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Chemosensors, Volume 7, Issue 2 (June 2019)

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Open AccessArticle
Cyclic Voltammetric and Quantum Chemical Studies of a Poly(methionine) Modified Carbon Paste Electrode for Simultaneous Detection of Dopamine and Uric Acid
Chemosensors 2019, 7(2), 24; https://doi.org/10.3390/chemosensors7020024
Received: 26 March 2019 / Revised: 30 April 2019 / Accepted: 2 May 2019 / Published: 7 May 2019
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Abstract
Fabrication of biocompatible electrodes for the investigation of catecholamines is a known challenge. In this work, methionine was chosen as a modifier for fabrication of a biocompatible carbon paste electrode by electropolymerization, through cyclic voltammetry. The electrochemical behavior of the poly(methionine) modified carbon [...] Read more.
Fabrication of biocompatible electrodes for the investigation of catecholamines is a known challenge. In this work, methionine was chosen as a modifier for fabrication of a biocompatible carbon paste electrode by electropolymerization, through cyclic voltammetry. The electrochemical behavior of the poly(methionine) modified carbon paste electrode was characterized by cyclic voltammetry for simultaneous determination of dopamine (DA) and uric acid (UA) in a phosphate-buffered solution at pH 7.0. In the absence of an amino acid methionine layer, the bare carbon paste electrode exhibits rather poor voltammetric signals in DA and UA in the binary mixture, with oxidation potentials of DA and UA overlapping with each other. The poly(methionine) modified carbon paste electrode exhibits good catalytic activity with noticeably different oxidation potentials of DA and UA. The experimental results closely agree with the theoretical prediction based on a Fukui function complementary to the simulated electrostatic potential maps. Full article
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Open AccessArticle
Electro-Optical Gas Sensor Consisting of Nanostructured Paper Coating and an Ultrathin Sensing Element
Chemosensors 2019, 7(2), 23; https://doi.org/10.3390/chemosensors7020023
Received: 12 April 2019 / Revised: 26 April 2019 / Accepted: 29 April 2019 / Published: 1 May 2019
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Abstract
This work describes the use of a paper substrate for electro-optical detection of toxic hydrogen sulfide (H2S) gas. For electrical detection, a chemiresistive type of gas sensor was developed. Ultrathin gold film electrodes (UTGFE) were produced by physical vapor deposition of [...] Read more.
This work describes the use of a paper substrate for electro-optical detection of toxic hydrogen sulfide (H2S) gas. For electrical detection, a chemiresistive type of gas sensor was developed. Ultrathin gold film electrodes (UTGFE) were produced by physical vapor deposition of gold on nanostructured latex-coated paper substrate. The gas-sensing film was deposited on the electrodes by inkjet printing. The sensing films were characterized by atomic force microscopy, X-ray photoelectron spectroscopy and conductometry. The sensing films showed more than seven orders of magnitude change in resistance when exposed to as low as 1 part per million (ppm) H2S gas at room temperature. Besides resistive response, the change in color of the sensing films was studied on a paper substrate, both as a function of print density of the sensing material and H2S concentration. For quantification of the analyte the red, green and blue color deconvolution was performed on the pictures of the paper strip indicator using an open source software. A clear response was obtained from the blue channel. The inexpensive disposable color strips produced on the paper substrate can be used for qualitative and quantitative detection (as low as 1.5 ppm) of H2S gas. Full article
(This article belongs to the Special Issue Thin Film Based Sensors)
Open AccessReview
Low Molecular Weight Fluorescent Probes (LMFPs) to Detect the Group 12 Metal Triad
Chemosensors 2019, 7(2), 22; https://doi.org/10.3390/chemosensors7020022
Received: 2 March 2019 / Revised: 17 April 2019 / Accepted: 19 April 2019 / Published: 28 April 2019
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Abstract
Fluorescence sensing, of d-block elements such as Cu2+, Fe3+, Fe2+, Cd2+, Hg2+, and Zn2+ has significantly increased since the beginning of the 21st century. These particular metal ions play essential roles in [...] Read more.
Fluorescence sensing, of d-block elements such as Cu2+, Fe3+, Fe2+, Cd2+, Hg2+, and Zn2+ has significantly increased since the beginning of the 21st century. These particular metal ions play essential roles in biological, industrial, and environmental applications, therefore, there has been a drive to measure, detect, and remediate these metal ions. We have chosen to highlight the low molecular weight fluorescent probes (LMFPs) that undergo an optical response upon coordination with the group 12 triad (Zn2+, Cd2+, and Hg2+), as these metals have similar chemical characteristics but behave differently in the environment. Full article
(This article belongs to the Special Issue Chemical Sensors for Heavy Metals/Toxin Detection)
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Open AccessArticle
Optical Detection of Bromide Ions Using Pt(II)-5,10,15,20-Tetra-(4-methoxy-phenyl)-porphyrin
Chemosensors 2019, 7(2), 21; https://doi.org/10.3390/chemosensors7020021
Received: 29 March 2019 / Revised: 23 April 2019 / Accepted: 23 April 2019 / Published: 27 April 2019
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Abstract
Bromide ions are present in many environments, such as sedative drugs, methyl-bromide-treated vegetables and seawater. Excess bromide in humans interferes with iodide metabolism and is considered toxic. The need for fast and inexpensive methods for bromide detection is of interest. Spectrophotometric detection methods [...] Read more.
Bromide ions are present in many environments, such as sedative drugs, methyl-bromide-treated vegetables and seawater. Excess bromide in humans interferes with iodide metabolism and is considered toxic. The need for fast and inexpensive methods for bromide detection is of interest. Spectrophotometric detection methods provide accurate and sensitive results. The well-known ability of metalloporphyrins to bind anionic ligands to the central metal ion has been exploited. The changes in the optical properties of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) under the influence of bromide ions allowed us to achieve a fast, simple and reliable UV-vis spectrophotometric method of detection with a detection limit of 2.5 × 10−8 M and a good confidence coefficient: 99.05%. The potential interfering ions, such as Cl, I, NO2, NO3, SCN, SO32−, SO42− and PO43− of 100-fold higher and Cl and R-S of 1000-fold higher concentrations in the mixture as compared to the determined concentration of bromide ions (c = 10−5 M), were tested and did not influence the results. The behavior of the sensitive porphyrin in various pH media was investigated in order to determine their influence upon the bromide detection capacity. Full article
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Open AccessArticle
Polyvinyl Acetate Film-Based Quartz Crystal Microbalance for the Detection of Benzene, Toluene, and Xylene Vapors in Air
Chemosensors 2019, 7(2), 20; https://doi.org/10.3390/chemosensors7020020
Received: 22 March 2019 / Revised: 8 April 2019 / Accepted: 19 April 2019 / Published: 22 April 2019
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Abstract
Vapors of volatile organic compounds such as benzene, toluene, and xylene (BTX) may cause health concerns. The sensitive detection of these compounds in air remains challenging. In this study, we reported on modification of the Quartz Crystal Microbalance (QCM) sensing chip using polyvinyl [...] Read more.
Vapors of volatile organic compounds such as benzene, toluene, and xylene (BTX) may cause health concerns. The sensitive detection of these compounds in air remains challenging. In this study, we reported on modification of the Quartz Crystal Microbalance (QCM) sensing chip using polyvinyl acetate (PVAc) film as active coating for the analysis of BTX vapors. The PVAc film was deposited on the QCM sensing chip surface by a spin coating technique. The morphology of the PVAc films was confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sensitivities of PVAc based QCM system for benzene, toluene, and xylene analyses were 0.018, 0.041, and 0.081 Hz/ppm, respectively. The high sensitivity of the proposed QCM system for analysis of BTX vapors is believed to be due to the effective interaction between the PVAc film and BTX molecules. The analyte vapor pressure appears to also affect the sensitivity. These data show that the prepared QCM sensor has a low time constant, good reproducibility, and excellent stability. It offers an alternative to the developed methods for detection of BTX and possibly other aromatic hydrocarbons in the air. Full article
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Open AccessCommunication
An Organophosphorus(III)-Selective Chemodosimeter for the Ratiometric Electrochemical Detection of Phosphines
Chemosensors 2019, 7(2), 19; https://doi.org/10.3390/chemosensors7020019
Received: 10 March 2019 / Revised: 2 April 2019 / Accepted: 3 April 2019 / Published: 11 April 2019
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Abstract
The high toxicity of phosphine and the use of organophosphines as nerve agent precursors has provoked the requirement for a rapid and reliable detection methodology for their detection. Herein, we demonstrate that a ferrocene-derived molecular probe, armed with an azidobenzene trigger, delivers a [...] Read more.
The high toxicity of phosphine and the use of organophosphines as nerve agent precursors has provoked the requirement for a rapid and reliable detection methodology for their detection. Herein, we demonstrate that a ferrocene-derived molecular probe, armed with an azidobenzene trigger, delivers a ratiometric electrochemical signal selectively in response to organophosphorus(III) compounds and can be accurately measured with an inexpensive, handheld potentiostat. Through an intensive assay optimization process, conditions were found that could determine the presence of a model organophosphine(III) nerve agent precursor within minutes and achieved a limit of detection for triphenylphosphine of just 13 ppm. Due to the portability of the detection system and the excellent stability of the probe in solution, we envisaged that this proof-of-concept of work could easily be taken into the field to enable potentially toxic organophosphorus(III) compounds to be detected at the point-of-need. Full article
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Open AccessArticle
Improved Synthesis of ZnO Nanowalls: Effects of Chemical Bath Deposition Time and Annealing Temperature
Chemosensors 2019, 7(2), 18; https://doi.org/10.3390/chemosensors7020018
Received: 18 February 2019 / Revised: 26 March 2019 / Accepted: 27 March 2019 / Published: 1 April 2019
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Abstract
Zinc Oxide (ZnO) nanowalls (NWLs) are interesting nanostructures for sensing application. In order to push towards the realization of room-temperature operating sensors, a detailed investigation of the synthesis effect on the electrical and optical properties is needed. This work focuses on the low-cost [...] Read more.
Zinc Oxide (ZnO) nanowalls (NWLs) are interesting nanostructures for sensing application. In order to push towards the realization of room-temperature operating sensors, a detailed investigation of the synthesis effect on the electrical and optical properties is needed. This work focuses on the low-cost synthesis of ZnO NWLs by means of chemical bath deposition (growth time of 5, 60, and 120 min) followed by annealing in inert ambient (temperature of 100, 200, and 300 °C). The as-grown NWLs show a typical intertwined network of vertical sheets whose features (thickness and height) stabilize after 60 min growth. During thermal annealing, NWLs are converted into ZnO. The electric transport across the ZnO NWL network radically changes after annealing. A higher resistivity was observed for longer deposition times and for higher annealing temperatures, at which the photoluminescence spectra resemble those obtained for ZnO material. A longer deposition time allows for a better transformation to ZnO during the annealing, thanks to the presence of ZnO seeds just after the growth. These findings can have a significant role in promoting the realization of room-temperature operating sensors based on ZnO NWLs. Full article
(This article belongs to the Special Issue Nanotechnology Efforts for Chemical Sensors)
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Open AccessArticle
Surface Functionalization of Cotton Fabric with Fluorescent Dendrimers, Spectral Characterization, Cytotoxicity, Antimicrobial and Antitumor Activity
Chemosensors 2019, 7(2), 17; https://doi.org/10.3390/chemosensors7020017
Received: 6 February 2019 / Revised: 21 March 2019 / Accepted: 25 March 2019 / Published: 30 March 2019
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Abstract
Poly(propylenimine) dendrimers from first and third generations modified with 1,8-naphthalimide units and their Zn(II) complexes have been investigated by absorption and fluorescence spectroscopy. These dendrimers have been deposited on a cotton cloth by the extraction method, producing yellow-colored textile materials. They have been [...] Read more.
Poly(propylenimine) dendrimers from first and third generations modified with 1,8-naphthalimide units and their Zn(II) complexes have been investigated by absorption and fluorescence spectroscopy. These dendrimers have been deposited on a cotton cloth by the extraction method, producing yellow-colored textile materials. They have been characterized by defining their color coordinates L*a*b*, XYZ and xy. The antimicrobial activity of dendrimers has been investigated in vitro against model gram-positive and gram-negative bacteria and yeasts. Being deposited onto the surface of cotton fabric, the studied dendrimers reduced bacterial growth and prevented the formation of bacterial biofilm. Anticancer and cytotoxicity activities have also been performed against HeLa and Lep-3 human tumor cell lines as model systems. Full article
(This article belongs to the Special Issue New insides in Fluorescent and Colorimetric Probes)
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