Development of ultrafast broadband UV-Vis circular dichroism spectroscopy for investigating the photoinduced dynamics of chiral molecular systems

开发超快宽带紫外-可见圆二色光谱用于研究手性分子系统的光致动力学

• 批准号: 313529255
• 负责人: Professor Dr. Thomas Lenzer
• 金额: --
• 依托单位: Arbeitsgruppe Physikalische Chemie II
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/313529255?language=en
• 关键词: Development; ultrafast; broadband; UV; Vis

Transient circular dichroism (TrCD) spectroscopy is a promising method for tracking the transient evolution of photoexcited chiral systems. This is made possible by monitoring the difference in the photoinduced changes of absorption between left and right circularly polarized light. In the first funding period of this project, we established a setup for ultrafast TrCD spectroscopy covering the wavelength range 260-700 nm with a time resolution of 170-200 fs. It was successfully applied to obtain new information regarding the photoinduced dynamics and the coherent spectroscopy of chiral polymer thin films. In this renewal proposal, we would like to improve the sensitivity of the existing UV-Vis TrCD setup considerably by employing two new technical developments: (1) an advanced Pockels-cell-based design and (2) an alternative design involving a photoelastic modulator. Both approaches will improve the time resolution of the setup to ca. 90 fs and the present signal-to-noise ratio by at least a factor of ten. These new setups for TrCD spectroscopy will then be applied to elucidate the dynamics of three classes of chiral systems: (1) the electronic and structural dynamics of photoexcited cholesteric fluorene- and carbazole-based copolymer arrangements showing either large intrinsic chirality or giant chiral induction, (2) the transient CD response of helicene-type molecules and thin films in the excited electronic state and (3) the dynamics of chiral perovskite-inspired semiconductors upon photoexcitation to the conduction band. Measurements employing ultrafast broadband UV-Vis-NIR transient absorption will complement the studies using TrCD spectroscopy. The experiments will be analyzed by sophisticated global kinetic analysis techniques and calculations based on density functional theory. We are convinced that these advanced setups for ultrafast transient CD spectroscopy will be applicable to probing the structural and electronic dynamics of various chiral systems.

瞬态圆二色性（TrCD）光谱是跟踪光激发手性系统瞬态演化的一种有前景的方法。这是通过监测左右圆偏振光之间光致吸收变化的差异来实现的。在该项目的第一个资助期间，我们建立了超快 TrCD 光谱仪，覆盖波长范围 260-700 nm，时间分辨率为 170-200 fs。它已成功应用于获得有关手性聚合物薄膜的光致动力学和相干光谱的新信息。在这个更新提案中，我们希望通过采用两项新技术开发来显着提高现有紫外-可见光 TrCD 设置的灵敏度：(1) 先进的基于普克尔斯盒的设计和 (2) 涉及光弹性调制器的替代设计。两种方法都将设置的时间分辨率提高到大约。 90 fs 和当前信噪比至少提高了十倍。这些 TrCD 光谱的新装置将用于阐明三类手性系统的动力学：(1) 光激发胆甾型芴基和咔唑基共聚物排列的电子和结构动力学，显示出大的本征手性或巨大的手性感应，(2) 螺旋烯型分子和薄膜在激发电子态下的瞬态 CD 响应 (3) 手性钙钛矿半导体在光激发至导带时的动力学。采用超快宽带紫外-可见-近红外瞬态吸收的测量将补充使用 TrCD 光谱的研究。实验将通过复杂的全局动力学分析技术和基于密度泛函理论的计算进行分析。我们相信，这些用于超快瞬态圆二色光谱的先进装置将适用于探测各种手性系统的结构和电子动力学。