Insight into the Role of Copper in the Transformation of a [Ag25(2,5-DMBT)16(DPPF)3]+ Nanocluster: Doping or Oxidation.

ABSTRACT

Structural transformation in nanoclusters is important not only in obtaining functional nanoclusters controllably but also in understanding their structural evolution. This study investigated the role of Cu2+ ions in structural transformation. It was revealed that Cu2+ exhibits two different functions, doping and oxidation, in determining the final products. Starting with a new silver nanocluster, [Ag25(2,5-DMBT)16(DPPF)3]+ (Ag25), a doping process would occur when no more than 0.5 equiv of Cu2+ was added, resulting in the formation of [Ag25-xCux(2,5-DMBT)16(DPPF)3]+ (Ag25-xCux). When 1 equiv of Cu2+ was introduced to Ag25, a structural transformation process would occur instead, forming [Ag22-xCux(2,5-DMBT)12(DPPF)4Cl4]2+ (Ag22-xCux). Considering the similar Cu doping amounts in Ag25-xCux and Ag22-xCux, an oxidation process induced by Cu2+ in the solution can account for this transformation process, which was further demonstrated by the addition of other oxidant substitutions. On the other hand, the role of other valence states of copper in the transformation of the Ag25 cluster was explored. It was found that copper powder can hardly change Ag25 and Cu+ can only proceed the doping process, both of which are different from the role of Cu2+. Overall, this work explores the role of copper in the transformation of the Ag25 cluster in detail, including its concentrations and valence states.