A probe based on coumarin phenylhydrazone highly selective to NO₂ for the detection of NEPE propellant aging

As a crucial product in the aging process of nitrate ester plasticized polyether (NEPE) propellant, the development of a non-destructive, rapid, and sensitive detection method for nitrogen dioxide (NO₂) is particularly important. A coumarin-phenylhydrazone molecule with high selectivity and sensitivity to NO₂ was synthesized. By employing a hydrazone group as the recognition site that specifically reacts with NO₂, the ratiometric fluorescence responses in both solution and film were realized. Upon NO₂ exposure, the absorption and fluorescence emission bands of the probe possess a significant hypsochromic shift. In addition to achieving a linear response to NO₂ under solution conditions, the probe can also achieve a linear response to NO₂ under film conditions that are convenient for practical applications. Furthermore, the probe has excellent selectivity and thermal stability, and the limit of detection (LOD) is as low as 1.5 ppm, which broadens the boundaries of practical applications. In this study, the coumarin probe was firstly extended to the field of solid propellant aging monitoring, which has the potential of being applied for the non-destructive monitoring of NEPE propellant aging.