Design Principles for Two-Dimensional Molecular Aggregates Using Kasha's Model: Tunable Photophysics in Near and Short-Wave Infrared
Design Principles for Two-Dimensional Molecular Aggregates Using Kasha's Model: Tunable Photophysics in Near and Short-Wave Infrared
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使用 Kasha 模型的二维分子聚集体设计原理：近短波红外可调谐光物理
DOI：
10.1021/acs.jpcc.9b05060
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发表时间：
2019
影响因子：
--
通讯作者：
and Caram, J. R.
中科院分区：
文献类型：
--
作者：
Deshmukh, A. P.;Koppel, D.;Chuang, C.;Cadena, D. M.;Cao, J.;and Caram, J. R.
利用近红外（NIR） （700-1000 nm）和短波红外（1000-2000 nm）电磁辐射的技术在深层组织成像、电信和卫星遥测中有应用，因为在该光谱区域散射低，背景信号减少。因此，有必要开发能够有效吸收1000纳米以上光的材料。跃迁偶极矩耦合（例如，j聚集）允许红移激子态，并提供了在红外高吸收电子态的途径。我们研究了两种菁染料的聚集体，它们的吸收峰在水中聚集时分别在800 ~ 1000 nm和1050 nm范围内发生显著的红移，具有片状形态和高摩尔吸收率（ε≈105M-1cm-1）。我们使用Frenkel激子理论扩展了Kasha的J-和h -聚集模型，并描述了在组装结构中滑移受位阻控制的二维聚集体的激子态。增加维数的结果是中间“i -聚集体”现象，它红移但显示类似于h -聚集体的带边暗态的光谱特征。我们区分H-， I-和j -聚集通过显示明亮（吸收）状态的相对位置内的状态密度使用温度依赖光谱。i -聚集体具有应用潜力，如半导体的电荷注入部分和近红外和短波红外的能量转移供体。我们的研究结果可用于更好地设计具有可预测和可调聚集的具有新的光物理性质的发色团。
Technologies which utilize near-infrared (NIR) (700–1000 nm) and short-wave infrared (1000–2000 nm) electromagnetic radiation have applications in deep-tissue imaging, telecommunications, and satellite telemetry due to low scattering and decreased background signal in this spectral region. It is therefore necessary to develop materials that absorb light efficiently beyond 1000 nm. Transition dipole moment coupling (e.g., J-aggregation) allows for red-shifted excitonic states and provides a pathway to highly absorptive electronic states in the infrared. We present aggregates of two cyanine dyes whose absorption peaks red-shift dramatically upon aggregation in water from ∼800 to 1000 nm and 1050 nm, respectively, with sheet-like morphologies and high molar absorptivities (ε ≈ 105M–1cm–1). We use Frenkel exciton theory to extend Kasha’s model for J- and H-aggregations and describe the excitonic states of two-dimensional aggregates whose slip is controlled by steric hindrance in the assembled structure. A consequence of the increased dimensionality is the phenomenon of an intermediate “I-aggregate”, one which red-shifts yet displays spectral signatures of band-edge dark states akin to an H-aggregate. We distinguish between H-, I-, and J-aggregates by showing the relative position of the bright (absorptive) state within the density of states using temperature-dependent spectroscopy. I-aggregates hold potential for applications such as charge injection moieties for semiconductors and donors for energy transfer in NIR and short-wave infrared. Our results can be used to better design chromophores with predictable and tunable aggregation with new photophysical properties.