Development an optical sensor using lyotropic cholesteric liquid crystals for the detection of toxic gases

In the current study, a lyotropic cholesteric liquid crystal (ChLC) based sensor for the identification of vapors of polar (toluene and phenol) and apolar (1,2 dicholoropropane) toxic gases was investigated. The lyotropic ChLC sample including cholesteryl oleyl carbonate, cholesteryl pelargonate, and cholesteryl benzoate was supported on the chemically modified glass surfaces as an optical sensor for the detecting of these toxic gases vapors. The glass surfaces were modified by coating Dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP). The optical signal generated by the incorporation of different toxic gases vapors in the lyotropic ChLC layers which disturbs the pitch length. These toxic gases were evaporated at different temperatures and the exposure time was differentiated. Increasing solvent evaporation temperature lead a shift in the wavelength maximum to smaller wavelengths which can be observed by a naked eye.