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Special Issue "Gas Nanosensors"

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

Deadline for manuscript submissions: closed (30 November 2016).

Special Issue Editors

Prof. Dr. Eduard Llobet
E-Mail Website
Guest Editor
MINOS-EMaS, Universitat Rovira i Virgili, 43007 Tarragona, Spain
Tel. +34 977 558 502; Fax: +34 977 559 605
Interests: Gas sensors employing nanosized metal oxides and carbon nanomaterials integrated in ceramics, MEMS or flexible polymeric transducers. Nanomaterial synthesis using CVD or VPT and surface functionalization via grafting of functional groups or molecules or substitutional doping. Development of gas sensing applications in environment, security.
Special Issues and Collections in MDPI journals
Dr. Stella Vallejos
E-Mail Website
Guest Editor
SIX Research Centre, Brno University of Technology, Brno, Czech Republic
Interests: gas sensing technologies; chemosensors; synthesis of functional nanostructured materials; chemical vapor deposition

Special Issue Information

Dear Colleagues,

In the last few years, intensive research has been carried out in the synthesis of functional nanomaterials with superior gas sensing performance (i.e., sensitivity, selectivity and stability). Dots, nanowires, nanoribbons, nanotubes, nanorods, monolayers, and hierarchical nanomaterials, have been synthesized via a wide spectrum of techniques, including solution synthesis, smart anodization, spray pyrolysis, or chemical vapor deposition, to cite a few. The integration of these nanomaterials onto different transducer platforms, in particular MEMS (Micro-Electro-Mechanical Systems) or polymeric, in view of obtaining functional nanosensors has been the subject of many studies, in which yield, reproducibility, reliability, and long-term stability have been addressed. These results are widening the potential use of gas nanosensors in different fields and applications, such as RFID (Radio-frequency identification) systems with gas sensing capabilities, wearables or smartphones for environmental monitoring, safety at the workplace, or breath analysis. This Special Issue of Sensors will be dedicated to highlight the emerging technologies of gas nanosensors and their applications, and aims at presenting the latest technologies and methodologies developed in this interdisciplinary field of science. Full papers, communications and reviews are welcome. Topics include, but are not limited to, the following:

  • Synthesis, functionalization and gas sensing properties of metal oxide nanomaterials (including single-crystalline, polycrystalline, nanostructured metal oxides).
  • Synthesis, functionalization and gas sensing properties of carbon nanomaterials (including carbon nanofibers, carbon nanotubes and graphene or graphene-like nanomaterials.
  • Synthesis and gas sensing properties of hierarchical nanomaterials.
  • Gas sensing devices employing bare or functionalized silicon nanowires.
  • Gas sensing devices employing organic nanomaterials
  • Integration of gas sensitive nanomaterials onto transducers platforms (MEMS, ceramic, polymeric, etc.) for resistive, gravimetric, gas sensing.
  • New applications of gas nanosensors (RFID, wearable, integration in smartphones, etc.)

Prof. Dr. Eduard Llobet
Dr. Stella Vallejos
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 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

  • inorganic gas sensitive nanomaterials
  • organic gas sensitive nanomaterials
  • nanomaterial synthesis
  • integration in transducer platforms
  • applications

Published Papers (18 papers)

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Research

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Open AccessArticle
Investigation of Pristine Graphite Oxide as Room-Temperature Chemiresistive Ammonia Gas Sensing Material
Sensors 2017, 17(2), 320; https://doi.org/10.3390/s17020320 - 09 Feb 2017
Cited by 17
Abstract
Graphite oxide has been investigated as a possible room-temperature chemiresistive sensor of ammonia in a gas phase. Graphite oxide was synthesized from high purity graphite using the modified Hummers method. The graphite oxide sample was investigated using scanning electron microscopy, energy dispersive X-ray [...] Read more.
Graphite oxide has been investigated as a possible room-temperature chemiresistive sensor of ammonia in a gas phase. Graphite oxide was synthesized from high purity graphite using the modified Hummers method. The graphite oxide sample was investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetry and differential scanning calorimetry. Sensing properties were tested in a wide range of ammonia concentrations in air (10–1000 ppm) and under different relative humidity levels (3%–65%). It was concluded that the graphite oxide–based sensor possessed a good response to NH3 in dry synthetic air (ΔR/R0 ranged from 2.5% to 7.4% for concentrations of 100–500 ppm and 3% relative humidity) with negligible cross-sensitivity towards H2 and CH4. It was determined that the sensor recovery rate was improved with ammonia concentration growth. Increasing the ambient relative humidity led to an increase of the sensor response. The highest response of 22.2% for 100 ppm of ammonia was achieved at a 65% relative humidity level. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Volatile Organic Compounds Sensing Using Optical Fibre Long Period Grating with Mesoporous Nano-Scale Coating
Sensors 2017, 17(2), 205; https://doi.org/10.3390/s17020205 - 08 Feb 2017
Cited by 11
Abstract
A long period grating (LPG) modified with a mesoporous film infused with a calixarene as a functional compound was employed for the detection of individual volatile organic compounds (VOCs) and their mixtures. The mesoporous film consisted of an inorganic part, SiO2 nanoparticles [...] Read more.
A long period grating (LPG) modified with a mesoporous film infused with a calixarene as a functional compound was employed for the detection of individual volatile organic compounds (VOCs) and their mixtures. The mesoporous film consisted of an inorganic part, SiO2 nanoparticles (NPs), along with an organic moiety of poly(allylamine hydrochloride) polycation PAH, which was finally infused with the functional compound, p-sulphanato calix[4]arene (CA[4]) or p-sulphanato calix[8]arene (CA[8]). The LPG sensor was designed to operate at the phase matching turning point to provide the highest sensitivity. The sensing mechanism is based on the measurement of the refractive index (RI) change induced by a complex of the VOCs with calixarene. The LPG, modified with a coating of 5 cycles of (SiO2 NPs/PAH) and infused with CA[4] or CA[8], was exposed to chloroform, benzene, toluene and acetone vapours. The British Standards test of the VOCs emissions from material (BS EN ISO 16000-9:2006) was used to test the LPG sensor performance. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Effects of Operating Temperature on Droplet Casting of Flexible Polymer/Multi-Walled Carbon Nanotube Composite Gas Sensors
Sensors 2017, 17(1), 4; https://doi.org/10.3390/s17010004 - 22 Dec 2016
Cited by 6
Abstract
This study examined the performance of a flexible polymer/multi-walled carbon nanotube (MWCNT) composite sensor array as a function of operating temperature. The response magnitudes of a cost-effective flexible gas sensor array equipped with a heater were measured with respect to five different operating [...] Read more.
This study examined the performance of a flexible polymer/multi-walled carbon nanotube (MWCNT) composite sensor array as a function of operating temperature. The response magnitudes of a cost-effective flexible gas sensor array equipped with a heater were measured with respect to five different operating temperatures (room temperature, 40 °C, 50 °C, 60 °C, and 70 °C) via impedance spectrum measurement and sensing response experiments. The selected polymers that were droplet cast to coat a MWCNT conductive layer to form two-layer polymer/MWCNT composite sensing films included ethyl cellulose (EC), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Electrical characterization of impedance, sensing response magnitude, and scanning electron microscope (SEM) morphology of each type of polymer/MWCNT composite film was performed at different operating temperatures. With respect to ethanol, the response magnitude of the sensor decreased with increasing operating temperatures. The results indicated that the higher operating temperature could reduce the response and influence the sensitivity of the polymer/MWCNT gas sensor array. The morphology of polymer/MWCNT composite films revealed that there were changes in the porous film after volatile organic compound (VOC) testing. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Synthesis, Characterization, and Sensor Applications of Spinel ZnCo2O4 Nanoparticles
Sensors 2016, 16(12), 2162; https://doi.org/10.3390/s16122162 - 17 Dec 2016
Cited by 12
Abstract
Spinel ZnCo2O4 nanoparticles were synthesized by means of the microwave-assisted colloidal method. A solution containing ethanol, Co-nitrate, Zn-nitrate, and dodecylamine was stirred for 24 h and evaporated by a microwave oven. The resulting solid material was dried at 200 °C [...] Read more.
Spinel ZnCo2O4 nanoparticles were synthesized by means of the microwave-assisted colloidal method. A solution containing ethanol, Co-nitrate, Zn-nitrate, and dodecylamine was stirred for 24 h and evaporated by a microwave oven. The resulting solid material was dried at 200 °C and subsequently calcined at 500 °C for 5 h. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, confirming the formation of spinel ZnCo2O4 nanoparticles with average sizes between 49 and 75 nm. It was found that the average particle size decreased when the dodecylamine concentration increased. Pellets containing ZnCo2O4 nanoparticles were fabricated and tested as sensors in carbon monoxide (CO) and propane (C3H8) gases at different concentrations and temperatures. Sensor performance tests revealed an extremely high response to 300 ppm of CO at an operating temperature of 200 °C. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Disposable, Paper-Based, Inkjet-Printed Humidity and H2S Gas Sensor for Passive Sensing Applications
Sensors 2016, 16(12), 2073; https://doi.org/10.3390/s16122073 - 06 Dec 2016
Cited by 18
Abstract
An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a [...] Read more.
An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a paper substrate provides the base conductivity that varies during the sensing process. Aided by the porous nature of the substrate, a change in relative humidity from 18% to 88% decreases the electrode resistance from a few Mega-ohms to the kilo-ohm range. For gas sensing, an additional copper acetate-based customized ink is printed on top of the electrode, which, upon reaction with hydrogen sulphide gas (H2S) changes, both the optical and the electrical properties of the electrode. A fast response time of 3 min is achieved at room temperature for a H2S concentration of 10 ppm at a relative humidity (RH) of 45%. The passive wireless sensing is enabled through an antenna in which the inner loop takes care of conductivity changes in the 4–5 GHz band, whereas the outer-dipole arm is used for chipless identification in the 2–3 GHz band. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
SAW Humidity Sensor Sensitivity Enhancement via Electrospraying of Silver Nanowires
Sensors 2016, 16(12), 2024; https://doi.org/10.3390/s16122024 - 30 Nov 2016
Cited by 9
Abstract
In this research, we investigated the influence of the surface coatings of silver nanowires on the sensitivity of surface acoustic wave (SAW) humidity sensors. Silver nanowires, with poly(vinylpyrrolidone) (PVP), which is a hydrophilic capping agent, were chemically synthesized, with an average length of [...] Read more.
In this research, we investigated the influence of the surface coatings of silver nanowires on the sensitivity of surface acoustic wave (SAW) humidity sensors. Silver nanowires, with poly(vinylpyrrolidone) (PVP), which is a hydrophilic capping agent, were chemically synthesized, with an average length of 15 µm and an average diameter of 60 nm. Humidity sensors, with 433 MHz frequency dual-port resonator Rayleigh-SAW devices, were coated by silver nanowires (AgNWs) using the electrospray coating method. It was demonstrated that increasing thickness of coated AgNW on the surfaces of SAW devices results in increased sensitivity. The highest frequency shift (262 kHz) in these SAW devices was obtained with an injection of 0.5 mL of the AgNW solution with a concentration of 0.5 mg/mL at an injection rate of 1 mL/h. It also showed the highest humidity sensitivity among the other prepared SAW devices. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
The Impact of Sepiolite on Sensor Parameters during the Detection of Low Concentrations of Alcohols
Sensors 2016, 16(11), 1881; https://doi.org/10.3390/s16111881 - 09 Nov 2016
Abstract
The article presents the results of the detection of low-concentration C1–C4 alcohols using a planar sensor, in which a sepiolite filter was applied next to the gas-sensitive layer based on tin dioxide. The sepiolite layer is composed of tubes that have a length [...] Read more.
The article presents the results of the detection of low-concentration C1–C4 alcohols using a planar sensor, in which a sepiolite filter was applied next to the gas-sensitive layer based on tin dioxide. The sepiolite layer is composed of tubes that have a length of several microns, and the diameter of the single tube ranges from several to tens of nanometers. The sepiolite layer itself demonstrated no chemical activity in the presence of volatile organic compounds (VOC), and the passive filter made of this material did not modify the chemical composition of the gaseous atmosphere diffusing to the gas-sensitive layer. The test results revealed that the structural remodelling of the sepiolite that occurs under the influence of temperature, as well as the effect of the filter (a compound with ionic bonds) with molecules of water, has a significant impact on the improvement of the sensitivity of the sensor in relation to volatile organic compounds when compared to the sensor without a filter. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Enhanced Acetone Sensing Characteristics of ZnO/Graphene Composites
Sensors 2016, 16(11), 1876; https://doi.org/10.3390/s16111876 - 09 Nov 2016
Cited by 14
Abstract
ZnO/graphene (ZnO-G) hybrid composites are prepared via hydrothermal synthesis with graphite, N-methyl-pyrrolidone (NMP), and Zn(NO3)2·6H2O as the precursors. The characterizations, including X-ray diffraction (XRD), thermogravimetric analyses (TGA), Raman spectroscopy, and transmission electron microscopy (TEM) indicate the formation [...] Read more.
ZnO/graphene (ZnO-G) hybrid composites are prepared via hydrothermal synthesis with graphite, N-methyl-pyrrolidone (NMP), and Zn(NO3)2·6H2O as the precursors. The characterizations, including X-ray diffraction (XRD), thermogravimetric analyses (TGA), Raman spectroscopy, and transmission electron microscopy (TEM) indicate the formation of ZnO-G. Gas sensors were fabricated with ZnO-G composites and ZnO as sensing material, indicating that the response of the ZnO towards acetone was significantly enhanced by graphene doping. It was found that the ZnO-G sensor exhibits remarkably enhanced response of 13.3 at the optimal operating temperature of 280 °C to 100 ppm acetone, an improvement from 7.7 with pure ZnO. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Achievement of High-Response Organic Field-Effect Transistor NO2 Sensor by Using the Synergistic Effect of ZnO/PMMA Hybrid Dielectric and CuPc/Pentacene Heterojunction
Sensors 2016, 16(10), 1763; https://doi.org/10.3390/s16101763 - 21 Oct 2016
Cited by 4
Abstract
High-response organic field-effect transistor (OFET)-based NO2 sensors were fabricated using the synergistic effect the synergistic effect of zinc oxide/poly(methyl methacrylate) (ZnO/PMMA) hybrid dielectric and CuPc/Pentacene heterojunction. Compared with the OFET sensors without synergistic effect, the fabricated OFET sensors showed a remarkable shift [...] Read more.
High-response organic field-effect transistor (OFET)-based NO2 sensors were fabricated using the synergistic effect the synergistic effect of zinc oxide/poly(methyl methacrylate) (ZnO/PMMA) hybrid dielectric and CuPc/Pentacene heterojunction. Compared with the OFET sensors without synergistic effect, the fabricated OFET sensors showed a remarkable shift of saturation current, field-effect mobility and threshold voltage when exposed to various concentrations of NO2 analyte. Moreover, after being stored in atmosphere for 30 days, the variation of saturation current increased more than 10 folds at 0.5 ppm NO2. By analyzing the electrical characteristics, and the morphologies of organic semiconductor films of the OFET-based sensors, the performance enhancement was ascribed to the synergistic effect of the dielectric and organic semiconductor. The ZnO nanoparticles on PMMA dielectric surface decreased the grain size of pentacene formed on hybrid dielectric, facilitating the diffusion of CuPc molecules into the grain boundary of pentacene and the approach towards the conducting channel of OFET. Hence, NO2 molecules could interact with CuPc and ZnO nanoparticles at the interface of dielectric and organic semiconductor. Our results provided a promising strategy for the design of high performance OFET-based NO2 sensors in future electronic nose and environment monitoring. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Towards Enhanced Gas Sensor Performance with Fluoropolymer Membranes
Sensors 2016, 16(10), 1605; https://doi.org/10.3390/s16101605 - 28 Sep 2016
Cited by 6
Abstract
In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination, [...] Read more.
In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination, as well as polymers whose monomers have ether groups (-O-) in addition to fluorine groups (-F). For the study, a set of application-relevant gases including H2, CO, CO2, NO2, methane, ethanol, acetone, and acetaldehyde as well as various concentrations of relative humidity were used. These gases have different functional groups and polarities, yet have a similar kinetic diameter and are therefore typically difficult to separate. The concentrations of the gases were chosen according to international indicative limit values (TWA, STEL). To measure the concentration in the feed and permeate, we used tin-dioxide-based metal oxide gas sensors with palladium catalyst (SnO2:Pd), catalytic sensors (also SnO2:Pd-based) and thermal conductivity sensors. This allows a close examination of the interdependence of diffusion and physicochemical operating principle of the sensor. Our goal is to increase the selectivity of gas sensors by using inexpensive fluoropolymer membranes. The measurements showed that through membranes with low polarity, preferably non-polar gases are transported. Furthermore, the degree of crystallization influences the permeability and selectivity of a polymer membrane. Basically the polar polymers showed a higher permeability to water vapor and polar substances than non-polar polymer membranes. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessCommunication
Selectivity Enhancement by Using Double-Layer MOX-Based Gas Sensors Prepared by Flame Spray Pyrolysis (FSP)
Sensors 2016, 16(9), 1437; https://doi.org/10.3390/s16091437 - 06 Sep 2016
Cited by 5
Abstract
Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of [...] Read more.
Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of highly porous metal oxide double- and single-layer sensors obtained by flame spray pyrolysis. The results show that the calculated resistance ratios of the single- and double-layer sensors are a good indicator for the presence of specific gases in the atmosphere, and can constitute some building blocks for the development of chemical logic devices. Due to the inherent lack of selectivity of SMOX-based gas sensors, such devices could be especially relevant for domestic applications. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
A Sensor Array for the Detection and Discrimination of Methane and Other Environmental Pollutant Gases
Sensors 2016, 16(8), 1163; https://doi.org/10.3390/s16081163 - 25 Jul 2016
Cited by 20
Abstract
We address the sensitive detection and discrimination of gases impacting the environment, such as CH4, NH3, SO2, and CO, using a sensor array and aided by principal component analysis (PCA). A 32-element chemiresistive sensor array consisting of [...] Read more.
We address the sensitive detection and discrimination of gases impacting the environment, such as CH4, NH3, SO2, and CO, using a sensor array and aided by principal component analysis (PCA). A 32-element chemiresistive sensor array consisting of nine different sensor materials including seven types of modified single-walled carbon nanotubes and two types of polymers has been constructed. PCA results demonstrate excellent discriminating ability of the chemiresistor sensor chip in the 1–30 ppm concentration range. The accuracy of the sensor was verified against data collected using cavity ring down spectroscopy. The sensor chip has also been integrated with a smartphone and has been shown to reproduce the sensing performance obtained with the laboratory measurement system. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
Reduced Graphene Oxide/Au Nanocomposite for NO2 Sensing at Low Operating Temperature
Sensors 2016, 16(7), 1152; https://doi.org/10.3390/s16071152 - 22 Jul 2016
Cited by 13
Abstract
A reduced grapheme oxide (rGO)/Au hybrid nanocomposite has been synthesized by hydrothermal treatment using graphite and HAuCl4 as the precursors. Characterization, including X-ray diffraction (XRD), Raman spectra, X-ray photoelecton spectroscopy (XPS) and transmission electron microscopy (TEM), indicates the formation of rGO/Au. A [...] Read more.
A reduced grapheme oxide (rGO)/Au hybrid nanocomposite has been synthesized by hydrothermal treatment using graphite and HAuCl4 as the precursors. Characterization, including X-ray diffraction (XRD), Raman spectra, X-ray photoelecton spectroscopy (XPS) and transmission electron microscopy (TEM), indicates the formation of rGO/Au. A gas sensor fabricated with rGO/Au nanocomposite was applied for NO2 detection at 50 °C. Compared with pure rGO, rGO/Au nanocomposite exhibits higher sensitivity, a more rapid response–recovery process and excellent reproducibility. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessArticle
A Single Nanobelt Transistor for Gas Identification: Using a Gas-Dielectric Strategy
Sensors 2016, 16(6), 917; https://doi.org/10.3390/s16060917 - 21 Jun 2016
Abstract
Despite tremendous potential and urgent demand in high-response low-cost gas identification, the development of gas identification based on a metal oxide semiconductor nanowire/nanobelt remains limited by fabrication complexity and redundant signals. Researchers have shown a multisensor-array strategy with “one key to one lock” [...] Read more.
Despite tremendous potential and urgent demand in high-response low-cost gas identification, the development of gas identification based on a metal oxide semiconductor nanowire/nanobelt remains limited by fabrication complexity and redundant signals. Researchers have shown a multisensor-array strategy with “one key to one lock” configuration. Here, we describe a new strategy to create high-response room-temperature gas identification by employing gas as dielectric. This enables gas discrimination down to the part per billion (ppb) level only based on one pristine single nanobelt transistor, with the excellent average Mahalanobis distance (MD) as high as 35 at the linear discriminant analysis (LDA) space. The single device realizes the selective recognition function of electronic nose. The effect of the gas dielectric on the response of the multiple field-effect parameters is discussed by the comparative investigation of gas and solid-dielectric devices and the studies on trap density changes in the conductive channel. The current work opens up exciting opportunities for room-temperature gas recognition based on the pristine single device. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Review

Jump to: Research

Open AccessReview
Nanostructured Polypyrrole-Based Ammonia and Volatile Organic Compound Sensors
Sensors 2017, 17(3), 562; https://doi.org/10.3390/s17030562 - 10 Mar 2017
Cited by 25
Abstract
The aim of this review is to summarize the recent progress in the fabrication of efficient nanostructured polymer-based sensors with special focus on polypyrrole. The correlation between physico-chemical parameters, mainly morphology of various polypyrrole nanostructures, and their sensitivity towards selected gas and volatile [...] Read more.
The aim of this review is to summarize the recent progress in the fabrication of efficient nanostructured polymer-based sensors with special focus on polypyrrole. The correlation between physico-chemical parameters, mainly morphology of various polypyrrole nanostructures, and their sensitivity towards selected gas and volatile organic compounds (VOC) is provided. The different approaches of polypyrrole modification with other functional materials are also discussed. With respect to possible sensors application in medicine, namely in the diagnosis of diseases via the detection of volatile biomarkers from human breath, the sensor interaction with humidity is described as well. The major attention is paid to analytes such as ammonia and various alcohols. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessFeature PaperReview
Nanomaterials for the Selective Detection of Hydrogen Sulfide in Air
Sensors 2017, 17(2), 391; https://doi.org/10.3390/s17020391 - 17 Feb 2017
Cited by 14
Abstract
This paper presents a focused review on the nanomaterials and associated transduction schemes that have been developed for the selective detection of hydrogen sulfide. It presents a quite comprehensive overview of the latest developments, briefly discusses the hydrogen sulfide detection mechanisms, identifying the [...] Read more.
This paper presents a focused review on the nanomaterials and associated transduction schemes that have been developed for the selective detection of hydrogen sulfide. It presents a quite comprehensive overview of the latest developments, briefly discusses the hydrogen sulfide detection mechanisms, identifying the reasons for the selectivity (or lack of) observed experimentally. It critically reviews performance, shortcomings, and identifies missing or overlooked important aspects. It identifies the most mature/promising materials and approaches for achieving inexpensive hydrogen sulfide sensors that could be employed in widespread, miniaturized, and inexpensive detectors and, suggests what research should be undertaken for ensuring that requirements are met. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessReview
Gas Sensors Based on Polymer Field-Effect Transistors
Sensors 2017, 17(1), 213; https://doi.org/10.3390/s17010213 - 22 Jan 2017
Cited by 28
Abstract
This review focuses on polymer field-effect transistor (PFET) based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (ΔISD). Dependent on the sensing layer which can be semiconducting [...] Read more.
This review focuses on polymer field-effect transistor (PFET) based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (ΔISD). Dependent on the sensing layer which can be semiconducting polymer, dielectric layer or conducting polymer gate, the PFET sensors can be subdivided into three types. For each type of sensor, we present the molecular structure of sensing polymer, the gas analyte and the sensing performance. Most importantly, we summarize various analyte–polymer interactions, which help to understand the sensing mechanism in the PFET sensors and can provide possible approaches for the sensor fabrication in the future. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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Open AccessReview
Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview
Sensors 2016, 16(9), 1531; https://doi.org/10.3390/s16091531 - 20 Sep 2016
Cited by 33
Abstract
Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and [...] Read more.
Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors. Full article
(This article belongs to the Special Issue Gas Nanosensors)
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