Circularly Polarized Luminescence in Nanoassemblies: Generation, Amplification, and Application

Tunable circularly polarized electroluminescence behaviors from chiral co-assembled conjugated liquid crystal polymers

Chiral co-assembly strategy has proven effective in increasing the dissymmetry factor (gEL) of the emitting layers (EMLs) in circularly polarized organic light-emitting diodes (CP-OLEDs). Therefore, it is crucial to investigate the molecular structures that facilitate chiral co-assembly for further amplification of circularly polarized electroluminescence (CP-EL) signals. In this study, three types of achiral conjugated liquid crystal (LC) polymers (PFPh, PFNa and PFPy) and chiral binaphthyl-based polymer inducers (R/S-FO) were synthesized to construct corresponding chiral co-assemblies (R/S-FO)0.1-(PFPh/Na/Py)0.9 as EMLs for CP-OLEDs through strong intermolecular π-π stacking interactions. Interestingly, these resulting chiral co-assembled EMLs exhibited tunable CP-EL behaviors caused by the different conjugation linkers of LC polymers. Among them, the deep blue devices based on (R/S-FO)0.1-(PFNa)0.9 emitted the strongest CP-EL signals (|gEL| = 0.014, Lmax = 3039 cd m-2, CEmax = 1.16 cd A-1). It is attributed to the formation of ordered helical nanofibers facilitated by the excellent intermolecular compatibility due to the same naphthyl moieties in PFNa and R/S-FO. This study provides novel perspectives for developing high-performance CP-EL materials in chiral co-assembly systems.

Spin-Valley-Locked Electroluminescence for High-Performance Circularly Polarized Organic Light-Emitting Diodes

Circularly polarized (CP) organic light-emitting diodes (OLEDs) have attracted attention in potential applications, including novel display and photonic technologies. However, conventional approaches cannot meet the requirements of device performance, such as high dissymmetry factor, high directionality, narrowband emission, simplified device structure, and low costs. Here, we demonstrate spin-valley-locked CP-OLEDs without chiral emitters but based on photonic spin-orbit coupling, where photons with opposite CP characteristics are emitted from different optical valleys. These spin-valley-locked OLEDs exhibit a narrowband emission of 16 nm, a high external quantum efficiency of 3.65%, a maximum luminance of near 98,000 cd/m2, and a gEL of up to 1.80, which are among the best performances of active single-crystal CP-OLEDs, achieved with a simple device structure. This strategy opens an avenue for practical applications toward three-dimensional displays and on-chip CP-OLEDs.

An effective orange-red solution-processed circularly polarized organic light-emitting diode

A pair of circularly polarized thermally activated delayed fluorescence (CP-TADF) materials (R)-ad-PXZ/(S)-ad-PXZ were obtained, which show orange-red emission at 602 nm and clear chiroptical properties both in solution and the solid state. The solution processable circularly polarized device exhibits the maximum external quantum efficiency of 9.0% and gEL value of 10-3.

Enhanced Asymmetric Circularly Polarized Luminescence in Self-Organized Helical Superstructures Enabled by Macro-Chiral Liquid Crystal Quantum Dots

Circularly polarized luminescent (CPL) materials have garnered considerable interest for a variety of advanced optical applications including 3D imaging, data encryption, and asymmetric catalysis. However, the development of high-performance CPL has been hindered by the absence of simple synthetic methods for chiral luminescent emitters that exhibit both high quantum yields and dissymmetry factors. In this study, we present an innovative approach for the synthesis of macro-chiral liquid crystal quantum dots (Ch-QDs/LC) and their CPL performance enhancement through doping with 4-cyano-4'-pentylbiphenyl (5CB), thus yielding a CPL-emitting generator (CEG). The Ch-QDs/LCs were synthesized, and their surfaces functionalized with a chiral mesogenic ligand, specifically cholesteryl benzoate, anchored via a lipoic acid linker. Under the regulation of chiral 2S-Zn2+ coordination complexes, the chiral LC encapsulation process promotes coordinated ligand substitution, resulting in an exceptional quantum yield of 56.3%. This is accompanied by high absorption dissymmetry factor (gabs) and luminescence dissymmetry factor (glum) values ranging from 10-3 to 10-2, surpassing most reported dissymmetry factors by at least an order of magnitude. The modular Ch-QDs/LCs demonstrate the ability to transfer chirality to the surrounding medium efficiently and manifest macro-chiral characteristics within a nematic LC matrix. Utilizing Ch-QDs/LC as an effective CPL emitter within achiral 5CB matrices enabled the system to achieve a maximum glum value of 0.35. The resultant CEG device acted as a direct CPL source, initiating enantioselective photopolymerization.

Helix-Sense-Selective Memory Polymerization of Biphenylylacetylenes Bearing Carboxy and Amino Groups in Water

We report the helix-sense-selective memory polymerization (HSMP) of achiral biphenylylacetylenes bearing carboxy and amino pendant groups in the presence of basic and acidic chiral guests in water, respectively. The HSMP proceeds in a highly helix-sense-selective manner driven by noncovalent chiral ionic interactions between the monomers and guests under kinetic control, producing the one-handed helical polymers with a static memory of helicity in one-pot during the polymerization in a very short time, accompanied by amplification of asymmetry. The carboxy-bound helicity-memorized polymer self-assembles into a cholesteric liquid crystal in concentrated water, in which a variety of basic achiral fluorophores further co-assembles to form supramolecular helical aggregates that exhibit an induced circularly polarized luminescence in a color tunable manner.

Three-Level Chirality Transfer and Amplification in Liquid Crystal Supramolecular Assembly for Achieving Full-Color and White Circularly Polarized Luminescence

Chiral liquid crystal supramolecular assembly provides an ideal strategy for constructing excellent circularly polarized luminescence (CPL) materials. However, the chirality transfer in chiral liquid crystals normally occurs at two levels from the configurational chirality to the supramolecular phase chirality. The more precise and more levels of chirality transmission are fascinating but remain challenging. The present work reports the first success of three-level chirality transfer and amplification from configurationally point chirality of small molecules to conformationally helical chirality of helical polymers and finally to supramolecular phase chirality of cholesteric liquid crystals composed of chiral nonfluorescent polymers (P46) and nematic liquid crystals. Noticeably, the helical twisting power of P46 is five-fold larger than its monomer. Full-color and white CPL with maximum luminescence dissymmetry factor up to 1.54 and photoluminescence quantum yield up to 63.8% are realized utilizing helical supramolecular assembly combined with selective reflection mechanism. Also significantly, the electrically stimuli-responsive CPL switching device as well as anti-counterfeiting security, information encryption, and chiral logic gate applications are developed. This study deepens the understanding of chirality transfer and amplification across different hierarchical levels.

Ultra-Narrowband Circularly Polarized Luminescence from Multiple 1,4-Azaborine-Embedded Helical Nanographenes

In this manuscript we present a strategy to achieve ultranarrowband circularly polarized luminescence (CPL) from multiple 1,4-azaborine-embedded helical nanographenes. The impact of number and position of boron and nitrogen atoms in the rigid core of the molecule on optical properties─including absorption and emission maxima, photoluminescence quantum yield, Stokes shift, excited singlet-triplet energy gap and full width at half-maximum (fwhm) for CPL and fluorescence─was investigated. The molecules reported here exhibits ultranarrowband fluorescence (fwhm 16-17.5 nm in toluene) and CPL (fwhm 18-19 nm in toluene). To the best of our knowledge, this is among the narrowest CPL for any organic molecule reported to date. Quantum chemical calculations, including computed CPL spectra involving vibronic contributions, provide valuable insights for future molecular design aimed at achieving narrowband CPL.

Fluorescent Dye-Based Chiral Crystalline Organic Salt Networks for Circularly Polarized Luminescence

A facile and general strategy is developed herein for the construction of circularly polarized luminescence (CPL) materials with simultaneously high fluorescence quantum efficiency (Φ) and large luminescence dissymmetry factor (glum). The self-assembly of fluorescent dye, disodium 4,4'-bis(2-sulfonatostyryl)biphenyl (CBS), with chiral diamines such as (R,R)/(S,S)-1,2-diaminocyclohexane (R/S-DACH) and R/S-1,2-diaminopropane (R/S-DAP), produces four chiral crystalline organic salt networks (COSNs). These as-synthesized organic salts emit strong blue-color CPL upon excitation, with both high Φ and glum values of up to 79% and 0.022. The well-defined molecular structures and arrangements of CBS are directly observed through single crystal X-ray analysis, offering crucial information regarding the origins of high-efficiency CPL performance. The chirality of amine is effectively transferred to CBS and further amplified to the supramolecular structure by multiple hydrogen bonding and π-π stacking interactions, giving rise to the large glum factors; meanwhile, the fixation and the ordered arrangement of CBS by these multiple interactions empower efficient suppression of molecular motions, facilitating strong fluorescence. This work can inspire the assembly of CPL organic materials with high Φ and glum via charge-assisted hydrogen bonds between fluorescent dyes and chiral inducers. It also offers important insight into the structural origins of supramolecular chirality and CPL performance.

Liquid crystal-mediated self-assembly of copper nanoclusters with induced circular dichroism and amplified circularly polarized luminescence

Elucidating the mechanism of chiral transfer is key to regulating chiral expression and generalizing the structure-property relationship of chiral functional systems. However, it is still an important challenge to select novel building blocks to achieve chiral induction, chiral transfer and chiral modulation. Liquid crystals (LCs) can be considered as promising smart soft materials due to their responsiveness and adaptability. Confining chiral metal nanoclusters (NCs) in an achiral LC phase to construct chiral LCs provides an expanded strategy for the self-assembly of chiral metal NCs in different matrices. Herein, chiral glutathione-stabilized copper NCs (G-SH-Cu NCs)/polyoxyethylene tert-octylphenyl ether (TX-100) LCs were constructed and systematically investigated. The results showed that the introduction of G-SH-Cu NCs into TX-100 LCs induced the generation of supramolecular chirality. More interestingly, the circular dichroism (CD) handedness can be controlled by changing the amount of TX-100 or G-SH-Cu NCs; when the ratio of G-SH-Cu NCs and TX-100 was proportionally matched, the strength of the noncovalent interactions was sufficient to induce chiral inversion. Meanwhile, TX-100 LCs provide effective confinement of G-SH-Cu NCs, which improves the expression of asymmetry at the aggregation level and induces a 2-fold enhancement of the circularly polarized luminescence (CPL) signal. This work realizes the spatial amplification of chirality through dopants in LCs, which provides an effective method for accurately regulating the supramolecular chirality of metal NCs in the LC phase.

Upconversion circularly polarized luminescence of cholesteric liquid crystal polymer networks with NaYF4:Yb,Tm UCNPs

Upconversion circularly polarized luminescence (UC-CPL) exhibits promising potential for application for anti-counterfeiting and displays. Upconversion nanoparticles (UCNPs), NaYF4:Yb,Tm, with uniform morphology and high crystallinity, were prepared via a simple solvothermal method. These UCNPs were embedded into cholesteric liquid crystal polymer network (CLCN) films. The UC-CPL performance of these films was investigated using left- and right-handed circular polarizers. After calibration, the |gcallum| values (up to 0.33) were obtained for the free-standing CLCN-UCNPs films, while a |gcallum| value of 0.43 was achieved for the CLCN-UCNPs-coated PET film. Moreover, a combined system comprising a PMMA-UCNPs layer and a CLCN layer yielded an ultra-large |gcallum| value of up to 1.73. Flexible and colourful patterned CLCN films were fabricated using photomasks, offering potential applications in anti-counterfeiting. This study not only successfully prepared UC-CPL-active materials based on CLCNs and UCNPs, but also demonstrated the chiral filtering effect of CLCN films in upconversion luminescent materials.

Chiral Co-assembly Based on a Stimuli-Responsive Polymer towards Amplified Full-Color Circularly Polarized Luminescence

Stimuli-responsive circularly polarized luminescence (CPL) materials have been attaching wide attention in the field of optical information storage and encryption, while still facing the challenge of the realization of high luminescence dissymmetry factors (glum). This work presents a pair of stimuli-responsive chiral co-assemblies P7R3 and P7S3 by combining polymer PFIQ containing iso-quinoline units with chiral inducers. The obtained chiral co-assemblies can reversibly undergo significant modification in CPL behavior under trifluoroacetic acid (TFA) fumigation and annealing treatment, with the |glum| values exhibiting a reversible shift between 0.2 and 0.3. Moreover, the chiral co-assemblies before TFA fumigating can effectively induce achiral emitters to generate intense full-color CPL signals through CPL energy transfer (CPL-ET), with the corresponding |glum| values larger than 0.2. Moreover, information encryption and decryption as well as a multi-level logic gates application are achieved by leveraging the reversible stimuli-responsive CPL activity of the chiral co-assembly. This work provides a new perspective for the construction of stimuli-responsive chiral luminescent materials with large |glum| values and the activation of CPL behavior in achiral emitters.

Tuning the circularly polarized luminescence in homoleptic and heteroleptic chiral CrIII complexes

A series of highly emissive inert and chiral CrIII complexes displaying positive and negative circularly polarized luminescence (CPL) within the near-infrared (NIR) region at room temperature have been prepared and characterized to decipher the effect of ligand substitution on the photophysical properties, more specifically on the chiroptical properties. The helical homoleptic [Cr(dqp-R)2]3+ (dqp = 2,6-di(quinolin-8-yl)pyridine; R = Ph, ≡-Ph, DMA, ≡-DMA (DMA = N,N-dimethylaniline)) and heteroleptic [Cr(dqp)(L)]3+ (L = 4-methoxy-2,6-di(quinolin-8-yl)pyridine (dqp-OMe) or L = N 2,N 6-dimethyl-N 2,N 6-di(pyridin-2-yl)pyridine-2,6-diamine (ddpd)) molecular rubies were synthesized as racemic mixtures and then resolved and isolated into their respective pure PP and MM enantiomeric forms by chiral stationary phase HPLC. The corresponding enantiomers show two opposite polarized emission bands within the 700-780 nm range corresponding to the characteristic metal-centered Cr(2E'→4A2) and Cr(2T1 '→4A2) transitions with large g lum ranging from 0.14 to 0.20 for the former transition. In summary, this study reports the rational use of different ligands on CrIII and their effect on the chiroptical properties of the complexes.

Loading Dyes into Chiral Cd/Zn-Metal-Organic Frameworks for Efficient Full-Color Circularly Polarized Luminescence

Host-guest chemistry of chiral metal-organic frameworks (MOFs) has endowed them with circularly polarized luminescence (CPL), it is still limited for MOFs to systematically tune full-color CPL emissions and sizes. This work directionally assembles the chiral ligands, metal sites and organic dyes to prepare a series of crystalline enantiomeric D/L-Cd/Zn-n MOFs (n=1~5, representing the adding amount of dyes), where D/L-Cd/Zn with the formula of Cd2(D/L-Cam)2(TPyPE) and Zn2(D/L-Cam)2(TPyPE) (D/L-Cam=D/L-camphoric acid, TPyPE=4,4',4'',4'''-(1,2-henediidenetetra-4,1-phenylene)tetrakis[pyridine]) were used as the chiral platforms. The framework-dye-enabled emission and through-space chirality transfer facilitate D/L-Cd/Zn-n bright full-color CPL activity. The ideal yellow CPL of D-Cd-5 and D-Zn-4, with |glum| as 4.9 × 10-3 and 1.3×10-3 and relatively high photoluminescence quantum yield of 40.79 % and 45.40 %, are further assembled into a white CPL light-emitting diode. The crystal sizes of D/L-Cd/Zn-n were found to be strongly correlated to the types and additional amounts of organic dyes, that the positive organic dyes allow for the preparation of > 7 mm bulks and negative dyes account for sub-20 μm particles. This work opens a new avenue to fabricate full-color emissive CPL composites and provides a potentially universal method for controlling the size of optical platforms.

Efficient multicolour and white circularly polarized luminescence from liquid crystalline polymer networks

Twelve liquid crystalline polymer network films were fabricated through photopolymerization of cholesteric liquid-crystalline mixtures containing two aggregation-induced emissive-active luminogens. The films exhibit multicolour and white circularly polarized luminescence with dissymmetry factors up to 0.85 and fluorescence quantum yields up to 90%.

Stacking Transformation-Triggered Circularly Polarized Luminescence Reversion in γ-Cyclodextrins-Pyrene Co-Assembly

Considerable attention has been directed towards cyclodextrins (CDs) in the creation of co-assembled CPL-active materials, owing to their intrinsic chiral host cavities and synergistic host-guest interactions. However, achieving reversed CPL emission regulation with single-handedness CDs moiety poses a significant challenge. In this study, we have devised a series of γ-CD-based host-guest complexes comprising dual pyrene imidazolium derivatives with multiple linkers, which exhibit reversed circularly polarized emission. We have uncovered that the transformation of excimer stacking within γ-CD/pyrene complexes contributes to the inverted CPL emissions originating from a single-handed chiral host. This research elucidates the phenomenon of (+)- and (-)-circularly polarized excimer emission (CPEE) within γ-CD, arising from right- and left-handed stacking conformations, respectively.

Flexible organic crystals with multi-stimuli-responsive CPL for broadband multicolor optical waveguides

Flexible organic crystals, capable of transmitting light and responding to various external stimuli, are emerging as a new frontier in optoelectronic materials. They hold immense potential for applications in molecular machines, sensors, displays, and intelligent devices. Here, we report on flexible organic crystals based on single-component enantiomeric organic compounds, demonstrating multi-stimuli-responsive circularly polarized light (CPL). These crystals exhibit remarkable elasticity, responsiveness to light and acid vapors, and tunable circularly polarized optical signals. Upon exposure to acid vapors, the fluorescence of the crystals shifts from initial yellow emission to green emission, attributable to the protonation-induced inhibition of excited-state intramolecular proton transfer. Under UV irradiation, the fluorescence emission undergoes a red-shift, resulting from the molecular transformation from an enol configuration to a ketone configuration. Notably, both processes are reversible and can be restored under daylight. The integration of reversible fluorescence changes under light and acid vapors stimuli, CPL signals, and flexible optical waveguides within a single crystal paves the way for the application of organic crystals as all-organic chiral functional materials.

The promise of chiral electrocatalysis for efficient and sustainable energy conversion and storage: a comprehensive review of the CISS effect and future directions

The integration of chirality, specifically through the chirality-induced spin selectivity (CISS) effect, into electrocatalytic processes represents a pioneering approach for enhancing the efficiency of energy conversion and storage systems. This review delves into the burgeoning field of chiral electrocatalysis, elucidating the fundamental principles, historical development, theoretical underpinnings, and practical applications of the CISS effect across a spectrum of electrocatalytic reactions, including the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). We explore the methodological advancements in inducing the CISS effect through structural and surface engineering and discuss various techniques for its measurement, from magnetic conductive atomic force microscopy (mc-AFM) to hydrogen peroxide titration. Furthermore, this review highlights the transformative potential of the CISS effect in addressing the key challenges of the NRR and CO2RR processes and in mitigating singlet oxygen formation in metal-air batteries, thereby improving their performance and durability. Through this comprehensive overview, we aim to underscore the significant role of incorporating chirality and spin polarization in advancing electrocatalytic technologies for sustainable energy applications.

Color-tunable and white circularly polarized luminescence through confining guests into chiral MOFs

Herein, chiral metal-organic frameworks (MOFs), DCF-20 and LCF-20, were utilized as matrices for both chirality transfer and energy transfer. HBT1@MOFs and HBT2@MOFs emit excitation-dependent circularly polarized luminescence (CPL) due to excited-state intramolecular proton transfer (ESIPT). HBT1/C152/NIR@MOFs exhibit full-color and white CPL. The luminescence dissymmetry factors (glum) were significantly increased, benefiting from the efficient chirality space transfer and high luminescence efficiency.

Two-Photon-Excited Fluorescent Tetrabranched Triphenylborane Featuring the Cooperative Effect of Branching in Two-Photon Absorption

We here disclose a new type of two-photon-excited fluorescent triarylborane, tetrabranched triphenylborane 1, which contains four electron-donating [4-(N,N-diphenylamino)phenyl]ethynyl branches at 2,6-positions of two phenyl rings. The cross section of 1 reaches 275 GM (1 GM = 10-50 cm4 s photon-1) in tetrahydrofuran. Compared with dibranched triphenylborane 2, the 2-fold increase in the number of electron-donating branches induces a 3.6-fold increase in the two-photon absorption cross section, suggesting the great cooperative effect of branching in the enhancement of two-photon absorption.

A Halogen-Bonded Fluorescent Molecular Photoswitch: Transition from 3D Cubic Lattice to 1D Helical Superstructure for Polarization Inversion of Circularly Polarized Luminescence

The fabrication of materials that can switch between circularly polarized luminescence (CPL) signals is both essential and challenging. Here, two new halogen-bonded fluorescent molecular photoswitches, namely, HB-switch 1 and HB-switch 2, containing α-cyano-substituted diarylethene compounds with different end groups were developed. Upon exposure to specific UV or visible light wavelengths, they exhibited controllable and reversible Z/E photoisomerization. When these switches were integrated into blue-phase liquid crystals (BPLCs), the temperature range of BP significantly expanded. Notably, the BP system incorporating HB-switch 1 exclusively achieved reversible polarization inversion of CPL signals under irradiation with specific UV/Visible light and during cooling/heating. The photo/thermal dual-response behavior of the CPL signals can be attributed to the phase transition from a high-symmetry 3D BP Icubic lattice to a low-symmetry 1D helical superstructure induced by the Z/E photoisomerization of HB-switch 1 and temperature changes. This study underscores the significance of employing halogen-bond assembly strategies to design materials with switchable CPL signals, opening new possibilities for CPL-active systems.

Chiral Co-Assembly with Narrowband Multi-Resonance Characteristics for High-Performance Circularly Polarized Organic Light-Emitting Diodes

A promising kind of ternary chiral co-assemblies with high PLQY, large dissymmetry factor (glum), and narrowband multi-resonance characteristics are achieved by codoped-thermal annealing treatments of achiral luminescent polymer F8BT, chiral inducers R/S-5011, and achiral FRET acceptor DBN-ICZ. The optimized co-assemblies (F8BT)0.9-(R/S-5011)0.1-(DBN-ICZ)0.005 display narrowband yellow emission with full-width half maximum (FWHM) of 37 nm, PLQY of 79%, and intense CPL signals with |glum| of up to 0.26. Meaningfully, solution-processed CP-OLEDs by using those ternary chiral co-assemblies as emitting layer are successfully fabricated, which display yellow circularly polarized electroluminescence (CPEL) with EQEmax of 4.6% and gEL of up to 0.16. The corresponding Q-factor could reach up to 7.36 × 10-3, which is the highest of all the reported CP-OLEDs. Moreover, the devices also exhibit excellent comprehensive device performance with low Von of 7.0 V, high Lmax of about 25 000 cd m-2, extremely low efficiency roll-off with EQE of 4.3% at 10 000 cd m-2, as well as narrowband EL with FWHM of only 39 nm. The proposed ternary co-assembly strategy in fabricating CP-OLED provides the possibility to achieve high comprehensive device performance such as balancing high EQE and large gEL value, as well as narrowband emission, high brightness and low efficiency roll-off simultaneously.

Achiral Solvent Inversed Helical Pathway and Cosolvent Controlled Excited-State "Majority Rule" in Enantiomeric Dansulfonamide Assemblies

Achiral solvents are commonly utilized to induce the self-assembly of chiral molecules. This study demonstrates that achiral solvents can trigger helicity inversion in the assemblies of dansyl amphiphiles and control the excited-state "majority rule" in assemblies composed of pure enantiomers, through variation of the cosolvent ratio. Specifically, enantiomers of dansyl amphiphiles self-assemble into helical structures with opposite handedness in methanol (MeOH) and acetonitrile (MeCN), together with inversed circular dichroism and circularly polarized luminescence (CPL) signals. When a mixture of MeOH and MeCN is employed, the achiral cosolvents collectively affect the CPL of the assemblies in a way similar to that of "mixed enantiomers". The dominant cosolvent governs the CPL signal. As the cosolvent composition shifts from pure MeCN to MeOH, the CPL signals undergo a significant inversion and amplification, with two maxima observed at ≈20% MeOH and 20% MeCN. This study deepens the comprehension of how achiral solvents modulate helical nanostructures and their excited-state chiroptical properties.

Supramolecular assembly of dendronized diacetylenes into thermoresponsive chiral fibers and their covalent fixation through topochemical polymerization

By combination of dendritic topological structures with photopolymerizable diacetylene, here we report on supramolecular chiral assembly of the dendronized diacetylenes in water. These dendronized diacetylenes are constituted with three-fold dendritic oligoethylene glycols (OEGs), bridged with a dipeptide from phenylalanine and glycine. These dendronized amphiphiles exhibit intensive propensity to aggregate in water and form helical fibers, which show characteristic thermoresponsive behavior with phase transition temperatures dominated by hydrophilicity of the dendritic OEGs. Topochemical polymerization of these supramolecular fibers through UV irradiation transfers them into the covalent helical dendronized polydiacetylenes. Chirality of these dendronized polydiacetylenes can be mediated through the thermally-induced phase transitions, but is also intriguingly dependent on vortex via stirring. Through stirring the solutions, chiralities of the dendronized polydiacetylenes are inverted, which can be reversibly recovered after keeping still the solution. Hydrogels are formed from these dendronized diacetylenes through concentration-enhanced interactions between the supramolecular fibers. Their mechanical properties can be greatly increased through thermally-enhanced interactions between the fibers with storage moduli increased from 20 Pa to a few hundred Pa. In addition, through photo-polymerization, the supramolecular fibers are transferred into covalent dendronized polydiacetylenes, and the corresponding hydrogels show much improved mechanical properties with storage moduli about 10 kPa.

Self-Standing Chiral Covalent Organic Framework Thin Films with Full-Color Tunable Guest-Induced Circularly Polarized Luminescence

Exploring self-standing chiral covalent organic framework (COF) thin films with controllable circularly polarized luminescence (CPL) is of paramount significance but remains a challenging task. Herein, we demonstrate the first example of self-standing chiral COF films employing a polymerization-dispersion-filtration strategy. Pristine, low-quality chiral COF films were produced by interfacial polymerization and then re-dispersed into COF colloidal solutions. Via vacuum assisted assembly, these COF colloids were densely stacked and assembled into self-standing, pure chiral COF films (L-/D-CCOF-F) that were transparent, smooth, crack-free and highly crystalline. These films were tunable in thicknesses, areas, and roughness, along with strong diffuse reflectance circular dichroism (DRCD) and cyan CPL signals, showing an intrinsic luminescence asymmetric factor (glum) of ~4.3×10-3. Furthermore, these COF films served as host adsorbents to load various achiral organic dye guests through adsorption. The effective chiral transfer and energy transfer between CCOF-F and achiral fluorescent dyes endowed the dyes with strong chirality and tunable DRCD, resulting in intense, full-color-tunable solid-state CPL. Notably, the ordered arrangement of dye guest molecules within the preferentially oriented chiral pores of CCOF-F contributed to an amplified |glum| factor of up to 7.2×10-2, which is state-of-the-art for COF-based CPL materials. This work provides new insights into the design and fabrication of self-standing chiral COF films, demonstrating their great potential for chiroptical applications.

Amplification and Attenuation of Asymmetry via Kinetically Controlled Seed-Induced Supramolecular Polymerization

The amplification of asymmetry in supramolecular polymers has recently garnered significant attention. While asymmetry amplification has predominantly been explored under thermodynamic conditions, the kinetic aspect of this process unveils intriguing observations, yet is scarcely reported in the literature. Herein, drawing inspiration from macromolecular systems, we propose a novel strategy for enhancing asymmetry in supramolecular polymers through a seed-induced supramolecular polymerization approach under kinetic conditions, employing a naphthalene diimide-derived monomer (ANSG) for template-induced supramolecular polymerization, utilizing adenosine triphosphate (ATP) and pyrophosphate (PPi) as templates. A chiral seed comprising [ANSG-ATP]S effectively amplifies the overall supramolecular asymmetry when exposed to a mixture of achiral templates (PPi) and monomers (ANSG), owing to its efficient seeding characteristics under kinetic conditions. As a result of efficient co-operativity, conversely, employing an achiral seed [ANSG-PPi]S in a mixture of chiral templates (ATP) and monomers (ANSG) results in the attenuation of asymmetry, highlighting the effective modulation achievable through the seeding approach, an unprecedented observation in the field. Exploiting the efficient aggregation-induced emission enhancement (AIEE) of the resultant supramolecular polymers further extends the amplification and attenuation of circularly polarized luminescence (CPL) as a potential function.

Responsive circularly polarized ultralong room temperature phosphorescence materials with easy-to-scale and chiral-sensing performance

Circularly polarized room temperature phosphorescence materials represent a state-of-the-art frontier of optical materials and exhibit promising applications in various fields. Herein, we fabricate a series of full-color circularly polarized room temperature phosphorescence materials, based on anionic cellulose derivatives and achiral luminophores. The ionic achiral substituents promote the spontaneous formation of chiral helical structure of cellulose derivatives via the electrostatic repulsion effect. There are multiple interactions between anionic cellulose derivatives and the doped luminophores, thus the chirality is transferred to luminophores and the non-radiative transition is inhibited. The resultant materials can be easily processed into large-scale film and flexible 3D objects with repeatable folding and curling properties. In addition, their phosphorescence performance shows to be excitation-dependence, time-dependence, visible-light excitation, and multi-responsiveness to humidity, temperature as well as pH value. Importantly, they recognize many enantiomers in an instrument-free visual mode, including amino acids, hydroxyl acids, organic phosphate and hydrobenzoin. These results provide insights into design of advanced optical materials which can be applied in multilevel information handling and chiral sensing.

Supramolecular chirality capture in solvent monomer-based co-assemblies via in situ photopolymerization

Supramolecular assemblies with chirality inversion were developed using a co-assembly system comprising solvent monomers and a pyridine-cholesterol gelator. The polarity-dependent chiralities were captured in situ through photopolymerization, enabling the formation of multi-color circularly polarized luminescence films.

Chiral Tetrakis Eu(III) Complexes with Ammonium Cations for Improved Circularly Polarized Luminescence

Large dissymmetry factor of the circularly polarized luminescence (gCPL) was observed in ligand and coordination tuned chiral tetrakis europium (Eu(III)) complexes with ammonium cations. The gCPL value was estimated to be -1.54, which is the largest among chiral luminescent molecules. Through photophysical measurements, single crystal X-ray structural analyses and quantum chemical calculations, changes in the geometric and electronic structures were observed for a series of chiral tetrakis Eu(III) complexes which enhanced the gCPL value. The emission quantum yield and photosensitized energy transfer efficiencies of chiral Eu(III) complexes with ammonium cations were also larger than those of chiral Eu(III) complex with Cs+. Based on the systematic modifications and analyses for chiral tetrakis Eu(III) complex, effect of the ammonium cation on enhanced CPL brightness is reported.

Enhanced circularly polarized luminescence attained via self-assembly of heterochiral as opposed to homochiral dipeptides in water

Circularly polarized luminescence (CPL) is gaining interest across various disciplines, including materials science, pharmaceuticals, and sensing technologies. Organic molecules, due to their ease of synthesis and reduced toxicity, are a focus for achieving high dissymmetry values (g lum) in CPL. Here, we present a low molecular weight molecule (1), a dipeptide (Ala-Phe) covalently linked with tetraphenyl-ethylene (TPE), an Aggregation-Induced Emission luminophore (AIE-gen). Varying the stereochemistry of amino acid chiral centers, we synthesized homochiral 1-(l, l) & 1-(d, d) and heterochiral 1-(l, d) and 1-(d, l). In aqueous media, these molecules exhibit aggregation-induced chirality at the TPE chromophore. Heterochiral systems form sheet-like structures, displaying a bisignate induced circular dichroism signal and a good g lum value for CPL [7.5 (±0.04) × 10-3]. Conversely, homochiral systems adopt fibrillar morphology, exhibiting a monosignate induced circular dichroism signal with a lower dissymmetry value for CPL [1.3 (±0.05) × 10-3]. This study introduces the concept of chiroptical amplification, emphasizing enhanced CPL through heterochiral peptide-induced CPL compared to its homochiral counterpart, with an ON and OFF CPL signal at low and high temperature respectively.

Molecular ordering-enhanced circularly polarized luminescence of chiral 1,10-phenanthroline derivatives

2,9-Bis((1R,2S,5R)-2-isopropyl-5-methylcyclohexanoxy)-1,10-phenanthroline [2,9-di-L-menthoxy-1,10-phenanthroline] (Men2Phen) and 2,9-bis(2-(S)-methylbutoxy)-1,10-phenanthroline (MB2Phen) were synthesized as chiral derivatives of 1,10-phenanthroline (Phen). Differences in rigidity and bulkiness of the chiral substituents at the 2- and 9-positions of the Phen backbone led to distinctive molecular dissymmetry in the ground state resulting in remarkable differences in circular dichroism. Men2Phen exhibited efficient circularly polarized luminescence (CPLm) at an anisotropy factor of 10-2 in the solid state based on molecular ordering disclosed by X-ray crystal analysis, while it showed much lower anisotropy factor in solution. MB2Phen, which was rather amorphous and did not afford good crystals, showed only negligible CPLm both in the solid state and in solution.

Cooperative Binding and Chirogenesis in an Expanded Perylene Bisimide Cyclophane

The encapsulation of more than one guest molecule into a synthetic cavity is a highly desirable yet a highly challenging task to achieve for neutral supramolecular hosts in organic media. Herein, we report a neutral perylene bisimide cyclophane, which has a tailored chiral cavity with an interchromophoric distance of 11.2 Å, capable of binding two aromatic guests in a π-stacked fashion. Detailed host-guest binding studies with a series of aromatic guests revealed that the encapsulation of the second guest in this cyclophane is notably more favored than the first one. Accordingly, for the encapsulation of the coronene dimer, a cooperativity factor (α) as high as 485 was observed, which is remarkably high for neutral host-guest systems. Furthermore, a successful chirality transfer, from the chiral host to encapsulated coronenes, resulted in a chiral charge-transfer (CT) complex and the rare observation of circularly polarized emission originating from the CT state for a noncovalent donor-acceptor assembly in solution. The involvement of the CT state also afforded an enhancement in the luminescence dissymmetry factor (glum) value due to its relatively large magnetic transition dipole moment. The 1:2 binding pattern and chirality-transfer were unambiguously verified by single-crystal X-ray diffraction analysis of the host-guest superstructures.

Binaphthalene-Assisted Axial Chirality in Porphyrins: Toward Solid-State Circularly Polarized Luminescence from Self-Assembled Nanostructures

Circularly polarized luminescence (CPL) is emerging as an effective tool to study the excited-state optical activity in molecules and their self-assembled nanostructures. Chiral porphyrins are a class of optically active molecules wherein the ground-state chirality has been extensively studied in recent times using circular dichroism (CD) spectroscopy. However, obtaining CPL from porphyrin nanostructures, which would have vast implications in biological applications, has remained an uphill task. In this work, we design and synthesize a pair of chiral porphyrin enantiomers functionalized by axially chiral binaphthalene units at the four meso-positions. The molecule undergoes self-assembly following an isodesmic polymerization model, leading to the formation of a spherical nanostructure possessing opposite chirality. Favorable thermodynamic parameters achieved through the controlled experimental conditions helped drive the self-assembly in the forward direction. The limitations imposed by a large nonradiative decay constant arising due to the aggregation-induced quenching could be overcome by fabricating self-standing polymeric films of the nanostructures. The films exhibited relatively high radiative decay and, more interestingly, good CPL activity with clear mirror image spectra for the nanostructures with opposite chirality. The work on CPL-active solid-state materials opens avenue for the design and synthesis of a variety of porphyrin-based chromophoric systems and their nanoaggregates that can find potential application in the field of chiral biosensing and bioimaging, security tags, and display devices.

Handedness-Inverted and Stimuli-Responsive Circularly Polarized Luminescent Nano/Micromaterials Through Pathway-Dependent Chiral Supramolecular Polymorphism

The precise manipulation of supramolecular polymorphs has been widely applied to control the morphologies and functions of self-assemblies, but is rarely utilized for the fabrication of circularly polarized luminescence (CPL) materials with tailored properties. Here, this work reports that an amphiphilic naphthalene-histidine compound (NIHis) readily self-assembled into distinct chiral nanostructures through pathway-dependent supramolecular polymorphism, which shows opposite and multistimuli responsive CPL signals. Specifically, NIHis display assembly-induced CPL from the polymorphic keto tautomer, which become predominant during enol-keto tautomerization shifting controlled by a bulk solvent effect. Interestingly, chiral polymorphs of nanofiber and microbelt with inverted CPL signals can be prepared from the same NIHis monomer in exactly the same solvent compositions and concentrations by only changing the temperature. The tunable CPL performance of the solid microbelts is realized under multi external physical or chemical stimuli including grinding, acid fuming, and heating. In particular, an emission color and CPL on-off switch based on the microbelt polymorph by reversible heating-cooling protocol is developed. This work brings a new approach for developing smart CPL materials via supramolecular polymorphism engineering.

Recent Progress in Circularly Polarized Luminescent Materials Based on Cyclodextrins

Circularly polarized luminescence (CPL) materials have been widely used in the fields of bioimaging, optoelectronic devices, and optical communications. The supramolecular interaction, involving harnessing non-covalent interactions between host and guest molecules to control their arrangements and assemblies, represents an advanced approach for facilitating the development of CPL materials and finely constructing and tuning the desired CPL properties. Cyclodextrins (CDs) are cyclic natural polysaccharides, which have also been ubiquitous in various fields such as molecular recognition, drug encapsulation, and catalyst separation. By adjusting the interactions between CDs and guest molecules precisely, composite materials with CPL properties can be facilely generated. This review aims to outline the design strategies and performance of CD-based CPL materials comprehensively and provides a detailed illustration of the interactions between host and guest molecules.

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.

Near-unity angular anisotropy of circularly polarized luminescence from microspheres of monodispersed chiral conjugated polymers

A microsphere, assembled from a chiral π-conjugated polymer with narrow polydispersity, features a well-organized twisted-bipolar structure and exhibits highly biased circularly polarized luminescence (CPL). The CPL emitted toward the equatorial direction is 61-fold greater than that emitted along the zenith direction, which is the highest anisotropy among existing microscopic CPL emitters.

Clustering triggered emissive liquid crystalline template for dual mode upconverted and downconverted circularly polarized luminescence

Liquid crystalline materials have attracted significant attention in chiroptical research due to their ability to form long range ordered helical superstructures. Research focus has been on exploiting the unique properties of liquid crystalline materials to demonstrate highly dissymmetric circularly polarised luminescent (CPL) systems. In this study, we present a thermally driven, facile approach to fabricate CPL-active materials utilizing cholesteryl benzoate as the active substrate. Cholesteryl benzoate, a well-known thermotropic liquid crystal, has been found to manifest intriguing optical characteristics upon subjecting to repeated heating-cooling cycles. Despite the absence of conventional fluorescent moieties, the material exhibited luminescence through aggregation induced clustering triggered emission mechanism. Systematic investigations revealed excitation-dependent CPL for solid cholesteryl benzoate films when subjected to multiple thermal cycles. The excited state chiroptical investigation performed after multiple thermal cycles showed a luminescence anisotropy (glum) of 8 × 10-2, which is a high value for simple organic molecules. Moreover, upon co-assembly with lanthanide-based upconversion nanophosphors (UCNPs), the hybrid system demonstrated upconverted circularly polarised luminescence (UC-CPL). Benefiting from the ability to endow upconversion nanoparticles of various sizes, fabrication of UCNP-ChB hybrid nanocomposites exhibiting multicoloured upconversion CPL was demonstrated. These findings highlight the potential of liquid crystalline materials for diverse applications, including 3D optical displays and anticounterfeiting technologies.

Chirally Selective and Switchable Luminescence from Achiral Quantum Emitters on Suspended Twisted Stacking Metasurfaces

Dynamic control of circularly polarized photoluminescence has aroused great interest in quantum optics and nanophotonics. Chiral plasmonic metasurfaces enable the manipulation of the polarization state via plasmon-photon coupling. However, current plasmonic light-emitting metasurfaces for effective deterministic modulation of spin-dependent emission at near-infrared wavelengths are underexplored in terms of dissymmetry and tunability. Here, we demonstrate a microfluidic hybrid emitting system of a suspended twisted stacking metasurface coated with PbS quantum dots. The suspended metasurface is fabricated with a single step of electron beam exposure, exhibiting a strong optical chirality of 309° μm-1 with a thickness of less than λ/10 at key spectral locations. With significant chiral-selective interactions, enhanced photoluminescence is achieved with strong dissymmetry in circular polarization. The dissymmetry factor of the induced circularly polarized emission can reach 1.54. More importantly, altering the refractive index of the surrounding medium at the bottom surface of the metasurface can effectively manipulate the chiroptical responses of the hybrid system, hence leading to chirality-reversed emission. This active hybrid emitting system could be a resultful platform for chirality-switchable light emission from achiral quantum emitters, holding great potential for anticounterfeiting, biosensing, light sources, imaging, and displays.

Supramolecular polymerization of [6]helicene-based cyano-luminogens: on the overall efficiency of self-assembled circularly polarized emitters

The synthesis of the [6]helicene-based luminophores 1 and 2 is reported. These chiral systems, endowed with cyano-stilbene fragments, form supramolecular polymers by the operation of intermolecular H-bonding interactions between the amides present in the peripheral side chains. The dissimilar disubstitution of 1 and 2 plays a crucial role in their self-assembling features. Thus, 1 does not show an efficient π-stacking of the central aromatic moiety. Instead, its self-assembling process results in a zig-zag arrangement of the monomeric units to form the aggregated species. On the other hand, 2 presents an efficient overlap of the aromatic backbones that affords a co-facial arrangement of the monomeric units. The solvent-dependent studies indicate that both [6]helicenes self-assemble following a cooperative supramolecular polymerization mechanism with a higher degree of cooperativity and stability for compound 2. The enantioenriched samples of both 1 and 2 display a rich dichroic pattern that changes when the supramolecular polymerization takes place. Furthermore, the presence of the cyano-stilbene moieties gives rise to an aggregation induced emission effect. The inherent chirality of both the monomeric and aggregated species of 1 and 2 provides the systems with CPL-emitting properties, presenting a remarkable overall CPL-efficiency, quantified by the BCPL parameter, that increases upon supramolecular polymerization.

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.

Surficial Host-Guest Responsive CsPbBr3 Perovskite Nanocrystals for Programmable Multi-Level Information Encryption

The design of smart stimuli-responsive photoluminescent materials capable of multi-level encryption and complex information storage is highly sought after in the current information era. Here, a novel adamantyl-capped CsPbBr3 (AD-CsPbBr3) perovskite NCs, along with its supramolecular host-guest assembly partner a modified β-CD (mCD), mCD@AD-CsPbBr3, are designed and prepared. By dispersing these two materials in different solvents, namely, AD-CsPbBr3 in toluene, mCD@AD-CsPbBr3 in toluene, and mCD@AD-CsPbBr3 in methanol, the three solutions exhibit diverse photoluminescence (PL) turn-on/off or PL discoloration response upon supramolecular stimulus. Based on these responses, a proof-of-principle programmable Multi-Level Photoluminescence Encoding System (MPLES) is established. Three types of four-level and three types of three-level information encoding are achieved by the system. A layer-by-layer four-level information encryption and decryption as well as a two-level encrypted 3D code are successfully achieved.

Photon Upconversion Cooperates with Downshifting in Chiral Systems: Modulation, Amplification, and Applications of Circularly Polarized Luminescence

Circularly polarized luminescence (CPL)-active materials are increasingly recognized for their potential applications such as 3D imaging, data storage, and optoelectronic devices. Typically, CPL materials have required high-energy (HE) photons for excitation to emit low-energy (LE) circularly polarized light, a process known as downshifting CPL (DSCPL). However, the emergence of upconverted CPL (UCCPL), where the absorption of multi LE photons results in the emission of a single HE photon with circular polarization, has recently attracted considerable attention. This minireview highlights the intricate relationship between upconversion and CPL phenomena. During upconversion, the dissymmetry factor (glum) value can be improved in certain systems. Additionally, the integration of both LE and HE photons in upconversion-downshifting-synergistic systems offers avenues for dual-excitation or dual-emission CPL functionalities. More in detail, the emerging UCCPL based on various photon upconversion mechanisms and their synergy with DSCPL are introduced. Additionally, several examples that demonstrate the applications of UCCPL are presented to highlight the future opportunities.

Encapsulation engineering of porous crystalline frameworks for delayed luminescence and circularly polarized luminescence

Delayed luminescence (DF), including phosphorescence and thermally activated delayed fluorescence (TADF), and circularly polarized luminescence (CPL) exhibit common and broad application prospects in optoelectronic displays, biological imaging, and encryption. Thus, the combination of delayed luminescence and circularly polarized luminescence is attracting increasing attention. The encapsulation of guest emitters in various host matrices to form host-guest systems has been demonstrated to be an appealing strategy to further enhance and/or modulate their delayed luminescence and circularly polarized luminescence. Compared with conventional liquid crystals, polymers, and supramolecular matrices, porous crystalline frameworks (PCFs) including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), zeolites and hydrogen-bonded organic frameworks (HOFs) can not only overcome shortcomings such as flexibility and disorder but also achieve the ordered encapsulation of guests and long-term stability of chiral structures, providing new promising host platforms for the development of DF and CPL. In this review, we provide a comprehensive and critical summary of the recent progress in host-guest photochemistry via the encapsulation engineering of guest emitters in PCFs, particularly focusing on delayed luminescence and circularly polarized luminescence. Initially, the general principle of phosphorescence, TADF and CPL, the combination of DF and CPL, and energy transfer processes between host and guests are introduced. Subsequently, we comprehensively discuss the critical factors affecting the encapsulation engineering of guest emitters in PCFs, such as pore structures, the confinement effect, charge and energy transfer between the host and guest, conformational dynamics, and aggregation model of guest emitters. Thereafter, we summarize the effective methods for the preparation of host-guest systems, especially single-crystal-to-single-crystal (SC-SC) transformation and epitaxial growth, which are distinct from conventional methods based on amorphous materials. Then, the recent advancements in host-guest systems based on PCFs for delayed luminescence and circularly polarized luminescence are highlighted. Finally, we present our personal insights into the challenges and future opportunities in this promising field.

Efficient chiral hydrogel template based on supramolecular self-assembly driven by chiral carbon dots for circularly polarized luminescence

Since the chiral emission of excited states is observed on carbon dots (CDs), exploration towards the design and synthesis of chiral CDs nanomaterials with circularly polarized luminescence (CPL) properties has been at a brisk pace. In this regard, the "host and guest" co-assembly strategy based on the combination of CDs and chiral templates has been of unique interest recently for its convenient operation, multicolor tunable CPL, and wide application of prepared CDs-composited materials in optoelectronic devices and information encryption. However, the existing chiral templates that match perfectly with chiral CDs exhibiting optical activity both in ground and excited states are rather scarce. In this work, we synthesize the chiral CDs that could induce the spontaneous supramolecular self-assembly of N-(9-fluorenylmethox-ycarbonyl) (Fmoc)-protected glutamic acid to form chiral hydrogels with helical nanostructure. The co-assembled hydrogels show powerful chiral template function, which not only enable chiral CDs with a luminescence dissymmetry factor (glum) up to 10-2, but also have universal chiral transfer to inserted dye molecules, realizing full-color CPL and Förster resonance energy transfer (FRET) CPL as well as the distinction between left and right circularly polarized light. This CPL-active template based on chiral CDs enriches the design scenario of chiral functionalized nanomaterials.

Interfacial self-assembly of a chiral pyrene exciplex into a superhelix with enhanced circularly polarized luminescence

We found that the interfacially confined self-assembly of pyrene and phenanthrene glutamides can form strong exciplexes and amorphous superhelices, which show intensity-enhanced and sign-inverted CPL activity with improved quantum yield compared to a pyrene excimer. This work unveils the predominant role of supramolecular nanostructures over molecular configurations on CPL performance.

Achieving Circularly Polarized Phosphorescence through Noncovalent Clipping of Metallotweezers

Circularly polarized phosphorescent materials, based on host-guest complexation, have received significant attention due to their outstanding emission performance in solutions. Recent studies have primarily focused on macrocyclic host-guest complexes. To broaden the scope of this research, there is a keen pursuit of developing novel chiral phosphorescent host-guest systems. Metallotweezers with square-planar d8 transition metal complexes emerge as promising candidates for achieving this objective. Specifically, metallotweezers, comprising platinum(II) terpyridine and gold(III) diphenylpyridine pincers on a diphenylpyridine scaffold, have been designed and synthesized. Due to the preorganization effect rendered by the diphenylpyridine scaffold, the resulting metallotweezers are capable of complexing with each other and forming quadruple stacking structures. The phosphorescent emission is enhanced owing to the synergistic rigidifying and shielding effects. Meanwhile, the steric effect of chiral (1R) pinene units on the platinum(II) terpyridine pincers results in a stereospecific twist for the quadruple stacking structures. Thus, the chirality transfers from the molecular to the supramolecular level. By a combination of phosphorescent enhancement and supramolecular chirality for the clipping complex, circularly polarized phosphorescent emission is achieved. Overall, noncovalent clipping of metallotweezers exemplified in the current study presents a novel and effective approach toward solution-processable circularly polarized phosphorescent materials.

Efficient Ultraviolet Circularly Polarized Luminescence in Zero-Dimensional Hybrid Cerium Bromides

Ultraviolet circularly polarized luminescence (UV-CPL) with high photon energy shows great potential in polarized light sources and stereoselective photopolymerization. However, developing luminescent materials with high UV-CPL performance remains challenging. Here, we report a pair of rare earth Ce3+-based zero-dimensional (0D) chiral hybrid metal halides (HMHs), R/S-(C14H24N2)2CeBr7, which exhibits characteristic UV emissions derived from the Ce 5d-4f transition. The compounds show simultaneously high photoluminescent quantum yields of (32-39)% and large luminescent dissymmetry factor (|glum|) values of (1.3-1.5)×10-2. Thus, the figures of merits of R/S-(C14H24N2)2CeBr7 are calculated to be (4.5-5.8)×10-3, which are superior to the reported UV-CPL emissive materials. Additionally, nearly 91 % of their PL intensities at 300 K can be well preserved at 380 K (LED operating temperature) without phase transition or decomposition, demonstrating the excellent structural and optical thermal stabilities of R/S-(C14H24N2)2CeBr7. Based on these enantiomers, the fabricated UV-emitting CP-LEDs exhibit high polarization degrees of ±1.0 %. Notably, the UV-CPL generated from the devices can significantly trigger the enantioselective photopolymerization of diacetylene with remarkable stereoselectivity, and consequently yield polymerized products with the anisotropy factors of circular dichroism (gCD) up to ±3.9×10-2, outperforming other UV-CPL materials and demonstrating their great potential as UV-polarized light sources.

Chiral Luminophore Guided Self-Assembly of Achiral Block Copolymers for the Amplification of Circularly Polarized Luminescence

This work aims to examine the effect of self-assembly on the chiroptic responses of the achiral block copolymer (BCP) polystyrene-b-poly(ethylene oxide) (PS-b-PEO) associated with chiral luminophores, (R)- or (S)-1,1'-bi-2-naphthol ((R)- or (S)-BINOL), through hydrogen bonding. With the formation of a well-ordered helical phase (H*), significantly induced circular dichroism (ICD) signals for the PEO block in the mixture can be found. Most interestingly, a remarkable amplification with an extremely large dissymmetry factor of luminescence (glum) from 10-3 to 0.3 (i.e., induced circular polarized luminescence (iCPL) behavior) for the chiral BINOLs in the mixture can be achieved by the formation of the helical phase (H*) via mesochiral self-assembly. As a result, by taking advantage of BCP for mesochiral self-assembly, it is feasible to create a nanostructured monolith with substantial optical activities, offering promising applications in the design of chiroptic devices.

Near-Infrared Circularly Polarized Luminescent Physical Unclonable Functions

Distinguished from traditional physical unclonable functions (PUFs), optical PUFs derive their encoded information from the optical properties of materials, offering distinct advantages, including solution processability, material versatility, and tunable luminescence performance. However, existing research on optical PUFs has predominantly centered on visible photoluminescence, while advanced optical PUFs based on higher-level covert light remain unexplored. In this study, we present optical PUFs based on the utilization of the covert light of near-infrared circularly polarized luminescence (NIR-CPL). This interesting property is achieved by incorporating Yb-doped metal halide perovskite nanocrystals (Yb-PeNCs) possessing NIR emission property into chiral imprinted photonic (CIP) films. By employing a solvent immersion method, we successfully integrated Yb-PeNCs into these CIP films, thereby creating an optically unclonable surface. The resulting NIR-CPL emission adds a layer of advanced security to the optical PUF systems. These findings underscore the potential of solution-processable chiral films to play a pivotal role in advancing the next generation of PUFs.

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.