Photochemical deposition of surface-clean silver nanoparticles on nitrogen-doped graphene quantum dots for sensitive colorimetric detection of glutathione

In this work, a novel colorimetric sensor is designed for the sensitive detection of glutathione (GSH) based on the intrinsic peroxidase-like activity of Ag nanoparticles supported on the nitrogen-doped graphene quantum dots (Ag NPs-N-GQDs). The Ag NPs-N-GQDs nanocomposites are prepared by a facile one-step photocatalytic strategy and only N-GQDs were used as photocatalytic agents. Therefore, the surface of the obtained Ag NPs is clean without the capping of surfactant. TEM, XRD and XPS characterizations clearly show that Ag NPs-N-GQDs have been successfully prepared. Such non-surfactant capped Ag NPs provide naked catalytic surface with highly catalytic activity, which can catalyze the oxidation of 3,3′5,5′-tetramethylbenzidine (TMB) to oxTMB with the presence of H 2 O 2 along with a visual color variation. Since GSH can reduce oxTMB, the UV–vis absorption intensity of oxTMB shows a strong dependence on the concentration of GSH. The novel Ag NPs-N-GQDs-TMB-H 2 O 2 system exhibits high sensitivity and selectivity for the detection of GSH with a low detection limit of 31   nM and a wide detection linear range of 0.1–157.6   μM. Furthermore, the novel sensor system shows great potential application for GSH detection in blood serum sample, and easy-to-make analytical approaches in the future.