Researchers obtain >99% photoluminescence quantum yield in metallic nanoclusters

A analysis group has achieved near-unity room-temperature photoluminescence quantum yield (PLQY) (>99%) within the near-infrared (NIR) emission of metallic nanoclusters in answer. Their work is revealed in Science.

Gold nanoclusters (Au NCs) as NIR-emissive supplies maintain potential in biomedical functions. Nonetheless, the PLQY of Au NCs within the NIR area is usually low, typically lower than 10%. To handle this drawback, researchers synthesized Au₂₂(^tBuPhC≡C)₁₈(Au₂₂) and its copper-doped counterpart, Au₁₆Cu₆(^tBuPhC≡C)₁₈ (Au₁₆Cu₆), to review their photophysical properties.

Single-crystal X-ray diffraction evaluation revealed that Au₂₂ and Au₁₆Cu₆ share comparable buildings. Au₂₂ confirmed an emission peak at 690 nm and Au₁₆Cu₆ at 720 nm. Absolutely the PLQY of Au₂₂ and Au₁₆Cu₆ in air have been 9% and 95%, respectively.

Within the deaerated answer, the PLQY of Au₁₆Cu₆ reached 100%, measured by each absolute and relative strategies. Time-correlated single-photon counting measured the photoluminescence lifetimes of Au₂₂ and Au₁₆Cu₆ to be 485 ns and 1.64 μs, respectively.

Additional investigation of NCs’ excited-state dynamics by transient-absorption spectroscopy revealed that each NCs’ luminescent states originated from the triplet state (T₁), with distinct dynamic processes noticed in femtosecond transient-absorption spectroscopy. Underneath 380 nm excitation, Au₂₂ confirmed a gradual rise of 148 ps, whereas Au₁₆Cu₆ confirmed a fast rest of 0.5 ps.

Triplet sensitization experiments confirmed that these processes are attributed to ultrafast intersystem crossing (ISC) from singlet state (S₁) to T₁. Attributable to copper doping, Au₁₆Cu₆ has a smaller ∆E_st, considerably accelerating its ISC price. Consequently, Au₁₆Cu₆ finally showcases PLQY near 100%.

The strategy to realize near-unity PLQY might allow the event of extremely emissive metallic cluster supplies. Particularly, this work demonstrates that near-unity PLQY may be attained with an alloy of gold-copper nanoclusters even in answer at room temperature, which can allow functions starting from organic imaging to luminescent units.

The analysis group included Prof. Zhou Meng’s group from the College of Science and Expertise of China of the Chinese language Academy of Sciences (CAS), collaborating with Prof. Wang Quanming’s group from Tsinghua College.