Octo-diamond crystal of nanoscale tetrahedra with interchanging chiral motifs

Despite their simplicity, tetrahedra can assemble into diverse high- and low-density structures. Here we report a low-density 'octo-diamond' structure formed by nanoscale solid tetrahedra with a 64-tetrahedron unit cell containing 8 cubic-diamond subcells. The formed crystal is achiral, but is composed of chiral bilayers with alternating handedness. The left- and right-handed chirality of the bilayers, combined with the plasmonic nature of the gold tetrahedra, produces chiroptical responses at the crystal surface. We uncover that the hydrophobic substrate facilitates the arrangement of tetrahedra into irregular ring-like patterns, creating a critical, uneven topography to stabilize the observed octo-diamond structure. This study reveals a potent way to affect colloidal crystallization through particle-substrate interactions, expanding the nanoparticle self-assembly toolbox.

Nanofabrication for Nanophotonics

Nanofabrication, a pivotal technology at the intersection of nanoscale engineering and high-resolution patterning, has substantially advanced over recent decades. This technology enables the creation of nanopatterns on substrates crucial for developing nanophotonic devices and other applications in diverse fields including electronics and biosciences. Here, this mega-review comprehensively explores various facets of nanofabrication focusing on its application in nanophotonics. It delves into high-resolution techniques like focused ion beam and electron beam lithography, methods for 3D complex structure fabrication, scalable manufacturing approaches, and material compatibility considerations. Special attention is given to emerging trends such as the utilization of two-photon lithography for 3D structures and advanced materials like phase change substances and 2D materials with excitonic properties. By highlighting these advancements, the review aims to provide insights into the ongoing evolution of nanofabrication, encouraging further research and application in creating functional nanostructures. This work encapsulates critical developments and future perspectives, offering a detailed narrative on the state-of-the-art in nanofabrication tailored for both new researchers and seasoned experts in the field.

Transforming achiral semiconductors into chiral domains with exceptional circular dichroism

Highly concentrated solutions of asymmetric semiconductor magic-sized clusters (MSCs) of cadmium sulfide, cadmium selenide, and cadmium telluride were directed through a controlled drying meniscus front, resulting in the formation of chiral MSC assemblies. This process aligned their transition dipole moments and produced chiroptic films with exceptionally strong circular dichroism. G-factors reached magnitudes as high as 1.30 for drop-cast films and 1.06 for patterned films, approaching theoretical limits. By controlling the evaporation geometry, various domain shapes and sizes were achieved, with homochiral domains exceeding 6 square millimeters that transition smoothly between left- and right-handed chirality. Our results uncovered fundamental relationships between meniscus deposition processes, the alignment of supramolecular filaments and their MSC constituents, and their connection to emergent chiral properties.

Helical Assemblies of Colloidal Nanocrystals with Long-Range Order and Their Fusion into Continuous Structures

Chirality epitomizes the sophistication of chemistry, representing some of its most remarkable achievements. Yet, the precise synthesis of chiral structures from achiral building blocks remains a profound and enduring challenge in synthetic chemistry and materials science. Here, we demonstrate that achiral colloidal nanocrystals, including Au and Ag nanocrystals, can assemble into long-range-ordered helical assemblies with the assistance of chiral molecules. The synchronized aggregation kinetics between colloidal silver or gold nanocrystals and π-conjugated perylene diimide molecules enables the nanocrystals to precisely follow the helical pathways of the molecular assemblies. This results in the formation of helical nanocrystal assemblies extending over tens of micrometers. These helically organized nanocrystals, exhibiting high positional precision, display linear size-dependent chiroptical properties. Furthermore, more intricate helical assemblies, featuring triple, quadruple, and quintuple nanocrystal strands, can be observed in addition to the commonly encountered double helical assemblies. Finally, these helical assemblies, composed of discrete Ag nanocrystals, can fuse into continuous Ag2S helical structures following a sulfidation reaction, ultimately leading to the formation of diverse metal sulfide helices through cation exchange processes.

Chiral Symmetry Breaking in Nanocrystal Superlattices Enabled by Shear and Nanowires

The self-assembly of colloidal nanocrystals typically leads to the formation of highly symmetric superlattices, while chiral symmetry breaking within these structures remains rare. Here, we present a universal approach for achieving chiral symmetry breaking within self-assembled nanocrystal superlattices through the incorporation of nanowires and shear force. The networked film, composed of highly flexible nanowires that are only a few nanometers in diameter and bound by weak van der Waals interactions, can be manipulated to stretch and rotate, resulting in a controlled chiral pattern with a specified handedness. When combined with nanocrystal superlattices, the nanowires convey mechanical torque to the nanocrystals, inducing chiral symmetry breaking in the solid materials. This method is versatile and can be applied to various nanocrystal solids irrespective of their size, shape, or composition. Overall, this study enhances the repertoire of fabrication techniques for chiral nanomaterials, circumventing the need for chiral molecules.

Geometric Frustration Directs the Self-assembly of Nanoparticles with Crystallized Ligand Bundles

Polymer-grafted nanoparticles are versatile building blocks that self-assemble into a diverse range of mesostructures. Coarse-grained molecular simulations have commonly accompanied experiments by resolving structure formation pathways and predicting phase behavior. Past simulations represented nanoparticles as spheres and the ligands as flexible chains of beads, isotropically tethered to the nanoparticles. Here, we investigate a different minimal coarse-grained model. The model consists of an attractive rod tethered to a repulsive sphere. The motivation of this rod-sphere model is to describe nanospheres with a partially crystallized, stretched polymeric bundle as well as other complex building blocks such as rigid surfactants and end-tethered nanorods. Varying the ratio of sphere size to rod radius stabilizes self-limited clusters and other mesostructures with reduced dimensionality. The complex phase behavior we observe is a consequence of geometric frustration.

Achiral and chiral ligands synergistically harness chiral self-assembly of inorganics

Chiral structures and functions are essential natural components in biominerals and biological crystals. Chiral molecules direct inorganics through chiral growth of facets or screw dislocation of crystal clusters. As chirality promoters, they initiate an asymmetric hierarchical self-assembly in a quasi-thermodynamic steady state. However, achieving chiral assembly requires a delicate balance between intricate interactions. This complexity causes the roles of achiral-chiral and inorganic components in crystallization to remain ambiguous. Here, we elucidate a definitive mechanism using an achiral-chiral ligand strategy to assemble inorganics into hierarchical, self-organized superstructures. Achiral ligands cluster inorganic building blocks, while chiral ligands impart chiral rotation. Achiral and chiral ligands can flexibly modulate the chirality of superstructures by fully using their competition in coordination chemistry. This dual-ligand strategy offers a versatile framework for engineering chiroptical nanomaterials tailored to optical devices and metamaterials with optical activities across a broad wavelength range, with applications in imaging, detection, catalysis, and sensing.

Engineering Anisotropy into Organized Nanoscale Matter

Programming the organization of discrete building blocks into periodic and quasi-periodic arrays is challenging. Methods for organizing materials are particularly important at the nanoscale, where the time required for organization processes is practically manageable in experiments, and the resulting structures are of interest for applications spanning catalysis, optics, and plasmonics. While the assembly of isotropic nanoscale objects has been extensively studied and described by empirical design rules, recent synthetic advances have allowed anisotropy to be programmed into macroscopic assemblies made from nanoscale building blocks, opening new opportunities to engineer periodic materials and even quasicrystals with unnatural properties. In this review, we define guidelines for leveraging anisotropy of individual building blocks to direct the organization of nanoscale matter. First, the nature and spatial distribution of local interactions are considered and three design rules that guide particle organization are derived. Subsequently, recent examples from the literature are examined in the context of these design rules. Within the discussion of each rule, we delineate the examples according to the dimensionality (0D-3D) of the building blocks. Finally, we use geometric considerations to propose a general inverse design-based construction strategy that will enable the engineering of colloidal crystals with unprecedented structural control.

Chiral inorganic nanomaterials in the tumor microenvironment: A new chapter in cancer therapy

Chirality plays a crucial function in the regulation of normal physiological processes and is widespread in organisms. Chirality can be imparted to nanomaterials, whether they are natural or manmade, through the process of asymmetric assembly and/or grafting of molecular chiral groups or linkers. Chiral inorganic nanomaterials possess unique physical and chemical features that set them apart from regular nanomaterials. They also have the ability to interact with cells and tissues in a specific manner, making them useful in various biomedical applications, particularly in the treatment of tumors. Despite the growing amount of research on chiral inorganic nanomaterials in the tumor microenvironment (TME) and their promising potential applications, there is a lack of literature that comprehensively summarizes the intricate interactions between chiral inorganic nanomaterials and TME. In this review, we introduce the fundamental concept, classification, synthesis methods, and physicochemical features of chiral inorganic nanomaterials. Next, we briefly outline the components of TME, such as T cells, macrophages, dendritic cells, and weak acids, and then discuss the anti-tumor effects of several chiral inorganic nanoparticles targeting these components and their potential for possible application during cancer therapy. Finally, the present challenges faced by chiral inorganic nanomaterials in cancer treatment and their future areas of investigation are disclosed.

Chiral Transfer and Evolution in Cysteine Induced Cobalt Superstructures

Chiral organic additives have unveiled the extraordinary capacity to form chiral inorganic superstructures, however, complex hierarchical structures have hindered the understanding of chiral transfer and growth mechanisms. This study introduces a simple hydrothermal synthesis method for constructing chiral cobalt superstructures with cysteine, demonstrating specific recognition of chiral molecules and outstanding electrocatalytic activity. The mild preparation conditions allow in situ tracking of chirality evolution in the chiral cobalt superstructure, offering unprecedented insights into the chiral transfer and amplification mechanism. The resulting superstructures exhibit a universal formation process applicable to other metal oxides, extending the understanding of chiral superstructure evolution. This work contributes not only to the fundamental understanding of chirality in self-assembled structures but also provides a versatile method for designing chiral inorganic nanomaterials with remarkable molecular recognition and electrocatalytic capabilities.

Structural and Electronic Chirality in Inorganic Crystals: from Construction to Application

Chirality represents a fundamental characteristic inherent in nature, playing a pivotal role in the emergence of homochirality and the origin of life. While the principles of chirality in organic chemistry are well-documented, the exploration of chirality within inorganic crystal structures continues to evolve. This ongoing development is primarily due to the diverse nature of crystal/amorphous structures in inorganic materials, along with the intricate symmetrical and asymmetrical relationships in the geometry of their constituent atoms. In this review, we commence with a summary of the foundational concept of chirality in molecules and solid states matters. This is followed by an introduction of structural chirality and electronic chirality in three-dimensional and two-dimensional inorganic materials. The construction of chirality in inorganic materials is classified into physical photolithography, wet-chemistry method, self-assembly, and chiral imprinting. Highlighting the significance of this field, we also summarize the research progress of chiral inorganic materials for applications in optical activity, enantiomeric recognition and chiral sensing, selective adsorption and enantioselective separation, asymmetric synthesis and catalysis, and chirality-induced spin polarization. This review aims to provide a reference for ongoing research in chiral inorganic materials and potentially stimulate innovative strategies and novel applications in the realm of chirality.

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.

Graph-theoretical chirality measure and chirality-property relations for chemical structures with multiscale mirror asymmetries

Chirality is an essential geometric property unifying small molecules, biological macromolecules, inorganic nanomaterials, biological microparticles, and many other chemical structures. Numerous chirality measures have attempted to quantify this geometric property of mirror asymmetry and to correlate these measures with physical and chemical properties. However, their utility has been widely limited because these correlations have been largely notional. Furthermore, chirality measures also require prohibitively demanding computations, especially for chiral structures comprised of thousands of atoms. Acknowledging the fundamental problems with quantification of mirror asymmetry, including the ambiguity of sign-variable pseudoscalar chirality measures, we revisit this subject because of the significance of quantifying chirality for quantitative biomimetics and describing the chirality of nanoscale materials that display chirality continuum and scale-dependent mirror asymmetry. We apply the concept of torsion within the framework of differential geometry to the graph theoretical representation of chiral molecules and nanostructures to address some of the fundamental problems and practical limitations of other chirality measures. Chiral gold clusters and other chiral structures are used as models to elaborate a graph-theoretical chirality (GTC) measure, demonstrating its applicability to chiral materials with different degrees of chirality at different scales. For specific cases, we show that GTC provides an adequate description of both the sign and magnitude of mirror asymmetry. The direct correlations with macroscopic properties, such as chiroptical spectra, are enhanced by using the hybrid chirality measures combining parameters from discrete mathematics and physics. Taking molecular helices as an example, we established a direct relation between GTC and optical activity, indicating that this chirality measure can be applied to chiral metamaterials and complex chiral constructs.

Direct-write 3D printing of plasmonic nanohelicoids by circularly polarized light

Chiral plasmonic surfaces with 3D "forests" from nanohelicoids should provide strong optical rotation due to alignment of helical axis with propagation vector of photons. However, such three-dimensional nanostructures also demand multi-step nanofabrication, which is incompatible with many substrates. Large-scale photonic patterns on polymeric and flexible substrates remain unattainable. Here, we demonstrate the substrate-tolerant direct-write printing and patterning of silver nanohelicoids with out-of-plane 3D orientation using circularly polarized light. Centimeter-scale chiral plasmonic surfaces can be produced within minutes using inexpensive medium-power lasers. The growth of nanohelicoids is driven by the symmetry-broken site-selective deposition and self-assembly of the silver nanoparticles (NPs). The ellipticity and wavelength of the incident photons control the local handedness and size of the printed nanohelicoids, which enables on-the-fly modulation of nanohelicoid chirality during direct writing and simple pathways to complex multifunctional metasurfaces. Processing simplicity, high polarization rotation, and fine spatial resolution of the light-driven printing of stand-up helicoids provide a rapid pathway to chiral plasmonic surfaces, accelerating the development of chiral photonics for health and information technologies.

Tuning the Chiral Growth of Plasmonic Bipyramids via the Wavelength and Polarization of Light

Circularly polarized light (CPL) is a versatile tool to prepare chiral nanostructures, but the mechanism for inducing enantioselectivity is not well understood. This work shows that the energy and polarization of visible photons can initiate photodeposition at different sites on plasmonic nanocrystals. Here, CPL on achiral gold bipyramids (AuBPs) creates hot holes that oxidatively deposit PbO2 asymmetrically. We show for the first time that the location of PbO2 photodeposition and hence optical dissymmetry depends on the CPL wavelength. Specifically, 488 and 532 nm CPL induce PbO2 growth in the middle of AuBPs, whereas 660 nm CPL induces PbO2 growth at the tips. Our observations show that wavelength-dependent plasmonic field distributions are more important than surface lightning rod effects in localizing plasmon-mediated photochemistry. The largest optical dissymmetry occurs at excitation wavelengths between the transverse and longitudinal resonances of the AuBPs because higher-order modes are required to induce chiral electric fields.

Biomimetic chiral hydrogen-bonded organic-inorganic frameworks

Assembly ubiquitously occurs in nature and gives birth to numerous functional biomaterials and sophisticated organisms. In this work, chiral hydrogen-bonded organic-inorganic frameworks (HOIFs) are synthesized via biomimicking the self-assembly process from amino acids to proteins. Enjoying the homohelical configurations analogous to α-helix, the HOIFs exhibit remarkable chiroptical activity including the chiral fluorescence (glum = 1.7 × 10-3) that is untouched among the previously reported hydrogen-bonded frameworks. Benefitting from the dynamic feature of hydrogen bonding, HOIFs enable enantio-discrimination of chiral aliphatic substrates with imperceivable steric discrepancy based on fluorescent change. Moreover, the disassembled HOIFs after recognition applications are capable of being facilely regenerated and self-purified via aprotic solvent-induced reassembly, leading to at least three consecutive cycles without losing the enantioselectivity. The underlying mechanism of chirality bias is decoded by the experimental isothermal titration calorimetry together with theoretic simulation.

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.

2D superlattices via interfacial self-assembly of polymer-grafted Au nanoparticles

Nanoparticle (NP) superlattices are periodic arrays of nanoscale building blocks. Because of the collective effect between functional NPs, NP superlattices can exhibit exciting new properties that are distinct from those of individual NPs or corresponding bulk materials. In particular, two-dimensional (2D) NP superlattices have attracted increasing attention due to their emerging applications in micro/opto-electronics, catalysis, sensing, and other fields. Among various preparation methods, evaporation-induced interfacial self-assembly has become the most popular method for preparing 2D NP superlattices because it is a simple, low-cost, and scalable process that can be widely applied to various NPs. Introducing soft ligands, such as polymers, can not only provide convenience in controlling the self-assembly process and tuning superlattice structures but also improve the properties of 2D NP superlattices. This feature article focuses on the methods of evaporation-induced self-assembly of polymer-grafted Au NPs into free-standing 2D NP superlattice films at air/liquid interfaces and 2D NP superlattice coatings on substrates, followed by studies on in situ tracking of the self-assembly evolution process through small-angle X-ray scattering. Their application in nano-floating gate memory devices is also included. Finally, the challenges and perspectives of this direction are discussed.

Breaking AgInTe2 Quantum Dot Chain to Fabricate AgInTe2-ZnS Janus Nanocrystals

Colloidal multinary chalcogenides (MnCs) have emerged as excellent optoelectronic materials, where S- and Se-based MnCs show considerable progress; however, the Te counterpart suffers from detrimental surface oxidation. Moreover, Te-based I-III-VI MnCs (e.g., AgInTe2) tend to form a one-dimensional (1-D) anisotropic structure via the self-assembly of surface-oxidized Te, thus restricting the isolation of AgInTe2 quantum dots (QDs). We report successful control of the self-assembly of Te-based MnCs to arrest the growth of AgInTe2 QDs by using a synergistic capping agent (dodecanethiol and oleic acid). The reaction proceeds with several intermediates, including hexagonal microrods (MR), tetragonal QDs in a chain arrangement, and tetragonal MRs. Importantly, we note that the incorporation of ZnS QDs triggers the breaking of the chain arrangement of the AgInTe2 QDs and the emergence of evenly distributed AgInTe2-ZnS Janus nanocrystals with significantly reduced long-term Te-oxidative properties. Arresting the AgInTe2 QD chain and the subsequent Janus nanocrystal formation could have promising opportunities for 1-D charge hopping and efficient charge transport for optoelectronic applications, respectively.

Self-Organization of Iron Sulfide Nanoparticles into Complex Multicompartment Supraparticles

Self-assembled compartments from nanoscale components are found in all life forms. Their characteristic dimensions are in 50-1000 nm scale, typically assembled from a variety of bioorganic "building blocks". Among the various functions that these mesoscale compartments carry out, protection of the content from the environment is central. Finding synthetic pathways to similarly complex and functional particles from technologically friendly inorganic nanoparticles (NPs) is needed for a multitude of biomedical, biochemical, and biotechnological processes. Here, it is shown that FeS2 NPs stabilized by l-cysteine self-assemble into multicompartment supraparticles (mSPs). The NPs initially produce ≈55 nm concave assemblies that reconfigure into ≈75 nm closed mSPs with ≈340 interconnected compartments with an average size of ≈5 nm. The intercompartmental partitions and mSP surface are formed primarily from FeS2 and Fe2 O3 NPs, respectively. The intermediate formation of cup-like particles enables encapsulation of biological cargo. This capability is demonstrated by loading mSPs with DNA and subsequent transfection of mammalian cells. Also it is found that the temperature stability of the DNA cargo is enhanced compared to the traditional delivery vehicles. These findings demonstrate that biomimetic compartmentalized particles can be used to successfully encapsulate and enhance temperature stability of the nucleic acid cargo for a variety of bioapplications.

Spiral Square Nanosheets Assembled from Ru Clusters

Spiral two-dimensional (2D) nanosheets exhibit unique physical and chemical phenomena due to their twisted structures. While self-assembly of clusters is an ideal strategy to form hierarchical 2D structures, it is challenging to form spiral nanosheets. Herein, we first report a screw dislocation involved assembled method to obtain 2D spiral cluster assembled nanosheets (CANs) with uniform square morphology. The 2D spiral Ru CANs with a length of approximately 4 μm and thickness of 20.7 ± 3.0 nm per layer were prepared via the assembly of 1-2 nm Ru clusters in the presence of molten block copolymer Pluronic F127. Cryo-electron microscopy (cryo-EM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) demonstrate the existence of screw dislocation in the spiral assembled structure. The X-ray absorption fine structure spectrum indicates that Ru clusters are Ru³⁺ species, and Ru atoms are mainly coordinated with Cl with a coordination number of 6.5. Fourier-transform infrared (FT-IR) spectra and solid-state nuclear magnetic resonance hydrogen spectra (¹H NMR) indicate that the assembly process of Ru clusters is formed by noncovalent interactions, including hydrogen bonding and hydrophilic interactions. Additionally, the Ru-F127 CANs exhibit excellent photothermal conversion performance in the near-infrared (NIR) region.

Chirality Analysis of Complex Microparticles using Deep Learning on Realistic Sets of Microscopy Images

Nanoscale chirality is an actively growing research field spurred by the giant chiroptical activity, enantioselective biological activity, and asymmetric catalytic activity of chiral nanostructures. Compared to chiral molecules, the handedness of chiral nano- and microstructures can be directly established via electron microscopy, which can be utilized for the automatic analysis of chiral nanostructures and prediction of their properties. However, chirality in complex materials may have multiple geometric forms and scales. Computational identification of chirality from electron microscopy images rather than optical measurements is convenient but is fundamentally challenging, too, because (1) image features differentiating left- and right-handed particles can be ambiguous and (2) three-dimensional structure essential for chirality is 'flattened' into two-dimensional projections. Here, we show that deep learning algorithms can identify twisted bowtie-shaped microparticles with nearly 100% accuracy and classify them as left- and right-handed with as high as 99% accuracy. Importantly, such accuracy was achieved with as few as 30 original electron microscopy images of bowties. Furthermore, after training on bowtie particles with complex nanostructured features, the model can recognize other chiral shapes with different geometries without retraining for their specific chiral geometry with 93% accuracy, indicating the true learning abilities of the employed neural networks. These findings indicate that our algorithm trained on a practically feasible set of experimental data enables automated analysis of microscopy data for the accelerated discovery of chiral particles and their complex systems for multiple applications.

Ligand-Triggered Self-Assembly of Flexible Carbon Dot Nanoribbons for Optoelectronic Memristor Devices and Neuromorphic Computing

Carbon dots (CDs) are widely utilized in sensing, energy storage, and catalysis due to their excellent optical, electrical and semiconducting properties. However, attempts to optimize their optoelectronic performance through high-order manipulation have met with little success to date. In this study, through efficient packing of individual CDs in two-dimensions, the synthesis of flexible CDs ribbons is demonstrated technically. Electron microscopies and molecular dynamics simulations, show the assembly of CDs into ribbons results from the tripartite balance of π-π attractions, hydrogen bonding, and halogen bonding forces provided by the superficial ligands. The obtained ribbons are flexible and show excellent stability against UV irradiation and heating. CDs ribbons offer outstanding performance as active layer material in transparent flexible memristors, with the developed devices providing excellent data storage, retention capabilities, and fast optoelectronic responses. A memristor device with a thickness of 8 µm shows good data retention capability even after 10⁴ cycles of bending. Furthermore, the device functions effectively as a neuromorphic computing system with integrated storage and computation capabilities, with the response speed of the device being less than 5.5 ns. These properties create an optoelectronic memristor with rapid Chinese character learning capability. This work lays the foundation for wearable artificial intelligence.

Electric, magnetic, and shear field-directed assembly of inorganic nanoparticles

Ordered assemblies of inorganic nanoparticles (NPs) have shown tremendous potential for wide applications due to their unique collective properties, which differ from those of individual NPs. Various assembly methods, such as external field-directed assembly, interfacial assembly, template assembly, biomolecular recognition-mediated assembly, confined assembly, and others, have been employed to generate ordered inorganic NP assemblies with hierarchical structures. Among them, the external field-directed assembly method is particularly fascinating, as it can remotely assemble NPs into well-ordered superstructures. Moreover, external fields (e.g., electric, magnetic, and shear fields) can introduce a local and/or global field intensity gradient, resulting in an additional force on NPs to drive their rotation and/or translation. Therefore, the external field-directed assembly of NPs becomes a robust method to fabricate well-defined functional materials with the desired optical, electronic, and magnetic properties, which have various applications in catalysis, sensing, disease diagnosis, energy conversion/storage, photonics, nano-floating-gate memory, and others. In this review, the effects of an electric field, magnetic field, and shear field on the organization of inorganic NPs are highlighted. The methods for controlling the well-ordered organization of inorganic NPs at different scales and their advantages are reviewed. Finally, future challenges and perspectives in this field are discussed.

Chiral Au Nanorods: Synthesis, Chirality Origin, and Applications

Chiral Au nanorods (c-Au NRs) with diverse architectures constitute an interesting nanospecies in the field of chiral nanophotonics. The numerous possible plasmonic behaviors of Au NRs can be coupled with chirality to initiate, tune, and amplify their chiroptical response. Interdisciplinary technologies have boosted the development of fabrication and applications of c-Au NRs. Herein, we have focused on the role of chirality in c-Au NRs which helps to manipulate the light-matter interaction in nontraditional ways. A broad overview on the chirality origin, chirality transfer, chiroptical activities, artificially synthetic methodologies, and circularly polarized applications of c-Au NRs will be summarized and discussed. A deeper understanding of light-matter interaction in c-Au NRs will help to manipulate the chirality at the nanoscale, reveal the natural evolution process taking place, and set up a series of circularly polarized applications.

Synthesis of Ligand-Induced Chiral Tellurium Nanocrystals

Chiral tellurium nanoparticles have recently garnered tremendous attention as emerging inorganic nanomaterials with intrinsically chiral space groups owing to their potential in next-generation stereosynthesis, spintronics, and optoelectronics. Inspired by the chiral ligand-mediated synthetic strategy, we herein present hydrothermal-assisted synthesis of chiral polyhedral tellurium nanoparticles that provides differed chirogenesis than that of particles fabricated by wet chemistry in recent studies; the thiolated cysteine molecules change the morphology of tellurium nanoparticles from fundamental two-dimensional shapes to chiral three-dimensional polyhedra owing to the screw dislocation effects observed only during nanoparticle growth. However, the nanoparticles do not exhibit chiral behaviors at the nucleation stage. Further investigation indicates that the growth of chiral polyhedral tellurium nanoparticles is overwhelmingly affected by parameters such as the hydrothermal reaction time, amount of polyvinylpyrrolidone, and species of chiral molecules. We believe that these findings can provide new insights into the fundamental relationships among structural chirality, chiral ligands, screw dislocations, and chiral space groups in principle.

Ligand-Free Direct Optical Lithography of Bare Colloidal Nanocrystals via Photo-Oxidation of Surface Ions with Porosity Control

Microscale patterning of colloidal nanocrystal (NC) films is important for their integration in devices. Here, we introduce the direct optical patterning of all-inorganic NCs without the use of additional photosensitive ligands or additives. We determined that photoexposure of ligand-stripped, "bare" NCs in air significantly reduces their solubility in polar solvents due to photo-oxidation of surface ions. Doses as low as 20 mJ/cm² could be used; the only obvious criterion for material selection is that the NCs need to have significant absorption at the irradiation wavelength. However, transparent NCs can still be patterned by mixing them with suitably absorbing NCs. This approach enabled the patterning of bare ZnSe, CdSe, ZnS, InP, CeO₂, CdSe/CdS, and CdSe/ZnS NCs as well as mixtures of ZrO₂ or HfO₂ NCs with ZnSe NCs. Optical, X-ray photoelectron, and infrared spectroscopies show that solubility loss results from desorption of bound solvent due to photo-oxidation of surface ions. We also demonstrate two approaches, compatible with our patterning method, for modulating the porosity and refractive index of NC films. Block copolymer templating decreases the film density, and thus the refractive index, by introducing mesoporosity. Alternatively, hot isostatic pressing increases the packing density and refractive index of NC layers. For example, the packing fraction of a ZnS NC film can be increased from 0.51 to 0.87 upon hot isostatic pressing at 450 °C and 15 000 psi. Our findings demonstrate that direct lithography by photo-oxidation of bare NC surfaces is an accessible patterning method for facilitating the exploration of more complex NC device architectures while eliminating the influence of bulky or insulating surfactants.

Biomimetic Self-Assembled Chiral Inorganic Nanomaterials: A New Strategy for Solving Medical Problems

The rapid expansion of the study of chiral inorganic structures has led to the extension of the functional boundaries of inorganic materials. Nature-inspired self-assembled chiral inorganic structures exhibit diverse morphologies due to their high assembly efficiency and controlled assembly process, and they exhibit superior inherent properties such as mechanical properties, chiral optical activity, and chiral fluorescence. Although chiral self-assembled inorganic structures are becoming more mature in chiral catalysis and chiral optical regulation, biomedical research is still in its infancy. In this paper, various forms of chiral self-assembled inorganic structures are summarized, which provides a structural starting point for various applications of chiral self-assembly inorganic structures in biomedical fields. Based on the few existing research statuses and mechanism discussions on the chiral self-assembled materials-mediated regulation of cell behavior, molecular probes, and tumor therapy, this paper provides guidance for future chiral self-assembled structures to solve the same or similar medical problems. In the field of chiral photonics, chiral self-assembled structures exhibit a chirality-induced selection effect, while selectivity is exhibited by chiral isomers in the medical field. It is worth considering whether there is some correspondence or juxtaposition between these phenomena. Future chiral self-assembled structures in medicine will focus on the precise treatment of tumors, induction of soft and hard tissue regeneration, explanation of the biochemical mechanisms and processes of its medical effects, and improvement of related theories.

Modulation of Nano-superstructures and Their Optical Properties

Self-assembly, which enables spontaneous arrangement of objects, is of particular importance for nanomaterials in both fundamental and applied research fields. Multiple types of nanoparticle superstructures have been successfully built in highly controllable and efficient manners through balancing the nanoscale interactions. Uniform and proper arrangement of nanoparticles inside the assembled superstructures is essential to exhibit their constant, reliable, and homogeneous functionalities. To be specific, the long-range ordered superlattices not only succeed with their building blocks' intrinsic property, but also, more importantly, can display collective properties that are absent both in individual nanoparticles and in their bulk states. One of the most attractive aspects of nanomaterials is their exceptional optical properties that have tremendous application potential in multidisciplinary fields. In this regard, constructing the superstructures from optical nano units like noble metal nanostructures, semiconductor nanoparticles, or hybrid nanomaterials is critical for attaining the unique optical properties and exploring their practical applications in multiple fields including photonics, optoelectronics, optical sensing, photocatalysis, etc. In this Account, we provide guidelines for self-assembly strategies to fabricate the superstructures and discuss the optical properties that the superstructures display. In the first part, we categorize and discuss the key factors that strongly affect the self-assembly process and determine the configurational and integral quality of the superstructures. On one hand, the diversity and designability of nanoparticles offer the intrinsic complexity of the building blocks, including geometry, size, composition, and surface ligand, which efficiently tailors the assembly process and superstructure configuration. On the other hand, multiple factors originating from the introduction of extrinsic features are recognized to facilitate the metastable or dynamic self-assembly process. Such extrinsic features include both matter like DNA origami, peptides, small molecules, etc. and nonmatter involved with electric fields, magnetic fields, light, temperature, etc. In the second part, we introduce the state-of the art progress on the collective optical performances of the assembled superstructures, including (1) chiral optics, such as circular dichroism and circularly polarized luminescence, (2) plasmonic properties and related applications, and (3) luminescence related optics and their applications. Finally, we summarize the existing problems and main challenges briefly, and some future directions of this field are proposed. We envision that, with deep understanding of the assembly mechanism and development of the synthetic and surface chemistry, rational modulation of nanoassemblies will be the trend of this field, which is beneficial to achieve the emerging collective performances and create new generation devices with advanced functions.

Assembly of planar chiral superlattices from achiral building blocks

The spontaneous assembly of chiral structures from building blocks that lack chirality is fundamentally important for colloidal chemistry and has implications for the formation of advanced optical materials. Here, we find that purified achiral gold tetrahedron-shaped nanoparticles assemble into two-dimensional superlattices that exhibit planar chirality under a balance of repulsive electrostatic and attractive van der Waals and depletion forces. A model accounting for these interactions shows that the growth of planar structures is kinetically preferred over similar three-dimensional products, explaining their selective formation. Exploration and mapping of different packing symmetries demonstrates that the hexagonal chiral phase forms exclusively because of geometric constraints imposed by the presence of constituent tetrahedra with sharp tips. A formation mechanism is proposed in which the chiral phase nucleates from within a related 2D achiral phase by clockwise or counterclockwise rotation of tetrahedra about their central axis. These results lay the scientific foundation for the high-throughput assembly of planar chiral metamaterials.

The formation of nanostructures with chiral symmetry often requires chiral directing agents at a smaller length scale. Here, the authors report the self-assembly of 2D chiral superlattices from achiral tetrahedron-shaped building blocks.

Recent advances in chiral nanomaterials with unique electric and magnetic properties

Research on chiral nanomaterials (NMs) has grown radically with a rapid increase in the number of publications over the past decade. It has attracted a large number of scientists in various fields predominantly because of the emergence of unprecedented electric, optical, and magnetic properties when chirality arises in NMs. For applications, it is particularly informative and fascinating to investigate how chiral NMs interact with electromagnetic waves and magnetic fields, depending on their intrinsic composition properties, atomic distortions, and assembled structures. This review provides an overview of recent advances in chiral NMs, such as semiconducting, metallic, and magnetic nanostructures.

Chirality of Fingerprints: Pattern- and Curvature-Induced Emerging Chiroptical Properties of Elastomeric Grating Meta-Skin

Fingerprint-inspired elastomeric grating meta-skin (EGMS) is herein fabricated to investigate the chirality of fingerprints. The EGMS is made by a facile nanoimprinting method with a diffraction grating as a template using polydimethylsiloxane, followed by gold deposition. The chirality of the surface is caused by symmetry breaking, induced by the pattern (P) and curvature (T). Furthermore, the chiroptical properties of EGMS are reconfigurable through the control of the skew angle (θ), which is the angle between P and T. The chiroptical properties of a fingerprint are also shown and interpreted in this perspective. On the basis of the results, we suggest the strategy to impart chirality on the surface, which is reconfigurable by controlling P and T. It will be a useful method to produce chirality in membranes, thin films, metasurfaces, and 2D nanomaterials, as well as advance biometric recognition.

Chiral Helices Formation by Self-Assembled Molecules on Semiconductor Flexible Substrates

The crystal structure of atomically defined colloidal II-VI semiconductor nanoplatelets (NPLs) induces the self-assembly of organic ligands over thousands of square nanometers on the top and bottom basal planes of these anisotropic nanoparticles. NPLs curl into helices under the influence of the surface stress induced by these ligands. We demonstrate the control of the radii of NPL helices through the ligands described as an anchoring group and an aliphatic chain of a given length. A mechanical model accounting for the misfit strain between the inorganic core and the surface ligands predicts the helices' radii. We show how the chirality of the helices can be tuned by the ligands anchoring group and inverted from one population to another.

Rigidity Dictates Spontaneous Helix Formation of Thermoresponsive Colloidal Chains in Poor Solvent

The formation of helical motifs typically requires specific directional interactions. Here, we demonstrate that isotropic interparticle attraction can drive self-assembly of colloidal chains into thermo-reversible helices, for chains with a critical level of backbone rigidity. We prepare thermoresponsive colloidal chains by cross-linking PNIPAM microgel-coated polystyrene colloids ("monomers"), aligned in an AC electric field. We control the chain rigidity by varying cross-linking time. Above the LCST of PNIPAM, there is an effective attraction between monomers so that the colloidal chains are in a bad solvent. On heating, the chains decrease in size. For the most rigid chains, the decrease is modest and is not accompanied by a change in shape. Much less rigid chains form relatively compact structures, resulting in a large increase in the local monomer density. Unusually, chains with intermediate rigidity spontaneously assemble into helical structures. The chain helicity increases with temperature and plateaus above the collapse transition temperature of the microgel particles. We simulate a minimal model that captures the spontaneous emergence of the helical conformations of the polymeric chain and provides insight into this shape transition. Our work suggests that a purely mechanical instability for semiflexible filaments can drive helix formation, without the need to invoke directional interactions.

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.

Supramolecular Chirality from Hierarchical Self-Assembly of Atomically Precise Silver Nanoclusters Induced by Secondary Metal Coordination

Chiral assembly of metal nanoparticles (NPs) into complex superstructures has been widely studied, but their formation mechanisms still remain mysterious due to the lack of precise structural information from the metal-organic interface to metallic kernel. As "molecular models" of metal NPs, atomically precise metal nanoclusters (NCs) used in the assembly of a macroscale superstructure will provide details of microscopic structure for deep understanding of such highly sophisticated assemblies; however, chiral superstructures have not been realized starting from achiral metal NCs with atomic precision. Herein, we report the supramolecular assembly of a water-soluble silver NC ((NH₄)₉[Ag₉(mba)₉], H₂mba = 2-mercaptobenzoic acid, abbreviated as Ag₉-NCs hereafter) into chiral hydrogels induced by the coordination of secondary metal ions. Single crystal X-ray diffraction reveals the triskelion-like structure of Ag₉-NCs with a pseudochiral conformation caused by special arrangement of the peripheral mba^2- ligands. The enantioselective orientation of the peripheral carboxyl group facilitates the assembly of Ag₉-NCs into nanotubes with a chiral cubic (I*) lattice when coordinating to Ba²⁺. The nanotubes can further intertwine into one-dimensional chiral nanobraids with a preferred left-handed arrangement. These multiple levels of chirality can be tuned by drying, during which the I* phase is missing but the chiral entanglement of the nanotubes is enhanced. Through the gelation of atomically precise, achiral NCs coordination of secondary metal ions, chiral amplification of superstructures was realized. The origination of the chirality at different length scales was also discussed.

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.

Semiconductor Bow-Tie Nanoantenna from Coupled Colloidal Quantum Dot Molecules

Top-down fabricated nanoantenna architectures of both metallic and dielectric materials show powerful functionalities for Raman and fluorescence enhancement with relevance to single molecule sensing while inducing directionality of chromophore emission with implications for single photon sources. We synthesize the smallest bow-tie nanoantenna by selective tip-to-tip fusion of two tetrahedral colloidal quantum dots (CQDs) forming a dimer. While the tetrahedral monomers emit non-polarized light, the bow-tie architecture manifests nanoantenna functionality of enhanced emission polarization along the bow-tie axis, as predicted theoretically and revealed by single-particle spectroscopy. Theory also predicts the formation of an electric-field hotspot at the bow-tie epicenter. This is utilized for selective light-induced photocatalytic metal growth at that location, unlike growth on the free tips in dark conditions, thus demonstrating bow-tie dimer functionality as a photochemical reaction center.

Double-helical assembly of heterodimeric nanoclusters into supercrystals

DNA has long been used as a template for the construction of helical assemblies of inorganic nanoparticles^1-5. For example, gold nanoparticles decorated with DNA (or with peptides) can create helical assemblies^6-9. But without such biological ligands, helices are difficult to achieve and their mechanism of formation is challenging to understand^10,11. Atomically precise nanoclusters that are protected by ligands such as thiolate^12,13 have demonstrated hierarchical structural complexity in their assembly at the interparticle and intraparticle levels, similar to biomolecules and their assemblies¹⁴. Furthermore, carrier dynamics can be controlled by engineering the structure of the nanoclusters¹⁵. But these nanoclusters usually have isotropic structures^16,17 and often assemble into commonly found supercrystals¹⁸. Here we report the synthesis of homodimeric and heterodimeric gold nanoclusters and their self-assembly into superstructures. While the homodimeric nanoclusters form layer-by-layer superstructures, the heterodimeric nanoclusters self-assemble into double- and quadruple-helical superstructures. These complex arrangements are the result of two different motif pairs, one pair per monomer, where each motif bonds with its paired motif on a neighbouring heterodimer. This motif pairing is reminiscent of the paired interactions of nucleobases in DNA helices. Meanwhile, the surrounding ligands on the clusters show doubly or triply paired steric interactions. The helical assembly is driven by van der Waals interactions through particle rotation and conformational matching. Furthermore, the heterodimeric clusters have a carrier lifetime that is roughly 65 times longer than that of the homodimeric clusters. Our findings suggest new approaches for increasing complexity in the structural design and engineering of precision in supercrystals.

Unconventional-Phase Crystalline Materials Constructed from Multiscale Building Blocks

Crystal phase, an intrinsic characteristic of crystalline materials, is one of the key parameters to determine their physicochemical properties. Recently, great progress has been made in the synthesis of nanomaterials with unconventional phases that are different from their thermodynamically stable bulk counterparts via various synthetic methods. A nanocrystalline material can also be viewed as an assembly of atoms with long-range order. When larger entities, such as nanoclusters, nanoparticles, and microparticles, are used as building blocks, supercrystalline materials with rich phases are obtained, some of which even have no analogues in the atomic and molecular crystals. The unconventional phases of nanocrystalline and supercrystalline materials endow them with distinctive properties as compared to their conventional counterparts. This Review highlights the state-of-the-art progress of nanocrystalline and supercrystalline materials with unconventional phases constructed from multiscale building blocks, including atoms, nanoclusters, spherical and anisotropic nanoparticles, and microparticles. Emerging strategies for engineering their crystal phases are introduced, with highlights on the governing parameters that are essential for the formation of unconventional phases. Phase-dependent properties and applications of nanocrystalline and supercrystalline materials are summarized. Finally, major challenges and opportunities in future research directions are proposed.

Enhancement of X-ray-Excited Red Luminescence of Chromium-Doped Zinc Gallate via Ultrasmall Silicon Carbide Nanocrystals

X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical probes due to being free of autofluorescence, while both their excitation and emission possess a high penetration efficacy in vivo. Herein, we report silicon carbide quantum dot sensitization of trivalent chromium-doped zinc gallate nanoparticles with enhanced near-infrared emission upon X-ray and UV-vis light excitation. We have found that a ZnGa2O4 shell is formed around the SiC nanoparticles during seeded hydrothermal growth, and SiC increases the emission efficiency up to 1 order of magnitude due to band alignment that channels the excited electrons to the chromium ion.

Self-assembly of colloidal inorganic nanocrystals: nanoscale forces, emergent properties and applications

The self-assembly of colloidal nanoparticles has made it possible to bridge the nanoscopic and macroscopic worlds and to make complex nanostructures. The nanoparticle-mediated assembly enables many potential applications, from biodetection and nanomedicine to optoelectronic devices. Properties of assembled materials are determined not only by the nature of nanoparticle building blocks, but also by spatial positions of nanoparticles within the assemblies. A deep understanding of nanoscale interactions between nanoparticles is a prerequisite to controlling nanoparticle arrangement during assembly. In this review, we present an overview of interparticle interactions governing their assembly in a liquid phase. Considerable attention is devoted to examples that illustrate nanoparticle assembly into ordered superstructures using different types of building blocks, including plasmonic nanoparticles, magnetic nanoparticles, lanthanide-doped nanophosphors, and quantum dots. We also cover the physicochemical properties of nanoparticle ensembles, especially those arising from particle coupling effects. We further discuss future research directions and challenges in controlling self-assembly at a level of precision that is most crucial to technology development.

Construction of Chiral, Helical Nanoparticle Superstructures: Progress and Prospects

Chiral nanoparticle (NP) superstructures, in which discrete NPs are assembled into chiral architectures, represent an exciting and growing class of nanomaterials. Their enantiospecific properties make them promising candidates for a variety of potential applications. Helical NP superstructures are a rapidly expanding subclass of chiral nanomaterials in which NPs are arranged in three dimensions about a screw axis. Their intrinsic asymmetry gives rise to a variety of interesting properties, including plasmonic chiroptical activity in the visible spectrum, and they hold immense promise as chiroptical sensors and as components of optical metamaterials. Herein, a concise history of the foundational conceptual advances that helped define the field of chiral nanomaterials is provided, and some of the major achievements in the development of helical nanomaterials are highlighted. Next, the key methodologies employed to construct these materials are discussed, and specific merits that are offered by each assembly methodology are identified, as well as their potential disadvantages. Finally, some specific examples of the emerging applications of these materials are discussed and some areas of future development and research focus are proposed.

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.

Self-assembly of anisotropic nanoparticles into functional superstructures

Self-assembly of colloidal nanoparticles (NPs) into superstructures offers a flexible and promising pathway to manipulate the nanometer-sized particles and thus make full use of their unique properties. This bottom-up strategy builds a bridge between the NP regime and a new class of transformative materials across multiple length scales for technological applications. In this field, anisotropic NPs with size- and shape-dependent physical properties as self-assembly building blocks have long fascinated scientists. Self-assembly of anisotropic NPs not only opens up exciting opportunities to engineer a variety of intriguing and complex superlattice architectures, but also provides access to discover emergent collective properties that stem from their ordered arrangement. Thus, this has stimulated enormous research interests in both fundamental science and technological applications. This present review comprehensively summarizes the latest advances in this area, and highlights their rich packing behaviors from the viewpoint of NP shape. We provide the basics of the experimental techniques to produce NP superstructures and structural characterization tools, and detail the delicate assembled structures. Then the current understanding of the assembly dynamics is discussed with the assistance of in situ studies, followed by emergent collective properties from these NP assemblies. Finally, we end this article with the remaining challenges and outlook, hoping to encourage further research in this field.