Fabrication of Langmuir–Blodgett thin film for organic vapor detection using a novel N,N′-dicyclohexyl-3,4:9,10-perylenebis (dicarboximide)

Abstract

The Langmuir–Blodgett (LB) thin film fabrication and gas sensing properties of a novel N,N′-dicyclohexyl-3,4:9,10-perylenebis (dicarboximide) (FY2) is reported in this study. Surface pressure changes as a function of surface area of FY2 molecule at the water surface shows a well organized and stable monolayer with a 22.5mNm−1 surface pressure value for LB film deposition. LB deposition processes is characterized by UV–vis spectroscopy and quartz crystal microbalance (QCM) measurement system. Transfer ratio values are found to be 0.93 for glass and 0.95 for quartz crystal substrate. Gas sensing properties of these LB films against volatile organic compounds (VOCs) such as chloroform, benzene, toluene and ethyl alcohol are studied using the QCM technique. The FY2 LB film sensor sensitivities are calculated for chloroform, benzene, toluene and ethyl alcohol, 5.32×10−4, 3.52×10−4, 1.32×10−4 and 1.16×10−4Hzppm−1, respectively. LB films are more sensitive to chloroform than other vapors and the response of the LB films to chloroform is fast, large and reversible. Associated limits of detection are found to be between 1.12×104 and 5.17×104ppm for these organic vapors. The novel FY2 material is promising as a vapor sensing device at room temperature.