Sample Alexander D, Guan Jun, Hu Jingtian, Reese Thaddeus, Cherqui Charles R, Park Jeong-Eun, Freire-Fernández Francisco, Schaller Richard D, Schatz George C, Odom Teri W
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States.
Nano Lett. 2021 Sep 22;21(18):7775-7780. doi: 10.1021/acs.nanolett.1c02740. Epub 2021 Sep 7.
This Letter describes strong coupling of densely packed molecular emitters in metal-organic frameworks (MOFs) and plasmonic nanoparticle (NP) lattices. Porphyrin-derived ligands with small transition dipole moments in an ordered MOF film were grown on Ag NP arrays. Angle-resolved optical measurements of the MOF-NP lattice system showed the formation of a polariton that is lower in energy and does not cross the uncoupled MOF Q band. Modeling predicted the upper polariton energy and a calculated Rabi splitting of 110 meV. The coupling strength was systematically controlled by detuning the plasmon energy by changing the refractive index of the solvents infiltrating the MOF pores. Through transient absorption spectroscopy, we found that the lower polariton decays quickly at shorter time scales (<500 ps) and slowly at longer times because of energy transfer from the upper polariton. This hybrid system demonstrates how MOFs can function as an accessible excitonic material for polariton chemistry.
本信函描述了金属有机框架（MOF）中密集排列的分子发射体与等离子体纳米颗粒（NP）晶格的强耦合。在有序MOF薄膜中具有小跃迁偶极矩的卟啉衍生配体生长在银NP阵列上。对MOF-NP晶格系统进行的角分辨光学测量表明形成了一种能量较低且不穿过未耦合MOF Q带的极化激元。建模预测了上极化激元能量以及计算得出的110毫电子伏特的拉比分裂。通过改变渗透MOF孔的溶剂的折射率来失谐等离子体能量，从而系统地控制耦合强度。通过瞬态吸收光谱法，我们发现由于上极化激元的能量转移，下极化激元在较短时间尺度（<500皮秒）下快速衰减，而在较长时间下缓慢衰减。这种混合系统展示了MOF如何作为极化激元化学中一种易于获取的激子材料发挥作用。
