A smart “off–on” gate for the in situ detection of hydrogen sulphide with Cu(ii)-assisted europium emission†
Abstract
A water-soluble and emissive Eu-complex (EuL1) bearing a DO3A(Eu3+)–pyridine–aza-crown motif has been prepared and its Cu2+ complex has been demonstrated to be a smart luminescence “off–on” gate for H2S detection in water with a nano-molar detection limit (60 nM). EuL1 binds to Cu2+ ions selectively (KB = 1.2 × 105 M−1) inducing 17-fold luminescence quenching and forming a 1 : 1 stoichiometric complex (EuL1–Cu2+), which responds to H2S 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–Na2S, KB = 1.5 × 104 M−1). Without Cu2+ ions, EuL1 showed non-specific binding towards H2S with only a 5-fold luminescence enhancement.