High-Yield Synthesis of Cu₂₉ Nanoclusters and Their Applications in Photothermal Conversion and Catalysis

Atomically precise copper nanoclusters (NCs) have received considerable interest in recent years. Significant progress is being made in understanding their synthesis, size/shape control, and crystallization techniques. Unlike Au and Ag nanoclusters, zerovalent Cu NCs are much more difficult to synthesize due to the low reduction potential of Cu(II) or Cu(I). However, Cu is unique in its catalytic reactivity and photothermal conversion. This study presents a high-yield procedure for bulk synthesis of a Cu₂₉ NC (in Cu(I) valence state) coprotected by cyclohexanethiolate (CHT) and triphenylphosphine (TPP), with its crystal structure characterized. The Cu₂₉-CHT-TPP is further investigated as an effective photothermal material as well as a catalyst for the azide-alkyne click-chemistry reactions. The Cu₂₉ NC possesses a good photothermal activity (e.g., a 22.4 °C increase in 450 s for 0.4 OD_{488 nm} when irradiated 488 nm laser of 1.75 W/cm²) and a photothermal efficiency of 33%, which rivals the best Au NCs reported. In the catalysis, it shows fast reactions and >90% yields under blue LED irradiation, along with good recyclability, when used as a homogeneous catalyst. The findings from this work may promote future explorations of Cu NCs in various applications.