Research Highlights

We develop novel optical technology, geared to obtaining molecular level details of nanoscale and microscopic systems in aqueous environments as well as other complex 3D environments such as pores. We have focused on ultrafast nonlinear optical methods as they are non-invasive and label-free and inherently interface specific or sensitive to polar structures. We apply these tools to fundamental questions that have important implications for biology, chemistry or technology. 
 
 Topics of interest:
 • Water, aqueous solutions
 • Aqueous interfaces and nanoscopic systems
 • Nonlinear optics, ultrafast spectroscopy, light scattering
 • Multiphoton imaging
 • Soft systems: Interfaces, membranes, electric double layers
 • Structure and dynamics in living systems
 • Neuroimaging and neurological activity
 
 10 Research Highlights (anti-chronological)
 
 • Surface electrostatic potentials and reaction constants can be optically imaged in real time and display heterogeneities of respectively a factor of 3 x the average and 8 orders of magnitude on a glass micro-capillary surface immersed in water. 
 • Electrolytes induce changes in the hydrogen bond network of water that range over ~77 hydration shells and are subject to quantum effects. These changes lead to energy changes on the order of kT per ion, which lead to surface tension anomalies, better known as the controversial Jones-Ray effect (discovered in the 1930’s).
 • Discovery that (~50-150 nm) liposomes exhibit trans-membrane asymmetry in their hydration shells rather than the lipid composition. Specific interactions may induce membrane asymmetry. 
 • Development of a nanodroplet platform to study the molecular structure of lipid droplets and biological monolayer phenomena in solution.
 • Discovery that various molecular properties of nanoscale / submicron droplets of oil and water behave differently than extended planar interfaces composed of the same chemicals; reasons can be found in the difference in hydrogen bond network configurations and a different balance of electrostatic interactions.
 • Development of wide field medium repetition rate second harmonic and multiphoton imaging instruments with ~5000 x better efficiency than scanning confocal microscopy.
 • Angle resolved second harmonic scattering can be used to measure unique surface potential values on particles in solution.
 • Development of second harmonic scattering instrumentation with an improved efficiency of ~1000. 
 • Invention of vibrational sum frequency scattering, and subsequent development into a reliable interfacial molecular probe of buried interfaces of nano- and microscale materials.
 • Development of nonlinear optical theories to understand nonlinear light scattering.