A novel and fast responsive turn-on fluorescent probe for the highly selective detection of Cd(2+) based on photo-induced electron transfer

A novel, highly sensitive and fast responsive turn-on fluorescence probe, 2,2′-((1E,1′E)-((1,10-phenanthroline-2,9-diyl)bis(methanylylidene)) bis(azanylylidene)) diphenol (ADMPA), for Cd(2+) was successfully developed based on 2,9-dimethyl-1,10-phenanthroline and o-aminophenol. ADMPA showed a remarkable fluorescence enhancement toward Cd(2+) against other competing cations, owing to the suppression of the photo-induced electron transfer (PET) and CH[double bond, length as m-dash]N isomerization. A good linear relationship (R(2) = 0.9960) was obtained between the emission intensity of ADMPA and the concentration of Cd(2+) (0.25–2.5 μM) with a detection limit of 29.3 nM, which was much lower than that reported in literature. The binding stoichiometry between ADMPA and Cd(2+) was 2 : 1 as confirmed by the Job's Plot method, which was further confirmed by a (1)H NMR titration experiment. Moreover, the ADMPA probe was successfully applied to detect Cd(2+) in real water samples with a quick response time of only 6.6 s, which was about 3–40 times faster than the reported cadmium ion probe.