Saratov University physicists were the first in the world to discover optimal modes of laser synthesis of hybrid nanostructures based on carbon nanotubes and graphene. The discovery caused a wide resonance in the scientific community, because it is a real breakthrough in the field of nanoelectronics and bioengineering.
As the experts explained, explaining the essence of experimental research to us as popularly as possible, optimal laser synthesis modes mean a certain range of laser irradiation wavelengths, which determines the maximum possible electrical conductivity and strength for a given material. Such nanomaterials are called hybrid. Everyone knows that the word "hybrid" already provides for a combination of similar, but different properties of objects. In this case, two different objects are combined – in their dimension. Carbon nanotubes are a 1D-object, that is, an object whose transverse dimensions can be neglected compared to its length (an example is a human hair - very thin compared to its length). Graphene refers to 2D-objects, that is, it is a thin sheet whose thickness is negligible compared to its size. These hybrid nanomaterials, let's call them “hybrids”, demonstrate increased strength, electrical conductivity and electrical capacity compared to the original 1D and 2D nanomaterials.
The university specialists have identified such a topology of the mutual arrangement of 1D and 2D objects in the hybrid, which not only provides high electrical conductivity and electrical capacity, but also allows to preserve the functional properties of the material during deformation.
As a result of what studies and how exactly were such results obtained? With this question, we turned to the head of the scientific project, Chair of the Department of Radiotechnology and Electrodynamics, SSU, Doctor of Physical and Mathematical Sciences, Professor Olga Glukhova. She clarified the practical significance of the results obtained, their applicability today and in the future.
The research was carried out within the framework of the state task of the Ministry of Education and Science "Topological management of electronic and optoelectronic properties of graphene-nanotube composite materials" and the grant of the Russian Academy of Sciences "Functional branched networks based on single-walled carbon nanotubes, bundles of them and graphene monolayer flakes for emission electronics: new technological solutions and applied developments".
This topic unites the interests of several collectives, including scientific groups of the National Research University "Moscow Institute of Electronic Technology", the First Moscow State Medical University named after I.M. Sechenov, the Technological Center Research and Production Complex, the Institute of Nanotechnologies of Microelectronics of the Russian Academy of Sciences and, of course, the Saratov National Research State University, where, in fact, the optimal mode for creating hybrid nanostructures based on carbon nanotubes and graphene was discovered - the most optimal frequency of laser nanowelding of graphene with nanotubes.
NANOIMPLANT BASED ON GRAPHENE AND CARBON TUBES
As Olga Evgenievna told about the history of the scientific problem, initially it was for medical purposes that special nanomaterials were needed, which would be both highly conductive and durable. It is such materials that should act as implants for the heart – "patches" in case of myocardial rupture. Branched grids of hybrid nanomaterial based on graphene and carbon nanotubes have become one of the most suitable materials. Initially, two types of nanotubes were considered: single–layer - the walls of which consisted of a single layer of carbon atoms; and multi–layered - they can be imagined as a set of cylinders of different diameters nested one into another.
To understand how the connection with graphene will affect the properties of each type of nanotubes to ensure their strength and conductivity, physicists initially had to "stitch" them. At the Moscow Institute of Electronic Technology, a laser nanosweld technology was developed, which made it possible to firmly connect materials with chemical bonds. To do this, the researchers used laser radiation with short pulses. The 3D meshes obtained as a result of laser welding were placed in a solution containing macrobiomolecules, and as a result of laser irradiation, a new nanobiomaterial – an implant - was obtained from the solution.
One of the first applications of the new nanobiomaterial was an implant that simultaneously replaces and promotes the restoration of cartilage tissue in joints. Preclinical studies have shown that such a biocompatible nanomaterial stimulates the growth of cartilage tissue cells.
Further, the topic of developing implants based on hybrid nanomaterials has received a new development, for example, as "patches" for the heart after a myocardial infarction. Unique preclinical tests were successfully conducted at the I.M. Sechenov First Moscow State Medical University.
As you know, a living organism can independently "patch up" a rupture of the heart muscle, but with connective tissue, which means that scars remain. But the "nano-patch" will avoid this. How? The nanomaterial is highly elastic, conductive, biocompatible and high–strength – it almost completely replaces the muscle tissue of the myocardium.
A team of doctors, physicists and technologists is working on this and other tasks. Part of this large team, in particular the scientific group of our university, is engaged in mathematical modeling. The scientific group led by O.E. Glukhova includes eight people, including candidates of physical and mathematical Sciences, associate professors of the Department of Radiotechnology and Electrodynamics, SSU, Mikhail Slepchenkov, Vladislav Shunayev, assistant Dmitrii Kolosov, as well as graduate students and undergraduates.
LASER FREQUENCY FOR BETTER NANOWELDING OF STRUCTURES
According to experts, an atomistic model of a 3D grid was built to conduct a numerical experiment in order to identify the best physical conditions for nanoswelding carbon structures. It was with its help that the absorption frequency for all types of nanotubes was identified, which will allow synthesizing the required hybrid materials even with a small laser irradiation power. Quantum modeling makes it possible to determine the local frequency range in the absorption spectrum in which the absorption of laser energy will be maximum.
As a result, scientists have found the very absorption frequency that makes it possible to obtain a new super–nanomaterial hybrid from the source material in the form of separate sheets of graphene and nanotubes. This new material is hyper–high-strength, conducts electric current very well, and is also highly elastic. It is these qualities that are needed to create implants based on it for the heart, blood vessels and joints. The set frequency corresponds to a wavelength of 266 nm of the UV range. It should be noted that lasers of this range were previously used only in dentistry, and now they are in demand in bionic technologies designed to make human life easier by technical means. Previously, a laser with a wavelength of 1064 nm was used for welding nanostructures. Yes, he coped with the task quite successfully and ensured the creation of a new promising hybrid nanomaterial, but, as numerous experimental studies have proved, the predicted new laser wavelength of 266 nm allows the hybrid to increase electrical conductivity and strength by at least 100%.
It became obvious that this discovery of Saratov physicists is a world–class discovery!
MULTIDISCIPLINARY 3D-GRIDS
Today, scientists continue to develop success in solving this interesting scientific problem. It turned out that the 3D meshes they obtained can be used not only in interaction with proteins in medicine, but also in electronics. This is how the multidisciplinary material turned out.
Now physicists are working at the stage of electronic research, studying 3D grids in relation to auto-emission cathodes. Using computer modeling, they are trying to determine the strength limits of graphene grids when exposed to strong external electric fields. It is important to know at what electric field what is obtained by nanosweld will or will not be destroyed – at what electric field strengths, in what place? SSU specialists are conducting complex quantum calculations that will help answer the main question of experimental practitioners: at what point can a nanostructure rupture occur? And their colleagues who synthesize these grids, with the help of their modern equipment, are trying to answer the question of what kind of emission current can be obtained from these grids.
This year, SSU intends to open a new Laboratory for the study of the use of 3D grids in both nanoelectronics and medicine. There are already several patents. Now a patent has been prepared from SSU for the formation of hybrids: it is proposed to use graphene flakes connected to nanotubes along with extended graphene structures. The latter have already been successfully synthesized.
"Our research has shown that the high strength and electrical conductivity of hybrid materials will allow them to be used in nanoelectronics, as well as as components of various bioelectronics devices, as they will help to increase the accuracy and speed of their operation. In the future, we plan to study in more detail the features of the chemical bonds formed between the components of hybrid structures in order to understand whether their physical characteristics can still be improved," says O.E. Glukhova, project manager for the RNF grant.
FROM MEDICINE TO ELECTRIC VEHICLES
Today it is obvious that Saratov physicists have made a significant scientific contribution to nano- and bioelectronics - they have proposed hybrid networks, more efficient single–walled nanotubes instead of multilayer ones, and the optimal frequency of laser irradiation to produce hybrid networks.
The results of the study, supported by a grant from the Russian Science Foundation (RNF), have already been published in the journal Nanomaterials 2021. Vol. 11, No. 8. P. 1875 and Nanomaterials. 2021. Vol. 11, No. 8. P. 1934, as well as Chemical Physics. 2021. Vol. 550. P. 111312, Chemosensors 2021, 9(4), 84. doi.org/10.3390/chemosensors9040084 , Composite Structures 2021, 260, 113517. doi: 10.1016/j.compstruct.2020.113517, Membranes. 2021. Vol. 11, no. 9. P. 658. DOI: 10.3390/membranes11090658.
Employees of the Department of Radiotechnology and Electrodynamics and the Department of Mathematical Modelling of SSU have prepared a monograph Graphene-nanotube composites: Mathematical modelling, which was published by the Moscow publishing house "Rusains". The results obtained indicate that the studied nanocomposites will soon become an integral element base for the creation of devices such as transistors, biosensors, and will also act as radio-absorbing materials and storage devices.
The desired effect was achieved thanks to a special technique of laser "welding", through which scientists have developed hybrid networks based on graphene and carbon nanotubes. The range of applications of the technology is wide, including in medicine. Such material can make the operation of bioelectronic devices, in particular hearing aids, smart watches and various medical sensors, more accurate and faster. The material will also seriously speed up charging and extend the operating time of electric vehicles and other equipment.
Text by: Tamara Korneva
Photos by: Victoria Victorova
Articles from other media on this topic:
RIA Novosti: A new material for electric vehicles and flexible electronics was created in Russia
TASS: Hybrid carbon networks have been created in Russia to improve the work of nano- and bioelectronics
Gazeta.ru: Scientists have improved bioelectronics with hybrid carbon networks
Open Science: Hybrid carbon networks will make nano- and bioelectronics more reliable and faster
