In this paper, we consider new quantum mechanisms for selective detection in complex gaseous media which provide the highest possible efficiency of quantum sensors and for the first time analyze their nature. On the basis of these quantum mechanisms, the concepts of quantum detection and innovative methods of analysis are developed, which are virtually impossible to implement in the conventional conductive sensors and nanosensors. Examples of original solutions to problems in the field of detection and analysis of human breath using point-contact sensors are considered. A new method of analysis based on detection of metastable quantum states of the "point-contact sensor—breath" system in dynamic mode is proposed. The conductance histogram of dendritic Yanson point contacts recorded for this system is a unique energy signature of breath which allows differentiation between the states of human body. We demonstrate that nanosized Yanson point contacts, which, thanks to their quantum properties, can replace a massive spectrometer, open up wide opportunities for solving complex problems in the field of breath analysis using a new generation of portable high-tech quantum sensor devices.

Quantum structures are ideal objects by which to discover and study new sensor mechanisms and implement advanced approaches in sensor analysis to develop innovative sensor devices. Among them, one of the most interesting representatives is the Yanson point contact. It allows the implementation of a simple technological chain to activate the quantum mechanisms of selective detection in gaseous and liquid media. In this work, a portable device for multipurpose research on dendritic Yanson point contacts and quantum sensing was developed and manufactured. The device allows one to create dendritic Yanson point contacts and study their quantum properties, which are clearly manifested in the process of the electrochemical cyclic switchover effect. The device tests demonstrated that it was possible to gather data on the compositions and characteristics of the synthesized substances, and on the electrochemical processes that influence the production of dendritic Yanson point contacts, as well as on the electrophysical processes that provide information on the quantum nature of the electrical conductance of dendritic Yanson point contacts. The small size of the device makes it simple to integrate into a micro-Raman spectrometer setup. The developed device may be used as a prototype for designing a quantum sensor that will serve as the foundation for cutting-edge sensor technologies, as well as be applied to research into atomic-scale junctions, single-atom transistors, and any relative subjects.

Abstract In this paper, we consider new quantum mechanisms for selective detection in complex gaseous media which provide the highest possible efficiency of quantum sensors. On the basis of these quantum mechanisms, the concepts of quantum detection and innovative methods of analysis are developed, which are virtually impossible to implement in the conventional conductive sensors and nanosensors. Examples of original solutions to problems in the field of detection and analysis of human breath using point-contact sensors are considered. A new method of analysis based on detection of metastable quantum states of the "point-contact sensor – breath" system in dynamic mode is proposed. The conductance histogram of dendritic Yanson point contacts recorded for this system is a unique energy signature of breath which allows differentiation between the states of human body. We demonstrate that nanosized Yanson point contacts, which, thanks to their quantum properties, can replace a massive spectrometer, open up wide opportunities for solving complex problems in the field of breath analysis using a new generation of portable high-tech quantum sensor devices.

In recent years, the problem of CBRN materials and explosives has attracted much attention because the threat they pose is high and tends to increase. Effective protection of critical infrastructure against CBRNE threats can be achieved by developing breakthrough technologies to create a new generation of portable, multifunctional, autonomous, energy-efficient, and low-cost devices. One of the advanced approaches to creating new innovative tools to successfully control CBRNE agents can be based on high-tech solutions involving point-contact sensors. Research and development of point-contact sensors is an emerging trend in modern sensorics. To better understand the mechanisms of point-contact sensors operation and their potential to solve the global security problems we pay attention to some of the original properties of Yanson point contacts. They are totally different from those of traditional sensors based on the principle of electric conduction change and, among others, exploit use of tunnelling mechanisms. Special attention is paid to the potential use of point-contact sensors in the development of combined devices and technologies, involving such competing schemes as THz techniques, to detect terror threats and CBRNE agents.

The review covers the most recent results and advancements in point-contact nanosensors. Fundamentals of Yanson point contacts that determine their spectroscopic and sensor behaviour are considered. A special attention is paid to the basic properties of these nanoobjects which are responsible for their ability to demonstrate the point-contact gas-sensitive effect and excellent sensor performance. Classification of point contacts into homo- and heterocontacts and peculiarities of their electric characteristics are described. The technological principles of Yanson point-contact spectroscopy used for designing various types of point-contact sensors are discussed. The innovative approaches in sensor engineering which are evident from the peculiar properties of point-contact sensors are presented. The point-contact method of sensor spectral analysis of complex gas mixtures which does not require detection of separate components, and selective analysis of gaseous and liquid media through conductance registration in dynamic regime are introduced. Prospects for application of point-contact sensors for security, environmental and health issues are discussed.

The aim of this paper was to develop a prototype of new quantum sensor whose sensing element is a Yanson point contact. The exceptional features of quantum point-contact sensors, besides the proper quantum properties of Yanson point contacts, are due to a number of their fundamental properties. These properties include the specific potential distribution in the contact contributing to the appearance of the point-contact gas-sensitive effect and the gapless electrode system formed in the point-contact conduction channel in a liquid medium and responsible for the cyclic switchover effect which makes it possible to record a broad spectrum of quantum states in dendritic Yanson point contacts placed in the analyzed media. Conductance histograms corresponding to the quantum states of dendritic point contacts undergoing transformations are markers of certain media and could be recorded with the prototype of new quantum sensor developed in our paper. The efficiency of the developed prototype was demonstrated in experiments with gaseous media of argon and ambient air. The obtained results lay the foundations for the development of new generation of quantum sensors for selective detection in liquid and gaseous media.

The diversity of techniques employed in modern sensing nanodevices is crucial for large-scale use of sensors in multifunctional technological cycles. We propose a new concept of selective detection of gases and liquids based on the formation of an original quantum system and registration of its energy states in dynamic mode using dendrite point contacts synthesized electrochemically in the probed medium. The in situ synthesis of nanosized dendrite point contacts is shaped by the cyclic switchover effect which takes place in an electrolyte in contact with the analyzed medium and results in consecutive cycles of the formation and destruction of an electrochemical gapless electrode system. Conductivity of such point contacts demonstrates quantum behavior driven by the shell effect which determines the geometry of their conducting channels. Temporal dependence of dendrite point contact electrical resistance measured in dynamic mode is characterized by a step-like structure which reflects the metastable quantum states of the system whose distribution can be presented in the form of a conductance histogram. The histogram is a unique fingerprint of the probed medium and can thus be used to unambiguously identify it. The dynamic mode scanning of the energy states of point contact quantum systems proposed here makes it possible to develop a universal method for selective detection of many gaseous and liquid media including such hard to detect substances as methane and rare gases. The new approach is expected to prove its efficiency in investigating quantum effects for various sensor applications and stimulate the development of the next generation of highly selective nanodevices. The new concept of selective detection of gases and liquids is based on the registration of quantum states of nanosized dendrite point contacts synthesized in the probed medium.

We propose a new operating principle of selective detection in gases and liquids based on formation of an original quantum system and registration of its energy states in dynamic mode using dendritic point contacts.

A new phenomenological approach is proposed to formalize "the elongated element" as electrochemical medium in which electrode reactions are localized on the surface of an elongated first-class conductor with the outline dimensions ratio (d/l(et)) -> 0, where d is the effective cross section size and l(el) is the length of the conductor in contact with a second-class conductor. This architecture of electrochemical system is used to develop ultrasensitive broadly functional sensor devices. The object under consideration can become the basis for creation of state-of-the-art, yet inexpensive, technologies for synthesizing functional atom sized structures and nanostructured materials.