Ultrafast photochemical processes in nanomaterials and their interfaces for electronic and biomedical applications

Presenter: Elham Ghadiri, Assistant Professor, Chemistry Department, Wake Forest University

Ultrafast photochemical processes such as photoinduced electron transfer across molecular/bulk interfaces of different organic-inorganic materials have gained attention only recently and are still poorly understood. These interfaces offer an excellent case study relevant to a variety of photoelectrochemical systems, photovoltaic, molecular electronics, analytical detection, photography, and quantum confinement devices. In energy conversion systems, photochemical processes happen in time frames of femtoseconds to milliseconds. For example, in the dye-sensitized solar cells (DSCs), a kinetic competition of charge carrier processes, namely electron injection, dye regeneration by electrolyte, unwanted back recombinations, and electron/hole transport processes (happening within dye molecules, redox electrolyte, hole transport material, catalyst, and their interfaces) control the final performance of the device. Time-resolved laser spectroscopy techniques, such as pump-probe transient absorption, have been applied to study such processes. Our research deals with the fabrication of nanomaterials and nanomaterials-based heterojunctions with controlled interfaces for target applications in energy conversion and biomedical devices. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test. We integrate ultrafast laser spectroscopy and ultrafast laser microscopy techniques to study the photochemical processes at such interfaces. Such a fundamental understanding of the interfaces would help to design and improve the performance of the materials.

Dr. Elham Ghadiri is an assistant professor in the Chemistry department at Wake Forest University. She obtained a Ph.D. degree in Nanoscience and Nanotechnology from the Institute for Nanoscience of the Sharif University of Technology in 2010. After obtaining her Ph.D., she joined the group of Jacques Moser and Michael Grätzel to perform research in the field of ultrafast laser spectroscopy science and technologies and obtained a second Ph.D. degree in Chemistry (December 2014). She developed the first femtosecond time-resolved pump-probe diffuse reflectance spectrometer capable of measuring any opaque system. She performed her post-doctoral research in the group of Warren S. Warren, a pioneer in biomedical imaging to integrate the spectroscopy technique she developed with the ultrafast microscopy techniques developed at Warren’s group, to the study of opaque biological systems, namely photochemistry of tissue for early cancer diagnosis. She received the 2017 WFIRM-TERMIS International Society Young Investigator Award at the annual TERMIS AM meeting.