mCP 和 Br-mCP 的超快动力学：瞬态吸收光谱的启示

IF 3.3 3区物理与天体物理 Q2 OPTICS

Journal of Luminescence Pub Date : 2024-10-12 DOI:10.1016/j.jlumin.2024.120940

Yonggang Yang , Feiyao Geng , Zhinan Jiang , Yang Liu , Tiantian Guan , Chaochao Qin , Chunsheng Zhuang , Yufang Liu

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引用次数: 0

摘要

重金属原子激活的有机室温磷光（RTP）因其磷光量子产率高、寿命长而备受关注。本研究详细分析了 1,3-双（N-咔唑基）苯（mCP）和 9,9'-（5-溴-1,3-亚苯基）双（9H-咔唑）（Br-mCP）在甲苯溶液中的瞬态吸收光谱。在 mCP 的飞秒瞬态吸收（fs-TA）光谱中，激发态吸收（ESA）信号在 630 nm 处减弱，而三重-三重吸收（TTA）信号在 420 nm 处增强。同时，在 455 纳米波长处观察到的等距点表明系统间交叉（ISC）寿命为 15.4 毫微秒。再看纳秒瞬态吸收（ns-TA）光谱，TTA 信号在 27.3 ns 达到峰值，然后逐渐减弱，测得 mCP 的三重态寿命为 2.8 μs。Br-mCP 的动态演变与 mCP 相似，但 ISC 过程更快（9.4 ns），三重态寿命更长（3.9 μs）。Br-mCP 的 ISC 过程较快，这是因为分子结构中存在重原子，导致自旋轨道耦合常数增强（ξ(S1, T3)Br-mCP = 1.371 cm-1 >；ξ(S1, T4)mCP = 0.060 cm-1）。Br-mCP 的三重态寿命延长（3.9 μs > 2.8 μs）是因为其重组能降低，从而有效减少了分子内的非辐射振动能量损失。这项工作极大地增强了我们对含有重金属原子的 RTP 材料的了解。

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Ultrafast dynamics of mCP and Br-mCP: Insights from transient absorption spectroscopy

Heavy atom activated organic room-temperature phosphorescence (RTP) has attracted considerable interest due to its high phosphorescence quantum yield and prolonged lifetime. This research provides a detailed analysis of the transient absorption spectroscopy of 1,3-Bis(N-carbazolyl)benzene (mCP) and 9,9'-(5-Bromo-1,3-phenylene)bis(9H-carbazole) (Br-mCP) in toluene solution. In the femtosecond transient absorption (fs-TA) spectroscopy of mCP, the excited state absorption (ESA) signal decreases at 630 nm while the triplet-triplet absorption (TTA) signal increases at 420 nm. Meanwhile, the isosbestic point observed at 455 nm indicates an intersystem crossing (ISC) lifetime of 15.4 ns. Moving on to the nanosecond transient absorption (ns-TA) spectroscopy, the TTA signal reaches its peak at 27.3 ns before decreasing, with the triplet lifetime of mCP measured at 2.8 μs. Br-mCP exhibits a similar dynamic evolution to mCP, but with a quicker ISC process (9.4 ns) and a longer triplet lifetime (3.9 μs). The quicker ISC process in Br-mCP is ascribed to the presence of heavy atom in the molecular structure, leading to an enhanced spin-orbit coupling constant (ξ(S₁, T₃)_Br-mCP = 1.371 cm⁻¹ > ξ(S₁, T₄)_mCP = 0.060 cm⁻¹). The prolonged triplet lifetime of Br-mCP (3.9 μs > 2.8 μs) results from its lower reorganization energy, effectively reducing non-radiative vibrational energy losses within the molecule. This work significantly enhances our understanding of RTP materials incorporating heavy atoms.

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来源期刊

Journal of Luminescence 物理-光学

CiteScore

6.70

自引率

13.90%

发文量

850

审稿时长

3.8 months

期刊介绍： The purpose of the Journal of Luminescence is to provide a means of communication between scientists in different disciplines who share a common interest in the electronic excited states of molecular, ionic and covalent systems, whether crystalline, amorphous, or liquid. We invite original papers and reviews on such subjects as: exciton and polariton dynamics, dynamics of localized excited states, energy and charge transport in ordered and disordered systems, radiative and non-radiative recombination, relaxation processes, vibronic interactions in electronic excited states, photochemistry in condensed systems, excited state resonance, double resonance, spin dynamics, selective excitation spectroscopy, hole burning, coherent processes in excited states, (e.g. coherent optical transients, photon echoes, transient gratings), multiphoton processes, optical bistability, photochromism, and new techniques for the study of excited states. This list is not intended to be exhaustive. Papers in the traditional areas of optical spectroscopy (absorption, MCD, luminescence, Raman scattering) are welcome. Papers on applications (phosphors, scintillators, electro- and cathodo-luminescence, radiography, bioimaging, solar energy, energy conversion, etc.) are also welcome if they present results of scientific, rather than only technological interest. However, papers containing purely theoretical results, not related to phenomena in the excited states, as well as papers using luminescence spectroscopy to perform routine analytical chemistry or biochemistry procedures, are outside the scope of the journal. Some exceptions will be possible at the discretion of the editors.