Photon Upconversion Enhanced by Ag₂₉ Nanocluster Sensitizers and Multifunctional P(DPA)₃ Acting as Triplet Mediator, Annihilator, and Emitter

The [Ag 29 (BDT) 12 ] 3– nanocluster ( Ag 29, BDT = 1,3-benzenedithiolate) is renowned for its high stability, photoluminescence, and ability to accommodate up to four phosphine compounds as secondary ligands. Herein, the multichromophoric phosphine derivative P(DPA) 3, bearing three 9,10-diphenylanthracene (DPA) units, was employed to serve triple roles: triplet-energy mediator ligand, annihilator, and emitter. By adding an excess amount of P(DPA) 3 to Ag 29, a solution was prepared containing [Ag 29 (BDT) 12 [P(DPA) 3 ] n ] 3– ( Ag 29 PDPA, n = 1–4) complexes coexisting with unbound (free) P(DPA) 3 molecules. This enabled efficient intra- and intermolecular triplet energy transfer from photoexcited Ag 29, first to the bound and then to the unbound P(DPA) 3 . Under 532 nm excitation, the system achieved a green-to-blue UC internal quantum yield of 24.0% (48% normalized to the 100% maximum) and a significantly low threshold intensity of 2.0 mW cm –2 . Remarkably, this performance rivals that of the benchmark Pt(II)-octaethylporphine/DPA pair, establishing the Ag 29 PDPA /P(DPA) 3 combination as a high-performing green-to-blue UC system.