Aggregation-induced Emission Active Naphthalimide Derived Schiff Base for Detecting Cu and Its Applications.

Herein, an aggregation-induced emission (AIE) active Schiff base (NHS) was synthesized by condensing naphthalimide hydrazide with salicylaldehyde. The non-fluorescent solution of NHS in DMSO turned to emissive NHS upon increasing the HEPES fraction in DMSO from 70 to 95%. The UV-Vis absorption and DLS studies supported the self-aggregation of NHS that restricted the intramolecular rotation and activated the ESIPT process. The blue fluorescence of AIE luminogen NHS in DMSO:HEPES (5:95, v/v, pH = 7.4) was examined by adding different metal ions (Al, Ca, Cd, Co, Cu, Cr, Fe, Fe, Hg, Mg, Mn, Ni, Pb and Zn). NHS showed a selective fluorescence switch-off response for Cu due to the chelation enhancement quenching effect (CHEQ). The quenching of NHS by Cu was explored by using density functional theory (DFT) and Stern-Volmer plot. The practical utility of NHS was examined by quantitative and qualitative analysis of Cu in real water samples.