Sharon BerkowiczPhD student
With a background in both physical (spectroscopy in particular) and organic chemistry, I am driven by curiosity to understand the relations between molecular structure and functional properties - from chemical reactivity and interactions to photophysical as well as structural dynamics. Following internships at the Catalysis, Green Chemistry and Renewable Energy Lab at Weizmann Institute of Science (Israel) and the Laboratory of Ultrafast Spectroscopy at EPFL (Switzerland), I first joined the Chemical Physics division at Stockholm University for my Master Thesis in 2019, where I worked with femtosecond lasers to investigate the steering of photochemical reactions by intense light.
Later on, in 2019, I joined as a PhD student in the group of Structural Dynamics of Aqeuous Solutions (SDAQS) led by Foivos Perakis. My current work as a PhD student is focused on studying the structural dynamics in supercooled water and aqueous solutions at the molecular level, in order to gain insight into the unique and fundamental properties of water as the essential solvent for life. To explore structural dynamic solution phenomena, such as diffusive dynamics and nanoscale fluctuations, I utilize in particular light- and X-ray scattering techniques, including dynamic light scattering and X-ray photon correlation spectroscopy at synchrotons and X-ray free-electron lasers.
A selection from Stockholm University publication database
Exploring the validity of the Stokes-Einstein relation in supercooled water using nanomolecular probes
2021. Sharon Berkowicz, Fivos Perakis. Physical Chemistry, Chemical Physics - PCCP 23 (45), 25490-25499Article
The breakdown of Stokes–Einstein relation in liquid water is one of the many anomalies that take place upon cooling and indicates the decoupling of diffusion and viscosity. It is hypothesized that these anomalies manifest due to the appearance of nanometer-scale spatial fluctuations, which become increasingly pronounced in the supercooled regime. Here, we explore the validity of the Stokes–Einstein relation in supercooled water using nanomolecular probes. We capture the diffusive dynamics of the probes using dynamic light scattering and target dynamics at different length scales by varying the probe size, from ≈100 nm silica spheres to molecular-sized polyhydroxylated fullerenes (≈1 nm). We find that all the studied probes, independent of size, display similar diffusive dynamics with an Arrhenius activation energy of ≈23 kJ mol−1. Analysis of the diffusion coefficient further indicates that the probes, independent of their size, experience similar dynamic environment, which coincides with the macroscopic viscosity, while single water molecules effectively experience a comparatively lower viscosity. Finally, we conclude that our results indicate that the Stokes–Einstein relation is preserved for diffusion of probes in supercooled water T ≥ 260 K with size as small as ≈1 nm.