Early dynamics of the emission of solvated electrons from nanodiamonds in water

Abstract

Solvated electrons are among the most reductive species in aqueous environment. Diamond materials have been proposed as a promising source for solvated electrons, but the underlying emission process in water remains elusive so far. Here, we show spectroscopic evidence for the emission of solvated electrons from nanodiamonds upon excitation with both deep ultraviolet (255 nm) and visible (400 nm) light using ultrafast transient absorption. The crucial role of surface termination for the emission process is evidenced by comparing hydrogenated, hydroxylated and carboxylated nanodiamonds. Especially, hydrogenated nanodiamonds are able to generate solvated electron upon visible light excitation, while they show a sub-ps recombination due to trap states when excited with deep ultraviolet light. The essential role of surface reconstructions on the nanodiamonds in these processes is proposed based on density functional theory calculations. These results open new perspectives for solar-driven emission of solvated electrons in aqueous phase using nanodiamonds.

Photo-excited charge transfer from adamantane to electronic bound states in water

“…3 One particularly interesting type of catalysts are nanodiamonds, which can act as electron donors upon radiation with UV/Vis light. 14,15 Nanodiamonds, similar to a planar diamond surface in general, have a negative electron affinity (NEA), i.e., the lowest unoccupied molecular orbital (LUMO) of a nanodiamond has a higher energy than a free electron in the vacuum. Furthermore, the outwards-pointing surface dipoles of the diamond C-H bonds facilitate the movement of the electron from the diamond surface into the adjacent medium.…”