Daria A. Zazymkina

The development of layered semiconductor doping and functionalization techniques is important for van der Waals heterostructure applications. Rare-earth impurities are of interest due to their ability to modify the optical, magnetic, and conductive properties of the semiconductor matrix. In this study, Tm-doped SnS2 powders (SnS2:Tm) with optically active rare-earth centers were synthesized under pressures up to 8–9 GPa and temperatures up to 1600 °C. The synthesized powders consisted of platy particles containing Sn, S, and Tm. Powder X-ray diffraction and Raman spectroscopy confirmed the crystallization of SnS2:Tm with lattice parameters and phonon modes close to those of undoped hexagonal SnS2. Photoluminescent measurements of SnS2:Tm exfoliated flakes revealed sharp emission lines from intra-center transitions 3F2,3 → 3H6 and 3H4 → 3H6 of Tm3+. The Stark splitting of these luminescence lines reflects the local D3d crystal-field environment of Tm3+ ions. The results obtained demonstrate that 2H-transition metal dichalcogenide lattices can serve as a matrix for rare-earth ions, combining a wide variety of structural and electrical properties of 2D materials with well-studied optical transitions in lanthanide ions.

The development of new strategies for the mass synthesis of SiC nanocrystals with high structure perfection and narrow particle size distribution remains in demand for high-tech applications. In this work, the size-controllable synthesis of the SiC 3C polytype, free of sp² carbon, with high structure quality nanocrystals, was realized for the first time by the pyrolysis of organosilane C₁₂H₃₆Si₆ at 8 GPa and temperatures up to 2000 °C. It is shown that the average particle size can be monotonically changed from ~2 nm to ~500 nm by increasing the synthesis temperature from 800 °C to 1400 °C. At higher temperatures, further enlargement of the crystals is impeded, which is consistent with the recrystallization mechanism driven by a decrease in the surface energy of the particles. The optical properties investigated by IR transmission spectroscopy, Raman scattering, and low-temperature photoluminescence provided information about the concentration and distribution of carriers in nanoparticles, as well as the dominant type of internal point defects. It is shown that changing the growth modes in combination with heat treatment enables control over not only the average crystal size, but also the LO phonon—plasmon coupled modes in the crystals, which is of interest for applications related to IR photonics.

A novel, successful method of bactericidal treatment of pathogenic bacterial biofilms in vitro by laser-induced forward transfer of metallic nanoparticles from a polyethylene terephthalate polymeric substrate was suggested. Transferred nanoparticles were characterized by scanning and transmission electron microscopy, energy-dispersive X-ray and Raman spectroscopy. The antibacterial modality of the method was tested on Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas Aeruginosa) bacterial biofilms in vitro, revealing their complete destruction. The proposed simple, cost-effective and potentially mobile biofilm treatment method demonstrated its high and broad bactericidal efficiency.

Active and passive hybrid ways are described for controlling biofilms and the planktonic form of pathogenic microorganisms based on different bactericidal

We have investigated the size effect (quasi-classical size effect) in nanocomposites. It was shown that the size effect can change the amplitude, form and sign of the optical and magnetooptical spectra. We have deduced formulas for size effect and discussed the applications of the distributions for corrected description of optical and magnetooptical properties with regard to the granule size effect. It is very important to consider the distribution on the granule size in size effect. This fact allows to describe optical and magnetooptical spectra of nanocomposites better, especially in near IR due to intraband electron transitions. We have deduced formulas for size effect and discussed applications of the distributions for corrected description of optical and magnetooptical properties with regard to the effect of the granule size.