Highly sensitive electrospun ammonia sensor using polydiacetylene incorporating hemi-protonated cytosine

Abstract

Polydiacetylenes (PDAs) have attracted significant attention as promising materials for sensor development due to their unique colorimetric and fluorescent responses to external stimuli. In this study, we propose a PDA-based sensor structure capable of selectively detecting ammonia, developed from a diacetylene monomer functionalized with a cytosine moiety (CyDA). By inducing hemi-protonation, we established a CyDA-H platform that enables colorimetric ammonia sensing. Furthermore, instead of conventional film-casting or drop-casting methods, we employed an electrospinning technique to overcome the limitation of low sensitivity. CyPDA-H was immobilized within a three-dimensional porous polyethylene oxide (PEO) nanofibrous matrix via electrospinning, enhancing reactivity with ammonia molecules. The resulting sensor exhibited a low detection limit of 17 ppm and demonstrated excellent selectivity for ammonia over various amines and basic compounds. Additionally, real-time monitoring of raw chicken spoilage at 4 °C and 25 ℃ revealed a gradual color change from blue to red due to the accumulation of ammonia released during decomposition, which was clearly visible to the naked eye. This study successfully demonstrates the fabrication of a highly sensitive electrospun-type CyPDA-H sensor and highlights its strong potential for commercial application as a simple and easy-to-use food freshness indicator.