In this award, funded by the Experimental Physical Chemistry Program of the Division of Chemistry, Professor Markus Raschke and his group at the University of Washington are studying fundamental questions about the electron and vibration dynamics of nanoconfined systems. To achieve simultaneous ultrahigh temporal and nanometer spatial resolution, Professor Raschke and his group combine femtosecond time resolved spectroscopy with optical near-field microscopy techniques. The local optical field enhancement of scanning probe tips provide the necessary spatial field confinement. The proposed work includes probing the electron dynamics in individual plasmonic nanocrystals to provide insight into the time scale and efficiency of different relaxation channels and their correlation with structural parameter. In addition the study of vibrational dynamics will allow to distinguish spatial and temporal decoherence in molecular nanostructures. This interdisciplinary research program with its combination of optical spectroscopy, scanning probe techniques, and material science, provides a broad learning environment for graduate and undergraduate students. In addition to laboratory research, this award supports the development of a new nanooptics and spectroscopy graduate course and of nanoscience modules for the undergraduate curriculum in physical chemistry.
The examination of the femtosecond dynamics on the mesoscopic length scale (1 -100 nm) contributes to a fundamental understanding of the underlying optical excitations that is necessary for the targeted design of functional optical materials, for the production of nanophotonic devices, for improved understanding of signal transduction, and for improved methods of molecular sensing. The educational aspects of this award provide integrated open source teaching materials, course readers, free online encyclopedia entries, and a summer internship for students from educationally disadvantaged schools districts in Seattle.
Many real world materials such as biological, catalytic, energy, or photonics gain their functional properties from interactions of their molecular or nano-scopic building blocks. Understanding the structure of these materials and how it related to their function, and ultimately controlling their properties requires new microscopic imaging techniques that provide chemical insight with few nanometer spatial resolution. In this project we have developed and applied new ultra-microscopy techniques that can imagine materials with a sensitivity as high as single molecules or single quantum objects. This goal has been enabled by the combination of several interdisciplinary concepts, such as engineering the transduction of light into the nanoscale through the help of scanning probe tips acting as optical antennas, scanning probe microscopy to achieve the nanometer precise control of the tip-sample position and for lateral imaging, and advanced sensitive spectroscopy and optical signal detection schemes. We have demonstrated the unique performance and applicability of the approach to the understanding of plasmonic particles for their use for enhanced optical molecular sensors. Using infrared nano-spectroscopic imaging we were able to determine the mechanisms of intermolecular coupling in polymer heterostructures as the basis for their properties to charge and energy transfer. And in combination with ultrafast laser pulses this furthermore allowed to watch the underlying dynamics of electron and vibrational atomic motion in real time, aiding in the understanding of the most fundamental processes that determine the relationship between structure and function in advanced materials.
