Search Results (425)

The reverse-mode smart windows, which usually fabricated by polymer stabilized liquid crystal (PSLC), are more practical for scenarios where high transparency is a priority for most of the time. However, the polymer stabilized cholesteric liquid crystal (PSCLC) film exhibits poor spacing stability due to the mobility of CLC molecules during the bending deformation. In this work, a reverse-mode PSCLC flexible film with excellent bending resistance was fabricated by the construction of polymer spacer columns. The effect of the concentration of the polymerizable monomer C6M and chiral dopant R811 on the electro-optical properties and polymer microstructure of the film were studied. The sample B2 containing 3 wt% of C6M and 3 wt% R811 presented the best electro-optical performance. The electrical switch between transparent and opaque state of the flexible PSCLC film after bending not only indicated the excellent electro-optical switching performance, but also demonstrated the outstanding bending resistance of the sample with polymer spacer columns, which makes the PSCLC film containing polymer spacer columns have a great potential to be applied in the field of flexible devices. Full article

Optically active heterodimeric 5,5′-linked bis-isochromans, containing a stereogenic ortho-trisubstituted biaryl axis and up to four chirality centers, were synthesized stereoselectively by using a Suzuki–Miyaura biaryl coupling reaction of optically active isochroman and 1-arylpropan-2-ol derivatives, providing the first access to synthetic biaryl-type isochroman dimers. Enantiomeric pairs and stereoisomers up to seven derivatives were prepared with four different substitution patterns, which enabled us to test how OR, ECD, and VCD measurements and DFT calculations can be used to determine parallel central and axial chirality elements in three isolated blocks of chirality. In contrast to natural penicisteckins A–D and related biaryls, the ECD spectra and OR data of (aS) and (aR) atropodiastereomers did not reflect the opposite axial chirality, but they were characteristic of the central chirality. The atropodiastereomers showed consistently near-mirror-image VCD curves, allowing the determination of axial chirality with the aid of DFT calculation or by comparison of characteristic VCD transitions. Full article

Recently, a technical modification of a Reflectance Anisotropy Spectroscopy (RAS) spectrometer has been proposed to investigate the circular dichroism (CD) of samples instead of the normally studied linear dichroism. CD-RAS measures the anisotropy of the optical properties of a sample under right-handed and left-handed circularly polarized light. Here, we present the application of CD-RAS to measure the circular dichroism of a twisted bilayer of graphene, purposely prepared as a possible substrate for the adsorption of thin molecular layers, in air, in liquid or in a vacuum. This result demonstrates the performance of the apparatus and shows interesting perspectives for the investigation of chiral organic assemblies deposited in solid film. Full article

Nanographenes are of increasing importance owing to their potential applications in the photoelectronic field. Meanwhile, recent studies have primarily focused on the pure electronic spectra of nanographenes, which have been found to be inadequate for describing the experimental spectra that contain vibronic progressions. In this study, we focused on the vibronic effect on the electronic transition of a range of chiral nanographenes, especially in the low-energy regions with distinct vibronic progressions, using theoretical calculations. All the calculations were performed at the PBE0-D3(BJ)/def2-TZVP level of theory, adopting both time-dependent and time-independent approaches with Franck–Condon approximation. The resulting calculated curves exhibited good alignment with the experimental data. Notably, for the nanographenes incorporating helicene units, owing to the increasing π-extension, the major vibronic modes in the vibrationally resolved spectra differed significantly from those of the primitive helicenes. This investigation suggests that calculations that account for the vibronic effect could have better reproducibility compared with calculations based solely on pure electronic transitions. We anticipate that this study could pave the way for further investigations into optical and chiroptical properties, with a deeper understanding of the vibronic effect, thereby providing theoretical explanations with higher precision on more sophisticated nanographenes. Full article

The interaction between natural amino acids and hydrogen peroxide is of paramount importance due to the widespread use of hydrogen peroxide in biological and environmentally significant processes. Given that both amino acids and hydrogen peroxide occur in nature in two enantiomeric forms, it is crucial to investigate the formation of complexes between them, considering the role of molecular chirality. In this work, we report a theoretical study on the hydrogen peroxide enantiomers and their interactions with L- and S-serine and their clusters. We aimed to evaluate the non-covalent interactions between each hydrogen peroxide enantiomer and the L- and D-enantiomers of the non-essential amino acid serine and their clusters. First, the potential energy surfaces (PES) of transitions between enantiomers of the simplest chiral molecule, hydrogen peroxide, in the gas phase and in aqueous solution were studied using the Møller–Plesset theory method MP2/aug-cc-pVDZ. The activation energies of such transitions were calculated. The interactions of both hydrogen peroxide enantiomers (P and M) with L- and D-serine enantiomers were analyzed by density functional theory (DFT) with ωb97xd/6-311+G**, B3Lyp/6-311+G**, B3P86/6-311+G**, and M06/6-311+G** functionals. We found that both enantiomers of hydrogen peroxide bind more strongly to L-serine and its clusters than to D-serine, especially highlighting that the L form is the predominant natural form of this and other chiral amino acids. The optimized geometric parameters, interaction energies, and HOMO-LUMO energies for various complexes were estimated. Furthermore, circular dichroism (CD) spectra, which are optical chirality characteristics, were simulated for all the complexes under study. Full article

Most optical phenomena result from the interaction of electromagnetic waves with matter. However, the light structure can be eminently more complex than plane waves, with many degrees of freedom and dimensions involved, yielding intricate configurations. Light transcends the conventional landscape of electromagnetism, offering the possibility to tailor light in three dimensions (intermixing all three electric field components), in four-dimensional spacetime (for fields manifesting both temporal and spatial patterns), and, beyond that, to make structured quantum light, tuning its characteristics at an unprecedented new level of control. This article addresses the physical foundations of structured light, its interactions with matter, including the nonlinear regime and probing chirality, its classical benefits with holography as a specific highlight, and quantum mechanical applications. It describes the various applications connecting structured light with material physics, quantum information, and technology. Notably, we discuss weak measurements with structured light acting as the meter with connections to probing structured-light beam shifts at interfaces. Ultimately, revealing the interplay between structured light and matter opens attractive avenues for different new technologies and applications, covering both the classical and the quantum realms. Full article

Metasurfaces can flexibly manipulate electromagnetic waves by engineering subwavelength structures, which have attracted enormous attention in holography, cloaking, and functional multiplexing. For structures with n-fold (n > 2) rotational symmetry, they have been utilized to realize broadband and high-efficiency wavefront manipulation with generalized Pancharatnam–Berry phase, whereas spin-selective wavefront manipulation is still a challenge limited by their symmetrical spin–orbit interactions. Here, we demonstrate the spin-selective wavefront manipulations with generalized Pancharatnam–Berry phase in the range of 560–660 nm with a metal–insulator–metal metasurface consisting of the chiral C3 logarithmic spiral nanostructures. As a proof of concept, two deflectors and a bifocal metalens are designed. This configuration may provide a platform for various applications in polarimetry, polarization-selective images, and nonlinear optical responses. Full article

A new hydrazone Schiff base bridging ligand (H₂L_Schiff (E)-N′-((1-hydroxynaphthalen-2-yl)methylene)pyrazine-2-carbohydrazide) and L/D-proline were used to construct a pair of homochiral Dy₆ cluster complexes, [Dy₆(CO₃)(L-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (L-1, L-HPro = L-proline; DMA = N,N-dimethylacetamide) and [Dy₆(CO₃)(D-Pro)₆(L_Schiff)₄(HL_Schiff)₂]·5DMA·2H₂O (D-1, D-HPro = D-proline), which show a novel triangular Dy₆ topology. Notably, the fixation of CO₂ in the air formed a carbonato central bridge, playing a key role in assembling L-1/D-1. Magnetic measurements revealed that L-1/D-1 displays intramolecular ferromagnetic coupling and magnetic relaxation behaviours. Furthermore, L-1/D-1 shows a distinct magneto-optical Faraday effect and has a second harmonic generation (SHG) response (1.0 × KDP) at room temperature. The results show that the immobilization of CO₂ provides a novel pathway for homochiral multifunctional 4f cluster complexes. Full article

Ibuprofen is a well-known and broadly used, nonsteroidal anti-inflammatory and painkiller medicine. Ibuprofen is a chiral compound, and its two isomers have different biological effects, therefore, their chiral separation is necessary. Ibuprofen and its derivatives were used as model compounds to establish transportable structure chiral selectivity relationships. Chiral selectors were permethylated α-, β-, and γ-cyclodextrins containing gas chromatographic stationary phases. The chiral selectivity of ibuprofen as a free acid and its various alkyl esters (methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and isoamyl esters) derivatives were tested at different temperatures. Every tested stationary phase was capable of the chiral separations of ibuprofen in its free acid form. The less strong included S optical isomers eluted before R optical isomers in every separate case. The results offer to draw transportable guidelines for the chiral selectivity vs. analyte structures. It was recognized that the S isomers of free ibuprofen acid showed an overloading phenomenon, but the R isomer did not. The results were supported by molecular modeling studies. Full article

The use of naturally sourced organic materials with chirality, such as the M13 bacteriophage, holds intriguing implications, especially in the field of nanotechnology. The chirality properties of bacteriophages have been demonstrated through numerous studies, particularly in the analysis of liquid crystal phase transitions, developing specific applications. However, exploring the utilization of the M13 bacteriophage as a template for creating chiral nanostructures for optics and sensor applications comes with significant challenges. In this study, the chirality of the M13 bacteriophage was leveraged as a valuable tool for generating helical hybrid structures by combining it with nanoparticles through an evaporation-induced three-dimensional (3D) printing process. Utilizing on the self-assembly property of the M13 bacteriophage, metal nanoparticles were organized into a helical chain under the influence of the M13 bacteriophage at the meniscus interface. External parameters, including nanoparticle shape, the ratio between the bacteriophage and nanoparticles, and pulling speed, were demonstrated as crucial factors affecting the fabrication of helical nanostructures. This study aimed to explore the potential of chiral nanostructure fabrication by utilizing the chirality of the M13 bacteriophage and manipulating external parameters to control the properties of the resulting hybrid structures. Full article

This study focused on utilizing cellulose nanocrystal (CNC)–polyvinyl alcohol (PVA) composite in optical sensor applications to detect high humidity conditions and determine water concentration in ethanol. We focused on the composite’s effectiveness in moisture absorption to demonstrate visual color change. We demonstrated that the different molecular weights of PVA significantly affect CNC’s chiral nematic structure and moisture absorption capability. PVA with molecular weight 88 k–97 k exhibited the disintegration of its chiral nematic structure at 30 wt%, whereas low molecular weight PVA (n~1750) showed no structural disintegration even at 100 wt% concentration when analyzed through UV-Vis spectroscopy. Further, the thermal crosslinking of the CNC-PVA composite showed no significant loss of moisture sensitivity for all molecular weights of the PVA. We observed that the addition of PVA to the sulfated CNC obtained from sulfuric acid hydrolysis did not facilitate moisture absorption significantly. A CNC-PVA sensor was developed which can detect high humidity with 2 h. of exposure time. 2,2,6,6-tetramethylpiperidin-1-piperidinyloxy oxidized CNC (TEMPO-CNC) having carboxylic functionality was also used to prepare the CNC-PVA composite films for comparing the effect of functional groups on moisture sensitivity. Finally, we demonstrated a facile method for utilizing the composite as an optical sensor to detect water concentration in ethanol efficiently; thus, it can be used in polar organic solvent dehydration applications. Full article

Orthoconic antiferroelectric liquid crystals (OAFLCs) represent unique self-organized materials with significant potential for applications in photonic devices due to their sub-microsecond switching times and high optical contrast in electro-optical effects. However, almost all known OALFCs suffer from low chemical stability and short helical pitch values. This paper presents the synthesis and study results of two chiral AFLCs, featuring a four-ring structure in the rigid core and high chemical stability. The mesomorphic properties of these compounds were investigated using polarizing optical microscopy and differential scanning calorimetry. Spectrometry and electro-optical studies were employed to estimate the helical pitch, tilt angle, and spontaneous polarization of the synthesized compounds and the prepared mixtures. All studied compounds exhibit enantiotropic chiral smectic mesophases including the SmA*, the SmC*, and a very broad temperature range of the SmC_A* phase. Doping top-modern antiferroelectric mixture with synthesized compounds offers benefits such as increased helical pitch and tilt angle values without significantly influencing spontaneous polarization. This allows the prepared mixture to be regarded as an OAFLC with high optical contrast, characterized by an almost perfect dark state. These valuable physicochemical and optical properties suggest significant potential of studied materials for practical applications. Full article

A comprehensive study was performed on the supramolecular ordering and optical properties of thin nanostructured glycerohydrogel sol-gel plates based on chitosan L- and D-aspartate and their individual components in the X-ray, UV, visible, and IR ranges. Our comparative analysis of chiroptical characteristics, optical collimated transmittance, the average cosine of the scattering angle, microrelief and surface asymmetry, and the level of structuring shows a significant influence of the wavelength range of electromagnetic radiation and the enantiomeric form of aspartic acid on the functional characteristics of the sol-gel materials. At the macrolevel of the supramolecular organization, a complex topography of the surface layer and a dense amorphous–crystalline ordering of polymeric substances were revealed, while at the nanolevel, there were two forms of voluminous scattering domains: nanospheres with diameters of 60–120 nm (L-) and 45–55 nm (D-), anisometric particles of lengths within ~100–160 (L-) and ~85–125 nm (D-), and widths within ~10–20 (L-) and ~20–30 nm (D-). The effect of optical clearing on glass coated with a thin layer of chitosan L-(D-)aspartate in the near-UV region was discovered (observed for the first time for chitosan-based materials). The resulting nanocomposite shape-stable glycerohydrogels seem promising for sensorics and photonics. Full article

Chirality plays a significant part in many vital processes, and to further our level of understanding, there is a steadily growing interest in enhancing the yield of enantioselective processes. Here, a multilayer with etched grooves is activated in a Kretschmann geometry and consists of alternating platinum Pt, silica SiO₂, and silicon Si, as well as a silver Ag layer. Due to the production process, the groove surface exhibits a micrometric roughness, characterized by a typical vibrational mode at ω = 96 MHz. The mode is attributed to a localized acoustic vibration and has been detected as a transmitted signal. The outcomes of the inquiry include plasmonic amplification of the transmitted signal and its wavevector-less nature; in addition, it is shown that the signal is depolarized in reference to the incident beam because of the rough surface. When the Kretschmann scheme is combined with the depolarization brought on by the roughness, a built-in asymmetry results in a higher optical flux of spectrum photons in the depolarized plane than the co-polarized plane, resulting in distinct, enantioselective, and solely polarization-dependent spectral contrast. In conclusion, enantioselectivity is demonstrated for the D,L-penicillamine. Full article

Tröger’s base analogs (TBAs) and their derivatives are versatile, Λ-shaped, tetracyclic chiral building blocks utilized in numerous fields of research. Although various methods for the enantiopurification of TBAs have been demonstrated in the literature, none has achieved it with the use of metal–organic frameworks (MOFs). This investigation introduces a convenient and scalable method to obtain enantiopure TBAs with the formation and digestion of a chiral MOF composed of fully recoverable and non-hazardous starting materials, namely, cyclodextrin-based metal–organic framework (CD-MOF). Full article