Unusual Reduction of Graphene Oxide by Titanium Dioxide Electrons Produced by Ionizing Radiation. Reaction Products and Mechanism

The research concerns the reduction of graphene oxide (GO) by excess electrons on TiO2 nanocrystallites, eTiO2-, produced with the aid of ionizing radiation in the presence of 2-propanol at acidic pH prior to mixing with GO solution. Under these conditions, 2-propanol reacts with the radiation produced •OH radicals and produces the strongly reducing CH3C•OHCH3 free radical. The latter, together with the radiation produced hydrated electrons react with the TiO2 nanoparticles by electron transfer, producing up to 60 excess electrons per colloid particle. Reaction of eTiO2- with GO takes place after mixing the two sols. The reaction kinetics shows a multi-stage reduction, extending from seconds to many minutes. Simulations of the time profile of eTiO2- based on the complex kinetics involving four types of reactive GO segments reacting with eTiO2- agree with the observed rate of electron decay. The multi-reaction kinetics is expected in view of several reducible segments of GO (C=C, C–O–C, C–OH and C=O) and t...