Benzo[4,5]imidazole[2,1-b]quinazoline-1(2H)-one: An efficient fluorescent probe for the selective and sensitive...

Copper (Cu) is essential for biological systems and animal-plant tissues, but Cu²⁺ ions are also significant environmental pollutants. An imbalance in non-toxic Cu²⁺ levels can lead to health issues. This study focuses on the development of a novel fluorescent turn-on probe, 3,4-dihydrobenzo[4,5]imidazole[2,1-b]quinazoline-1(2H)-one (HBQ) for the selective and sensitive detection of Cu²⁺ ions. The synthesis of HBQ was achieved from the reaction of 2-((dimethylamino)methylene)-cyclohexane-1,3-dione and 2-aminobenzimidazole. The photophysical properties of HBQ were investigated in various solvents. The strong binding of HBQ to Cu²⁺ causes a blue shift in the emission maxima and enhanced fluorescence due to reduced non-radiative decay, highlighting its selectivity for Cu²⁺ detection. Absorption and emission spectroscopy revealed the binding interactions, sensitivity, and selectivity of HBQ toward Cu²⁺ ions. The turn-on fluorescence of HBQ shows high sensitivity, with detection (LOD) and quantification (LOQ) limits extending to sub-micron concentrations. The sensor's reliability and applicability were further validated using real samples, with a recovery rate of approximately 100 ± 2 %.