Enhanced triplet state generation through radical pair intermediates in BODIPY-quantum dot complexes
Enhanced triplet state generation through radical pair intermediates in BODIPY-quantum dot complexes
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DOI：
10.1063/1.5136045
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发表时间：
2019-12-28
影响因子：
4.4
通讯作者：
Lian, Tianquan
中科院分区：
文献类型：
--
作者：
Jin, Tao;Uhlikova, Natalie;Lian, Tianquan
在分子络合物中，通过自由基对中间体产生三重态激发态已被广泛研究。类似的方案在量子点-有机分子的杂化结构中仍然很少见，尽管最近人们对量子点敏化三重态激发态的产生产生了强烈的兴趣。在这里，我们证明了通过在量子点导带和氧化的BODIPY中由一个未配对的电子组成的自由基对中间态，可以提高在CdSe量子点-BODIPY络合物中从单态到三重态的跃迁效率。在650 nm光激发下，BODIPY分子通过电子转移形成电荷分离态(时间常数为6.33+/-1.13 ns)，与BODIPY分子内基态相互竞争，自由基对通过背电荷复合衰变为三重态(时间常数为158+/-28 ns)或BODIPY基态。BODIPY三重态激发态产生的总量子效率为(27.2+/-3.0)%。这一杂化体系中有效的三重态形成和中间自由基对态的发现表明，量子点-分子络合物可能是一个很有前途的自旋电子学应用平台。由AIP出版公司授权出版。
Generation of triplet excited states through radical pair intermediates has been extensively studied in molecular complexes. Similar schemes remain rare in hybrid structures of quantum dot-organic molecules, despite intense recent interest of quantum dot sensitized triplet excited state generation. Herein, we demonstrate that the efficiency of the intersystem crossing from the singlet to the triplet state in boron dipyrromethene (BODIPY) can be enhanced in CdSe quantum dot-BODIPY complexes through a radical pair intermediate state consisting of an unpaired electron in the quantum dot conduction band and that in oxidized BODIPY. By transient absorption spectroscopy, we show that the excitation of BODIPY with 650 nm light leads to the formation of a charge separated state by electron transfer from BODIPY to CdSe (with a time constant of 6.33 +/- 1.13 ns), competing with internal conversion to the ground state within BODIPY, and the radical pair state decays subsequently by back charge recombination to generate a triplet excited state (with a time constant of 158 +/- 28 ns) or the ground state of BODIPY. The overall quantum efficiency of BODIPY triplet excited state generation was determined to be (27.2 +/- 3.0)%. The findings of efficient triplet state formation and intermediate radical pair states in this hybrid system suggest that quantum dot-molecule complexes may be a promising platform for spintronics applications. Published under license by AIP Publishing.