Tailoring Photothermal Performance and Stability of Atomically Precise Silver Nanoclusters by Ligand Engineering

Synthesizing silver (Ag) nanoclusters with improved photothermal performance and durability remains a challenge. Two atomically precise silver clusters, [Ag42(5-Me-dpf)12(S-Adm)4Cl2](SO3CF3)4(1) (5-Me-dpf = N,N′-di(5-methyl-2-pyridinyl) formamidine; S-Adm = 1-adamantanethiol) and [Ag42(5-Me-dpf)14(ArC≡C)3Cl](BF4)4(2) (ArC≡C = 3,5-bis(trifluoromethyl)phenylacetylide), were synthesized, and their structures were determined by single-crystal X-ray diffraction. DFT calculations indicated that both 1 and 2 feature a 20-electron superatomic configuration of 1S21P61D102S2. Remarkably, 1 and 2 exhibited significantly enhanced photothermal performance and durability. A substantial temperature increase of ∼55.7 °C within 5 min (λex = 520 nm, 0.5 W) and a record high photothermal conversion efficiency of 87.5% at 40.0 μM in N,N-dimethylformamide were observed. Charge transfer between the Ag42 kernel and arrayed 5-Me-dpf ligands in excited 1 and 2 promotes the formation of a strong transition dipole moment. This configuration is conducive to electron–phonon coupling (τe-ph) at the femtosecond scale, which promotes exceptional photothermal performance. This study paves the way for the rational design of materials with improved photothermal performance and durability.