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331 KiB

Open AccessArticle

Chemo-Electrical Signal Transduction by Using Stimuli-Responsive Polymer Gate-Modified Field Effect Transistor

by Akira Matsumoto, Yusuke Tsurui, Hiroko Matsumoto, Yasuhiro Maeda, Toru Hoshi, Takashi Sawaguchi and Yuji Miyahara

Chemosensors 2014, 2(2), 97-107; https://doi.org/10.3390/chemosensors2020097 - 26 Mar 2014

Cited by 1 | Viewed by 8885

Abstract

A glucose-responsive polymer brush was designed on a gold electrode and exploited as an extended gate for a field effect transistor (FET) based biosensor. A permittivity change at the gate interface due to the change in hydration upon specific binding with glucose was [...] Read more.

A glucose-responsive polymer brush was designed on a gold electrode and exploited as an extended gate for a field effect transistor (FET) based biosensor. A permittivity change at the gate interface due to the change in hydration upon specific binding with glucose was detectable. The rate of response was markedly enhanced compared to the previously studied cross-linked or gel-coupled electrode, owing to its kinetics involving no process of the polymer network diffusion. This finding may offer a new strategy of the FET-based biosensors effective not only for large molecules but also for electrically neutral molecules such as glucose with improved kinetics. Full article

(This article belongs to the Special Issue Hydrogel-Based Chemosensors)

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632 KiB

Open AccessArticle

A Low-Cost Fluorescent Sensor for pCO₂ Measurements

by Xudong Ge, Yordan Kostov, Robert Henderson, Nicholas Selock and Govind Rao

Chemosensors 2014, 2(2), 108-120; https://doi.org/10.3390/chemosensors2020108 - 03 Apr 2014

Cited by 10 | Viewed by 8329

Abstract

Global warming is believed to be caused by increasing amounts of greenhouse gases (mostly CO₂) discharged into the environment by human activity. In addition to an increase in environmental temperature, an increased CO₂ level has also led to ocean acidification. [...] Read more.

Global warming is believed to be caused by increasing amounts of greenhouse gases (mostly CO₂) discharged into the environment by human activity. In addition to an increase in environmental temperature, an increased CO₂ level has also led to ocean acidification. Ocean acidification and rising temperatures have disrupted the water’s ecological balance, killing off some plant and animal species, while encouraging the overgrowth of others. To minimize the effect of global warming on local ecosystem, there is a strong need to implement ocean observing systems to monitor the effects of anthropogenic CO₂ and the impacts thereof on ocean biological productivity. Here, we describe the development of a low-cost fluorescent sensor for pCO₂ measurements. The detector was exclusively assembled with low-cost optics and electronics, so that it would be affordable enough to be deployed in great numbers. The system has several novel features, such as an ideal 90° separation between excitation and emission, a beam combiner, a reference photodetector, etc. Initial tests showed that the system was stable and could achieve a high resolution despite the low cost. Full article

(This article belongs to the Special Issue Photonic Sensors for Biological and Chemical Measurements)

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452 KiB

Open AccessArticle

Synthesis, Characterization and Sensing Properties of AZO and IZO Nanomaterials

by Mokhtar Hjiri, Lassaad El Mir and Salvatore Gianluca Leonardi

Chemosensors 2014, 2(2), 121-130; https://doi.org/10.3390/chemosensors2020121 - 23 May 2014

Cited by 28 | Viewed by 9275

Abstract

Al-doped ZnO (AZO) and In-doped ZnO (IZO) nanopowders were prepared by a sol-gel route and subsequent drying in ethanol under supercritical conditions. The morphological and microstructural properties were investigated by transmission electron microscopy (TEM) analysis and X-ray powder diffraction (XRD). The characterization study [...] Read more.

Al-doped ZnO (AZO) and In-doped ZnO (IZO) nanopowders were prepared by a sol-gel route and subsequent drying in ethanol under supercritical conditions. The morphological and microstructural properties were investigated by transmission electron microscopy (TEM) analysis and X-ray powder diffraction (XRD). The characterization study showed that the AZO and IZO nanoparticles were crystalline and exhibited the hexagonal wurtzite structure. Chemoresistive devices consisting of a thick layer of synthesized nanoparticles on interdigitated alumina substrates have been fabricated and their electrical and sensing characteristics were investigated. The sensor performances of the AZO and IZO nanoparticles for carbon monoxide (CO) were reported. The results indicated that both doped-sensors exhibited higher response and quick response/recovery dynamics compared to a ZnO-based sensor. These interesting sensing properties were discussed on the basis of the characterization data reported. Full article

(This article belongs to the Special Issue Solid State Gas Sensors)

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623 KiB

Open AccessArticle

Electrochemical Detection with Preconcentration: Nitroenergetic Contaminants

by Brandy J. Johnson, Mansoor Nasir, Ronald L. Siefert, Iwona A. Leska, Jeffrey S. Erickson, Paul T. Charles, Brian J. Melde and Jenna R. Taft

Chemosensors 2014, 2(2), 131-144; https://doi.org/10.3390/chemosensors2020131 - 10 Jun 2014

Cited by 1 | Viewed by 4875

Abstract

This effort evaluated the potential of two prototype devices for enhanced electrochemical detection of 2,4,6-trinitrotoluene (TNT) and dinitrotoluene (DNT) following preconcentration using an organosilicate sorbent. The bench-scale prototype provides adsorption of the targets from aqueous solution followed by elution in a mixture of [...] Read more.

This effort evaluated the potential of two prototype devices for enhanced electrochemical detection of 2,4,6-trinitrotoluene (TNT) and dinitrotoluene (DNT) following preconcentration using an organosilicate sorbent. The bench-scale prototype provides adsorption of the targets from aqueous solution followed by elution in a mixture of methanol and potassium chloride (KCl). Following elution, the eluant is diluted using an aqueous KCl solution to provide sufficient electrolyte for electrochemical analysis. Concentrations of methanol greater than 50% were detrimental to sensor performance and lifetime. Calibration of the electrochemical sensor was completed and results of electrochemical analysis were compared to those of HPLC analysis over a range of concentrations and in varied matrices. TNT detection was found to be consistent and detection limits were improved from 200 ppb to 3 ppb depending on the sample volume utilized. DNT detection showed higher variability and significantly greater false response rates. On the basis of these results, a second, more advanced, prototype was developed and utilized in limited field trials with the intention of moving the technology toward in situ applications. Full article

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1069 KiB

Open AccessArticle

Piezoresistive Chemical Sensors Based on Functionalized Hydrogels

by Margarita Guenther, Thomas Wallmersperger and Gerald Gerlach

Chemosensors 2014, 2(2), 145-170; https://doi.org/10.3390/chemosensors2020145 - 10 Jun 2014

Cited by 14 | Viewed by 6959

Abstract

Thin films of analyte-specific hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain chemomechanical sensors that can serve as selective biochemical sensors for a continuous monitoring of metabolites. The gel swelling pressure has been monitored in simulated physiological solutions by means of [...] Read more.

Thin films of analyte-specific hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain chemomechanical sensors that can serve as selective biochemical sensors for a continuous monitoring of metabolites. The gel swelling pressure has been monitored in simulated physiological solutions by means of the output signal of piezoresistive sensors. The interference by fructose, human serum albumin, pH, and ionic concentration on glucose sensing was studied. With the help of a database containing the calibration curves of the hydrogel-based sensors at different values of pH and ionic strength, the corrected values of pH and glucose concentration were determined using a novel calibration algorithm. Full article

(This article belongs to the Special Issue Hydrogel-Based Chemosensors)

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808 KiB

Open AccessArticle

Discriminating Bacteria with Optical Sensors Based on Functionalized Nanoporous Xerogels

by Sabine Crunaire, Pierre R. Marcoux, Khanh-Quyen Ngo, Jean-Pierre Moy, Frédéric Mallard and Thu-Hoa Tran-Thi

Chemosensors 2014, 2(2), 171-181; https://doi.org/10.3390/chemosensors2020171 - 11 Jun 2014

Cited by 8 | Viewed by 7600

Abstract

An innovative and low-cost method is proposed for the detection and discrimination of indole-positive pathogen bacteria. The method allows the non-invasive detection of gaseous indole, released by bacteria, with nanoporous colorimetric sensors. The innovation comes from the use of nanoporous matrices doped with [...] Read more.

An innovative and low-cost method is proposed for the detection and discrimination of indole-positive pathogen bacteria. The method allows the non-invasive detection of gaseous indole, released by bacteria, with nanoporous colorimetric sensors. The innovation comes from the use of nanoporous matrices doped with 4-(dimethylamino)-cinnamaldehyde, which act as sponges to trap and concentrate the targeted analyte and turn from transparent to dark green, long before the colonies get visible with naked eyes. With such sensors, it was possible to discriminate E. coli from H. alvei, two indole-positive and negative bacteria after seven hours of incubation. Full article

(This article belongs to the Special Issue Photonic Sensors for Biological and Chemical Measurements)

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Chemosensors, Volume 2, Issue 2 (June 2014) – 6 articles , Pages 97-181

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