Chemosensors

2024

Jump to: 2023, 2022, 2021

26 pages, 6242 KiB

Open AccessArticle

Wireless Sensor Node for Chemical Agent Detection

by Zabdiel Brito-Brito, Jesús Salvador Velázquez-González, Fermín Mira, Antonio Román-Villarroel, Xavier Artiga, Satyendra Kumar Mishra, Francisco Vázquez-Gallego, Jung-Mu Kim, Eduardo Fontana, Marcos Tavares de Melo and Ignacio Llamas-Garro

Chemosensors 2024, 12(9), 185; https://doi.org/10.3390/chemosensors12090185 - 11 Sep 2024

Viewed by 851

Abstract

In this manuscript, we present in detail the design and implementation of the hardware and software to produce a standalone wireless sensor node, called SensorQ system, for the detection of a toxic chemical agent. The proposed wireless sensor node prototype is composed of [...] Read more.

In this manuscript, we present in detail the design and implementation of the hardware and software to produce a standalone wireless sensor node, called SensorQ system, for the detection of a toxic chemical agent. The proposed wireless sensor node prototype is composed of a micro-controller unit (MCU), a radio frequency (RF) transceiver, a dual-band antenna, a rechargeable battery, a voltage regulator, and four integrated sensing devices, all of them integrated in a package with final dimensions and weight of 200 × 80 × 60 mm and 0.422 kg, respectively. The proposed SensorQ prototype operates using the Long-Range (LoRa) wireless communication protocol at 2.4 GHz, with a sensor head implemented on a hetero-core fiber optic structure supporting the surface plasmon resonance (SPR) phenomenon with a sensing section (L = 10 mm) coated with titanium/gold/titanium and a chemically sensitive material (zinc oxide) for the detection of Di-Methyl Methyl Phosphonate (DMMP) vapor in the air, a simulant of the toxic nerve agent Sarin. The transmitted spectra with respect to different concentrations of DMMP vapor in the air were recorded, and then the transmitted power for these concentrations was calculated at a wavelength of 750 nm. The experimental results indicate the feasibility of detecting DMMP vapor in air using the proposed optical sensor head, with DMMP concentrations in the air of 10, 150, and 150 ppm in this proof of concept. We expect that the sensor and wireless sensor node presented herein are promising candidates for integration into a wireless sensor network (WSN) for chemical warfare agent (CWA) detection and contaminated site monitoring without exposure of armed forces. Full article

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14 pages, 3199 KiB

Open AccessArticle

Gas Sensing with Nanoporous In₂O₃ under Cyclic Optical Activation: Machine Learning-Aided Classification of H₂ and H₂O

by Dominik Baier, Alexander Krüger, Thorsten Wagner, Michael Tiemann and Christian Weinberger

Chemosensors 2024, 12(9), 178; https://doi.org/10.3390/chemosensors12090178 - 3 Sep 2024

Viewed by 796

Abstract

Clean hydrogen is a key aspect of carbon neutrality, necessitating robust methods for monitoring hydrogen concentration in critical infrastructures like pipelines or power plants. While semiconducting metal oxides such as In₂O₃ can monitor gas concentrations down to the ppm range, [...] Read more.

Clean hydrogen is a key aspect of carbon neutrality, necessitating robust methods for monitoring hydrogen concentration in critical infrastructures like pipelines or power plants. While semiconducting metal oxides such as In₂O₃ can monitor gas concentrations down to the ppm range, they often exhibit cross-sensitivity to other gases like H₂O. In this study, we investigated whether cyclic optical illumination of a gas-sensitive In₂O₃ layer creates identifiable changes in a gas sensor’s electronic resistance that can be linked to H₂ and H₂O concentrations via machine learning. We exposed nanostructured In₂O₃ with a large surface area of 95 m² g⁻¹ to H₂ concentrations (0–800 ppm) and relative humidity (0–70%) under cyclic activation utilizing blue light. The sensors were tested for 20 classes of gas combinations. A support vector machine achieved classification rates up to 92.0%, with reliable reproducibility (88.2 ± 2.7%) across five individual sensors using 10-fold cross-validation. Our findings suggest that cyclic optical activation can be used as a tool to classify H₂ and H₂O concentrations. Full article

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13 pages, 3349 KiB

Open AccessArticle

The Effect of Loading W&V:TiO₂ Nanoparticles with Noble Metals for CH₄ Detection

by Monica Scarisoreanu, Izabela Constantinoiu, Evghenii Goncearenco, Iuliana P. Morjan, Valentin Serban Teodorescu and Cristian Viespe

Chemosensors 2024, 12(8), 160; https://doi.org/10.3390/chemosensors12080160 - 9 Aug 2024

Viewed by 711

Abstract

TiO₂ nanoparticles (NPs) doped with W (W:TiO₂), double-doped with W and V (W&V:TiO₂), and loaded with noble metals (W:TiO₂ @Pt/Pd/Ag and W&V:TiO₂@Pt/Pd/Ag) were synthesized by laser pyrolysis followed by chemical impregnation and reduction. Due to [...] Read more.

TiO₂ nanoparticles (NPs) doped with W (W:TiO₂), double-doped with W and V (W&V:TiO₂), and loaded with noble metals (W:TiO₂ @Pt/Pd/Ag and W&V:TiO₂@Pt/Pd/Ag) were synthesized by laser pyrolysis followed by chemical impregnation and reduction. Due to its exceptional properties, TiO₂ is considered a key material being used in a wide range of applications. To improve its detection activity, the increase in the specific surface of the material, and the presence of defects in its structure play a decisive role. Doped and double-doped TiO₂ nanoparticles with dimensions in the range of 25–30 nm presented a mixture of phases corresponding to titania, with the anatase phase accounting for the majority (95%). By loading these nanoparticles with small particles of noble metals, a significant increase in the specific surface area by three or even five times the original values was achieved. Sensitive thin films for surface acoustic wave (SAW) sensors were made with the NPs, embedded in polyethyleneimine (PEI) polymer and deposited by spin-coating. Each sensor was tested at CH₄ concentrations between 0.4 and 2%, at room temperature, and the best results were obtained by the sensor with NPs doped with V and decorated with Pd, with a limit of detection (LOD) of 17 ppm, due to the strong catalytic effect of Pd. Full article

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15 pages, 42124 KiB

Open AccessArticle

Influence of Synthesis Method and Electrode Geometry on GHG-Sensing Properties of 5%Gd-Doped SnO₂

by Cristian Eugen Simion, Catalina Gabriela Mihalcea, Alexandra Corina Iacoban, Ion Viorel Dinu, Daniela Predoi, Ioana Dorina Vlaicu, Ovidiu Gabriel Florea and Adelina Stanoiu

Chemosensors 2024, 12(8), 148; https://doi.org/10.3390/chemosensors12080148 - 1 Aug 2024

Viewed by 823

Abstract

This study investigates the influence of synthesis methods and electrode geometry on the physico-chemical properties of 5%Gd-doped SnO₂. Two distinct synthesis routes, co-precipitation and hydrothermal growth, were employed, resulting in powders denoted as SnO₂: Gd 5%-CP and SnO₂ [...] Read more.

This study investigates the influence of synthesis methods and electrode geometry on the physico-chemical properties of 5%Gd-doped SnO₂. Two distinct synthesis routes, co-precipitation and hydrothermal growth, were employed, resulting in powders denoted as SnO₂: Gd 5%-CP and SnO₂: Gd 5%-HT. Morpho-structural and textural analyses reveal a uniform morphology consisting of quasi-spherical nanoparticles with dimensions of ~6 nm and mesoporosity for CP and a non-uniform morphology with larger nanoparticles of ~42 nm, with irregular shapes and macroporosity for the HT sample, respectively. The powders were deposited onto alumina substrates equipped with platinum interdigital electrodes with alternative gaps of 200 μm and 100 μm. The back-side heater allows for variation in the temperature of the layer. Sensing properties assessed under in-field-like atmospheres simulated by a computer-controlled Gas Mixing System reveal higher sensitivity to methane compared to carbon dioxide. Although the sensor signals did not differ quantitatively, they exhibited distinct saturation tendencies with an increasing methane concentration, attributed to the morpho-structure and porosity induced by the synthesis method. Differentiation was achieved by varying the interdigital gap of the electrodes, highlighting different sensor signals and conduction mechanisms, determined by the specific size of the crystallites. Full article

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28 pages, 9261 KiB

Open AccessReview

Recent Progress in MXenes-Based Materials for Gas Sensors and Photodetectors

by Praveen Kumar, Waseem Raza, Sanjeevamuthu Suganthi, Mohd Quasim Khan, Khursheed Ahmad and Tae Hwan Oh

Chemosensors 2024, 12(8), 147; https://doi.org/10.3390/chemosensors12080147 - 1 Aug 2024

Viewed by 1290

Abstract

Recently, a new class of two-dimensional (2D) materials known as MXenes, such as Ti₃C₂T_x, have received significant attention due to their exceptional structural and physiochemical properties. MXenes are widely used in a variety of applications, including sensors, [...] Read more.

Recently, a new class of two-dimensional (2D) materials known as MXenes, such as Ti₃C₂T_x, have received significant attention due to their exceptional structural and physiochemical properties. MXenes are widely used in a variety of applications, including sensors, due to their excellent charge transport, high catalytic, and conducive properties, making them superior materials for sensing applications. Sensing technology has attracted significant interest from the scientific community due to its wide range of applications. In particular, gas sensing technology is essential in today’s world due to its vital role in detecting various gases. Gas sensors have an essential role in real-time environmental monitoring health assessment, and the demand for air quality monitoring is driving the gas sensor market forward. Similarly, optical sensors are a related technology that can rapidly detect toxic substances and biomaterials using optical absorption spectroscopy. MXenes are highly desirable for gas and optical sensing applications due to their abundant active sites, metallic conductivity, optical properties, customizable surface chemistry, and exceptional stability. In this review article, we compile recent advancements in the development of gas sensors and optical sensors using MXenes and their composite materials. This review article would be beneficial for researchers working on the development of MXenes-based gas sensors and optical sensors. Full article

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23 pages, 2802 KiB

Open AccessArticle

Unveiling Hidden Insights in Gas Chromatography Data Analysis with Generative Adversarial Networks

by Namkyung Yoon, Wooyong Jung and Hwangnam Kim

Chemosensors 2024, 12(7), 131; https://doi.org/10.3390/chemosensors12070131 - 7 Jul 2024

Viewed by 1111

Abstract

The gas chromatography analysis method for chemical substances enables accurate analysis to precisely distinguish the components of a mixture. This paper presents a technique for augmenting time-series data of chemicals measured by gas chromatography instruments with artificial intelligence techniques such as generative adversarial [...] Read more.

The gas chromatography analysis method for chemical substances enables accurate analysis to precisely distinguish the components of a mixture. This paper presents a technique for augmenting time-series data of chemicals measured by gas chromatography instruments with artificial intelligence techniques such as generative adversarial networks (GAN). We propose a novel GAN algorithm called GCGAN for gas chromatography data, a unified model of autoencoder (AE) and GAN for effective time-series data learning with an attention mechanism. The proposed GCGAN utilizes AE to learn a limited number of data more effectively. We also build a layer of high-performance generative adversarial neural networks based on the analysis of the features of data measured by gas chromatography instruments. Then, based on the proposed learning, we synthesize the features embedded in the gas chromatography data into a feature distribution that extracts the temporal variability. GCGAN synthesizes the features embedded in the gas chromatography data into a feature distribution that extracts the temporal variability of the data over time. We have fully implemented the proposed GCGAN and experimentally verified that the data augmented by the GCGAN have the characteristic properties of the original gas chromatography data. The augmented data demonstrate high quality with the Pearson correlation coefficient, Spearman correlation coefficient, and cosine similarity all exceeding 0.9, significantly enhancing the performance of AI classification models by 40%. This research can be effectively applied to various small dataset domains other than gas chromatography data, where data samples are limited and difficult to obtain. Full article

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16 pages, 1285 KiB

Open AccessArticle

Combining PDMS Composite and Plasmonic Solid Chemosensors: Dual Determination of Ammonium and Hydrogen Sulfide as Biomarkers in a Saliva Single Test

by Belen Monforte-Gómez, Sergio Mallorca-Cebriá, Carmen Molins-Legua and Pilar Campíns-Falcó

Chemosensors 2024, 12(6), 94; https://doi.org/10.3390/chemosensors12060094 - 31 May 2024

Viewed by 686

Abstract

In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination [...] Read more.

In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination of ammonium and hydrogen sulfur in saliva using two colorimetric chemosensors. The ammonia reacts with 1,2-Naftoquinone 4 sulphonic acid (NQS) entrapped in polydimethylsiloxane (PDMS) and the hydrogen sulfide with AgNPs retained in a nylon membrane. The color changed from orange to brown in the case of ammonia chemosensors and from yellow to brown in the H₂S. The experimental conditions to be tested have been established. Both analytes have been determined from their gaseous form; these are ammonia from ammonium and hydrogen sulfur from hydrogen sulfur. Good figures of merit have been obtained by using both measuring strategies (reflectance diffuse and digitalized images). The acquired results show that both sensors can be used and provide good selectivity and sensitivity for the determination of these biomarkers in saliva. Both measurement strategies have provided satisfactory results for the real saliva samples (n = 15). Recoveries on spiked samples were between 70% and 100%. This methodology can lead to possible in situ diagnosis and monitoring of certain diseases and pathologies related with NH₄⁺ and/or H₂S, in a fast, simple, cheap and non-invasive way. Full article

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2023

Jump to: 2024, 2022, 2021

16 pages, 5106 KiB

Open AccessArticle

Pd-Nanoparticle-Decorated Multilayered MoS₂ Sheets for Highly Sensitive Hydrogen Sensing

by Shuja Bashir Malik, Fatima Ezahra Annanouch and Eduard Llobet

Chemosensors 2023, 11(11), 550; https://doi.org/10.3390/chemosensors11110550 - 26 Oct 2023

Cited by 2 | Viewed by 2238

Abstract

In this work, efficient hydrogen gas sensors based on multilayered p-type bare MoS₂ and Pd-decorated MoS₂ were fabricated. MoS₂ was deposited onto alumina transducers using an airbrushing technique to be used as a sensing material. Aerosol-assisted chemical vapor deposition (AACVD) [...] Read more.

In this work, efficient hydrogen gas sensors based on multilayered p-type bare MoS₂ and Pd-decorated MoS₂ were fabricated. MoS₂ was deposited onto alumina transducers using an airbrushing technique to be used as a sensing material. Aerosol-assisted chemical vapor deposition (AACVD) was used to decorate layered MoS₂ with Pd nanoparticles at 250 °C. The bare and Pd-decorated MoS₂ was characterized using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and Raman spectroscopy. The characterization results reveal the multilayered crystalline structure of MoS₂ with successful Pd decoration. The size of the Pd nanoparticles ranges from 15 nm to 23 nm. Gas sensing studies reveal that a maximum response of 55% is achieved for Pd-decorated MoS₂ operated at 150 °C to 100 ppm of H₂, which is clearly below the explosive limit (4%) in air. The higher sensitivity due to Pd nanoparticle decoration was owed to a spillover effect. This study reveals that the sensitivity of the sensors is highly dependent on the amount of Pd decoration. Moreover, sensor responses increase slightly when exposed to 50% relative humidity (RH at 25 °C). Full article

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16 pages, 6911 KiB

Open AccessEditor’s ChoiceArticle

Electro-Optical Nose for Indoor Air Quality Monitoring

by Víctor González, Félix Meléndez, Patricia Arroyo, Javier Godoy, Fernando Díaz, José Ignacio Suárez and Jesús Lozano

Chemosensors 2023, 11(10), 535; https://doi.org/10.3390/chemosensors11100535 - 11 Oct 2023

Cited by 5 | Viewed by 2346

Abstract

Nowadays, indoor air pollution is a major problem that affects human health. For that reason, measuring indoor air quality has an increasing interest. Electronic noses are low-cost instruments (compared with reference methods) capable of measuring air components and pollutants at different concentrations. In [...] Read more.

Nowadays, indoor air pollution is a major problem that affects human health. For that reason, measuring indoor air quality has an increasing interest. Electronic noses are low-cost instruments (compared with reference methods) capable of measuring air components and pollutants at different concentrations. In this paper, an electro-optical nose (electronic nose that includes optical sensors) with non-dispersive infrared sensors and metal oxide semiconductor sensors is used to measure gases that affect indoor air quality. To validate the developed prototype, different gas mixtures (CH₄ and CO₂) with variable concentrations and humidity values are generated to confirm the discrimination capabilities of the device. Principal Component Analysis (PCA) was used for dimensionality reduction purposes to show the measurements in a plot. Partial Least Squares Regression (PLS) was also performed to calculate the predictive capabilities of the device. PCA results using all the measurements from all the sensors obtained PC1 = 47% and PC2 = 10%; results are improved using only the relevant information of the sensors obtaining PC1 = 79% and PC2 = 9%. PLS results with CH₄ using only MOX sensors received an RMSE = 118.8. When using NDIR and MOX sensors, RMSE is reduced to 19.868; this tendency is also observed in CO₂ (RMSE = 116.35 with MOX and RMSE = 20.548 with MOX and NDIR). The results confirm that the designed electro-optical nose can detect different gas concentrations and discriminate between different mixtures of gases; also, a better correlation and dispersion is achieved. The addition of NDIR sensors gives better results in measuring specific gases, discrimination, and concentration prediction capabilities in comparison to electronic noses with metal oxide gas sensors. Full article

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15 pages, 5588 KiB

Open AccessArticle

Optical Dual Gas Sensor for Simultaneous Detection of Nitric Oxide and Oxygen

by Rispandi Mesin and Cheng-Shane Chu

Chemosensors 2023, 11(8), 454; https://doi.org/10.3390/chemosensors11080454 - 14 Aug 2023

Cited by 6 | Viewed by 1795

Abstract

This work presents a new optical dual sensor based on PtTFPP-containing electrospun fibers and CsPbBr₃ perovskite quantum dots (PQDs) for simultaneous detection of oxygen (O₂) and nitric oxide (NO) gases, wherein PtTFPP-containing electrospun fibers for O₂ sensing was based [...] Read more.

This work presents a new optical dual sensor based on PtTFPP-containing electrospun fibers and CsPbBr₃ perovskite quantum dots (PQDs) for simultaneous detection of oxygen (O₂) and nitric oxide (NO) gases, wherein PtTFPP-containing electrospun fibers for O₂ sensing was based on electrospinning process fabricated by platinum(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) complex immobilized in cellulose acetate (CA) matrix. CsPbBr₃ PQDs were used as NO-sensitive material and coated on the surface of PtTFPP-containing electrospun fibers. Both materials were excited by a UV LED with a central wavelength of 380 nm, and the fluorescence intensities of sensing materials were recorded and analyzed with a spectrometer. The experiment results show that the optical NO and O₂ sensors have linear Stern–Volmer plots, and the sensitivities are around 2.7 and 10.7, respectively. The response and recovery times of the optical NO sensor are 71 and 109 s, respectively. For optical O₂, response and recovery times are 60 and 65 s, respectively. The optical dual sensor with a new method based on fluorescent dye containing electrospun fibers and coated with CsPbBr₃ PQDs has been successfully developed to detect NO and O₂ gases simultaneously. The optical dual gas sensor provides great potential for practical applications with low cost and ease of fabrication. Full article

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15 pages, 5015 KiB

Open AccessArticle

Sub-ppm NO₂ Detection through Chipless RFID Sensor Functionalized with Reduced SnO₂

by Viviana Mulloni, Andrea Gaiardo, Giada Marchi, Matteo Valt, Lia Vanzetti, Massimo Donelli and Leandro Lorenzelli

Chemosensors 2023, 11(7), 408; https://doi.org/10.3390/chemosensors11070408 - 20 Jul 2023

Cited by 4 | Viewed by 1481

Abstract

NO₂ is an important environmental pollutant and is harmful to human health even at very low concentrations. In this paper, we propose a novel chipless RFID sensor able to work at room temperature and to detect sub-ppm concentration of NO₂ in [...] Read more.

NO₂ is an important environmental pollutant and is harmful to human health even at very low concentrations. In this paper, we propose a novel chipless RFID sensor able to work at room temperature and to detect sub-ppm concentration of NO₂ in the environment. The sensor is made of a metallic resonator covered with NO₂-sensitive tin oxide and works by monitoring both the frequency and the intensity of the output signal. The experimental measurements show a fast response (a few minutes) but a very slow recovery. The sensor could therefore be used for non-continuous threshold monitoring. However, we also demonstrated that the recovery can be strongly accelerated upon exposure to a UV source. This opens the way to the reuse of the sensor, which can be easily regenerated after prolonged exposure and recycled several times. Full article

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11 pages, 737 KiB

Open AccessArticle

Detection of Aroma Profile in Spanish Rice Paella during Socarrat Formation by Electronic Nose and Sensory Panel

by Juan Diego Barea-Ramos, José Pedro Santos, Jesús Lozano, María José Rodríguez, Ismael Montero-Fernández and Daniel Martín-Vertedor

Chemosensors 2023, 11(6), 342; https://doi.org/10.3390/chemosensors11060342 - 11 Jun 2023

Cited by 2 | Viewed by 2187

Abstract

Valencian paella is a world-famous dish that is originally from the Valencia Spanish region, in which rice is the basic ingredient along with others such as extra virgin olive oil, vegetables, seafood and/or meat. During the cooking process, the paella rice suffers a [...] Read more.

Valencian paella is a world-famous dish that is originally from the Valencia Spanish region, in which rice is the basic ingredient along with others such as extra virgin olive oil, vegetables, seafood and/or meat. During the cooking process, the paella rice suffers a loss of moisture and the socarrat is formed, being crunchy and brown in color. The objective of this work was to evaluate the aromas generated during the formation of socarrat in paella rice (P) by an electronic nose (E-nose), discriminating against the aromatic profile of white rice (WR), and validate it with sensory analysis and gas chromatography. The results of the sensory analysis showed a decrease in positive fruity and sweet aromas of some volatile compounds such as hexanal and nonanal, among others, and an increase in roasted aromas due to the appearance of furans and furanones compounds, which is probably associated with socarrat formation. The acrylamide content increased by 33.8–48.3% as the intensity of the thermal treatment rose. The higher value of acrylamide (179.5 ng g⁻¹) was achieved in P. The E-nose was sensitive to changes in the aromatic profile, and the PCA analysis explained 85.7% and 91.6% of the variance for WR and P, respectively. Furthermore, a strong clustering in the thermal treatments was observed, which is related to the composition of volatile compounds. Full article

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13 pages, 5903 KiB

Open AccessArticle

Colorimetric Gas Detection Using Molecular Devices and an RGB Sensor

by Javier Roales, Francisco G. Moscoso, Alejandro P. Vargas, Tânia Lopes-Costa and José M. Pedrosa

Chemosensors 2023, 11(2), 92; https://doi.org/10.3390/chemosensors11020092 - 27 Jan 2023

Cited by 8 | Viewed by 2846

Abstract

Spectrophotometry and colorimetry are among the most-used techniques for chemical and biological analyses, but the required equipment is often expensive and restricted to laboratory use. We present here a low-cost and portable color measuring device that can provide similar results to laboratory spectrophotometers [...] Read more.

Spectrophotometry and colorimetry are among the most-used techniques for chemical and biological analyses, but the required equipment is often expensive and restricted to laboratory use. We present here a low-cost and portable color measuring device that can provide similar results to laboratory spectrophotometers in color measuring applications. Our prototype was based on an RGB color sensor interfaced to a Raspberry Pi and mounted on custom sample holders with a dual illumination source for reflectance or transmittance measurements. To evaluate its capabilities for the detection of gases, we used two already-tested colorimetric molecular devices: Harrison’s reagent supported on porous TiO₂ films for the detection of phosgene, and mixed films of a porphyrinic metal–organic frameworks and polydimethylsiloxane for the detection of biogenic amines. The results showed that the prototype could accurately monitor the color change of the sensing devices when exposed to the analytes and that its versatility allowed for the measurement of samples with different characteristics. This inexpensive and portable prototype, able to run on a 5 V battery and work wirelessly, proved to be a valid alternative for color measuring when expensive spectrophotometers are not available, mobility is needed, or a full-spectral characterization is not necessary. Full article

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2022

Jump to: 2024, 2023, 2021

15 pages, 3338 KiB

Open AccessArticle

Nanostructured Diamond Composites for Multifunctional Sensing Applications

by Eric Y. Li, Elluz Pacheco, Andrew F. Zhou and Peter X. Feng

Chemosensors 2022, 10(11), 488; https://doi.org/10.3390/chemosensors10110488 - 17 Nov 2022

Cited by 3 | Viewed by 1707

Abstract

We report studies of multifunctional, nanostructured diamond composites that were fabricated using chemical vapor deposition (CVD) techniques. Grain sizes from micrometer, to submicron, nano, and ultrananocrystalline diamond (UNCD) were controlled by varying CH₄, hydrogen, and argon gas concentrations during the syntheses. [...] Read more.

We report studies of multifunctional, nanostructured diamond composites that were fabricated using chemical vapor deposition (CVD) techniques. Grain sizes from micrometer, to submicron, nano, and ultrananocrystalline diamond (UNCD) were controlled by varying CH₄, hydrogen, and argon gas concentrations during the syntheses. Scanning electron microscopy (SEM) and Raman scattering spectroscopy were used to investigate the morphologies, composites, and crystallinities of the films. Four multifunctional sensor prototypes were designed, fabricated, and tested, based on the four diamond materials of different grain sizes. The responses of the four prototypes to either pollution gas or UV light illumination were systematically investigated at different operating temperatures. Experimental data indicated the obtained UNCD composite from the low-cost simple CVD fabrication technique appeared to have very good sensitivities when exposed to low concentrations of H₂ or NH₃ gas with a decent response and fast recovery time. Furthermore, highly induced photocurrents from both microdiamond- and UNCD-based prototypes to deep UV illumination were also demonstrated, with responsivities up to 2750 mA/W and 550 mA/W at 250 nm wavelength, respectively. Overall, the fabricated UNCD prototypes displayed a good balance in performance for multifunctional sensor applications in terms of responsivity, stability, and repeatability. Full article

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13 pages, 2543 KiB

Open AccessArticle

Enhanced Gas Detection by Altering Gate Voltage Polarity of Polypyrrole/Graphene Field-Effect Transistor Sensor

by Xiaohui Tang, Jean-Pierre Raskin, Nicolas Reckinger, Yiyi Yan, Nicolas André, Driss Lahem and Marc Debliquy

Chemosensors 2022, 10(11), 467; https://doi.org/10.3390/chemosensors10110467 - 9 Nov 2022

Cited by 7 | Viewed by 2156

Abstract

This work introduces a new measurement methodology for enhancing gas detection by tuning the magnitude and polarity of back-gate voltage of a field-effect transistor (FET)-based sensor. The aim is to simultaneously strengthen the sensor response and accelerate the sensor recovery. In addition, this [...] Read more.

This work introduces a new measurement methodology for enhancing gas detection by tuning the magnitude and polarity of back-gate voltage of a field-effect transistor (FET)-based sensor. The aim is to simultaneously strengthen the sensor response and accelerate the sensor recovery. In addition, this methodology can consume less energy compared with conventional measurements by direct current bias. To illustrate the benefits of the proposed methodology, we fabricated and characterized a polypyrrole/graphene (PPy/G) FET sensor for ammonia (NH₃) detection. Our experiment, simulation and calculation results demonstrated that the redox reaction between the NH₃ molecules and the PPy/G sensitive layer could be controlled by altering the polarity and the magnitude of the back-gate voltage. This proof-of-principle measurement methodology, which solves the inherent contradiction between high response and slow recovery of the chemiresistive sensor, could be extended to detect other gases, so as to improve global gas measurement systems. It opens up a new route for FET-based gas sensors in practical applications. Full article

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21 pages, 20581 KiB

Open AccessArticle

Application of a Single-Type eNose to Discriminate the Brewed Aroma of One Caffeinated and Decaffeinated Encapsulated Espresso Coffee Type

by Jordi Palacín, Elena Rubies and Eduard Clotet

Chemosensors 2022, 10(10), 421; https://doi.org/10.3390/chemosensors10100421 - 13 Oct 2022

Cited by 2 | Viewed by 1962

Abstract

This paper assesses a custom single-type electronic nose (eNose) applied to differentiate the complex aromas generated by the caffeinated and decaffeinated versions of one encapsulated espresso coffee mixture type. The eNose used is composed of 16 single-type (identical) metal–oxide semiconductor (MOX) gas sensors [...] Read more.

This paper assesses a custom single-type electronic nose (eNose) applied to differentiate the complex aromas generated by the caffeinated and decaffeinated versions of one encapsulated espresso coffee mixture type. The eNose used is composed of 16 single-type (identical) metal–oxide semiconductor (MOX) gas sensors based on microelectromechanical system (MEMS). This eNose proposal takes advantage of the small but inherent sensing variability of MOX gas sensors in order to provide a multisensorial description of volatiles or aromas. Results have shown that the information provided with this eNose processed using LDA is able to successfully discriminate the complex aromas of one caffeinated and decaffeinated encapsulated espresso coffee type. Full article

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17 pages, 7400 KiB

Open AccessEditor’s ChoiceArticle

Au-Decorated Polyaniline-ZnO Electrospun Composite Nanofiber Gas Sensors with Enhanced Response to NO₂ Gas

by Maryam Bonyani, Seyed Mojtaba Zebarjad, Kamal Janghorban, Jin-Young Kim, Hyoun Woo Kim and Sang Sub Kim

Chemosensors 2022, 10(10), 388; https://doi.org/10.3390/chemosensors10100388 - 24 Sep 2022

Cited by 15 | Viewed by 2672

Abstract

Ternary systems are less studied for sensing applications due to complex synthesis procedures. However, they have more sources of resistance modulation, leading to an enhanced gas response. In this study, a ternary system, namely Au-decorated ZnO-polyaniline (PANI) composite nanofibers with different amounts of [...] Read more.

Ternary systems are less studied for sensing applications due to complex synthesis procedures. However, they have more sources of resistance modulation, leading to an enhanced gas response. In this study, a ternary system, namely Au-decorated ZnO-polyaniline (PANI) composite nanofibers with different amounts of PANI (10, 25, and 50 wt.%) were synthesized for NO₂ gas sensing studies. First, ZnO nanofibers were synthesized by electrospinning, and then an Au layer (9 nm) was coated on the ZnO nanofibers. Finally, PANI was coated onto the prepared Au-decorated ZnO nanofibers. NO₂ gas sensing investigations indicated that the sensor with 25 wt.% PANI had the best response to NO₂ gas at 300 °C. In addition, the optimized sensor exhibited high selectivity to NO₂ gas. The improved performance of the optimal gas sensor was attributed to the role of Au, the formation of ZnO-PANI heterojunctions, and the optimal amount of PANI. The promising effect of this ternary system for NO₂ sensing was demonstrated, and it can be extended to other similar systems. Full article

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15 pages, 5339 KiB

Open AccessArticle

Spinel Magnesium Ferrite (MgFe₂O₄): A Glycine-Assisted Colloidal Combustion and Its Potentiality in Gas-Sensing Application

by Digambar Nadargi, Ahmad Umar, Jyoti Nadargi, Jayvant Patil, Imtiaz Mulla, Sheikh Akbar and Sharad Suryavanshi

Chemosensors 2022, 10(9), 361; https://doi.org/10.3390/chemosensors10090361 - 9 Sep 2022

Cited by 9 | Viewed by 2660

Abstract

Herein, we describe the facile synthesis of spinel MgFe₂O₄ ferrite and its potential use as a gas sensor using a straightforward and reliable sol–gel approach, i.e., the glycine-assisted auto-combustion route. The novelty in obtaining the sensing material via the auto-combustion [...] Read more.

Herein, we describe the facile synthesis of spinel MgFe₂O₄ ferrite and its potential use as a gas sensor using a straightforward and reliable sol–gel approach, i.e., the glycine-assisted auto-combustion route. The novelty in obtaining the sensing material via the auto-combustion route is its inherent simplicity and capability to produce the material at an industry scale. The said cost-effective process makes use of simple metal salts (Mg and Fe-nitrates) and glycine in an aqueous solution, which leads to the formation of spinel MgFe₂O₄ ferrite. A single-phase crystallinity with crystallite sizes ranging between 36 and 41 nm was observed for the synthesized materials using the X-ray diffraction (XRD) technique. The porous morphologies of the synthesized materials caused by auto-ignition during the combustion process were validated by the microscopic investigations. The EDS analysis confirmed the constituted elements such as Mg, Fe, and O, without any impurity peaks. The gas-sensing ability of the synthesized ferrites was examined to detect various reducing gases such as LPG, ethanol, acetone, and ammonia. The ferrite showed the highest response (>80%) toward LPG with the response and recovery times of 15 s and 23 s, respectively. Though the sensor responded low toward ammonia (~30%), its response and recovery times were very quick, i.e., 7 s and 9 s, respectively. The present investigation revealed that the synthesized ferrite materials are good candidates for fabricating high-performance sensors for reducing gases in real-world applications. Full article

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14 pages, 4773 KiB

Open AccessArticle

Effects of Calcination Temperature on CO-Sensing Mechanism for NiO-Based Gas Sensors

by Adelina Stanoiu, Corneliu Ghica, Catalina G. Mihalcea, Daniela Ghica, Simona Somacescu, Ovidiu G. Florea and Cristian E. Simion

Chemosensors 2022, 10(5), 191; https://doi.org/10.3390/chemosensors10050191 - 19 May 2022

Cited by 7 | Viewed by 2612

Abstract

NiO-sensitive materials have been synthesized via the hydrothermal synthesis route and calcined in air at 400 °C and, alternatively, at 500 °C. Structural, morphological, and spectroscopic investigations were involved. As such, the XRD patterns showed a higher crystallinity degree for the NiO calcined [...] Read more.

NiO-sensitive materials have been synthesized via the hydrothermal synthesis route and calcined in air at 400 °C and, alternatively, at 500 °C. Structural, morphological, and spectroscopic investigations were involved. As such, the XRD patterns showed a higher crystallinity degree for the NiO calcined at 500 °C. Such an aspect is in line with the XPS data indicating a lower surface hydroxylation relative to NiO calcined at 400 °C. An HRTEM microstructural investigation revealed that the two samples differ essentially at the morphological level, having different sizes of the crystalline nanoparticles, different density of the surface defects, and preferential faceting according to the main crystallographic planes. In order to identify their specific gas-sensing mechanism towards CO exposure under the in-field atmosphere, the simultaneous evaluation of the electrical resistance and contact potential difference was carried out. The results allowed the decoupling of the water physisorption from the chemisorption of the ambient oxygen species. Thus, the specific CO interaction mechanism induced by the calcination temperature of NiO has been highlighted. Full article

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15 pages, 2305 KiB

Open AccessCommunication

Comparative Analysis of Derivative Parameters of Chemoresistive Sensor Signals for Gas Concentration Estimation

by Nina K. Plugotarenko, Tatiana N. Myasoedova, Sergey P. Novikov and Tatiana S. Mikhailova

Chemosensors 2022, 10(4), 126; https://doi.org/10.3390/chemosensors10040126 - 29 Mar 2022

Cited by 2 | Viewed by 2661

Abstract

Signals from resistive gas sensors based on zirconium dioxide and silicon–carbon films have been extensively investigated to estimate gas concentration. In this study, the change in the normalized resistance of the sensor’s response under NO₂ exposure is shown and the analysis of [...] Read more.

Signals from resistive gas sensors based on zirconium dioxide and silicon–carbon films have been extensively investigated to estimate gas concentration. In this study, the change in the normalized resistance of the sensor’s response under NO₂ exposure is shown and the analysis of the first and second derivatives of the response curves were carried out. A signal-processing scheme, reducing the effect of noise and signal drift, is proposed. The extreme of the second derivative of the sensor response, the initial reaction rate, and the slope of the curve of the approximating line in the coordinates of the Elovich equation are proposed as calibration dependencies. The calibration curves built from the values of the maximum second derivative turned out to be the most stable, with the lowest relative error in estimating gas concentration compared to the traditional fixed-time point method. Full article

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2021

Jump to: 2024, 2023, 2022

10 pages, 2340 KiB

Open AccessArticle

Silicon MEMS Thermocatalytic Gas Sensor in Miniature Surface Mounted Device Form

by Nikolay Samotaev, Pavel Dzhumaev, Konstantin Oblov, Alexander Pisliakov, Ivan Obraztsov, Csaba Ducso and Ferenc Biro

Chemosensors 2021, 9(12), 340; https://doi.org/10.3390/chemosensors9120340 - 3 Dec 2021

Cited by 7 | Viewed by 3311

Abstract

A reduced size thermocatalytic gas sensor was developed for the detection of methane over the 20% of the explosive concentration. The sensor chip is formed from two membranes with a 150 µm diameter heated area in their centers and covered with highly dispersed [...] Read more.

A reduced size thermocatalytic gas sensor was developed for the detection of methane over the 20% of the explosive concentration. The sensor chip is formed from two membranes with a 150 µm diameter heated area in their centers and covered with highly dispersed nano-sized catalyst and inert reference, respectively. The power dissipation of the chip is well below 70 mW at the 530 °C maximum operation temperature. The chip is mounted in a novel surface mounted metal-ceramic sensor package in the form-factor of SOT-89. The sensitivity of the device is 10 mV/v%, whereas the response and recovery times without the additional carbon filter over the chip are <500 ms and <2 s, respectively. The tests have shown the reliability of the new design concerning the hotplate stability and massive encapsulation, but the high degradation rate of the catalyst coupled with its modest chemical power limits the use of the sensor only in pulsed mode of operation. The optimized pulsed mode reduces the average power consumption below 2 mW. Full article

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17 pages, 3394 KiB

Open AccessArticle

Performance Analysis of MAU-9 Electronic-Nose MOS Sensor Array Components and ANN Classification Methods for Discrimination of Herb and Fruit Essential Oils

by Mansour Rasekh, Hamed Karami, Alphus Dan Wilson and Marek Gancarz

Chemosensors 2021, 9(9), 243; https://doi.org/10.3390/chemosensors9090243 - 31 Aug 2021

Cited by 41 | Viewed by 4080

Abstract

The recent development of MAU-9 electronic sensory methods, based on artificial olfaction detection of volatile emissions using an experimental metal oxide semiconductor (MOS)-type electronic-nose (e-nose) device, have provided novel means for the effective discovery of adulterated and counterfeit essential oil-based plant products sold [...] Read more.

The recent development of MAU-9 electronic sensory methods, based on artificial olfaction detection of volatile emissions using an experimental metal oxide semiconductor (MOS)-type electronic-nose (e-nose) device, have provided novel means for the effective discovery of adulterated and counterfeit essential oil-based plant products sold in worldwide commercial markets. These new methods have the potential of facilitating enforcement of regulatory quality assurance (QA) for authentication of plant product genuineness and quality through rapid evaluation by volatile (aroma) emissions. The MAU-9 e-nose system was further evaluated using performance-analysis methods to determine ways for improving on overall system operation and effectiveness in discriminating and classifying volatile essential oils derived from fruit and herbal edible plants. Individual MOS-sensor components in the e-nose sensor array were performance tested for their effectiveness in contributing to discriminations of volatile organic compounds (VOCs) analyzed in headspace from purified essential oils using artificial neural network (ANN) classification. Two additional statistical data-analysis methods, including principal regression (PR) and partial least squares (PLS), were also compared. All statistical methods tested effectively classified essential oils with high accuracy. Aroma classification with PLS method using 2 optimal MOS sensors yielded much higher accuracy than using all nine sensors. The accuracy of 2-group and 6-group classifications of essentials oils by ANN was 100% and 98.9%, respectively. Full article

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12 pages, 2489 KiB

Open AccessArticle

Selective Determination of Hydrogen Sulfide Using SnO₂–Ag Sensor Working in Non-Stationary Temperature Regime

by Alexey V. Shaposhnik, Pavel V. Moskalev, Alexey A. Zviagin, Margarita V. Duykova, Stanislav V. Ryabtsev, Dina A. A. Ghareeb and Alexey A. Vasiliev

Chemosensors 2021, 9(8), 203; https://doi.org/10.3390/chemosensors9080203 - 2 Aug 2021

Cited by 11 | Viewed by 2591

Abstract

The application of a non-stationary regime of temperature modulation in metal oxide semiconductor sensor based on SnO₂–Ag leads not only to a strongly increased sensor response, but also to a considerably improved sensor selectivity toward hydrogen sulfide. Selectivity with respect to [...] Read more.

The application of a non-stationary regime of temperature modulation in metal oxide semiconductor sensor based on SnO₂–Ag leads not only to a strongly increased sensor response, but also to a considerably improved sensor selectivity toward hydrogen sulfide. Selectivity with respect to other reducing gases (CO, NH₃, H₂) is about five orders of magnitude, enabling a correct selective determination of H₂S in the presence of interfering gas components. Full article

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13 pages, 2971 KiB

Open AccessArticle

Ionogels Based on a Single Ionic Liquid for Electronic Nose Application

by Wellington B. Gonçalves, Evelyn P. Cervantes, Ana C. C. S. Pádua, Gonçalo Santos, Susana I. C. J. Palma, Rosamaria W. C. Li, Ana C. A. Roque and Jonas Gruber

Chemosensors 2021, 9(8), 201; https://doi.org/10.3390/chemosensors9080201 - 30 Jul 2021

Cited by 10 | Viewed by 3407

Abstract

Ionogel are versatile materials, as they present the electrical properties of ionic liquids and also dimensional stability, since they are trapped in a solid matrix, allowing application in electronic devices such as gas sensors and electronic noses. In this work, ionogels were designed [...] Read more.

Ionogel are versatile materials, as they present the electrical properties of ionic liquids and also dimensional stability, since they are trapped in a solid matrix, allowing application in electronic devices such as gas sensors and electronic noses. In this work, ionogels were designed to act as a sensitive layer for the detection of volatiles in a custom-made electronic nose. Ionogels composed of gelatin and a single imidazolium ionic liquid were doped with bare and functionalized iron oxide nanoparticles, producing ionogels with adjustable target selectivity. After exposing an array of four ionogels to 12 distinct volatile organic compounds, the collected signals were analyzed by principal component analysis (PCA) and by several supervised classification methods, in order to assess the ability of the electronic nose to distinguish different volatiles, which showed accuracy above 98%. Full article

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32 pages, 5813 KiB

Open AccessReview

One-Dimensional Nanomaterials in Resistive Gas Sensor: From Material Design to Application

by Ze Wang, Lei Zhu, Shiyi Sun, Jianan Wang and Wei Yan

Chemosensors 2021, 9(8), 198; https://doi.org/10.3390/chemosensors9080198 - 30 Jul 2021

Cited by 60 | Viewed by 7383

Abstract

With a series of widespread applications, resistive gas sensors are considered to be promising candidates for gas detection, benefiting from their small size, ease-of-fabrication, low power consumption and outstanding maintenance properties. One-dimensional (1-D) nanomaterials, which have large specific surface areas, abundant exposed active [...] Read more.

With a series of widespread applications, resistive gas sensors are considered to be promising candidates for gas detection, benefiting from their small size, ease-of-fabrication, low power consumption and outstanding maintenance properties. One-dimensional (1-D) nanomaterials, which have large specific surface areas, abundant exposed active sites and high length-to-diameter ratios, enable fast charge transfers and gas-sensitive reactions. They can also significantly enhance the sensitivity and response speed of resistive gas sensors. The features and sensing mechanism of current resistive gas sensors and the potential advantages of 1-D nanomaterials in resistive gas sensors are firstly reviewed. This review systematically summarizes the design and optimization strategies of 1-D nanomaterials for high-performance resistive gas sensors, including doping, heterostructures and composites. Based on the monitoring requirements of various characteristic gases, the available applications of this type of gas sensors are also classified and reviewed in the three categories of environment, safety and health. The direction and priorities for the future development of resistive gas sensors are laid out. Full article

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17 pages, 3602 KiB

Open AccessArticle

The UV Effect on the Chemiresistive Response of ZnO Nanostructures to Isopropanol and Benzene at PPM Concentrations in Mixture with Dry and Wet Air

by Maksim A. Solomatin, Olga E. Glukhova, Fedor S. Fedorov, Martin Sommer, Vladislav V. Shunaev, Alexey S. Varezhnikov, Albert G. Nasibulin, Nikolay M. Ushakov and Victor V. Sysoev

Chemosensors 2021, 9(7), 181; https://doi.org/10.3390/chemosensors9070181 - 14 Jul 2021

Cited by 12 | Viewed by 3783

Abstract

Towards the development of low-power miniature gas detectors, there is a high interest in the research of light-activated metal oxide gas sensors capable to operate at room temperature (RT). Herein, we study ZnO nanostructures grown by the electrochemical deposition method over Si/SiO₂ [...] Read more.

Towards the development of low-power miniature gas detectors, there is a high interest in the research of light-activated metal oxide gas sensors capable to operate at room temperature (RT). Herein, we study ZnO nanostructures grown by the electrochemical deposition method over Si/SiO₂ substrates equipped by multiple Pt electrodes to serve as on-chip gas monitors and thoroughly estimate its chemiresistive performance upon exposing to two model VOCs, isopropanol and benzene, in a wide operating temperature range, from RT to 350 °C, and LED-powered UV illumination, 380 nm wavelength; the dry air and humid-enriched, 50 rel. %, air are employed as a background. We show that the UV activation allows one to get a distinctive chemiresistive signal of the ZnO sensor to isopropanol at RT regardless of the interfering presence of H₂O vapors. On the contrary, the benzene vapors do not react with UV-illuminated ZnO at RT under dry air while the humidity’s appearance gives an opportunity to detect this gas. Still, both VOCs are well detected by the ZnO sensor under heating at a 200–350 °C range independently on additional UV exciting. We employ quantum chemical calculations to explain the differences between these two VOCs’ interactions with ZnO surface by a remarkable distinction of the binding energies characterizing single molecules, which is −0.44 eV in the case of isopropanol and −3.67 eV in the case of benzene. The full covering of a ZnO supercell by H₂O molecules taken for the effect’s estimation shifts the binding energies to −0.50 eV and −0.72 eV, respectively. This theory insight supports the experimental observation that benzene could not react with ZnO surface at RT under employed LED UV without humidity’s presence, indifference to isopropanol. Full article

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25 pages, 8717 KiB

Open AccessReview

Strategies for Improving the Sensing Performance of Semiconductor Gas Sensors for High-Performance Formaldehyde Detection: A Review

by Zhenyu Yuan, Chang Yang and Fanli Meng

Chemosensors 2021, 9(7), 179; https://doi.org/10.3390/chemosensors9070179 - 14 Jul 2021

Cited by 36 | Viewed by 6100

Abstract

Formaldehyde is a poisonous and harmful gas, which is ubiquitous in our daily life. Long-term exposure to formaldehyde harms human body functions; therefore, it is urgent to fabricate sensors for the real-time monitoring of formaldehyde concentrations. Metal oxide semiconductor (MOS) gas sensors is [...] Read more.

Formaldehyde is a poisonous and harmful gas, which is ubiquitous in our daily life. Long-term exposure to formaldehyde harms human body functions; therefore, it is urgent to fabricate sensors for the real-time monitoring of formaldehyde concentrations. Metal oxide semiconductor (MOS) gas sensors is favored by researchers as a result of their low cost, simple operation and portability. In this paper, the mechanism of formaldehyde detection by gas sensors is introduced, and then the ways of ameliorating the response of gas sensors for formaldehyde detection in recent years are summarized. These methods include the control of the microstructure and morphology of sensing materials, the doping modification of matrix materials, the development of new semiconductor sensing materials, the outfield control strategy and the construction of the filter membrane. These five methods will provide a good prerequisite for the preparation of better performing formaldehyde gas sensors. Full article

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9 pages, 2571 KiB

Open AccessArticle

A Gas Sensor Based on Network Nanowire for H₂S Monitor in Construction Waste Landfill

by Pengyu Ren, Qingwei Shi and Lingling Qi

Chemosensors 2021, 9(7), 156; https://doi.org/10.3390/chemosensors9070156 - 25 Jun 2021

Cited by 2 | Viewed by 2119

Abstract

As an extremely harmful gas, H₂S gas is the major pollutant in construction waste landfill. Herein, a one-dimensional oxide nanomaterial was produced from a simple wet chemical method to serve as a H₂S gas sensing material. The SEM observation [...] Read more.

As an extremely harmful gas, H₂S gas is the major pollutant in construction waste landfill. Herein, a one-dimensional oxide nanomaterial was produced from a simple wet chemical method to serve as a H₂S gas sensing material. The SEM observation indicates that the nanomaterial with network structure is constructed by a lot of nanowires with an approximate diameter from 24 nm to 40 nm. The sensing film was formed on a ceramic substrate using a slurry composed of the as-prepared network nanowires. Furthermore, a gas sensing measurement was carried out to determine the gas sensing performances towards the H₂S gas. The detection results at different working temperature towards various gas concentrations demonstrate that the network nanowires-based sensor exhibits a higher gas response to H₂S as compared to that of the rod-like one. The optimum working temperature of the network and rod-like nanomaterials is both 300 °C, and the corresponding maximum gas response is 24.4 and 13.6, respectively. Namely, the gas response of the network-based gas sensor is almost larger than that of the rod-like oxide. Moreover, the network nanowires-based gas sensor display a faster gas response and recovery speed. In addition, the fabricated gas sensors all exhibit excellent repeatability. Such improved sensing properties may offer a promising potential to realize an efficient detection of harmful H₂S gas released from construction waste landfill. Full article

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16 pages, 2359 KiB

Open AccessArticle

Classification and Identification of Essential Oils from Herbs and Fruits Based on a MOS Electronic-Nose Technology

by Mansour Rasekh, Hamed Karami, Alphus Dan Wilson and Marek Gancarz

Chemosensors 2021, 9(6), 142; https://doi.org/10.3390/chemosensors9060142 - 16 Jun 2021

Cited by 63 | Viewed by 6870

Abstract

The frequent occurrence of adulterated or counterfeit plant products sold in worldwide commercial markets has created the necessity to validate the authenticity of natural plant-derived palatable products, based on product-label composition, to certify pricing values and for regulatory quality control (QC). The necessity [...] Read more.

The frequent occurrence of adulterated or counterfeit plant products sold in worldwide commercial markets has created the necessity to validate the authenticity of natural plant-derived palatable products, based on product-label composition, to certify pricing values and for regulatory quality control (QC). The necessity to confirm product authenticity before marketing has required the need for rapid-sensing, electronic devices capable of quickly evaluating plant product quality by easily measurable volatile (aroma) emissions. An experimental MAU-9 electronic nose (e-nose) system, containing a sensor array with 9 metal oxide semiconductor (MOS) gas sensors, was developed with capabilities to quickly identify and classify volatile essential oils derived from fruit and herbal edible-plant sources. The e-nose instrument was tested for efficacy to discriminate between different volatile essential oils present in gaseous emissions from purified sources of these natural food products. Several chemometric data-analysis methods, including pattern recognition algorithms, principal component analysis (PCA), and support vector machine (SVM) were utilized and compared. The classification accuracy of essential oils using PCA, LDA and QDA, and SVM methods was at or near 100%. The MAU-9 e-nose effectively distinguished between different purified essential oil aromas from herbal and fruit plant sources, based on unique e-nose sensor array responses to distinct, essential-oil specific mixtures of volatile organic compounds (VOCs). Full article

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15 pages, 1054 KiB

Open AccessArticle

A Hairpin DNA-Based Piezoelectric E-Nose: Exploring the Performances of Heptamer Loops for the Detection of Volatile Organic Compounds

by Sara Gaggiotti, Marcello Mascini, Angelo Cichelli, Michele Del Carlo and Dario Compagnone

Chemosensors 2021, 9(5), 115; https://doi.org/10.3390/chemosensors9050115 - 20 May 2021

Cited by 2 | Viewed by 2573

Abstract

A hairpin DNA (hpDNA) piezoelectric gas sensors array with heptamer loops as sensing elements was designed, realized, and challenged with pure volatile organic compounds VOCs and real samples (beer). The virtual binding versus five chemical classes (alcohols, aldehydes, esters, hydrocarbons, and ketones) of [...] Read more.

A hairpin DNA (hpDNA) piezoelectric gas sensors array with heptamer loops as sensing elements was designed, realized, and challenged with pure volatile organic compounds VOCs and real samples (beer). The virtual binding versus five chemical classes (alcohols, aldehydes, esters, hydrocarbons, and ketones) of the entire combinatorial library of heptamer loops (16,384 elements) was studied by molecular modelling. Six heptamer loops, having the largest variance in binding the chemical classes, were selected to build the array. The six gas sensors were realized by immobilizing onto gold nanoparticles (AuNPs) via a thiol spacer the hpDNA constituted by the heptamer loops and the same double helix stem of four base pairs (GAAG at 5′ and CTTC at 3′ end). The HpDNA-AuNP was used to modify the surface of 20 MHz quartz crystal microbalances (QCMs). The realized E-nose was able to clearly discriminate among 15 pure VOCs of different chemical classes, as demonstrated by hierarchical cluster analysis. The analysis of real beer samples during fermentation was also carried out. In such a challenging matrix consisting of 23 different VOCs, the hpDNA E-nose with heptamer loops was able to discriminate among different fermentation times with high success rate. Class assignment using the Bayes theorem gave an excellent 98% correct beer samples classification in cross-validation. Full article

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