Research Team of Dominik Heger

 

Welcome at our website!

We are a research group specializing in photophysics and photochemistry of compounds in ice matrices. We aim to combine the knowledge of pharmaceutical sciences and environmental sciences to shine a light on the freezing process and its implication for compounds within the frozen solution!

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Our Most Recent Publications

Jan Zezula and David Mužík, led by Dominik Heger, collaborated with the Austrian group of Thomas Loerting to study the fluorescence behavior of 1-methylnaphthalene in the temperature range of 77-295 K. They discovered that the crystalline, glassy, and liquid states of 1-methylnaphthalene could be distinguished using fluorescence spectroscopy.

The authors found that the main distinguishing feature is the presence of excimer emission in the fluorescence spectra. Crystals do not show excimer fluorescence at temperatures below 190 K, unlike glass. The study also proposed the existence of a quasi-liquid layer on the surface of 1-methylnaphthalene crystals, characterized by excimer emission. This existence became apparent 40 K below the melting point.

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Susrisweta Behera, Radim Štůsek, and Lukáš Veselý, led by Dominik Heger, collaborated with the Austrian group of Thomas Loerting to conduct a comprehensive study of the behaviour of citrate buffer during freezing. The study revealed that one of the most commonly used citrate buffers becomes more acidic when frozen. Interestingly, the acidification is more pronounced at lower concentrations, while it is negligible at higher concentrations.

The authors conducted a calorimetric study and optical microscopy, correlating the results with the acidities obtained by spectroscopy. The study revealed that citrate buffer can crystallize, which challenges a long-standing paradigm in the pharmaceutical field. Additionally, the measured acidities demonstrate that citrate buffer significantly acidifies, which was previously unexpected.

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Lukáš Veselý and Radim Štůsek performed this study in cooperation with the A-ESEM microscopy group of the Czech Academy of Sciences. They were able to successfully connect microscopic images with spectroscopic data, which led to the first ever demonstration that the inner structure of the freeze-concentrated solution (as shown on the right) has a major influence on aggregation during freezing.


In this work the authors challaged a long standing theory, which assumed that the size of the ice crystals is the most important factor influencing the aggregation after freezing! This would not be possilble without close long-term collaboration of our research group with the ESEM group lead by Vilém Neděla.

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The study was led by Dominik Heger in collaboration with the A-ESEM microscopy group of the Czech Academy of Sciences. The work focuses on the small (micrometre-sized) salt particles produced during ice sublimation. These particles are thought to facilitate photochemical reactions in polar regions.

In this paper, the authors show the surprising result that high-salinity ice requires temperatures of -30°C to produce particles small enough to form reactive aerosols. In contrast, in low-salinity ice, particles are produced at all sub-zero temperatures. This unique paper is the first to quantify the particle sizes produced by ice sublimation.

The importance of the article is immediately apparent as it has been chosen as the cover of the 8th issue of the 49th volume of Geophysical Research Letters.

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Radim Štůsek and Lukáš Veselý performed a laboratory study of artificial seawater freezing. This was a topic of Radim’s bachelor thesis, and its results were finally published in impacted journal Science of the Total Environment. The authors discovered that the acidity of freeze-concentrated solution increases with decreasing temperature of the ice.

The samples of seawater were chosen to reflect natural conditions of seawater (3.5 % of salt weight and pH 8), frost flowers, and salty snow. The study focused on the investigation of acidity of the brine inside the ice vein (depicted in the abstract in the magnification on the right). The acidity was measured by the acid-base indicator present inside the ice veins. The study concluded that with decreasing temperature, the acidity of the brine increases above values that allow for efficient acid-base catalysis.

These results can explain the enhanced reactivity in the polar regions, both polluted by human-made chemicals and untouched pristine regions. The former was explained by scavenging of anthropogenic acids, however the latter remained as a mystery. This study finally cracked this mystery and proved that the sea ice can become acidic just by freezing by a completely natural mechanism. These results show that the anthropogenic acids are not necessary to facilitate the enhanced reactivity.

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News

July 2024: Marie Garncarzová and Radim Štůsek started their PhD studies in our lab.  

June 2024:Marie Garncarzová and Radim Štůsek have successfully completed their master's studies. Congratulation!

June 2024: Radim Štůsek and Lukáš Veselý were awarded the prize of Head of the Department of Chemistry. Congratulations!

February 2024: David Mužík started his PhD in our lab. 

February 2024: David Mužík successfully defended his master's thesis. Congratulation!

January 2024: Congratulations to Susrisweta for successfully defending her thesis. Good luck in your future life, Dr. Behera!

Contacts

Dominik Heger - Head of the team

Email: hegerd@chemi.muni.cz
Phone: : +420 549 493 322

Team members Address

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