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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Reversible Ferroelectric Polarization Modulation of Chiral Molecular Ferroelectrics by Circularly Polarized Light

Abstract The optical modulation of ferroelectric polarization constitutes a transformative, non‐contact strategy for the precise manipulation of ferroelectric properties, heralding advancements in optically stimulated ferroelectric devices. Despite its potential, progress in this domain is constrained by material limitations and the intricate nature of the underlying mechanisms. Recent studies have achieved efficient regulation of ferroelectric polarization and thermal conductivity in chiral ferroelectric thin films through the application of left‐ and right‐handed circularly polarized light (LCP and RCP). Differential absorption of circularly polarized light (CPL) induces nonequilibrium carrier dynamics, generating distinctive interfacial electrostatic fields that enable precise control of ultrathin ferroelectric films. For (R)‐BINOL−DIPASi and (S)‐BINOL−DIPASi (C 26 H 26 O 2 Si), polarization changes surpass 23%, exhibiting opposite response under LCP and RCP excitation. In R chiral films, remnant polarization decreases from 1.05 µC cm − 2 under LCP to 0.85 µC cm − 2 under RCP, whereas in S chiral films, polarization increases from 0.85 µC cm − 2 under LCP to 0.98 µC cm − 2 under RCP. This reversible modulation facilitates reliable switching between ON and OFF states, presenting the potential of chiral ferroelectric materials for flexible, high‐speed integrated photonic sensor technologies.

Chemistry↗
DOE OSTI2023

Hybrid Monomer Design Synergizing Property Trade‐offs in Developing Polymers for Circularity and Performance

Abstract Current search for more sustainable plastics seeks to redesign polymers possessing both chemical recyclability to monomer for a circular plastics economy and desirable performance that can rival or even exceed today's non‐recyclable or hard‐to‐recycle petroleum‐based incumbents. However, within a traditional monomer framework it is challenging to optimize, concurrently , contrasting polymerizability/depolymerizability and recyclability/performance properties. Here, we highlight the emerging hybrid monomer design strategy to develop intrinsically circular polymers with tunable performance properties, aiming to unify desired, but otherwise conflicting, properties in a single monomer. Conceptually, this design hybridizes parent monomer pairs of contrasting, mismatching, or matching properties into offspring monomers that not only unify the above‐described conflicting properties but also radically alter the resultant polymer properties far beyond the limits of what either parent homopolymers or their copolymers can achieve.

Shi, Changxia↗
DOE OSTI2024

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

Abstract 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 ( g lum ) 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 | g lum | 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.

Tang, Xihao↗
DOE OSTI2025

Closed‐Loop Recyclable Vitrimer Plastics from PET Waste: A Design for Circularity

Plastics are essential to modern society, but their low recycling rates and inefficient end-of-life management pose a significant environmental challenge. Herein, the efficient strategy for upcycling postconsumer poly(ethylene terephthalate) (PET) waste into robust, closed-loop recyclable vitrimer plastics and composites is presented to address this issue. The catalyst-free aminolysis utilizes readily available amines to deconstruct diverse PET wastes into macromonomers, which are upcycled into vitrimers, exhibiting superior mechanical properties and exceeding the ultimate tensile stress and Young's Modulus of virgin PET by 80% and 150% respectively. These vitrimers exhibit excellent healability, shape memory, thermal reprocessability, and closed-loop chemical recyclability, enabling quantitative macromonomer recovery even from mixed plastic waste streams and glass/carbon fiber reinforced vitrimer (G/CFRV) composites. Furthermore, the vitrimer resin yields robust GFRV and CFRV composites with tensile strengths exceeding those of traditional epoxy composites by 100% and 80%, respectively, while maintaining complete chemical recyclability of both constituent materials. A preliminary technoeconomic analysis confirms the costeffectiveness and competitiveness of the facile PET deconstruction approach, which is potentially adaptable to other condensation polymers. Further, this study presents a facile approach to upcycling plastic waste into circular plastics and composites, offering a sustainable solution to global plastic waste management and fostering a circular economy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Steady state quantum discord for circularly accelerated atoms

We study, in the framework of open quantum systems, the dynamics of quantum entanglement and quantum discord of two mutually independent circularly accelerated two-level atoms in interaction with a bath of fluctuating massless scalar fields in the Minkowski vacuum. We assume that the two atoms rotate synchronically with their separation perpendicular to the rotating plane. The time evolution of the quantum entanglement and quantum discord of the two-atom system is investigated. For a maximally entangled initial state, the entanglement measured by concurrence diminishes to zero within a finite time, while the quantum discord can either decrease monotonically to an asymptotic value or diminish to zero at first and then followed by a revival depending on whether the initial state is antisymmetric or symmetric. When both of the two atoms are initially excited, the generation of quantum entanglement shows a delayed feature, while quantum discord is created immediately. Remarkably, the quantum discord for such a circularly accelerated two-atom system takes a nonvanishing value in the steady state, and this is distinct from what happens in both the linear acceleration case and the case of static atoms immersed in a thermal bath.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Circular RNA hsa-circ-0010729 regulates vascular endothelial cell proliferation and apoptosis by targeting the miR-186/HIF-1α axis

Circular RNAs (circRNAs) are a group of non-protein-coding RNAs generated from back splicing. Emerging evidence has demonstrated its vital regulation on angiogenesis. However, the underlying mechanism responsible for circRNAs effects on vascular endothelial cells is still unclear. In the present study, we screened the expression profiles and investigated the physiological role of circRNAs in hypoxia-induced human umbilical vein endothelial cells (HUVECs). Using circRNA microarray analysis, we identified 36 circRNAs that were significantly dysregulated including 14 down-regulated circRNAs and 22 up-regulated with 2-fold change (P < 0.05). From the over-expressed circRNAs, hsa-circ-0010729 was selected as candidate circRNA and which was validated to be significantly up-regulated using RT-PCR. In loss-of-function experiments of HUVECs, hsa-circ-0010729 knockdown suppressed the proliferation and migration ability and enhanced apoptosis. Bioinformatic prediction and luciferase assay revealed that hsa-circ-0010729 and hypoxia inducible factor 1 alpha (HIF-1α) were targeted by miR-186. Validation experiments verified that hsa-circ-0010729 was co-expressed with HIF-1α, being negatively correlated with miR-186. Moreover, rescue experiments demonstrated that miR-186 inhibitor could reverse the role of hsa-circ-0010729 knockdown on HUVECs progression. Overall, the present study identifies the crucial regulation of hsa-circ-0010729 on vascular endothelial cell proliferation and apoptosis via targeting miR-186/HIF-1α axis. - Highlights: • Circular RNA expression profile identifies hsa-circ-0010729 is up-regulated in hypoxia-induced HUVECs. • Hsa-circ-0010729 knockdown suppresses the proliferation and migration ability, and enhanced the apoptosis. • Hsa-circ-0010729 acts as an endogenous sponge of miR-186. • HIF-1α is targeted by miR-186. • Hsa-circ-0010729 regulates vascular endothelial cells proliferation and apoptosis via targeting miR-186/HIF-1α axis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Androgen-responsive circular RNA circSMARCA5 is up-regulated and promotes cell proliferation in prostate cancer

Prostate cancer (PCa) is one of the most commonly diagnosed cancers in males worldwide. Circular RNA (circRNA) is a unique class of RNA transcribed by RNA polymerase II characterized by jointing 3′ and 5′ ends together via exon or intron circularization. However, the molecular functions of circRNAs in prostate cancer have rarely been explored. In present study, we found circ-SMARCA5 was up-regulated in prostate cancer samples compared to match normal tissues. We also observed circ-SMARCA5 expression was significantly induced after DHT treatment. Functional experiments showed circ-SMARCA5 acted as an oncogene in prostate cancer by promoting cell cycle and inhibiting cell apoptosis. We thought this study provided useful information for exploring circRNAs as potential therapeutic and prognostic targets for prostate cancer. - Highlights: • To our knowledge, this is the first study to explore the molecular functions of circRNA in prostate cancer. • Our study showed that circ-SMARCA5 promoted cell proliferation and inhibited cell apoptosis in prostate cancer. • circ-SMARCA5 was for the first time reported as an androgen-responsive circRNA. • circ-SMARCA5 was for the first time reported to be up-regulated in prostate cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

A novel circular RNA, hsa{sub c}irc{sub 0}046701, promotes carcinogenesis by increasing the expression of miR-142-3p target ITGB8 in glioma

Highlights: • We identified a novel circular RNA, hsa{sub c}irc{sub 0}046701 in glioma cells. • Hsa{sub c}irc{sub 0}046701 was significantly upregulated in glioma tissues. • Hsa{sub c}irc{sub 0}046701 sponges miR-142-3p in glioma. • MiR-142-3p directly targets ITGB8 in glioma. • Hsa{sub c}irc{sub 0}046701/miR-142-3p/ITGB8 axis plays critical roles in glioma pathogenesis. In the present study, we identified a novel circular RNA (circRNA), hsa{sub c}irc{sub 0}046701, in glioma cells. We measured the expression of hsa{sub c}irc{sub 0}046701 using qRT-PCR in glioma tissues and cell lines, and explored its functions using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation, and Transwell assays. Luciferase reporter assays were performed to validate the correlation between microRNA miR-142-3p and hsa{sub c}irc{sub 0}046701 or integrin subunit beta 8 (ITGB8). The results showed that hsa{sub c}irc{sub 0}046701 was significantly upregulated in glioma tissues and cell lines, and knockdown of hsa{sub c}irc{sub 0}046701 inhibited cell proliferation and invasion. Luciferase reporter assays indicated that hsa{sub c}irc{sub 0}046701 functions as a sponge for miR-142-3p and regulates the expression of ITGB8. Subsequently, functional assays revealed that silencing of hsa{sub c}irc{sub 0}046701 could upregulate miR-142-3p, resulting in downregulation of ITGB8. The results demonstrated that the hsa{sub c}irc{sub 0}046701/miR-142-3p/ITGB8 axis might play critical regulatory roles in the pathogenesis and development of glioma.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Alterations of circular RNAs in hyperglycemic human endothelial cells

Circular RNA (circRNA), a family of RNA generated by RNA circularization, is ubiquitously expressed in tissues and possesses increasingly important biological functions. Hyperglycemia-induced endothelial dysfunction is an initiating event in the pathogenesis of diabetes-associated cardiovascular complications. How high glucose may affect circRNAs is unknown. To address this issue, human endothelial cells were exposed to high glucose treatment and the changes of circRNAs were measured by RNA sequencing. A total 3686 circRNAs, including 1040 previously unrecorded circRNAs, were detected; and 95 different expression (DE) circRNAs were observed. The host genes of these DE circRNAs were further studied by function enrichment analyses. These analyses revealed genes of phosphoproteins, transferases, and zine finger proteins. Since circRNAs can function as a microRNA (miRNA) sponge, circRNAs-miRNAs interaction networks were explored by bioinformatics. These analyses identified a number of miRNAs, which might interact with DE circRNAs and play roles in the actions of high glucose on endothelial cells. These results demonstrate that high glucose exposure profoundly changes circRNA expression in endothelial cells. Altered circRNA expression may contribute to the effects of high glucose on endothelial function in diabetes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Developing a circularly permuted variant of Renilla luciferase as a bioluminescent sensor for measuring Caspase-9 activity in the cell-free and cell-based systems

Highlights: • A luciferase based biosensor for measuring caspase-9 activity has been constructed using circular permutation strategy. • The designed biosensor detects the caspase-9 activity in a cell-free coupled assay system. • The designed biosensor can be implemented as a cell-based biosensor to detect cellular caspase-9 activity and apoptosis. Biosensors and whole cell biosensors consisting of biological molecules and living cells can sense a special stimulus on a living system and convert it to a measurable signal. A major group of them are the bioluminescent sensors derived from luciferases. This type of biosensors has a broad application in molecular biology and imaging systems. In this project, a luciferase-based biosensor for detecting and measuring caspase-9 activity is designed and constructed using the circular permutation strategy. The spectroscopic method results reveal changes in the biosensor structure. Additionally, its activity is examined in a cell-free coupled assay system. Afterward, the biosensor is utilized for measuring the cellular caspase-9 activity upon apoptosis induction in a cancer cell line. In following the gene of biosensor is sub-cloned into a eukaryotic vector and transfected to HEK293T cell line and then its activity is measured upon apoptosis induction in the presence and absence of a caspase-9 inhibitor. The obtained results show that the designed biosensor detects the caspase-9 activity in the cell-free and cell-based systems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Circular dichroism in hard X-ray photoelectron diffraction observed by time-of-flight momentum microscopy

X-ray photoelectron diffraction (XPD) is a powerful technique that yields detailed structural information of solids and thin films that complements electronic structure measurements. Among the strongholds of XPD we can identify dopant sites, track structural phase transitions, and perform holographic reconstruction. High-resolution imaging of k ll -distributions (momentum microscopy) presents a new approach to core-level photoemission. It yields full-field k x -k y XPD patterns with unprecedented acquisition speed and richness in details. Here, we show that beyond the pure diffraction information, XPD patterns exhibit pronounced circular dichroism in the angular distribution (CDAD) with asymmetries up to 80%, alongside with rapid variations on a small k ll -scale (0.1 Å -1 ). Measurements with circularly-polarized hard X-rays (hν = 6 keV) for a number of core levels, including Si, Ge, Mo and W, prove that core-level CDAD is a general phenomenon that is independent of atomic number. The fine structure in CDAD is more pronounced compared to the corresponding intensity patterns. Additionally, they obey the same symmetry rules as found for atomic and molecular species, and valence bands. Further, the CD is antisymmetric with respect to the mirror planes of the crystal, whose signatures are sharp zero lines. Calculations using both the Bloch-wave approach and one-step photoemission reveal the origin of the fine structure that represents the signature of Kikuchi diffraction. To disentangle the roles of photoexcitation and diffraction, XPD has been implemented into the Munich SPRKKR package to unify the one-step model of photoemission and multiple scattering theory.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Improving the circular economy via hydrothermal processing of high-density waste plastics

Highlights: • High-density plastics are susceptible to supercritical hydrothermal processing. • Plastics convert into their monomers and value-added chemical compounds. • Nearly 100% conversion of PC into synthetic crude oil. • Degradation of PET and PBT yields high quantity of their monomer terephtalic acid. • Hydrothermal processing is a prospective technology for unrecyclable waste plastics. - Abstract: Rising environmental concerns on climate changes are causing an increasing attention on circular economies. The plastic economy, in particular, is in focus due to the accelerating consumption of plastics, mainly derived from virgin feedstock, combined with the lack of plastic recycling strategies. This work presents a novel outlook on the potential of using supercritical hydrothermal processing of waste plastic fractions for tertiary recycling. The study investigates hydrothermal processing of nine different, high-density types of plastics into original resin monomers and other value-added chemical compounds. The outlook presents conversion yields, carbon balances, and chemical details on the products obtained. It is found that all the investigated resins are prone to hydrothermal treatment, and that high yields of monomers and high value compounds (up to nearly 100%), suitable for chemicals and fuels applications, can be obtained. For instance, for polycarbonate, styrene-butadiene, poly(lactic acid), poly(ethylene terephthalate), and poly(butylene terephthalate), original monomeric compounds can be reclaimed for manufacturing new resins. The promising results presented demonstrate that hydrothermal processing of high-density plastics is a prospective technology for increasing the circularity of the plastic economy.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Relativistic Effects in Magnetic Circular Dichroism: Restricted Magnetic Balance and Temperature Dependence

Magnetic circular dichroism of transition metal complexes and open-shell systems are challenging to simulate and analyze, mainly due to the interplay of spin–orbit couplings and finite-magnetic-field induced Zeeman effects with the complex selection rules dictated by the circularly polarized light. In this study, we introduce an ab initio relativistic two-component formalism based on the restricted magnetic-balanced Hamiltonian for simulating MCD spectra. Both homogeneous finite magnetic field and relativistic effects are included variationally in the ground state reference. Finite-field London orbitals are used to enforce the constrained gauge-origin independence in the calculation using localized atomic orbitals. Through benchmark studies of AuCl 4 – , Pt(CN) 4 2– , and Mo(CN) 8 3– , we discuss how relativistic effects are manifested in MCD for both closed-shell and open-shell molecular complexes and how the interplay between spin–orbit coupling and magnetic field modulates the MCD selection rules. Finally, an investigation on temperature-dependent MCD is carried out and compared to experiment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Toward an Understanding of the Excitonic Structure of the CP47 Antenna Protein Complex of Photosystem II Revealed via Circularly Polarized Luminescence

Identification of the lowest energy pigments in the photosynthetic CP47 antenna protein complex of Photosystem II (PSII) is essential for understanding its excitonic structure, as well as excitation energy pathways in the PSII core complex. Unfortunately, there is no consensus concerning the nature of the low-energy state(s) nor chlorophyll (Chl) site energies in this important photosynthetic antenna. Although, we raised concerns regarding the estimations of Chl site energies obtained from modeling studies of various types of CP47 optical spectra [Reinot, T; et al., Anal. Chem. Insights 2016, 11, 35–48] recent new assignments imposed by the shape of the circularly polarized luminescence (CPL) spectrum [Hall, J.; et al., Biochim. Biophys. Acta 2016, 1857, 1580–1593] necessitate our comments. We demonstrate that other combinations of lowenergy Chls provide equally good or improved simultaneous fits of various optical spectra (absorption, emission, CPL, circular dichroism, and nonresonant hole-burned spectra), but more importantly, we expose the heterogeneous nature of the recently studied complexes and argue that the published composite nature of the CPL (contributed to by CPL 685 , CPL 691 , and CPL 695 ) does not represent an intact CP47 protein. A positive CPL 695 is extracted for the intact protein, which when simultaneously fitted with multiple other optical spectra, provides new information on the excitonic structure of intact and destabilized CP47 complexes and their lowest energy state(s).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Conformational Populations of β-(1→4) O -Glycosidic Linkages Using Redundant NMR J -Couplings and Circular Statistics

Twelve disaccharides containing β-(1→4) linkages and displaying systematic structural variations in the vicinity of these linkages were selectively labeled with 13 C to facilitate measurements of multiple NMR spin–spin (scalar; J) coupling constants (J CH and J CC values) across their O-glycosidic linkages. Ensembles of spin-couplings ( 2 J COC , 3 J COCH , 3 J COCC ) sensitive to the two linkage torsion angles, phi (Φ) and psi (ψ), were analyzed by using parametrized equations obtained from density functional theory (DFT) calculations, Fredholm theory, and circular statistics to calculate experiment-based rotamer populations for Φ and ψ in each disaccharide. With the statistical program MA’AT, torsion angles Φ and ψ were modeled as a single von Mises distribution, which yielded two parameters, the mean position and the circular standard deviation (CSD) for each angle. The NMR-derived rotamer populations were compared to those obtained from 1 μs aqueous molecular dynamics (MD) simulations and crystallographic database statistical analyses. Conformer populations obtained exclusively from the MA’AT treatment of redundant J-couplings were in very good agreement with those obtained from the MD simulations, providing evidence that conformational populations can be determined by NMR for mobile molecular elements such as O-glycosidic linkages with minimal input from theory. The approach also provides an experimental means to validate the conformational preferences predicted from MD simulations. The conformational behaviors of Φ in the 12 disaccharides were very similar, but those of ψ varied significantly, allowing a classification of the 12 disaccharides based on preferred linkage conformation in solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Depolarized Scattering from Block Copolymer Grains Using Circularly Polarized Light

The grain structure of ordered block copolymer materials affects their viscoelastic, adhesive, optical, and electrical properties. Depolarized light scattering has proven to be an important method for characterizing this grain structure. In this paper, we use both theory and experiments to demonstrate the relationship between grain structure and depolarized light scattering from ordered block copolymer samples performed with crossed circular polarizers. We model the sample assuming it comprises randomly oriented ellipsoidal grains with optic axes coincident with the ellipsoid axes. We show that the scattering pattern obtained using circularly polarized (CP) light is azimuthally symmetric, in contrast to that obtained using linearly polarized (LP) light which exhibits 4-fold angular modulation. The integrated scattered power in the CP case is twice as large as that in the LP case. Finally, by simultaneously fitting CP and LP light scattering data, we obtain robust measures of parameters that characterize grain structures. In addition, CP light scattering can, in principle, be used to characterize nonrandom grain orientation distributions.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A Visual Understanding of Circular Dichroism Spectroscopy

Mapping chemical and structural properties to electronic and magnetic responses is critical to many applications such as quantum information science, where the precise storage and transmission of unique information is paramount. Specifically, constructing molecules and materials that provide strong polarized responses at tunable frequencies and with large anisotropies is key to optical processing of quantum information. Chiral molecules provide chiroptical response to circularly polarized light, making them attractive for quantum information science and other applications related to sensing, polarized photodetectors, and spintronics. Predicting a molecular design, a priori, with large anisotropies to circularly polarized light is challenging due to the complex interplay between electric and magnetic components of the optical response. In this work, we explore a visual representation of the electronic chiroptical response by decomposing the rotary strength into its constituent components. Here, we make use of the intuitive electronic oscillator framework to develop classical intuition regarding the rotary strength and its constituents. We explore three model chemical systems that exhibit local and global chirality. Our analysis reveals that local chirality necessarily exhibits competition between the local chiral center and chirality induced in other fragments of the molecule, resulting in both unexpected nonmonotonic trends and sign flips in chemically adjacent geometries. Furthermore, we can visually distinguish between local and global chirality via examination of the transition chiral tensor. Interestingly, we make strong connections to ferromagnetic and antiferromagnetic spin systems in that chiroptically inactive transitions exhibit antiferromagnetic-like alternating orbital patterns while active transitions show domain formation in an ferromagnetic-like alignment that produces a net chiroptical response.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Terahertz Circular Dichroism Spectroscopy of Molecular Assemblies and Nanostructures

Chemical, physical, biological and materials engineering disciplines use a variety of chiroptical spectroscopies to probe geometrical and optical asymmetry in molecules and particles. Electronic (ECD) and vibrational (VCD) circular dichroism are the most common of these techniques and collectively enable the studies of electronic and vibronic transitions with energies between 0.1 and 5.0 eV. The vibrational states with characteristic energies in the range of 0.001–0.01 eV carry valuable information about concerted intermolecular motions in molecules and crystals involving multiple atoms. These vibronic transitions located in the terahertz (THz) part of the spectrum become increasingly more important for the chemistry, physics, and biology of complex molecules and materials However, the methodology and hardware of THz circular dichroism (TCD) are much less developed than the chiroptical spectroscopies for ultraviolet, visible, near- and mid infrared photons. In this report we provide theoretical foundations, practical implementations, comparative assessments, and exemplary applications of TCD spectroscopy. We show that the sign, intensity, and position of TCD peaks are highly sensitive to the three-dimensional structure and long-range organization of molecular crystals, which offer unique capabilities to study (bio) molecules, their crystals, and nanoscale assemblies and apply the novel data processing methodologies. TCD also offers a convenient toolbox to identify new physical phenomena, such as chiral phonons and their propagation in nanostructured matter. We also discuss the major challenges, emerging opportunities and promising research directions, including broad investigation of chiral phonons observed in chiral (nano) crystals and emerging machine learning methodologies for TCD in biological and nanoscale structures. Ubiquity of low-frequency vibrations with rotational components in biomolecular structures, combined with sharpness of peaks in TCD spectra, enables a variety of technological translations.

36 MATERIALS SCIENCE↗