Time-domain Tollens reaction: synthesising silver nanoparticles with the formaldehyde clock.

The addition of silver(i) ions to the methylene glycol-sulphite (MGS) clock reaction results in the sudden formation of metallic silver nanoparticles. Stable suspensions are obtained in the presence of poly(vinylpyrrolidone). The time delay before the appearance of the particles, as well as their size, decreases with the initial methylene glycol concentration while their monodispersity increases.