A novel pyrazoline-based fluorescence probe armed by pyrene and naphthol system for the selective detection of Cu 2+ and its biological application

A photo-induced electron transfer cationic fluorescence probe L 1 based on pyrene-naphthol system was designed to detect the change of Cu 2+ with fluorescence. The probe L 1 was found to selectively recognize Cu 2+ in aqueous ethanol solution [10.0 mmol/L HEPES, pH 7.4, EtOH–H 2 O = 1:1 (v/v)] without interference from other coexisting metal ions. The response of the sensor to Cu 2+ is transient and reversible, and anions generally have no impact on the selectivity of Cu 2+ . Probe L 1 forms complex with Cu 2+ in 1:1 ratio as supported by Job’s plot analysis. The binding constants of Cu 2+ was calculated to be 6.322 × 10 4 L/mol using a nonlinear curve-fitting method. The detection limit of Cu 2+ was determined to be 1.620 × 10 –7 mol/L. The energy gap between HOMO and LUMO in L 1 and L 1 –Cu 2+ was calculated by density functional theory as 3.76 eV and 2.71 eV, respectively. In addition, the probe L 1 has extremely low cytotoxicity and can be used for living cell imaging studies.