Month: November 2021

Scientists of Tomsk Polytechnic University jointly with their colleagues from the universities of Great Britain and Taiwan have proposed a new method how to obtain a photonic hook, a new type of artificially curved light beam. They were able to generate the photonic hook using two small bars from a dielectric material.

The proposed method turned out to be simpler than the previous one. The new method was described in the article released in Scientific Reports published by the Nature Portfolio publishing house (IF: 5,133; Q1).

The photonic hook is a type of artificially curved light beam. Previously, Airy beams, the only one type of curved light beams, were known to science. The research group from TPU jointly with their colleagues from Bangor University (Great Britain) and a number of Russian universities theoretically substantiated and then experimentally confirmed the existence of the photonic hook. Such a hook can be used, for instance, in microscopy for super-resolution imaging and for manipulating nanoparticles.

“Our first and by the last moment, the only one method of generating the photonic hook, although was incomparably simpler than methods of obtaining Airy beams, however, required the application of a special-shaped particle or a special-shaped irradiating beam. For instance, there was required a cube-shaped microparticle with a prism attached to it. Percolating this particle, photon beam radiation twisted and took a shape of a hook,” Igor Minin, Professor of the Division for Electronic Engineering of the TPU School of Non-Destructive Testing, a project supervisor, says.

“The new method allowed obtaining a hook using two parallel rectangular microbars. The bars can be easily made of a wide range of dielectric materials, such as glass or polytetrafluoroethylene. Furthermore, everything can be done on the plane, what is convenient.”

“The new method allowed obtaining a hook using two parallel rectangular microbars. The bars can be easily made of a wide range of dielectric materials, such as glass or polytetrafluoroethylene. Furthermore, everything can be done on the plane, what is convenient,” Igor Minin says.

The photonic hook is generated by the new method in the following way: an electromagnetic wave fractionizes into two parts, the first part percolates the bars, while the second part percolates between them. At the output, the waves merge and finally, the hook becomes twisted.

“In this article, we described the physics of obtaining the hook by the new method. It provided one more tool for generation of the curved photonic beam required in research works,” the scientist explains.

By changing the distance between two bars and their refractive indexes, it is possible to control the hook shape and its curvature.

“Further, we intend to research the situations where the distance between the bars is filled not only by air. It is possible to obtain the hook in gas or liquid mediums. It also can affect the characteristics of the obtained hook,” Igor Minin says.

Among the article authors, there were the scientists from Tomsk Polytechnic University, Newcastle University (Great Britain) and National Chiao Tung University (Taiwan). The research work was supported by a grant of the Russian Foundation for Basic Research and the TPU Competitiveness Enhancement Program.

Chemists of Tomsk Polytechnic University jointly with their colleagues from the Czech Republic have developed a new method for the MXene surface modification and solved the problem of their instability.

MXenes are a new family of nanomaterials. The scientists were able to graft hydrophobic organic molecules on the nanomaterial surface using iodonium salts under surface plasmon resonance (SPR). Such grafting allowed enhancing MXene stability by four-folds. Moreover, the method was quite simple. Alternatively to other methods, it did not require great energy input or complicated equipment. The research data has been published in the 2D Materials academic journal (IF: 7,103; Q1).

MXenes were discovered around 10 years ago. It is a class of two-dimensional materials consisting of carbon atoms and transition metals, for instance, titanium. They are very thin. Their thickness is equal to only a few atoms. MXenes possess unique properties and are considered promising materials in various areas, such as nanoelectronics, water splitting for hydrogen production.

“In the MXene application, there are two problems. They are sensitive in the air and their meaningful technological properties greatly depend on surface condition, i.e. the properties determinate chemical groups, which are located on the surface.  The already known methods for surface modification reduce to reactions proceeding under high energies and temperatures.

“In the MXene application, there are two problems. They are sensitive in the air and their meaningful technological properties greatly depend on surface condition, i.e. the properties determinate chemical groups, which are located on the surface.  The already known methods for surface modification reduce to reactions proceeding under high energies and temperatures.

It is always complicated and expensive. Therefore, we saw the solution to these problems in the MXene surface modification using iodonium salts. At the same time, there was an obvious problem for the chemists: in conventional conditions, iodonium salts do not react with surfaces,” Pavel Postnikov, Associate Professor of the TPU Research School of Chemistry and Applied Biomedical Sciences, one of the article authors, says.

In order to make iodonium salts undergo required reactions onto the MXene surface, the researchers used SPR. The resonance occurred onto the metal surface under light illumination, i.e. plasmonic quasiparticles emerged onto the surface.

“First, we produced iodonium salts with groups possessing hydrophobic properties, i.e. water-repellent properties. Then, the MXene suspension was added and a laser ray was directed to the solution. It caused SPR required for radical formation from iodonium salts, which in return bound to the surface. The reaction proceeded under room temperature,” the scientist explains.

In order to prove the stability of the modified MXenes, the researchers kept them in the air in a humid environment for one week.

“In comparison with an initial MXene, our material turned out to be more stable by four-folds. At the same time, it was hydrophobic,” Pavel Postnikov says. “The research work was fundamental. We demonstrated the principle that our method worked and brought very good results. Further, we intend to develop the method and search for ways of giving MXenes specific properties.”

The article authors were also researchers from the University of Chemistry and Technology, Prague, the Institute of Physics of the Czech Academy of Sciences and Charles University in Prague. The research work was conducted with the support of the Russian Science Foundation.

It must be mentioned that previously, the scientists of Tomsk Polytechnic University jointly with their colleagues from China had conducted an extensive analysis of the latest data in the processing of MXenes, new two-dimensional inorganic materials. The research findings were published in the article of the Chemical Engineering Journal.