Two highly sensitive Schiff-base fluorescent indicators for the detection of Zn2+

Abstract

Two novel Schiff-based fluorescent probes 1 and 2 for Zn²⁺ ion were developed. The spectroscopic behavior toward metal ions has been investigated by the absorption and fluorescence method. Both of the two probes were found to show good selectivity to Zn²⁺ ion over other metal ions in ethanol–water solution, such as Li⁺, Na⁺, Mg²⁺, Al³⁺, K⁺, Ca²⁺, Ba²⁺, Cr³⁺, Mn²⁺, Cu²⁺, Co²⁺, Ni²⁺, Fe³⁺, Hg²⁺, Ag⁺, Cd²⁺ and Pb²⁺. The selectivity mechanism of 1 and 2 to metal ions is based on a combinational effect of proton transfer (ESPT), CN isomerization and chelation-enhanced fluorescence (CHEF). pH response experiments show that the probes can be used to indicate pH values under certain conditions.