A New Fluorescent Chemosensor for Cobalt(II) Ions in Living Cells Based on 1,8-Naphthalimide.

In this work, a highly selective fluorescent chemosensor -(2-(2--1,3-dioxo-2,3-dihydro-1-benzo[]isoquinolin-6-yl)hydrazine-1-carbonothioyl)benzamide () was prepared and characterized. An assay to detect the presence of cobalt(II) ions was developed by utilizing turn-on fluorescence enhancement with visual colorimetric response. Upon treatment with Co, a remarkable fluorescence enhancement located at 450 nm was visible to naked eyes accompanied with a distinct color change (from pink to colorless) in a CHCN/HEPES (4/1, /, pH = 7.4) solution due to the formation of a 1:1 complex at room temperature. In addition, the linear concentration range for Co was 0-25 µM with the limit of detection down to 0.26 µM. Thus, a highly sensitive fluorescent method based on chelation-assisted fluorescence enhancement was developed for the trace-level detection of Co. The sensor was found to be highly selective toward Co ions with a large number of coexisting ions. Furthermore, the probe can serve as a fluorescent sensor for Co detecting in biological environments, demonstrating its low toxic properties to organisms and good cell permeability in live cell imaging.