An AIE active anthracene-based Schiff base probe for "turn-on" detection of Cu²⁺ ions: Demonstrations with nanostructural investigations, DFT, cellular imaging, and real water analysis

An aggregation induced emission (AIE) active anthracene-based Schiff base probe "(2-((anthracen-9-ylmethylene) amino) phenol); AP" was synthesized via one-pot reaction and utilized in "turn-on" detection of Cu2+ ions. Ultraviolet-visible and photoluminescence (UV-vis/PL) interrogations confirm the AIE between 0 and 99 % water fraction (f(w)) and high selectivity of AP to Cu2+. PL studies establish the linear regression of Cu2+ between 0 and 24 mu M with a detection limit (LOD) of 53.2 nM. The Job plot and high-resolution mass (HR-mass) data affirm 2:1 stoichiometry and the association constant (K-a) value appraised as 1.88 x 10(-4) M-2. Time-resolved photoluminescence (TRPL) studies reveal decay kinetics of AIE, Cu2+ sensors and complex's reversibility. Moreover, H-1 NMR titration and density functional theory (DFT) investigations identify the binding mode, pi-pi stacking in AIE, AP - Cu2+ - AP* excimer formation, band gap variations and involvement of photoinduced electron transfer (PET) and chelation enhanced fluorescence (CHEF) mechanism. Crystallinity and nanostructural variations of AIE and Cu2+ sensors are investigated by using powder-X-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and dynamic light scattering (DLS). AIE and Cu2+ sensory method are validated by MDA-MB-231 cellular imaging studies. Finally, real water-based titrations show nanomolar LODs and recoveries > 97 % with RSDs < 3.5 %.