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 N,N-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 via modulating the dissociation of ligands on the NC surface, which is totally different from the previously reported AIE phenomena in the NC field.
Highlights
Most of the previous reports on aggregationinduced enhancement of fluorescence in NCs are induced by the restriction of intramolecular motion (RIM)
By the addition of TPP into an N,N-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
The Ag29(BDT)12(TPP)[4] NC was prepared following a method previously published by Bakr and coworkers.[27]
Summary
Noble metal nanoclusters (NCs) have attracted widespread attention due to their advantages of atomically precise structures, distinct physical/chemical properties, and extensive catalytic/biomedical applications.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16] Among these interesting physical/chemical properties, photo-luminescence (PL) represents one of the most fascinating features owing to the low toxicity, good photostability, and high biocompatibility of NCs.[1,2,8,17,18,19,20,21,22,23,24] several luminescent NCs have been reported,[8,18,21,22,23,24,25,26,27,28,29,30,31] most of them exhibit lower quantum yields (QYs) compared with other uorescent nanomaterials (such as lanthanide nanoparticles,[32] organic dyes[33] and quantum dots34), which severely impedes extensive application of uorescent NCs in biological and sensing elds. How can we enhance the QY of uorescent NCs with new patterns? Addressing these issues will develop a powerful and practical strategy for synthesizing more uorescent NCs with enhanced PL QYs, and promote wide-range application of AIE in the NC eld In the NC eld, the AIE strategy could boost the PL QY through facile approaches (e.g., solvent- or cationinducing approaches).[19,25] the previously reported enhancements of uorescence in NCs have mostly been achieved by the restriction of intramolecular motion (RIM, a general mechanism in AIE materials).[19,25] This raises some interesting questions: are there any other patterns (other than RIM) of AIE that exist in the NC eld? If so, how can we enhance the QY of uorescent NCs with new patterns? Addressing these issues will develop a powerful and practical strategy for synthesizing more uorescent NCs with enhanced PL QYs, and promote wide-range application of AIE in the NC eld
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