Polymer-embedded thin films of a pyrene chalcone-based small molecule for vapour-phase detection of picric acid.

Abstract

The incorporation of fluorescent small organic molecules (fluorophores) into polymer matrices provides an effective strategy for fabricating thin films capable of rapid and sensitive vapour-phase detection of nitroaromatic compounds (NACs). In this study, a pyrene-chalcone derivative, 2APP, synthesized from 1-pyrenealdehyde and 2-acetylpyridine, demonstrated selective sensing toward picric acid (PA) in solution. Subsequently, 2APP-embedded thin films were fabricated using polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF) matrices. The PEO-based films exhibited a blue-shifted emission maximum, whereas the PVDF-based films showed a red shift relative to pristine 2APP, attributed to the distinct hydrophilic and hydrophobic interactions of PEO and PVDF, respectively. Density functional theory (DFT)-optimized geometries revealed interactions between the pyridyl nitrogen and ethylene bridge of 2APP with the oxygen atoms of PEO. In contrast, the PVDF system displayed C-H⋯F interactions between the hydrogen atoms of the pyrene moiety of 2APP and the fluorine atoms of PVDF. These intermolecular interactions were further supported by X-ray photoelectron spectroscopy (XPS) analysis. The resulting fluorescent polymer thin films (PEO/PVDF-x% 2APP) exhibited excellent chemosensing performance toward PA vapour, achieving the estimated exposure-dose detection limits (D LOD) of 1.377 ppm min for PEO-10% 2APP and 0.0638 ppm min for PVDF-50% 2APP at 50 °C. Additionally, the PVDF-based films demonstrated good reusability, as they could be readily regenerated by washing with water and reused for subsequent sensing cycles.

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