This fascinating picture was taken with a confocal laser scanning microscope LSM 710 (Zeiss, Germany) in the laboratory of the International Research and Educational Center for Physics of Nanostructures. The image was obtained by combining two micrographs. One is made in the laser light passing through the sample, and the second is its luminescent image.

The branching structures shown on the picture are dendrites of luminescent semiconductor nanocrystals – quantum dots resulting from self-organization under controlled solvent evaporation. 

To obtain such structures, a drop of quantum dot solution is applied to a glass slide and dried in a desiccator. The type of the observed structures is completely determined by the parameters (acidity, concentration, and type of stabilizer) of the solution and the drying conditions.

After complete evaporation of the solvent (in this case, water), the study of the sample continues with an LSM 710 confocal microscope. Due to their branching structure dendrites are able to collect, transport, and concentrate light, which makes them a prospective system for collecting solar energy.

As part of the research, scientists are exploring the relationship between synthesis conditions, spectral features, and the structural properties of synthesized dendrites. The principles of fractal geometry are used to study them.

Photo courtesy of Olga Kushchenko and Lubov Borodina
Photo courtesy of Olga Kushchenko and Lubov Borodina

Now, a theorist group of the International Research and Educational Center for Physics of Nanostructures laboratory is engaged in this task. The study aims to comprehensively study dendrites and create dendritic structures with fully controllable properties for large-scale production of solar cells. Students of the Physics and Technology of Nanostructures program are also taking part in the work.

Furthermore, the experiment made it possible to capture many beautiful pictures. One of them is currently exhibited at the ZEISS Russia & CIS Perspectives competition.

The results obtained in the course of this work were presented in December 2019 at the 2nd International School-Conference Smart Nanosystems for Life and published in the article Fractal Properties of CdTe Quantum Dots Dendrites (Kushchenko O.M., Rudyi S.S., Borodina L.N., Cherevkov S.A., Rozhdestvensky Y.V. //Optics and spectroscopy, 2020, Vol. 128, No. 8, pp. 1190).