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Chemosensors, Volume 5, Issue 2 (June 2017)

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Editorial

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Open AccessEditorial Electrochemical Immunosensors and Aptasensors
Chemosensors 2017, 5(2), 13; doi:10.3390/chemosensors5020013
Received: 30 March 2017 / Revised: 30 March 2017 / Accepted: 30 March 2017 / Published: 2 April 2017
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Abstract
Since the first electrochemical biosensor for glucose detection, pioneered in 1962 by Clark and Lyons [1], research and application in the field has grown at an impressive rate and we are still witnessing a continuing evolution of research on this topic [2].[...] Full article
(This article belongs to the Special Issue Electrochemical Immunosensors and Aptasensors) Printed Edition available

Research

Jump to: Editorial, Review

Open AccessArticle A Chemically-Bound Glutathione Sensor Bioinspired by the Defense of Organisms against Heavy Metal Contamination: Optimization of the Immobilization Conditions
Chemosensors 2017, 5(2), 12; doi:10.3390/chemosensors5020012
Received: 23 February 2017 / Revised: 23 March 2017 / Accepted: 25 March 2017 / Published: 2 April 2017
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Abstract
The influence of the experimental conditions (glutathione concentration and incubation time and temperature) concerning the covalent immobilization of glutathione via carbodiimide coupling on the behavior of a glutathione modified screen-printed carbon electrode obtained by electrografting is evaluated. The optimized parameters fasten the modification
[...] Read more.
The influence of the experimental conditions (glutathione concentration and incubation time and temperature) concerning the covalent immobilization of glutathione via carbodiimide coupling on the behavior of a glutathione modified screen-printed carbon electrode obtained by electrografting is evaluated. The optimized parameters fasten the modification process and improve the performance of the sensor as compared to the usual procedure. This suggests the convenience of a tailored preparation of metal sensors based on metal-binding biomolecules such as glutathione. Full article
(This article belongs to the Special Issue Bioinspired Chemical Sensing)
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Open AccessArticle Microfluidic Electronic Tongue Applied to Soil Analysis
Chemosensors 2017, 5(2), 14; doi:10.3390/chemosensors5020014
Received: 24 February 2017 / Revised: 21 April 2017 / Accepted: 25 April 2017 / Published: 27 April 2017
Cited by 1 | PDF Full-text (3442 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Precision agriculture is crucial for increasing food output without expanding the cultivable area, which requires sensors to be deployed for controlling the level of nutrients in the soil. In this paper, we report on a microfluidic electronic tongue (e-tongue) based on impedance measurements
[...] Read more.
Precision agriculture is crucial for increasing food output without expanding the cultivable area, which requires sensors to be deployed for controlling the level of nutrients in the soil. In this paper, we report on a microfluidic electronic tongue (e-tongue) based on impedance measurements which is capable of distinguishing soil samples enriched with plant macronutrients. The e-tongue setup consisted of an array of sensing units made with layer-by-layer films deposited onto gold interdigitated electrodes. Significantly, the sensing units could be reused with adequate reproducibility after a simple washing procedure, thus indicating that there is no cross-contamination in three independent sets of measurements. A high performance was achieved by treating the capacitance data with the multidimensional projection techniques Principal Component Analysis (PCA), Interactive Document Map (IDMAP), and Sammon’s Mapping. While an optimized performance was demonstrated with IDMAP and feature selection, during which data of a limited frequency range were used, the distinction of all soil samples was also possible with the well-established PCA analysis for measurements at a single frequency. The successful use of a simple microfluidic e-tongue for soil analysis paves the way for enhanced tools to support precision agriculture. Full article
(This article belongs to the Special Issue Bioinspired Chemical Sensing)
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Open AccessArticle Surface Plasmon Resonance Immunosensor for the Detection of Campylobacter jejuni
Chemosensors 2017, 5(2), 16; doi:10.3390/chemosensors5020016
Received: 31 March 2017 / Revised: 25 April 2017 / Accepted: 4 May 2017 / Published: 16 May 2017
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Abstract
Campylobacteriosis is an internationally important foodborne disease caused by Campylobacter jejuni. The bacterium is prevalent in chicken meat and it is estimated that as much as 90% of chicken meat on the market may be contaminated with the bacterium. The current gold
[...] Read more.
Campylobacteriosis is an internationally important foodborne disease caused by Campylobacter jejuni. The bacterium is prevalent in chicken meat and it is estimated that as much as 90% of chicken meat on the market may be contaminated with the bacterium. The current gold standard for the detection of C. jejuni is the culturing method, which takes at least 48 h to confirm the presence of the bacterium. Hence, the aim of this work was to investigate the development of a Surface Plasmon Resonance (SPR) sensor platform for C. jejuni detection. Bacterial strains were cultivated in-house and used in the development of the sensor. SPR sensor chips were first functionalized with polyclonal antibodies raised against C. jejuni using covalent attachment. The gold chips were then applied for the direct detection of C. jejuni. The assay conditions were then optimized and the sensor used for C. jejuni detection, achieving a detection limit of 8 × 106 CFU·mL−1. The sensitivity of the assay was further enhanced to 4 × 104 CFU·mL−1 through the deployment of a sandwich assay format using the same polyclonal antibody. The LOD obtained in the sandwich assay was higher than that achieved using commercial enzyme-linked immunosorbent assay (ELISA) (106–107 CFU·mL−1). This indicate that the SPR-based sandwich sensor method has an excellent potential to replace ELISA tests for C. jejuni detection. Specificity studies performed with Gram-positive and Gram-negative bacteria, demonstrated the high specific of the sensor for C. jejuni. Full article
(This article belongs to the Special Issue Biosensors Applications in Food Safety)
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Open AccessFeature PaperArticle Highly Sensitive ZnO(Ga, In) for Sub-ppm Level NO2 Detection: Effect of Indium Content
Chemosensors 2017, 5(2), 18; doi:10.3390/chemosensors5020018
Received: 21 April 2017 / Revised: 18 May 2017 / Accepted: 25 May 2017 / Published: 1 June 2017
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Abstract
Nanocrystalline ZnO, ZnO(Ga), and ZnO(Ga, In) samples with different indium contents were prepared by wet-chemical method and characterized in detail by ICP-MS and XRD methods. Gas sensing properties toward NO2 were studied at 150–450 °C by DC conductance measurements. The optimal temperature
[...] Read more.
Nanocrystalline ZnO, ZnO(Ga), and ZnO(Ga, In) samples with different indium contents were prepared by wet-chemical method and characterized in detail by ICP-MS and XRD methods. Gas sensing properties toward NO2 were studied at 150–450 °C by DC conductance measurements. The optimal temperature for gas sensing experiments was determined. The dependence of the ZnO(Ga, In) sensor signal to NO2 at 250 °C correlates with the change of conductivity of the samples. The introduction of indium into the system leads to an increase in the values of the sensor signal in the temperature range T < 250 °C. The investigation of the local sample conductivity by scanning spreading resistance microscopy demonstrates that, at high indium content, the sensor properties are determined by the In–Ga–Zn–O layer that forms on the ZnO surface. Full article
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Open AccessArticle Ultra-Sensitive Optical Resonator for Organic Solvents Detection Based on Whispering Gallery Modes
Chemosensors 2017, 5(2), 19; doi:10.3390/chemosensors5020019
Received: 23 March 2017 / Revised: 13 May 2017 / Accepted: 1 June 2017 / Published: 5 June 2017
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Abstract
In this paper, a novel technique using an ultra-sensitive optical resonator based on whispering gallery modes (WGM) is proposed to detect the diffusion of organic solvents. The sensor configuration is a micro-cavity made of polymeric material. When the solvent starts to diffuse, the
[...] Read more.
In this paper, a novel technique using an ultra-sensitive optical resonator based on whispering gallery modes (WGM) is proposed to detect the diffusion of organic solvents. The sensor configuration is a micro-cavity made of polymeric material. When the solvent starts to diffuse, the polymer of the cavity starts to swallow that solvent. A swollen elastomer is in fact a solution, except that its mechanical response is now elastic rather than viscous. As solvents fill the network, chains are extended. In turn, that leads to the change of the morphology and mechanical properties of the sensing element. These changes could be measured by tracking the WGM shifts. Several experiments were carried out to measure that swelling force. Ethanol and methanol are used in this paper as candidates to study their driving force of diffusion (concentration gradient) on the cavity. Additionally, this sensing design can be used for biological sensing application. Breath diagnosis can use this configuration in diabetes diagnosis since a solvent like acetone concentration in human breath leads to a quick, convenient, accurate, and painless breath diagnosis of diabetes. The optical resonator results are verified through two different analyses: theoretical and experimental modeling. These micro-optical cavities have been examined using preliminary experiments to fully investigate their response and to verify the numerical analysis. Results show that the proposed sensor yields sensitivity for the driving force of diffusion (concentration gradient) (9.405 × 1013 pm/N) with a measurement precision of ~3.6 fN. Full article
(This article belongs to the Special Issue Chemical Microsensors)
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Review

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Open AccessReview Enzymes as Tools in MIP-Sensors
Chemosensors 2017, 5(2), 11; doi:10.3390/chemosensors5020011
Received: 24 December 2016 / Revised: 17 March 2017 / Accepted: 20 March 2017 / Published: 26 March 2017
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Abstract
Molecularly imprinted polymers (MIPs) have the potential to complement antibodies in bioanalysis, are more stable under harsh conditions, and are potentially cheaper to produce. However, the affinity and especially the selectivity of MIPs are in general lower than those of their biological pendants.
[...] Read more.
Molecularly imprinted polymers (MIPs) have the potential to complement antibodies in bioanalysis, are more stable under harsh conditions, and are potentially cheaper to produce. However, the affinity and especially the selectivity of MIPs are in general lower than those of their biological pendants. Enzymes are useful tools for the preparation of MIPs for both low and high-molecular weight targets: As a green alternative to the well-established methods of chemical polymerization, enzyme-initiated polymerization has been introduced and the removal of protein templates by proteases has been successfully applied. Furthermore, MIPs have been coupled with enzymes in order to enhance the analytical performance of biomimetic sensors: Enzymes have been used in MIP-sensors as “tracers” for the generation and amplification of the measuring signal. In addition, enzymatic pretreatment of an analyte can extend the analyte spectrum and eliminate interferences. Full article
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Open AccessReview Two-Dimensional Transition Metal Disulfides for Chemoresistive Gas Sensing: Perspective and Challenges
Chemosensors 2017, 5(2), 15; doi:10.3390/chemosensors5020015
Received: 5 April 2017 / Revised: 1 May 2017 / Accepted: 3 May 2017 / Published: 5 May 2017
Cited by 1 | PDF Full-text (5079 KB) | HTML Full-text | XML Full-text
Abstract
Transition metal disulfides have been attracting significant attentions in recent years. There are extensive applications of transition metal disulfides, especially on gas sensing applications, due to their large specific surface-to-volume ratios, high sensitivity to adsorption of gas molecules and tunable surface functionality depending
[...] Read more.
Transition metal disulfides have been attracting significant attentions in recent years. There are extensive applications of transition metal disulfides, especially on gas sensing applications, due to their large specific surface-to-volume ratios, high sensitivity to adsorption of gas molecules and tunable surface functionality depending on the decoration species or functional groups. However, there are several drawbacks such as poor gas selectivity, sluggish recovery characteristics and difficulty in the fabrication of large-scale devices. Here, we provide a review of recent progress on the chemoresistive gas sensing properties of two-dimensional transition metal disulfides. This review also provides various methods to enhance the gas sensing performance of two-dimensional disulfides, such as surface functionalization, decoration receptor functions and developing nanostructures. Full article
(This article belongs to the Special Issue Novel 2D-Inorganic Materials for Gas Sensing)
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Open AccessReview Two-Dimensional Zinc Oxide Nanostructures for Gas Sensor Applications
Chemosensors 2017, 5(2), 17; doi:10.3390/chemosensors5020017
Received: 13 April 2017 / Revised: 16 May 2017 / Accepted: 19 May 2017 / Published: 26 May 2017
Cited by 1 | PDF Full-text (8515 KB) | HTML Full-text | XML Full-text
Abstract
Two-dimensional (2D) nanomaterials, due to their unique physical and chemical properties, are showing great potential in catalysis and electronic/optoelectronic devices. Moreover, thanks to the high surface to volume ratio, 2D materials provide a large specific surface area for the adsorption of molecules, making
[...] Read more.
Two-dimensional (2D) nanomaterials, due to their unique physical and chemical properties, are showing great potential in catalysis and electronic/optoelectronic devices. Moreover, thanks to the high surface to volume ratio, 2D materials provide a large specific surface area for the adsorption of molecules, making them efficient in chemical sensing applications. ZnO, owing to its many advantages such as high sensitivity, stability, and low cost, has been one of the most investigated materials for gas sensing. Many ZnO nanostructures have been used to fabricate efficient gas sensors for the detection of various hazardous and toxic gases. This review summarizes most of the research articles focused on the investigation of 2D ZnO structures including nanosheets, nanowalls, nanoflakes, nanoplates, nanodisks, and hierarchically assembled nanostructures as a sensitive material for conductometric gas sensors. The synthesis of the materials and the sensing performances such as sensitivity, selectivity, response, and recovery times as well as the main influencing factors are summarized for each work. Moreover, the effect of mainly exposed crystal facets of the nanostructures on sensitivity towards different gases is also discussed. Full article
(This article belongs to the Special Issue Novel 2D-Inorganic Materials for Gas Sensing)
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