Optical Rotation Measurements Research Articles

Measurement of Optical Rotation as a Function of Temperature using a Common-Path Heterodyne Polarimeter

Measurement of Optical Rotation as a Function of Temperature using a Common-Path Heterodyne Polarimeter

Hofmeister Ions‐Induced Thinning of Gelatin to Enhance 3D Printing Precision

AbstractHydrogel 3D printing holds immense potential in fields like personalized medicine, regenerative therapies, and organ creation, offering biocompatible structures similar to the extracellular matrix. Gelatin‐Methacryloyl (GelMA) emerges as a promising candidate, while its high viscosity poses a significant challenge, especially in vat photopolymerization‐based 3D printing. Here, a new approach is presented by using Hofmeister ionic effect to substantially reduce the viscosity of high‐content (up to 60%) Gelatin bioink at room temperature with enhanced mechanical performance of the printed structures. The thinning effect induced by chaotropic Hofmeister ions is investigated through complex viscosity analysis, optical rotation measurements, and sol–gel conversion studies. The thinning effect induced by chaotropic ions enables precise 3D printing of Gelatin hydrogel, achieving accuracy comparable to prints made with polymers. Furthermore, after polymerization, the cations of the chaotropic salt change their role to cross‐linkers, leading to stronger scaffolds that exhibit biocompatibility with robust cell attachment, proliferation, and suitability for cell growth. The combination facilitates the creation of customizable structures and high printing accuracy will promote the wide application of Gelatin in the development of patient‐specific implants, drug delivery systems, and tissue scaffolds, further improving medical treatment efficacy and personalized healthcare.

Sesquiterpene lactones from Tithonia diversifolia with ferroptosis-inducing activities

Eight previously undescribed sesquiterpene lactones (1–8), together with six known ones (9–14) were isolated from the aerial parts of Tithonia diversifolia (Hemsl.) A. Gray. The absolute configurations of these compounds were elucidated using HRMS, NMR spectroscopy, optical rotation measurements, X-ray crystallography, and ECD. Among them, sesquiterpene lactones 2–4 share a unique carbon skeleton with a rare C-3/C-4 ring-opened structure. Compounds 1 and 8 showed moderate inhibitory effects toward CT26 murine colon carcinoma cells by promoting lipid ROS production, highlighting their potential as ferroptosis inducers.

Total Synthesis of Homoseongomycin Enantiomers and Evaluation of Their Optical Rotation.

A total synthesis of each homoseongomycin enantiomer was accomplished in 17 total steps (longest linear sequence = 12 steps) and 10 chromatographic purifications. Several schemes were attempted to forge the key 5-membered ring, but only a Suzuki coupling-intramolecular Friedel-Crafts acylation sequence proved viable. Challenges encountered during the optical rotation characterization of the natural product left us with two important takeaways. First, highly colored compounds like homoseongomycin that absorb near/at the sodium d-line may require optical rotation measurements at other wavelengths. Second, high dilution of such compounds to obtain measurement at the sodium d-line could result in artificially large and incorrectly assigned specific rotations. To verify the optical rotation, electronic circular dichroism spectra were acquired for both homoseongomycin enantiomers and were transformed into optical rotary dispersions via the Kramers-Kronig transform. We note the wavelength dependency on rotation, and at the sodium d-line 589 nm, we reassign the optical rotation of L-homoseongomycin from (-) to (+).

Ultra-sensitive measurement of small optical rotation angles using quantum entanglement based on a quasi-Wollaston prism beam splitter

The measurement of optical rotation is fundamental to optical atomic magnetometry. Ultra-high sensitivity has been achieved by employing a quasi-Wollaston prism as the beam splitter within a quantum entanglement state, complemented by synchronous detection. Initially, we designed a quasi-Wollaston prism and intentionally rotated the crystal axis of the exit prism element by a specific bias angle. A linearly polarized light beam, incident upon this prism, is divided into three beams, with the intensity of each beam correlated through quantum entanglement. Subsequently, we formulated the equations for optical rotation angles by synchronously detecting the intensities of these beams, distinguishing between differential and reference signals. Theoretical analysis indicates that the measurement uncertainty for optical rotation angles, when using quantum entanglement, exceeds the conventional photon shot noise limit. Moreover, we have experimentally validated the effectiveness of our method. In DC mode, the experimental results reveal that the measurement uncertainty for optical rotation angles is 4.7 × 10−9 rad, implying a sensitivity of 4.7 × 10−10 rad/Hz1/2 for each 0.01 s measurement duration. In light intensity modulation mode, the uncertainty is 48.9 × 10−9 rad, indicating a sensitivity of 4.89 × 10−9 rad/Hz1/2 per 0.01 s measurement duration. This study presents a novel approach for measuring small optical rotation angles with unprecedentedly low uncertainty and high sensitivity, potentially playing a pivotal role in advancing all-optical atomic magnetometers and magneto-optical effect research.

Chiral Metasurfaces: A Review of the Fundamentals and Research Advances

Chirality, the absence of mirror symmetry, is predominant in nature. The chiral nature of the electromagnetic field behaves differently with chiral matter for left circularly polarized and right circularly polarized light. The chiroptical behavior in the sensing of naturally occurring chiral objects is weak, and improving the chiroptical response enhances the chiral sensing platform. This review covers the fundamental concepts of chiral metasurfaces and various types of single- and multi-layered chiral metasurfaces. In addition, we discuss tunable and deep-learning-based chiral metasurfaces. Tunability is achieved by manipulating the meta-atom’s property in response to external stimuli for applications such as optical modulation, chiral photonics, advanced sensing, and adaptive optics. Deep-learning modeling techniques, such as CNNs and GANs, offer efficient learning of the complex relationships in data, enabling the optimization and accurate prediction of chiral metasurface properties. The challenges in the design and fabrication of chiral metasurface include achieving broadband performance and scalability and addressing material limitations. Chiral metasurface performance is evaluated by optical rotation, circular dichroism enhancement, and tunability, which are quantified through the spectroscopic measurement of circular dichroism and optical rotation. Chiral metasurface progress enables applications, including metaholography, metalenses, and chiral sensing. Chiral sensing improves the detection of pharmaceuticals and biomolecules, increasing the sensitivity and accuracy of analytical diagnostics.

Unconventional specular optical rotation in the charge ordered state of Kagome metal CsV3Sb5

Kagome metals AV3Sb5 (A = K, Cs, Rb) provide a rich platform for intertwined orders, where evidence for time-reversal symmetry breaking, likely due to the long-sought loop currents, has emerged in STM and muon spin relaxation experiments. An isotropic component in the spontaneous optical rotation has also been reported and was interpreted as the magneto-optic Kerr effect. Intriguingly, the observed rotations differ by five orders of magnitude between different wavelengths and samples, suggesting more intricate physics. Here we report optical rotation and polar Kerr measurements in CsV3Sb5 crystals at the same wavelength. We observe large isotropic components of 1 milliradian in the optical rotation that do not respond to applied magnetic fields, while the spontaneous Kerr signal is less than 20 nanoradians. Our results prove unambiguously that the reported isotropic rotation is not from time-reversal symmetry breaking but represents the long-sought specular optical rotation and indicates a new intertwined order.

Identification of Ecdysteroid Sinapate Esters with COX-2 Inhibitory Effects from Fibraurea recisa Using Molecular Networking and MS2LDA.

The roots of Fibraurea recisa are recognized as a rich source of protoberberine and aporphine alkaloids, but the non-alkaloidal metabolites in this plant are underexplored. The present study investigated the chemical composition of the plant roots using untargeted metabolomics-based molecular networking and MS2LDA motif annotation, revealing the presence of a characteristic fragment motif related to several sinapoyl-functionalized metabolites. Guided by the targeted motif, two new sinapic acid-ecdysteroid hybrids, named 3-O-sinapoyl makisterone A (1) and 2-O-sinapoyl makisterone A (2), were isolated. The structures of these compounds, including their absolute configuration, were elucidated by HR-ESIQTOFMS, MS2 fragmentation, NMR spectroscopy, and chemical degradation coupled with optical rotation measurements. Although neither compound inhibited nitric oxide (NO) production or inducible nitric oxide synthase (iNOS) protein expression on lipopolysaccharide-induced RAW 264 cells, 2 significantly suppressed cyclooxygenase 2 (COX-2) protein expression at 1-30 μM. Additionally, decreased expression of COX-2 protein was barely observed after treatment with methyl sinapate or makisterone A, the steroid skeleton of 1 and 2. These results indicated that the presence of the sinapoyl moiety at C-2 on the C28-ecdysteroid skeleton played a key role in the selectivity for the suppression of the COX-2 protein expression.

Observation of Exceptional Points in Thermal Atomic Ensembles.

Exceptional points (EPs) in non-Hermitian systems have recently attracted wide interest and spawned intriguing prospects for enhanced sensing. However, EPs have not yet been realized in thermal atomic ensembles, which is one of the most important platforms for quantum sensing. Here we experimentally observe EPs in multilevel thermal atomic ensembles and realize enhanced sensing of the magnetic field for 1 order of magnitude. We take advantage of the rich energy levels of atoms and construct effective decays for selected energy levels by employing laser coupling with the excited state, yielding unbalanced decay rates for different energy levels, which finally results in the existence of EPs. Furthermore, we propose the optical polarization rotation measurement scheme to detect the splitting of the resonance peaks, which makes use of both the absorption and dispersion properties and shows an advantage with enhanced splitting compared with the conventional transmission measurement scheme. Additionally, in our system both the effective coupling strength and decay rates are flexibly adjustable, and thus the position of the EPs are tunable, which expands the measurement range. Our Letter not only provides a new controllable platform for studying EPs and non-Hermitian physics, but also provide new ideas for the design of EP-enhanced sensors and opens up realistic opportunities for practical applications in the high-precision sensing of magnetic field and other physical quantities.

System analysis of a common-path heterodyne polarimeter

We proposed a polarimeter combining the common-path heterodyne interferometry (CPHI) with a half-wave plate. When the azimuth of the wave plate is at 22.5 degrees, it has the best resolution for optical rotation (OR) measurement. The purpose of this paper is to analyze all possible sources of error in the system. The retardation closer to the true half wavelength, the higher the resolution will be. A large phase change of the test signal relative to the reference signal can be found by a lock-in amplifier. The system phase error is approximately 0.06∘. The accuracy of optical rotation is 1.0 × 10−3 degrees for the phase retardation is 178.08∘. The concentration resolution can reach 1.6×10−3[gdl] for fructose solutions. The magnitude of the phase error depends on the stability of the optical system and whether the two interfering lights coincide exactly. If the phase error can be reduced to 0.01∘, the resolution of OR can be increased to 1.3×10−4∘.

Synthesis of l-Rare Sugars from d-Sorbitol Using a TiO2 Photocatalyst

In recent years, l-rare sugars have been attracting attention, both as active compounds and useful building blocks for use in the pharmaceutical industry; however, these compounds have low natural abundances and cannot be extracted from natural products. Therefore, it is necessary to convert widely available substrates, such as biomass-derived compounds, to produce rare sugars. In this study, we examined the production of l-rare sugars using a TiO2 photocatalyst. d-Sorbitol was treated with a TiO2 photocatalyst under light irradiation, and the products were identified as glucose, gulose, fructose, sorbose, arabinose, xylose, erythrose, threose, and glyceraldehyde using high-performance liquid chromatography, liquid chromatography–mass spectrometry, and proton nuclear magnetic resonance spectroscopy. Furthermore, the production of the l-rare sugars, l-gulose and l-xylose, was confirmed by optical rotation measurements. Analysis of the product concentrations as a function of time suggested that d-sorbitol undergoes a decarbonization reaction and C–C bond cleavage when treated with a TiO2 photocatalyst.

New Indole Diketopiperazine Alkaloids from Soft Coral-Associated Epiphytic Fungus Aspergillus versicolor CGF 9-1-2.

Two new indole diketopiperazine alkaloids (IDAs), (+)19-epi-sclerotiamide (1) and (-)19-epi-sclerotiamide (2), along with 13 known analogs (3-15), were isolated from a soft coral-associated epiphytic fungus Aspergillus versicolor CGF 9-1-2. The structures of two new compounds were established based on the combination of HR-ESI-MS, 1D and 2D NMR spectroscopy, optical rotation measurements and quantum chemical 13 C-NMR, the absolute configurations were determined by experimental and electronic circular dichroism (ECD) calculations. The results of molecular docking showed that all the compounds had a good binding with TDP1, TDP2, TOP1, TOP2, Ache, NLRP3, EGFR, EGFR L858R, EGFR T790M and EGFR T790/L858. Biological evaluation of compounds 3, 6, 8, 11 showed that 3 exerted a strong inhibitory effect on TDP2 with a rate of 81.72 %.

Analysis of atomic magnetometry using metasurface optics for balanced polarimetry.

Atomic magnetometry is one of the most sensitive field-measurement techniques for biological, geo-surveying, and navigational applications. An essential process in atomic magnetometry is measurement of optical polarization rotation of a near-resonant beam due to its interaction with atomic spins under an external magnetic field. In this work, we present the design and analysis of a silicon-metasurface-based polarization beam splitter that have been tailored for operation in a rubidium magnetometer. The metasurface polarization beam splitter operates at a wavelength of 795 nm and has a transmission efficiency > 83% and a polarization extinction ratio > 20 dB. We show that these performance specifications are compatible with magnetometer operation in miniaturized vapor cells with sub-picotesla-level sensitivity and discuss the prospect of realizing compact, high-sensitivity atomic magnetometers with nanophotonic component integration.

Mystery in the Palm of Your Hand: Chiral Identification Using Optical Rotation Measurements and Specificity for Chiral Pollution Detection

Mystery in the Palm of Your Hand: Chiral Identification Using Optical Rotation Measurements and Specificity for Chiral Pollution Detection

Gate tunable spatial accumulation of valley-spin in chemical vapor deposition grown 40°-twisted bilayer WS2

The emerging two-dimensional materials, particularly transition metal dichalcogenides (TMDs), are known to exhibit valley degree of freedom with long valley lifetime, which hold great promises in the implementation of valleytronic devices. Especially, light–valley interactions have attracted attentions in these systems, as the electrical generation of valley magnetization can be readily achieved — a rather different route toward magnetoelectric (ME) effect as compared to that from conventional electron spins. However, so far, the moiré patterns constructed with twisted bilayer TMDs remain largely unexplored in regard of their valley spin polarizations, even though the symmetry might be distinct from the AB stacked bilayer TMDs. Here, we study the valley Hall effect (VHE) in 40°-twisted chemical vapor deposition (CVD) grown WS2 moiré transistors, using optical Kerr rotation measurements at 20 K. We observe a clear gate tunable spatial distribution of the valley carrier imbalance induced by the VHE when a current is exerted in the system.

Anion specific conformational change in aqueous gellan gum solutions

127I NMR is applied to investigate the motional state and the selective interaction of I− ions in tetramethylammonium form of gellan gum (TMA gellan), together with monitoring the conformational change by the optical rotation measurement. The experimental results indicate that I− ion promotes the conformational transition, and there exists the preferential affinity of I− ion for the ordered conformation of TMA gellan.

Synthesis of (-)-halichonic acid and (-)-halichonic acid B.

The first syntheses of the amino acids (-)-halichonic acid and (-)-halichonic acid B have been achieved in ten steps starting from commercially available (-)-α-bisabolol. The optimized synthetic route includes a new purification method for isolating (-)-7-amino-7,8-dihydrobisabolene in enantiomerically pure form via recrystallization of its benzamide derivative. The key intramolecular aza-Prins reaction forms the characteristic 3-azabicyclo[3.3.1]nonane ring system of halichonic acid along with the lactonized form of halichonic acid B in an 8:1 ratio. Optical rotation measurements confirmed that these synthetic compounds were in fact the enantiomers of the natural products, establishing both the relative and absolute configurations of the halichonic acids.

Simultaneous formation of two-fold rotation symmetry with charge order in the kagome superconductor CsV3Sb5 by optical polarization rotation measurement

We report the observation of two-fold rotation symmetry in charge density wave (CDW) state in the newly discovered Kagome superconductor CsV$_3$Sb$_5$. Below its CDW transition temperature ($T_{CDW}$), the polarization rotation of the reflected laser beam promptly emerges and increases close to about 1 mrad, and the rotation angle shows two-fold rotation symmetry. With femtosecond laser pulse pumping, the rotation angle can be easily suppressed and then recovers in several picoseconds accompanied with coherent oscillations. Significantly, the oscillations in the signal also experience a 180 degree periodic change. Our investigation provides clear optical evidence for the formation of nematic order with two-fold rotation symmetry just below $T_{CDW}$. The results imply a immediate development of nematicity and possible time-reversal symmetry breaking in CDW state of CsV$_3$Sb$_5$.

Enhanced room-temperature spin-valley coupling in V-doped MoS2

Achieving room-temperature valley polarization in two-dimensional (2D) atomic layers (2D materials) by substitutional doping opens new avenues of applications. Here, monolayer ${\mathrm{MoS}}_{2}$, when doped with vanadium at low (0.1 atomic %) concentrations, is shown to exhibit high spin-valley coupling, and hence a high degree of valley polarization at room-temperature. The atomic layers of ${\mathrm{MoS}}_{2}$ (MS) and V-doped ${\mathrm{MoS}}_{2}$ (VMS) are grown via the chemical vapor deposition-assisted method. The formation of new energy states near the valence band is confirmed from band gap calculations and also from the density functional theory--based band structure analyses. Time-reversal symmetry broken energy shift in the equivalent valleys is predicted in VMS, and the room-temperature chirality-controlled photoluminescent (PL) excitation measurements indicate such a shift in valley exciton energies (\ensuremath{\sim}35 meV). An enhanced valley polarization in VMS (\ensuremath{\sim}42%) is observed in comparison to that in MS (12%), while in MS, the chirality-controlled excitations did not show the difference in emission energies. Spin Hall effect of light--based optical rotation measurements indicate the asymmetric absorption among the two different chiralities of the incident light, hence supporting the existence of room-temperature valley polarization. This study opens possibilities of room-temperature opto-spintronics using stable 2D materials.

Optical Rotation and Transmittance of Different Phases of Ferroelectric Liquid Crystal Sample ZLI 3654

Objectives: The Phase transition scheme of Ferroelectric Liquid Crystal (FLC) sample has been studied in a temperature range 500C to 950C. Methods: The material was procured from Merck, Germany and was used as such without any further purification, and studied for the measurement of optical rotation and transmittance. The Polarizing Optical Microscopy (POM) technique has been used and the different phases existing in the sample were observed by placing the sample having planar alignment under crossed polarizer arrangement. Findings: The sharp variation in the values of optical rotation and transmittance at the phase transition points clearly indicates that the different phases exist in the experimental sample. From the LDR vs Temperature and Optical Rotation vs Temperature study, four different phases for the sample were obtained. The SmC* phase exists in the temperature range 300C – 620C and at 620C, the SmA* occurs. The sample shows SmA* phase in the temperature range 620C – 760C and at 760C sample transit to Nematic phase which occurs in the temperature range 760C – 860C and lastly, Isotropic phase appears at 860C. Novelty: Some researchers have studied the same sample but in the temperature range 300C to 620C where they were able to observe only two initial phases namely SmC* and SmA* whereas the present study reports the four different phases (SmC*, SmA*, nematic and isotropic) of the Ferroelectric Liquid Crystal (FLC). The same study can also be carried out using the other technique like Differential Scanning Calorimetry (DSC) but the technique used in the present study is simpler and cost-effective. The same technique can also be applied to other liquid crystal samples to study their phase transition behaviour. Keywords: Ferroelectric Liquid Crystal, Optical Rotation, Optical Transmittance, Polarizing Microscope, Phase Transition