A turn-on fluorescent sensor for zinc and cadmium ions based on perylene tetracarboxylic diimide

In this paper, we describe a turn-on fluorescent probe for Zn2+ and Cd2+ ion detection and discrimination. This probe, N′-bis-(N,N-di-(2-pyridylmethyl)-ethane-1,2-diamine)-perylene-3,4,9,10-tetracarboxylic-diimide (PDI-DIDPA), exhibits very low fluorescence at pH above 6.0 due to the photo-induced electron transfer (PET) process from 2-pyridylmethyl-amine (DPA) to perylene tetracarboxylic diimide (PDI). Zn2+ and Cd2+ can chelate PDI-DIDPA to form a stable complex at pH 6.0–7.0 and 9.0 respectively, and inhibit the PET process, which result in the fluorescence recovery of PDI-DIDPA. This fluorescence turn-on behavior allows the detection of Zn2+ in the range of 0.1–4.0 μM and Cd2+ in the range of 0.1–5.0 μM. The limit of detection for Zn2+ and Cd2+ is as low as 32 nM and 48 nM. The high selectivity, high sensitivity and easy operation make this probe suitable for the rapid detection of Zn2+ and Cd2+ respectively. The different response of PDI-DIDPA to Zn2+ and Cd2+ at different pH makes it possible to discriminate Zn2+ and Cd2+ by simply adjusting the pH of the working solution.