Ultrafast Phenomena Laboratory (UPL)

We study photophysical properties of new photoactive materials, such as photosensitizers used in the so-called photodynamic therapy using stationary and time-resolved spectroscopic techniques. By analyzing the interaction of these materials with light and examining the influence of their environment on their photophysics, we can contribute to the optimization of the properties of novel materials.

Intense ultrasonic waves propagating through a liquid create rapidly collapsing microbubbles (cavitation bubbles) with temperatures reaching thousands of Kelvin. This results in chemical reactions in the hot bubble environment (so-called sonochemical reactions) and the formation of new molecules. This phenomenon can be used to synthesize new materials, and by analyzing the light emitted from the bubbles, conclusions can be drawn about the processes taking place during the ultrasound-induced reaction. Using stationary and time-resolved spectroscopy, we try to study sonochemical processes and use them to produce photoactive materials.

The formation and breaking of chemical bonds or structural changes in chemical molecules take place in times much shorter than 1 picosecond. The study of such fast phenomena is possible only thanks to the use of ultrashort (femtosecond) pulses of laser light: one pulse can initiate the process under study and another, delayed with respect to the first one by a given time, monitors its course. Using this scheme, we study the dynamics of elementary chemical reactions, e.g. involving the transfer of a hydrogen atom, which allows, among others, verification of quantum models used to describe them.

Until recently, light has rarely been considered in the context of diagnostic methods that can be used for imaging tissues in a form other than microscopic sections. The reason for this is the strong scattering of light by the tissues and the low sensitivity of light to changes in the tissues occurring at the microscopic level. This situation is changing now, thanks to the development of techniques for focusing light inside scattering media such as tissue, and application of methods based on non-linear (multi-photon) light absorption and the process of stimulated emission. Using the properties of ultrashort light pulses, we develop methods of detecting pathogenic proteins in tissues, based, for example, on the generation of laser light inside the tissue excited in a two-photon absorption process.