Abstract
Chirality in materials and light is of abiding interest across a broad range of scientific disciplines. This article discusses present and emerging issues in relation to molecular and optical chirality, also including some important developments in chiral metamaterials. Quantifying the chirality of matter or light leads to issues concerning the most appropriate measures, such as a helicity parameter for specific chiral chromophores and technical measures of light chirality. An optical helicity and chirality density depend on a difference between the numbers of left- and right-handed photons in a beam. In connection with circularly polarised luminescence, adoption of the Stokes parameter to spontaneous emission from chiral molecules invites critical attention. Modern spectroscopic techniques are often based on the different response arising from left-handed circularly polarised light compared to right-handed light. This dissimilarity can be exploited as a foundation for the separation of chiral molecules, promising new avenues of application.
Highlights
The properties of chiral molecules have interested scientists for over 150 years, ever since the discovery by Pasteur that there are two forms of tartaric acid [1]
Many bioactive molecules are homochiral, one enantiomer predominating for reasons whose origin remains debatable, and which some claim as the basis for life [2,3,4,5]
Similar principles apply to materials that are structured on a mesoscopic scale, where a relatively new field of endeavour has arisen in the construction of metamaterials that can exhibit chirality through larger, nano- or micro-scale architectures [6]
Summary
The properties of chiral molecules have interested scientists for over 150 years, ever since the discovery by Pasteur that there are two forms of tartaric acid [1]. Since the receptors in human biology mostly consist of chiral molecules, drug action mostly involves a specified enantiomeric form This has spurred the development, especially in the pharmaceutical industry, of a host of techniques to secure enantiopure products. A significant drawback, for either approach, is a dependence on a supply of enantiopure reagents or substrates – synthesis routes generally utilise chiral building blocks or enantioselective catalysts [7,8], while enantiomer separation techniques typically incorporate chiral selector molecules to form chemically distinct and distinguishable diastereomeric complexes [8,9]. D.S. Bradshaw et al / Chemical Physics Letters xxx (2015) xxx–xxx emission, and we go on to discuss the new optical methods of enantiomer separation, before a final summary
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