Water is the liquid of life. The structural, dynamic, and biological properties of water, aqueous systems and aqueous interfaces are essential in understanding the complexity of life, and our ability to harness its features for novel technologies. Research of the past decades has shown that liquid water is not the passive background against which biology unfolds, but rather an active participant and facilitator of biochemical processes that are responsible for life. Liquid water is a unique and dynamic system that continuously changes on a femtosecond timescale and sub-nanometer length scale. Unlike other liquids, and thanks to the quantum mechanical nature of the water molecule, these changes strongly contribute to the macroscopic properties of water. Understanding water thus involves the simultaneous access to multiple time and length scales.
It is our mission to obtain a better understanding of the active role that water plays in aqueous systems and in interfacial (biological) processes, by using and developing new methods (theory and instrumentation) that access the interfacial structure more accurately and probe multiple time and length scales simultaneously:
• Aqueous interfaces can be probed with better accuracy thanks to the development of a nanoparticle/droplet platform. Nanodroplets have a surface to volume ratio that is ~3-4 orders of magnitude larger than that of a planar interface. Thus, by using nano-interfaces we can dramatically increase the efficiency and accuracy of an interface measurement. Furthermore, preparation procedures can be done entirely in the bulk phase, and require a small sample volume. This allows for a dramatic reduction of impurity issues and reduces restrictions for a optical probes. In addition, apart from molecular level details it is also possible to simultaneously measure interfacial charge and structure.
• Probing aqueous droplet interfaces on different length scales requires methods that cover different length scales, such as linear and nonlinear light scattering measurements: dynamic light scattering (~mm/s), second harmonic scattering (nm,fs/ms), and vibrational sum frequency scattering (Å, ps). A large part of our research effort has been aimed at developing those methods. We have also developed the necessary nonlinear optical theories that allow us to access detailed molecular level information about interfacial processes.
Processes of current interest:
• • The unexplained charging of hydrophobic/aqueous interfaces
• • The formation and stabilization of amphiphilic aqueous interfaces
• • The formation and molecular properties of the electric double layer
• • Specific ion effects
We also aim to use our understanding of light-matter interaction, optical experiments and in particular the role of water to facilitate biotechnology.