Rapid detection and estimation of Lead (Pb2+) has been accomplished in randomly selected lipstick samples by a simple FRET-based chemosensor RNPC (Rhodamine-Naphthalimide Conjugate) through “turn on” fluorescence. Fluorescence intensities were compared with the fluorescence plot of RNPC-Pb2+ complex to evaluate the concentration of Pb2+ present in the sample solutions. NMR titrations and TD-DFT calculations were achieved in order to demonstrate the sensing mechanism and the electronic properties of the RNPC-Pb2+ complex. Different cell lines have been cultured for live cell imaging study to understand the in vitro sensing mechanism and to satisfy the biocompatibility of the probe RNPC. © 2018 Elsevier B.V.