A methane sensor based on poly[3 ',4 '-dihexyl-4,4 ''-bis(pentyloxy)-2,2 ': 5 ',2 ''-terthiophene]

3,4'-Dihexyl- 4,4"-bis(pentyloxy)-2,2':5',2"-terthiophene was electrochemically polymerized on gold interdigitated electrodes to investigate the impedance variation of the polymer in the exposure to air/methane atmospheres. The higher sensitivity of poly[3',4'-dihexyl-4,4" -bis( pentyloxy) 2,2';5',2"-terthiophene] (PHPT) to methane was observed at frequencies of about 100 Hz. The PHPT impedance decreases when the CH4 concentration increases and shows the highest sensitivity at the lowest methane concentrations. After each concentration step, the impedance decreased as the square root of time indicating that the response time of the PHPT-based sensor was controlled by diffusion of the gas into the material. It is suggested that the absorption of methane into the polymer film affects the rate of interchain charge hopping.