Smartphone-assisted paper-based analytical device integrated with photo-responsive oxidase mimetic for colorimetric detection of carbosulfan

Given the significant harm caused by carbosulfan, the prominent characteristics of photo-responsive nanozymes and the bright prospects of paper-based analytical devices (PADs), developing a photo-responsive nanozyme-mediated colorimetric PAD for the convenient and accurate detection of carbosulfan is highly desired. Herein, carbon dots/graphitic carbon nitride (C-dots/g-C3N4) photo-responsive oxidase mimetic is constructed and employed in the field of colorimetric PAD for carbosulfan detection. C-dots/g-C3N4 with excellent photo-responsive oxidase-like activity is obtained by controlling the loading amounts of C-dots on g-C3N4, which can be ascribed to the enhanced visible light-harvesting ability and more efficient charge separation and transfer. C-dots/g-C3N4 is capable of catalyzing the oxidation of 3,3’,5,5’-tetramethylbenzidine with noticeable color changes due to the formation of singlet oxygen and photogenerated holes. Whereas, the oxidase-like activity of C-dots/g-C3N4 is inhibited by the reductive sulfide compound derived from the hydrolysis of carbosulfan under acidic medium, thereby inhibiting the chromogenic reaction. Based on the above facts, a colorimetric PAD for carbosulfan detection is proposed. The designed PAD shows a good linear range of 5–60 μM with a detection limit down to 2.52 μM. Moreover, the PAD demonstrates high accuracy when detecting carbosulfan in real samples. This work may expand the applications of photo-responsive nanozymes in PADs. [Display omitted] ●C-dots/g-C3N4 nanozyme exhibits outstanding light-responsive oxidase-like activity.●Controlling the amounts of C-dots contributes to improving oxidase-like activity.●C-dots/g-C3N4 nanozyme-based colorimetric PAD for carbosulfan detection is designed.●The PAD can be practically applied for quantification of carbosulfan in real samples.