Eisenthal Group

We study equilibrium and dynamical properties of molecules at liquid interfaces. Many important chemical processes occur at liquid interfaces. Examples include cell membranes which host a variety of vital reactions in biology and life science, air/water interface (environmental importance), solid/liquid and liquid/liquid interfaces in catalysis and electrochemistry, surfaces of self-organized structures such as phospholipid bilayers, liposomes, micelles and surfaces of colloids and microparticles.

Experiments performed in our lab are a unique combination of ultrafast (femtosecond) and surface selective capabilities. We use nonlinear optical spectroscopies to selectively probe molecules in the very thin interfacial region (~10Å). The second order nonlinear optical process of Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG) are symmetry-forbidden in bulk media, but allowed at interfaces. In our experiments we use femtosecond lasers to perform ultrafast time-resolved measurements. This allows us to observe motions and reactions of molecules at interfaces in real time. Our current time resolution is ~140fs.

Static molecular properties at liquid interfaces that have been characterized in our group:

*pK of acids and bases

*Orientation of adsorbed molecules

*Electronic spectra

*Polarity

*Surface potential of charged interfaces

*Surface properties of microscopic particles: liposomes, semiconductor colloids, clays, polymer beads and emulsions

*Biomembrane surfaces

Dynamical molecular processes at interfaces that have been characterized in our group:

*Intermolecular energy transfer

*Orientational relaxation

*Photoisomerization

*Solvation dynamics