Probing Structure and Dynamics at Interfaces with Ultrafast Nonlinear Spectroscopy
Interfaces play an important role in a variety of intriguing charge transfer process relevant to biology, catalysis, environmental chemistry and molecular electronics. Fundamental information about the molecules at interfaces is limited as many spectroscopic methods are not able to specifically detect the buried interface between two condensed phases. A primary goal of my research is to use the tools of ultrafast nonlinear spectroscopy to provide a comprehensive picture of interfacial structure and dynamics. My research group will design and implement novel spectroscopies capable of selectively probing buried interfaces in situ and provide molecular level structural information such as the presence of various chemical moieties, quantitative molecular functional group orientation, and time-dependent kinetics and dynamics at interfaces.
Charge transfer at Organic Heterojunction Interfaces
Organic semiconductors (OSCs) constitute an attractive platform for optoelectronics design due to the ease of their processability and chemically tunable properties. However, employing OSCs as active electronic components remain challenging as this involves forming junctions between OSCs and other materials. Such junctions can distort the OSC’s electronic properties, complicating the transfer of energy and charge across them. To better understand the electronic structure of interfacial OSC molecules, our group will employ interface-selective electronic sum frequency generation technique, which selectively probes interfaces of thin films where a breakage of symmetry occurs.
Proteins at Interfaces
Many important biological phenomena occur at interfaces and most proteins attain their biological activities through specific interactions at interfaces. Despite the apparent importance, a molecular picture of how, and to what extent, surfaces and proteins influence each other’s structure still lacking due to the lack of experimental probes that can uniquely investigate the interfacial interaction between the protein and crystal. In order to understand the details of protein interactions that take place on surfaces, our group proposes to use an interface-specific femtosecond nonlinear spectroscopy technique to understand the mode of action by which surface active proteins interact and manipulate interfaces.
Interfacial Structure of Room-Temperature Ionic Liquids
Many applications of ionic liquids (ILs) involve interfacial effects such as electrochemistry, fuel cells, organic field-effect transistors, lubrication, heterogeneous catalysis, energy materials and propellants. Understanding of the structure of ILs at the phase boundary, therefore, can lead to structure -property relations and is a prerequisite to a knowledge-based design of a suitable ILs for a given application. Despite the immense commercial potential, developing a framework for how the molecular-level interactions between the individual units that comprise these materials act to give rise to their macroscopic properties remains a strong challenge for scientists. Understanding the structure and dynamics of ILs at interfaces will enable us to develop molecular design rules for controlling interfacial ILs behaviour.