Die DPG-Frühjahrstagung in Dresden musste abgesagt werden! Lesen Sie mehr ...

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

DY: Fachverband Dynamik und Statistische Physik

DY 62: Critical Phenomena and Phase Transitions

DY 62.3: Vortrag

Freitag, 20. März 2020, 10:00–10:15, ZEU 118

Exchange between two phases of confined water using deuteron two-dimensional exchange NMR — •Verena Fella and Michael Vogel — Institute for Condensed Matter Physics, TU Darmstadt, Germany

Understanding the properties of water in confinement is an important task due to its many applications in life science and technology. Nano-confinement reduces the crystallization temperature of water to lower values and enables supercooling to temperatures even below the nucleation temperature. Our previous studies [Yao et al., Langmuir (2019)], [Weigler et al., J. Phys. Chem. B (2019)] identified two dynamically distinguishable fractions of water coexisting within the pores at sufficiently low temperatures. These fractions correspond to a liquid interfacial water layer and a less mobile water phase in the pore center. We conjecture that highly distorted and unstable crystal nuclei exist under extreme confinement that exhibit reorientational dynamics with time scales intermediate to the confined liquid and to bulk ice. This leads to a complex and heterogeneous system inside the pores. One of the still open questions is the potential exchange between both water species and the time scales on which it occurs. Therefore we measure ²H two-dimensional NMR spectra of water in mesoporous silica materials. This method is well suited for heterogeneous systems because it directly probes exchange processes between fast and slow subensembles [Vogel, Rössler, J. Phys. Chem. A (1998)]. By varying the temperature and mixing time of the experiment we determine the time scale of these processes.