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

Abstract 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 λ425) 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 λ425. The relative increase in fluorescence intensity for quinalphos (F/F0) works linearly in the concentration range 0–16 μM 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.