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Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020)

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 39122

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Prof. Dr. Katarzyna Zakrzewska

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Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow, Poland
Interests: solid-state physics; thin films; materials science; chemical engineering; renewable energy; chemical sensors

Prof. Dr. Artur M. Rydosz

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Guest Editor

Insitute of Electronics, AGH University of Science and Technology, 30-059 Krakow, Poland
Interests: metal oxide thin films; nanomaterials; gas sensors; acetone detection; exhaled breath analysis
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Special Issue Information

Dear Colleagues,

The 16^th International Conference on Electronic and Optical Sensors, COE’2020, could not have taken place as planned in spring of 2020 due to the unexpected development of the COVID-19 pandemic. However, this Special Issue already includes seven papers related to the research, the results of which were supposed to be presented during the event, which was regretfully canceled.

Eventually, it was possible to arrange a three-day online COE’2020 international meeting on from 27 to 29 September 2021, with more than a hundred participants from 11 countries. Eight fascinating plenary lectures were delivered by distinguished scientists, namely Elisabetta Comini (Italy), Rupert Schreiner (Germany), Lars Österlund (Sweden), Don N. Futaba (Japan), Susana Cardoso de Freitas (Portugal), Bilge Saruhan-Brings (Germany), Marcel Bouvet (France), and Eduard Llobet (Spain). The program of the conference offered 52 oral presentations including 21 invited talks. Three contributions from young speakers—Bartosz Dzikowski (Warsaw University of Technology), Bartosz Kawa (Wroclaw University of Science and Technology), and Julia Mazurków (AGH UST, Krakow)—have been awarded. The conference was sponsored by the Polish Ministry of Education and Science, MEN, within the framework of the Excellent Science (Doskonała Nauka, DNK/SP/462114/2020) project. Six companies—Prevac, Elsta Elektronika, EV Group, Vakpol, OEM Automatic, and Radionika—have supported the conference since its beginning.

The 16th International Conference on Optical and Electronic Sensors, COE’2020, was organized by three faculties of AGH University of Science and Technology, Kraków, Poland: Computer Science, Electronics and Telecommunications; Materials Science and Ceramics; and Electrical Engineering, Automatics, Computer Science and Biomedical Engineering. The President of AGH UST, JM Rector prof. dr. hab. inż. Jerzy Lis, has granted his honorary patronage and became the Chair of the Honorary Committee of this event.

The conference has a long tradition dating back to 1990 when the first COE was initiated by the sensor community in Poland under auspices of the Polish Sensor Society, PTTS. Since 2014, COE has attained the status of an international conference. Two past COE conferences were hosted by Gdansk University of Technology in 2016 and Warsaw University of Technology in 2018.

The scope of the conference covered the most important issues: new sensor materials; nanosensors; nano- and micro-systems, including MEMS, MOEMS, RF MEMS, and NEMS; sensor networks; biosensors and lab-on-chip devices; semiconducting and electrochemical gas sensors; optical and magnetic sensors; sensors of physical quantities; the theory and modelling of sensing behavior; and the application of sensors, especially in medicine as well as in emerging topics such as wearable electronics, the Internet of Things (IoT), and the Internet of Energy (IoE).

On the behalf of the Scientific Committee, International Advisory Board, and the Technical Committee of COE’2020, I kindly invite you to submit the manuscripts devoted to the results of your current research to this Special Issue of Sensors.

Prof. Dr. Katarzyna Zakrzewska
Prof. Dr. Artur M. Rydosz
Guest Editors

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Published Papers (12 papers)

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Research

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17 pages, 2844 KiB

Open AccessArticle

A Robust Miniaturized Gas Sensor for H₂ and CO₂ Detection Based on the 3ω Method

by Dominik Berndt, Josef Muggli, Robert Heckel, Mohd Fuad Rahiman, Matthias Lindner, Stephan Heinrich, Heinz Plöchinger and Rupert Schreiner

Sensors 2022, 22(2), 485; https://0-doi-org.brum.beds.ac.uk/10.3390/s22020485 - 09 Jan 2022

Cited by 6 | Viewed by 2911

Abstract

Gas concentration monitoring is essential in industrial or life science areas in order to address safety-relevant or process-related questions. Many of the sensors used in this context are based on the principle of thermal conductivity. The $3 ω$ -method is a very accurate method to determine the thermal properties of materials. It has its origin in the thermal characterization of thin solid films. To date, there have been very few scientific investigations using this method to determine the thermal properties of gases and to apply it to gas measurement technology. In this article, we use two exemplary gases (

H_{2}

and

C O_{2}

) for a systematical investigation of this method in the context of gas analysis. To perform our experiments, we use a robust, reliable sensing element that is already well established in vacuum measurement technology. This helix-shaped thin wire of tungsten exhibits high robustness against chemical and mechanical influences. Our setup features a compact measurement environment, where sensor operation and data acquisition are integrated into a single device. The experimental results show a good agreement with a simplified analytical model and FEM simulations. The sensor exhibits a lower detection limit of 0.62% in the case of

C O_{2}

, and only 0.062% in case the of

H_{2}

at an excitation frequency of 1

Hz

. This is one of the lowest values reported in literature for thermal conductivity

H_{2}

sensors. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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16 pages, 3048 KiB

Open AccessArticle

Electrochemical Characterization of Modified Glassy Carbon Electrodes for Non-Enzymatic Glucose Sensors

by Julia Maria Mazurków, Anna Kusior and Marta Radecka

Sensors 2021, 21(23), 7928; https://0-doi-org.brum.beds.ac.uk/10.3390/s21237928 - 27 Nov 2021

Cited by 6 | Viewed by 3212

Abstract

The diversity of materials proposed for non-enzymatic glucose detection and the lack of standardized protocols for assessing sensor performance have caused considerable confusion in the field. Therefore, methods for pre-evaluation of working electrodes, which will enable their conscious design, are currently intensively sought. Our approach involved comprehensive morphologic and structural characterization of copper sulfides as well as drop-casted suspensions based on three different polymers—cationic chitosan, anionic Nafion, and nonionic polyvinylpyrrolidone (PVP). For this purpose, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were applied. Subsequently, comparative studies of electrochemical properties of bare glassy carbon electrode (GCE), polymer- and copper sulfides/polymer-modified GCEs were performed using electrochemical impedance spectroscopy (EIS) and voltammetry. The results from EIS provided an explanation for the enhanced analytical performance of Cu-PVP/GCE over chitosan- and Nafion-based electrodes. Moreover, it was found that the pH of the electrolyte significantly affects the electrocatalytic behavior of copper sulfides, indicating the importance of OH_ads in the detection mechanism. Additionally, diffusion was denoted as a limiting step in the irreversible electrooxidation process that occurs in the proposed system. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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9 pages, 2145 KiB

Open AccessCommunication

Method of Step Detection and Counting Based on Measurements of Magnetic Field Variations

by Patryk Łaś and Piotr Wiśniowski

Sensors 2021, 21(23), 7775; https://0-doi-org.brum.beds.ac.uk/10.3390/s21237775 - 23 Nov 2021

Cited by 1 | Viewed by 2471

Abstract

Basic human activity recognition (HAR) and analysis is becoming a key aspect of tracking and identifying daily habits that can have a critical impact on healthy lifestyles by providing feedback on health status and warning of deterioration. However, current approaches for detecting basic activities such as movements or steps rely on solutions with multiple sensors which affect their size and power consumption. In this paper, we propose a novel method that uses only a single magnetic field sensor for basic step detection, unlike the well-known multisensory solutions. The approach presented here is based on real-time analysis of magnetic field sensor measurements to detect and count steps during a walking activity. The approach is implemented in a system that integrates a digital magnetic field sensor with software blocks: filter, steady state detector, extrema detector with classifier, and threshold comparator implemented in an embedded platform. Outdoor experiments with volunteers of different ages and genders walking at variable speeds showed that the proposed detection method achieves up to 98% accuracy in step detection. The obtained results show that a single magnetic field sensor can be used to detect steps, and in general offers the possibility of simplifying the current solutions by reducing the device dimensions, the cost of a system and its power consumption. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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14 pages, 3751 KiB

Open AccessArticle

Mode Sensitivity Exploration of Silica–Titania Waveguide for Refractive Index Sensing Applications

by Muhammad A. Butt, Andrzej Kaźmierczak, Cuma Tyszkiewicz, Paweł Karasiński and Ryszard Piramidowicz

Sensors 2021, 21(22), 7452; https://0-doi-org.brum.beds.ac.uk/10.3390/s21227452 - 09 Nov 2021

Cited by 13 | Viewed by 1880

Abstract

In this paper, a novel and cost-effective photonic platform based on silica–titania material is discussed. The silica–titania thin films were grown utilizing the sol–gel dip-coating method and characterized with the help of the prism-insertion technique. Afterwards, the mode sensitivity analysis of the silica–titania ridge waveguide is investigated via the finite element method. Silica–titania waveguide systems are highly attractive due to their ease of development, low fabrication cost, low propagation losses and operation in both visible and near-infrared wavelength ranges. Finally, a ring resonator (RR) sensor device was modelled for refractive index sensing applications, offering a sensitivity of 230 nm/RIU, a figure of merit (FOM) of 418.2 RIU⁻¹, and Q-factor of 2247.5 at the improved geometric parameters. We believe that the abovementioned integrated photonics platform is highly suitable for high-performance and economically reasonable optical sensing devices. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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13 pages, 3647 KiB

Open AccessCommunication

Nitrogen Dioxide Sensing Using Multilayer Structure of Reduced Graphene Oxide and α-Fe₂O₃

by Tadeusz Pisarkiewicz, Wojciech Maziarz, Artur Małolepszy, Leszek Stobiński, Dagmara Agnieszka Michoń, Aleksandra Szkudlarek, Marcin Pisarek, Jarosław Kanak and Artur Rydosz

Sensors 2021, 21(3), 1011; https://0-doi-org.brum.beds.ac.uk/10.3390/s21031011 - 02 Feb 2021

Cited by 10 | Viewed by 2841

Abstract

Multilayers consisting of graphene oxide (GO) and α-Fe₂O₃ thin layers were deposited on the ceramic substrates by the spray LbL (layer by layer) coating technique. Graphene oxide was prepared from graphite using the modified Hummers method. Obtained GO flakes reached up to 6 nanometers in thickness and 10 micrometers in lateral size. Iron oxide Fe₂O₃ was obtained by the wet chemical method from FeCl₃ and NH₄OH solution. Manufactured samples were deposited as 3 LbL (GO and Fe₂O₃ layers deposited sequentially) and 6 LbL structures with GO as a bottom layer. Electrical measurements show the decrease of multilayer resistance after the introduction of the oxidizing NO₂ gas to the ambient air atmosphere. The concentration of NO₂ was changed from 1 ppm to 20 ppm. The samples changed their resistance even at temperatures close to room temperature, however, the sensitivity increased with temperature. Fe₂O₃ is known as an n-type semiconductor, but the rGO/Fe₂O₃ hybrid structure behaved similarly to rGO, which is p-type. Both chemisorbed O₂ and NO₂ act as electron traps decreasing the concentration of electrons and increasing the effective multilayer conductivity. An explanation of the observed variations of multilayer structure resistance also the possibility of heterojunctions formation was taken into account. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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17 pages, 5394 KiB

Open AccessArticle

Nonenzymatic Glucose Sensors Based on Copper Sulfides: Effect of Binder-Particles Interactions in Drop-Casted Suspensions on Electrodes Electrochemical Performance

by Julia Mazurków, Anna Kusior and Marta Radecka

Sensors 2021, 21(3), 802; https://0-doi-org.brum.beds.ac.uk/10.3390/s21030802 - 26 Jan 2021

Cited by 11 | Viewed by 2669

Abstract

The constant progress in novel nanomaterials synthesis has contributed to the rapid development of nonenzymatic glucose sensors. For working electrodes preparation, drop casting proved to be the most convenient and thus most widely applied method. However, appropriate interpretation of obtained electrochemical signal requires in-depth knowledge of limitations related to this technique. In this study, we prepared solutions based on commonly reported polymers for nanostructures immobilization and investigated their influence on copper sulfides distribution on the electrode. Characterization of suspensions properties and behavior of particles during droplet drying revealed that nonionic polyvinylpyrrolidone (PVP) was favorable for electrodes modification with copper sulfides in comparison with Nafion and chitosan. It ensured homogeneity of the suspension as well as the uniform coverage of the electrode surface with particles, what resulted in increased active surface area and, therefore, higher signal from glucose addition. On the other hand, when cationic chitosan was used as a binder, suspensions were agglomerated and, within dry deposits, a coffee-ring effect was observed. Appropriate adjustment of material and polymer interactions led to enhanced electrode electrochemical performance. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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17 pages, 1747 KiB

Open AccessArticle

Sensors in the Autoclave-Modelling and Implementation of the IoT Steam Sterilization Procedure Counter

by Lukas Boehler, Mateusz Daniol, Ryszard Sroka, Dominik Osinski and Anton Keller

Sensors 2021, 21(2), 510; https://0-doi-org.brum.beds.ac.uk/10.3390/s21020510 - 13 Jan 2021

Cited by 1 | Viewed by 5032

Abstract

Surgical procedures involve major risks, as pathogens can enter the body unhindered. To prevent this, most surgical instruments and implants are sterilized. However, ensuring that this process is carried out safely and according to the normative requirements is not a trivial task. This study aims to develop a sensor system that can automatically detect successful steam sterilization on the basis of the measured temperature profiles. This can be achieved only when the relationship between the temperature on the surface of the tool and the temperature at the measurement point inside the tool is known. To find this relationship, the thermodynamic model of the system has been developed. Simulated results of thermal simulations were compared with the acquired temperature profiles to verify the correctness of the model. Simulated temperature profiles are in accordance with the measured temperature profiles, thus the developed model can be used in the process of further development of the system as well as for the development of algorithms for automated evaluation of the sterilization process. Although the developed sensor system proved that the detection of sterilization cycles can be automated, further studies that address the possibility of optimization of the system in terms of geometrical dimensions, used materials, and processing algorithms will be of significant importance for the potential commercialization of the presented solution. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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20 pages, 7968 KiB

Open AccessArticle

SnO₂/TiO₂ Thin Film n-n Heterostructures of Improved Sensitivity to NO₂

by Piotr Nowak, Wojciech Maziarz, Artur Rydosz, Kazimierz Kowalski, Magdalena Ziąbka and Katarzyna Zakrzewska

Sensors 2020, 20(23), 6830; https://0-doi-org.brum.beds.ac.uk/10.3390/s20236830 - 29 Nov 2020

Cited by 13 | Viewed by 2750

Abstract

Thin-film n-n nanoheterostructures of SnO₂/TiO₂, highly sensitive to NO₂, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO₂ base layers were deposited by MS and subsequently overcoated with a thin and discontinuous TiO₂ film by means of L–B. Rutile nanopowder spread over the ethanol/chloroform/water formed a suspension, which was used as a source in L–B method. The morphology, crystallographic and electronic properties of the prepared sensors were studied by scanning electron microscopy, SEM, X-ray diffraction, XRD in glancing incidence geometry, GID, X-ray photoemission spectroscopy, XPS, and uv-vis-nir spectrophotometry, respectively. It was found that amorphous SnO₂ films responded to relatively low concentrations of NO₂ of about 200 ppb. A change of more than two orders of magnitude in the electrical resistivity upon exposure to NO₂ was further enhanced in SnO₂/TiO₂ n-n nanoheterostructures. The best sensor responses R_NO2/R₀ were obtained at the lowest operating temperatures of about 120 °C, which is typical for nanomaterials. Response (recovery) times to 400 ppb NO₂ were determined as a function of the operating temperature and indicated a significant decrease from 62 (42) s at 123 °C to 12 (19) s at 385 °C A much smaller sensitivity to H₂ was observed, which might be advantageous for selective detection of nitrogen oxides. The influence of humidity on the NO₂ response was demonstrated to be significantly below 150 °C and systematically decreased upon increase in the operating temperature up to 400 °C. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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14 pages, 3056 KiB

Open AccessArticle

Modeling and Implementation of TEG-Based Energy Harvesting System for Steam Sterilization Surveillance Sensor Node

by Mateusz Daniol, Lukas Boehler, Ryszard Sroka and Anton Keller

Sensors 2020, 20(21), 6338; https://0-doi-org.brum.beds.ac.uk/10.3390/s20216338 - 06 Nov 2020

Cited by 6 | Viewed by 2330

Abstract

The aim of this work is a proof of concept, that medical Internet of Things (IoT) sterilization surveillance sensors can be powered by using the heat during a steam sterilization procedure. Hereby, the focus was on the use of thermo-electrical generators (TEG) to generate enough power for an ultra-low-power sensor application. Power generation requirement of the sensor was 1.6 mW over the single sterilization cycle. The thermal gradient across the TEG has been achieved using a highly efficient aerogel-foam-based thermal insulation, shielding a heat storage unit (HSU), connected to one side of the TEG. The evaluation of the developed system was carried out with thermal and electrical simulations based on the parameters extracted from the TEG manufacturer’s datasheet. The developed model has been validated with a real prototype using the thermal step response method. It was important for the authors to focus on rapid-prototyping and using off-the-shelf devices and materials. Based on comparison with the physical prototype, the SPICE model was adjusted. With a thermal gradient of 12 °C, the simulated model generated over 2 mW of power. The results show that a significant power generation with this system is possible and usable for sensor applications in medial IoT. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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16 pages, 4130 KiB

Open AccessArticle

High-Temperature Hydrogen Sensing Performance of Ni-Doped TiO₂ Prepared by Co-Precipitation Method

by Roussin Lontio Fomekong, Klemens Kelm and Bilge Saruhan

Sensors 2020, 20(21), 5992; https://0-doi-org.brum.beds.ac.uk/10.3390/s20215992 - 22 Oct 2020

Cited by 19 | Viewed by 2785

Abstract

This work deals with the substantially high-temperature hydrogen sensors required by combustion and processing technologies. It reports the synthesis of undoped and Ni-doped TiO₂ (with 0, 0.5, 1 and 2 mol.% of Ni) nanoparticles by a co-precipitation method and the obtained characteristics applicable for this purpose. The effect of nickel doping on the morphological variation, as well as on the phase transition from anatase to rutile, of TiO₂ was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The resistive sensors prepared with these powders were tested toward H₂ at 600 °C. The results indicate that 0.5% Ni-doped TiO₂ with almost equal amounts of anatase and rutile shows the best H₂ sensor response (ΔR/R0 = 72%), response rate and selectivity. The significant improvement of the sensing performance of 0.5% Ni-doped TiO₂ is mainly attributed to the formation of the highest number of n-n junctions present between anatase and rutile, which influence the quantity of adsorbed oxygen (i.e., the active reaction site) on the surface and the conductivity of the material. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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17 pages, 3463 KiB

Open AccessArticle

CuO-Ga₂O₃ Thin Films as a Gas-Sensitive Material for Acetone Detection

by Katarzyna Dyndal, Arkadiusz Zarzycki, Wojciech Andrysiewicz, Dominik Grochala, Konstanty Marszalek and Artur Rydosz

Sensors 2020, 20(11), 3142; https://0-doi-org.brum.beds.ac.uk/10.3390/s20113142 - 02 Jun 2020

Cited by 18 | Viewed by 3622

Abstract

The p-n heterostructures of CuO-Ga₂O₃ obtained by magnetron sputtering technology in a fully reactive mode (deposition in pure oxygen) were tested under exposure to low acetone concentrations. After deposition, the films were annealed at previously confirmed conditions (400 °C/4 h/synthetic air) and further investigated by utilization of X-ray diffraction (XRD), X-ray reflectivity (XRR), energy-dispersive X-ray spectroscopy (EDS). The gas-sensing behavior was tested in the air/acetone atmosphere in the range of 0.1–1.25 ppm, as well as at various relative humidity (RH) levels (10–85%). The highest responses were obtained for samples based on the CuO-Ga₂O₃ (4% at. Ga). Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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Review

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25 pages, 9112 KiB

Open AccessReview

MXene Heterostructures as Perspective Materials for Gas Sensing Applications

by Svitlana Nahirniak and Bilge Saruhan

Sensors 2022, 22(3), 972; https://0-doi-org.brum.beds.ac.uk/10.3390/s22030972 - 27 Jan 2022

Cited by 26 | Viewed by 5248

Abstract

This paper provides a summary of the recent developments with promising 2D MXene-related materials and gives an outlook for further research on gas sensor applications. The current synthesis routes that are provided in the literature are summarized, and the main properties of MXene compounds have been highlighted. Particular attention has been paid to safe and non-hazardous synthesis approaches for MXene production as 2D materials. The work so far on sensing properties of pure MXenes and MXene-based heterostructures has been considered. Significant improvement of the MXenes sensing performances not only relies on 2D production but also on the formation of MXene heterostructures with other 2D materials, such as graphene, and with metal oxides layers. Despite the limited number of research papers published in this area, recommendations on new strategies to advance MXene heterostructures and composites for gas sensing applications can be driven. Full article

(This article belongs to the Special Issue Selected Papers from 16th International Conference on Optical and Electronic Sensors (COE 2020))

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