Magneto-Optická a THz Spektroskopie

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Chemical vapor deposition: a potential tool for wafer scale growth of two-dimensional layered materials
(IOP Publishing Ltd, 2022-11-24) El Hammoumi, Mohammed; Chaudhary, Vivek; Neugebauer, Petr; El Fatimy, Abdelouahad
The rapidly growing demand for high-performance and low-power electronic and photonic devices has driven attention towards novel two-dimensional (2D) layered materials. In this regard, 2D layered materials, including graphene, molybdenum disulfide (MoS2), and newly discovered phosphorene, have the potential to take over the existing semiconductor industry due to their intriguing features, such as excellent electrical conductivity, strong light-matter interaction, and especially the ability to scale down the resulting device to the atomic level. However, to explore the full potential of these materials in various technological applications, it is essential to develop a large-scale synthesis method that can provide uniform, defect-free thin film. The chemical vapor deposition (CVD) technique has been proven to produce large-scale and less defective 2D crystals with reasonably good quality and uniformity compared to other elaboration techniques, such as molecular beam epitaxy. This article discusses whether CVD may improve 2D layered materials growth, including graphene and MoS2, and whether it can be used to grow phosphorene. Only a few attempts have been made using CVD-like methods to grow phosphorene directly on the substrate. Still, one has to go long to establish a proper CVD method for phosphorene synthesis.
Anti-myeloma pro-apoptotic Pt(II) diiodido complexes
(Royal Society of Chemistry, 2023-05-31) Masaryk, Lukáš; Weiser Drozdková, Denisa; Sloczynska, Karolina; Moncol, Ján; Milde, David; Krikavova, Radka; Popiol, Justyna; Pekala, Elzbieta; Ondrušková, Katarína; Nemec, Ivan; Smešný, Kateřina; Štarha, Pavel
Platinum-based agents unwaveringly hold their prominent position in cancer treatment. Current research emphasizes finding novel complexes for hard-to-treat cancers with minimum side effects, capable of overcoming resistance. This work presents easy-to-prepare diiodidoplatinum(II) complexes cis-[PtI2(L-n)(2)] (1-7) with imidazole derivatives (L-n), which were considerably effective against multiple myeloma cell lines U266B1 and KMS12-PE. The leading compound 6 (at 3 mu M concentration) extraordinarily reduced viability of U266B1 and KMS12-PE myeloma cells to 3.0% and 1.1%, respectively, and exceeded the conventional platinum-based anticancer drug cisplatin (93.1% and 88.3%, respectively) that is used clinically for the combination therapy of multiple myeloma. Complex 6 was significantly more effective in inducing apoptosis in KMS12-PE cells without interleukin-6 (IL-6) expression than in U266B1 cells with IL-6 expression. Complex 6 also induced apoptosis in co-culture of KMS12-PE with non-cancerous stromal fibroblasts (HS-5), and displayed markedly lower activity in the HS-5 stromal fibroblast cells than in myeloma cells, pointing out its pharmocologically prospective selectivity towards the cancer cells over the normal ones. No caspase 3/7 activity was detected in apoptotic KMS12-PE cells treated by complex 6 indicating a different mechanism of apoptosis action from cisplatin. This work demonstrates that simple non-classical platinum(II) complexes represent a new perspective for a monotherapy of hard-to-treat multiple myeloma.
Thermal- and light-induced SCO effect in Fe(II) complexes and coordination polymers
(SCIENDO, 2023-01-01) Šagátová, Alexandra; Brachňaková, Barbora; Šalitroš, Ivan
The review presents several families of spin crossover (SCO) active Fe(II) coordination compounds with photoactive N-donor heterocyclic ligands, in which the photoinduced structural changes can activate reversible change of spin state and thus control magnetic properties under isothermal conditions. Detailed description of structural, spectral, and magnetic behavior for selected examples of photoisomerizable coordination compounds are provided. From the application point of view, light is an excellent tool to control SCO properties. The first and best known approach called Light Induced Excited Spin State Trapping (LIESST) has a significant technological limitation due to low temperatures (< 120 K) required for the trapping and existence of photoexcited metastable states. The second and more elegant approach known as Ligand-Driven Light-Induced Spin Crossover (LD-LISC) seems to be a very suitable strategy utilizing light-induced structural changes to control the spin. Isomerization of photoswitchable groups, such as azobenzenes or stilbenes, can cause reversible transformation between two isomeric forms after exposition to selective wavelengths at ambient temperature. A very recent third approach, the Guest-Driven Light-Induced Spin Crossover (GD-LISC) effect employing the photoisomerizable guest molecules to control the spin state has also been introduced.
Ultrafast Dynamics of Valley-Polarized Excitons in WSe2 Monolayer Studied by Few-Cycle Laser Pulses
(MDPI, 2023-03-28) Koutenský, Petr; Slobodeniuk, Artur; Bartoš, Miroslav; Trojánek, František; Malý, Petr; Kozák, Martin
We report on the experimental investigation of the ultrafast dynamics of valley-polarized excitons in monolayer WSe (Formula presented.) using transient reflection spectroscopy with few-cycle laser pulses with 7 fs duration. We observe that at room temperature, the anisotropic valley population of excitons decays on two different timescales. The shorter decay time of approximately 120 fs is related to the initial hot exciton relaxation related to the fast direct recombination of excitons from the radiative zone, while the slower picosecond dynamics corresponds to valley depolarization induced by Coloumb exchange-driven transitions of excitons between two inequivalent valleys
High harmonic generation in monolayer MoS2 controlled by resonant and near-resonant pulses on ultrashort time scales
(AIP Publishing, 2023-08-01) Peterka, Pavel; Slobodeniuk, Artur; Novotný, Tomáš; Suthar, Pawan; Bartoš, Miroslav; Trojánek, František; Malý, Petr; Kozák, Martin
We report on experimental investigation of nonperturbative high harmonic generation (HHG) in monolayer MoS2 in the ultraviolet spectral region driven by mid-infrared light. We study how the HHG is influenced by pre-excitation of the monolayer using resonant and near-resonant pulses in a pump-probe-like scheme. The resonant light creates high density exciton population. Due to ultrafast dephasing caused by electron-electron scattering, the HHG is suppressed in the presence of pre-excited carriers. In the case of near-resonant excitation with photon energy below the exciton transition, the dynamics of the observed suppression of the HHG yield contains a fast component, which is a consequence of momentum scattering at carriers, which are excited by two-photon transition when the two pulses temporally overlap in the sample. This interpretation is supported by comparing the experimental data with theoretical calculations of the two-photon absorption spectrum of the MoS2 monolayer. This work demonstrates a possibility to control HHG in low-dimensional materials on ultrashort timescales by combining the driving strong-field pulse with a weak near-resonant light.

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