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Special Issue "Functional Materials for the Applications of Advanced Gas Sensors"

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

Deadline for manuscript submissions: closed (28 February 2019)

Special Issue Editors

Guest Editor
Prof. Dr. Youichi Shimizu

Department of Applied Chemistry, Kyushu Institute of Technology, Japan
Website | E-Mail
Interests: gas sensors; solid electrolyte; ceramics device; electrochemical method; oxides
Guest Editor
Prof. Dr. Tetsuya Kida

Department of Applied Chemistry & Biochemistry, Kumamoto University, Japan
Website | E-Mail
Interests: gas sensors; nanocrystals; electrochemical devices; inorganic-organic hybrids; 2-D materials
Guest Editor
Prof. Dr. Geyu Lu

College of Electronic Science and Engineering, Jilin University, China
Website | E-Mail
Phone: +86-431-85167808
Interests: gas sensors; semiconductor oxides; solid electrolytes; nanomaterials; sensing electrodes

Special Issue Information

Dear Colleagues,

High-performance gas sensors are becoming very important in the fields of reactor control, environmental monitoring, and health care technology with gas monitoring, and as an interface for IoT. The use of functional materials, such as nano-powders and nano-films, are one of the new key points for developing high-performance gas sensors. This Special Issue is focused on “Functional Materials for the Applications of Advanced Gas Sensors”. It includes gas sensors based on new or functionally-developed materials, uniquely-designed materials, and so on. The topics include sensors using nanomaterials, nanoparticles, structure-controlled materials, sensor devices based on micro semiconductor, newly designed solid-electrolyte, new sensing methods with electrochemical detection, sensing system, smart system, and gas sensing for health, safety and security care. The MDPI journal, Sensors, is soliciting high-quality papers that document original and significant research works in “Sensors for Advanced Gas Sensors”. We welcome your participation and look forward to your contribution to this Special Issue.

Prof. Dr. Youichi Shimizu
Prof. Dr. Tetsuya Kida
Prof. Dr. Geyu Lu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 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

  • Semiconductor, Solid electrolyte, FET- based gas sensors
  • New transducers based on QCM, SAW, etc.
  • 1D- 2D- 3D- structured nano-materials Nanoparticles
  • Ceramics, Carbon-related materials
  • Other new sensing materials for health, safety and security care, and IoT

Published Papers (10 papers)

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Research

Open AccessArticle Waste Coffee Ground Biochar: A Material for Humidity Sensors
Sensors 2019, 19(4), 801; https://doi.org/10.3390/s19040801
Received: 20 December 2018 / Revised: 11 February 2019 / Accepted: 12 February 2019 / Published: 15 February 2019
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Abstract
Worldwide consumption of coffee exceeds 11 billion tons/year. Used coffee grounds end up as landfill. However, the unique structural properties of its porous surface make coffee grounds popular for the adsorption of gaseous molecules. In the present work, we demonstrate the use of [...] Read more.
Worldwide consumption of coffee exceeds 11 billion tons/year. Used coffee grounds end up as landfill. However, the unique structural properties of its porous surface make coffee grounds popular for the adsorption of gaseous molecules. In the present work, we demonstrate the use of coffee grounds as a potential and cheap source for biochar carbon. The produced coffee ground biochar (CGB) was investigated as a sensing material for developing humidity sensors. CGB was fully characterized by using laser granulometry, X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and the Brunnauer Emmett Teller (BET) technique in order to acquire a complete understanding of its structural and surface properties and composition. Subsequently humidity sensors were screen printed using an ink-containing CGB with polyvinyl butyral (PVB) acting as a temporary binder and ethylene glycol monobutyral ether, Emflow, as an organic vehicle so that the proper rheological characteristics were achieved. Screen-printed films were the heated at 300 °C in air. Humidity tests were performed under a flow of 1.7 L/min in the relative humidity range 0–100% at room temperature. The initial impedance of the film was 25.2 ± 0.15 MΩ which changes to 12.3 MΩ under 98% humidity exposure. A sensor response was observed above 20% relative humidity (RH). Both the response and recovery times were reasonably fast (less than 2 min). Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Improvement of Sensing Performance of Impedancemetric C2H2 Sensor Using SmFeO3 Thin-Films Prepared by a Polymer Precursor Method
Sensors 2019, 19(4), 773; https://doi.org/10.3390/s19040773
Received: 27 December 2018 / Revised: 3 February 2019 / Accepted: 8 February 2019 / Published: 13 February 2019
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Abstract
A sensitive an impedancemetric acetylene (C2H2) gas sensor device could be fabricated by using perovskite-type SmFeO3 thin-film as a sensor material. The uniform SmFeO3 thin-films were prepared by spin-coating and focusing on the effects of polymer precursor [...] Read more.
A sensitive an impedancemetric acetylene (C2H2) gas sensor device could be fabricated by using perovskite-type SmFeO3 thin-film as a sensor material. The uniform SmFeO3 thin-films were prepared by spin-coating and focusing on the effects of polymer precursor solutions. The prepared precursors and thin-films were characterized by means of thermal analysis, Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that particle growth and increase in homogeneity of the prepared thin-film could be accelerated by the addition of acetyl acetone (AcAc) as a coordination agent in the polymer precursor solution. Moreover, the highly crystallized thin-film-based sensor showed good response properties and stabilities to a low C2H2 concentration between 0.5 and 2.0 ppm. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Co3O4/Al-ZnO Nano-composites: Gas Sensing Properties
Sensors 2019, 19(4), 760; https://doi.org/10.3390/s19040760
Received: 31 December 2018 / Revised: 8 February 2019 / Accepted: 10 February 2019 / Published: 13 February 2019
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Abstract
In this paper, the gas sensing properties of metal oxide nano-powder composites are studied and modeled. The gas sensing properties of mixtures of two different metal oxide nanoparticles, prepared via low-cost routes, are investigated. The responses to both an oxidizing (NO2) [...] Read more.
In this paper, the gas sensing properties of metal oxide nano-powder composites are studied and modeled. The gas sensing properties of mixtures of two different metal oxide nanoparticles, prepared via low-cost routes, are investigated. The responses to both an oxidizing (NO2) and a reducing gas (CO) are analyzed. The tested composites are obtained by mixing a different percentage of a p-type metal oxide, Co3O4, with moderate responses to NO2 at about 200 °C and to CO at high temperature (above 260 °C), with n-type Al-doped ZnO, which is characterized by a large but unstable response towards NO2 around 160 °C and a moderate response towards CO around 200 °C. In the oxides mixtures, p-n heterojunctions are formed by the juxtaposition of an n-type and a p-type grain in contact. Consequently, the electronic conductivity is modified and the obtained composite materials show novel characteristics with respect to the base materials. This indicates that predicting the behavior of the composites from those of their components is not possible and it suggests that the hetero-junction behavior has to be studied to understand the sensing properties of the composite materials. The obtained results indicate that the composites containing a significant amount of hetero-junctions exhibit a stable response to NO2 at room temperature and significant responses towards CO at 160 °C. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Synthesis of Cu2O/CuO Nanocrystals and Their Application to H2S Sensing
Sensors 2019, 19(1), 211; https://doi.org/10.3390/s19010211
Received: 13 December 2018 / Revised: 28 December 2018 / Accepted: 7 January 2019 / Published: 8 January 2019
Cited by 2 | PDF Full-text (4648 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Semiconducting metal oxide nanocrystals are an important class of materials that have versatile applications because of their useful properties and high stability. Here, we developed a simple route to synthesize nanocrystals (NCs) of copper oxides such as Cu2O and CuO using [...] Read more.
Semiconducting metal oxide nanocrystals are an important class of materials that have versatile applications because of their useful properties and high stability. Here, we developed a simple route to synthesize nanocrystals (NCs) of copper oxides such as Cu2O and CuO using a hot-soap method, and applied them to H2S sensing. Cu2O NCs were synthesized by simply heating a copper precursor in oleylamine in the presence of diol at 160 °C under an Ar flow. X-ray diffractometry (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) results indicated the formation of monodispersed Cu2O NCs having approximately 5 nm in crystallite size and 12 nm in colloidal size. The conversion of the Cu2O NCs to CuO NCs was undertaken by straightforward air oxidation at room temperature, as confirmed by XRD and UV-vis analyses. A thin film Cu2O NC sensor fabricated by spin coating showed responses to H2S in dilute concentrations (1–8 ppm) at 50–150 °C, but the stability was poor because of the formation of metallic Cu2S in a H2S atmosphere. We found that Pd loading improved the stability of the sensor response. The Pd-loaded Cu2O NC sensor exhibited reproducible responses to H2S at 200 °C. Based on the gas sensing mechanism, it is suggested that Pd loading facilitates the reaction of adsorbed oxygen with H2S and suppresses the irreversible formation of Cu2S. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessFeature PaperArticle Selective Functionalization of High-Resolution Cu2O Nanopatterns via Galvanic Replacement for Highly Enhanced Gas Sensing Performance
Sensors 2018, 18(12), 4438; https://doi.org/10.3390/s18124438
Received: 21 November 2018 / Revised: 10 December 2018 / Accepted: 13 December 2018 / Published: 15 December 2018
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Abstract
Recently, high-resolution patterned metal oxide semiconductors (MOS) have gained considerable attention for enhanced gas sensing performance due to their polycrystalline nature, ultrasmall grain size (~5 nm), patternable properties, and high surface-to-volume ratio. Herein, we significantly enhanced the sensing performance of that patterned MOS [...] Read more.
Recently, high-resolution patterned metal oxide semiconductors (MOS) have gained considerable attention for enhanced gas sensing performance due to their polycrystalline nature, ultrasmall grain size (~5 nm), patternable properties, and high surface-to-volume ratio. Herein, we significantly enhanced the sensing performance of that patterned MOS by galvanic replacement, which allows for selective functionalization on ultrathin Cu2O nanopatterns. Based on the reduction potential energy difference between the base channel material (Cu2O) and the decorated metal ion (Pt2+), Pt could be selectively and precisely decorated onto the desired area of the Cu2O nanochannel array. Overall, the Pt-decorated Cu2O exhibited 11-fold higher NO2 (100 ppm) sensing sensitivity as compared to the non-decorated sensing channel, the while the channel device with excessive Pt doping showed complete loss of sensing properties. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Guiding Ketogenic Diet with Breath Acetone Sensors
Sensors 2018, 18(11), 3655; https://doi.org/10.3390/s18113655
Received: 8 October 2018 / Revised: 22 October 2018 / Accepted: 22 October 2018 / Published: 28 October 2018
Cited by 2 | PDF Full-text (1659 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ketogenic diet (KD; high fat, low carb) is a standard treatment for obesity, neurological diseases (e.g., refractory epilepsy) and a promising method for athletes to improve their endurance performance. Therein, the level of ketosis must be regulated tightly to ensure an effective therapy. [...] Read more.
Ketogenic diet (KD; high fat, low carb) is a standard treatment for obesity, neurological diseases (e.g., refractory epilepsy) and a promising method for athletes to improve their endurance performance. Therein, the level of ketosis must be regulated tightly to ensure an effective therapy. Here, we introduce a compact and inexpensive breath sensor to monitor ketosis online and non-invasively. The sensor consists of Si-doped WO3 nanoparticles that detect breath acetone selectively with non-linear response characteristics in the relevant range of 1 to 66 ppm, as identified by mass spectrometry. When tested on eleven subjects (five women and six men) undergoing a 36-h KD based on the Johns Hopkins protocol, this sensor clearly recognizes the onset and progression of ketosis. This is in good agreement to capillary blood β-hydroxybutyrate (BOHB) measurements. Despite similar dieting conditions, strong inter-subject differences in ketosis dynamics were observed and correctly identified by the sensor. These even included breath acetone patterns that could be linked to low tolerance to that diet. As a result, this portable breath sensor represents an easily applicable and reliable technology to monitor KD, possibly during medical treatment of epilepsy and weight loss. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Characteristics and Temperature Compensation of Non-Dispersive Infrared (NDIR) Alcohol Gas Sensors According to Incident Light Intensity
Sensors 2018, 18(9), 2911; https://doi.org/10.3390/s18092911
Received: 3 August 2018 / Revised: 24 August 2018 / Accepted: 29 August 2018 / Published: 1 September 2018
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Abstract
This paper discusses the output characteristics of the sensor response of infrared ethanol gas detectors based on incident radiation intensity. Sensors placed at each focal point of two elliptical waveguides were fabricated to yield two module combinations and to verify the output characteristics. [...] Read more.
This paper discusses the output characteristics of the sensor response of infrared ethanol gas detectors based on incident radiation intensity. Sensors placed at each focal point of two elliptical waveguides were fabricated to yield two module combinations and to verify the output characteristics. A thin Parylene-C film was deposited onto the reflector surfaces of one module. The thermal properties were compared between the sensor (2.0 Ø) and sensor with a hollow disk (1.6 Ø), the disk being mounted at the end of one detector. The fabricated sensor modules were placed inside a gas chamber. The temperature was increased from 253 K to 333 K, over the concentration range from 0 to 500 ppm. As the temperature increases by 10 K, the output of sensor (2.0 Ø) without and with Parylene-C coating typically increased by 70 mV and 52 mV, respectively. However, the sensor output with the hollow disk showed an average decrement of 0.8 mV/50 ppm and 1 mV/50 ppm for module without and with Parylene-C deposition, respectively. For concentrations higher than 50 ppm, the estimation error was around ±5%. Further, the sensitivity to temperature variation and the absorbance of infrared (IR) reflection was found higher for Parylene-C coated module. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Research on a Fast-Response Thermal Conductivity Sensor Based on Carbon Nanotube Modification
Sensors 2018, 18(7), 2191; https://doi.org/10.3390/s18072191
Received: 17 April 2018 / Revised: 28 June 2018 / Accepted: 4 July 2018 / Published: 7 July 2018
Cited by 1 | PDF Full-text (4135 KB) | HTML Full-text | XML Full-text
Abstract
Aiming at solving the slow-response problem of traditional bead-type thermal conductivity gas sensors, a fast-response thermal conductivity gas sensor can be made by using multiwalled carbon nanotubes (MWNTs), combined with the technology of carrier modification, to modify the performance of the sensor carrier. [...] Read more.
Aiming at solving the slow-response problem of traditional bead-type thermal conductivity gas sensors, a fast-response thermal conductivity gas sensor can be made by using multiwalled carbon nanotubes (MWNTs), combined with the technology of carrier modification, to modify the performance of the sensor carrier. The carrier material, granular nanoscale γ-Al2O3/ZrO2, was synthesized by chemical precipitation, and its particle size was found to be 50–70 nm through SEM. After the carrier material was wet-incorporated into carbon nanotubes, the composite carrier γ-Al2O3/ZrO2/MWNTs was obtained. The results show that the designed thermal conductivity sensor has a fast response to methane gas, with a 90% response time of 7 s and a recovery time of 16 s. There is a good linear relationship between the sensor output and CH4 gas concentration, with an average sensitivity of 1.15 mV/1% CH4. Thus, the response speed of a thermal conductivity sensor can be enhanced by doping carbon nanotubes into γ-Al2O3/ZrO2. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle High-Performance Limiting Current Oxygen Sensor Comprised of Highly Active La0.75Sr0.25Cr0.5Mn0.5O3 Electrode
Sensors 2018, 18(7), 2155; https://doi.org/10.3390/s18072155
Received: 7 June 2018 / Revised: 30 June 2018 / Accepted: 2 July 2018 / Published: 4 July 2018
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Abstract
Zirconia-based limiting current oxygen sensor gains considerable attention, due to its high-performance in improving the combustion efficiency of fossil fuels and reducing the emission of exhaust gases. Nevertheless, the Pt electrode is frequently used in the oxygen sensor, therefore, it restrains the broader [...] Read more.
Zirconia-based limiting current oxygen sensor gains considerable attention, due to its high-performance in improving the combustion efficiency of fossil fuels and reducing the emission of exhaust gases. Nevertheless, the Pt electrode is frequently used in the oxygen sensor, therefore, it restrains the broader application due to the high cost. Quite recently, La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) has been reported to be highly active to catalyze oxygen reduction. Herein, with the intention of replacing the frequently used Pt, we studied the practicability of adapting the LSCM to zirconia-based limiting current oxygen sensor. Through comparing the electrocatalytic activity of LSCM and Pt, it is confirmed that LSCM gave analogous oxygen reactivity with that of the Pt. Then, limiting the current oxygen sensors comprised of LSCM or Pt are fabricated and their sensing behavior to oxygen in the range of 2–25% is evaluated. Conclusively, quick response/recovery rate (within 7s), linear relationship, and high selectivity (against 5% CO2 and H2O) in sensing oxygen are observed for the sensors, regardless of the sensing materials (LSCM or Pt) that are used in the sensor. Particularly, identical sensing characteristics are observed for the sensors consisting of LSCM or Pt, indicating the practicability of replacing the Pt electrode by adapting the LSCM electrode to future zirconia-based oxygen sensors. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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Open AccessArticle Enhanced Hydrogen Detection Based on Mg-Doped InN Epilayer
Sensors 2018, 18(7), 2065; https://doi.org/10.3390/s18072065
Received: 18 May 2018 / Revised: 27 June 2018 / Accepted: 27 June 2018 / Published: 28 June 2018
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Abstract
It is a fact that surface electron accumulation layer with sheet electron density in the magnitude of ~1013 cm−2 on InN, either as-grown or Mg-doped, makes InN an excellent candidate for sensing application. In this paper, the response of hydrogen sensors [...] Read more.
It is a fact that surface electron accumulation layer with sheet electron density in the magnitude of ~1013 cm−2 on InN, either as-grown or Mg-doped, makes InN an excellent candidate for sensing application. In this paper, the response of hydrogen sensors based on Mg-doped InN films (InN:Mg) grown by molecular beam epitaxy has been investigated. The sensor exhibits a resistance variation ratio of 16.8% with response/recovery times of less than 2 min under exposure to 2000 ppm H2/air at 125 °C, which is 60% higher in the magnitude of response than the one based on the as-grown InN film. Hall-effect measurement shows that the InN:Mg with suitable Mg doping level exhibits larger sheet resistance, which accords with buried p-type conduction in the InN bulk. This work shows the advantage of InN:Mg and signifies its potential for sensing application. Full article
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
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