A simple and efficient synthesis of phenanthridine molecule has been successfully achieved. This is involved in the development of fluorescent chemosensor for the trace level determination of Al3+ and Cr3+ through a turn-on response. The recognizing pathway towards Al3+ and Cr3+ was investigated by UV visible spectrometry, Fluorescence spectrometry, NMR spectrometry and HR-MS. The calculated LOD vaues are 2.5 × 10−7 and 1.1 × 10−5 for Al3+ and Cr3+ respectively. Finally application of probe in identification of E. coli bacteria was employed based on biocompatibility in fluorescence imaging. © 2020 Elsevier B.V.