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

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Research

Open AccessArticle Chemo-Electrical Signal Transduction by Using Stimuli-Responsive Polymer Gate-Modified Field Effect Transistor
Chemosensors 2014, 2(2), 97-107; doi:10.3390/chemosensors2020097
Received: 8 October 2013 / Revised: 10 January 2014 / Accepted: 13 March 2014 / Published: 26 March 2014
Cited by 1 | PDF Full-text (331 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle A Low-Cost Fluorescent Sensor for pCO2 Measurements
Chemosensors 2014, 2(2), 108-120; doi:10.3390/chemosensors2020108
Received: 16 July 2013 / Revised: 24 December 2013 / Accepted: 21 March 2014 / Published: 3 April 2014
Cited by 1 | PDF Full-text (632 KB) | HTML Full-text | XML Full-text
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.
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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)
Open AccessArticle Synthesis, Characterization and Sensing Properties of AZO and IZO Nanomaterials
Chemosensors 2014, 2(2), 121-130; doi:10.3390/chemosensors2020121
Received: 24 December 2013 / Revised: 9 April 2014 / Accepted: 13 May 2014 / Published: 23 May 2014
Cited by 5 | PDF Full-text (452 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle Electrochemical Detection with Preconcentration: Nitroenergetic Contaminants
Chemosensors 2014, 2(2), 131-144; doi:10.3390/chemosensors2020131
Received: 25 November 2013 / Revised: 23 May 2014 / Accepted: 28 May 2014 / Published: 10 June 2014
Cited by 1 | PDF Full-text (623 KB) | HTML Full-text | XML Full-text | Supplementary Files
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
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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
Open AccessArticle Piezoresistive Chemical Sensors Based on Functionalized Hydrogels
Chemosensors 2014, 2(2), 145-170; doi:10.3390/chemosensors2020145
Received: 3 July 2013 / Revised: 15 April 2014 / Accepted: 14 May 2014 / Published: 10 June 2014
Cited by 2 | PDF Full-text (1069 KB) | HTML Full-text | XML Full-text
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
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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)
Open AccessArticle Discriminating Bacteria with Optical Sensors Based on Functionalized Nanoporous Xerogels
Chemosensors 2014, 2(2), 171-181; doi:10.3390/chemosensors2020171
Received: 13 December 2013 / Revised: 12 May 2014 / Accepted: 22 May 2014 / Published: 11 June 2014
Cited by 2 | PDF Full-text (808 KB) | HTML Full-text | XML Full-text | Supplementary Files
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
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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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