A ratiometric fluorescence/colorimetric dual-response sensor based on fluorescent nanozymes and smartphone-assisted for accurate determination of glyphosate residues

Abstract

In this study, a ratio-fluorescence/colorimetric sensor based on copper-based metal-organic framework nanozymes (Cu-BH) was developed for detection of organophosphorus pesticides (OPs). The sensor utilized the intrinsic fluorescence properties of the nanozymes in combination with the synergistic effect of ophenylenediamine (OPD). Cu-BH catalyzes the conversion of OPD into a yellow fluorescent product (oxOPD), exhibits ultraviolet absorption and fluorescence absorption peaks at 416 nm and 567 nm, respectively. Meanwhile, oxOPD quenched the fluorescence of Cu-BH at 430 nm via fluorescence internal filtering effect (IFE), thereby establishing a colorimetric signal (A 416 ) and fluorescence signal (F 567 /F 430 ).When introduction of OPs into system, OPs interact with the copper ions of the Cu-BH nanozymes, diminishing the ability of Cu-BH to oxidize OPD, which progressively decreased the absorbance at 416 nm and diminishing the fluorescence intensity at 567 nm. The signal from the dual-mode sensor exhibited a linear relationship with Gly concentration, the LOD (3σ/K) for ratio-fluorescence and colorimetric modes of 0.103 ng/mL and 0.118 ng/mL, respectively. Moreover, smartphone-based RGB color digitization provided a quantifiable B/R value with a favorable linear response (1×10 - 3 -1×10 2 μg/mL). This work not only proposes a straightforward and low-cost approach to pesticide sensing but also exerts a favorable effect on the establishment of food safety pre-warning systems.