Colorimetric determination of glutathione by using a nanohybrid composed of manganese dioxide and carbon dots

A kind of single-layer carbon based dots (CDs) with abundant carboxyl functional groups was hybridized with manganese dioxide (MnO2). The resulting nanohybrid is stable and can be well dispersed in water. MnO2 is capable of oxidizing the substrate 3,3′5,5′-tetramethylbenzidine (TMB) to form a blue product whose absorption (peaking at 655 nm) fades in the presence of glutathione (GSH). A sensitive and selective colorimetric GSH assay was worked out that has a linear response in the 10 to 0.1 µM GSH concentration range, with a 0.095 μM detection limit. The method was applied to the determination of GSH in spiked fetal calf serum where it gave excellent recoveries.