A N-Cds/Auncs@Zif-8-Assisted Ratiometric Fluorescent Nanosensor for Ultrasensitive Detection of Glyphosate

Abstract

The residue of glyphosate (Gly), a widely used herbicide in agricultural production, in diverse matrices from long-term and widespread overspray has posed serious threats to public health. Development of reliable methods for its detection is in great urgency. In this study, a novel ratiometric fluorescent was established for the detection of glycine (Gly) by encapsulating N-doped carbon dots (N-CDs) and gold nanoclusters (AuNCs) in zeolitic imidazole framework-8 (ZIF-8) as the dual-emissive fluorescence probes that displayed greatly-amplified double fluorescence responses at 410 nm and 650 nm. Due to the adsorption property of ZIF-8, the N-CDs/AuNCs@ZIF-8 nanoprobes accumulated Cu2+ to quench the red fluorescence of AuNCs, and the blue fluorescence of N-CDs was stable. While, thiocholine, A product of acetylthiocholine hydrolyzed by acetylcholinesterase could potentially coordinate with Cu2+, resulting in significant fluorescence recovery of AuNCs. This phenomenon was utilized for the quantitation of Gly, due to its inhibitory effect on acetylcholinesterase activity. By calculating the fluorescence intensity ratio (I650/I410), Gly in real samples could realize accurate determination in a wide concentration range of 2-100 ng/mL with the detection limit low to 2.6 ng/mL because of the anti-interference and the self-correction ability of the two signals. The N-CDs/AuNCs@ZIF-8 nanoprobes-assisted “signal on-off-on-off” ratiometric fluorescent nanosensor exhibited high specificity, good reliability and accuracy for Gly in real malt samples with recoveries of 93.67-108.2%, as well as unique merits of rapid preparation, simple sample treatment, easy operation, and high response. This study presents a versatile detection tool for the versatile sensing of a range of trace analytes in other matrices, which can be extended to a full range of environmental and food safety applications.

Keywords: Ratiometric fluorescent nanosensor, N-CDs/AuNCs@ZIF-8 dual-emissive probes, Ultrasensitive detection, Glyphosate, Edible and medicinal malt