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Application of Thin Film Materials in Sensors

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

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 11652

Special Issue Editor

Christopher Ingold Laboratories, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
Interests: gas sensors; environmental monitoring; photocatalysis; nanomaterials; thin films; atomic layer deposition

Special Issue Information

Dear Colleagues,

Whilst a thin film has no formal definition, it is commonly taken to mean a material, either additive or intrinsic, that has a thickness ranging from atomic layers (subnanometer) to several microns. The use of ‘bottom-up’ fabrication techniques that include both chemical methods—such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) —and physical methods—such as physical vapor deposition (PVD), sputtering, and molecular beam epitaxy—have allowed exploration of a wide range of materials and device architectures over the last two decades. These methods can also be used to make thin film devices efficiently and reproducibly at relatively low cost, meaning material advances arising from use of these techniques have significant potential for commercial impact.

Thin films are, in general, more sensitive to local changes than equivalent materials with larger dimensions, and they can also be more robust/flexible, hence providing important enhancements in functional performance. Thin film sensor devices where the sensor element is achieved using a thin film have many potential advantages over conventional sensors, which typically include smaller form factor and/or lower power consumption whilst at least maintaining—although in many cases exceeding—performance over conventional/thick film devices. To highlight the important advancements being made in sensor function and performance by use of thin film technologies, MDPI Sensors will be publishing a Special Issue on “Application of Thin Film Materials in Sensors”. We are seeking contributions in this area, where the use of a thin film is integral to the device function, with envisaged sensing areas including (but not limited to) gas detection (including humidity), strain, heat flux, and corrosion.

Prof. Dr. Chris Blackman
Guest Editor

Manuscript Submission Information

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Published Papers (4 papers)

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Research

15 pages, 4535 KiB  
Article
Development and Characterization of Integrated Nano-Sensors for Organic Residues and pH Field Detection
by Itamar Chajanovsky, Sarah Cohen, Giorgi Shtenberg and Ran Yosef Suckeveriene
Sensors 2021, 21(17), 5842; https://doi.org/10.3390/s21175842 - 30 Aug 2021
Cited by 3 | Viewed by 1934
Abstract
Meeting global water quality standards is a real challenge to ensure that food crops and livestock are fit for consumption, as well as for human health in general. A major hurdle affecting the detection of pollutants in water reservoirs is the lapse of [...] Read more.
Meeting global water quality standards is a real challenge to ensure that food crops and livestock are fit for consumption, as well as for human health in general. A major hurdle affecting the detection of pollutants in water reservoirs is the lapse of time between the sampling moment and the availability of the laboratory-based results. Here, we report the preparation, characterization, and performance assessment of an innovative sensor for the rapid detection of organic residue levels and pH in water samples. The sensor is based on carbonaceous nanomaterials (CNMs) coated with an intrinsically conductive polymer, polyaniline (PANI). Inverse emulsion polymerizations of aniline in the presence of carbon nanotubes (CNTs) or graphene were prepared and confirmed by thermogravimetric analysis and high-resolution scanning electron microscopy. Aminophenol and phenol were used as proxies for organic residue detection. The PANI/CNM nanocomposites were used to fabricate thin-film sensors. Of all the CNMs, the smallest limit of detection (LOD) was achieved for multi-walled CNT (MWCNT) with a LOD of 9.6 ppb for aminophenol and a very high linearity of 0.997, with an average sensitivity of 2.3 kΩ/pH at an acid pH. This high sensor performance can be attributed to the high homogeneity of the PANI coating on the MWCNT surface. Full article
(This article belongs to the Special Issue Application of Thin Film Materials in Sensors)
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12 pages, 5511 KiB  
Communication
Ratiometric Sensor Based on PtOEP-C6/Poly (St-TFEMA) Film for Automatic Dissolved Oxygen Content Detection
by Honglin Zhang and Zhiguo Zhang
Sensors 2020, 20(21), 6175; https://doi.org/10.3390/s20216175 - 29 Oct 2020
Cited by 10 | Viewed by 2586
Abstract
A ratiometric oxygen sensor based on a platinum octaethylporphyrin (PtOEP)–coumarin 6 (C6)/poly (styrene-trifluoroethyl methacrylate) (poly (St-TFEMA)) film was developed for automatic dissolved oxygen (DO) detection. The oxygen-sensing film according to the dynamic quenching mechanism was prepared by embedding platinum octaethylporphyrin (PtOEP) and coumarin [...] Read more.
A ratiometric oxygen sensor based on a platinum octaethylporphyrin (PtOEP)–coumarin 6 (C6)/poly (styrene-trifluoroethyl methacrylate) (poly (St-TFEMA)) film was developed for automatic dissolved oxygen (DO) detection. The oxygen-sensing film according to the dynamic quenching mechanism was prepared by embedding platinum octaethylporphyrin (PtOEP) and coumarin 6 (C6) in poly (styrene-trifluoroethyl methacrylate) (poly (St-TFEMA)). The optical parameter (OP) was defined as the ratio of the oxygen-insensitive fluorescence from C6 to the oxygen-sensitive phosphorescence from PtOEP. A calibration equation expressing the correlation between the OP values and DO content described by a linear function was obtained. A program based on the Labview software was developed for monitoring the real-time DO content automatically. The influence of the excitation intensity and fluctuation on the OP values and the direct luminescence signal (integration areas) was compared, verifying the strong anti-interference ability of the sensor. The detection limit of the sensor was determined to be 0.10 (1) mg/L. The switching response time and recovery time of the sensor were 0.4 and 1.3 s, respectively. Finally, the oxygen sensor was applied to the investigation of the kinetic process of the DO content variation, which revealed an exponential relationship with time. Full article
(This article belongs to the Special Issue Application of Thin Film Materials in Sensors)
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14 pages, 4913 KiB  
Article
New Insights towards High-Temperature Ethanol-Sensing Mechanism of ZnO-Based Chemiresistors
by Lesia Piliai, David Tomeček, Martin Hruška, Ivan Khalakhan, Jaroslava Nováková, Přemysl Fitl, Roman Yatskiv, Jan Grym, Mykhailo Vorokhta, Iva Matolínová and Martin Vrňata
Sensors 2020, 20(19), 5602; https://doi.org/10.3390/s20195602 - 30 Sep 2020
Cited by 12 | Viewed by 2638
Abstract
In this work, we investigate ethanol (EtOH)-sensing mechanisms of a ZnO nanorod (NRs)-based chemiresistor using a near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). First, the ZnO NRs-based sensor was constructed, showing good performance on interaction with 100 ppm of EtOH in the ambient air at [...] Read more.
In this work, we investigate ethanol (EtOH)-sensing mechanisms of a ZnO nanorod (NRs)-based chemiresistor using a near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). First, the ZnO NRs-based sensor was constructed, showing good performance on interaction with 100 ppm of EtOH in the ambient air at 327 °C. Then, the same ZnO NRs film was investigated by NAP-XPS in the presence of 1 mbar oxygen, simulating the ambient air atmosphere and O2/EtOH mixture at the same temperature. The partial pressure of EtOH was 0.1 mbar, which corresponded to the partial pressure of 100 ppm of analytes in the ambient air. To better understand the EtOH-sensing mechanism, the NAP-XPS spectra were also studied on exposure to O2/EtOH/H2O and O2/MeCHO (MeCHO = acetaldehyde) mixtures. Our results revealed that the reaction of EtOH with chemisorbed oxygen on the surface of ZnO NRs follows the acetaldehyde pathway. It was also demonstrated that, during the sensing process, the surface becomes contaminated by different products of MeCHO decomposition, which decreases dc-sensor performance. However, the ac performance does not seem to be affected by this phenomenon. Full article
(This article belongs to the Special Issue Application of Thin Film Materials in Sensors)
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18 pages, 6356 KiB  
Article
Influence of Mg Doping Levels on the Sensing Properties of SnO2 Films
by Bouteina Bendahmane, Milena Tomić, Nour El Houda Touidjen, Isabel Gràcia, Stella Vallejos and Farida Mansour
Sensors 2020, 20(7), 2158; https://doi.org/10.3390/s20072158 - 10 Apr 2020
Cited by 8 | Viewed by 3533
Abstract
This work presents the effect of magnesium (Mg) doping on the sensing properties of tin dioxide (SnO2) thin films. Mg-doped SnO2 films were prepared via a spray pyrolysis method using three doping concentrations (0.8 at.%, 1.2 at.%, and 1.6 at.%) [...] Read more.
This work presents the effect of magnesium (Mg) doping on the sensing properties of tin dioxide (SnO2) thin films. Mg-doped SnO2 films were prepared via a spray pyrolysis method using three doping concentrations (0.8 at.%, 1.2 at.%, and 1.6 at.%) and the sensing responses were obtained at a comparatively low operating temperature (160 °C) compared to other gas sensitive materials in the literature. The morphological, structural and chemical composition analysis of the doped films show local lattice disorders and a proportional decrease in the average crystallite size as the Mg-doping level increases. These results also indicate an excess of Mg (in the samples prepared with 1.6 at.% of magnesium) which causes the formation of a secondary magnesium oxide phase. The films are tested towards three volatile organic compounds (VOCs), including ethanol, acetone, and toluene. The gas sensing tests show an enhancement of the sensing properties to these vapors as the Mg-doping level rises. This improvement is particularly observed for ethanol and, thus, the gas sensing analysis is focused on this analyte. Results to 80 ppm of ethanol, for instance, show that the response of the 1.6 at.% Mg-doped SnO2 film is four times higher and 90 s faster than that of the 0.8 at.% Mg-doped SnO2 film. This enhancement is attributed to the Mg-incorporation into the SnO2 cell and to the formation of MgO within the film. These two factors maximize the electrical resistance change in the gas adsorption stage, and thus, raise ethanol sensitivity. Full article
(This article belongs to the Special Issue Application of Thin Film Materials in Sensors)
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