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Polarimetry
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
Spectroscopic polarimetry, combining the rich information from both spectroscopy and polarimetry, is one of the most exhaustive methods for analyzing light properties and light–matter interaction. It is applied to a wide range of scientific disciplines. In searching for life in the universe, we need a sensitive remote sensor capable of identifying a universal biosignature. Since all known living materials contain chiral molecules (a molecule that does not superimpose with its mirror image) possessing almost exclusively a single handedness in their biological processes, homochirality is likely to be a universal biosignature for all biochemical life whether similar to terrestrial or not. A PEM-based spectroscopic Stokes polarimeter is well suited to both remote sensing and detecting weak circular polarization signals that may arise from homochirality of astrobiological samples.
Recent progress at the interface between nanomaterial chirality and liquid crystals
Published in Liquid Crystals Reviews, 2021
Diana P. N. Gonçalves, Marianne E. Prévôt, Şenay Üstünel, Timothy Ogolla, Ahlam Nemati, Sasan Shadpour, Torsten Hegmann
Understanding and controlling the chirality of molecules, nanoparticles and -clusters as well as surfaces is a central theme in various fields of science, from fundamental research on elucidating the origin of homochirality [30, 31] to understanding how chirality transfers across distances and length scales [18]. Homochirality, i.e. the single handedness of key biological molecules, is ubiquitous in nature and a key signature of life. Living organisms use virtually exclusively L-amino-acids and D-sugars as building blocks for proteins and nucleic acids. Researchers have invested a great deal of effort to elucidate the origin of homochirality, and chirality amplification, or more accurately, amplified enantioselectivity, emerged as one of several critical underlying concepts [32].
Chiroptical studies on nanoparticle-liquid crystal composites
Published in Liquid Crystals, 2023
The scientific community is investing a great deal of effort to elucidate the origin of homochirality and amplification of chirality emerged as a critical underlying concept. New molecular structures and materials have been generated to fully exploit their chiroptical characteristic. Here, we reviewed recent progress and ongoing limitations in chiroptical NP-LC materials. We have provided a clear comparison of chiroptical NP-LC composites attained by three different strategies: doping, template and direct bounding approaches. In general, doping chiral NPs in bulk LC is a facile method to detect, visualise, measure and quantify the chirality of chiral molecules based on optical observation. And it requires strict manipulations to gain well-mixed system because NPs prefer to aggregate together and separate from soft matrix. Template method is used to direct the helical assembly of NPs and it shows great potential to synthesise chiroptical metamaterials by choosing suitable chiral templates. But the helical NPs achieved by this approach are static and irreversible. Macroscopic liquid crystal behaviour has been observed for the undiluted gold nanoparticles organic-modified by designed chiral discogen and such chiral LC/NP hybrid nanomaterials are highly expected to realise the tunable optical activities base on various ordered structure in different phases. Unfortunately, few works achieve this goal. Because in most cases, the fluidity and poor compatibility between organic LC groups and stubborn metals cannot afford forming a superstructure at microscale and macroscale. To achieve enhanced or new chiroptical functions, increasing the anisotropy factor of chiral matter has been proposed and it proved to be critical to SP-CD resonance.