A smart "off-on" gate for the in situ detection of hydrogen sulphide with Cu(ii)-assisted europium emission

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