Enhanced sensitivity of langasite-based surface acoustic wave CO gas sensor using highly porous Ppy@PEDOT:PSS hybrid nanocomposite

Abstract

The potential usage of the nano-porous Ppy@PEDOT:PSS hybrid organic nanocomposite polymers has been widely explored in various applications fields. However, the study of Ppy@PEDOT:PSS based room temperature (RT) CO gas sensing utilizing surface acoustic wave (SAW) sensor is still at infancy. Herein, we report a langasite (LGS) based RT CO SAW gas sensor using Ppy@PEDOT:PSS hybrid organic nanocomposite polymer. The Ppy@PEDOT:PSS/LGS SAW sensor exhibited high sensitivity of ~9.38 KHz positive frequency shift (∆f) as compared to the pristine PEDOT:PSS/LGS SAW (~1.76 kHz negative ∆f) sensor with a short response/recovery times (121 s/138 s), good reproducibility, excellent selectivity and low detection limit (~231 ppb) towards CO (100 ppm) gas at RT. Interestingly, our experimental findings demonstrated that the Ppy@PEDOT:PSS/LGS SAW sensor exhibited the positive ∆f which was attributed to the enhanced elastic loading and decrease in the electrical conductivity under CO gas ambient, whereas the PEDOT:PSS/LGS SAW showed negative ∆f, which was due to the mass loading effect. Moreover, the impressive CO gas sensing performances were attributed to the, high porosity, large surface area, abundant OH and amine functionalizing groups. In addition the synergetic effect of the p-p hybrid heterojunction, which can act as active surface sites that further improving the CO gas molecules absorption, and thus leading to the massive changes in elastic stiffness and the electrical conductivity of the Ppy@PEDOT:PSS film. The scientific findings of this work offers a versatile platform to develop high performance hybrid organic polymer nanocomposites based SAW gas-sensing applications.