Light‐Directed Dynamic Chirality Inversion in Functional Self‐Organized Helical Superstructures

Dynamic Diffractive Patterns in Helix-Inverting Cholesteric Liquid Crystals

The future of adaptive materials will rely on transduction of molecular motion across increasing length scales, up to the macroscopic and functional level. In this context, liquid crystals have emerged as a promising amplification medium, in view of their long-range order and high sensitivity to external stimuli, and in particular, chiral liquid crystals have demonstrated widely tunable optical properties and invertible handedness. Here, we demonstrate that by applying weak electric fields, regular, periodic and light-tunable patterns can be formed spontaneously in cholesteric liquid crystals. These patterns can be used as light-tunable diffraction gratings for which the period, the diffraction efficiency, and the in-plane orientation of grating vector can be controlled precisely, reversibly, and independently. Such a photoregulation allows generating a variety of one- and two-dimensional complex diffractive patterns in a single material. Our data are also supported by modeling and theoretical calculations. Overall, the fine tunability of cholesteric materials doped with artificial molecular switches makes them attractive for optics and photonics.

Optically Rewritable Transparent Liquid Crystal Displays Enabled by Light-Driven Chiral Fluorescent Molecular Switches

Functional soft materials exhibiting distinct functionalities in response to a specific stimulus are highly desirable towards the fabrication of advanced devices with superior dynamic performances. Herein, two novel light-driven chiral fluorescent molecular switches have been designed and synthesized that are able to exhibit unprecedented reversible Z/E photoisomerization behavior along with tunable fluorescence intensity in both isotropic and anisotropic media. Cholesteric liquid crystals fabricated using these new fluorescent molecular switches as chiral dopants exhibit reversible reflection color tuning spanning the visible and infrared region of the spectrum. Transparent display devices have been fabricated using both low chirality and high chirality cholesteric films that operate either exclusively in fluorescent mode or in both fluorescent and reflection mode, respectively. The dual mode display device employing short pitch cholesteric film is able to function on demand under all ambient light conditions including daylight and darkness with fast response and high resolution. Moreover, the proof-of-concept for a "remote-writing board" using cholesteric films containing one of the light-driven chiral fluorescent molecular switches with ease of fabrication and operation is disclosed herein. Such optically rewritable transparent display devices enabled by light-driven chiral fluorescent molecular switches pave a new way for developing novel display technology under different lighting conditions.

Ligand Exchange Strategy for Tuning of Helicity Inversion Speeds of Dynamic Helical Tri(saloph) Metallocryptands

We developed a new strategy, ligand exchange strategy, for tuning the response speeds of helicity inversion of a metal-containing helical structure. This is based on the exchange of the two axial amine ligands of the octahedral Co³⁺ centers in the metallocryptands [LCo₃ X₆ ] (X=axial amine ligand). The response speeds of the helicity induction were controlled by using different combinations of achiral and chiral amines as the starting and entering ligands, respectively. The response speeds of the helicity inversion from P to M were also tuned by using different combinations of chiral amines.

Air-Curable, High-Resolution Patternable Oxetane-Based Liquid Crystalline Photonic Films via Flexographic Printing

The production of patterned photonic films on a large scale remains a challenge. Here, we report on a new class of photonic materials that are based on oxetane liquid crystals (LCs). Patterned reflective coatings can be produced from these materials on flexible substrates by using flexographic printing. This industrially relevant process allows for upscaling in future applications. Furthermore, the oxetane LCs used do not require an inert atmosphere for photopolymerization, unlike previously described acrylate systems. We show that the flexographic printing process results in excellent alignment, and that the patterns produced display a high resolution. Additionally, we demonstrate that free-standing photonic reflecting foils can also be produced from these materials. Our new oxetane-based patterned iridescent colored materials have potential application for both esthetic purposes as well as anticounterfeit labels.

Modulating ICT emission: a new strategy to manipulate the CPL sign in chiral emitters

A new strategy to manipulate the circularly polarized luminescence (CPL) handedness in chiral emitters, based on modulating the population of an emissive ICT state, is proposed. Such a strategy is particularly interesting for conformationally rigid and non-aggregating chiral organic emitters, opening up new perspectives for the development of CPL applications based on organic molecules.

Reversible chirality inversion of circularly polarized luminescence in a photo-invertible helical cholesteric superstructure

The first example of photo-driven reversible chirality inversion of circularly polarized luminescence in a helical cholesteric superstructure is reported.

Dissymmetry enhancement in enantioselective synthesis of helical polydiacetylene by application of superchiral light

Superchiral light, generated by the interference of two counter-propagating circularly polarized light (CPL) with same frequency, opposite handedness and different intensity, exhibits enhanced dissymmetry in its interaction with chiral molecules, and has the potential for ultrasensitive detection and characterization of chiral molecules. It is anticipated that the enhanced optical dissymmetry in superchiral light (SCL) field may be utilized to promote asymmetric photochemical reactions efficiency. Herein we reported SCL impart greater chiral bias to trigger asymmetric photo-polymerization reaction from initially achiral diacetylene (DA) monomer, and the enhanced optical dissymmetry for whole polydiacetylene (PDA) films could be achieved. An explanation based on the chiral transfer and amplification of chiral bias from SCL during the polymerization process has been proposed. Moreover, thus formed chiral PDA films polymerized by SCL exhibited enhanced enantioselective recognition ability, and can serve as a direct visual probe for the discrimination of some specific enantiomers.

Superchiral light can be utilized to promote asymmetric photochemical reactions. Here the authors show that superchiral light imparts greater chiral bias to trigger asymmetric photo-polymerization reactions from initially achiral diacetylene monomers and enhanced optical dissymmetry in polydiacetylene films.

Hierarchical Self-Assembly in Liquid-Crystalline Block Copolymers Enabled by Chirality Transfer

Helical topological structures are often found in chiral biological systems, but seldom in synthesized polymers. Now, controllable microphase separation of amphiphilic liquid-crystalline block copolymers (LCBCs) consisting of hydrophilic poly(ethylene oxide) and hydrophobic azobenzene-containing poly(methylacrylate) is combined with chirality transfer to fabricate helical nanostructures by doping with chiral additives (enantiopure tartaric acid). Through hydrogen-bonding interactions, chirality is transferred from the dopant to the aggregation, which directs the hierarchical self-assembly in the composite system. Upon optimized annealing condition, helical structures in film are fabricated by the induced aggregation chirality. The photoresponsive azobenzene mesogens in the LCBC assist photoregulation of the self-assembled helical morphologies. This allows the construction and non-contact manipulation of complicated nanostructures.

Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates

Much attention has recently focused on helical structures that can change their helicity in response to external stimuli. The requirements for the invertible helical structures are a dynamic feature and well-defined structures. In this context, helical metal complexes with a labile coordination sphere have a great advantage. There are several types of dynamic helicity controls, including the responsive helicity inversion. In this review article, dynamic helical structures based on oligo(salamo) metal complexes are described as one of the possible designs. The introduction of chiral carboxylate ions into Zn3La tetranuclear structures as an additive is effective to control the P/M ratio of the helix. The dynamic helicity inversion can be achieved by chemical modification, such as protonation/deprotonation or desilylation with fluoride ion. When (S)-2-hydroxypropyl groups are introduced into the oligo(salamo) ligand, the helicity of the resultant complexes is sensitively influenced by the metal ions. The replacement of the metal ions based on the affinity trend resulted in a sequential multistep helicity inversion. Chiral salen derivatives are also effective to bias the helicity; by incorporating the gauche/anti transformation of a 1,2-disubstituted ethylene unit, a fully predictable helicity inversion system was achieved, in which the helicity can be controlled by the molecular lengths of the diammonium guests.

Stimuli-Driven Control of the Helical Axis of Self-Organized Soft Helical Superstructures

Supramolecular and macromolecular functional helical superstructures are ubiquitous in nature and display an impressive catalog of intriguing and elegant properties and performances. In materials science, self-organized soft helical superstructures, i.e., cholesteric liquid crystals (CLCs), serve as model systems toward the understanding of morphology- and orientation-dependent properties of supramolecular dynamic helical architectures and their potential for technological applications. Moreover, most of the fascinating device applications of CLCs are primarily determined by different orientations of the helical axis. Here, the control of the helical axis orientation of CLCs and its dynamic switching in two and three dimensions using different external stimuli are summarized. Electric-field-, magnetic-field-, and light-irradiation-driven orientation control and reorientation of the helical axis of CLCs are described and highlighted. Different techniques and strategies developed to achieve a uniform lying helix structure are explored. Helical axis control in recently developed heliconical cholesteric systems is examined. The control of the helical axis orientation in spherical geometries such as microdroplets and microshells fabricated from these enticing photonic fluids is also explored. Future challenges and opportunities in this exciting area involving anisotropic chiral liquids are then discussed.

Instant Locking of Molecular Ordering in Liquid Crystal Elastomers by Oxygen-Mediated Thiol-Acrylate Click Reactions

Liquid crystal elastomers (LCEs) with intrinsic anisotropic strains are reversible shape-memory polymers of interest in sensor, actuator, and soft robotics applications. Rapid gelation of LCEs is required to fix molecular ordering within the elastomer network, which is essential for directed shape transformation. A highly efficient photo-cross-linking chemistry, based on two-step oxygen-mediated thiol-acrylate click reactions, allows for nearly instant gelation of the main-chain LCE network upon exposure to UV light. Molecular orientation from the pre-aligned liquid crystal oligomers can be faithfully transferred to the LCE films, allowing for preprogrammed shape morphing from two to three dimensions by origami- (folding-only) and kirigami-like (folding with cutting) mechanisms. The new LCE chemistry also enables widely tunable physical properties, including nematic-to- isotropic phase-transition temperatures (T_N-I ), glassy transition temperatures (T_g ), and mechanical strains, without disrupting the LC ordering.

Palladium-Catalyzed 4-Fold Domino Reaction for the Synthesis of a Polymeric Double Switch

A palladium-catalyzed 4-fold domino reaction consisting of two carbopalladation reactions and two C-H activation reactions, followed by the introduction of an acrylate moiety, led to the tetra-substituted helical alkene A2, using the dialkyne A3 as a substrate. The alkene was copolymerized with butyl acrylate by using the reversible addition-fragmentation chain transfer polymerization (RAFT) to give the desired polymeric switch A1.

Ferroelectric Liquid Crystals: Synthesis and Thermal Behavior of Optically Active, Three-Ring Schiff Bases and Salicylaldimines

The chiral ferroelectric smectic C (SmC*) phase, characterized by a helical superstructure, has been well exploited in developing high-resolution microdisplays that have been effectively employed in the fabrication of a wide varieties of portable devices. Although, an overwhelming number of optically active (chiral) liquid crystals (LCs) exhibiting a SmC* phase have been designed and synthesized, the search for new systems continues so as to realize mesogens capable of meeting technical necessities and specifications for their end-use. In continuation of our research work in this direction, herein we report the design, synthesis, and thermal behavior of twenty new optically active, three-ring calamitic LCs belonging to four series. The first two series comprise five pairs of enantiomeric Schiff bases whereas the other two series are composed of five pairs of enantiomeric salicylaldimines. In each pair of optical isomers, the configuration of a chiral center in one stereoisomer is opposite to that of the analogous center in the other isomer as they are derived from (3 S)-3,7-dimethyloctyloxy and (3 R)-3,7-dimethyloctyloxy tails. To probe the structure-property correlations in each series, the length of the n-alkoxy tail situated at the other end of the mesogens has been varied from n-octyloxy to n-dodecyloxy. The measurement of optical activity of these chiral mesogens was carried out by recording their specific rotations. As expected, enantiomers rotate plane polarized light in the opposite direction but by the same magnitude. The thermal behavior of the compounds was established by using a combination of optical polarizing microscopy, differential scanning calorimetry, and powder X-ray diffraction. These complementary techniques demonstrate the existence of the expected, thermodynamically stable, chiral smectic C (SmC*) LC phase besides blue phase I/II (BPI or BPII) and chiral nematic (N*) phase. However, as noted in our previous analogous study, the vast majority of the Schiff bases show an additional metastable, unfamiliar smectic (SmX) phase just below the SmC* phase. Notably, the SmC* phase persists over the temperature range ≈80-115 °C. Two mesogens chosen each from Schiff bases and salicylaldimines were investigated for their electrical switching behavior. The study reveals the ferroelectric switching characteristics of the SmC* phase featuring the spontaneous polarization (P_S ) in the range 69-96 nC cm^-2 . The helical twist sense of the SmC* phase as well as the N* phase formed by a pair of enantiomeric Schiff bases and salicylaldimines has been established with the help of circular dichroism (CD) spectroscopic technique. As expected, the SmC* and the N* phase of a pair of enantiomers showed mirror image CD signals. Most importantly, the reversal of helical handedness from left to right and vice versa has been evidenced during the N* to SmC* phase transition, implying that the screw sense of the helical array of the N* phase and the SmC* phase of an enantiomer is opposite.

Photochromism into nanosystems: towards lighting up the future nanoworld

The ability to manipulate the structure and function of promising nanosystems via energy input and external stimuli is emerging as an attractive paradigm for developing reconfigurable and programmable nanomaterials and multifunctional devices. Light stimulus manifestly represents a preferred external physical and chemical tool for in situ remote command of the functional attributes of nanomaterials and nanosystems due to its unique advantages of high spatial and temporal resolution and digital controllability. Photochromic moieties are known to undergo reversible photochemical transformations between different states with distinct properties, which have been extensively introduced into various functional nanosystems such as nanomachines, nanoparticles, nanoelectronics, supramolecular nanoassemblies, and biological nanosystems. The integration of photochromism into these nanosystems has endowed the resultant nanostructures or advanced materials with intriguing photoresponsive behaviors and more sophisticated functions. In this Review, we provide an account of the recent advancements in reversible photocontrol of the structures and functions of photochromic nanosystems and their applications. The important design concepts of such truly advanced materials are discussed, their fabrication methods are emphasized, and their applications are highlighted. The Review is concluded by briefly outlining the challenges that need to be addressed and the opportunities that can be tapped into. We hope that the review of the flourishing and vibrant topic with myriad possibilities would shine light on exploring the future nanoworld by encouraging and opening the windows to meaningful multidisciplinary cooperation of engineers from different backgrounds and scientists from the fields such as chemistry, physics, engineering, biology, nanotechnology and materials science.

Stimuli-Directed Dynamic Reconfiguration in Self-Organized Helical Superstructures Enabled by Chemical Kinetics of Chiral Molecular Motors

Dynamic controllability of self-organized helical superstructures in spatial dimensions is a key step to promote bottom-up artificial nanoarchitectures and functional devices for diverse applications in a variety of areas. Here, a light-driven chiral overcrowded alkene molecular motor with rod-like substituent is designed and synthesized, and its thermal isomerization reaction exhibits an increasing structural entropy effect on chemical kinetic analysis in anisotropic achiral liquid crystal host than that in isotropic organic liquid. Interestingly, the stimuli-directed angular orientation motion of helical axes in the self-organized helical superstructures doped with the chiral motors enables the dynamic reconfiguration between the planar (thermostationary) and focal conic (photostationary) states. The reversible micromorphology deformation processes are compatible with the free energy fluctuation of self-organized helical superstructures and the chemical kinetics of chiral motors under different conditions. Furthermore, stimuli-directed reversible nonmechanical beam steering is achieved in dynamic hidden periodic photopatterns with reconfigurable attributes prerecorded with a corresponding photomask and photoinduced polymerization.

Photoalignment of dye-doped cholesteric liquid crystals for electrically tunable patterns with fingerprint textures

We present a convenient photoalignment approach to fabricate rewritable fingerprint textures with designed geometrical patterns based on methyl red doped cholesteric liquid crystals (MDCLCs). MDCLC systems with/without nanoparticles of polyhedral oligomeric silsesquioxanes (POSS) were employed to realize two types of sophisticated binary patterns, respectively. Based on the understanding of involved mechanisms related to boundary conditions and middle-layer theory, we demonstrated the precise manipulation of fingerprint patterns by varying the fingerprint grating vectors in different domains. Notably, the hybrid-aligned liquid crystal configuration induced by POSS nanoparticles, which leads to the electrically rotatable grating, can be converted into the planar-aligned configuration by the adsorption of photoexcited methyl red molecules onto the indium-tin-oxide (ITO) surface. In this manner, the dynamic voltage-dependent behavior of fingerprint gratings is altered from the rotation mode (R-mode) to the on-off mode (O-mode).

Precisely Tuning Helical Twisting Power via Photoisomerization Kinetics of Dopants in Chiral Nematic Liquid Crystals

It has been paid much attention to improve the helical twisting power (β) of dopants in chiral nematic liquid crystals (CLCs); however, the correlations between the β value and the molecular structures as well as the interaction with nematic LCs are far from clear. In this work, a series of reversibly photo-switchable axially chiral dopants with different lengths of alkyl or alkoxyl substituent groups have been successfully synthesized through nucleophilic substitution and the thiol-ene click reaction. Then, the effect of miscibility between these dopants and nematic LCs on the β values, as well as the time-dependent decay/growth of the β values upon irradiations, has been investigated. The theoretical Teas solubility parameter shows that the miscibility between dopants and nematic LCs decreases with increasing of the length of substituent groups from dopant 1 to dopant 4. The β value of chiral dopants in nematic LCs decreases from dopant 1 to dopant 4 both at the visible light photostationary state (PSS) and at the UV PSS after UV irradiation. With increasing of the length of substituent groups, the photoisomerization rate constant of dopants increases for trans-cis transformation upon UV irradiation and decreases for the reverse process upon visible light irradiation either in isotropic ethyl acetate or in anisotropic LCs, although the constant in ethyl acetate is several times larger than the corresponding value in LCs. Also, the color of the CLCs could be tuned upon light irradiations. These results enable the precise tuning of the pitch and selective reflection wavelength/color of CLCs, which paves the way to the applications in electro-optic devices, information storage, high-tech anticounterfeit, and so forth.

Efficient visible-light full-color tuning of self-organized helical superstructures enabled by fluorinated chiral switches

Light-driven chiral switches have the ability to tune and control the self-organized helical superstructures of cholesteric liquid crystals (CLCs), resulting in the photo-induced reflection wavelength shift of the CLCs. A new type of axially chiral switch functionalized with fluorine atoms ortho to the azobenzene moiety is found to exhibit reversible visible-light-driven photoisomerization due to a separation of the n–π* absorption bands of the trans and cis isomers. These chiral switches all have high HTP values and the doped CLCs with 15.8 wt% concentration demonstrates reversible dynamic tuning of the reflection color within the entire visible spectrum driven by 530 nm and 445 nm visible light. It is also noteworthy that the thermal stability is improved thanks to the cis form of the fluorinated azobenzenes possessing a remarkably long half-life. The newly designed visible-light-driven chiral switches may broaden the application of CLCs, especially in the fields where high energy UV light is unfavorable.

Reversible dynamic tuning of the reflection color from cholesteric liquid crystals within the entire visible spectrum is driven by green and blue light via newly designed chiral switches.

Optically Reconfigurable Chiral Microspheres of Self-Organized Helical Superstructures with Handedness Inversion

Optically reconfigurable monodisperse chiral microspheres of self-organized helical superstructures with dynamic chirality were fabricated via a capillary-based microfluidic technique. Light-driven handedness-invertible transformations between different configurations of microspheres were vividly observed and optically tunable RGB photonic cross-communications among the microspheres were demonstrated.

Controllable Dynamic Zigzag Pattern Formation in a Soft Helical Superstructure

Zigzag pattern formation is a common and important phenomenon in nature serving a multitude of purposes. For example, the zigzag-shaped edge of green leaves boosts the transportation and absorption of nutrients. However, the elucidation of this complicated shape formation is challenging in fluid mechanics and soft condensed matter systems. Herein, a dynamically reconfigurable zigzag pattern deformation of a soft helical superstructure is demonstrated in a photoresponsive self-organized cholesteric liquid crystal superstructure under the simultaneous influence of an applied electric field and light irradiation. The zigzag-shaped pattern can not only be generated and terminated repeatedly on demand, but can also be easily manipulated by alternating irradiation of ultraviolet and visible light while under the influence of a sustained electric field. This unique behavior results from a delicate balance among the variable experimental parameters. The evolution of the zigzag-shaped pattern is successfully modeled by numerical simulations and has been monitored through diffraction of a probe laser. Interestingly, this fascinating zigzag-shaped pattern yields crescent-shaped diffraction pattern. The reversibly controllable dynamic zigzag pattern could enable the fabrication of novel photonic devices and architectures, besides greatly advancing the fundamental understanding of temporal behavior of ordered soft materials under combined stimuli.

Vertical Orientation of Nanocylinders in Liquid-Crystalline Block Copolymers Directed by Light

The microphase-separated nanostructures of block copolymers are ideal nanotemplates for advanced fabrication, but they are greatly limited by the rapid and precise manipulation especially at room temperature. Here we report one method of light-directed regulation of nanostructures in thin films of liquid-crystalline diblock copolymers containing azobenzene units as photoresponsive mesogens. The in-plane orientated nanocylinders in thin film can be light-directed into out-of-plane on a time scale of seconds at room temperature. This fast regulation is beneficial from the fast process of photoinduced phase transition of the mesogenic block from liquid crystal to disordered isotropic phase. Several influence factors like the molecular weight of polymer, film thickness, light intensity, and relative humidity were studied in the light-directed processes. In addition, the photoregulated nanostructures demonstrate their capability of being photopatterned and further used as nanotemplates for fabrication of nanoparticles. The light-directed method shows noncontact, precise, and reversible features, enabling it to find further applications in fast control of nanostructures for nanofabrication and nanoengineering.

Dynamic Orthogonal Switching of a Thermoresponsive Self-Organized Helical Superstructure

Controllable manipulation of self-organized dynamic superstructures of functional molecular materials by external stimuli is an enabling enterprise. Herein, we have developed a thermally driven, self-organized helical superstructure, i.e., thermoresponsive cholesteric liquid crystal (CLC), by integrating a judiciously chosen thermoresponsive chiral molecular switch into an achiral liquid crystalline medium. The CLC in lying state, in both planar and twisted nematic cells, exhibits reversible in-plane orthogonal switching of its helical axis in response to the combined effect of temperature and electric field. Consequently, the direction of the cholesteric grating has been observed to undergo 90° switching in a single cell, enabling non-mechanical beam steering along two orthogonal directions. The ability to reversibly switch the cholesteric gartings along perpendicular directions by appropriately adjusting temperature and electric field strength could facilitate their applications in 2D beam steering, spectrum scanning, optoelectronics and beyond.

Demonstration of patterned polymer-stabilized cholesteric liquid crystal textures for anti-counterfeiting two-dimensional barcodes

We evaluated the feasibility of embedding periodically arranged squares with planar and vertical texture into a background with a developable-modulation (DM) type cholesteric liquid crystal (CLC) fingerprint texture by a two-step ultraviolet-induced polymerization method. Checker-patterned optical diffractive elements, which can be seen as a variation of a two-dimensional (2D) barcode, were first realized and the dependence of diffraction behaviors on incident light polarization and applied voltage were investigated. Taking advantage of the natural randomness and uncontrollable variations of a DM-type fingerprint textures, a polymer-stabilized CLC (PSCLC) graphic symbol with a 2D barcode pattern was then implemented with enhanced anti-counterfeiting features that are difficult to falsify or duplicate. The results indicate that the multiplexing of nonuniform DM-type fingerprint gratings, cross-polarized light readout, and unique polarization diffraction characteristics can improve the level of security.

Mesoscopic helical architectures via self-assembly of porphyrin-based discotic systems

Mesoscopic super-helices with preferred helicity have been serendipitously formed via the self-assembly of electroactive extended core discotic molecules.

Supramolecular self-assembly of chiral polyimides driven by repeat units and end groups

Complementary aromatic π–π stacking and hydrogen bonding induce time-dependent chiroptical spectroscopic behaviours of l-phenylalaninate-derived chiral polyimide.

Circular Dichroism Studies on Plasmonic Nanostructures

In recent years, optical chirality of plasmonic nanostructures has aroused great interest because of innovative fundamental understanding as well as promising potential applications in optics, catalysis and sensing. Herein, state-of-the-art studies on circular dichroism (CD) characteristics of plasmonic nanostructures are summarized. The hybrid of achiral plasmonic nanoparticles (NPs) and chiral molecules is explored to generate a new CD response at the plasmon resonance as well as the enhanced CD intensity of chiral molecules in the UV region, owing to the Coulomb static and dynamic dipole interactions between plasmonic NPs and chiral molecules. As for chiral assembly of plasmonic NPs, plasmon-plasmon interactions between the building blocks are found to induce generation of intense CD response at the plasmon resonance. Three-dimensional periodical arrangement of plasmonic NPs into macroscale chiral metamaterials is further introduced from the perspective of negative refraction and photonic bandgap. A strong CD signal is also discerned in achiral planar plasmonic nanostructures under illumination of circular polarized plane wave at oblique incidence or input vortex beam at normal incidence. Finally perspectives, especially on future investigation of time-resolved CD responses, are presented.