Design and synthesis of a terbium(III) complex-based luminescence probe for time-gated luminescence detection of mercury(II) ions

Time-gated luminescence detection technique using lanthanide complexes as luminescent probes is a useful and highly sensitive method. However, the effective application of this technique is limited by the lack of the target-responsive luminescent lanthanide complexes that can specifically recognize various analytes in aqueous solutions. In this work, a dual-functional ligand that can form a stable complex with Tb ³⁺ and specifically recognize Hg ²⁺ ions in aqueous solutions, N,N,N1,N1-{[2,6- bis(3′-aminomethyl-1′-pyrazolyl)-4-[N,N-bis(3″, 6″-dithiaoctyl)-aminomethyl]- pyridine]} tetrakis(acetic acid) (BBAPTA), has been designed and synthesized. The luminescence of its Tb ³⁺ complex is weak, but can be effectively enhanced upon reaction with Hg ²⁺ ions in aqueous solutions. The luminescence response investigations of BBAPTA-Tb ³⁺ to various metal ions indicate that the complex has a good luminescence sensing selectivity for Hg ²⁺ ions, but not for other metal ions. Thus a highly sensitive time-gated luminescence detection method for Hg ²⁺ ions was developed by using BBAPTA-Tb ³⁺ as a luminescent probe. The dosedependent luminescence enhancement of the probe shows a good linearity with a detection limit of 17 nM for Hg ²⁺ ions. These results demonstrated the efficacy and advantages of the new Tb ³⁺ complex-based luminescence probe for the sensitive and selective detection of Hg ²⁺ ions.