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9 pages, 3325 KiB

Open AccessArticle

Estimation of Potential Distribution during Crevice Corrosion through Analysis of I–V Curves Obtained by LAPS

by Kiyomi Nose, Ko-ichiro Miyamoto and Tatsuo Yoshinobu

Sensors 2020, 20(10), 2873; https://doi.org/10.3390/s20102873 - 19 May 2020

Cited by 5 | Viewed by 2887

Abstract

Crevice corrosion is a type of local corrosion which occurs when a metal surface is confined in a narrow gap on the order of 10 μm filled with a solution. Because of the inaccessible geometry, experimental methods to analyze the inner space of [...] Read more.

Crevice corrosion is a type of local corrosion which occurs when a metal surface is confined in a narrow gap on the order of 10 μm filled with a solution. Because of the inaccessible geometry, experimental methods to analyze the inner space of the crevice have been limited. In this study, a light-addressable potentiometric sensor (LAPS) was employed to estimate the potential distribution inside the crevice owing to the IR drop by the anodic current flowing out of the structure. Before crevice corrosion, the I–V curve of the LAPS showed a potential shift, depending on the distance from the perimeter. The shift reflected the potential distribution due to the IR drop by the anodic current flowing out of the crevice. After crevice corrosion, the corrosion current increased exponentially, and a local pH change was detected where the corrosion was initiated. A simple model of the IR drop was used to calculate the crevice gap, which was 12 μm—a value close to the previously reported values. Thus, the simultaneous measurement of the I–V curves obtained using a LAPS during potentiostatic electrolysis could be applied as a new method for estimating the potential distribution in the crevice. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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9 pages, 1505 KiB

Open AccessArticle

Label-Free Detection of E. coli O157:H7 DNA Using Light-Addressable Potentiometric Sensors with Highly Oriented ZnO Nanorod Arrays

by Yulan Tian, Tao Liang, Ping Zhu, Yating Chen, Wei Chen, Liping Du, Chunsheng Wu and Ping Wang

Sensors 2019, 19(24), 5473; https://doi.org/10.3390/s19245473 - 12 Dec 2019

Cited by 20 | Viewed by 3144

Abstract

The detection of bacterial deoxyribonucleic acid (DNA) is of great significance in the quality control of food and water. In this study, a light-addressable potentiometric sensor (LAPS) deposited with highly oriented ZnO nanorod arrays (NRAs) was used for the label-free detection of single-stranded [...] Read more.

The detection of bacterial deoxyribonucleic acid (DNA) is of great significance in the quality control of food and water. In this study, a light-addressable potentiometric sensor (LAPS) deposited with highly oriented ZnO nanorod arrays (NRAs) was used for the label-free detection of single-stranded bacterial DNA (ssDNA). A functional, sensitive surface for the detection of Escherichia coli (E. coli) O157:H7 DNA was prepared by the covalent immobilization of the specific probe single-stranded DNA (ssDNA) on the LAPS surface. The functional surface was exposed to solutions containing the target E. coli ssDNA molecules, which allowed for the hybridization of the target ssDNA with the probe ssDNA. The surface charge changes induced by the hybridization of the probe ssDNA with the target E. coli ssDNA were monitored using LAPS measurements in a label-free manner. The results indicate that distinct signal changes can be registered and recorded to detect the target E. coli ssDNA. The lower detection limit of the target ssDNA corresponded to 1.0 × 10² colony forming units (CFUs)/mL of E. coli O157:H7 cells. All the results demonstrate that this DNA biosensor, based on the electrostatic detection of ssDNA, provides a novel approach for the sensitive and effective detection of bacterial DNA, which has promising prospects and potential applications in the quality control of food and water. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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14 pages, 2263 KiB

Open AccessArticle

A LAPS-Based Differential Sensor for Parallelized Metabolism Monitoring of Various Bacteria

by Shahriar Dantism, Désirée Röhlen, Torsten Wagner, Patrick Wagner and Michael J. Schöning

Sensors 2019, 19(21), 4692; https://doi.org/10.3390/s19214692 - 29 Oct 2019

Cited by 14 | Viewed by 3686

Abstract

Monitoring the cellular metabolism of bacteria in (bio)fermentation processes is crucial to control and steer them, and to prevent undesired disturbances linked to metabolically inactive microorganisms. In this context, cell-based biosensors can play an important role to improve the quality and increase the [...] Read more.

Monitoring the cellular metabolism of bacteria in (bio)fermentation processes is crucial to control and steer them, and to prevent undesired disturbances linked to metabolically inactive microorganisms. In this context, cell-based biosensors can play an important role to improve the quality and increase the yield of such processes. This work describes the simultaneous analysis of the metabolic behavior of three different types of bacteria by means of a differential light-addressable potentiometric sensor (LAPS) set-up. The study includes Lactobacillus brevis, Corynebacterium glutamicum, and Escherichia coli, which are often applied in fermentation processes in bioreactors. Differential measurements were carried out to compensate undesirable influences such as sensor signal drift, and pH value variation during the measurements. Furthermore, calibration curves of the cellular metabolism were established as a function of the glucose concentration or cell number variation with all three model microorganisms. In this context, simultaneous (bio)sensing with the multi-organism LAPS-based set-up can open new possibilities for a cost-effective, rapid detection of the extracellular acidification of bacteria on a single sensor chip. It can be applied to evaluate the metabolic response of bacteria populations in a (bio)fermentation process, for instance, in the biogas fermentation process. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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12 pages, 2759 KiB

Open AccessArticle

Modeling of the Return Current in a Light-Addressable Potentiometric Sensor

by Tatsuo Yoshinobu, Daisuke Sato, Yuanyuan Guo, Carl Frederik Werner and Ko-ichiro Miyamoto

Sensors 2019, 19(20), 4566; https://doi.org/10.3390/s19204566 - 21 Oct 2019

Cited by 3 | Viewed by 3165

Abstract

A light-addressable potentiometric sensor (LAPS) is a chemical sensor with a field-effect structure based on semiconductor. Its response to the analyte concentration is read out in the form of a photocurrent generated by illuminating the semiconductor with a modulated light beam. As stated [...] Read more.

A light-addressable potentiometric sensor (LAPS) is a chemical sensor with a field-effect structure based on semiconductor. Its response to the analyte concentration is read out in the form of a photocurrent generated by illuminating the semiconductor with a modulated light beam. As stated in its name, a LAPS is capable of spatially resolved measurement using a scanning light beam. Recently, it has been pointed out that a part of the signal current is lost by the return current due to capacitive coupling between the solution and the semiconductor, which may seriously affect the sensor performance such as the signal-to-noise ratio, the spatial resolution, and the sensitivity. In this study, a circuit model for the return current is proposed to study its dependence on various parameters such as the diameter of contact area, the modulation frequency, the specific conductivity of the solution, and the series resistance of the circuit. It is suggested that minimization of the series resistance of the circuit is of utmost importance in order to avoid the influence of the return current. The results of calculation based on this model are compared with experimental results, and its applicability and limitation are discussed. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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10 pages, 4126 KiB

Open AccessArticle

InGaN as a Substrate for AC Photoelectrochemical Imaging

by Bo Zhou, Anirban Das, Menno J. Kappers, Rachel A. Oliver, Colin J. Humphreys and Steffi Krause

Sensors 2019, 19(20), 4386; https://doi.org/10.3390/s19204386 - 11 Oct 2019

Cited by 19 | Viewed by 4121

Abstract

AC photoelectrochemical imaging at electrolyte–semiconductor interfaces provides spatially resolved information such as surface potentials, ion concentrations and electrical impedance. In this work, thin films of InGaN/GaN were used successfully for AC photoelectrochemical imaging, and experimentally shown to generate a considerable photocurrent under illumination [...] Read more.

AC photoelectrochemical imaging at electrolyte–semiconductor interfaces provides spatially resolved information such as surface potentials, ion concentrations and electrical impedance. In this work, thin films of InGaN/GaN were used successfully for AC photoelectrochemical imaging, and experimentally shown to generate a considerable photocurrent under illumination with a 405 nm modulated diode laser at comparatively high frequencies and low applied DC potentials, making this a promising substrate for bioimaging applications. Linear sweep voltammetry showed negligible dark currents. The imaging capabilities of the sensor substrate were demonstrated with a model system and showed a lateral resolution of 7 microns. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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10 pages, 3297 KiB

Open AccessArticle

CCD Multi-Ion Image Sensor with Four 128 × 128 Pixels Array

by Toshiaki Hattori, Fumihiro Dasai, Hikaru Sato, Ryo Kato and Kazuaki Sawada

Sensors 2019, 19(7), 1582; https://doi.org/10.3390/s19071582 - 1 Apr 2019

Cited by 5 | Viewed by 4189

Abstract

A semiconductor array pH image sensor consisting of four separated blocks was fabricated using charged coupled device (CCD) and complementary metal oxide semiconductor (CMOS) technologies. The sensing surface of one of the four blocks was Si₃N₄ and this block responded [...] Read more.

A semiconductor array pH image sensor consisting of four separated blocks was fabricated using charged coupled device (CCD) and complementary metal oxide semiconductor (CMOS) technologies. The sensing surface of one of the four blocks was Si₃N₄ and this block responded to H⁺. The surfaces of the other three blocks were respectively covered with cation sensitive membranes, which were separately printed with plasticized poly (vinyl chloride) solutions including Na⁺, K⁺, and Ca²⁺ ionophores by using an ink-jet printing method. In addition, each block of the image sensor with 128 × 128 pixels could have a calibration curve generated in each independent measurement condition. The present sensor could measure the concentration image of four kinds of ions (H⁺, K⁺, Na ⁺, Ca²⁺) simultaneously at 8.3 frames per second (fps) in separated regions on a chip. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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Review

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22 pages, 27938 KiB

Open AccessReview

Light-addressable Electrodes for Dynamic and Flexible Addressing of Biological Systems and Electrochemical Reactions

by Rene Welden, Michael J. Schöning, Patrick H. Wagner and Torsten Wagner

Sensors 2020, 20(6), 1680; https://doi.org/10.3390/s20061680 - 17 Mar 2020

Cited by 9 | Viewed by 4164

Abstract

In this review article, we are going to present an overview on possible applications of light-addressable electrodes (LAE) as actuator/manipulation devices besides classical electrode structures. For LAEs, the electrode material consists of a semiconductor. Illumination with a light source with the appropiate wavelength [...] Read more.

In this review article, we are going to present an overview on possible applications of light-addressable electrodes (LAE) as actuator/manipulation devices besides classical electrode structures. For LAEs, the electrode material consists of a semiconductor. Illumination with a light source with the appropiate wavelength leads to the generation of electron-hole pairs which can be utilized for further photoelectrochemical reaction. Due to recent progress in light-projection technologies, highly dynamic and flexible illumination patterns can be generated, opening new possibilities for light-addressable electrodes. A short introduction on semiconductor–electrolyte interfaces with light stimulation is given together with electrode-design approaches. Towards applications, the stimulation of cells with different electrode materials and fabrication designs is explained, followed by analyte-manipulation strategies and spatially resolved photoelectrochemical deposition of different material types. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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22 pages, 3555 KiB

Open AccessReview

Recent Developments of High-Resolution Chemical Imaging Systems Based on Light-Addressable Potentiometric Sensors (LAPSs)

by Tao Liang, Yong Qiu, Ying Gan, Jiadi Sun, Shuqi Zhou, Hao Wan and Ping Wang

Sensors 2019, 19(19), 4294; https://doi.org/10.3390/s19194294 - 3 Oct 2019

Cited by 20 | Viewed by 4399

Abstract

A light-addressable potentiometric sensor (LAPS) is a semiconductor electrochemical sensor based on the field-effect which detects the variation of the Nernst potential on the sensor surface, and the measurement area is defined by illumination. Thanks to its light-addressability feature, an LAPS-based chemical imaging [...] Read more.

A light-addressable potentiometric sensor (LAPS) is a semiconductor electrochemical sensor based on the field-effect which detects the variation of the Nernst potential on the sensor surface, and the measurement area is defined by illumination. Thanks to its light-addressability feature, an LAPS-based chemical imaging sensor system can be developed, which can visualize the two-dimensional distribution of chemical species on the sensor surface. This sensor system has been used for the analysis of reactions and diffusions in various biochemical samples. In this review, the LAPS system set-up, including the sensor construction, sensing and substrate materials, modulated light and various measurement modes of the sensor systems are described. The recently developed technologies and the affecting factors, especially regarding the spatial resolution and temporal resolution are discussed and summarized, and the advantages and limitations of these technologies are illustrated. Finally, the further applications of LAPS-based chemical imaging sensors are discussed, where the combination with microfluidic devices is promising. Full article

(This article belongs to the Special Issue Light-Addressing and Chemical Imaging Technologies for Electrochemical Sensing)

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