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Chemosensors, Volume 9, Issue 1 (January 2021) – 18 articles

Cover Story (view full-size image): Fluorescent molecular rotors with aggregation-induced emission (AIE) were reported for the real-time monitoring of polyurethane (PU) formation in solution. The agreement between viscosity and fluorescence variations during the polymerization progress suggests the innovative use of a low-cost fluorescence detection system based on an LED/photodiode, the assembly of which, can be mounted directly on the reaction apparatus. The general validity of the proposed experiments enabled the monitoring of polyurethane polymerization and suggests practical applications in a variety of industrial polymers, eliciting enhancements in viscosity during polymerization. View this paper
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Open AccessEditorial
Acknowledgment to Reviewers of Chemosensors in 2020
Chemosensors 2021, 9(1), 18; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010018 - 19 Jan 2021
Viewed by 374
Abstract
Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that Chemosensors maintains its standards for the high quality of its published papers [...] Full article
Open AccessArticle
Preparation and Characterization of Au/NiPc/Anti-p53/BSA Electrode for Application as a p53 Antigen Sensor
Chemosensors 2021, 9(1), 17; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010017 - 19 Jan 2021
Viewed by 335
Abstract
While the tumor suppressor protein p53 regulates the cell cycle to prevent cell damage, it also triggers apoptosis and prevents cancer. These inhibitory functions may disappear once the p53 gene is mutated. Under these circumstances, the detection of p53 protein concentrations can have [...] Read more.
While the tumor suppressor protein p53 regulates the cell cycle to prevent cell damage, it also triggers apoptosis and prevents cancer. These inhibitory functions may disappear once the p53 gene is mutated. Under these circumstances, the detection of p53 protein concentrations can have significant clinical applications. In this study, nickel phthalocyanine (NiPc) was coated on a gold electrode to produce a modified Au/NiPc electrode. p53 antibodies were bonded to the Au/NiPc electrode by the Ni+2 ion in NiPc, which can be self-assembled with the imidazole group of the p53 protein. The Au/NiPc/anti-p53 electrode was subsequently dripped with a buffer solution of bovine serum albumin (BSA) to form the Au/NiPc/anti-p53/BSA electrode, which was used for the detection of p53 antigen under 10 mM potassium ferricyanide/potassium ferrocyanide (K3Fe(CN)6/K4Fe(CN)6) solution by cyclic voltammetry and differential pulse voltammetry analyses. The linear detection range and the sensitivity for the p53 antigen were 0.1–500 pg/mL and 60.65 μA/Log (pg/mL)-cm2, respectively, with a detection time of 90–150 s. In addition, Au/NiPc/anti-p53 (100 ng/mL)/BSA electrodes were tested for specificity using glucose, bovine serum albumin, histidine, ascorbic acid, uric acid, prostate-specific antigen, human serum albumin, and human immunoglobulin G. All p-values were <0.0005, indicating an outstanding specificity. Full article
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Open AccessReview
Bicyclic 1,3a,6a-Triazapentalene Chromophores: Synthesis, Spectroscopy and Their Use as Fluorescent Sensors and Probes
Chemosensors 2021, 9(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010016 - 15 Jan 2021
Viewed by 413
Abstract
The 1,3a,6a-triazapentalene (TAP) is an aromatic heterocyclic fluorescent dye with interesting features such as its small size, large Stokes shift, solvatochromism, and emission wavelengths that are spread across the visible spectrum. TAPs have been synthesized via different synthetic strategies involving click−cyclization−aromatization domino reactions, [...] Read more.
The 1,3a,6a-triazapentalene (TAP) is an aromatic heterocyclic fluorescent dye with interesting features such as its small size, large Stokes shift, solvatochromism, and emission wavelengths that are spread across the visible spectrum. TAPs have been synthesized via different synthetic strategies involving click−cyclization−aromatization domino reactions, gold-catalyzed cyclization of propargyl triazoles or triazolization of acetophenones. As a result, TAPs with diverse substitution patterns were obtained, showing varying fluorescence properties. Based on these properties, several TAPs have been selected and studied as fluorescent imaging probes in living cells and as sensors. This mini review provides an overview of the research on the bicyclic TAPs and does not comment on the literature about benzo or otherwise fused systems. The synthetic methodologies for the preparation of TAPs, the substituent effects on the fluorescence properties, and the behavior of the TAP core as an element of biological imaging probes and sensors are discussed. Full article
(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)
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Open AccessArticle
Electrochemical Detection of a Local Anesthetic Dibucaine at Arrays of Liquid|Liquid MicroInterfaces
Chemosensors 2021, 9(1), 15; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010015 - 15 Jan 2021
Viewed by 309
Abstract
Electrochemical characterization and detection of protonated dibucaine (DIC+) at microinterface array across water|1,6-dichlorohexane were performed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Some thermodynamic parameters of dibucaine, such as the standard transfer potential, the Gibbs energy of transfer [...] Read more.
Electrochemical characterization and detection of protonated dibucaine (DIC+) at microinterface array across water|1,6-dichlorohexane were performed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Some thermodynamic parameters of dibucaine, such as the standard transfer potential, the Gibbs energy of transfer and the partition coefficient, were estimated by CV. In addition to the analytical parameters, the impact of bovine serum albumin (BSA) on dibucaine detection (in artificial serum matrices) was also investigated. DPV was applied to detect a lower concentration of DIC+, resulting in a detection limit of 0.9 ± 0.06 µM. While the presence of BSA affected CV, demonstrated as reduced current responses, DPV was confirmed to be an efficient method for lowering concentrations of the dibucaine detection in the artificial serum matrix in the presence of BSA, with a limit of detection (LOD) of 1.9 ± 0.12 µM. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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Open AccessReview
Nanomaterials Based Electrochemical Sensors for Serotonin Detection: A Review
Chemosensors 2021, 9(1), 14; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010014 - 14 Jan 2021
Viewed by 487
Abstract
The present review deals with the recent progress made in the field of the electrochemical detection of serotonin by means of electrochemical sensors based on various nanomaterials incorporated in the sensitive element. Due to the unique chemical and physical properties of these nanomaterials, [...] Read more.
The present review deals with the recent progress made in the field of the electrochemical detection of serotonin by means of electrochemical sensors based on various nanomaterials incorporated in the sensitive element. Due to the unique chemical and physical properties of these nanomaterials, it was possible to develop sensitive electrochemical sensors with excellent analytical performances, useful in the practice. The main electrochemical sensors used in serotonin detection are based on carbon electrodes modified with carbon nanotubes and various materials, such as benzofuran, polyalizarin red-S, poly(L-arginine), Nafion/Ni(OH)2, or graphene oxide, incorporating silver-silver selenite nanoparticles, as well as screen-printed electrodes modified with zinc oxide or aluminium oxide. Also, the review describes the nanocomposite sensors based on conductive polymers, tin oxide-tin sulphide, silver/polypyrole/copper oxide or a hybrid structure of cerium oxide-gold oxide nanofibers together with ruthenium oxide nanowires. The presentation focused on describing the sensitive materials, characterizing the sensors, the detection techniques, electroanalytical properties, validation and use of sensors in lab practice. Full article
(This article belongs to the Special Issue Voltammperometric Sensors)
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Open AccessArticle
Capacitance Electrochemical pH Sensor Based on Different Hafnium Dioxide (HfO2) Thicknesses
Chemosensors 2021, 9(1), 13; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010013 - 10 Jan 2021
Viewed by 551
Abstract
Over the past years, to achieve better sensing performance, hafnium dioxide (HfO2) has been studied as an ion-sensitive layer. In this work, thin layers of hafnium dioxide (HfO2) were used as pH-sensitive membranes and were deposited by atomic layer [...] Read more.
Over the past years, to achieve better sensing performance, hafnium dioxide (HfO2) has been studied as an ion-sensitive layer. In this work, thin layers of hafnium dioxide (HfO2) were used as pH-sensitive membranes and were deposited by atomic layer deposition (ALD) process onto an electrolytic-insulating-semiconductor structure Al/Si/SiO2/HfO2 for the realization of a pH sensor. The thicknesses of the layer of the HfO2 studied in this work was 15, 19.5 and 39.9 nm. HfO2 thickness was controlled by ALD during the fabrication process. The sensitivity toward H+ was clearly higher when compared to other interfering ions such as potassium K+, lithium Li+, and sodium Na+ ions. Mott−Schottky and electrochemical impedance spectroscopy (EIS) analyses were used to characterise and to investigate the pH sensitivity. This was recorded by Mott–Schottky at 54.5, 51.1 and 49.2 mV/pH and by EIS at 5.86 p[H−1], 10.63 p[H−1], 12.72 p[H−1] for 15, 19.5 and 30 nm thickness of HfO2 ions sensitive layer, respectively. The developed pH sensor was highly sensitive and selective for H+ ions for the three thicknesses, 15, 19.5 and 39.9 nm, of HfO2-sensitive layer when compared to the other previously mentioned interferences. However, the pH sensor performances were better with 15 nm HfO2 thickness for the Mott–Schottky technique, whilst for EIS analyses, the pH sensors were more sensitive at 39.9 nm HfO2 thickness. Full article
(This article belongs to the Special Issue Feature Papers- Electrochemical Devices and Sensors)
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Open AccessReview
How to Improve the Performance of Electrochemical Sensors via Minimization of Electrode Passivation
Chemosensors 2021, 9(1), 12; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010012 - 06 Jan 2021
Viewed by 453
Abstract
It follows from critical evaluation of possibilities and limitations of modern voltammetric/amperometric methods that one of the biggest obstacles in their practical applications in real sample analysis is connected with electrode passivation/fouling by electrode reaction products and/or matrix components. This review summarizes possibilities [...] Read more.
It follows from critical evaluation of possibilities and limitations of modern voltammetric/amperometric methods that one of the biggest obstacles in their practical applications in real sample analysis is connected with electrode passivation/fouling by electrode reaction products and/or matrix components. This review summarizes possibilities how to minimise these problems in the field of detection of small organic molecules and critically compares their potential and acceptability in practical laboratories. Attention is focused on simple and fast electrode surface renewal, the use of disposable electrodes just for one and/or few measurements, surface modification minimising electrode fouling, measuring in flowing systems, application of rotating disc electrode, the use of novel separation methods preventing access of passivating particles to electrode surface and the novel electrode materials more resistant toward passivation. An attempt is made to predict further development in this field and to stress the need for more systematic and less random research resulting in new measuring protocols less amenable to complications connected with electrode passivation. Full article
(This article belongs to the Special Issue Feature Papers- Electrochemical Devices and Sensors)
Open AccessArticle
Comparing Surface Plasmon-Optical and Electronic Immuno-Sensing of Affinity Interactions—A Case Study
Chemosensors 2021, 9(1), 11; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010011 - 05 Jan 2021
Viewed by 444
Abstract
In this case study, we provide a few examples for affinity-sensors based on optical detection concepts and compare them with electronic read-out schemes. We concentrate and briefly summarize two of the most advanced versions in each category: one is a surface-plasmon field-enhanced fluorescence [...] Read more.
In this case study, we provide a few examples for affinity-sensors based on optical detection concepts and compare them with electronic read-out schemes. We concentrate and briefly summarize two of the most advanced versions in each category: one is a surface-plasmon field-enhanced fluorescence spectroscopic approach, while in the electronic sensing domain we concentrate on graphene-based field-effect transistors as the read-out platform. Both transduction principles are surface-sensitive and-selective, however, with penetration lengths into the analyte solution (e.g., into a flow cell attached) that are very different and that depend on totally different physical principles: while for surface-plasmons the evanescent character of the plasmon mode, propagating along the noble metal-solution interface with a penetration length in the order of 100 nm (for Au/water and a laser wavelength of = 632.8 nm), the “penetration depth” in electronic transistor-based sensing is governed by the Debye length which, for a physiological salt environment, amounts to less than 1 nm. Taking these differences into account, one can optimize the sensor read-out by the appropriate interfacial architecture used to functionalize the transducers by immobilizing one of the affinity interaction partners. We will discuss this for both concepts by giving a few examples of the achievable limit of detection for both methods. The examples discussed include a classical system, i.e., the binding of human chorionic gonadotropin (hCG) to its surface-immobilized antibodies or Fab fragments, the detection of lipopolysaccharides in a tethered bimolecular lipid membrane, and, as an example for small analyte detection by antibodies, the monitoring of aflatoxin B1, a member of the food toxin family of mycotoxins. Full article
(This article belongs to the Special Issue Organic-Inorganic Hybrid Chemo- and Bio-Sensors)
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Open AccessArticle
Nanoplasmonic Biosensing Approach for Endotoxin Detection in Pharmaceutical Field
Chemosensors 2021, 9(1), 10; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010010 - 04 Jan 2021
Viewed by 376
Abstract
The outer membrane of Gram-negative bacteria contains bacterial endotoxins known as Lipopolysaccharides (LPS). Owing to the strong immune responses induced in humans and animals, these large molecules have a strong toxic effect that can cause severe fever, hypotension, shock, and death. Endotoxins are [...] Read more.
The outer membrane of Gram-negative bacteria contains bacterial endotoxins known as Lipopolysaccharides (LPS). Owing to the strong immune responses induced in humans and animals, these large molecules have a strong toxic effect that can cause severe fever, hypotension, shock, and death. Endotoxins are often present in the environment and medical implants and represent undesirable contaminations of pharmaceutical preparations and medical devices. To overcome the limitations of the standard technique, novel methods for early and sensitive detection of LPS will be of crucial importance. In this work, an interesting approach for the sensitive detection of LPS has been realized by exploiting optical features of nanoplasmonic transducers supporting Localized Surface Plasmon Resonances (LSPRs). Ordered arrays of gold nano-prisms and nano-disks have been realized by nanospheres lithography. The realized transducers have been integrated into a simple and miniaturized lab-on-a-chip (LOC) platform and functionalized with specific antibodies as sensing elements for the detection of LPS. Interactions of specific antibodies anchored on protein A-modified sensor chips with the investigated analyte resulted in a spectral shift in the plasmonic resonance peak of the transducers. A good linear relationship between peak shifts and the LPS concentration has been demonstrated for the fabricated nano-structures with a detection limit down to 5 ng/mL. Integration with a proper microfluidic platform demonstrates the possibility of yielding a prototypal compact device to be used as an analytical test for quality determination of pharmaceutical products. Full article
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Open AccessArticle
Interpretation of Quartz Crystal Microbalance Behavior with Viscous Film Using a Mason Equivalent Circuit
Chemosensors 2021, 9(1), 9; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010009 - 02 Jan 2021
Viewed by 495
Abstract
In odor sensing based on Quartz Crystal Microbalances (QCMs), the sensing film is crucial for both sensor sensitivity and selectivity. The typical response of the QCM due to sorption is a negative frequency shift. However, in some cases, the sorption causes a positive [...] Read more.
In odor sensing based on Quartz Crystal Microbalances (QCMs), the sensing film is crucial for both sensor sensitivity and selectivity. The typical response of the QCM due to sorption is a negative frequency shift. However, in some cases, the sorption causes a positive frequency shift, and then, Sauerbrey’s equation and Kanazawa’s equation cannot be applied to this situation. We model the QCM response with a Mason equivalent circuit. The model approximates a single layer of a uniform viscous coating on the QCM. The simulation of the equation circuit shows the possibility of the positive frequency change when the sorption occurs, which is the situation we find in some of the odor sensing applications. We measured the QCM frequency and resistance using the Vector Network Analyzer (VNWA). The QCMs were coated with glycerol, PEG2000, and PEG20M. To simulate odor exposure, a microdispenser was used to deposit the water. A positive frequency shift was observed in the case of PEG2000, and a negative frequency change was obtained for PEG20M. These results can be explained by the Mason equivalent circuit, with the assumption that when the film is exposed to water, its thickness increases and its viscosity decreases. Full article
(This article belongs to the Special Issue Gustatory and Olfactory Sensing Technologies and Applications)
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Open AccessArticle
Potentiometric Carbon Quantum Dots-Based Screen-Printed Arrays for Nano-Tracing Gemifloxacin as a Model Fluoroquinolone Implicated in Antimicrobial Resistance
Chemosensors 2021, 9(1), 8; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010008 - 31 Dec 2020
Viewed by 446
Abstract
Antimicrobial resistance (AMR) is a neglected issue that poses a serious global threat to public health, causing long-term negative consequences at both humanitarian and economic levels. Herein, we report an unprecedented economic fabrication method of seven potentiometric screen-printed sensors for the ultra-trace determination [...] Read more.
Antimicrobial resistance (AMR) is a neglected issue that poses a serious global threat to public health, causing long-term negative consequences at both humanitarian and economic levels. Herein, we report an unprecedented economic fabrication method of seven potentiometric screen-printed sensors for the ultra-trace determination of gemifloxacin (GEMI) as a model of the fluoroquinolones antibiotics deeply involved in the growing AMR problem. Sensors were constructed by depositing homemade carbon ink on a recycled X-ray sheet, patterned using stencils printed with an office printer in simple, cost-effective steps requiring no sophisticated equipment. Four sensors were modified using carbon quantum dots (CQDs) synthesized from dextrose through a single-step method. Sensors exhibited a linear response in the concentration ranges 10−5–10−2 M (sensors 1, 3 and 4), 10−6–10−3 M (sensor 2) and 10−6–10−2 M (sensors 5, 6 and 7). LOD allowed tracing of the target drug at a nano-molar level down to 210 nM. GEMI was successfully determined in pharmaceutical formulations and different water samples without any pretreatment steps with satisfactory recovery (96.93–105.28% with SD values < 3). All sensors revealed a long lifetime of up to several months and are considered promising tools for monitoring water quality and efficiency of water treatment measures. Full article
(This article belongs to the Special Issue Applications of Chemosensors in Real-World Sample Analysis)
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Open AccessArticle
A Simple Visible Recognition Method for Copper Ions Using Dibenzo[b,j][1,10]Phenanthroline Scaffold as a Colorimetric Sensor
Chemosensors 2021, 9(1), 7; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010007 - 30 Dec 2020
Viewed by 409
Abstract
A dibenzo[b,j][1,10]phenanthroline (DBPhen) scaffold as a novel colorimetric Cu2+ sensor was proposed and prepared in this study. The optical properties of DBPhen were measured utilizing UV light, UV-VIS spectroscopy, and fluorescence spectroscopy. The findings denote that DBPhen exhibited a particular [...] Read more.
A dibenzo[b,j][1,10]phenanthroline (DBPhen) scaffold as a novel colorimetric Cu2+ sensor was proposed and prepared in this study. The optical properties of DBPhen were measured utilizing UV light, UV-VIS spectroscopy, and fluorescence spectroscopy. The findings denote that DBPhen exhibited a particular selectivity and great sensitivity to Cu2+ compared with other metal ions. The addition of Cu2+ in the DBPhen solution induced the color change from yellow to purple, and a new peak in the visible range (~545 nm) was observed. The detection limit of Cu2+ in the aqueous solution was calculated to be as low as 0.14 μM. Besides, the color change of the DBPhen/Cu2+ complex could be reversibly restored by adding CN. Therefore, DBPhen could have a prospective implementation as a practical colorimetric sensor to detect Cu2+ ions in environmental fields. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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Open AccessArticle
Hierarchical Porous Carbon Cobalt Nanocomposites-Based Sensor for Fructose
Chemosensors 2021, 9(1), 6; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010006 - 30 Dec 2020
Viewed by 460
Abstract
3D hierarchical graphitic carbon nanowalls encapsulating cobalt nanoparticles HPC-Co were prepared in high yield from solid-state pyrolysis of cobalt 2,2′-bipyridine chloride complex. Annealing of HPC-Co in air gave HPC-CoO, which consists of a mixture of crystallite Co3O4 nanospheres and nanorods [...] Read more.
3D hierarchical graphitic carbon nanowalls encapsulating cobalt nanoparticles HPC-Co were prepared in high yield from solid-state pyrolysis of cobalt 2,2′-bipyridine chloride complex. Annealing of HPC-Co in air gave HPC-CoO, which consists of a mixture of crystallite Co3O4 nanospheres and nanorods bursting out of mesoporous carbon. Both nanocomposites were fully characterized using SEM, TEM, BET, and powder X-ray diffraction. The elemental composition of both nanocomposites examined using SEM elemental mapping and TEM elemental mapping supports the successful doping of nitrogen. The powder X-ray diffraction studies supported the formation of hexagonal cobalt in HPC-Co, and cubic crystalline Co3O4 with cubic cobalt in HPC-CoO. HPC-Co and HPC-CoO can be used as a modified carbon electrode in cyclic voltammetry experiments for the detection of fructose with limit of detection LOD 0.5 mM. However, the single-frequency impedimetric method has a wider dynamic range of 8.0–53.0 mM and a sensitivity of 24.87 Ω mM−1 for the electrode modified with HPC-Co and 8.0–87.6 mM and a sensitivity of 1.988 Ω mM−1 for the electrode modified with HPC-CoO. The LOD values are 3 and 4 mM, respectively. The effect of interference increases in the following order: ascorbic acid, ethanol, urea, and glucose. A simple method was used with negligible interference from glucose to measure the percentage of fructose in a corn syrup sample with an HPC-CoO electrode. A specific capacitance of 47.0 F/g with 76.6% retentivity was achieved for HPC-Co and 28.2 F/g with 87.9% for HPC-CoO for 3000 charge–discharge cycles. Thus, (1) has better sensitivity and specific capacitance than (2), because (1) has a higher surface area and less agglomerated cobalt nanoparticles than (2). Full article
(This article belongs to the Special Issue Carbon Nanomaterials and Related Materials for Sensing Applications)
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Open AccessArticle
Fabrication of Zinc Oxide Nanoparticles Deposited on (3-Aminopropyl) Triethoxysilane-Treated Silicon Substrates by an Optimized Voltage-Controlled Electrophoretic Deposition and Their Application as Fluorescence-Based Sensors
Chemosensors 2021, 9(1), 5; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010005 - 29 Dec 2020
Viewed by 400
Abstract
In this study, a voltage controlled, reproducible, scalable, and cost-effective approach for depositing zinc oxide (ZnO) nanoparticles (NPs), using electrophoretic deposition (EPD) onto p-type silicon (Si) substrates, has been researched and analyzed for its feasibility with respect to electronic device fabrication and fluorescence-based [...] Read more.
In this study, a voltage controlled, reproducible, scalable, and cost-effective approach for depositing zinc oxide (ZnO) nanoparticles (NPs), using electrophoretic deposition (EPD) onto p-type silicon (Si) substrates, has been researched and analyzed for its feasibility with respect to electronic device fabrication and fluorescence-based sensors. Our work presents a detailed investigation to evaluate the influence of ZnO morphology, ZnO concentration, and the method of surface treatment applied to the underlying Si substrates, because these pertain to an optimized EPD system. It has been noted that the ZnO NP structures formed directly atop the (3-aminopropyl) triethoxysilane (APTES)-treated Si substrates were more adhesive, thus resulting in a higher yield of NPs over that of comparable depositions on bare silicon. Our observation is that smaller particle sizes of ZnO will increase the energy emission for fluorescence transmission, eliminate several peak emissions, obtain higher fluorescence quantum yield (FQY) efficiency, and require less excitation energy. The results obtained are promising in relation to the integration of EPD in the fabrication of nano biosensors, PV solar cells, nano electronic devices, and thin film transistors (TFTs), where ZnO improves the reliability, affordability, and increased sensitivity needed for the next generation of nanoscale devices and systems. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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Open AccessArticle
Potentiometric Carboxylate Sensors Based on Carbazole-Derived Acyclic and Macrocyclic Ionophores
Chemosensors 2021, 9(1), 4; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010004 - 24 Dec 2020
Viewed by 517
Abstract
Solid-contact ion-selective electrodes with carbazole-derived ionophores were prepared. They were characterized as acetate sensors, but can be used to determine a number of carboxylates. The potentiometric response characteristics (slope, detection limit, selectivity, and pH sensitivity) of sensors prepared with different membrane compositions (ionophore, [...] Read more.
Solid-contact ion-selective electrodes with carbazole-derived ionophores were prepared. They were characterized as acetate sensors, but can be used to determine a number of carboxylates. The potentiometric response characteristics (slope, detection limit, selectivity, and pH sensitivity) of sensors prepared with different membrane compositions (ionophore, ionophore concentration, anion exchanger concentration, and plasticizer) were evaluated. The results show that for the macrocyclic ionophores, a larger cavity provided better selectivity. The sensors exhibited modest selectivity for acetate but good selectivity for benzoate. The carbazole-derived ionophores effectively decreased the interference from lipophilic anions, such as bromide, nitrate, iodide, and thiocyanate. The selectivity, detection limit, and linear range were improved by choosing a suitable plasticizer and by reducing the ionophore and anion exchanger concentrations. The influence of the electrode body’s material upon the composition of the plasticized poly(vinyl chloride) membrane, and thus also upon the sensor characteristics, was also studied. The choice of materials for the electrode body significantly affected the characteristics of the sensors. Full article
(This article belongs to the Special Issue Feature Papers- Electrochemical Devices and Sensors)
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Open AccessArticle
Molecular Rotors with Aggregation-Induced Emission (AIE) as Fluorescent Probes for the Control of Polyurethane Synthesis
Chemosensors 2021, 9(1), 3; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010003 - 23 Dec 2020
Viewed by 599
Abstract
In this work, the use of fluorescent molecular rotors such as 9-(2,2-dicyanovinyl)julolidine (DCVJ) and 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl) phenyl)amino)phenyl)fumaronitrile (TPETPAFN) was proposed for the real-time monitoring of polyurethane (PU) formation in a solution of dimethylacetamide starting with 4,4′-methylenediphenyl diisocyanate (MDI) and different polyethylene glycols (PEG400 and [...] Read more.
In this work, the use of fluorescent molecular rotors such as 9-(2,2-dicyanovinyl)julolidine (DCVJ) and 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl) phenyl)amino)phenyl)fumaronitrile (TPETPAFN) was proposed for the real-time monitoring of polyurethane (PU) formation in a solution of dimethylacetamide starting with 4,4′-methylenediphenyl diisocyanate (MDI) and different polyethylene glycols (PEG400 and PEG600) as diols. Notably, relative viscosity variations were compared with fluorescence changes, recorded as a function of the polymerization progress. The agreement between these two parameters suggested the innovative use of a low-cost fluorescence detection system based on a LED/photodiode assembly directly mountable on the reaction apparatus. The general validity of the proposed experiments enabled the monitoring of polyurethane polymerization and suggested its effective applications to a variety of industrial polymers, showing viscosity enhancement during polymerization. Full article
(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)
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Open AccessArticle
Detection of Mackerel Fish Spoilage with a Gas Sensor Based on One Single SnO2 Nanowire
Chemosensors 2021, 9(1), 2; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010002 - 23 Dec 2020
Viewed by 491
Abstract
A chemosensor consisting of one single tin oxide nanowire is used to determine the freshness status of mackerel fish (Scomber scombrus) in a quick and non-invasive way. The tiny chemoresistive sensor is first tested with pure ammonia and then used to measure the [...] Read more.
A chemosensor consisting of one single tin oxide nanowire is used to determine the freshness status of mackerel fish (Scomber scombrus) in a quick and non-invasive way. The tiny chemoresistive sensor is first tested with pure ammonia and then used to measure the total volatile basic nitrogen from different samples of fish at different degrees of freshness. The sensor has proved capable of determining the freshness of a sample in few seconds compared to traditional methods such as microbial count and chromatography, which take hours. The sensor response is well correlated with the total viable count (TVC), proving that the total volatile basic nitrogen is a good way to quickly test the bacterial population in the sample. After calibrating the sensor (following the degradation of the fish during almost two days), it has been tested with random double blind samples, proving that it can well discriminate the degree of freshness of the fish preserved at different temperatures. Full article
(This article belongs to the Special Issue Nanowire-Based Sensors)
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Open AccessReview
Perylene Imide-Based Optical Chemosensors for Vapor Detection
Chemosensors 2021, 9(1), 1; https://0-doi-org.brum.beds.ac.uk/10.3390/chemosensors9010001 - 22 Dec 2020
Viewed by 494
Abstract
Perylene imide (PI) molecules and materials have been extensively studied for optical chemical sensors, particularly those based on fluorescence and colorimetric mode, taking advantage of the unique features of PIs such as structure tunability, good thermal, optical and chemical stability, strong electron affinity, [...] Read more.
Perylene imide (PI) molecules and materials have been extensively studied for optical chemical sensors, particularly those based on fluorescence and colorimetric mode, taking advantage of the unique features of PIs such as structure tunability, good thermal, optical and chemical stability, strong electron affinity, strong visible light absorption and high fluorescence quantum yield. PI-based optical chemosensors have now found broad applications in gas phase detection of chemicals, including explosives, biomarkers of some food and diseases (such as organic amines (alkylamines and aromatic amines)), benzene homologs, organic peroxides, phenols and nitroaromatics, etc. In this review, the recent research on PI-based fluorometric and colorimetric sensors, as well as array technology incorporating multiple sensors, is reviewed along with the discussion of potential applications in environment, health and public safety areas. Specifically, we discuss the molecular design and aggregate architecture of PIs in correlation with the corresponding sensor performances (including sensitivity, selectivity, response time, recovery time, reversibility, etc.). We also provide a perspective summary highlighting the great potential for future development of PIs optical chemosensors, especially in the sensor array format that will largely enhance the detection specificity in complexed environments. Full article
(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)
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