is very difficult to make definite recognition and identification between QDs coated with enantiomers based only on the differences in the respective Raman bands' position shifts and their intensities. However, the applied approach involving the principal component analysis performed on the Raman spectra allows the simultaneous differentiation and identification of the studied QDs. The first and second principal components explain 98, 97, 97, and 87% of the variability among the studied families of QDs and demonstrate the possibility of using the presented method as a qualitative assay. Thus, the reported multivariate approach paves the way for simultaneous differentiation and identification of chirotopically active semiconductor nanocrystals.

Biomimetic Chiral Nanomaterials with Selective Catalysis Activity

Chiral nanomaterials with unique chiral configurations and biocompatible ligands have been booming over the past decade for their interesting chiroptical effect, unique catalytical activity, and related bioapplications. The catalytic activity and selectivity of chiral nanomaterials have emerged as important topics, that can be potentially controlled and optimized by the rational biochemical design of nanomaterials. In this review, chiral nanomaterials synthesis, composition, and catalytic performances of different biohybrid chiral nanomaterials are discussed. The construction of chiral nanomaterials with multiscale chiral geometries along with the underlying principles for enhancing chiroptical responses are highlighted. Various biochemical approaches to regulate the selectivity and catalytic activity of chiral nanomaterials for biocatalysis are also summarized. Furthermore, attention is paid to specific chiral ligands, materials compositions, structure characteristics, and so on for introducing selective catalytic activities of representative chiral nanomaterials, with emphasis on substrates including small molecules, biological macromolecule, and in-site catalysis in living systems. Promising progress has also been emphasized in chiral nanomaterials featuring structural versatility and improved chiral responses that gave rise to unprecedented chances to utilize light for biocatalytic applications. In summary, the challenges, future trends, and prospects associated with chiral nanomaterials for catalysis are comprehensively proposed.

Modulation by Co (II) Ion of Optical Activities of L/D-glutathione (GSH)-modified Chiral Copper Nanoclusters for Sensitive Adenosine Triphosphate Detection

Chiral nanoscale enantiomers exhibit different biological effects in living systems. However, their chirality effect on the detection sensitivity for chiral biological targets still needs to be explored. Here, we discovered that Co2+ can modulate the luminescence performance of L/D-glutathione (GSH)-modified copper nanoclusters (L/D-Cu NCs) and induce strong chiroptical activities as the asymmetric factor was enhanced 223-fold with their distribution regulating from the ultraviolet to visible region. One Co2+ coordinated with two GSH molecules that modified on the surface of Cu NCs in the way of CoN2O2. On this basis, dual-modal chiral and luminescent signals of Co2+ coordinated L/D-Cu NCs (L/D-Co-Cu NCs) were used to detect the chiral adenosine triphosphate (ATP) based on the competitive interaction between surficial GSH and ATP molecules with Co2+. The limits of detection of ATP obtained with fluorescence and circular dichroism intensity were 9.15 μM and 15.75 nM for L-Co-Cu NCs, and 5.35 μM and 4.69 nM for D-Co-Cu NCs. This demonstrated that selecting suitable chiral configurations of nanoprobes effectively enhances detection sensitivity. This study presents not only a novel method to modulate and enhance the chiroptical activity of nanomaterials but also a unique perspective of chirality effects on the detection performances for bio-targets.

Circularly polarized luminescence in quantum dot-based materials

Quantum dots (QDs) have emerged as fantastic luminescent nanomaterials with significant potential due to their unique photoluminescence properties. With the rapid development of circularly polarized luminescence (CPL) materials, many researchers have associated QDs with the CPL property, resulting in numerous novel CPL-active QD-containing materials in recent years. The present work reviews the latest advances in CPL-active QD-based materials, which are classified based on the types of QDs, including perovskite QDs, carbon dots, and colloidal semiconductor QDs. The applications of CPL-active QD-based materials in biological, optoelectronic, and anti-counterfeiting fields are also discussed. Additionally, the current challenges and future perspectives in this field are summarized. This review article is expected to stimulate more unprecedented achievements based on CPL-active QD-based materials, thus further promoting their future practical applications.

One-Step Electrochemical Synthesis of Multiyolk-Shell Nanocoils for Exceptional Photocatalytic Performance

Multiyolk-shell (mYS) nanostructures have garnered significant interest in various photocatalysis applications such as water splitting and waste treatment. Nonetheless, the complexity and rigorous conditions for the synthesis have hindered their widespread implementation. This study presents a one-step electrochemical strategy for synthesizing multiyolk-shell nanocoils (mYSNC), wherein multiple cores of noble metal nanoparticles, such as Au, are embedded within the hollow coil-shaped FePO4 shell structures, mitigating the challenges posed by conventional methods. By capitalizing on the dissimilar dissolution rates of bimetallic alloy nanocoils in an electrochemically programmed solution, nanocoils of different shapes and materials, including two variations of mYSNCs are successfully fabricated. The resulting Au-FePO4 mYSNCs exhibit exceptional photocatalytic performance for environmental remediation, demonstrating up to 99% degradation of methylene blue molecules within 50 min and 95% degradation of tetracycline within 100 min under ultraviolet-visible (UV-vis) light source. This remarkable performance can be attributed to the abundant electrochemical active sites, internal voids facilitating efficient light harvesting with coil morphology, amplified localized surface plasmon resonance (LSPR) at the plasmonic nanoparticle-semiconductor interface, and effective band engineering. The innovative approach utilizing bimetallic alloys demonstrates precise geometric control and design of intricate multicomponent hybrid composites, showcasing the potential for developing versatile hollow nanomaterials for catalytic applications.

Chiral Induced Spin Selectivity

Since the initial landmark study on the chiral induced spin selectivity (CISS) effect in 1999, considerable experimental and theoretical efforts have been made to understand the physical underpinnings and mechanistic features of this interesting phenomenon. As first formulated, the CISS effect refers to the innate ability of chiral materials to act as spin filters for electron transport; however, more recent experiments demonstrate that displacement currents arising from charge polarization of chiral molecules lead to spin polarization without the need for net charge flow. With its identification of a fundamental connection between chiral symmetry and electron spin in molecules and materials, CISS promises profound and ubiquitous implications for existing technologies and new approaches to answering age old questions, such as the homochiral nature of life. This review begins with a discussion of the different methods for measuring CISS and then provides a comprehensive overview of molecules and materials known to exhibit CISS-based phenomena before proceeding to identify structure-property relations and to delineate the leading theoretical models for the CISS effect. Next, it identifies some implications of CISS in physics, chemistry, and biology. The discussion ends with a critical assessment of the CISS field and some comments on its future outlook.

Sensitive and Selective Dual-Mode Responses to Reactive Oxygen Species by Chiral Manganese Dioxide Nanoparticles for Antiaging Skin

Excessive accumulation of reactive oxygen species (ROS) can lead to oxidative stress and oxidative damage, which is one of the important factors for aging and age-related diseases. Therefore, real-time monitoring and the moderate elimination of ROS is extremely important. In this study, a ROS-responsive circular dichroic (CD) at 553 nm and magnetic resonance imaging (MRI) dual-signals chiral manganese oxide (MnO2 ) nanoparticles (NPs) are designed and synthesized. Both the CD and MRI signals show excellent linear ranges for intracellular hydrogen peroxide (H2 O2 ) concentrations, with limits of detection (LOD) of 0.0027 nmol/106 cells and 0.016 nmol/106 cells, respectively. The lower LOD achieved with CD detection may be attributable to its higher anti-interference capability from the intracellular matrix. Importantly, ROS-induced cell aging is intervened by chiral MnO2 NPs via redox reactions with excessive intracellular ROS. In vivo experiments confirm that chiral MnO2 NPs effectively eliminate ROS in skin tissue, reduce oxidative stress levels, and alleviate skin aging. This approach provides a new strategy for the diagnosis and treatment of age-related diseases.

Chirality in Atomically Thin CdSe Nanoplatelets Capped with Thiol-Free Amino Acid Ligands: Circular Dichroism vs. Carboxylate Group Coordination

Chiral semiconductor nanostructures and nanoparticles are promising materials for applications in biological sensing, enantioselective separation, photonics, and spin-polarized devices. Here, we studied the induction of chirality in atomically thin only two-monolayer-thick CdSe nanoplatelets (NPLs) grown using a colloidal method and exchanged with L-alanine and L-phenylalanine as model thiol-free chiral ligands. We have developed a novel two-step approach to completely exchange the native oleic acid ligands for chiral amino acids at the basal planes of NPLs. We performed an analysis of the optical and chiroptical properties of the chiral CdSe nanoplatelets with amino acids, which was supplemented by an analysis of the composition and coordination of ligands. After the exchange, the nanoplatelets retained heavy-hole, light-hole, and spin-orbit split-off exciton absorbance and bright heavy-hole exciton luminescence. Capping with thiol-free enantiomer amino acid ligands induced the pronounced chirality of excitons in the nanoplatelets, as proven by circular dichroism spectroscopy, with a high dissymmetry g-factor of up to 3.4 × 10-3 achieved for heavy-hole excitons in the case of L-phenylalanine.

Chiral Mesostructured Inorganic Materials with Optical Chiral Response

Fabricating chiral inorganic materials and revealing their unique quantum confinement-determined optical chiral responses are crucial tasks in the multidisciplinary fields of chemistry, physics, and biology. The field of chiral mesostructured inorganic materials started from the synthesis of individual nanocrystals and evolved to include their assembly from metals, semiconductors, ceramics, and inorganic salts endowed with various chiral structures ranging from atomic to micron scales. This tutorial review highlights the recent research on chiral mesostructured inorganic materials, especially the novel expression of mesostructured chirality and endowed optical chiral response, and it may inspire us with new strategies for the design of chiral inorganic materials and new opportunities beyond the traditional applications of chirality. Fabrication methods for chiral mesostructured inorganic materials are classified according to chirality type, scale, and symmetry-breaking mechanism. Special attention is given to highlight systems with original discoveries, exceptional phenomena, or unique mechanisms of optical chiral response for left- and right-handedness.

Chiral Confined Unimolecular Micelles for Controlled In Situ Fabrication of Optically Active Hybrid Nanostructures

Functional nanomaterials made by chiral induction have attracted extensive attention because of their intriguing characteristics and potential applications. However, the precise and controllable fabrication of chiral nanomaterials still remains challenging but is highly desired. In this study, chiral unimolecular micelles with different molecular weights and chiroptical activities were prepared by photoinduced atom transfer radical polymerization (photoATRP). Through nanoconfined growth, the chiral plasmonic nanoparticle assemblies with predesigned size and morphology were prepared using chiral unimolecular micelles as nanoreactors. The controllability over chiral assemblies and the size effect on chiroptical properties were also investigated. Furthermore, chiral complexes with absorption asymmetry and circularly polarized luminescence (glum = 4.25 × 10-4) were easily constructed via mixing of organic fluorescent molecules and chiral templates based on intermolecular hydrogen bonds. Such results indicated that our unimolecular-micelle-based templates enable the controllable preparation of both inorganic and organic chiral nanostructures with tailored dimensions, sizes, compositions, and optical activities.

Chiral Inorganic Nanomaterials for Photo(electro)catalytic Conversion

Chiral inorganic nanomaterials due to their unique asymmetric nanostructures have gradually demonstrated intriguing chirality-dependent performance in photo(electro)catalytic conversion, such as water splitting. However, understanding the correlation between chiral inorganic characteristics and the photo(electro)catalytic process remains challenging. In this perspective, we first highlight the chirality source of inorganic nanomaterials and briefly introduce photo(electro)catalysis systems. Then, we delve into an in-depth discussion of chiral effects exerted by chiral nanostructures and their photo-electrochemistry properties, while emphasizing the emerging chiral inorganic nanomaterials for photo(electro)catalytic conversion. Finally, the challenges and opportunities of chiral inorganic nanomaterials for photo(electro)catalytic conversion are prospected. This perspective provides a comprehensive overview of chiral inorganic nanomaterials and their potential in photo(electro)catalytic conversion, which is beneficial for further research in this area.

Chiral Materials: Progress, Applications, and Prospects

Chirality is a universal phenomenon in molecular and biological systems, denoting an asymmetric configurational property where an object cannot be superimposed onto its mirror image by any kind of translation or rotation, which is ubiquitous on the scale from neutrinos to spiral galaxies. Chirality plays a very important role in the life system. Many biological molecules in the life body show chirality, such as the "codebook" of the earth's biological diversity-DNA, nucleic acid, etc. Intriguingly, living organisms hierarchically consist of homochiral building blocks, for example, l-amino acids and d-sugars with unknown reason. When molecules with chirality interact with these chiral factors, only one conformation favors the positive development of life, that is, the chiral host environment can only selectively interact with chiral molecules of one of the conformations. The differences in chiral interactions are often manifested by chiral recognition, mutual matching, and interactions with chiral molecules, which means that the stereoselectivity of chiral molecules can produce changes in pharmacodynamics and pathology. Here, the latest investigations are summarized including the construction and applications of chiral materials based on natural small molecules as chiral source, natural biomacromolecules as chiral sources, and the material synthesized by design as a chiral source.

Structurally Induced Chirality of an Achiral Chromophore on Self-Assembled Nanofibers: A Twist Makes It Chiral

The surface domains of self-assembled amphiphiles are well-organized and can perform many physical, chemical, and biological functions. Here, we present the significance of chiral surface domains of these self-assemblies in transferring chirality to achiral chromophores. These aspects are probed using l- and d-isomers of alkyl alanine amphiphiles which self-assemble in water as nanofibers, possessing a negative surface charge. When bound on these nanofibers, positively charged cyanine dyes (CY524 and CY600), each having two quinoline rings bridged by conjugated double bonds, show contrasting chiroptical features. Interestingly, CY600 displays a bisignated circular dichroic (CD) signal with mirror-image symmetry, while CY524 is CD silent. Molecular dynamics simulations reveal that the model cylindrical micelles (CM) derived from the two isomers exhibit surface chirality and the chromophores are buried as monomers in mirror-imaged pockets on their surfaces. The monomeric nature of template-bound chromophores and their binding reversibility are established by concentration- and temperature-dependent spectroscopies and calorimetry. On the CM, CY524 displays two equally populated conformers with opposite sense, whereas CY600 is present as two pairs of twisted conformers in each of which one is in excess, due to differences in weak dye-amphiphile hydrogen bonding interactions. Infrared and NMR spectroscopies support these findings. Reduction of electronic conjugation caused by the twist establishes the two quinoline rings as independent entities. On-resonance coupling between the transition dipoles of these units generates bisignated CD signals with mirror-image symmetry. The results presented herein provide insight on the little-known structurally induced chirality of achiral chromophores through transfer of chiral surface information.

Block Copolymer Enabled Synthesis and Assembly of Chiral Metal Oxide Nanoparticle

Chiral metal oxide nanostructures have received tremendous attention in nanotechnological applications owing to their intriguing chiroptical and magnetic properties. Current synthetic methods mostly rely on the use of amino acids or peptides as chiral inducers. Here, we report a general approach to fabricate chiral metal oxide nanostructures with tunable magneto-chiral effects, using block copolymer (BCP) inverse micelle and R/S-mandelic acid (MA). Diverse chiral metal oxide nanostructures are prepared by the selective incorporation of precursors within micellar cores followed by the oxidation process, exhibiting intense chiroptical properties with a g-factor up to 7.0 × 10^-3 in the visible-NIR range for the Cr₂O₃ nanoparticle multilayer. The BCP inverse micelle is found to inhibit the racemization of MA, allowing MA to act as a chiral dopant that imparts chirality to nanostructures via hierarchical chirality transfer. Notably, for paramagnetic nanostructures, magneto-chiroptical modulation is realized by regulating the direction of the external magnetic field. This BCP-driven approach can be extended to the mass production of chiral nanostructures with tunable architectures and optical activities, which may provide insights into the development of chiroptical functional materials.

Chiral zinc oxide functionalized quartz crystal microbalance sensor for enantioselective recognition of amino acids

Chiral transition metal oxides with tunable structures and multiple physicochemical features have been increasingly applied for chiral sensing and detection. In this work, chiral zinc oxide (ZnO) was first applied as selector to construct quartz crystal microbalance (QCM) sensor for enantioselective recognition of amino acids. The chiral ZnO was prepared by a methionine-induced self-assembly strategy and its high topological chirality was confirmed by several techniques such as circular dichroism spectrum. The chiral discrimination factors were calculated by frequency shifts in response to aspartic acid, phenylalanine, lysine and arginine on L-ZnO surface, achieving 1.89 ± 0.04, 1.76 ± 0.11, 1.66 ± 0.07 and 1.54 ± 0.09, respectively. Notably, L-enantiomers preferred stronger absorptions on L-ZnO surface as compared to D-forms. It was further found that this sensor was appropriate for quantitative analysis and enantiomer excess analysis and adsorption kinetics study. Furthermore, molecular docking revealed the recognition mechanism, where chiral distinction was caused by the different steric interactions between enantiomers and chiral ZnO. This method enjoyed merits of high enantioselectivity, simple preparation and low cost, offering newly chiral sensing method for other molecules.

Histidine-Mediated Synthesis of Chiral Cobalt Oxide Nanoparticles for Enantiomeric Discrimination and Quantification

Chiral transition metal oxide nanoparticles (CTMOs) are attracting a lot of attention due to their fascinating properties. Nevertheless, elucidating the chirality induction mechanism often remains a major challenge. Herein, the synthesis of chiral cobalt oxide nanoparticles mediated by histidine (Co₃ O₄ @L-His and Co₃ O₄ @D-His for nanoparticles synthesized in the presence of L- and D-histidine, respectively) is investigated. Interestingly, these CTMOs exhibit remarkable and tunable chiroptical properties. Their analysis by x-ray photoelectron, Fourier transform infrared, and ultraviolet-visible absorption spectroscopy indicates that the ratio of Co²⁺ /Co³⁺ and their interactions with the imidazole groups of histidine are behind their chiral properties. In addition, the use of chiral Co₃ O₄ nanoparticles for the development of sensitive, rapid, and enantioselective circular dichroism-based sensors is demonstrated, allowing direct molecular detection and discrimination between cysteine or penicillamine enantiomers. The circular dichroism response of the chiral Co₃ O₄ exhibits a limit of detection and discrimination of cysteine and penicillamine enantiomers as low as 10 µm. Theoretical calculations suggest that the ligand exchange and the coexistence of both species adsorbed on the oxide surface are responsible for the enantiomeric discrimination. This research will enrich the synthetic approaches to obtain CTMOs and enable the extension of the applications and the discovery of new chiroptical properties.

Polarization-directed growth of spiral nanostructures by laser direct writing with vector beams

Chirality is pivotal in nature which attracts wide research interests from all disciplines and creating chiral matter is one of the central themes for chemists and material scientists. Despite of significant efforts, a simple, cost-effective and general method that can produce different kinds of chiral metamaterials with high regularity and tailorability is still demanding but greatly missing. Here, we introduce polarization-directed growth of spiral nanostructures via vector beams, which is simple, tailorable and generally applicable to both plasmonic and dielectric materials. The self-aligned near field enhances the photochemical growth along the polarization, which is crucial for the oriented growth. The obtained plasmonic chiral nanostructures present prominent optical activity with a g-factor up to 0.4, which can be tuned by adjusting the spirality of the vector beams. These spiral plasmonic nanostructures can be used for the sensing of different chiral enantiomers. The dielectric chiral metasurfaces can also be formed in arrays of sub-mm scale, which exhibit a g-factor over 0.1. However, photoluminescence of chiral cadmium sulfide presents a very weak luminescence g-factor with the excitation of linearly polarized light. A number of applications can be envisioned with these chiral nanostructures such as chiral sensing, chiral separation and chiral information storage.

Multimodal-Responsive Circularly Polarized Luminescence Security Materials

Nations, industries, and aspects of everyday life have undergone forgery and counterfeiting ever since the emergence of commercialization. Securing documents and products with anticounterfeit additives shows promise for authentication, allowing one to combat ever-increasing global counterfeiting. One most-used effective encryption strategy is to combine with optical-security markers on the required protection objects; however, state-of-the-art labels still suffer from imitation due to their poor complexity and easy forecasting, as a result of deterministic production. Developing advanced anticounterfeiting tags with unusual optical characters and further incorporating complex security features are desired to achieve multimodal, unbreakable authentication capacity; unfortunately, this has not yet been achieved. Here, we prepare a series of stable circularly polarized luminescence (CPL) materials, composed of toxicity-free, high-quality-emitting inorganic quantum dots (QDs) and liquid crystals, using a designed helical-coassembly strategy. This CPL system achieves a figure of merit (FM, assessing the performance of both luminescence dissymmetry and quantum yield) value of 0.39, fulfilling practical demands for anticounterfeiting applications. Based on these CPL structures, we produce a type of multimodal-responsive security materials (MRSMs) that exhibits six different stimuli-responsive modes, including light activation, polarization, temperature, voltage, pressure, and view angle. Thus, we show a proof-of-principle blockchain-like integrated anticounterfeiting system, allowing multimodal-responsive, interactive/changeable information encryption-decryption. We further encapsulate the obtained security materials into a fiber to expand our materials to work on flexible fabrics, that is, building an intelligent textile with a color-adaptable function along with environmental change.

Chiral Seeded Growth of Gold Nanorods Into Fourfold Twisted Nanoparticles with Plasmonic Optical Activity

A robust and reproducible methodology to prepare stable inorganic nanoparticles with chiral morphology may hold the key to the practical utilization of these materials. An optimized chiral growth method to prepare fourfold twisted gold nanorods is described herein, where the amino acid cysteine is used as a dissymmetry inducer. Four tilted ridges are found to develop on the surface of single-crystal nanorods upon repeated reduction of HAuCl4 , in the presence of cysteine as the chiral inducer and ascorbic acid as a reducing agent. From detailed electron microscopy analysis of the crystallographic structures, it is proposed that the dissymmetry results from the development of chiral facets in the form of protrusions (tilted ridges) on the initial nanorods, eventually leading to a twisted shape. The role of cysteine is attributed to assisting enantioselective facet evolution, which is supported by density functional theory simulations of the surface energies, modified upon adsorption of the chiral molecule. The development of R-type and S-type chiral structures (small facets, terraces, or kinks) would thus be non-equal, removing the mirror symmetry of the Au NR and in turn resulting in a markedly chiral morphology with high plasmonic optical activity.

Liquid crystal-templated chiral nanomaterials: from chiral plasmonics to circularly polarized luminescence

Chiral nanomaterials with intrinsic chirality or spatial asymmetry at the nanoscale are currently in the limelight of both fundamental research and diverse important technological applications due to their unprecedented physicochemical characteristics such as intense light-matter interactions, enhanced circular dichroism, and strong circularly polarized luminescence. Herein, we provide a comprehensive overview of the state-of-the-art advances in liquid crystal-templated chiral nanomaterials. The chiroptical properties of chiral nanomaterials are touched, and their fundamental design principles and bottom-up synthesis strategies are discussed. Different chiral functional nanomaterials based on liquid-crystalline soft templates, including chiral plasmonic nanomaterials and chiral luminescent nanomaterials, are systematically introduced, and their underlying mechanisms, properties, and potential applications are emphasized. This review concludes with a perspective on the emerging applications, challenges, and future opportunities of such fascinating chiral nanomaterials. This review can not only deepen our understanding of the fundamentals of soft-matter chirality, but also shine light on the development of advanced chiral functional nanomaterials toward their versatile applications in optics, biology, catalysis, electronics, and beyond.

Biological applications of chiral inorganic nanomaterials

Chirality is common in nature and plays the essential role in maintaining physiological process. Chiral inorganic nanomaterials with intense optical activity have attracted more attention due to amazing properties in recent years. Over the past decades, many efforts have been paid to the preparation and chirality origin of chiral nanomaterials; furthermore, emerging biological applications have been investigated widely. This review mainly summarizes recent advances in chiral nanomaterials. The top-down and bottom-up preparation methods and chirality origin of chiral nanomaterials are introduced; besides, the biological applications, such as sensing, therapy, and catalysis, will be introduced comprehensively. Finally, we also provide a perspective on the biomedical applications of chiral nanomaterials.

Authentic Intelligent Machine for Scaling Driven Discovery: A Case for Chiral Quantum Dots

The scaling laws have long been used as evidence of science where many fundamental physics laws emerge. As emerging nanomaterials, quantum dots are also sensitive to scaling because of their strong size effect. In this work, we developed the chiral dielectric theory based on the exciton absorption mechanism to explain the increment of the dielectric constant from chirality via its dimensionality. To help researchers discover and develop scaling relevant theories, the Authentic Intelligent Machine (AIM) protocol was developed to generate and interpret experimental data in an analytical and scaling-oriented manner. We show how the AIM protocol interprets spectra such as transient absorption data of chiral quantum dots with theories, where discrepancies concerning the dielectric constant were discovered. Examples for applying the AIM protocol on other spectra, such as absorption spectra and photoluminescence spectra, are also given.

Selectively Regulating the Chiral Morphology of Amino Acid-Assisted Chiral Gold Nanoparticles with Circularly Polarized Light

Chiral nanomaterials have attracted increasing attention due to their versatile optical properties. Although circularly polarized (CP) light can serve as an inducer, it has negligible effects because of the short lifetime of the plasmonic states. Here, we propose that the site-selective chirality regulation on the morphology of cysteine (cys) amino acid-assisted chiral gold nanoparticles (cys-chiral AuNPs) can be realized through CP light irradiation. This can result in the increased or decreased circular dichroism (CD) signal intensity. The site-selective growth mechanism of the cys-chiral AuNPs is elucidated with light-matter interactions through the opposite rotation of right(R)/left(L) CP light. The site-selective chirality growth of the cys-chiral AuNPs is ascribed to the morphology evolution induced by the synergy of cys and R/L-CP light, which is clearly analyzed and elucidated with high CD intensities. This work provides a promising alternative strategy to produce high-chirality nanomaterials that can be applied in biomedicine and enantiomer photocatalytic reaction.

Self-assembled inorganic chiral superstructures

Controlled assembly of inorganic nanoparticles with different compositions, sizes and shapes into higher-order structures of collective functionalities is a central pursued objective in chemistry, physics, materials science and nanotechnology. The emerging chiral superstructures, which break spatial symmetries at the nanoscale, have attracted particular attention, owing to their unique chiroptical properties and potential applications in optics, catalysis, biology and so on. Various bottom-up strategies have been developed to build inorganic chiral superstructures based on the intrinsic configurational preference of the building blocks, external fields or chiral templates. Self-assembled inorganic chiral superstructures have demonstrated significant superior optical activity from the strong electric/magnetic coupling between the building blocks, as compared with the organic counterparts. In this Review, we discuss recent progress in preparing self-assembled inorganic chiral superstructures, with an emphasis on the driving forces that enable symmetry breaking during the assembly process. The chiroptical properties and applications are highlighted and a forward-looking trajectory of where research efforts should be focused is discussed.

Recent Advances in Inorganic Chiral Nanomaterials

Inorganic nanoparticles offer a multifunctional platform for biomedical applications in drug delivery, biosensing, bioimaging, disease diagnosis, screening, and therapies. Homochirality prevalently exists in biological systems composed of asymmetric biochemical activities and processes, so biomedical applications essentially favor the usage of inorganic chiral nanomaterials, which have been widely studied in the past two decades. Here, the latest investigations are summarized including the characterization of 3D stereochirality, the bionic fabrication of hierarchical chirality, extension of the compositional space to poly-elements, studying optical activities with the (sub-)single-particle resolution, and the experimental demonstration in biomedical applications. These advanced studies pave the way toward fully understanding the two important chiral effects (i.e., the chiroptical and enantioselective effects), and prospectively promote the flexible design and fabrication of inorganic chiral nanoparticles with engineerable functionalities to solve diverse practical problems closely associated with environment and public health.

Chiral Magneto-Optical Properties of Supra-Assembled Fe3O4 Nanoparticles

Research on the chiral magneto-optical properties of inorganic nanomaterials has enabled novel applications in advanced optical and electronic devices. However, the corresponding chiral magneto-optical responses have only been studied under strong magnetic fields of ≥1 T, which limits the wider application of these novel materials. In this paper, we report on the enhanced chiral magneto-optical activity of supra-assembled Fe₃O₄ magnetite nanoparticles in the visible range at weak magnetic fields of 1.5 mT. The spherical supra-assembled particles with a diameter of ∼90 nm prepared by solvothermal synthesis had single-crystal-like structures, which resulted from the oriented attachment of nanograins. They exhibited superparamagnetic behavior even with a relatively large supraparticle diameter that exceeded the size limit for superparamagnetism. This can be attributed to the small size of nanograins with a diameter of ∼12 nm that constitute the suprastructured particles. Magnetic circular dichroism (MCD) measurements at magnetic fields of 1.5 mT showed distinct chiral magneto-optical activity from charge transfer transitions of magnetite in the visible range. For the supraparticles with lower crystallinity, the MCD peaks in the 250-550 nm range assigned as the ligand-to-metal charge transfer (LMCT) and the inter-sublattice charge transfer (ISCT) show increased intensities in comparison to those with higher crystallinity samples. On the contrary, the higher crystallinity sample shows higher MCD intensities near 600-700 nm for the intervalence charge transfer (IVCT) transition. The differences in MCD responses can be attributed to the crystallinity determined by the reaction time, lattice distortion near grain boundaries of the constituent nanocrystals, and dipolar interactions in the supra-assembled structures.

Inorganic Hollow Nanocoils Fabricated by Controlled Interfacial Reaction and Their Electrocatalytic Properties

The fabrication of 3D hollow nanostructures not only allows the tactical provision of specific physicochemical properties but also broadens the application scope of such materials in various fields. The synthesis of 3D hollow nanocoils (HNCs), however, is limited by the lack of an appropriate template or synthesis method, thereby restricting the wide-scale application of HNCs. Herein, a strategy for preparing HNCs by harnessing a single sacrificial template to modulate the interfacial reaction at a solid-liquid interface that allows the shape-regulated transition is studied. Furthermore, the triggering of the Kirkendall effect in 3D HNCs is demonstrated. Depending on the final state of the transition metal ions reduced during the electrochemical preparation of HNCs, the surface states of the binding anions and the composition of the HNCs can be tuned. In a single-component CrPO₄ HNC with a clean surface, the Kirkendall effect of the coil shape is analyzed at various points throughout the reaction. The rough-surface multicomponent MnO_x P_0.21 HNCs are complexed with ligand-modified BF₄ -Mn₃ O₄ nanoparticles. The fabricated nanocomposite exhibits an overpotential decrease of 25 mV at neutral pH compared to pure BF₄ -Mn₃ O₄ nanoparticles because of the increased active surface area.

Chirality Affecting Reaction Dynamics of HgS Nanostructures Simultaneously Visualized in Real and Reciprocal Space

Chirality involved reactions enable to probe features in the fields of asymmetric synthesis and catalysis, which allow to gain insight into the fundamental mechanisms of topochemically controlled reactions. However, in situ observation of the chirality-associated reaction dynamics with simultaneous structural determination of microscopic features has been lacking. Here, we report the direct visualization of the electron-beam-stimulated reaction dynamics of HgS nanostructures with chiral and achiral morphologies simultaneously in both real and reciprocal space. Under the electron-beam excitation of HgS nanostructures, the formation and evaporation dynamics of Hg nanodroplets were vividly pictured, while the reciprocal space imaging revealed the structural transformation from monocrystalline to polycrystalline. Interestingly, such induced changes were size dependent, which were slowed when involving the chirality in the nanostructures. The finding offers a fundamental understanding of topochemically controlled reaction mechanisms and holds promise of tuning asymmetric synthesis for catalysis-related applications.

Shining light on chiral inorganic nanomaterials for biological issues

The rapid development of chiral inorganic nanostructures has greatly expanded from intrinsically chiral nanoparticles to more sophisticated assemblies made by organics, metals, semiconductors, and their hybrids. Among them, lots of studies concerning on hybrid complex of chiral molecules with achiral nanoparticles (NPs) and superstructures with chiral configurations were accordingly conducted due to the great advances such as highly enhanced biocompatibility with low cytotoxicity and enhanced penetration and retention capability, programmable surface functionality with engineerable building blocks, and more importantly tunable chirality in a controlled manner, leading to revolutionary designs of new biomaterials for synergistic cancer therapy, control of enantiomeric enzymatic reactions, integration of metabolism and pathology via bio-to nano or structural chirality. Herein, in this review our objective is to emphasize current research state and clinical applications of chiral nanomaterials in biological systems with special attentions to chiral metal- or semiconductor-based nanostructures in terms of the basic synthesis, related circular dichroism effects at optical frequencies, mechanisms of induced optical chirality and their performances in biomedical applications such as phototherapy, bio-imaging, neurodegenerative diseases, gene editing, cellular activity and sensing of biomarkers so as to provide insights into this fascinating field for peer researchers.

Sequential Symmetry-Breaking Events as a Synthetic Pathway for Chiral Gold Nanostructures with Spiral Geometries

Symmetry-breaking synthetic controls allow for nanostructure geometries that are counter to the underlying crystal symmetry of a material. If suitably applied, such controls provide the means to drive an isotropic metal along a growth pathway yielding a three-dimensional chiral geometry. Herein, we present a light-driven solution-based synthesis yielding helical gold spirals from substrate-bound seeds. The devised growth mode relies on three separate symmetry-breaking events ushered in by seeds lined with planar defects, a capping agent that severely frustrates early stage growth, and the Coulombic repulsion that occurs when identically charged growth fronts collide. Together they combine to advance a growth pathway in which planar growth emanates from one side of the seed, advances to encircle the seed from both clockwise and counterclockwise directions, and then, upon collision of the two growth fronts, sees one front rise above the other to realize a self-perpetuating three-dimensional spiral structure.

Self-Assembled Chiral Phosphorescent Microflowers from Au Nanoclusters with Dual-Mode pH Sensing and Information Encryption

The self-assembly of chiral metal nanoclusters into supramolecular chiral aggregates is of interest for developing advanced materials. Herein, we manipulated the self-assembly of Au nanoclusters modified by l-/d-cysteine (l-/d-AuNCs) into ordered microstructures featuring enhanced phosphorescence and optical activities. The formation of these aggregates was driven by synergistic effect of coordination and electrostatic interactions assisted by Cd²⁺/H⁺. Detailed structural characterization and theoretical studies confirmed that the compact aggregation structures are essential for the emission enhancement and the chirality amplification of l-/d-AuNCs. Interestingly, upon the formation of microflowers, the emission lifetime was prolonged to 3.34 ms with a switch from fluorescence to phosphorescence induced by aurophilic Au(I)···Au(I) interactions and intensive ligand-to-metal charge transfer (LMCT). Moreover, both the CD and photoluminescence (PL) signals of the microflowers exhibited pH-responsiveness. This dual-mode sensitive platform could be developed as a pH sensor with improved accuracy. Additionally, the pH-responsive photoluminescence ON/OFF switch of the microflowers could be employed for reliable information encryption and decryption. This study provides useful ideas for regulating the self-assembly of nanoclusters to generate desired photophysical properties with potential applications.

Biomolecule-mediated chiral nanostructures: a review of chiral mechanism and application

The chirality of biomolecules is vital importance in biosensing and biomedicine. However, most biomolecules only have a chiral response in the ultraviolet region, and the corresponding chiral signal is weak. In recent years, inorganic nanomaterials can adjust chiral light signals to the visible and near-infrared regions and enhance optical signals due to their high polarizability and adjustable morphology-dependent optical properties. Nonetheless, inorganic nanomaterials usually lack specificity to identify targets, and have strong toxicity when applied in organisms. The combination of chiral biomolecules and inorganic nanomaterials offers a way to solve these problems. Because chiral biomolecules, such as DNA, amino acids, and peptides, have programmability, specific recognition, excellent biocompatibility, and strong binding force to inorganic nanomaterials. Biomolecule-mediated chiral nanostructures show specific recognition of targets, extremely low biological toxicity and adjustable optical activity by regulating, assembling and inducing inorganic nanomaterials. Therefore, biomolecule-mediated chiral nanostructures have received widespread attention, including chiral biosensing, enantiomers recognition and separation, biological diagnosis and treatment, chiral catalysis, and circular polarization of chiral metamaterials. This review mainly introduces the three chiral mechanisms of biomolecule-mediated chiral nanostructures, lists some important applications at present, and discusses the development prospects of biomolecule-mediated chiral nanostructures.

Structural complexity induced by {110} blocking of cysteine in electrochemical copper deposition on silver nanocubes

Morphology evolution into intricate structures at the nanoscale is hard to understand, but we can get critical information from the combination of ex situ and in situ spectroelectrochemical techniques. In this study, we investigated the structural complexity generated during electrochemical Cu deposition on individual Ag nanocubes, which was driven by surface regulating cysteine molecules. During the deposition process, selective nucleation occurred on the Ag nanocubes by underpotential deposition, and then sequential structural evolution to a windmill morphology was observed. By adjusting the cysteine coverage, diverse structures were yielded, including face-overgrown, four-leaf clover, and octapod-like structures. Structural analysis along the crystallographic directions demonstrated that cysteine molecules exclusively blocked the growth along 110 and relatively promoted the growth along 100 and 111, respectively. Interestingly, all morphologies maintained a highly symmetric nature from the pristine cube, despite being diverse and sophisticated. These findings would be essential to design complex morphologies and achieve desirable optical and catalytic properties.

Tyrosyltyrosylcysteine-Directed Synthesis of Chiral Cobalt Oxide Nanoparticles and Peptide Conformation Analysis

Chiral inorganic nanomaterials have revealed opportunities in various fields owing to their strong light-matter interactions. In particular, chiral metal oxide nanomaterials that can control light and biochemical reactions have been highlighted due to their catalytic activity and biocompatibility. In this study, we present the synthesis of chiral cobalt oxide nanoparticles with a g-factor of 0.01 in the UV-visible region using l- and d-Tyr-Tyr-Cys ligands. The conformation of the Tyr-Tyr-Cys peptide on the nanoparticle surfaces was identified by 2D NMR spectroscopy analysis. In addition, the sequence effect of Tyr-Tyr-Cys developing chiral nanoparticles was analyzed. The revealed peptide structure, along with the experimental results, demonstrate the important role of the thiol group and carboxyl group of the Tyr-Tyr-Cys ligand in chirality evolution. Importantly, due to the magnetic properties of chiral cobalt oxide nanoparticles and their strong absorption in the UV region, the circular dichroism (CD) responses can be dramatically modulated under an external magnetic field.

Chirality Detection by Raman Spectroscopy: The Case of Enantioselective Interactions between Amino Acids and Polymer-Modified Chiral Silica

In chirality research area, it is of interest to reveal the chiral feature of inorganic nanomaterials and their enantioselective interactions with biomolecules. Although common Raman spectroscopy is not regarded as a direct chirality analysis tool, it is in fact effective and sensitive to study the enantioselectivity phenomena, which is demonstrated by the enantio-discrimination of amino acid enantiomers using the polydopamine-modified intrinsically chiral SiO₂ nanofibers in this work. The Raman scattering intensities of an enantiomer of cysteine are more than twice as high as those of the other enantiomer with opposite handedness. Similar results were also found in the cases of cystine, phenylalanine, and tryptophan enantiomers. In turn, these organic molecules could be used as chirality indicators for SiO₂, which was clarified by the unique Raman spectra-derived mirror-image relationships. Thus, an indirect chirality detection method for inorganic nanomaterials was developed.