Observation of a new type of aggregation-induced emission in nanoclusters

Abstract

The strategy of aggregation-induced emission (AIE) has been widely used to enhance the photo-luminescence (PL) in the nanocluster (NC) research field. Most of the previous reports on aggregation-induced enhancement of fluorescence in NCs are induced by the restriction of intramolecular motion (RIM). In this work, a novel mechanism involving the restriction of the "dissociation-aggregation pattern" of ligands is presented using a Ag₂₉(BDT)₁₂(TPP)₄ NC (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) as a model. By the addition of TPP into an <i>N</i>,<i>N</i>-dimethylformamide solution of Ag₂₉(BDT)₁₂(TPP)₄, the PL intensity of the Ag₂₉(BDT)₁₂(TPP)₄ NC could be significantly enhanced (13 times, quantum yield from 0.9% to 11.7%) due to the restricted TPP dissociation-aggregation process. This novel mechanism is further validated by a low-temperature PL study. Different from the significant PL enhancement of the Ag₂₉(BDT)₁₂(TPP)₄ NC, the non-dissociative Pt₁Ag₂₈(S-Adm)₁₈(TPP)₄ NC (S-Adm: 1-adamantanethiol) exhibits a maintained PL intensity under the same TPP-addition conditions. Overall, this work presents a new mechanism for largely enhancing the PL of NCs <i>via</i> modulating the dissociation of ligands on the NC surface, which is totally different from the previously reported AIE phenomena in the NC field.