Endowing Perovskite Nanocrystals with Circularly Polarized Luminescence

Perovskite nanocrystals are attracting great interest due to their excellent photonic properties. Here, through a supramolecular self‐assembly approach, the perovskite nanocrystals (NCs) with a novel circularly polarized luminescence (CPL) are successfully endowed. It is found that the achiral perovskite NCs can coassemble with chiral gelator in nonpolar solvents, in which the gelator molecules modify the surface of the perovskite NCs. Through such cogelation, the molecular chirality can transfer to the NCs resulting in CPL signals with a dissymmetric factor (g_lum) up to 10^?3. Furthermore, depending on the molecular chirality of the gelator, the CPL sense can be selected and the mirror‐imaged CPL is obtained. Such gels can be further embedded into the polymer film to facilitate flexible CPL devices. It is envisaged that this approach will afford a new insight into the designing of the functional chiroptical materials.     

Selective Coassembly of Aromatic Amino Acids to Fabricate Hydrogels with Light Irradiation‐Induced Emission for Fluorescent Imprint

Controlling the structural parameters in coassembly is crucial for the fabrication of multicomponent functional materials. Here a proof‐of‐concept study is presented to reveal the α‐substituent effect of aromatic amino acids on their selective coassembly with bipyridine binders. With the assistance of X‐ray scattering technique, it is found that individual packing in the solid state as well as bulky effect brought by α‐substitution determines the occurrence of coassembly. A well‐performed hydrogels based on the complexation between certain aromatic amino acids and bipyridine units are successfully constructed, providing unprecedented smart materials with light irradiation‐triggered luminescence. Such hydrogels without the phase separation and photobleaching during light irradiation are able to behave fluorescent imprint materials. This study provides a suitable protocol in rationally designing amino acid residues of short peptides for fabricating self‐assembled multicomponent materials. In addition, this protocol is useful in screening potential functional materials on account of diverse self‐assembly behavior.     

Reconfigurable Chiral Self‐Assembly of Peptides through Control of Terminal Charges

Self‐assembly of chiral nanostructures is of considerable interest, since the ability to control the chirality of these structures has direct ramifications in biology and materials science. A new approach to design chiral nanostructures from self‐assembly of N‐(9‐fluorenylmethoxycarbonyl)‐protected phenylalanine‐tryptophan‐lysine tripeptides is reported. The terminal charges can induce helical twisting of the assembled β‐sheets, enabling the formation of well‐defined chiral nanostructures. The degree and direction of twisting in the β‐sheets can be precisely tailored through in situ pH and temperature modulations. This enables the assembly of reconfigurable chiral nanomaterials with easily adjustable size and handedness. These results offer new insight into the mechanism of helical twist formation, which may enable the precise assembly of highly dynamical materials with potential applications in biomedicine, chiroptics, and chiral sensing.     

Full‐Color Tunable Circularly Polarized Luminescent Nanoassemblies of Achiral AIEgens in Confined Chiral Nanotubes

Circularly polarized luminescent (CPL) materials are currently attracting great interest. While a chiral building is usually necessary in order to obtain CPL materials, here, this study proposes a general approach for fabricating 1D circularly polarized luminescent nanoassemblies from achiral aromatic molecules or aggregation‐induced emissive compounds (AIEgens). It is found that a C₃ symmetric chiral gelator can individually form hexagonal nanotube structures and encapsulate the guest molecules. When achiral AIEgens are encapsulated into the confined nanotubes via organogelation, the AIEgens will emit circularly polarized luminescence. Further, the direction of the CPL could be controlled by the supramolecular chirality of the nanotube. Remarkably, the approach is universal and various kinds of the AIEgens can be doped to show such property, providing a full‐color‐tunable circularly polarized luminescence.     

Photon Upconverted Circularly Polarized Luminescence via Triplet–Triplet Annihilation

Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high‐energy excitation results in low‐energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion—i.e., the conversion of low‐energy light into higher‐energy emission, with a wide variety of applications—has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher‐energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon‐upconverted CPL via the triplet–triplet annihilation mechanism, focusing on the amplified dissymmetry factor g_lum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.     

Helically assembled π-conjugated polymers with circularly polarized luminescence

We review the recent progress in the field of helically assembled π-conjugated polymers, focusing on aromatic conjugated polymers with interchain helical π-stacking that exhibit circularly polarized luminescence (CPL). In Part 1, we discuss optically active polymers with white-colored CPL and the amplification of the circular polarization through liquid crystallinity. In Part 2, we focus on the stimuli-responsive CPL that results from changes in the conformation and aggregation state of π-conjugated molecules and polymers. In Part 3, we discuss the self-assembly of achiral cationic π-conjugated polymers into circularly polarized luminescent supramolecular nanostructures with the aid of other chiral molecules.     

Supramolecular Nanostructures of Chiral Perylene Diimides with Amplified Chirality for High‐Performance Chiroptical Sensing

Chiral supramolecular nanostructures with optoelectronic functions are expected to play a central role in many scientific and technological fields but their practical use remains in its infancy. Here, this paper reports photoconductive chiral organic semiconductors (OSCs) based on perylene diimides with the highest electron mobility among the chiral OSCs and investigates the structure and optoelectronic properties of their homochiral and heterochiral supramolecular assemblies from bottom‐up self‐assembly. Owing to the well‐ordered supramolecular packing, the homochiral nanomaterials exhibit superior charge transport with significantly higher photoresponsivity and dissymmetry factor compared with those of their thin film and monomeric equivalents, which enables highly selective detection of circularly polarized light, for the first time, in visible spectral range. Interestingly, the heterochiral nanostructures assembled from co‐self‐assembly of racemic mixtures show extraordinary chiral self‐discrimination phenomenon, where opposite enantiomeric molecules are packed alternately into heterochiral architectures, leading to completely different optoelectrical performances. In addition, the crystal structures of homochiral and heterochiral nanostructures have first been studied by ab initio X‐ray powder diffraction analysis. These findings give insights into the structure–chiroptical property relationships of chiral supramolecular self‐assemblies and demonstrate the feasibility of supramolecular chirality for high‐performance chiroptical sensing.     

Chiral Shell Core–Satellite Nanostructures for Ultrasensitive Detection of Mycotoxin

Herein, the design of a DNA‐based chiral biosensor is described utilizing the self‐assembly of shell core–gold (Au) satellite nanostructures for the detection of mycotoxin, ochratoxin A (OTA). The assembly of core–satellite nanostructures based on OTA‐aptamer binding exhibits a strong chiral signal with an intense circular dichroism (CD) peak. The integrity of the assembly of core–satellite nanostructures is limited to some extent in the presence of different levels of OTA. Correspondingly, the chiral intensity of assembly is weakened with increasing OTA concentrations, allowing quantitative determination of the target. The developed chiral sensor shows an excellent linear relationship between the CD signal and concentrations of OTA in the range of 0.1–5 pg mL^?1 with a limit of detection as low as 0.037 pg mL^?1. The effectiveness of the biosensor in a sample of red wine is verified and a good recovery rate is obtained. These results suggest that the strategy has great potential for practical application.     

Uncovering the Circular Polarization Potential of Chiral Photonic Cellulose Films for Photonic Applications

Circularly polarized light (CPL) is central to photonic technologies. A key challenge lies in developing a general route for generation of CPL with tailored chiroptical activity using low‐cost raw materials suitable for scale‐up. This study presents that cellulose films with photonic bandgaps (PBG) and left‐handed helical sense have an intrinsic ability for circular polarization leading to PBG‐based CPL with extraordinary | g | values, well‐defiend handedness, and tailorable wavelength by the PBG change. Using such cellulose films, incident light ranging from near‐UV to near‐IR can be transformed to passive L‐CPL and R‐CPL with viewing‐side‐dependent handedness and | g | values up to 0.87, and spontaneous emission transformed to R‐CPL emission with | g | values up to 0.68. Unprecedented evidence is presented with theoretical underpinning that the PBG effect can stimulate the R‐CPL emission. The potential of cellulose‐based CPL films for polarization‐based encryption is illustrated. The evaporation‐induced self‐assembly coupled with nanoscale mesogens of cellulose nanocrystals opens new venues for technological advances and enables a versatile strategy for rational design and scalable manufacturing of organic and inorganic CPL films for photonic applications.     

Tailoring Chiroptical Activity of Iron Disulfide Quantum Dot Hydrogels with Circularly Polarized Light

Chiral inorganic nanomaterials have recently attracted significant attention because of their many important applications, such as in asymmetric catalysis and chiral sensing. Here, chiral iron disulfide quantum dots (FeS₂ QDs) are synthesized via chirality transfer using l/d ‐cysteine (Cys) as chiral ligands. The chiral FeS₂ QDs are coassembled with two gelators to produce a cogel (l ‐ or d ‐[Gel+FeS₂]) with a g‐factor value of ±0.06. Interestingly, the cogels display intense circularly polarized luminescence. More significantly, the degree of twisting (twist pitch) and the diameter of the cogels can be markedly regulated by illumination with circularly polarized light (CPL) in the ranges of 120–213 and 37–65 nm, respectively, which is caused by the CPL‐induced electron transfer. This research opens the way for the design of chiroptical devices with a wide range of functions and applications.     

The Role of Surface Groups in Dictating the Chiral-Solvent-Induced Assembly of Carbon Dots into Structures Exhibiting Circularly Polarized Luminescence

Here, the use of achiral nanoparticles and solvent-induced chirality transfer is combined for the making of large structures exhibiting chiroptical properties in the form of circularly polarized luminescence (CPL). The nanoparticles that the authors use are carbon dots (C-Dots) that are known for their bright luminescence and the ability to tune their surface moieties by using different precursors in their synthesis. Here, the result of adding the chiral solvent limonene into an aqueous solution of various C-Dots is explored, differentiated by their surface group. It is shown that only nitrogen-containing C-Dots with amine functional groups see the emergence of a CPL signal and the formation of a large fibrillar assembled structure. The various forces happening in the interface between the C-Dots and the limonene phase and the role of the amine groups in both the chirality transfer interactions and the interactions between C-Dots in the assembly process are discussed, whereas these two processes intertwine with each other. The ability to form fluorescent chiral structures exhibiting CPL from achiral nanoparticles and the understanding of the various interactions in this process are both important to the rationale design of any supramolecular chiral assemblies.     

Programmable Construction of Peptide‐Based Materials in Living Subjects: From Modular Design and Morphological Control to Theranostics

Self‐assembled nanomaterials show potential high efficiency as theranostics for high‐performance bioimaging and disease treatment. However, the superstructures of pre‐assembled nanomaterials may change in the complicated physiological conditions, resulting in compromised properties and/or biofunctions. Taking advantage of chemical self‐assembly and biomedicine, a new strategy of “in vivo self‐assembly” is proposed to in situ construct functional nanomaterials in living subjects to explore new biological effects. Herein, recent advances on peptide‐based nanomaterials constructed by the in vivo self‐assembly strategy are summarized. Modular peptide building blocks with various functions, such as targeting, self‐assembly, tailoring, and biofunctional motifs, are employed for the construction of nanomaterials. Then, self‐assembly of these building blocks in living systems to construct various morphologies of nanostructures and corresponding unique biological effects, such as assembly/aggregation‐induced retention (AIR), are introduced, followed by their applications in high‐performance drug delivery and bioimaging. Finally, an outlook and perspective toward future developments of in vivo self‐assembled peptide‐based nanomaterials for translational medicine are concluded.     

Dynamic Nanostructures from DNA‐Coupled Molecules,Polymers, and Nanoparticles

Dynamic and reconfigurable systems that can sense and react to physical and chemical signals are ubiquitous in nature and are of great interest in diverse areas of science and technology. DNA is a powerful tool for fabricating such smart materials and devices due to its programmable and responsive molecular recognition properties. For the past couple of decades, DNA‐based self‐assembly is actively explored to fabricate various DNA–organic and DNA–inorganic hybrid nanostructures with high‐precision structural control. Building upon past development, researchers have recently begun to design and assemble dynamic nanostructures that can undergo an on‐demand transformation in the structure, properties, and motion in response to various external stimuli. In this Review, recent advances in dynamic DNA nanostructures, focusing on hybrid structures fabricated from DNA‐conjugated molecules, polymers, and nanoparticles, are introduced, and their potential applications and future perspectives are discussed.     

Self‐Assembly of Functional Molecules into 1D Crystalline Nanostructures

Self‐assembled functional nanoarchitectures are employed as important nanoscale building blocks for advanced materials and smart miniature devices to fulfill the increasing needs of high materials usage efficiency, low energy consumption, and high‐performance devices. One‐dimensional (1D) crystalline nanostructures, especially molecule‐composed crystalline nanostructures, attract significant attention due to their fascinating infusion structure and functionality which enables the easy tailoring of organic molecules with excellent carrier mobility and crystal stability. In this review, we discuss the recent progress of 1D crystalline self‐assembled nanostructures of functional molecules, which include both a small molecule‐derived and a polymer‐based crystalline nanostructure. The basic principles of the molecular structure design and the process engineering of 1D crystalline nanostructures are also discussed. The molecular building blocks, self‐assembly structures, and their applications in optical, electrical, and photoelectrical devices are overviewed and we give a brief outlook on crucial issues that need to be addressed in future research endeavors.     

Native MicroRNA Targets Trigger Self‐Assembly of Nanozyme‐Patterned Hollowed Nanocuboids with Optimal Interparticle Gaps for Plasmonic‐Activated Cancer Detection

The modernized use of nucleic acid (NA) sequences to drive nanostructure self‐assembly has given rise to a new class of designed nanomaterials with controllable plasmonic functionalities for broad surface‐enhanced Raman scattering (SERS)‐based bioanalysis applications. Herein, dual usage of microRNAs (miRNAs) as both valuable cancer biomarkers and direct self‐assembly triggers is identified and capitalized upon for custom‐designed plasmonic nanostructures. Through strict NA hybridization of miRNA targets, Au nanospheres selectively self‐assemble onto hollowed Au/Ag alloy nanocuboids with ideal interparticle distances (≈2.3 nm) for optimal SERS signaling. The intrinsic material properties of the self‐assembled nanostructures further elevate miRNA detection performance via nanozyme catalytic SERS signaling cascades. This enables fM‐level miR‐107 detection limit within a clinically‐relevant range without any molecular target amplification. The miRNA‐triggered nanostructure self‐assembly approach is further applied in clinical patient samples, and showcases the potential of miR‐107 as a non‐invasive prostate cancer diagnostic biomarker. The use of miRNA targets to drive nanostructure self‐assembly holds great promise as a practical tool for miRNA detection in disease applications.     

Molecular Programming of Biodegradable Nanoworms via Ionically Induced Morphology Switch toward Asymmetric Therapeutic Carriers

Engineering biodegradable nanostructures with precise morphological characteristics is a key objective in nanomedicine. In particular, asymmetric (i.e., nonspherical) nanoparticles are desirable due to the advantageous effects of shape in a biomedical context. Using molecular engineering, it is possible to program unique morphological features into the self‐assembly of block copolymers (BCPs). However, the criteria of biocompatibility and scalability limit progress due to the prevalence of nondegradable components and the use of toxic solvents during fabrication. To address this shortfall, a robust strategy for the fabrication of morphologically asymmetric nanoworms, comprising biodegradable BCPs, has been developed. Modular BCPs comprising poly (ethylene glycol)‐block‐poly(caprolactone‐gradient‐trimethylene carbonate) (PEG?PCLgTMC), with a terminal chain of quaternary ammonium‐TMC (PTMC‐Q), undergo self‐assembly via direct hydration into well‐defined nanostructures. By controlling the solution ionic strength during hydration, particle morphology switches from spherical micelles to nanoworms (of varying aspect ratio). This ionically‐induced switch is driven by modulation of chain packing with salts screening interchain repulsions, leading to micelle elongation. Nanoworms can be loaded with cytotoxic cargo (e.g., doxorubicin) at high efficiency, preferentially interact with cancer cells, and increase tumor penetration. This work showcases the ability to program assembly of BCPs and the potential of asymmetric nanosystems in anticancer drug delivery.     

Encoded Multichromophore Response for Simultaneous Label‐Free Detection

The self‐assembly of molecularly precise nanostructures is widely expected to form the basis of future high‐speed integrated circuits, but the technologies suitable for such circuits are not well understood. In this work, DNA self‐assembly is used to create molecular logic circuits that can selectively identify specific biomolecules in solution by encoding the optical response of near‐field coupled arrangements of chromophores. The resulting circuits can detect label‐free, femtomole quantities of multiple proteins, DNA oligomers, and small fragments of RNA in solution via ensemble optical measurements. This method, which is capable of creating multiple logic‐gate–sensor pairs on a 2 × 80 × 80‐nm DNA grid, is a step toward more sophisticated nanoscale logic circuits capable of interfacing computers with biological processes.     

Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing

Herein an approach to controlling the pore size of mesoporous carbon thin films from metal‐free polyacrylonitrile‐containing block copolymers is described. A high‐molecular‐weight poly(acrylonitrile‐block‐methyl methacrylate) (PAN‐b‐PMMA) is synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The authors systematically investigate the self‐assembly behavior of PAN‐b‐PMMA thin films during thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as‐spin‐coated PAN‐b‐PMMA is microphase‐separated into uniformly spaced globular nanostructures, and these globular nanostructures evolve into various morphologies after thermal or solvent annealing. Surprisingly, through thermal annealing and subsequent pyrolysis of PAN‐b‐PMMA into mesoporous carbon thin films, the pore size and center‐to‐center spacing increase significantly with thermal annealing temperature, different from most block copolymers. In addition, the choice of solvent in solvent annealing strongly influences the block copolymer nanostructure and the pore size of mesoporous carbon thin films. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon thin films by tuning thermal or solvent annealing conditions, instead of synthesizing a series of block copolymers of various molecular weights and compositions.     

Hierarchical Multicomponent Inorganic Metamaterials: Intrinsically Driven Self‐Assembly at the Nanoscale

Increasingly intricate in their composition and structural organization, hierarchical multicomponent metamaterials with nonlinear spatially reconfigurable functionalities challenge the intrinsic constraints of natural materials, revealing tremendous potential for the advancement of biochemistry, nanophotonics, and medicine. Recent breakthroughs in high‐resolution nanofabrication utilizing ultranarrow, precisely controlled ion or laser beams have enabled assembly of architectures of unprecedented structural and functional complexity, yet costly, time‐ and energy‐consuming high‐resolution sequential techniques do not operate effectively at industry‐required scale. Inspired by the fictional Baron Munchausen's fruitless attempt to pull himself up, it is demonstrated that metamaterials can undergo intrinsically driven self‐assembly, metaphorically pulling themselves up into existence. These internal drivers hold a key to unlocking the potential of metamaterials and mapping a new direction for the large‐area, cost‐efficient self‐organized fabrication of practical devices. A systematic exploration of these efforts is presently missing, and the driving forces governing the intrinsically driven self‐assembly are yet to be fully understood. Here, recent progress in the self‐organized formation and self‐propelled growth of complex hierarchical multicomponent metamaterials is reviewed, with emphasis on key principles, salient features, and potential limitations of this family of approaches. Special stress is placed on self‐assembly driven by plasma, current in liquid, ultrasonic, and similar highly energetic effects, which enable self‐directed formation of metamaterials with unique properties and structures.     

Active Self‐Assembly of Train‐Shaped DNA Nanostructures via Catalytic Hairpin Assembly Reactions

Biomolecular self‐assembly is a powerful approach for fabricating supramolecular architectures. Over the past decade, a myriad of biomolecular assemblies, such as self‐assembly proteins, lipids, and DNA nanostructures, have been used in a wide range of applications, from nano‐optics to nanoelectronics and drug delivery. The method of controlling when and where the self‐assembly starts is essential for assembly dynamics and functionalization. Here, train‐shaped DNA nanostructures are actively self‐assembled using DNA tiles as artificial “carriages,” hairpin structures as “couplers,” and initiators of catalytic hairpin assembly (CHA) reactions as “wrenches.” The initiator wrench can selectively open the hairpin couplers to couple the DNA tile carriages with high product yield. As such, DNA nanotrains are actively prepared with two, three, four, or more carriages. Furthermore, by flexibly modifying the carriages with “biotin seats” (biotin‐modified DNA tiles), streptavidin “passengers” are precisely arranged in corresponding seats. The applications of the CHA‐triggered self‐assembly mechanism are also extended for assembling the large DNA origami dimer. With the creation of 1D architectures established, it is thought that this CHA‐triggered self‐assembly mechanism may provide a new element of control for complex autonomous assemblies from a variety of starting materials with specific sites and times.