A UV-vis-fluorescence-smartphone-assisted hydrogel “three-in-one” platform based on light-responsive carbon dot nanozyme for multimodal glyphosate detection

The establishment of a fast and precise method for glyphosate detection holds critical importance in ensuring food safety. Herein, a multimodal sensing platform that integrated UV-vis, fluorescence and smartphone-assisted portable hydrogel kit was applied to detect glyphosate relying on the light-responsive oxidase-mimicking activity and intrinsic fluorescence of carbon dots (C-dots). C-dots enable the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), resulting in blue-colored oxidized TMB (oxTMB) along with enhanced absorbance at 652 nm. Simultaneously, the inner filter effect between oxTMB and C-dots induces the fluorescence quenching of C-dots. However, the introduction of copper ions can capture photogenerated electrons, thereby inhibiting the oxidase-mimicking catalytic activity of C-dots, leading to a decrease in absorbance and the restoration of fluorescence. Once glyphosate is present in the system, it can coordinate with copper ions to restore the catalytic activity of C-dots, thereby causing an increase in absorbance and a simultaneous decrease in fluorescence. Consequently, quantification detection of glyphosate can be realized via UV-vis and fluorescence modes. More importantly, in light of the changes in solution color, a smartphone-assisted portable hydrogel kit was also developed for glyphosate detection. Therefore, a UV-vis-fluorescence-smartphone-assisted hydrogel “three-in-one” platform was established for glyphosate analysis with corresponding limits of detection as low as 0.31, 0.12 and 5.07 µg/mL. This platform can achieve glyphosate detection within just one minute. Moreover, compared with single-mode detection platforms, this multi-mode detection platform ensures greater accuracy, thus holding broader application prospects.