This research area deals with objects and phenomena which can be studied by applying the fundamental principles and technological approaches of Yanson point-contact spectroscopy related to the gas-sensitive effect. The fact that the researchers of Department together with their co-authors have already created ultrasensitive point-contact nanosensors exploiting the point-contact gas-sensitive effect and characterized by parameters that excel those of the existing analogues makes the studies quite promising. Nonlinear current states in electrical conductivity of point-contact sensors are the key to understanding the nature of the point-contact gas-sensitive effect and thus provide multiple possibilities of development of brand new sensors and advanced sensor-based technologies.

Leading researchers: V.A. Gudimenko and D.A. Harbuz.

This new area in sensorics proposed by the researchers of Department is based on the study of energy of interaction between a point-contact structure and a gas or liquid by means of finding and analyzing the parameters of quantized electrical conductivity of the point contacts. The quantum nature of electrical properties of point contacts makes it possible to register very subtle states of the point-contact conductivity channel caused by adsorption of an external agent. The measurement can be performed with a resolution down to a quantum of conductivity, which corresponds to the addition of an atom of the investigated substance to the point contact. As a result, point-contact sensors possess an ultrahigh sensitivity up to the highest sensitivity levels of sensor devices known so far. The quantum approach opens up wide possibilities of developing a broad spectrum of new methods, devices, and technologies, since the knowledge of energetic parameters of a physical system is a key factor for being able to determine and foresee its properties. Energetic parameters of the response of point-contact sensors allow one not only to distinguish materials from one another, but also to analyze complex gaseous media via registration their profiles without determination of single components of the medium.

Leading researchers: A.V. Savytskyi and A.O. Herus.

The importance of the study of point-contact sensor multistructures arises from their unique properties, among which is a complex spectrum-like response generated by point contacts under the action of multicomponent gaseous media. Before it was discovered by the researchers of the Team and their co-authors, this type of the response signal had been unknown for sensor devices based on the measurement of electrical conductivity. The reason is that point contacts are nanostructured objects of quantum nature, so they can register minute structural and energetic variations caused by adsorption of external agents. Temporal characteristics of the response signal generated by a point-contact sensor device provide information about the adsorption energy levels of the gas ingredients. The complex gas mixture affects the time dependence of electrical conductivity of point contacts, which results in its spectrum-like form similar to a point-contact spectrum obtained in Yanson point-contact spectroscopy. This peculiarity of point contacts allows one to analyze complex gas mixtures by taking a general profile of a gaseous medium without the need to determine its particular components. This ensures realization of a new method for analysis of a complex molecular system with point-contact sensor devices. The proposed approach has no analogues in sensor engineering. Its effectiveness has been demonstrated by the analyses of exhaled human breath performed by the researchers of Department in collaboration with their co-authors. Making use of the fact that this complex biological gaseous medium contains metabolic products of bacteria a human body is infected with, we first proved the possibility of detecting carcinogenic strains of Helicobacter pylori in real-time mode. The results of this innovative study were published in the leading scientific journal – Journal of Breath Research (December 2015) – and presented on the site of the National Academy of Sciences of Ukraine (NASU) in April 2016 as one of the most outstanding scientific achievements of the NASU researchers. The importance of the discovery made by the scientists of Department and their co-authors lies in the fact that none of the currently existing methods for determining Helicobacter pylori can be used as a screening diagnostic method because of their high cost. It should also be noted that none of the known methods is able to determine carcinogenic strains of the bacterium in real-time mode. The possibility of using point-contact sensors to analyze the exhaled breath opens up real prospects for development of a new generation of breath tests which, thanks to their simplicity and affordability, can be widely used for large-scale screening and monitoring of great masses of population. This will help to timely detect carcinogenic strains of Helicobacter pylori and prevent development of ulcer diseases and gastric cancer in an early stage of infection even in countries with low income.

Another application that point-contact multistructures based on TCNQ compounds have found is sensors for the determining human hormonal background. In our recent studies, we have shown that such sensors can be successfully used for express analysis of the content  in the body of such important hormones as melaton, serotonin and cortisol by breath gas analysis.

An important feature of the point contacts implementing to determine the content of hormones in the human body is the fact that such task can be solved by two different approaches. The first approach is parametric, similar the to one we previously used to detect Helicobacter pylori strains. The other method is a unique development based on the spectral nature of the sensor response to the action of a gaseous agent. Understanding this feature made it possible to find temporal sections on the breath gas profile corresponding to the concentrations of the certain components in the biological substance under study.

The results of the research carried out are both fundamental and applied. From a fundamental point of view, the possibility of localizing an area of the curve corresponding to a certain binding energy of a substance with a surface classifies point-contact sensors as a spectroscopic research tool. The applied character  is the the application area of such sensors expansion in the direction of medical diagnostics. An inexpensive, compact and easy-to-maintain tool that provides non-invasive analysis of human hormonal levels in real time is definitely promising both for express diagnosis of a human body condition and for monitoring the treatment process.

Leading researchers: V.A. Gudimenko, D.A. Harbuz, V.I. Belan, and M.D. Romanov.