A novel barbiturate-based fluorescent probe for selective detection of Cu²⁺ in aqueous media and live-cell imaging

Copper ions (Cu²⁺) play vital roles in numerous physiological processes; however, their dysregulation can lead to severe health disorders, highlighting the need for reliable and sensitive detection strategies. Herein, we report the rational design and synthesis of a novel barbiturate-naphthyl-picolinate conjugate (BN-P) as a fluorescent probe for the selective detection of Cu²⁺ in an aqueous media. The probe exhibits negligible fluorescence in its native state, whereas Cu²⁺-triggered hydrolysis restores the intramolecular charge transfer (ICT) process, resulting in a pronounced fluorescence "turn-on" emission at 468 nm accompanied by a visible color change from colorless to blue-green under 365 nm UV illumination. BN-P demonstrates excellent water solubility, high selectivity toward Cu²⁺, and a rapid response (< 5 min). A good linear correlation was observed in the range of 0-4.25 μM, affording a detection limit of 23.6 nM. The sensing mechanism was further verified by ¹H NMR, HRMS, and DFT analyses. Moreover, BN-P was successfully employed for fluorescence imaging of intracellular Cu²⁺ in living 4 T1 cells, indicating its potential utility for biological sensing and bioimaging applications.