Long-Lived Excited State in a Solubilized Graphene Nanoribbon
Long-Lived Excited State in a Solubilized Graphene Nanoribbon
复制标题
可溶石墨烯纳米带中的长寿命激发态
DOI：
10.1021/acs.jpcc.1c10024
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发表时间：
2022-02-03
影响因子：
3.7
通讯作者：
Glusac, Ksenija D.
中科院分区：
文献类型：
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作者：
Drummer, Matthew C.;Weerasooriya, Ravindra B.;Glusac, Ksenija D.
石墨烯纳米带具有优异的吸光性能，但往往表现出较短的激发态寿命，这阻碍了它们在光催化中的应用。在这里，我们报告了一个长寿命的电荷转移三重态激发态，在一个溶解良好的，氯化石墨烯纳米带（Cl-GNR），其边缘被联嘧啶（bpm）修饰。利用稳态紫外-可见吸收和发射光谱、ps-ms时间尺度上的瞬态吸收光谱以及密度泛函理论（DFT）对Cl-GNR的光物理行为进行了观察和表征。Cl-GNR及其单体亚基氯化石墨烯量子点（Cl-GQD）采用自底向上的技术合成，生成化合物的h类似物，然后进行边缘氯化以获得可溶产物。Cl-GQD和Cl-GNR的吸收光谱出现在紫外可见光谱范围内，最低能量峰分别在375 nm和600 nm处。发现Cl-GNR中的激子表现出电荷转移特征，其bpm边缘充当电子受体。DFT计算表明激子是相对局域化的，最多分布在GNR的两个单体单元上。瞬态吸收光谱结果表明，Cl-GQD和Cl-GNR的单重态激发态发生了系统间交叉，其寿命接近300 ps，形成的三重态持续时间分别为15.7 μ s （Cl-GQD）和106 μ s （Cl-GNR）。这些特性，加上bpm位点协调过渡金属的能力，使cl - gnr成为光催化应用的有前途的光收集基序。
Graphene nanoribbons have excellent light-absorbing properties but often exhibit short excited-state lifetimes that prevent their applications in photocatalysis. Here, we report a long-lived charge-transfer triplet excited state in a well-solubilized, chlorinated graphene nanoribbon (Cl-GNR) with edges modified by bipyrimidine (bpm) moieties. The photophysical behavior of Cl-GNR was observed and characterized by steady-state UV-vis absorption and emission spectroscopy, transient absorption spectroscopy on the ps-ms timescale, and density functional theory (DFT) calculations. Both the Cl-GNR and its monomeric subunit, chlorinated graphene quantum dot (Cl-GQD), were synthesized using bottom-up techniques to produce the H-analogs of the compounds followed by edge-chlorination to achieve soluble products. The absorption spectra of Cl-GQD and Cl-GNR appear in the UV-vis range with lowest-energy peaks at 375 and 600 nm, respectively. The excitons in Cl-GNR were found to exhibit charge-transfer character with the bpm edges serving as electron acceptors. DFT calculations indicate that the excitons are relatively localized, spreading over at most two monomeric units of the GNR. Transient absorption spectroscopy shows that singlet excited states of Cl-GQD and Cl-GNR undergo intersystem crossing with similar to 300 ps lifetime to form triplet states that last for 15.7 mu s (Cl-GQD) and 106 mu s (Cl-GNR). These properties, combined with the ability of the bpm sites to coordinate transition metals, make Cl-GNRs promising light-harvesting motifs for photocatalytic applications.