solvent vapour detection with cholesteric liquid crystals—optical and mass-sensitive evaluation of the sensor mechanism溶剂蒸汽检测和胆甾型液体crystals-optical mass-sensitive评估传感器机制.pdf

Sensors 2010, 10, 4887-4897; doi:10.3390/s100504887 OPEN ACCESS sensors ISSN 1424-8220 /journal/sensors Article Solvent Vapour Detection with Cholesteric Liquid Crystals—Optical and Mass-Sensitive Evaluation of the Sensor Mechanism † Adnan Mujahid, Helen Stathopulos, Peter A. Lieberzeit and Franz L. Dickert * Department of Analytical Chemistry, University of Vienna, Waehringer Strasse 38, A-1090 Vienna, Austria; E-Mails: adnan.mujahid@univie.ac.at (A.M.); helen.stathopulos@univie.ac.at (H.S.); peter.lieberzeit@univie.ac.at (P.A.L.) † Dedicated to Professor Rolf Saalfrank on the occasion of his 70th birthday. * Author to whom correspondence should be addressed; E-Mail: franz.dickert@univie.ac.at; Tel.: +43-1-4277-52317; Fax: +43-1-4277-9523. Received: 18 March 2010; in revised form: 4 May 2010 / Accepted: 6 May 2010 / Published: 12 May 2010 Abstract: Cholesteric liquid crystals (CLCs) are used as sensitive coatings for the detection of organic solvent vapours for both polar and non-polar substances. The incorporation of different analyte vapours in the CLC layers disturbs the pitch length which changes the optical properties, i.e., shifting the absorption band. The engulfing of CLCs around non-polar solvent vapours such as tetrahedrofuran (THF), chloroform and tetrachloroethylene is favoured in comparison to polar ones, i.e., methanol and ethanol. Increasing solvent vapour concentrations shift the absorbance maxi