A simple 1,8-naphthalimide based Schiff base probe (E)-6-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2-(2-morpholinoethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NDSM) has been designed and synthesized for the specific detection of Fe3+based on a fluorimetric mode. The absorbance ofNDSMat 360 nm increased significantly in acetonitrile:water (7:3, v/v) medium only in the presence of Fe3+ions with a visible colour change from yellow to golden yellow. Likewise, fluorescence emission intensity at 531 nm was almost wholly quenched in the presence of Fe3+. However, other competitive ions influenced insignificantly or did not affect the optical properties ofNDSM. Lysosome targetability was expected fromNDSMdue to the installation of a basic morpholine unit. The LOD was found to be 0.8 μM with a response time of seconds. The fluorescence reversibility ofNDSM + Fe3+was established with complexing agent EDTA. Fe3+influences the optical properties ofNDSMby complexing with it, which blocks CN isomerization in addition to the ICT mechanism. The real-time application of Fe3+was demonstrated in test paper-based detection, by the construction of a molecular logic gate, quantification of Fe3+in water samples and fluorescence imaging of Fe3+ © The Royal Society of Chemistry 2021.