A fluorescence turn-down-up detection of Cu2+and pesticide quinalphos using carbon quantum dot integrated UiO-66-NH2

Synthesis of a fluorescent probe consisting of carbon quantum dot integrated metal-organic framework (OPCD@UiO-66-NH2) via a facile one-pot route has been reported. Carbon dot derived from orthophenylenediamine (OPCD) with a PLQY (26%) has been deposited on UiO-type metal organic framework by introducing OPCD during the synthesis of MOF. The resulting fluorescent OPCD@UiO-66-NH2 composite shows better fluorescence properties as well as photostability than pristine OPCD. The molecular interaction between UiO-66-NH2 and Cu2+ can be sensed by encapsulated OPCD. As a result the OPCD@UiO-66-NH2 shows remarkable fluorescence quenching on addition of Cu2+. However, in presence of organophosphorus pesticide quinalphos, the fluorescence intensity (at lambda 425) of CD@UIO-66-NH2 is regained because of competitive binding of Cu2+ with quinalphos and releasing OPCD@UIO-66-NH2 to the medium. Thus a dual sensor for Cu2+ and quinalphos can be established by measuring fluorescence intensity at lambda 425. The relative increase in fluorescence intensity for quinalphos (F/F0) works linearly in the concentration range 0-16 mu M and the limit of detection is found to be 0.3 nM. The specific and selective recognition of our probe towards organophosphorus pesticide quinalphos makes it suitable for real field applications.