Topical Collection "Sustainable Metal Oxide Materials for Sensing Applications"

Editors

Dr. Ana Rovisco
E-Mail Website
Collection Editor
i3N/CENIMAT, Department of Materials Science, NOVA School of Science and Technology and CEMOP/UNINOVA, NOVA University Lisbon, Campus de Caparica, 2829-516 Caparica, Portugal
Interests: multicomponent oxides; nanostructures; nanofabrication; nano-lithography (EBL); nanodevices; flexible and transparent technology; oxide thin film transistors; energy harvesting; multifunctionali-ty; sustainability
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Elisabetta Comini
E-Mail Website
Collection Editor
Sensor Lab, Department of Information Engineering, University of Brescia and CNR INO, Via Valotti 9, 25133 Brescia, Italy
Interests: metal oxides; nanowires; chemical sensors; gas sensors; heterostructures; functional materials; material synthesis
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

In the last several decades, nanotechnology has advanced at an impressive rate, owing to a high level of development in both materials and processing routes. This impressive progress is contributing significantly to the growth of several areas, such as (opto)electronics, chemical sensors, medicine/biology, energy, and others.

Particularly, sensors are some of the key devices in smart surfaces and Internet of things (IoT) applications. To meet these concepts, sensing applications now require flexible, transparent, nanoscale devices and materials. In this context, metal oxides are particularly interesting due to their good optical and electrical properties and their capability for transparency, large area uniformity, and good mechanical flexibility. Concerning the environmental issues the world is facing, special attention should be given to materials and methods which are low-cost and sustainable, while still enabling high integration levels.

Thus, this Special Issue welcomes the submission of papers focused on the fabrication of sustainable metal oxide materials, in the form of thin films or nanostructures, and their application for sensors.

Dr. Ana Rovisco
Prof. Dr. Elisabetta Comini
Collection 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 submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection 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. Chemosensors is an international peer-reviewed open access monthly 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

  • metal oxides
  • thin films
  • nanomaterials
  • pH sensors
  • optical sensors
  • gas sensors
  • biosensors
  • sustainability

Published Papers (9 papers)

2022

Jump to: 2021

Article
An Electrochemical Sensor Based on Reduced Graphene Oxide and Copper Nanoparticles for Monitoring Estriol Levels in Water Samples after Bioremediation
Chemosensors 2022, 10(10), 395; https://doi.org/10.3390/chemosensors10100395 (registering DOI) - 28 Sep 2022
Abstract
Water contamination from endocrine disruptors has become a major problem for health issues. Estriol is a hormone often detected in several aquatic matrices, due to the inefficient removal of such compounds through conventional water treatment methods. Therefore, there is a continuous need to [...] Read more.
Water contamination from endocrine disruptors has become a major problem for health issues. Estriol is a hormone often detected in several aquatic matrices, due to the inefficient removal of such compounds through conventional water treatment methods. Therefore, there is a continuous need to develop new, efficient, and low-cost treatment methods for this hormone removal, as well as analytical devices able to detect estriol at low concentrations. In this present study, we report the use of the Eichhornia crassipes (water hyacinth) as a phytoremediation agent for estriol removal from aqueous matrices, in addition to a newly developed electrochemical sensor based on reduced graphene oxide and copper nanoparticles as a quantification and monitoring tool of the hormone. The developed sensor presented a linear detection region from 0.5 to 3.0 μmol L−1, with detection and quantification limits of 0.17 μmol L−1 and 0.56 μmol L−1, respectively. Phytoremediation experiments were conducted in 2 L beakers and the reducing levels of the hormone were studied. Water hyacinth was able to reduce contaminant levels by approximately 80.5% in 7 days and below detection limits in less than 9 days, which is a good alternative for water decontamination with this endocrine disruptor. Due to the hydrophobicity of estriol, the probable mechanism involved in the bioremediation process is rhizodegradation, and the decrease in pH in the beakers that contained the plants indicated a possible formation of biofilms on the roots. Full article
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2021

Jump to: 2022

Article
Controlled Growth of WO3 Pyramidal Thin Film via Hot-Filament Chemical Vapor Deposition: Electrochemical Detection of Ethylenediamine
Chemosensors 2021, 9(9), 257; https://doi.org/10.3390/chemosensors9090257 - 08 Sep 2021
Cited by 1 | Viewed by 730
Abstract
In this work, the structural, optical, morphological, and sensing features of tungsten oxide (WO3) thin film deposited on a silicon substrate via hot-filament chemical vapor deposition (HFCVD) are described. The experimental characterization tools, such as X-ray diffraction (XRD), field emission scanning [...] Read more.
In this work, the structural, optical, morphological, and sensing features of tungsten oxide (WO3) thin film deposited on a silicon substrate via hot-filament chemical vapor deposition (HFCVD) are described. The experimental characterization tools, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV-Vis), and Fourier transform infra-red (FTIR) spectroscopies, etc., were used to determine the properties of WO3 NPys thin films. The grown WO3 thin film illustrated closely packed porous pyramidal nanostructures (NPys) of improved grain size properties. The diffraction analysis revealed (100) and (200) of WO3 phases, suggesting the classic monoclinic crystal WO3 structure. HFCVD grown WO3 NPys thin film was employed as electro-active electrode for detecting ethylenediamine in 10 mL of 0.1 M phosphate buffer solution (PBS) by varying the ethylenediamine concentrations from 10 μM to 200 μM at room temperature. With a detection of limit (LOD) of ~9.56 μM, and a quick reaction time (10 s), the constructed chemical sensor achieved a high sensitivity of ~161.33 μA μM−1 cm−2. The durability test displayed an excellent stability of electrochemical sensor by maintaining over 90% sensitivity after 4 weeks of operation. This work provides a strategy for a facile preparation of WO3 NPys thin film electrode for sensor applications. Full article
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Article
Nickel-Oxide Based Thick-Film Gas Sensors for Volatile Organic Compound Detection
Chemosensors 2021, 9(9), 247; https://doi.org/10.3390/chemosensors9090247 - 03 Sep 2021
Cited by 6 | Viewed by 782
Abstract
In this paper, we report on the development of a highly sensitive and humidity-tolerant metal-oxide-based volatile organic compound (VOC) sensor, capable of rapidly detecting low concentrations of VOCs. For this, we successfully fabricated two different thicknesses of nickel oxide (NiO) sensors using a [...] Read more.
In this paper, we report on the development of a highly sensitive and humidity-tolerant metal-oxide-based volatile organic compound (VOC) sensor, capable of rapidly detecting low concentrations of VOCs. For this, we successfully fabricated two different thicknesses of nickel oxide (NiO) sensors using a spin-coating technique and tested them with seven different common VOCs at 40% r.h. The measured film thickness of the spin-coated NiO was ~5 μm (S-5) and ~10 μm (S-10). The fastest response and recovery times for all VOCs were less than 80 s and 120 s, respectively. The highest response (Rg/Ra = 1.5 for 5 ppm ethanol) was observed at 350 °C for both sensors. Sensors were also tested in two different humidity conditions (40% and 90% r.h.). The humidity did not significantly influence the observed sensitivity of the films. Furthermore, S-10 NiO showed only a 3% drift in the baseline resistance between the two humidity conditions, making our sensor humidity-tolerant compared to traditional n-type sensors. Thus, we propose thick-film NiO (10 μm) sensing material as an interesting alternative VOC sensor that is fast and humidity-tolerant. Full article
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Article
Nickel Manganite-Sodium Alginate Nano-Biocomposite for Temperature Sensing
Chemosensors 2021, 9(9), 241; https://doi.org/10.3390/chemosensors9090241 - 27 Aug 2021
Cited by 2 | Viewed by 755
Abstract
Nanocrystalline nickel manganite (NiMn2O4) powder with a pure cubic spinel phase structure was synthesized via sol-gel combustion and characterized with XRD, FT-IR, XPS and SEM. The powder was mixed with sodium alginate gel to form a nano-biocomposite gel, dried [...] Read more.
Nanocrystalline nickel manganite (NiMn2O4) powder with a pure cubic spinel phase structure was synthesized via sol-gel combustion and characterized with XRD, FT-IR, XPS and SEM. The powder was mixed with sodium alginate gel to form a nano-biocomposite gel, dried at room temperature to form a thick film and characterized with FT-IR and SEM. DC resistance and AC impedance of sensor test structures obtained by drop casting the nano-biocomposite gel onto test interdigitated PdAg electrodes on an alumina substrate were measured in the temperature range of 20–50 °C at a constant relative humidity (RH) of 50% and at room temperature (25 °C) in the RH range of 40–90%. The material constant obtained from the measured decrease in resistance with temperature was determined to be 4523 K, while the temperature sensitivity at room temperature (25 °C) was −5.09%/K. Analysis of the complex impedance plots showed a dominant influence of grains. The decrease in complex impedance with increase in temperature confirmed the negative temperature coefficient effect. The grain resistance and grain relaxation frequency were determined using an equivalent circuit. The activation energy for conduction was determined as 0.45 eV from the temperature dependence of the grain resistance according to the small polaron hopping model, while the activation energy for relaxation was 0.43 eV determined from the Arrhenius dependence of the grain relaxation frequency on temperature. Full article
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Article
UV-Responsive Screen-Printed Porous ZnO Nanostructures on Office Paper for Sustainable and Foldable Electronics
Chemosensors 2021, 9(8), 192; https://doi.org/10.3390/chemosensors9080192 - 24 Jul 2021
Cited by 6 | Viewed by 1382
Abstract
The fabrication of low-cost, flexible, and recyclable electronic devices has been the focus of many research groups, particularly for integration in wearable technology and the Internet of Things (IoT). In this work, porous zinc oxide (ZnO) nanostructures are incorporated as a UV sensing [...] Read more.
The fabrication of low-cost, flexible, and recyclable electronic devices has been the focus of many research groups, particularly for integration in wearable technology and the Internet of Things (IoT). In this work, porous zinc oxide (ZnO) nanostructures are incorporated as a UV sensing material into the composition of a sustainable water-based screen-printable ink composed of carboxymethyl cellulose (CMC). The formulated ink is used to fabricate flexible and foldable UV sensors on ubiquitous office paper. The screen-printed CMC/ZnO UV sensors operate under low voltage (≤2 V) and reveal a stable response over several on/off cycles of UV light exposure. The devices reach a response current of 1.34 ± 0.15 mA and a rise and fall time of 8.2 ± 1.0 and 22.0 ± 2.3 s, respectively. The responsivity of the sensor is 432 ± 48 mA W−1, which is the highest value reported in the literature for ZnO-based UV sensors on paper substrates. The UV-responsive devices display impressive mechanical endurance under folding, showing a decrease in responsivity of only 21% after being folded 1000 times. Their low-voltage operation and extreme folding stability indicate a bright future for low-cost and sustainable flexible electronics, showing potential for low-power wearable applications and smart packaging. Full article
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Article
A Magnetic Nanocomposite Modifier for Improved Ultrasensitive Detection of Hexavalent Chromium in Water Samples
Chemosensors 2021, 9(8), 189; https://doi.org/10.3390/chemosensors9080189 - 22 Jul 2021
Viewed by 1115
Abstract
In this work, different electrodes were employed for the determination of Cr(VI) by the cathodic square-wave voltammetry (SWV) technique and the square-wave adsorptive stripping voltammetry (SWAdSV) technique in combination with diethylenetriaminepentaacetic acid. Using SWV, a comparison of the analytical performance of the bare [...] Read more.
In this work, different electrodes were employed for the determination of Cr(VI) by the cathodic square-wave voltammetry (SWV) technique and the square-wave adsorptive stripping voltammetry (SWAdSV) technique in combination with diethylenetriaminepentaacetic acid. Using SWV, a comparison of the analytical performance of the bare glassy carbon electrode (GCE), ex situ electrodes (antimony-film—SbFE, copper-film—CuFE, and bismuth-film—BiFE), and the GCE modified with a new magnetic nanocomposite (MNC) material was performed. First, the MNC material was synthesized, i.e., [email protected]2@Lys, where MNPs stands for magnetic maghemite nanoparticles, coated with a thin amorphous silica (SiO2) layer, which was additionally functionalized with derived lysine (Lys). The crystal structure of the prepared MNCs was confirmed by X-ray powder diffraction (XRD), while the morphology and nano-size of the MNCs were investigated by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), where TEM was additionally used to observe the MNP core and silica layer thickness. The presence of functional groups of the MNCs was investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and surface analysis was performed by X-ray photoelectron spectroscopy (XPS). The hydrophilicity of the modified electrodes was also tested by static contact angle measurements. Then, [email protected]2@Lys was applied onto the electrodes and used with the SWV and SWAdSV techniques. All electrodes tested with the SWV technique were effective for Cr(VI) trace determination. On the other hand, the SWAdSV technique was required for ultra-trace determination of Cr(VI). Using the SWAdSV technique, it was shown that a combination of ex situ BiFE with the deposited [email protected]2@Lys resulted in excellent analytical performance (LOQ = 0.1 µg/L, a linear concentration range of 0.2–2.0 µg/L, significantly higher sensitivity compared to the SWV technique, an RSD representing reproducibility of 9.0%, and an average recovery of 98.5%). The applicability of the latter system was also demonstrated for the analysis of a real sample. Full article
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Article
Sensing Properties of NiO Loaded SnO2 Nanoparticles—Specific Selectivity to H2S
Chemosensors 2021, 9(6), 125; https://doi.org/10.3390/chemosensors9060125 - 01 Jun 2021
Cited by 3 | Viewed by 1325
Abstract
NiO-loaded SnO2 powders were prepared involving two chemical procedures. The mesoporous SnO2 support was synthesized by a hydrothermal route using Brij 35 non-ionic surfactant as a template. The nickel loadings of 1 and 10 wt.%. NiO were deposited by the wet [...] Read more.
NiO-loaded SnO2 powders were prepared involving two chemical procedures. The mesoporous SnO2 support was synthesized by a hydrothermal route using Brij 35 non-ionic surfactant as a template. The nickel loadings of 1 and 10 wt.%. NiO were deposited by the wet impregnation method. The H2S sensing properties of xNiO-(1-x)SnO2 (x = 0, 1, 10%) thick layers deposited onto commercial substrates have been investigated with respect to different potential interfering gases (NO2, CO, CO2, CH4, NH3 and SO2) over a wide range of operating temperatures and relative humidity specific for in-field conditions. Following the correlation of the sensing results with the morphological ones, 1wt.% NiO/SnO2 was selected for simultaneous electrical resistance and work function investigations. The purpose was to depict the sensing mechanism by splitting between specific changes over the electron affinity induced by the surface coverage with hydroxyl dipoles and over the band bending induced by the variable surface charge under H2S exposure. Thus, it was found that different gas-interaction partners are dependent upon the amount of H2S, mirrored through the threshold value of 5 ppm H2S, which from an applicative point of view, represents the lower limit of health effects, an eight-hour TWA. Full article
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Article
Synthesis, Characterization and Gas Sensing Study of ZnO-SnO2 Nanocomposite Thin Films
Chemosensors 2021, 9(6), 124; https://doi.org/10.3390/chemosensors9060124 - 30 May 2021
Cited by 10 | Viewed by 1650
Abstract
Thin nanocomposite films composed of ZnO and SnO2 at 0.5–5 mol.% concentrations were synthesized by a new solid-phase low-temperature pyrolysis under the developed protocols. This hetero-oxide material was thoroughly studied by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy [...] Read more.
Thin nanocomposite films composed of ZnO and SnO2 at 0.5–5 mol.% concentrations were synthesized by a new solid-phase low-temperature pyrolysis under the developed protocols. This hetero-oxide material was thoroughly studied by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques to be compared with electrical and gas-sensing properties. We have found that the films have a poly-nanocrystal structure of ZnO and SnO2 crystals with characteristic grain sizes at 10–15 nm range. When comparing the chemiresistive response of the films with varied tin dioxide content, the sample of Sn:Zn optimum ratio taken as 1:99 yields 1.5-fold improvement upon to 5–50 ppm NO2 exposure at 200 °C. We argue that these remarkable changes have matured from both a reducing the intergrain potential barrier down to 0.58 eV and increasing the concentration of anionic vacancies at this rational composite. The results demonstrate that solid-phase low-temperature pyrolysis is a powerful technique for adjusting the functional gas-sensing properties of hetero-oxide film via modifying the ratio of the oxide components. Full article
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Article
Dual Transduction of H2O2 Detection Using ZnO/Laser-Induced Graphene Composites
Chemosensors 2021, 9(5), 102; https://doi.org/10.3390/chemosensors9050102 - 05 May 2021
Cited by 7 | Viewed by 1397
Abstract
Zinc oxide (ZnO)/laser-induced graphene (LIG) composites were prepared by mixing ZnO, grown by laser-assisted flow deposition, with LIG produced by laser irradiation of a polyimide, both in ambient conditions. Different ZnO:LIG ratios were used to infer the effect of this combination on the [...] Read more.
Zinc oxide (ZnO)/laser-induced graphene (LIG) composites were prepared by mixing ZnO, grown by laser-assisted flow deposition, with LIG produced by laser irradiation of a polyimide, both in ambient conditions. Different ZnO:LIG ratios were used to infer the effect of this combination on the overall composite behavior. The optical properties, assessed by photoluminescence (PL), showed an intensity increase of the excitonic-related recombination with increasing LIG amounts, along with a reduction in the visible emission band. Charge-transfer processes between the two materials are proposed to justify these variations. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy evidenced increased electron transfer kinetics and an electrochemically active area with the amount of LIG incorporated in the composites. As the composites were designed to be used as transducer platforms in biosensing devices, their ability to detect and quantify hydrogen peroxide (H2O2) was assessed by both PL and CV analysis. The results demonstrated that both methods can be employed for sensing, displaying slightly distinct operation ranges that allow extending the detection range by combining both transduction approaches. Moreover, limits of detection as low as 0.11 mM were calculated in a tested concentration range from 0.8 to 32.7 mM, in line with the values required for their potential application in biosensors. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Prospects of Palladium (II) Oxide Nanostructure Application in Gas Sensing
Authors: Alexander Samoylov1, Goran Karapetrov2, Alexey Shaposhnik3
Affiliation: 1Department of Chemistry, Voronezh State University, Voronezh, Russian Federation 2Department of Physics, Drexel University, Philadelphia, PA 19104, USA 3Department of Chemistry, Voronezh State Agricultural University, Voronezh, Russian Federation
Abstract: In this review article we present the current state of the art of palladium (II) oxide nanostructure application in gas sensing. In this area the initial investigations showed that bulk doping and surface modification of traditional n-type conductivity metal oxides (SnO2, ZnO, In2O3, WO3, and TiO2) using palladium (II) oxide nanostructures could effectively increase their sensitivity and selectivity towards the reducing gases. During the last five years it has been obtained the strong evidence that functional properties of sensors based on p-type conductivity palladium (II) oxide nanostructures could be utilized at detection of both the reducing and oxidizing gases. It has been proposed that the variation of palladium (II) oxide nanostructure composition within the non-stoichiometric region and its doping with aliovalent cations can effectively be used to optimize the functional properties of palladium (II) oxide gas sensors.

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