Quantum-size metal clusters with multiple delocalized electrons could support collective plasmon excitation, and thus, theoretically, coupling of plasmons in the few-atom limit might exist between assembled metal clusters, while currently few experimental observations about this phenomenon have been reported. Here we examined the optical absorption of DNA-templated Ag nanoclusters (DNA-AgNCs) assembled through DNA hybridization and found their absorption peaks were sensitive to the assembled distances, which share common characteristics with classical plasmon coupling. Dipolar charge distribution, multiple transition contributed optical absorption, and strongly enhanced electric field simulated by time-dependent density functional theory (TDDFT) indicated the origin of the absorption of individual DNA-AgNCs is a plasmon. The consistency of the peak-shifting trend between experimental and simulation results for assembled DNA-AgNCs suggested the possible presence of plasmon coupling. Our data imply the possibility for quantum-size structures to support plasmon coupling and also show that DNA-AgNCs possess the potential to be promising materials for construction of plasmon-coupling devices with ultrasmall size, site-specific and stoichiometric binding abilities, and biocompatibility.

中文翻译：

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DNA组装的银纳米团簇中的等离子体耦合

具有多个离域电子的量子尺寸金属簇可以支持集体等离子体激发，因此，理论上，组装的金属簇之间可能存在少数原子极限的等离子体耦合，而目前关于这种现象的实验观察报道很少。在这里，我们检查了通过 DNA 杂交组装的以 DNA 为模板的 Ag 纳米簇 (DNA-AgNCs) 的光学吸收，发现它们的吸收峰对组装距离敏感，这与经典等离子体耦合具有共同特征。偶极电荷分布、多重跃迁贡献的光吸收以及由时间相关密度泛函理论 (TDDFT) 模拟的强电场表明单个 DNA-AgNCs 的吸收起源是等离子体。组装 DNA-AgNCs 的实验和模拟结果之间的峰移趋势的一致性表明可能存在等离子体耦合。我们的数据暗示了量子尺寸结构支持等离子体耦合的可能性，并且还表明 DNA-AgNCs 具有成为构建具有超小尺寸、位点特异性和化学计量结合能力以及生物相容性的等离子体耦合装置的有前景的材料的潜力。