A turn-on hydrazide oxidative decomposition-based fluorescence probe for highly selective detection of Cu²⁺ in tap...

Copper (II) is one of the most important metal ions for the human body that act as a catalytic cofactor for many metalloenzymes and proteins, and its homeostasis disruption could lead to many neurological diseases. The reported probes for Cu (II) determination are mostly based on fluorescence quenching mechanism, which provides low precision and reliability. In the present work, a turn-on fluorescence probe, (Z)-1-[2-oxo-2-[2-[1-oxoaceanthrylen-2 (1H)-ylidene]hydrazinyl]ethyl]-pyridinium (OAHP), for highly selective detection of Cu²⁺ was developed. Hydrazide moiety of OAHP quenches probe fluorescence; however, upon its reaction with Cu, oxidative cleavage of the hydrazide moiety and intramolecular cyclization occurs, forming oxadiazole derivative with strong fluorescent properties. In this context, OAHP displayed significant fluorescence enhancement with increasing levels of Cu²⁺. OAHP could detect Cu²⁺ selectively with a detection limit of 18 nM (1.1 ppb). This is the first report for a probe that uses the ability of Cu²⁺ to induce oxidative decomposition of hydrazide with intramolecular cyclization, and it showed exceptional selective performance and exquisite sensitivity. Next, the method was applied successfully for monitoring Cu²⁺ in tap water samples with good accuracy (found% of 95.8-101.5%) and precisions (RSD<10%). Finally, OAHP was successfully applied for imaging Cu²⁺ in living cells, and this result indicates the potential of OAHP for selective detection of Cu²⁺ in complicated matrices.