Coalescence of silver nanoclusters to nanoparticles and simultaneous enhancement and quenching of excited states

Despite the successful launch of Au nanoclusters (NCs) in light energy conversion applications, the utilization of Ag NCs has been limited by their instability under continuous illumination. The main cause of photoinduced degradation pathways remains elusive. Hence, understanding the underlying mechanism behind the low stability is an urgent task to provide a new impetus for the development of Ag NCs. The slow regeneration of Ag NCs by a redox couple leads to holes in the NCs, which could result in either the photoetching of NCs or the transformation into plasmonic nanoparticles. Transient absorption spectroscopy reveals that Ag NCs coalesce into plasmonic nanoparticles and begin to experience two conflicting effects (plasmonic enhancement and quenching effect) during this in situ transformation. It also discloses that the quenching effect prevails over the plasmonic enhancement, which eventually leads to photocurrent loss under illumination.