Nano-focused multimodal imaging, control, and interaction dynamics: ultrafast spectroscopy reaching the single molecule level

在这个由化学系化学测量和成像计划资助的项目中，科罗拉多大学博尔德分校的Markus Raschke教授和他的团队将超快光谱和相干控制扩展到纳米级。针尖上的飞秒等离子体纳聚焦将被用于研究非均匀环境中单量子系统(分子、量子点)的超快电子动力学。研究红外振动动力学和通过光学天线耦合控制红外光谱将把红外光谱推向均匀的样品大小和单分子极限。通过纳米尺度的近场泵浦探测及其对多维光谱的扩展，该小组将深入了解模型分子半导体、相分离聚合物以及与器件相关的体异质结材料薄膜中的纳米尺度电荷和能量转移。需要能够记录低于传统分辨率极限(~200 nm)的细节的成像方法来研究分子间耦合和形态之间的相互作用，这些相互作用通常决定着重要的天然和工程多组分分子和纳米材料的功能，例如半导体。在纳米尺度上对飞秒动力学的研究提供了对决定其结构、电荷和能量转移的机制的洞察。对纳米和分子间尺度的理解最终将允许对膜、聚合物或有机光伏系统等功能材料的系统设计以及对其性能的控制。这一高度跨学科的研究项目还为研究生和本科生提供了广阔的学习环境。作为这一努力的一部分，拉施克教授正在通过行业合作和国家实验室的用户设施，使开发的化学纳米光谱技术广泛应用。

In this project, funded by the Chemical Measurement and Imaging Program of the Chemistry Division, Professor Markus Raschke and his group at the University of Colorado at Boulder extend ultrafast spectroscopy and coherent control to the nanoscale. Femtosecond plasmonic nanofocusing on a tip will be used to investigate the ultrafast electron dynamics of single quantum systems (molecules, quantum dots) in non-homogeneous environments. Studying the infrared vibrational dynamics and control via optical antenna coupling will push IR spectroscopy to the homogeneous sample size and single molecule limit. Via the demonstration of nanoscale near-field pump-probe and its extension to multidimensional spectroscopy, the group will gain insight into nano-scale charge and energy transfer in thin films of model molecular semiconductors, phase segregated polymers, and device relevant bulk heterojunction materials.Imaging methods that can record details below the conventional resolution limit (~200 nm) are needed to study the interplay between intermolecular coupling and morphology that often dictates the function of important natural and engineered multi-component molecular and nano-materials, such as semiconductors. The investigation of the femtosecond dynamics on nanometer length scales provides insight into the mechanisms that determine their structure, charge-, and energy-transfer. That understanding on the nano- and intermolecular scale will ultimately allow for the systematic design of functional materials such as membranes, polymers, or organic photovoltaic systems as well as control of their performance. This highly interdisciplinary research program also provides a broad learning environment for graduate and undergraduate students. As part of this effort, the Prof. Raschke is making the chemical nano-spectroscopy techniques developed broadly available through industry collaborations and at user facilities at National Labs.