Sensitive and fast optical HCl gas sensor using a nanoporous fiber membrane consisting of poly(lactic acid) doped with tetraphenylporphyrin

Abstract

A highly sensitive and fast sensor for gaseous hydrogen chloride (HCl) is described. It is based on the use of the optical probe 5,10,15,20-tetraphenylporphyrin contained in a poly(lactic acid) nanoporous fiber membrane that was fabricated via electrospinning. With its porous structure, the sensor overcomes the slow gas absorption and diffusion of other sensing materials. Field emission SEM was employed to characterize the morphology of the sensing membrane. The exposure to HCl gas causes a color change from pink to green that is due to the protonation of the central nitrogen atoms of the porphyrin, and fluorescence is quenched. The largest increase in absorbance occurs at 442 nm. HCl gas can be detected in this way even at sub-ppm levels. The detection limit is 34 ppb, and the response time is as short as 5 s. The sensor is highly stable after ten cycles of tracing HCl gas and recovery, and response is fully reversible.