Deprotonated Nanofilms-Enabled Fluorescence-Colorimetric Dual-Mode Sensing of 3-Hydroxy-2-butanone.

3-Hydroxy-2-butanone (3H2B) is a key gaseous metabolite of Listeria monocytogenes, a potential lung cancer biomarker, and a widely used food flavoring agent, underscoring the demand for real-time monitoring solutions. In this study, we designed a salicylaldehyde-functionalized 1,8-naphthalimide derivative (NI-OH-CHO) and reacted it with 1,3,5-tri(4-aminophenyl)benzene (TAPB) at a liquid/liquid interface to synthesize fluorescent NI-TAPB nanofilms. Upon deprotonation, the nanofilms (NI-TAPB@F) exhibit a reversible and unprecedented fluorescence response to 3H2B. Leveraging this discovery, we developed a fluorescent 3H2B sensor with exceptional performance: ultrahigh sensitivity (detection limit: ∼ 1.8 ppb), rapid response (<8 s), outstanding selectivity, and remarkable stability at room temperature. These advantages stem from the rational design of binding sites and the porous structure of the nanofilms. Furthermore, visual 3H2B detection was achieved using the deprotonated films. Notably, the nanofilms are self-standing, self-adhesive, and flexible, enabling substrate-independent detection by eliminating interference from background color or emission. These properties also facilitate on-site qualitative and quantitative analysis. We anticipate this work will pave the way for the development of portable 3H2B detection devices.