Igor V. Shvets

Metallic PtSe is obtained from thermal conversion of PtSe ₂ grown by chemical vapor deposition, highlighting the significance of sub-stoichiometric phases within transition metal dichalcogenide films.

The development of new synthetic strategies to introduce and control chirality in inorganic nanostructures has been highly stimulated by the broad spectrum of potential applications of these exiting nanomaterials. Molybdenum disulfide is among the most investigated transition metal dichalcogenides due to its promising properties for applications that spread from optoelectronic to spintronic. Herein, we report a new two‐step approach for the production of chiroptically active semiconductor 2H MoS₂ nanosheets with chiral morphology based on the manipulation of their crystallographic structure. In the first step, metastable metallic 1T MoS₂ nanosheets with chiral morphology were produced via hydrothermal synthesis. Then, thermal annealing was used to progressively tune the conversion of the metallic 1T phase into the thermodynamically stable semiconductor 2H phase while preserving the nanocrystals’ chiral morphology. Our detailed study covers the evolution of the chiroptical properties of the material during the crystallographic phase transition, revealing critical insights into the formation of chiroptically active excitonic transitions. This study represents a unique approach to the production of high‐quality chiral nanomaterials by exploiting phase engineering, and paves the way for the development of new synthetic methods to further expand the range and properties of chiral nanomaterials.

The development of new synthetic strategies to introduce and control chirality in inorganic nanostructures has been highly stimulated by the broad spectrum of potential applications of these exiting nanomaterials. Molybdenum disulfide is among the most investigated transition metal dichalcogenides due to its promising properties for applications that spread from optoelectronic to spintronic. Herein, we report a new two‐step approach for the production of chiroptically active semiconductor 2H MoS₂ nanosheets with chiral morphology based on the manipulation of their crystallographic structure. In the first step, metastable metallic 1T MoS₂ nanosheets with chiral morphology were produced via hydrothermal synthesis. Then, thermal annealing was used to progressively tune the conversion of the metallic 1T phase into the thermodynamically stable semiconductor 2H phase while preserving the nanocrystals’ chiral morphology. Our detailed study covers the evolution of the chiroptical properties of the material during the crystallographic phase transition, revealing critical insights into the formation of chiroptically active excitonic transitions. This study represents a unique approach to the production of high‐quality chiral nanomaterials by exploiting phase engineering, and paves the way for the development of new synthetic methods to further expand the range and properties of chiral nanomaterials.

Platinum diselenide (PtSe₂), a 2D noble metal dichalcogenide, has recently received significant attention due to its outstanding properties. It undergoes a semimetal to semiconductor transition when thinned, offers a bandgap in the infrared range, and exhibits excellent stability in ambient conditions. These properties make it a prime active material in optoelectronic and chemical sensing devices. However, there is a high demand for a synthesis method that can produce large‐scale and reliable high‐quality PtSe₂. In this study, the growth of PtSe₂ is presented by metal–organic vapor deposition on a variety of substrates. Comprehensive Raman, X‐ray photoelectron, and X‐ray diffraction spectroscopy, as well as scanning tunneling microscopy characterization reveals the high quality of the deposited PtSe₂. Domains within the films are found to be up to several hundreds of nanometers in size, and their highly ordered crystalline structure is evident from atomic‐scale measurements. Electrical characterization demonstrates improved conductivity relative to conventional synthesis methods. This study provides fundamental guidance for the scalable synthesis and implementation of high quality PtSe₂ layers with controllable thickness, offering a key requirement for the implementation of PtSe₂ in future applications.

In relation to perovskites, tweaking the oxidation state of the B‐site cation is fundamental to controlling the catalytic activity of these materials, thus necessitating a complete characterization of surface oxidation states. Herein, using a combination of atomic‐scale imaging and spectroscopic techniques, structure‐property correlation in barium manganese oxide (BaMnO₃) is established for the oxygen reduction reaction (ORR). Electron energy loss spectroscopy (EELS) on the synthesized BaMnO₃ find the rods to contain an amorphous surface layer with reduced Mn³⁺ states compared to Mn⁴⁺ states in the bulk. Consequently, the BaMnO₃ rods show electrocatalytic activity for the ORR, which originates from the presence of Mn³⁺ at the rod surface. Furthermore, heating of the samples in air at 300 and 800 °C results in a decrease in the number of Mn³⁺ states, and thus lowering of the ORR activity. This study represents a step‐stone study in understanding the mechanism of ORR activity and its association to the Mn³⁺ state at the perovskite's surface, opening up possibilities for further surface engineering and tuning catalytic properties.

Semiconducting thin-film polycrystalline PtS ₂ is characterised by atomically resolved scanning tunnelling microscopy and spectroscopy.

We investigate the origin of the variation in resistive switching hysteresis of VO₂ thin films. Using pulsed electrical measurements in textured VO₂ thin film devices, we show that the hysteresis observed in I–V curves results from Joule heating effects, particularly in the low-resistance state. The hysteresis is reduced by increasing the cooling time between pulses. Based on a mechanism of Joule heating-induced metal-insulator transition, numerical simulations are performed, which agree with the experimental variation in the hysteresis. Finally, a framework for engineering the I–V curves of VO₂ devices is proposed.