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

Abstract

The research concerns the reduction of graphene oxide (GO) by excess electrons on TiO 2 nanocrystallites, e TiO 2 − , produced with the aid of ionizing radiation in the presence of 2-propanol at acidic pH prior to mixing with a GO solution. Under these conditions, 2-propanol reacts with the radiation-produced • OH radicals and produces the strongly reducing CH 3 C • OHCH 3 free radicals. The latter, together with the radiation-produced hydrated electrons, reacts with the TiO 2 nanoparticles by electron transfer, producing up to 60 excess electrons per colloid particle. The reaction of e TiO 2 − with GO takes place after mixing the two sols. The reaction kinetics shows a multistage reduction, extending from seconds to many minutes. Simulations of the time profile of e TiO 2 − based on the complex kinetics involving four types of reactive GO segments reacting with e TiO 2 − agree with the observed rate of electron decay. The multireaction kinetics is expected in view of several reducible segments of GO (CC, C− O−C, C−OH, and CO) and the trapping energy distribution of e TiO 2 − . GO used in the present study had 48.8% CC (sp 2 ), 3.4% C−C (sp 3 ), 29.6% C−O bonds (as C−OH and C−O−C), 12.6% CO, and 5.6% O−CO. XPS analysis along the reaction time shows that the reduction of the oxygen-containing segments is the fastest process, while the saturation of CC double bonds is considerably slower. The latter involves the formation of C−H and C−C bonds. High-resolution transmission electron microscopy (HRTEM) shows the formation of nanodiamond islands within the amorphous carbon backbone.

When x-rays alter the course of your experiments*

“…In a previous section, it was noted that the presence of an interface can complicate matters and this is also the case with more complex solutions in which different particles are grafted to each other. An elaborate example can be found in the reduction of graphene oxide attached to TiO 2 particles in an acidic environment [132].…”

Modern trends in the development of nuclear power: from environmental friendliness to safe utilitarianism

“…So ionizing radiation is used for water and wastewater treatment and the secondary use of water resources after the removal of bisphenol A [6]; in industrial technologies -for the reduction of graphene by electrons of titanium dioxide, necessary for desalination of water, in the production of energy-saving light bulbs, heavy-duty batteries, implants, flexible electronics, etc. [7]. Ionizing radiation has become an effective way of modifying natural and synthetic polymers as a result of point anionic and cationic polymerization, crosslinking and degradation processes.…”