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T. Häusler, L. Felgitsch, E. Khaybulina, H. Grothe:
"Cellulose and Their Characteristic Ice Nucleation Activity- Freezing on a Chip";
Vortrag: 16. Österreichische Chemietage 2015, Innsbruck; 21.09.2015 - 24.09.2015; in: "GÖCH 2015", (2015).

Clouds are essential for Earth´s climate system, weather phenomena, and hydrological cycle.[1] Their microphysics determine for example cloud lifetime and precipitation properties. Furthermore clouds have a twofold impact, they can cool the climate system by reflecting incoming solar radiation and can warm its surface by trapping outgoing infrared radiation.[2] In the atmosphere ice crystals form through heterogeneous and homogeneous ice nucleation. For homogeneous nucleation, a temperature below -38°C is needed. Freezing processes at higher temperatures occur heterogeneously.[3] In the latter case, an aerosol particle acts like an catalyst, which reduces the energy barrier for nucleation. The nucleation mechanisms, especially the theory of functional sites are not entirely understood. It remains unclear which class of compound nucleates ice.
Here, we present proxies for biological macromolecular substances, microcrystalline cellulose and cellulose nano fibers. Cellulose is the main component of herbal cell walls (about 50 wt%). It is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose can contribute to the diverse spectrum of ice nucleation particles.
Immersion freezing experiments with a self-made reaction gadget were carried out. In this device a water-cellulose suspension was cooled till the freezing point and observed via a light microscope. Based on the evaluation of the microscope records, different INA due to the particle size and concentration of cellulose in the suspension were investigated. Further analysis methods as SEM, and ATR-IR were carried out to completely describe the cellulose and their ice nucleation activity.
[1] IPCC, 2013: Summary for Policymakers. In: Climate Change 2013 Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1-30, doi:10.1017/CBO9781107415324.004.
[2] Baker, M. B.; Peter, T., Small-scale cloud processes and climate. Nature 2008, 451 (7176), 299-300.
[3] Pruppacher, H.; Klett, G., Microphysics of Clouds and Precipitation. Kluwer Academic Publisher: Amsterdam: 1997.

ice, nucleation, cellulose

http://publik.tuwien.ac.at/files/PubDat_243139.doc