Chen Zongwei, Meng Xiaoyi, Lu Yinjie, Ding Chenxi, Huo Jingzhu, Meng Xinyi, Li Zhengxiao, Guo Fengqi, Wu Kaifeng
Henan Institute of Advanced Technology, Zhengzhou University, Zhengzhou, Henan 450052, China.
State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China.
J Am Chem Soc. 2024 Jul 17;146(28):19360-19368. doi: 10.1021/jacs.4c05364. Epub 2024 Jun 4.
High-efficiency generation of spin-triplet states in organic molecules is of great interest in diverse areas such as photocatalysis, photodynamic therapy, and upconversion photonics. Recent studies have introduced colloidal semiconductor nanocrystals as a new class of photosensitizers that can efficiently transfer their photoexcitation energy to molecular triplets. Here, we demonstrate that metallic Ag nanoparticles can also assist in the generation of molecular triplets in polycyclic aromatic hydrocarbons (PAHs), but not through a conventional sensitization mechanism. Instead, the triplet formation is mediated by charge-separated states resulting from hole transfer from photoexcited PAHs (anthracene and pyrene) to Ag nanoparticles, which is established through the rapid formation and subsequent decay of molecular anions revealed in our transient absorption measurements. The dominance of hole transfer over electron transfer, while both are energetically allowed, could be attributed to a Marcus inverted region of charge transfer. Owing to the rapid charge separation and the rapid spin-flip in metals, the triplet formation yields are remarkably high, as confirmed by their engagement in production of singlet oxygen with a quantum efficiency reaching 58.5%. This study not only uncovers the fundamental interaction mechanisms between metallic nanoparticles and organic molecules in both charge and spin degrees of freedom but also greatly expands the scope of triplet "sensitization" using inorganic nanomaterials for a variety of emerging applications.
在光催化、光动力疗法和上转换光子学等多个领域，有机分子中自旋三重态的高效产生备受关注。最近的研究引入了胶体半导体纳米晶体作为一类新型光敏剂，它们能够有效地将光激发能量转移到分子三重态。在此，我们证明金属银纳米颗粒也能协助多环芳烃（PAHs）中分子三重态的产生，但并非通过传统的敏化机制。相反，三重态的形成是由电荷分离态介导的，这种电荷分离态源于光激发的PAHs（蒽和芘）向银纳米颗粒的空穴转移，这一点通过我们瞬态吸收测量中揭示的分子阴离子的快速形成及随后的衰减得以证实。在能量上两者都可行的情况下，空穴转移比电子转移占主导地位，这可能归因于电荷转移的马库斯反转区域。由于金属中电荷的快速分离和快速的自旋翻转，三重态的形成产率非常高，通过它们参与单线态氧的产生且量子效率达到58.5%得以证实。这项研究不仅揭示了金属纳米颗粒与有机分子在电荷和自旋自由度方面的基本相互作用机制，还极大地扩展了使用无机纳米材料进行三重态“敏化”以用于各种新兴应用的范围。
