A phenanthro [9,10-d] imidazole-based optical sensor for dual-responsive turn-on detection of acidic pH and Cu2+ in chicken blood and living cells

A phenanthro[9,10-d]imidazole-based organic optical sensor (PIQPy) for dual-responsive turn-on detection of both acidic pH and Cu2+ in semi-aqueous media was described. PIQPy was weak fluorescence (nearly turn-off) in pure ethanol solution but exhibited typical aggregation-induced emission phenomenon (moderate turn-on) in water/EtOH mixture. More interestingly, PIQPy further displayed a dual enhancement (strong turn-on) for both acidic pH and Cu2+ with highly fluorescent intensity. pK(a) value of PIQPy for pH responding was 6.89, which suggests that PIQPy was an ideal biosensor for pH sensing. In addition, the super lower limit of detection for Cu2+ were found to be 37.69 nM which also nearly 500-fold lower than Cu2+ concentration in blood (15.7-23.6 mu M). Therefore, PIQPy was successfully used to detect Cu2+ in chicken blood. Furthermore, these dual-responsive turn-on signals to both acidic pH and Cu2+ were also successfully implemented in HeLa cells, which proved that PIQPy was capable of imaging pH fluctuations and simultaneous Cu2+ in living cells.