Inkjet-printed thin films on flexible substrate for electro-optical detection of methylamine gas

Methylamine (MA) is highly toxic even at low concentrations. The current U.S.A. Occupational Safety and Health Administration Permissible Exposure Limit (OSHAPEL) is 10 ppm in the gas phase. In this study we have developed low-cost, robust and stable copper sulphide film on flexible plastic and paper substrate. Thesensitivity of the film towards MA as a function of print density is studied at room temperature. The electrical and colorimetric response of the sensing films is optimized with respect to print density. The performance parameters of the sensing films including, sensitivity, a lower limit of detection (LOD), selectivity and onsettime of detection are determined. X-ray photoelectron spectroscopy is employed for chemical characterization of the sensing film. It is demonstrated that copper sulphide films register either change in resistance or colour when exposed to methylamine in a range of 1 to 100 ppm. A LOD of 1 ppm is achieved which is lower thanthe current OSHA PEL. The optimized sensing film has shown over three and six orders of magnitude change in resistance when exposed to 10 ppm and 500 ppm of MA respectively. The low cost, room temperature operation, electrical and colorimetric response of the developed sensing films make them promising candidates to be used for medical diagnostics as well as industrial use for example in chemical industry and environmental applications.