Fluorescence detection of malachite green and cations (Cr3+, Fe3+ and Cu2+) by a europium-based coordination polymer

Due to remarkable fluorescence characteristics, lanthanide coordination polymers (CP) have been widely employed in fluorescence detection, but it is rarely reported that they act as multifunctional luminescent probes dedicated to detecting malachite green (MG) and various metal ions. A europium-based CP fluorescent probe, Eu(PDCA)(2)(H2O)(6) (PDCA = 2,6-pyridinedicarboxylic acid), has been synthesized and exhibited excellent recognition ability for malachite green and metal cations (Cr3+, Fe3+ and Cu2+) among 11 metal cations, 13 anions and six other compounds. The recognition was achieved by fluorescence quenching when MG, Cr3+, Fe3+ and Cu2+ were added to a suspension of Eu(PDCA)(2)(H2O)(6) respectively. Eu(PDCA)(2)(H2O)(6) is a multifunctional luminescent probe, and displayed high quenching efficiencies K-sv (2.10 x 10(6) M-1 for MG; 1.46 x 10(5) M-1 for Cr3+; 7.26 x 10(5) M-1 for Fe3+; 3.64 x 10(5) M-1 for Cu2+), and low detection limits (MG: 0.039 mu M; Cr3+: 0.539 mu M; Fe3+: 0.490 mu M; Cu2+: 0.654 mu M), presenting excellent selectivity and sensitivity, especially for MG. In addition, Eu(PDCA)(2)(H2O)(6) was also made into fluorescent test strips, which can rapidly and effectively examine trace amounts of MG, Cr3+, Fe3+ and Cu2+ in aqueous solutions. This work provides a new perspective for detecting malachite green in fish ponds and heavy metal ions in waste water.