Liquid crystal nose based on chiral photonic bandgap materials: principles of selective response
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Liquid crystal nose based on chiral photonic bandgap materials: principles of selective response P. V. Shibaev1 · O. Roslyak1 · J. Plumitallo1 · E. Gullatt1 · U. Aparajita2 Received: 6 August 2020 / Accepted: 21 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Chiral liquid crystalline (LC) compositions with the selective reflection band (SRB) in a visible spectral range are suggested and studied as elements of LC-nose. This allows for optical detection of several volatile organic compounds (VOCs): SRB shifts and color of the sample changes under the action of VOCs. Ethanol, toluene, pyridine and acetic acid were detected by means of colorimetric and spectroscopic techniques during their diffusion inside chiral elements of LC-nose. Selectivity to different VOCs is enhanced by means of components of liquid crystal matrix with different viscosity, affinities to the solvents, and abilities to form hydrogen bonding. Keywords Cholesteric liquid crystals · Gases · Volatile organic compounds · Chirality · Detection · Liquid crystal nose There is a continuous need for creating materials and devices (artificial noses) that can respond to different kinds of pollutants including volatile organic compounds (VOCs) [1]. A VOC is one of a group of carbon-containing compounds that evaporates readily at room temperature with adverse health effects. The VOCs of environmental concern are often organic solvents (for example, toluene, ethanol, pyridine, and acetic acid). Commercially available VOC sensors with a wide range of sensitivities are deployed for detection of VOCs in outdoor and indoor environment [2]. Most of the current compact and inexpensive gas and VOC sensors are based on metal oxides that can change their resistance in different gases [3]. There are different types of sensors, some work at low concentrations, others may work at relatively high concentrations from hundreds to thousands ppm [2, 4]. Most of these sensors and their assemblies in electronic noses [5, 6] designed to selectively distinguish volatile Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00339-020-04102-3) contains supplementary material, which is available to authorized users. * P. V. Shibaev [email protected] 1
Physics and Engineering Physics Department, Fordham University, Bronx, New York, NY 10458, USA
Science Department, Borough of Manhattan Community College, CUNY New York, New York, NY 10007, USA
2
compounds (especially aromatic compounds) require electric power to operate. Organic solvents producing VOCs are used in industrial environment, and there are certain limits on the daily exposure of workers to harmful concentrations of these VOCs [7]. The requirements, established by governmental agencies, are different for different solvents and vary by countries. They typical require a detection range between tens to thousands ppm. However, there is also a need for sensors working in harsh environments at higher concentrations of VOCs. For example, in
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