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Understanding Gas Sensors Based on Semiconducting Metal Oxides by using Spectroscopic Techniques

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Special Issue Information
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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Chemical Sensors".

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 22131

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Special Issue Editors

Dr. Nicolae Barsan

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Guest Editor

Group Head-Weimar Group, Institute of Physical and Theoretical Chemistry, Eberhard Karls University of Tübingen, 72076 Tuebingen, Germany
Interests: DRIFT spectroscopy; Kelvin probe measurements; SMOX gas sensors; transduction and reception functions
Special Issues, Collections and Topics in MDPI journals

Dr. David Degler

E-Mail Website
Guest Editor

Electronic Structure, Magnetism and Dynamics Group (EMD Group), Experiments Division, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043 Grenoble, France
Interests: gas sensors and sensor technology; spectroscopy; surface chemistry; operando techniques; synthesis-structure-function-relationships

Special Issue Information

Dear Colleagues,

The development of gas sensors based on semiconducting metal oxides (SMOX) has achieved an unprecedented level, which is largely based on the more and more detailed understanding of the relationship of structural properties and the gas sensing performance (structure-function-relationships). Electronic characterization methods as well as various microscopies and spectroscopic techniques have contributed to this development. In particular spectroscopic techniques became increasingly important not only providing ex-situ information on countless material properties. Today various techniques allow studying sensing materials under realistic conditions (in-situ) or actual gas sensors during operation (operando).
The various spectroscopic techniques utilizing radiation from radio waves to hard x-rays or gamma radiation as well as electrons allow characterizing the materials’ structures and electrical properties as well as in determining the surface processes. Furthermore, mass spectrometry is an essential technique used to characterize solid materials or their chemical properties. The information obtained from these methods provides new and deep insights in the fundamental material properties and processes, which determine the gas sensing properties of SMOX materials, and, thus, enables establishing structure-function-relationships, which provide the basis for the knowledge-based design of highly sensitive, selective and stable SMOX gas sensing material.

This special issue of Sensors aims to provide an overview of all state-of-the-art spectroscopic techniques and related methods used to study gas sensors, highlighting the specific information, which is probed by a specific technique. Accordingly, you are invited to submit contributions focusing on the utilization of spectroscopic techniques to characterize SMOX based gas sensing materials and gas sensors. We would gladly welcome manuscripts coming from industry.

Dr. Nicolae Barsan
Dr. David Degler
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

metal oxides
gas sensors
spectroscopy
characterization techniques
material properties

Published Papers (5 papers)

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Research

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21 pages, 4605 KiB

Open AccessFeature PaperArticle

Spectroscopic Understanding of SnO₂ and WO₃ Metal Oxide Surfaces with Advanced Synchrotron Based; XPS-UPS and Near Ambient Pressure (NAP) XPS Surface Sensitive Techniques for Gas Sensor Applications under Operational Conditions

by Engin Ciftyürek, Břetislav Šmíd, Zheshen Li, Vladimír Matolín and Klaus Schierbaum

Sensors 2019, 19(21), 4737; https://doi.org/10.3390/s19214737 - 31 Oct 2019

Cited by 42 | Viewed by 5749

Abstract

The most promising and utilized chemical sensing materials, WO₃ and SnO₂ were characterized by means advanced synchrotron based XPS, UPS, NAP-XPS techniques. The complementary electrical resistance and sensor testing experiments were also completed. A comparison and evaluation of some of the prominent and newly employed spectroscopic characterization techniques for chemical sensors were provided. The chemical nature and oxidation state of the WO₃ and SnO₂ thin films were explored at different depths from imminent surface to a maximum of 1.5 nm depth from the surface with non-destructive depth profiling. The adsorption and amount of chemisorbed oxygen species were precisely analyzed and quantified as a function of temperature between 25–400 °C under realistic operating conditions for chemical sensors employing 1–5 mbar pressures of oxygen (O₂) and carbon monoxide (CO). The effect of realistic CO and O₂ gas pressures on adsorbed water (H₂O), OH⁻ groups and chemisorbed oxygen species (

O_{2 (a d s)}^{-}, O_{(a d s),}^{-} O_{2 (a d s)}^{2 -}

) and chemical stability of metal oxide surfaces were evaluated and quantified. Full article

(This article belongs to the Special Issue Understanding Gas Sensors Based on Semiconducting Metal Oxides by using Spectroscopic Techniques)

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15 pages, 3173 KiB

Open AccessArticle

by Lili Yang, Artem Marikutsa, Marina Rumyantseva, Elizaveta Konstantinova, Nikolay Khmelevsky and Alexander Gaskov

Sensors 2019, 19(15), 3405; https://doi.org/10.3390/s19153405 - 03 Aug 2019

Cited by 30 | Viewed by 3549

Abstract

Tungsten oxide is a renowned material for resistive type gas sensors with high sensitivity to nitrogen oxides. Most studies have been focused on sensing applications of WO₃ for the detection of NO₂ and a sensing mechanism has been established. However, less is known about NO sensing routes. There is disagreement on whether NO is detected as an oxidizing or reducing gas, due to the ambivalent redox behavior of nitric oxide. In this work, nanocrystalline WO₃ with different particle size was synthesized by aqueous deposition of tungstic acid and heat treatment. A high sensitivity to NO₂ and NO and low cross-sensitivities to interfering gases were established by DC-resistance measurements of WO₃ sensors. Both nitrogen oxides were detected as the oxidizing gases. Sensor signals increased with the decrease of WO₃ particle size and had similar dependence on temperature and humidity. By means of in situ infrared (DRIFT) spectroscopy similar interaction routes of NO₂ and NO with the surface of tungsten oxide were unveiled. Analysis of the effect of reaction conditions on sensor signals and infrared spectra led to the conclusion that the interaction of WO₃ surface with NO was independent of gas-phase oxidation to NO₂. Full article

(This article belongs to the Special Issue Understanding Gas Sensors Based on Semiconducting Metal Oxides by using Spectroscopic Techniques)

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19 pages, 4244 KiB

Open AccessArticle

The Influence of Nb on the Synthesis of WO₃ Nanowires and the Effects on Hydrogen Sensing Performance

by Dario Zappa

Sensors 2019, 19(10), 2332; https://doi.org/10.3390/s19102332 - 20 May 2019

Cited by 13 | Viewed by 3564

Abstract

Hydrogen sensing is becoming one of the hottest topics in the chemical sensing field, due to its wide number of applications and the dangerousness of hydrogen leakages. For this reason, research activities are focusing on the development of high-performance materials that can be easily integrated in sensing devices. In this work, we investigated the influence of Nb on the sensing performances of WO₃ nanowires (NWs) synthetized by a low-cost thermal oxidation method. The morphology and the structure of these Nb-WO₃ nanowires were investigated by field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Raman and X-ray photoelectron (XPS) spectroscopies, confirming that the addition of Nb does not modify significantly the monoclinic crystal structure of WO₃. Moreover, we integrated these NWs into chemical sensors, and we assessed their performances toward hydrogen and some common interfering compounds. Although the hydrogen sensing performances of WO₃ nanowires were already excellent, thanks to the presence of Nb they have been further enhanced, reaching the outstanding value of more than 80,000 towards 500 ppm @ 200 °C. This opens the possibility of their integration in commercial equipment, like electronic noses and portable devices. Full article

(This article belongs to the Special Issue Understanding Gas Sensors Based on Semiconducting Metal Oxides by using Spectroscopic Techniques)

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Review

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17 pages, 5546 KiB

Open AccessReview

Application of Raman Spectroscopy to Working Gas Sensors: From in situ to operando Studies

by Ann-Kathrin Elger and Christian Hess

Sensors 2019, 19(23), 5075; https://doi.org/10.3390/s19235075 - 20 Nov 2019

Cited by 22 | Viewed by 4603

Abstract

Understanding the mode of operation of gas sensors is of great scientific and economic interest. A knowledge-based approach requires the development and application of spectroscopic tools to monitor the relevant surface and bulk processes under working conditions (operando approach). In this review we trace the development of vibrational Raman spectroscopy applied to metal-oxide gas sensors, starting from initial applications to very recent operando spectroscopic approaches. We highlight the potential of Raman spectroscopy for molecular-level characterization of metal-oxide gas sensors to reveal important mechanistic information, as well as its versatility regarding the design of in situ/operando cells and the combination with other techniques. We conclude with an outlook on potential future developments. Full article

(This article belongs to the Special Issue Understanding Gas Sensors Based on Semiconducting Metal Oxides by using Spectroscopic Techniques)

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13 pages, 3109 KiB

Open AccessReview

Trends and Advances in the Characterization of Gas Sensing Materials Based on Semiconducting Oxides

by David Degler

Sensors 2018, 18(10), 3544; https://doi.org/10.3390/s18103544 - 19 Oct 2018

Cited by 28 | Viewed by 4142

Abstract

The understanding of the fundamental properties and processes of chemoresistive gas sensors based on semiconducting metal oxides is driven by the available characterization techniques and sophisticated approaches used to identify structure-function-relationships. This article summarizes trends and advances in the characterization of gas sensing materials based on semiconducting metal oxides, giving a unique overview of the state of the art methodology used in this field. The focus is set on spectroscopic techniques, but the presented concepts apply to other characterization methods, such as electronic, imaging or diffraction-based techniques. The presented concepts are relevant for academic research as well as for improving R&D approaches in industry. Full article

(This article belongs to the Special Issue Understanding Gas Sensors Based on Semiconducting Metal Oxides by using Spectroscopic Techniques)

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