Photocatalytic few atoms Ag nanoclusters produced by ultrashort light pulses

DIEGO MURACA; JESICA M. J. SANTILLÁN; LUCÍA B. SCAFFARDI; DAVID MUÑETÓN ARBOLEDA; DANIEL C. SCHINCA

Zurich

Congreso; Photonics Online Meetup (POM); 2020

Metal clusters have chemical and physical properties that are dependent only on the number of atoms they contain. These size-dependent properties, which make them suitable for applications in catalysis, photoluminescence and biomedicine among others, show significant deviations from their bulk and large nanoparticles (NPs) counterparts. Therefore metal clusters may be considered as new materials covering the intermediate stage between single atoms/molecules and bulk materials.For potential catalysis application, it is important to produce small and very small clusters, since they seem to be the most active catalyst sites. Reactivity is highly dependent on their electronic structure, leading to large variations even for sizes differing by only single atoms. In particular, Ag nanoclusters (NCs) are known to catalyse a wide range of reactions.In this work we analysed and synthesized few atoms Ag NCs by ultrashort pulse laser ablation. However, these few atoms NCs coexist with small Ag NPs (< 2 nm), hence centrifugation of the as-prepared colloids with different speeds and times was used to obtain a rich population of NCs in the supernatant.Photocatalytic activity of the obtained NCs, was assessed through degradation of methylene blue (MB) aqueous solution mixed with the as-prepared colloid and also with the supernatant of the different centrifuged colloids, while the samples were illuminated with white light. Degradation efficiency was evaluated by measuring the absorbance of MB at 660 nm at different times during illumination after addition of Ag colloids. We found that Ag colloids with larger centrifugation times had stronger photocatalytic activity, suggesting that small Ag NCs are responsible for this enhancement. It was found that even small concentrations of Ag NCs had a stronger photocatalytic action than that reported by other authors in the literature. Consequently, this work contributes to establishing a simple approach to synthesize highly photocatalytic NCs.