Cholesteric Liquid Crystals For Detection Of Organic Vapours

dc.creatorWinterbottom D.A.
dc.creatorNarayanaswamy R.
dc.creatorRaimundo Jr. I.M.
dc.date2003
dc.date2015-06-30T17:29:49Z
dc.date2015-11-26T15:42:11Z
dc.date2015-06-30T17:29:49Z
dc.date2015-11-26T15:42:11Z
dc.date.accessioned2018-03-28T22:50:46Z
dc.date.available2018-03-28T22:50:46Z
dc.identifier
dc.identifierSensors And Actuators, B: Chemical. , v. 90, n. 01/03/15, p. 52 - 57, 2003.
dc.identifier9254005
dc.identifier10.1016/S0925-4005(03)00021-2
dc.identifierhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0037457426&partnerID=40&md5=5c9dee64ab3ded9b7b995e1c0baecd0e
dc.identifierhttp://www.repositorio.unicamp.br/handle/REPOSIP/102299
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/102299
dc.identifier2-s2.0-0037457426
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1264798
dc.descriptionStudies on the use of cholesteric liquid crystals (CLCs) as sensing phase for detection of organic vapours in air are described. Stock solutions of 1.0% (w/v) cholesteryl nonanoate (CN) and cholesteryl chloride (CC) were prepared in tetrahydrofuran. Binary mixtures, with compositions ranging from 0.18 to 0.25% of CC and 0.82-0.75% of CN, respectively, were prepared by appropriate mixing of the stock solutions. Films were cast by pipetting three 10μl aliquots of the CLC solution mixture onto a glass disk, whose reverse side was made black to absorb unscattered light. The glass disk was adapted to the common end of a bifurcated optical fibre bundle and placed in a glass vial, which provided a headspace of organic vapours. Measurements were carried out at 27 ± 1 °C, a temperature in which the CLC mixtures maintain their liquid crystalline properties. The responses of the CLC mixtures to vapours of ethanol, acetone, benzene, pyridine and hexane were investigated. The colour of the sensing phases depended on their compositions and exposure to organic vapours gives rise to a change in the optical characteristics of liquid crystals. It was found that the CLC layers containing 0.23-0.25% of CC had no significant change in optical properties when exposed to organic vapours and that ethanol did not cause any optical changes in the liquid crystal layers. Benzene as well as hexane always turned all the coloured liquid crystalline layers to colourless. The CLC layers exhibited different behaviours to vapours of acetone and pyridine. For example, the wavelengths of maximum scattering for the 0.19% CC layer were 530nm in air, 545 nm in pyridine and 580 nm in acetone. The CLC layers showed reversibility. The lifetimes of these layers (interval of time in which the liquid crystalline phase exists, before crystallisation) were investigated by employing acetone and n-hexane vapours. Average lifetimes of 14-15 min were found for films in contact with these vapours, while a lifetime of 205 min was possible when the CLC film was exposed to air. © 2003 Elsevier Science B.V. All rights reserved.
dc.description90
dc.description01/03/15
dc.description52
dc.description57
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dc.languageen
dc.publisher
dc.relationSensors and Actuators, B: Chemical
dc.rightsfechado
dc.sourceScopus
dc.titleCholesteric Liquid Crystals For Detection Of Organic Vapours
dc.typeActas de congresos


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