Reaction Kinetics of Reducing Graphene Oxide at Individual Sheet Level Studied by Twilight Fluorescence Microscopy

Abstract

Kinetics of the reduction reaction of graphene oxide (GO) by l-ascorbic acid in a solution was examined by direct observation of an individual GO sheet with an area over 100 μm2 using Twilight fluorescence microscopy. Temporal changes of either increase in absorbance or decrease in autofluorescence from an individual GO sheet of a known layer number and an area were analyzed by the pseudo-first-order model, the pseudo-second-order model, and the Elovich model. An increase in the absorbance around 600 nm probes an extension of the π–electron conjugation length over multiple hexagonal units. All data at various conditions are best fitted with the Elovich model, implying that the activation energy increases as the reaction progresses. A decrease in the total autofluorescence intensity follows local deoxygenation of oxides. In this case, the pseudo-second-order model, which is based on a homogeneous surface with a constant activation energy, shows the best fit to all data. These results demonstrate that, for ...