The Reducing Agents in Sonochemical Reactions without Any Additives

Abstract

It has been experimentally reported that not only oxidation reactions but also reduction reactions occur in aqueous solutions under ultrasound without any additives. According to the numerical simulations of chemical reactions inside an air or argon bubble in water without any additives under ultrasound, reducing agents produced from the bubbles are H, H2, HO2 (which becomes superoxide anion (O2−) in liquid water), NO, and HNO2 (which becomes NO2− in liquid water). In addition, H2O2 sometimes works as a reducing agent. As the reduction potentials of H and H2 (in strongly alkaline solutions for H2) are higher than those of RCHOH radicals, which are usually used to reduce metal ions, H and H2 generated from cavitation bubbles are expected to reduce metal ions to produce metal nanoparticles (in strongly alkaline solutions for H2 to work). It is possible that the superoxide anion (O2−) also plays some role in the sonochemical reduction of some solutes. In strongly alkaline solutions, hydrated electrons (e−aq) formed from H atoms in liquid water may play an important role in the sonochemical reduction of solutes because the reduction potential is extremely high. The influence of ultrasonic frequency on the amount of H atoms produced from a cavitation bubble is also discussed.

Sonochemical decomposition effects of nickelocene aiming for low-temperature and dispersant-free synthesis of nickel fine particle

“…In this study, N 2 H 4 ·H 2 O and 2-PrOH was used, so it is assumed that reducing radicals (H, CH 3 radicals, etc.) were generated under ultrasound irradiation [45] . To investigate the effects of such radicals, NiCp 2 was irradiated in 2-PrOH.…”

Solution-Phase Synthesis of KCl Nanocrystals Templated by PEO-PPO-PEO Triblock Copolymers Micelles

“…Organic molecules possessing a hydroxyl group often have reducing capacity [36]. To study the role of the hydroxyl group of P123, carboxylic acid-ended P123 was synthesized.…”