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-NH 2 ) 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-NH 2 composite shows better fluorescence properties as well as photostability than pristine OPCD. The molecular interaction between UiO-66-NH 2 and Cu 2+ can be sensed by encapsulated OPCD. As a result the OPCD@UiO-66-NH 2 shows remarkable fluorescence quenching on addition of Cu 2+ . However, in presence of organophosphorus pesticide quinalphos, the fluorescence intensity (at λ 425 ) of CD@UIO-66-NH 2 is regained because of competitive binding of Cu 2+ with quinalphos and releasing OPCD@UIO-66-NH 2 to the medium. Thus a dual sensor for Cu 2+ and quinalphos can be established by measuring fluorescence intensity at λ 425 . The relative increase in fluorescence intensity for quinalphos (F/F 0 ) 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. • A carbon dot integrated UiO fluorescence sensor has been designed for detection of quinalphos in aqueous medium. • The sensing mechanism is based on disruption of non-radiative CD@UiO-Cu 2+ complex in presence of quinalphos. • The limit of detection is 0.3 nM which is lowest among the published papers. • The sensors can be successfully used to detect quinalphos in real samples.