• Interfacial Chemistry for the Environment

Understanding the role of aerosols in climate change is an important scientific challenge that is critical to accurately predict the environmental impact of future energy technology options, atmospheric chemistry, and human health. Although aerosols are important in a wide range of scientific disciplines, there is much that remains to be understood, particularly their surface properties and influences on atmospherically relevant reactions. Many physical and chemical processes at aerosol surfaces have been appreciated theoretically and conjectured experimentally. We thus explore the novel coupling of surface-selective nonlinear spectroscopy to various problems related to aerosol surfaces. The topic is to understand the physical and chemical properties at aerosol surfaces that are of key relevance to cloud formation and global climate change. There are many fundamental scientific questions to be addressed. Can aerosol particle surfaces serve as efficient media for photochemical processes? Can photochemical reactions be made faster on particle surfaces? How do these surface reactions affect cloud condensation properties of aerosol particles?

  • Interfacial Charge Transfer and Charge Transport for Energy Conversion

Harvesting solar energy is one of the most promising approaches to solve current energy requirements. Organic-based solar cells (OSCs) show great promise to meet the urgent requirements for low-cost, clean, and renewable energy managements. . However, further improvements of efficiencies are needed to make OSCs commercially viable. Numerous methods of increasing the conversion efficiency have been investigated including the usage of different donors and acceptors, the introduction of buffer layers between the anode and active layer. Of them, the charge transfer at donor/acceptor interfaces in the OSCs is the most crucial process that affects the power conversion efficiency. Many important questions remain unresolved regarding the interfacial processes in the OSCs. We employ and develop an emerging interface-specific technique, ultrafast sum frequency generation (SFG) spectroscopy. This is a very unique technique for studying interfacial structure and dynamics of OSCs, which is distinct from traditional ultrafast nonlinear spectroscopy for bulk. A prominent advantage of the SFG technique over other surface techniques is its ability to probe all types of boundaries, including various combinations of gas, liquid, and solid interfaces.