Alkali‐treated semiconducting polypyrrole for infrared detection

A simple treatment of a polypyrrole (PPy) film with sodium hydroxide (NaOH) solutions reduces the conductivity (i.e., increased the resistance) and makes the film heat sensitive in the infrared (IR) spectrum with wavelength from 2.5 to 15.4 μm. The IR sensitivity increases with increasing treatment time in NaOH solutions and increasing exposed area to the radiation. The temperature coefficient of resistance, α, quantifying the sensitivity to IR, of the NaOH‐treated PPy is comparable with that of silicon and other conventional materials. The reduction and recovery of resistance due to IR on/off exposure exhibit a t^β dependence, where t is the time and β is determined to be around 0.5. This implies that the response of the material is controlled by diffusion of heat flux into and out of the sample. It is also observed that thermal ageing of the NaOH‐treated PPy film enhances the IR sensitivity. The sensing response of the treated films is observed beyond the thermal IR region to ultraviolet–visible wavelengths. Thus, the NaOH‐treated PPy appears to be a broadband sensing material. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012