Browsing by Author "Korotcenkov, Ghenadii"

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Acid-base properties of the surface of zinc oxide powders subjected to milling in the attritor [Articol]
(IOP Publishing Ltd, 2020) Korotcenkov, Ghenadii
Using the method of acid-base indicators adsorption, the influence of mechanical stresses and defects, arising in the milling process, on the surface properties of ZnO powders is analyzed. An explanation of the changes in acid-base properties is given.
Carbon 1s photoemission line analysis of C-based adsorbate on (111)In2O3 surface: The influence of reducing and oxidizing conditions [Articol]
(Elsevier, 2016) Brînzari, Vladimir; Cho, B.K.; Korotcenkov, Ghenadii
Synchrotron radiation photoemission study of C 1s line of (111) In2O3 surface was carried out under HV (high vacuum) doses of oxygen, carbon monoxide and water. Gas interaction with the surface was activated by heating of In2O3 monocrystalline film at temperatures of 160 or 250 °C. The study of complex structure of C 1 s line and evolution of its fine components allowed to establish their nature and to propose possible surface adsorbed species and reactions, including a direct chemisorption and dissociation of CO molecules. Reduction or oxidation of the surface determines whether the first (chemisorption) or the second (dissociation) process takes place. The latter is responsible for additional formation of ionosorbed oxygen. Both processes have not been previously reported for In2O3 and for conductive metal oxides.
Conductometric gas sensors based on metal oxides modified with gold nanoparticles : a review [Articol]
(Springer, 2016) Korotcenkov, Ghenadii; Brinzari, Vladimir; Cho, Beong K.
This review (with 170 refs.) discusses approaches towards surface functionalizaton of metal oxides by gold nanoparticles, and the application of the resulting nanomaterials in resistive gas sensors. The articles is subdivided into sections on (a) methods for modification of metal oxides with gold nanoparticles; (b) the response of gold nanoparticle-modified metal oxide sensors to gaseous species, (c) a discussion of the limitations of such sensors, and (d) a discussion on future tasks and trends along with an outlook. It is shown that, in order to achieve significant improvements in sensor parameters, it is necessary to warrant a good control the size and density of gold nanoparticles on the surface of metal oxide crystallites, the state of gold in the cluster, and the properties of the metal oxide support. Current challenges include an improved reproducibility of sensor preparation, better long-term stabilities, and a better resistance to sintering and poisoning of gold clusters during operation. Additional research focused on better understanding the role of gold clusters and nanoparticles in gas-sensing effects is also required.
Current Trends in Nanomaterials for Metal Oxide-Based Conductometric Gas Sensors: Advantages and Limitations—Part 2: Porous 2D Nanomaterials [Articol]
(2023) Korotcenkov, Ghenadii; Tolstoy, Valeri P.
This article discusses the features of the synthesis and application of porous two-dimensional nanomaterials in developing conductometric gas sensors based on metal oxides. It is concluded that using porous 2D nanomaterials and 3D structures based on them is a promising approach to improving the parameters of gas sensors, such as sensitivity and the rate of response. The limitations that may arise when using 2D structures in gas sensors intended for the sensor market are considered.
Current trends in nanomaterials for metal oxide-based conductometric gas sensors: Advantages and limitations. part 1: 1D and 2D nanostructures [Articol]
(MDPI, 2020) Korotcenkov, Ghenadii
This article discusses the main uses of 1D and 2D nanomaterials in the development of conductometric gas sensors based on metal oxides. It is shown that, along with the advantages of these materials, which can improve the parameters of gas sensors, there are a number of disadvantages that significantly limit their use in the development of devices designed for the sensor market.
Handbook of Humidity Measurement: Methods, Materials and Technologies,Vol. 1: Spectroscopic Methods of Humidity Measurement
(Taylor & Francis Ltd, 2018) Korotcenkov, Ghenadii
The first volume of The Handbook of Humidity Measurement focuses on the review of devices based on optical principles of measurement such as optical UV, fluorescence hygrometers, optical and fiber-optic sensors of various types. Numerous methods for monitoring the atmosphere have been developed in recent years, based on measuring the absorption of electromagnetic field in different spectral ranges. These methods, covering the optical (FTIR and Lidar techniques), as well as a microwave and THz ranges are discussed in detail in this volume. The role of humidity-sensitive materials in optical and fiber-optic sensors is also detailed. This volume describes the reasons for controlling the humidity, features of water and water vapors, and units used for humidity measurement.
How to Improve the Performance of Porous Silicon-Based Gas and Vapor Sensors? Approaches and Achievements [Articol]
(Wiley, 2019) Korotcenkov, Ghenadii; Rusu, E.
It is shown that, along with the advantages, sensors based on porous silicon (PSi) have disadvantages that inhibit their widespread use. The parameters of PSi which can affect the performance of PSi-based sensors are considered in detail, and approaches are analyzed that allow for the improvement of the main characteristics of PSi-based gas and vapor sensors. It is concluded that despite the progress made in terms of improving the sensitivity, selectivity, and stability of PSi-based sensors, further research and development in this direction is necessary, as the existing methods do not provide the required stability of the characteristics and selectivity of their response.
In2O3- and SnO2-based ozone sensors: Design and characterization [Articol]
(Taylor & Francis Ltd, 2018) Korotcenkov, Ghenadii; Brinzari, Vladimir; Cho, B.K.
This article describes in detail the SnO2 and In2O3 metal oxides as materials for designing solid state conductometric ozone sensors. The main focus of this article is on the description of the SnO2 and In2O3 films' structural parameters important for gas sensor design and on the establishment of the main regularities of the film parameters influence on the sensor characteristics. Advantages and disadvantages of approaches used for optimization of ozone sensor parameters are also analyzed. In particular, surface modification, bulk doping of SnO2 and In2O3, and the use of 1D structures and hybrid materials are considered. The main factors, controlling parameters of SnO2- and In2O3-based ozone sensors, are determined, and recommendations for the process of the SnO2 and In2O3 films deposition, facilitating the search of the film parameters and the fabrication technologies that optimize the ozone sensor performance, are formulated.
In2O3-based thermoelectric materials: the state of the art and the role of surface state in the improvement of the efficiency of thermoelectric conversion [Articol]
(MDPI, 2018) Korotcenkov, Ghenadii; Brinzari, Vladimir; Ham, Moon-Ho
In this paper, the thermoelectric properties of In2 O3 -based materials in comparison with other thermoelectric materials are considered. It is shown that nanostructured In2 O3 Sn-based oxides are promising for thermoelectric applications at moderate temperatures. Due to the nanostructure, specific surface properties of In2 O3 and filtering effects, it is possible to significantly reduce the thermal conductivity and achieve an efficiency of thermoelectric conversion inaccessible to bulk materials. It is also shown that a specific surface state at the intergrain boundary, optimal for maximizing the filtering effect, can be achieved through (1) the engineering of grain boundary parameters, (2) controlling the composition of the surrounding atmosphere, and (3) selecting the appropriate operating temperature.
The influence of gold nanoparticles on the conductivity response of SnO2-based thin film gas sensors [Articol]
(Elsevier, 2015) Korotcenkov, Ghenadii; Brinzari, Vladimir; Gulina, L.B.; Cho, B. K.
The results presented in this study demonstrate that the successive ionic layer deposition (SILD) method for gold nanoparticle formation can be used for surface functionalization of SnO2 films to improve their gas sensing properties. As a result of successive treatments in HAuCl4•nH2O and NaBH4 solutions, gold nanoparticles can be formed on the surface of SnO2 crystallites. The size of the gold particles varies over the range of 1–50 nm depending on the number of SILD cycles. Gas sensing characteristics of the Au-modified SnO2 films are discussed as well. Unlike most studies focused on the development of CO sensors, the present research focuses on the specifics of the response of the SnO2:Au-based sensors to other gases, such as hydrogen and ozone. It is established that gold nanoparticles deposited on the SnO2 surface are active toward both reducing and oxidizing gases, and the effect of the SnO2 surface decoration by the gold nanoparticles on the gas sensing characteristics depends on the number of deposition cycles (i.e., the size of the gold particles). The sensitization to ozone and hydrogen suggests that the application of the surface modification by gold in the field of gas sensor design should not be limited by optimization of the CO sensor's parameters. Models showing the promotional role of Au additives are discussed, and a mechanism of sensitization in the SnO2:Au-based gas sensor is proposed.
Kinetic approach to receptor function in chemiresistive gas sensor modeling of tin dioxide. Steady state consideration [Articol]
(Elsevier, 2018) Brinzari, Vladimir; Korotcenkov, Ghenadii
Kinetic approach in phenomenological modeling of SnO2 chemiresistive gas sensor is proposed. It is based on a new perception of chemisorbed oxygen forms and consistent account of main reaction rates into a balance equation of particles on (110) surface. So-called receptor function was considered for dry and humid atmosphere and in the presence of CO. Transducer function was calculated within an electron filtering model. Numerical simulation of the surface coverage by oxygen and major gas sensing characteristics of SnO2 within 150–600 °C temperature range showed sufficient agreement with experimental behavior of nanocrystalline SnO2-based sensors. Model allows interpretation of some of the important features in these characteristics.
Metal oxides for biomedical and biosensor applications [Articol]
(Elsevier, 2021) Mondal, Kunal; Korotcenkov, Ghenadii
Metal Oxides for Biomedical and Biosensor Applications gives an in-depth overview of the emerging research in the biomedical and biosensing applications of metal oxides, including optimization of their surface and bulk properties. Sections cover biomedical applications of metal oxides for use in cell cultures, antibacterial and antimicrobial treatments, dental applications, drug delivery, cancer therapy, immunotherapy, photothermal therapy, tissue engineering, and metal oxide-based biosensor development. As advanced and biofunctionalized nano/micro structured metal oxides are finding applications in microfluidics, optical sensors, electrochemical sensors, DNA-based biosensing, imaging, diagnosis and analysis, this book provides a comprehensive update on the topic. Additional sections cover research challenges, technology limitations, and future trends in metal oxides and their composites regarding their usage in biomedical applications. © 2021 Elsevier Inc. All rights reserved.
Ozone sensing by In2O3 films modified with rh: Dimension effect [Articol]
(MDPI, 2021) Korotcenkov, Ghenadii; Nehasil, Vaclav
We considered the effect of coverage of the surface of In2O3 films with rhodium on the sensitivity of their electrophysical properties to ozone (1 ppm). The surface coverage with rhodium varied in the range of 0–0.1 ML. The In2O3 films deposited by spray pyrolysis had a thickness of 40–50 nm. The sensor response to ozone depends on the degree of rhodium coverage. This dependence has a pronounced maximum at a coverage of ~0.01 ML of Rh. An explanation is given for this effect. It is concluded that the observed changes are associated with the transition from the atomically dispersed state of rhodium to a 3D cluster state.
Plasma treatment and surface sensibilization of tin dioxide films for enhancement of gas sensitivity [Articol]
(2005) Brînzari, Vladimir; Dmitriev, Serghei; Korotcenkov, Ghenadii
This paper presents result of investigation aimed at the improvement of gas sensitive properties of SnO2 thin film gas sensors (TFGS) by means of high frequency (HF) oxygen plasma treatment and its surface doping. Used in experiments SnO2 films were deposited by spray pyrolysis method. It is shown that plasma treatment provides 3-4 times growth of thin film gas sensitivity. Surface doping of SnO2 films with Pd leads to gas sensitivity increasing by order. It is conluded that combination of HF oxygen plasma treatment and surface sensibilization through surface doping is an effective way to considerable improvement of gas sensitive properties of tin dioxide based TFGS.
The role of Rh dispersion in gas sensing effects observed in SnO2 thin films [Articol]
(Elsevier, 2019) Korotcenkov, Ghenadii; Nehasil, V.
In the present work the effect of surface modification by rhodium on the conductivity response of the SnO2 films to reducing gases such as CO and H2 and oxidizing gas ozone was analyzed. SnO2 films, subjected to surface modification, were deposited by spray pyrolysis, while Rh was deposited using a micro electron beam evaporation. The thickness of the Rh coating varied in the range of 0–0.1 ML. It was found that there is an optimal thickness of Rh, which gives an improvement in the sensor response and a decrease in the recovery time. An explanation of the observed effects was proposed. It was assumed that the atomically dispersed state of rhodium is most active in gas–sensing effects. The transformation from the atomic state to the cluster state reduces the efficiency of the surface functionalization of SnO2 with rhodium.
Senzorii de gaz și rolul lor în industrie, agricultură, medicină și monitorizarea mediului [Articol]
(Academia de Ştiinţe a Moldovei, 2019) Korotcenkov, Ghenadii
It has been shown that gas sensors make it possible to organize effective monitoring of living and working conditions, the state of the atmosphere, the quality of food, the condition of patients and the burning conditions. Gas sensors also play a significant role in organizing security systems and combating terrorism. All this stimulates intensive research in this area.
Theoretical bases of the operation of nanoscale semiconducting gas sensors on the example of tin dioxide [Articol]
(CEP USM, 2019) Brînzari, Vladimir; Korotcenkov, Ghenadii; Damaschin, Ion
Thermal transport evolution due to nanostructural transformations in Ga-doped indium-tin-oxide thin films [Articol]
(MDPI, 2021) Brinzari, Vladimir; Jeong, Do-Gyeom; Korotcenkov, Ghenadii; Vatavu, Sergiu; Lee, Jong S.; Nika, Denis; Cocemasov, Alexandr
We report on a comprehensive theoretical and experimental investigation of thermal conductivity in indium-tin-oxide (ITO) thin films with various Ga concentrations (0–30 at. %) deposited by spray pyrolysis technique. X-ray diffraction (XRD) and scanning electron microscopy have shown a structural transformation in the range 15–20 at. % Ga from the nanocrystalline to the amorphous phase. Room temperature femtosecond time domain thermoreflectance measurements showed nonlinear decrease of thermal conductivity in the range 2.0–0.5 Wm−1 K−1 depending on Ga doping level. It was found from a comparison between density functional theory calculations and XRD data that Ga atoms substitute In atoms in the ITO nanocrystals retaining Ia-3 space group symmetry. The calculated phonon dispersion relations revealed that Ga doping leads to the appearance of hybridized metal atom vibrations with avoided-crossing behavior. These hybridized vibrations possess shortened mean free paths and are the main reason behind the thermal conductivity drop in nanocrystalline phase. An evolution from propagative to diffusive phonon thermal transport in ITO:Ga with 15–20 at. % of Ga was established. The suppressed thermal conductivity of ITO:Ga thin films deposited by spray pyrolysis may be crucial for their thermoelectric applications.
Thermal transport evolution due to nanostructural transformations in ga-doped indium-tin-oxide thin films [Articol]
(2021) Cocemasov, Alexandr; Brinzari, Vladimir; Jeong, Do-Gyeom; Korotcenkov, Ghenadii; Lee, Jong S.; Nika, Denis L.
We report on a comprehensive theoretical and experimental investigation of thermal con- ductivity in indium-tin-oxide (ITO) thin films with various Ga concentrations (0–30 at. %) deposited by spray pyrolysis technique. X-ray diffraction (XRD) and scanning electron microscopy have shown a structural transformation in the range 15–20 at. % Ga from the nanocrystalline to the amorphous phase. Room temperature femtosecond time domain thermoreflectance measurements showed nonlinear decrease of thermal conductivity in the range 2.0–0.5 Wm−1 K−1 depending on Ga doping level. It was found from a comparison between density functional theory calculations and XRD data that Ga atoms substitute In atoms in the ITO nanocrystals retaining Ia-3 space group symmetry. The calculated phonon dispersion relations revealed that Ga doping leads to the appearance of hybridized metal atom vibrations with avoided-crossing behavior. These hybridized vibrations possess shortened mean free paths and are the main reason behind the thermal conductivity drop in nanocrystalline phase. An evolution from propagative to diffusive phonon thermal transport in ITO:Ga with 15–20 at. % of Ga was established. The suppressed thermal conductivity of ITO:Ga thin films deposited by spray pyrolysis may be crucial for their thermoelectric applications.
XPS study of Rh/In2O3 system [Articol]
(Elsevier, 2021) Korotcenkov, Ghenadii; Brinzari, Vladimir; Nehasil, Vaclav
The effect of surface modification of In2O3 films by rhodium atoms deposited by electron beam sputtering on the XP spectra is considered. The surface coverage with rhodium ranged from 0 to 0.1 ML. It was shown that the main changes in the XP spectra occur in the Rh3d region and are caused by the dimensional effect of rhodium particles. With an increase in the surface coverage with rhodium, Rh particles grow from an atomically dispersed state to relatively large clusters. As the particle size increases, its electronic structure tends to approach the state corresponding to the bulk Rh. Such a process is accompanied by a decrease in BE Rh3d5/2 by 0.3–0.6 eV, which behaviour depends on the surface structure of the used In2O3 films.