Computational Investigation of Charge Transfer from Hydroxymethyl Radicals to Metal Nanoparticles Suspended in Water

Radicals are highly reactive species that undergo fast reactions on metal surfaces, exhibiting charge transfer to/from the surface upon adsorption. Organic acids, including weak ones, are reported to undergo deprotonation on metal surfaces. Computational studies are used to study the surface reactions of hydroxy methyl radicals, which have a high aqueous pKa (10.7) on the (111) surface of Ag, Au, and Pt. The study shows that the hydroxymethyl radical undergoes faster deprotonation on the metal surfaces than in the homogeneous media. Deprotonation on Ag and Au surfaces leads to the formation of charged NPs along with the formation of formaldehyde in accordance with the mechanism proposed by Henglein. However, on Pt(111), only partial charge transfer from the radical to the surface is observed. These results are in accordance with reported experimental results.