Nanoparticles in a box: a concept to isolate, store and re-use colloidal surfactant-free precious metal nanoparticles

A concept is introduced that allows for the isolation, storage and re-use of surfactant-free precious metal nanoparticles (NPs) of catalytic relevance (Pt and Ru). Surfactant-free NPs well-defined in size (1-2 nm) are prepared in alkaline ethylene glycol. After synthesis these NPs are stabilized by surface bound CO, formed during synthesis by solvent oxidation, and OH-, added to the reaction mixture. We present a protocol that allows switching reversibly the stabilization between a CO-protected and OH--protected state. Most importantly, OH--protected Pt and Ru NPs exhibit remarkable resistance against sintering. These NPs can be isolated as solids, stored and put into boxes to be shipped. Thereafter they can be redispersed without changes in particle size or loss in catalytic activity. These results are expected to be of scientific and industrial relevance, as a methodology is introduced to handle surfactant-free catalytic nanoparticles like a normal solid chemical.