Abstract
A water-soluble and emissive Eu-complex (EuL1) bearing a DO3A(Eu(3+))-pyridine-aza-crown motif has been prepared and its Cu(2+) complex has been demonstrated to be a smart luminescence "off-on" gate for H(2)S detection in water with a nano-molar detection limit (60 nM). EuL1 binds to Cu(2+) ions selectively (K(B) = 1.2 × 10(5) M(-1)) inducing 17-fold luminescence quenching and forming a 1 : 1 stoichiometric complex (EuL1-Cu(2+)), which responds to H(2)S selectively with restoration of the original Eu emission of EuL1 followed by a further 40-fold luminescence enhancement, forming a 1 : 1 stoichiometric complex (EuL1-Na(2)S, K(B) = 1.5 × 10(4) M(-1)). Without Cu(2+) ions, EuL1 showed non-specific binding towards H(2)S with only a 5-fold luminescence enhancement.