Easy quantitative sensing of herbicide glyphosate using portable smartphone integrated PVA/chitosan composite films

Abstract

Glyphosate (Glyp) is the most widely used post-emergence herbicide commercialized by the Monsanto company under the brand name Roundup. It is an active agent of Glyp-based herbicides (GBHs). Despite its effectiveness in controlling weeds and enhancing crop yield, concerns over its potential environmental and health impacts have necessitated monitoring of Glyp residues. The present work explores the use of a very cheap sensing assay for the on-site monitoring of Glyp in aqueous media using a simple, biodegradable off-the-shelf fluorescent dye 6,7-dihydroxycoumarin (esculetin, DHC) based copper ensemble DHC·Cu²⁺. The potential of DHC·Cu²⁺ for the detection of Glyp was studied in solution, as well as using PVA/chitosan composite thin films. These composite films were also low-cost and biodegradable, making them suitable for the environment-friendly monitoring of Glyp. Remarkably, ensemble DHC·Cu²⁺ reversibly detects Cu²⁺ and Glyp making the sensing assay ideal for real-time measurements. UV-vis and emission spectral studies confirmed the detection of Glyp by DHC·Cu²⁺. The ensemble's detection limit for Glyp was determined as 1.72 μM. Job's plot indicated the formation of a 1 : 1 complex between DHC·Cu²⁺ and Glyp. The sensing assay was also applied to quantify the Glyp residues in various matrices such as water, soil, wheat, oats, and soybeans. The fluorescence enhancement and UV-vis spectral response of the sensor system were also used to design INHIBIT and IMPLICATION logic gates. In addition, the fluorometric readout was combined with a smartphone for facile on-site chemical sensing of the Glyp. The ensemble DHC·Cu²⁺ was also successfully used for bioimaging Glyp in C2C12 mouse skeletal muscle cells.