Chemosensors

14 pages, 4188 KiB

Open AccessArticle

Design of A Low-Cost and Disposable Paper-Based Immunosensor for the Rapid and Sensitive Detection of Aflatoxin B1

by Fernanda L. Migliorini, Danilo M. dos Santos, Andrey C. Soares, Luiz H. C. Mattoso, Osvaldo N. Oliveira, Jr. and Daniel S. Correa

Chemosensors 2020, 8(3), 87; https://doi.org/10.3390/chemosensors8030087 - 20 Sep 2020

Cited by 34 | Viewed by 4933

Abstract

We report a paper-based electrochemical immunosensor made with sustainable materials to detect aflatoxin B1 (AFB1), a highly toxic, carcinogenic mycotoxin found in food. The immunosensor was prepared with a waterproof paper substrate and low-cost graphite-based conductive ink through a simple cut-printing method. The [...] Read more.

We report a paper-based electrochemical immunosensor made with sustainable materials to detect aflatoxin B1 (AFB1), a highly toxic, carcinogenic mycotoxin found in food. The immunosensor was prepared with a waterproof paper substrate and low-cost graphite-based conductive ink through a simple cut-printing method. The working electrode was functionalized with a drop-cast film of multiwalled carbon nanotubes (MWCNT)/chitosan on which a layer of anti-AFB1 monoclonal antibodies was immobilized covalently. The architecture of the immunosensor was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and electrochemical impedance spectroscopy (EIS), including the effective immobilization of the active layer of anti-AFB1. With EIS as the principle of detection, the immunosensor could detect AFB1 in the range from 1 to 30 ng·mL⁻¹, and detection limit of 0.62 ng·mL⁻¹. This sensitivity is sufficient to detect AFB1 in food according to regulatory agencies. The immunosensor exhibited good repeatability, reproducibility, stability, and selectivity in experiments with a possible interferent. Furthermore, detection of AFB1 in maize flour samples yielded recovery of 97–99%, in a demonstration of the possible use of the paper-based immunosensor to detect AFB1 using extraction solutions from food samples. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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12 pages, 1426 KiB

Open AccessArticle

Screen-Printed Sensor Based on Potentiometric Transduction for Free Bilirubin Detection as a Biomarker for Hyperbilirubinemia Diagnosis

by Ayman H. Kamel, Abd El-Galil E. Amr, Hoda R. Galal, Mohamed A. Al-Omar and Abdulrahman A. Almehizia

Chemosensors 2020, 8(3), 86; https://doi.org/10.3390/chemosensors8030086 - 18 Sep 2020

Cited by 15 | Viewed by 3296

Abstract

Novel reliable and cost-effective potentiometric screen-printed sensors for free bilirubin (BR) detection were presented. The sensors were fabricated using ordered mesoporous carbon (OMC) as an ion-to-electron transducer. The ion-association complex [Ni(bphen)₃]²⁺[BR]²⁻ was utilized as a sensory recognition material [...] Read more.

Novel reliable and cost-effective potentiometric screen-printed sensors for free bilirubin (BR) detection were presented. The sensors were fabricated using ordered mesoporous carbon (OMC) as an ion-to-electron transducer. The ion-association complex [Ni(bphen)₃]²⁺[BR]²⁻ was utilized as a sensory recognition material in the plasticized Polyvinyl Chloride (PVC) membrane. The membrane was drop-casted on the OMC layer, which is attached on a carbon conductor (2-mm diameter). In a 50 mM phosphate solution of pH 8.5, the electrodes offered a Nernstian slope of −26.8 ± 1.1 (r² = 0.9997) mV/decade with a range of linearity 1.0 × 10⁻⁶–1 × 10⁻² M towards free bilirubin with a detection limit 8.8 × 10⁻⁷ M (0.52 µg/mL). The presented sensors offered good features in terms of reliability, ease of design, high potential stability, high specificity and good accuracy and precision. Chronopotentiometric and electrochemical impedance spectrometric measurements were used for short-term potential stability and interfacial capacitance calculations. The sensors were used for the determination of free bilirubin in biological fluids. The data obtained are fairly well consistent with those obtained by the reference spectophotometric method. Based on the interaction of free BR with albumin (1:1), the sensors were also utilized for the assessment of albumin in human serum. Full article

(This article belongs to the Section Applied Chemical Sensors)

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9 pages, 474 KiB

Open AccessPerspective

General Conceptual Framework of Future Wearables in Healthcare: Unified, Unique, Ubiquitous, and Unobtrusive (U4) for Customized Quantified Output

by Mostafa Haghi and Thomas M. Deserno

Chemosensors 2020, 8(3), 85; https://doi.org/10.3390/chemosensors8030085 - 15 Sep 2020

Cited by 8 | Viewed by 3990

Abstract

We concentrate on the importance and future conceptual development of wearable devices as the major means of personalized healthcare. We discuss and address the role of wearables in the new era of healthcare in proactive medicine. This work addresses the behavioral, environmental, physiological, [...] Read more.

We concentrate on the importance and future conceptual development of wearable devices as the major means of personalized healthcare. We discuss and address the role of wearables in the new era of healthcare in proactive medicine. This work addresses the behavioral, environmental, physiological, and psychological parameters as the most effective domains in personalized healthcare, and the wearables are categorized according to the range of measurements. The importance of multi-parameter, multi-domain monitoring and the respective interactions are further discussed and the generation of wearables based on the number of monitoring area(s) is consequently formulated. Full article

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17 pages, 2401 KiB

Open AccessArticle

Interaction of Several Toxic Heterocarbonyl Gases with Polypyrrole as a Potential Gas Sensor

by Francisco C. Franco

Chemosensors 2020, 8(3), 84; https://doi.org/10.3390/chemosensors8030084 - 14 Sep 2020

Cited by 8 | Viewed by 2974

Abstract

The interactions of the toxic heterocarbonyl gases phosgene, carbonyl fluoride, formaldehyde, carbonyl sulfide, and acetone with polypyrrole as a toxic heterocarbonyl gas sensor, were extensively studied by density functional theory (DFT). The Becke 3-parameter, Le^e-Yang-Parr (B3LYP) exchange-correlation functional methods were first [...] Read more.

The interactions of the toxic heterocarbonyl gases phosgene, carbonyl fluoride, formaldehyde, carbonyl sulfide, and acetone with polypyrrole as a toxic heterocarbonyl gas sensor, were extensively studied by density functional theory (DFT). The Becke 3-parameter, Le^e-Yang-Parr (B3LYP) exchange-correlation functional methods were first tested against several high-level DFT methods employing the Dunning’s double-ζ and triple-ζ basis sets and were found to be sufficient in describing the non-covalent interactions involved in this study. The interaction of pyrrole with the heterocarbonyl gases resulted in changes in the structure and optoelectronic properties of the polymer and it was observed that acetone and formaldehyde had the strongest H-bonding interaction with polypyrrole, while the interaction of phosgene and formaldehyde resulted in the lowest energy gap and may result in its high sensitivity towards these gases. The UV-Vis absorption revealed significant red-shifted first singlet excited states (E_{excited, 1st}) of the complexes and follows the same trend as the E_Gap values. It is shown that the E_{excited, 1st} was due to the π(HOMO_Py) ⟶ π*(LUMO_HC) transitions and the excited state at maximum absorption (E_{excited, max}) was due to the π(HOMO_Py) ⟶ π*(LUMO_Py) transitions. This study demonstrates the potential sensitivity and selectivity of polypyrrole as a toxic heterocarbonyl sensor. Full article

(This article belongs to the Section Applied Chemical Sensors)

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Graphical abstract

10 pages, 2555 KiB

Open AccessArticle

Peroxides and Bisphenols Detection in Extra Virgin Olive Oil (EVOO) by Plasmonic Nanodomes Transducers

by Adriano Colombelli, Daniela Lospinoso, Maria Grazia Manera and Roberto Rella

Chemosensors 2020, 8(3), 83; https://doi.org/10.3390/chemosensors8030083 - 7 Sep 2020

Cited by 1 | Viewed by 2916

Abstract

Large-area nanostructured transducer for absorption opto-plasmonic measurements in the ultraviolet visible UV-VIS spectral range have been realized by colloidal lithography. The design and simulation performed guarantee the optical behaviour of the nanostructured transducers. Morphological characterization by AFM microscopy evidences the nanodome structure of [...] Read more.

Large-area nanostructured transducer for absorption opto-plasmonic measurements in the ultraviolet visible UV-VIS spectral range have been realized by colloidal lithography. The design and simulation performed guarantee the optical behaviour of the nanostructured transducers. Morphological characterization by AFM microscopy evidences the nanodome structure of the object realized in array configuration. A microfluidic device was optimized to perform measurements in real time. Qualitative evaluation of the peroxides’ and bisphenols’ concentration in extra virgin olive oil (EVOO) have been obtained by following the variation in the plasmonic resonance monitoring of a suitable array nanodome structure deposited onto a glass substrate. Comparison of the obtained results with laboratory-standard methodologies gives us guaranteed support of the potential of the realized technology. Full article

(This article belongs to the Section Applied Chemical Sensors)

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17 pages, 4881 KiB

Open AccessEditor’s ChoiceArticle

Graphene Oxide as a Sensing Material for Gas Detection Based on Nanomechanical Sensors in the Static Mode

by Gaku Imamura, Kosuke Minami, Kota Shiba, Kissan Mistry, Kevin P. Musselman, Mustafa Yavuz, Genki Yoshikawa, Koichiro Saiki and Seiji Obata

Chemosensors 2020, 8(3), 82; https://doi.org/10.3390/chemosensors8030082 - 2 Sep 2020

Cited by 22 | Viewed by 6606

Abstract

Graphene is a key material for gas sensing applications owing to its high specific surface area and vast chemical modification potential. To fully utilize the potential of graphene, a sensing platform independent of conductive properties is required. In this study, we employed membrane-type [...] Read more.

Graphene is a key material for gas sensing applications owing to its high specific surface area and vast chemical modification potential. To fully utilize the potential of graphene, a sensing platform independent of conductive properties is required. In this study, we employed membrane-type surface stress sensors (MSS)—A kind of nanomechanical sensor operated in the static mode—As a sensing platform and utilized graphene oxide (GO) as a gas sensing material. MSS detect surface stress caused by gas sorption; therefore, chemically modified graphene with low conductivity can be utilized as a gas sensing material. We evaluated the sensing performance of a GO-coated MSS by measuring its responses to five gases. We demonstrated with the GO-coated MSS the feasibility of GO as a gas sensing material for static mode nanomechanical sensors and revealed its high selectivity to water vapor. Moreover, we investigated the sensing mechanism of the GO-coated MSS by comparing it with the sensing performance of MSS coated with reduced graphene oxide and graphite powder and deduced key factors for sensitivity and selectivity. Considering the high sensitivity of the GO-coated MSS and the compact measurement system that MSS can realize, the present study provides a new perspective on the sensing applications of graphene. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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11 pages, 2726 KiB

Open AccessArticle

Rationalization of In-Situ Synthesized Plasmonic Paper for Colorimetric Detection of Glucose in Ocular Fluids

by Hyeok Jung Kim, Jiwoo Hyung and Hyeran Noh

Chemosensors 2020, 8(3), 81; https://doi.org/10.3390/chemosensors8030081 - 1 Sep 2020

Cited by 6 | Viewed by 3555

Abstract

Tear glucose is an intriguing biofluid that includes potential biomarkers. While many sensors have emerged nowadays, there is still demand for advanced sensors with nonenzymatic, simple, cost-effective sensing mechanism. Herein, we present a paper-based colorimetric assay by utilizing a gold nanoparticle formation. Experimental [...] Read more.

Tear glucose is an intriguing biofluid that includes potential biomarkers. While many sensors have emerged nowadays, there is still demand for advanced sensors with nonenzymatic, simple, cost-effective sensing mechanism. Herein, we present a paper-based colorimetric assay by utilizing a gold nanoparticle formation. Experimental characterization substantiated a mechanism in this in situ reduction. Scanning electron microscopy, UV-visible spectrometry, etc. were involved in the scrutiny. As a result, we reached for the rationale whereas the particle formation can be utilized for a glucose sensing using tears. This paper-based detection was insusceptible to physiological tear matrix, i.e., chloride ion effect, false-positive error and synergistic effect by antioxidants. In addition, we evaluated its analytical performance in an artificial tear assay. Of the obtained a linear regressions, the concentration range corresponded to the physiological or pathologic reference range. In addition, within the low-concentration range, a high correlation was resulted 0.965. Furthermore, we investigated statistical validation by employing the Bland–Altman plot. In the end sections of this paper, we denoted its ready-to-use merits by simplicity—as well as the further application of our plasmonic paper. Full article

(This article belongs to the Section Optical Chemical Sensors)

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16 pages, 2046 KiB

Open AccessArticle

Factors Influencing the Surface Functionalization of Citrate Stabilized Gold Nanoparticles with Cysteamine, 3-Mercaptopropionic Acid or l-Selenocystine for Sensor Applications

by Georgia I. Sakellari, Nicole Hondow and Philip H.E. Gardiner

Chemosensors 2020, 8(3), 80; https://doi.org/10.3390/chemosensors8030080 - 31 Aug 2020

Cited by 35 | Viewed by 8998

Abstract

Thiols and selenides bind to the surface of gold nanoparticles (AuNPs) and thus provide suitable platforms for the fabrication of sensors. However, the co-existence of adsorbed citrate on the surface of the nanoparticles can influence their functionalization behavior and potentially their sensing performance [...] Read more.

Thiols and selenides bind to the surface of gold nanoparticles (AuNPs) and thus provide suitable platforms for the fabrication of sensors. However, the co-existence of adsorbed citrate on the surface of the nanoparticles can influence their functionalization behavior and potentially their sensing performance measured by the extent of particle aggregation. In this study, the functionalization of purchased (7.3 ± 1.2 nm) and in-house prepared AuNPs (13.8 ± 1.2 nm), under the same experimental conditions with either cysteamine (Cys), 3-mercaptopropionic acid (3-MPA), or l-selenocystine (SeCyst) was investigated. ¹H-NMR measurements showed distinct citrate signatures on the in-house synthesized citrate-stabilized AuNPs, while no citrate signals were detected on the purchased AuNPs other than evidence of the presence of α-ketoglutaric acid. Carboxylate-containing species attributed to either citrate or α-ketoglutaric acid were identified in all functionalized AuNPs. ATR-FTIR spectroscopy confirmed the functionalization of AuNPs with Cys and 3-MPA, and energy dispersive X-ray (EDX) spectroscopy measurements suggested the formation of SeCyst functionalized AuNPs. Co-adsorption rather than displacement by the functionalizing agents and carboxylate-containing molecules was indicated, which for Cys and SeCyst functionalized AuNPs was also the aggregation limiting factor. In contrast, the behavior of 3-MPA functionalized AuNPs could be attributed to electrostatic repulsions between the functionalized groups. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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14 pages, 3845 KiB

Open AccessArticle

Copper-Containing Films Obtained by the Simple Citrate Sol–Gel Route for NO₂ Detection: Adsorption and Kinetic Study

by Tatiana N. Myasoedova, Nina K. Plugotarenko and Tatiana A. Moiseeva

Chemosensors 2020, 8(3), 79; https://doi.org/10.3390/chemosensors8030079 - 30 Aug 2020

Cited by 4 | Viewed by 2691

Abstract

The citrate sol–gel method was utilized for the fabrication of copper-containing films sensitive to NO₂ gas. Effect of annealing temperature on the film phase composition, morphology, and sensor response was studied. X-ray diffraction reveals the formation of Cu₂Cl(OH)₃ phase [...] Read more.

The citrate sol–gel method was utilized for the fabrication of copper-containing films sensitive to NO₂ gas. Effect of annealing temperature on the film phase composition, morphology, and sensor response was studied. X-ray diffraction reveals the formation of Cu₂Cl(OH)₃ phase at 250 °C and the CuO phase at 350 and 500 °C. It was found out that the films annealed at 250 °C and 350 °C showed the best sensor characteristics. The influence of thermal degradation on the probability of percolation effect in films and its connection to a decrease of gas sensitivity was studied. The kinetics of the NO₂ gas adsorption on the film’s surface was described following the Elovich model. Activation energy estimated from the ln(S) vs. 1/T plots was 252 and 30 kJ/mol for the films annealed at 250 and 350 °C, respectively. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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17 pages, 3999 KiB

Open AccessArticle

Film Carbon Veil-Based Electrode Modified with Triton X-100 for Nitrite Determination

by Natalia Yu. Stozhko, Maria A. Bukharinova, Ekaterina I. Khamzina, Aleksey V. Tarasov and Sergey V. Sokolkov

Chemosensors 2020, 8(3), 78; https://doi.org/10.3390/chemosensors8030078 - 28 Aug 2020

Cited by 13 | Viewed by 3517

Abstract

A film carbon veil-based electrode (FCVE) modified with non-ionic surfactant Triton X-100 (TrX100) has been developed for nitrite determination. A new simple and producible technique of hot lamination (heat sealing) has been used for the FCVE manufacturing. The paper presents the findings of [...] Read more.

A film carbon veil-based electrode (FCVE) modified with non-ionic surfactant Triton X-100 (TrX100) has been developed for nitrite determination. A new simple and producible technique of hot lamination (heat sealing) has been used for the FCVE manufacturing. The paper presents the findings of investigating the FCVE and the TrX100/FCVE by using voltammetry, chronoamperometry, and scanning electron microscopy. Modification of the electrode with TrX100 improves the hydrophilic property of its surface, which results in a larger electrode active area and higher sensitivity. Optimal conditions for nitrite determination with the use of the TrX100/FCVE have been identified. The linear range (LR) and the limit of detection (LOD) are 0.1–100 μM and 0.01 μM, respectively. The relative standard deviation (RSD) does not exceed 2.3%. High selectivity of the sensor ensures its successful application for the analysis of real samples (sausage products and natural water). The obtained results accord well with the results of the standard spectrophotometric method. Full article

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8 pages, 6899 KiB

Open AccessLetter

Effect of Unmanned Aerial Vehicles on the Spatial Distribution of Analytes from Point Source

by Giovanni Li-Destri, Dario Menta, Carmelo Menta and Nunzio Tuccitto

Chemosensors 2020, 8(3), 77; https://doi.org/10.3390/chemosensors8030077 - 25 Aug 2020

Cited by 2 | Viewed by 2476

Abstract

We investigated and overcame the limitations associated with the use of unmanned aerial vehicles (UAVs) in the chemical mapping of pollutants coming from point source, as in the case of leaks’ detection. In particular, by simulating the pollutant spatial distribution in the absence [...] Read more.

We investigated and overcame the limitations associated with the use of unmanned aerial vehicles (UAVs) in the chemical mapping of pollutants coming from point source, as in the case of leaks’ detection. In particular, by simulating the pollutant spatial distribution in the absence and presence of a flying drone, we demonstrated that turbulent flows generated by UAVs can significantly limit the spatial accuracy of the mapping and the pollutant source detection. Finally, as this effect markedly depends on the proximity of the UAV to the pollutant source, we experimentally demonstrated that it is possible to overcome it by employing a sufficiently long probe equipped with an aspiration apparatus transporting the sample from the ground to the detector-equipped UAV. Full article

(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)

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17 pages, 4938 KiB

Open AccessArticle

Monitoring Corrosion Processes via Visible Fiber-Optic Evanescent Wave Sensor

by Dervis Türkmen, Achim Krug and Boris Mizaikoff

Chemosensors 2020, 8(3), 76; https://doi.org/10.3390/chemosensors8030076 - 23 Aug 2020

Cited by 3 | Viewed by 3354

Abstract

Ferrous objects, especially those that are additionally exposed to harsh environments, e.g., high humidity, have the common problem of suffering aggressive corrosion processes. Without a precaution, this leads in many cases to a limited functionality followed by treatment steps, and expensive repairing costs, [...] Read more.

Ferrous objects, especially those that are additionally exposed to harsh environments, e.g., high humidity, have the common problem of suffering aggressive corrosion processes. Without a precaution, this leads in many cases to a limited functionality followed by treatment steps, and expensive repairing costs, as well as to defects/uselessness and even to safety problems, e.g., bridge-collapsing, escaping gas and liquids from pipelines, or leaking oil tankers destroying the ecological system. Conventionally applied methods are confined to laboratory use due to bulky instruments, and are, therefore, time-intensive and may cause erroneous results. Therefore, a sensor based on fiber-optic evanescent wave spectroscopy (FEWS) working in the visible spectral range was developed. The sensor system is comprised of an uncoated single crystal sapphire fiber as a waveguide operating in the visible spectral range in combination with a laser diode as a light source at a specific wavelength and a photodiode for signal detection. Within this study, the potential of the developed sensor was investigated. The corrosion process was simulated by implementing a corroded iron bar inside the measuring cell. When corrosion starts, iron ions are released leading to a complexation reaction with the dye. The results showed the potential use of the developed sensor system enabling implementation for online and on-site detection and monitoring of components susceptible to corrosion. Full article

(This article belongs to the Special Issue Feature Papers – Chemical Sensors for Industrial Applications, Environmental, and Food Monitoring)

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17 pages, 4809 KiB

Open AccessArticle

Determination of Volatile Organic Compounds in Water by Attenuated Total Reflection Infrared Spectroscopy and Diamond-Like Carbon Coated Silicon Wafers

by Carina Dettenrieder, Dervis Türkmen, Andreas Mattsson, Lars Österlund, Mikael Karlsson and Boris Mizaikoff

Chemosensors 2020, 8(3), 75; https://doi.org/10.3390/chemosensors8030075 - 23 Aug 2020

Cited by 11 | Viewed by 4769

Abstract

Volatile organic compounds (VOCs) are one of the most commonly detected contaminants in water. The occurrence is mainly in gasoline and other petroleum-based products, fumigants, paints and plastics. Releases into the environment and the widespread use have an impact on the ecosystem such [...] Read more.

Volatile organic compounds (VOCs) are one of the most commonly detected contaminants in water. The occurrence is mainly in gasoline and other petroleum-based products, fumigants, paints and plastics. Releases into the environment and the widespread use have an impact on the ecosystem such as humans and animals due to their toxicity, mutagenicity, and carcinogenicity. VOCs may persist in groundwater and may enter drinking water supplies. In this paper, a diamond-like carbon (DLC)-coated silicon waveguide in combination with a polymer film (ethylene/propylene copolymer, E/P-co) for enrichment of analytes was investigated to determine its suitability for ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopic detection of VOCs. The DLC film was fluorine-terminated enhancing the adhesion of the hydrophobic polymer to the waveguide surface. The analytes diffuse into the hydrophobic polymer whereas water is excluded from the emanating evanescent field. Therefore, direct detection in aqueous systems is enabled. Nine VOCs, i.e., ethylbenzene (EB), trichloroethylene (TCE), tetrachloroethylene (TeCE), the xylene isomers (p-xylene, pXYL; m-xylene, mXYL; o-xylene, oXYL), naphthalene (NAPH), toluene (TOL), and benzene (BENZ), were evaluated simultaneously qualitatively and quantitatively showing the potential of DLC coatings revealing high sensitivities in the low ppb to ppm concentration range, i.e., 50 ppb for TeCE. To the best of our knowledge, this is the first time of IR spectroscopic detection of VOCs in aqueous solutions using DLC-coated waveguides in combination with a hydrophobic polymer. By utilizing a DLC-coated waveguide, a versatile sensor for real-time monitoring in harsh environments such as effluents, leaking pipelines, and underground storage tanks is feasible due to response times within a few minutes. Full article

(This article belongs to the Special Issue Feature Papers – Chemical Sensors for Industrial Applications, Environmental, and Food Monitoring)

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23 pages, 1078 KiB

Open AccessReview

Electrochemical Methods and (Bio) Sensors for Rosmarinic Acid Investigation

by Iulia Gabriela David, Dana Elena Popa, Mihaela Buleandră and Mihaela Carmen Cheregi

Chemosensors 2020, 8(3), 74; https://doi.org/10.3390/chemosensors8030074 - 22 Aug 2020

Cited by 15 | Viewed by 4050

Abstract

Rosmarinic acid (RA) is an important bioactive phenolic acid with significant biochemical activities, including the antioxidant one. It is widely found in plants of the families Lamiaceae and Boraginaceae and has many uses in the food, pharmaceutical and cosmetics industries. RA is an [...] Read more.

Rosmarinic acid (RA) is an important bioactive phenolic acid with significant biochemical activities, including the antioxidant one. It is widely found in plants of the families Lamiaceae and Boraginaceae and has many uses in the food, pharmaceutical and cosmetics industries. RA is an electroactive species owing to the presence of the two catechol groups in its structure. Due to their inherent characteristics, such as sensitivity, selectivity, ease of operation and not too high costs, electrochemical methods of analysis are interesting tools for the assessment of redox-active compounds. Moreover, there is a good correlation between the redox potential of the analyte and its capability to donate electrons and, consequently, its antioxidant activity. Therefore, this paper presents a detailed overview of the electrochemical (bio)sensors and methods, in both stationary and dynamic systems, applied for RA investigation under different aspects. These comprise its antioxidant activity, its interaction with biological important molecules and the quantification of RA or total polyphenolic content in different samples. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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14 pages, 2661 KiB

Open AccessArticle

Robust and Rapid Detection of Mixed Volatile Organic Compounds in Flow Through Air by a Low Cost Electronic Nose

by Jiamei Huang and Jayne Wu

Chemosensors 2020, 8(3), 73; https://doi.org/10.3390/chemosensors8030073 - 21 Aug 2020

Cited by 26 | Viewed by 4207

Abstract

This work aims to detect volatile organic compounds (VOC), i.e., acetone, ethanol and isopropyl alcohol (IPA) and their binary and ternary mixtures in a simulated indoor ventilation system. Four metal-oxide-semiconductor (MOS) gas sensors were chosen to form an electronic nose and it was [...] Read more.

This work aims to detect volatile organic compounds (VOC), i.e., acetone, ethanol and isopropyl alcohol (IPA) and their binary and ternary mixtures in a simulated indoor ventilation system. Four metal-oxide-semiconductor (MOS) gas sensors were chosen to form an electronic nose and it was used in a flow-through system. To speed up the detection process, transient signals were used to extracted features, as opposed to commonly used steady-state signals, which would require long time stabilization of testing parameters. Five parameters were extracted including three in phase space and two in time space. Classifier and regression models based on backpropagation neural network (BPNN) were used for the qualitative and quantitative detection of VOC mixtures. The VOCs were mixed at different ratios; ethanol and isopropyl alcohol had similar physical and chemical properties, both being challenging in terms of obtaining quantitative results. To estimate the amounts of VOC in the mixtures, the Levenberg–Marquardt algorithm was chosen in network training. When compared with the multivariate linear regression method, the BPNN-based model offered better performance on differentiating ethanol and IPA. The test accuracy of the classification was 82.6%. The concept used in this work could be readily translated for detecting closely related chemicals. Full article

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14 pages, 2842 KiB

Open AccessArticle

Enhanced NO₂-Sensing Properties of Au-Loaded Porous In₂O₃ Gas Sensors at Low Operating Temperatures

by Taro Ueda, Inci Boehme, Takeo Hyodo, Yasuhiro Shimizu, Udo Weimar and Nicolae Barsan

Chemosensors 2020, 8(3), 72; https://doi.org/10.3390/chemosensors8030072 - 20 Aug 2020

Cited by 27 | Viewed by 3823

Abstract

NO₂-sensing properties of semiconductor gas sensors using porous In₂O₃ powders loaded with and without 0.5 wt% Au (Au/In₂O₃ and In₂O₃ sensors, respectively) were examined in wet air (70% relative humidity at 25 [...] Read more.

NO₂-sensing properties of semiconductor gas sensors using porous In₂O₃ powders loaded with and without 0.5 wt% Au (Au/In₂O₃ and In₂O₃ sensors, respectively) were examined in wet air (70% relative humidity at 25 °C). In addition, the effects of Au loading on the increased NO₂ response were discussed on the basis of NO₂ adsorption/desorption properties on the oxide surface. The NO₂ response of the Au/In₂O₃ sensor monotonically increased with a decrease in the operating temperature, and the Au/In₂O₃ sensor showed higher NO₂ responses than those of the In₂O₃ sensor at a temperature of 100 °C or lower. In addition, the response time of the Au/In₂O₃ sensor was much shorter than that of the In₂O₃ sensor at 30 °C. The analysis based on the Freundlich adsorption mechanism suggested that the Au loading increased the adsorption strength of NO₂ on the In₂O₃ surface. Moreover, the Au loading was also quite effective in decreasing the baseline resistance of the In₂O₃ sensor in wet air (i.e., increasing the number of free electrons in the In₂O₃), which resulted in an increase in the number of negatively charged NO₂ species on the In₂O₃ surface. The Au/In₂O₃ sensor showed high response to the low concentration of NO₂ (ratio of resistance in target gas to that in air: ca. 133 to 0.1 ppm) and excellent NO₂ selectivity against CO and ethanol, especially at 100 °C. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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25 pages, 6725 KiB

Open AccessReview

Applying Nanomaterials to Modern Biomedical Electrochemical Detection of Metabolites, Electrolytes, and Pathogens

by Itthipon Jeerapan, Thitaporn Sonsa-ard and Duangjai Nacapricha

Chemosensors 2020, 8(3), 71; https://doi.org/10.3390/chemosensors8030071 - 19 Aug 2020

Cited by 20 | Viewed by 5792

Abstract

Personal biosensors and bioelectronics have been demonstrated for use in out-of-clinic biomedical devices. Such modern devices have the potential to transform traditional clinical analysis into a new approach, allowing patients or users to screen their own health or warning of diseases. Researchers aim [...] Read more.

Personal biosensors and bioelectronics have been demonstrated for use in out-of-clinic biomedical devices. Such modern devices have the potential to transform traditional clinical analysis into a new approach, allowing patients or users to screen their own health or warning of diseases. Researchers aim to explore the opportunities of easy-to-wear and easy-to-carry sensors that would empower users to detect biomarkers, electrolytes, or pathogens at home in a rapid and easy way. This mobility would open the door for early diagnosis and personalized healthcare management to a wide audience. In this review, we focus on the recent progress made in modern electrochemical sensors, which holds promising potential to support point-of-care technologies. Key original research articles covered in this review are mainly experimental reports published from 2018 to 2020. Strategies for the detection of metabolites, ions, and viruses are updated in this article. The relevant challenges and opportunities of applying nanomaterials to support the fabrication of new electrochemical biosensors are also discussed. Finally, perspectives regarding potential benefits and current challenges of the technology are included. The growing area of personal biosensors is expected to push their application closer to a new phase of biomedical advancement. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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14 pages, 4339 KiB

Open AccessArticle

A Simple but Efficient Voltammetric Sensor for Simultaneous Detection of Tartrazine and Ponceau 4R Based on TiO₂/Electro-Reduced Graphene Oxide Nanocomposite

by Zirong Qin, Jinyan Zhang, Ying Liu, Jingtao Wu, Guangli Li, Jun Liu and Quanguo He

Chemosensors 2020, 8(3), 70; https://doi.org/10.3390/chemosensors8030070 - 19 Aug 2020

Cited by 32 | Viewed by 3664

Abstract

In this work, we report a simple but efficient voltammetric sensor for simultaneous detection of ponceau 4R and tartrazine based on TiO₂/electro-reduced graphene oxide nanocomposites (TiO₂/ErGO). TiO₂/ErGO nanocomposites were prepared by ultrasonically dispersing TiO₂ nanoparticles (TiO [...] Read more.

In this work, we report a simple but efficient voltammetric sensor for simultaneous detection of ponceau 4R and tartrazine based on TiO₂/electro-reduced graphene oxide nanocomposites (TiO₂/ErGO). TiO₂/ErGO nanocomposites were prepared by ultrasonically dispersing TiO₂ nanoparticles (TiO₂ NPs) into graphene oxide (GO) solution followed by a green in-situ electrochemical reduction. TiO₂ NPs were uniformly supported on ErGO nanoflakes, which provides a favorable interface for the adsorption and subsequent oxidation of target analytes. TiO₂/ErGO showed remarkable electrocatalytic capacity for the oxidation of ponceau 4R and tartrazine, with minimized oxidation overpotentials and boosted adsorptive striping differential pulse voltammetric (AdSDPV) response peak currents. Under the optimal experimental conditions, the anodic peak currents of ponceau 4R and tartrazine increase linearly with the respective natural logarithm of concentrations from 0.01 to 5.0 μM. The detection limits (LOD = 3σ/s) for ponceau 4R and tartrazine are 4.0 and 6.0 nM, respectively. The extraordinary analytical properties of TiO₂/ErGO/GCE are primarily attributed to the synergistic enhancement effect from ErGO nanoflakes and TiO₂ NPs. Moreover, the proposed TiO₂/ErGO/GCE achieves reliable determination of ponceau 4R and tartrazine in orange juice with excellent selectively, reproducibility and stability. Together with simplicity, rapidness, and low cost, the proposed sensor demonstrates great potential for on-site detection of azo colorants. Full article

(This article belongs to the Special Issue Voltammperometric Sensors)

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9 pages, 216 KiB

Open AccessCommentary

Exposure Science in the 21st Century: Advancing the Science and Technology of Environmental Sensors through Cooperation and Collaboration across U.S. Federal Agencies

by Janis Hulla, Vasu Kilaru, Gregory Doucette, David Balshaw and Tim Watkins

Chemosensors 2020, 8(3), 69; https://doi.org/10.3390/chemosensors8030069 - 13 Aug 2020

Viewed by 2444

Abstract

The convergence of technological innovations in areas such as microelectronics, fabrication, the Internet-of-things (IoT), and smartphones, along with their associated “apps”, permeates many aspects of life. To that list we now can add environmental monitoring. Once the sole purview of governments and academics [...] Read more.

The convergence of technological innovations in areas such as microelectronics, fabrication, the Internet-of-things (IoT), and smartphones, along with their associated “apps”, permeates many aspects of life. To that list we now can add environmental monitoring. Once the sole purview of governments and academics in research, this sector is currently experiencing a transformation that is democratizing monitoring with inexpensive, portable commodities available through online retailers. However, as with any emerging area, several challenges and infrastructural hurdles must be addressed before this technology can be fully adopted and its potential be realized. A unique aspect of environmental sensing that differentiates it from some other technology sectors is its strong intersection and overlap with governance, public policy, public health, and national security—all of which contain some element of inherent governmental function. This paper advocates for and addresses the role of sensors in exposure science and illustrates areas in which improved coordination and leveraging of investments by government have helped and would catalyze further development of this technology sector. Full article

(This article belongs to the Section Applied Chemical Sensors)

8 pages, 1729 KiB

Open AccessCommunication

Nanometre-Scale Visualization of Chemical Parameter Changes by T₁-Weighted ODMR Imaging Using a Fluorescent Nanodiamond

by Takahiro Fujisaku, Ryuji Igarashi and Masahiro Shirakawa

Chemosensors 2020, 8(3), 68; https://doi.org/10.3390/chemosensors8030068 - 11 Aug 2020

Cited by 1 | Viewed by 4170

Abstract

The dynamics of physical parameters in cells is strongly related to life phenomena; thus, a method to monitor and visualize them on a single-organelle scale would be useful to reveal unknown biological processes. We demonstrate real-time nanometre-scale T₁-weighted imaging using a [...] Read more.

The dynamics of physical parameters in cells is strongly related to life phenomena; thus, a method to monitor and visualize them on a single-organelle scale would be useful to reveal unknown biological processes. We demonstrate real-time nanometre-scale T₁-weighted imaging using a fluorescent nanodiamond. We explored optically detected magnetic resonance (ODMR) contrast at various values of interval laser pulse (τ), showing that sufficient contrast is obtained by appropriate selection of τ. By this method, we visualized nanometre-scale pH changes using a functionalized nanodiamond whose T₁ has a dependence on pH conditions. Full article

(This article belongs to the Special Issue A Theme Issue in Honor of Dr. Richard Horobin—Cell or Organelle Selective Fluorescent Probes: Their Design, Mechanism, Modeling and Application)

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8 pages, 3363 KiB

Open AccessLetter

Sputtered SnO₂/ZnO Heterostructures for Improved NO₂ Gas Sensing Properties

by Bharat Sharma, Ashutosh Sharma, Monika Joshi and Jae-ha Myung

Chemosensors 2020, 8(3), 67; https://doi.org/10.3390/chemosensors8030067 - 7 Aug 2020

Cited by 40 | Viewed by 5609

Abstract

A highly sensitive and selective NO₂ gas sensor dependent on SnO₂/ZnO heterostructures was fabricated using a sputtering process. The SnO₂/ZnO heterostructure thin film samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray [...] Read more.

A highly sensitive and selective NO₂ gas sensor dependent on SnO₂/ZnO heterostructures was fabricated using a sputtering process. The SnO₂/ZnO heterostructure thin film samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Sensors fabricated with heterostructures attained higher gas response (S = 66.9) and quicker response-recovery (20 s, 45 s) characteristics at 100 °C operating temperature towards 100 ppm NO₂ gas efficiently in comparison to sensors based on their mono-counterparts. The selectivity and stability of SnO₂/ZnO heterostructures were studied. The more desirable sensing mechanism of SnO₂/ZnO heterostructures towards NO₂ was described in detail. Full article

(This article belongs to the Collection Sensing Materials: Advances in Synthesis, Functionalities, and Applications)

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30 pages, 2214 KiB

Open AccessReview

Anti-Biofouling Strategies for Long-Term Continuous Use of Implantable Biosensors

by Jian Xu and Hyowon Lee

Chemosensors 2020, 8(3), 66; https://doi.org/10.3390/chemosensors8030066 - 7 Aug 2020

Cited by 65 | Viewed by 9350

Abstract

The growing trend for personalized medicine calls for more reliable implantable biosensors that are capable of continuously monitoring target analytes for extended periods (i.e., >30 d). While promising biosensors for various applications are constantly being developed in the laboratories across the world, many [...] Read more.

The growing trend for personalized medicine calls for more reliable implantable biosensors that are capable of continuously monitoring target analytes for extended periods (i.e., >30 d). While promising biosensors for various applications are constantly being developed in the laboratories across the world, many struggle to maintain reliable functionality in complex in vivo environments over time. In this review, we explore the impact of various biotic and abiotic failure modes on the reliability of implantable biosensors. We discuss various design considerations for the development of chronically reliable implantable biosensors with a specific focus on strategies to combat biofouling, which is a fundamental challenge for many implantable devices. Briefly, we introduce the process of the foreign body response and compare the in vitro and the in vivo performances of state-of-the-art implantable biosensors. We then discuss the latest development in material science to minimize and delay biofouling including the usage of various hydrophilic, biomimetic, drug-eluting, zwitterionic, and other smart polymer materials. We also explore a number of active anti-biofouling approaches including stimuli-responsive materials and mechanical actuation. Finally, we conclude this topical review with a discussion on future research opportunities towards more reliable implantable biosensors. Full article

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14 pages, 4162 KiB

Open AccessArticle

Wicking in Paper Strips under Consideration of Liquid Absorption Capacity

by Surasak Kasetsirikul, Muhammad J. A. Shiddiky and Nam-Trung Nguyen

Chemosensors 2020, 8(3), 65; https://doi.org/10.3390/chemosensors8030065 - 6 Aug 2020

Cited by 7 | Viewed by 3964

Abstract

Paper-based microfluidic devices have the potential of being a low-cost platform for diagnostic devices. Electrical circuit analogy (ECA) model has been used to model the wicking process in paper-based microfluidic devices. However, material characteristics such as absorption capacity cannot be included in the [...] Read more.

Paper-based microfluidic devices have the potential of being a low-cost platform for diagnostic devices. Electrical circuit analogy (ECA) model has been used to model the wicking process in paper-based microfluidic devices. However, material characteristics such as absorption capacity cannot be included in the previous ECA models. This paper proposes a new model to describe the wicking process with liquid absorption in a paper strip. We observed that the fluid continues to flow in a paper strip, even after the fluid reservoir has been removed. This phenomenon is caused by the ability of the paper to store liquid in its matrix. The model presented in this paper is derived from the analogy to the current response of an electric circuit with a capacitance. All coefficients in the model are fitted with data of capillary rise experiments and compared with direct measurement of the absorption capacity. The theoretical data of the model agrees well with experimental data and the conventional Washburn model. Considering liquid absorption capacity as a capacitance helps to explain the relationship between material characteristics and the wicking mechanism. Full article

(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)

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11 pages, 2388 KiB

Open AccessEditor’s ChoiceArticle

Molecular Imprinted Based Quartz Crystal Microbalance Sensors for Bacteria and Spores

by Usman Latif, Serpil Can, Hermann F. Sussitz and Franz L. Dickert

Chemosensors 2020, 8(3), 64; https://doi.org/10.3390/chemosensors8030064 - 4 Aug 2020

Cited by 16 | Viewed by 3714

Abstract

A molecular imprinting strategy was combined with mass-sensitive transducers to generate robust and reliable biomimetic sensor systems for the detection of bioparticles. The patterning of polymers with bioanalytes enabled us to detect Escherichia coli (E. coli) bacteria with quartz crystal microbalance [...] Read more.

A molecular imprinting strategy was combined with mass-sensitive transducers to generate robust and reliable biomimetic sensor systems for the detection of bioparticles. The patterning of polymers with bioanalytes enabled us to detect Escherichia coli (E. coli) bacteria with quartz crystal microbalance (QCM). The QCM sensor results were compared with direct Atomic Force Microscopy (AFM) measurements—bacteria cells adhering to the sensor coatings were counted. The recognition sites generated by Bacillus subtilis (B. subtilis) spores could successfully and reversibly recognize the template analyte and ensured rapid sensing. Cross sensitive measurements clearly showed the advantage of the molecular imprinting strategy, by which spores of Bacillus species (subtilis and thuringiensis) could easily be differentiated and selectively detected. The growth of B. subtilis from its spores was observed at 42 °C in appropriate nutrient solution of glucose and ammonium sulfate over a period of 15 h. Moreover, the growth of B. subtilis bacteria from its respective spores was studied by increasing the glucose concentration until saturation effect of the sensor. The polymeric sensor coatings were patterned to fix the B. subtilis in order to investigate osmotic effects according to a frequency response of 400 Hz by altering the ionic strength of 0.1 M. Full article

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13 pages, 2442 KiB

Open AccessArticle

Electrochemical Detection of H₂O₂ Released from Prostate Cancer Cells Using Pt Nanoparticle-Decorated rGO–CNT Nanocomposite-Modified Screen-Printed Carbon Electrodes

by Seokyung Lee, Young Ju Lee, Jae Hyung Kim and Gi-Ja Lee

Chemosensors 2020, 8(3), 63; https://doi.org/10.3390/chemosensors8030063 - 4 Aug 2020

Cited by 27 | Viewed by 4745

Abstract

In this study, we fabricated platinum nanoparticles (PtNP)-decorated, porous reduced graphene oxide (rGO)–carbon nanotube (CNT) nanocomposites on a PtNP-deposited screen-printed carbon electrode (PtNP/rGO–CNT/PtNP/SPCE) for detection of hydrogen peroxide (H₂O₂), which is released from prostate cancer cells LNCaP. The PtNP/rGO–CNT/PtNP/SPCE [...] Read more.

In this study, we fabricated platinum nanoparticles (PtNP)-decorated, porous reduced graphene oxide (rGO)–carbon nanotube (CNT) nanocomposites on a PtNP-deposited screen-printed carbon electrode (PtNP/rGO–CNT/PtNP/SPCE) for detection of hydrogen peroxide (H₂O₂), which is released from prostate cancer cells LNCaP. The PtNP/rGO–CNT/PtNP/SPCE was fabricated by a simple electrochemical deposition and co-reduction method. In addition, the amperometric response of the PtNP/rGO–CNT/PtNP/SPCE electrode was evaluated through consecutive additions of H₂O₂ at an applied potential of 0.2 V (vs. Ag pseudo-reference electrode). As a result, the prepared PtNP/rGO–CNT/PtNP/SPCE showed good electrocatalytic activity toward H₂O₂ compared to bare SPCE, rGO–CNT/SPCE, PtNP/SPCE, and rGO–CNT/PtNP/SPCE. In addition, the PtNP/rGO–CNT/PtNP/SPCE electrode exhibited a sensitivity of 206 μA mM⁻¹·cm⁻² to H₂O₂ in a linear range of 25 to 1000 μM (R² = 0.99). Moreover, the PtNP/rGO–CNT/PtNP/SPCE electrode was less sensitive to common interfering substances, such as ascorbic acid, uric acid, and glucose than H₂O₂. Finally, real-time monitoring of H₂O₂ released from LNCaP cells was successfully performed by this electrode. Therefore, we expect that the PtNP/rGO–CNT/PtNP/SPCE can be utilized as a promising electrochemical sensor for practical nonenzymatic detection of H₂O₂ in live cells or clinical analysis. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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13 pages, 6135 KiB

Open AccessArticle

Study on Ultrasonic Assisted Electrochemical Drill-Grinding of Superalloy

by Huanghai Kong, Yong Liu, Xiangming Zhu and Tengfei Peng

Chemosensors 2020, 8(3), 62; https://doi.org/10.3390/chemosensors8030062 - 3 Aug 2020

Cited by 9 | Viewed by 3329

Abstract

Electrochemical grinding (ECG) technique composed of electrochemical machining (ECM) and mechanical grinding is a proper method for machining of difficult-to-cut alloys. This paper presents a new ultrasonic assisted electrochemical drill-grinding (UAECDG) technique which combines electrochemical drilling, mechanical grinding, and ultrasonic vibration to fabricating [...] Read more.

Electrochemical grinding (ECG) technique composed of electrochemical machining (ECM) and mechanical grinding is a proper method for machining of difficult-to-cut alloys. This paper presents a new ultrasonic assisted electrochemical drill-grinding (UAECDG) technique which combines electrochemical drilling, mechanical grinding, and ultrasonic vibration to fabricating high-quality small holes on superalloy. By applying ultrasonic vibration to high-speed rotating electrode in ECG, machining stability, efficiency, and surface quality can be obviously improved. Firstly, the electrochemical passive behavior of superalloy is studied, the mathematical model and simulation of gap electric field are established. Then, several experiments are conducted to investigate the influence of applied voltage, feed rate and ultrasonic amplitude on the machining quality. The balance of material removal between electrochemical reaction and mechanical grinding is achieved by optimizing the machining parameters. It reveals that the surface quality as well as machining stability and efficiency can be significantly improved by applying rotating ultrasonic vibration to the ECG process. Finally, several small holes of high quality have been machined successfully along with surface roughness of hole sidewall decreases from Ra 0.99 μm to Ra 0.14 μm by UAECDG. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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26 pages, 5791 KiB

Open AccessReview

Phage-Based Sensors in Medicine: A Review

by Sebastian J. Machera, Joanna Niedziółka-Jönsson and Katarzyna Szot-Karpińska

Chemosensors 2020, 8(3), 61; https://doi.org/10.3390/chemosensors8030061 - 31 Jul 2020

Cited by 17 | Viewed by 5735

Abstract

Bacteriophages are interesting entities on the border of biology and chemistry. In nature, they are bacteria parasites, while, after genetic manipulation, they gain new properties, e.g., selectively binding proteins. Owing to this, they may be applied as recognition elements in biosensors. Combining bacteriophages [...] Read more.

Bacteriophages are interesting entities on the border of biology and chemistry. In nature, they are bacteria parasites, while, after genetic manipulation, they gain new properties, e.g., selectively binding proteins. Owing to this, they may be applied as recognition elements in biosensors. Combining bacteriophages with different transducers can then result in the development of innovative sensor designs that may revolutionize bioanalytics and improve the quality of medical services. Therefore, here, we review the use of bacteriophages, or peptides from bacteriophages, as new sensing elements for the recognition of biomarkers and the construction of the highly effective diagnostics tools. Full article

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14 pages, 2882 KiB

Open AccessArticle

Opto-Electronic Nose Coupled to a Silicon Micro Pre-Concentrator Device for Selective Sensing of Flavored Waters

by Sami Slimani, Etienne Bultel, Thomas Cubizolle, Cyril Herrier, Tristan Rousselle and Thierry Livache

Chemosensors 2020, 8(3), 60; https://doi.org/10.3390/chemosensors8030060 - 31 Jul 2020

Cited by 25 | Viewed by 4092

Abstract

Headspace analysis of highly humid samples remains a challenge for artificial olfaction. Based on surface plasmon resonance imaging and bio-based sensors, the NeOse Pro olfactive analyzer yields multivariate data and enhances the statistical discrimination capacity of odor patterns. However, the presence of a [...] Read more.

Headspace analysis of highly humid samples remains a challenge for artificial olfaction. Based on surface plasmon resonance imaging and bio-based sensors, the NeOse Pro olfactive analyzer yields multivariate data and enhances the statistical discrimination capacity of odor patterns. However, the presence of a high background signal, such as water vapor from aqueous samples, may deteriorate its discriminant ability. Recently, miniaturized pre-concentrators packed with hydrophobic adsorbent have been developed to improve the detection limit of gas analysis methods and to enhance their selectivity by reducing the water’s background signal. This work presents, for the first time, the coupling of a miniaturized silicon micro pre-concentration unit (µPC) to a bio-based opto-electronic nose (NeOse Pro). The results showed that the coupling of a silicon µPC with the NeOse Pro led to an improvement in the detection limit of n-nonane by at least a factor of 125. Additionally, principal component analysis (PCA) of eight different flavored waters showed an enhanced discrimination ability of the coupled set-up in highly humid conditions. Full article

(This article belongs to the Special Issue Chemosensors and Biosensors for Food Quality and Safety)

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19 pages, 1409 KiB

Open AccessReview

Electrochemical Sensors Coupled with Multivariate Statistical Analysis as Screening Tools for Wine Authentication Issues: A Review

by Elisabeta-Irina Geană, Corina Teodora Ciucure and Constantin Apetrei

Chemosensors 2020, 8(3), 59; https://doi.org/10.3390/chemosensors8030059 - 30 Jul 2020

Cited by 28 | Viewed by 4475

Abstract

Consumers are increasingly interested in the characteristics of the products they consume, including aroma, taste, and appearance, and hence, scientific research was conducted in order to develop electronic senses devices that mimic the human senses. Thanks to the utilization of electroanalytical techniques that [...] Read more.

Consumers are increasingly interested in the characteristics of the products they consume, including aroma, taste, and appearance, and hence, scientific research was conducted in order to develop electronic senses devices that mimic the human senses. Thanks to the utilization of electroanalytical techniques that used various sensors modified with different electroactive materials coupled with pattern recognition methods, artificial senses such as electronic tongues (ETs) are widely applied in food analysis for quality and authenticity approaches. This paper summarizes the applications of electrochemical sensors (voltammetric, amperometric, and potentiometric) coupled with unsupervised and supervised pattern recognition methods (principal components analysis (PCA), linear discriminant analysis (LDA), partial least square (PLS) regression, artificial neural network (ANN)) for wine authenticity assessments including the discrimination of varietal and geographical origins, monitoring the ageing processes, vintage year discrimination, and detection of frauds and adulterations. Different wine electrochemical authentication methodologies covering the electrochemical techniques, electrodes types, functionalization sensitive materials and multivariate statistical analysis are emphasized and the main advantages and disadvantages of using the proposed methodologies for real applications were concluded. Full article

(This article belongs to the Special Issue Voltammperometric Sensors)

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13 pages, 3659 KiB

Open AccessArticle

Electrochemical Sodium Ion Sensor Based on Silver Nanoparticles/Graphene Oxide Nanocomposite for Food Application

by Pranlekha Traiwatcharanon, Wilai Siriwatcharapiboon and Chatchawal Wongchoosuk

Chemosensors 2020, 8(3), 58; https://doi.org/10.3390/chemosensors8030058 - 28 Jul 2020

Cited by 32 | Viewed by 6120

Abstract

High sodium ion (Na⁺) consumption leads to high blood pressure which causes many health issues. Real-time determination of Na⁺ content in food is still important to limit Na⁺ intake and control the taste of food. In this work, we [...] Read more.

High sodium ion (Na⁺) consumption leads to high blood pressure which causes many health issues. Real-time determination of Na⁺ content in food is still important to limit Na⁺ intake and control the taste of food. In this work, we have developed an electrochemical sensor based on agglomeration of silver nanoparticles (AgNPs) and graphene oxide (GO) modified on a screen-printed silver electrode (SPE) for Na⁺ detection at room temperature by using cyclic voltammetry (CV). The AgNPs were synthesized through a simple green route using Pistia stratiotes extract as a reducing agent under blue light illumination and mixed with the GO to be a Na⁺ selective sensing nanocomposite. The AgNPs/GO/SPE sensor showed high sensitivity (0.269 mA/mM/cm²), high selectivity, linear relationship (0–100 mM), good stability, and excellent reproducibility to Na⁺ detection as well as low limit of detection (9.344 mM) for food application. The interfering species such as K⁺, Zn²⁺, Na⁺, Mg²⁺, glucose, and ascorbic acid did not have any influence on the Na⁺ determination. The AgNPs/GO/SPE sensor was successfully applied to determine Na⁺ in real samples such as fish sauce and seasoning powder of instant noodle. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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