Fluorescence Spectroscopy Study on the Reaction of Hydroxyl Radicals and Hydrated Electrons in MXene Suspension

The reactive species including hydroxyl radicals (•OH) and hydrated electrons (eaq –) produced by radiolysis of liquid water play a central role in radiation chemistry. However, most quantification studies of the reaction of these species have been established in a homogeneous phase rather than in heterogeneous systems, which greatly limited the in-depth understanding of the knowledge of heterogeneous systems such as nanoparticle suspension. MXenes as active antioxidants and catalysts have been widely studied. Herein, the yields of radiation-induced •OH and eaq – in Ti3C2T x (TC) MXene suspension were investigated by a simple fluorescence spectroscopy using the optimized coumarin method. The results indicate that the yield of •OH in TC suspension decreased by increasing the TC concentration with a reaction rate constant of 1.58 × 108 L g –1 s–1 between •OH and TC, which implies that TC acts as an •OH scavenger and a radioprotectant. Also, the oxidation state of Ti in TC nanosheets increased after reacting with •OH. In addition, a higher yield of eaq – was achieved in N2O-saturated TC suspension than in liquid water. The generated eaq – per gram of TC nanosheets decreased and H2 produced by TC suspension after irradiation increased by increasing the TC concentration, which indicates the competing recombination reaction of eaq – to form H2 in high-concentration TC suspension. The work provides a facile method to study the reaction of •OH and eaq – with nanoparticles dispersed in water.