Research Activities

We are a group of physical chemists that try to understand the photophysical and photochemical processes not only on ice surfaces.

Photophysics and Photochemistry examines interation of matter and light. After a molecule has been excited by light to a higher electronic state, it either relaxes or react. There are numerous chemical reactions initiated by, which are studied by photochemistry, and potentially photophysics. The knowledge obtained during these studies is then used in various directions and applications, such as:

Study of Organic and Inorganic Impurities in/on Ice

We study organics and inorganics by spectroscopy of frozen solutions. We employ integrating sphere for this purpose to collect all of the scattered light. Our research focuses on the freezing-induced acidity changes of frozen seawater and inorganic salts, changes in aggregation during freezing and acidity changes connected to Workman-Reynolds.

We also study the changes in spectral characteristics of organics in and on ice. For example we have shown that absorption spectra greatly change when the compound is depositied on the ice surface or frozen inside the freeze-concentrated solution.

Study of Freezing and Lyophilization with Implications for Pharmaceutical Sciences

We study the fundamental processes of freezing and, by extention, lyophilization. These methods are widely used in pharmaceutical and food sciences. To study freezing we apply microscopy and spectroscopy and try to connect these two very different datasets.

Our research presents a unique look on the pharmaceutially important processes from a physical chemist's perspective. For example, we have shown that the structure of ice inside the freeze-concentrated solution is more important for the behavior of compounds that reside inside it than the structure of large primary ice crystals.

Ice and snow, the solid forms of water, are very interesting reaction media. The impurities that can partake in chemical reactions get on/in the ice by two paths - freezing of solution with impurities and deponation of impurities on the ice surface. In the former case we form a "freeze-concentrated solution" distributed between the ice crystals. This means that by freezing of solution we literaly concentrate our impurities because a large portion of the water precipitates as water. In the latter case we are stacking molecules on the surface of the ice, which is much more controlable process.

Organic compounds, for instance, are commonly found in the freeze-concentrated solution in nature and, due to interesting conditions therein, they can undergo a plethora of reactions. We study the compounds in these pockets of freeze-concentrated solution by absorption and emission of light, electrone microscopy, and possibly reactivity. These pockets differ from the original solution: the concentration of impurities increases 1000-fold or more, and the acidity of the solution changes as well. These effects strongly affect protonation of organic and inorganic compounds, their aggregation and stability. By our spectral methods we can observe spectral changes inside of the frozen solution and on the surface of the ice.

There is an interesting effect connected to freezing, it was named after its discoverers: Workman-Reynolds effect. Some ions are able to incorporate inside the ice crystal, which makes it changed and therefore creates a potential between the ice and the surrounding solution. This potential is the countered by the current of protons/hydroxyl ions into the ice. This depletion of protons/hydroxyl ions from the solution leads a rather mild pH change, which can be in some cases very significant. We study this effect by measuring the potential and its implications by measuring the pH change inside the frozen solution.

During our research we have observed all of the above phenomena and started to apply our knowledge in the field of pharmaceutical science. Freezing is the first step of lyophilization (freeze-drying) and most of the pharmaceuticals have been frozen at least once. Most of the medications that each of us takes has undergone some freezing, which is supposed to stabilize it and icrease its shelf-life. However, if done incorrectly, it can degrade the active pharmaceutical igredients or alter their funcionability. It is therefore vital to understand these effects in order to produce safe medications without loses on storage and stabilization.

Study of Photochemistry and Photophysics

We study the photophysics and photochemistry of various processes. Usually we apply fluorescence measurements, nano- and femtosecond spectroscopy and other mesessary methods.

These studies are quite complex and often very challenging, they require a cooperation of multiple groups and methods. Currently we study 1-MethylNaphtalene and its photophysics after excitation in nanosecond and picosecond timescales to uncover the mechanisms that govern its deexcitation and relaxation.

Some processes in chemistry, and especially photochemistry, are too rapid to be observable by our usual methods. Measurements on spectrophotometers are usually performed on second-milisecond scales, fluorescence measurements can be performed on microsecond scales, however such experiments may not be sufficient in some cases. For this purpose we apply nano- and femtosecond time-resolved spectroscopy to resolve some rapid processes that occur after the excitation of molecules.

These studies can help us to discover photochemical mechanisms and determine the rate constants. This can be very useful in a number of scientific disciplines. Interaction of light with matter is important for biology (photosynthesis), engineering (solar panels) and chemistry (photochemical reactions). Study of these mechanism of light emission and changes in molecular structure and behaviour after excitation are fundamental and their aplications are innumerable.

Study of Actinometry

We study the effeciency of radiative processes by our actinometric setup. In this regard, we determine the quantum yields of fluorescence, phosphorescence and other processes.

This method is usually ancillary to other methods, but it is essential for correct modelling and calculating the efficiency and yields of photochemical reactions.

The results obtained from spectroscopic studies are often difficult to interpret due to various interfering processes. To ensure accuracy, methods such as actinometry are employed to check lamp stability and measure quantum yields. Although the term 'quantum yields' may sound intimidating, it simply refers to the number of processes per absorbed photon.

Actinometers are compounds that have a known quantum yield of a detectable process, such as fluorescence or phosphorescence. In previous studies, 2-nitrobenzaldehyde was investigated as a potential actinometer, and its viability was confirmed using efficient ferrioxalate.