We demonstrate the use of custard apple peel waste biomass (CAPWB) to synthesize the homogenous carbon nano dots (CNDs) for the conductivity-based dopamine sensing and bioimaging applications. In this study, CNDs are synthesized hydrothermally using microwave irradiation and they are found to be biocompatible and hemocompatible. The formation of CNDs was confirmed by UV–Visible spectroscopy analysis. TEM images indicates that they are spherical in shape and size ranging from 3 to 8 nm. XRD and FT-IR studies confirmed the poor crystalline nature and different functional groups of these CNDs, respectively. Fluorescence spectroscopy studies proved their ability to exhibit wavelength dependent photoluminescence (PL) property and showed the PL phenomenon in C2C12 (mouse myoblast), 3T3 (swiss mouse), HeLa (cervical cancer) cells and BL-21 (E. coli strain), suggesting that these CNDs can be used for live cell bioimaging. Cytotoxicity and hemo compatibility assays reveal that these CNDs are not toxic to the cells, providing an opportunity to use them in biomedical applications. Importantly, the CND-Fe complex exhibited dopamine (DA) dependent conductivity-based sensing, thus, providing the novel route for the detection of DA. © 2021 Elsevier B.V.