Chemosensors

4 pages, 187 KiB

Open AccessEditorial

Polymer-Based Chemical Sensors

by José Antonio Reglero Ruiz, Saúl Vallejos, Félix Clemente García and José Miguel García

Chemosensors 2018, 6(3), 42; https://doi.org/10.3390/chemosensors6030042 - 19 Sep 2018

Cited by 4 | Viewed by 3360

Abstract

n/a Full article

(This article belongs to the Special Issue Polymers Based Chemical Sensors)

2 pages, 158 KiB

Open AccessEditorial

Fluorescent Probes for Live Cell Imaging

by Zhijie Chen and Gražvydas Lukinavičius

Chemosensors 2018, 6(3), 41; https://doi.org/10.3390/chemosensors6030041 - 19 Sep 2018

Cited by 4 | Viewed by 3923

Abstract

n/a Full article

(This article belongs to the Special Issue Fluorescent Probes for Live Cell Imaging)

45 pages, 7136 KiB

Open AccessReview

“Probe, Sample, and Instrument (PSI)”: The Hat-Trick for Fluorescence Live Cell Imaging

by Ludovic Galas, Thibault Gallavardin, Magalie Bénard, Arnaud Lehner, Damien Schapman, Alexis Lebon, Hitoshi Komuro, Patrice Lerouge, Stéphane Leleu and Xavier Franck

Chemosensors 2018, 6(3), 40; https://doi.org/10.3390/chemosensors6030040 - 13 Sep 2018

Cited by 23 | Viewed by 8023

Abstract

Cell Imaging Platforms (CIPs) are research infrastructures offering support to a number of scientific projects including the choice of adapted fluorescent probes for live cell imaging. What to detect in what type of sample and for how long is a major issue with [...] Read more.

Cell Imaging Platforms (CIPs) are research infrastructures offering support to a number of scientific projects including the choice of adapted fluorescent probes for live cell imaging. What to detect in what type of sample and for how long is a major issue with fluorescent probes and, for this, the “hat-trick” “Probe–Sample–Instrument” (PSI) has to be considered. We propose here to deal with key points usually discussed in CIPs including the properties of fluorescent organic probes, the modality of cell labeling, and the best equipment to obtain appropriate spectral, spatial, and temporal resolution. New strategies in organic synthesis and click chemistry for accessing probes with enhanced photophysical characteristics and targeting abilities will also be addressed. Finally, methods for image processing will be described to optimize exploitation of fluorescence signals. Full article

(This article belongs to the Special Issue Fluorescent Probes for Live Cell Imaging)

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8 pages, 1299 KiB

Open AccessArticle

Theoretical Investigations of the Interaction of Gaseous Pollutants Molecules with the Polyacrylonitrile Surface

by Victor Petrov and Marta Avilova

Chemosensors 2018, 6(3), 39; https://doi.org/10.3390/chemosensors6030039 - 13 Sep 2018

Cited by 3 | Viewed by 3264

Abstract

This work presents theoretical studies of the interaction of molecules of several gaseous pollutants with polyacrylonitrile (PAN) surface in the presence of a water and/or oxygen molecule. For this purpose, a PAN cluster model has been proposed by the methods of quantum chemical [...] Read more.

This work presents theoretical studies of the interaction of molecules of several gaseous pollutants with polyacrylonitrile (PAN) surface in the presence of a water and/or oxygen molecule. For this purpose, a PAN cluster model has been proposed by the methods of quantum chemical calculations and molecular modeling. The energy-favorable positions, in which the gas molecules are located relative to the surface of the PAN cluster, are determined and the thermodynamic and the following geometric parameters of the systems are calculated: “PAN cluster − oxygen molecule”, “PAN cluster − oxygen molecule − gas molecule”, “PAN cluster − water molecule − molecule of oxygen”, and “PAN cluster − a molecule of water − an oxygen molecule − a gas molecule”. It is concluded that PAN in atmospheric air in the presence of oxygen molecules is sensitive to carbon oxide (IV), sulfur (IV) oxide, chlorine, hydrogen sulfide and carbon oxide (II). In an anoxic environment, PAN films will show selective sensitivity to chlorine. The presence of water molecules in the investigated air should not affect the gas sensitivity of PAN films. Full article

(This article belongs to the Special Issue Polymers Based Chemical Sensors)

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11 pages, 2702 KiB

Open AccessArticle

Stability and Safety Assessment of Phosphorescent Oxygen Sensors for Use in Food Packaging Applications

by Caroline A. Kelly, Malco Cruz-Romero, Joseph P. Kerry and Dmitri B. Papkovsky

Chemosensors 2018, 6(3), 38; https://doi.org/10.3390/chemosensors6030038 - 6 Sep 2018

Cited by 15 | Viewed by 4842

Abstract

Five types of new solid-state oxygen sensors, four based on microporous polypropylene fabric materials and one on polyphenylene sulphide films impregnated with phosphorescent platinum(II)-benzoporphyrin dye, were tested for their stability and safety in food packaging applications. All these sensors exhibit useful optical signals [...] Read more.

Five types of new solid-state oxygen sensors, four based on microporous polypropylene fabric materials and one on polyphenylene sulphide films impregnated with phosphorescent platinum(II)-benzoporphyrin dye, were tested for their stability and safety in food packaging applications. All these sensors exhibit useful optical signals (phosphorescence lifetime readout) and working characteristics and are simpler and cheaper to produce and integrate into standard packaging materials than existing commercial sensors. When exposed to a panel of standard food simulants and upon direct contact with raw beef and chicken meat and cheddar cheese samples packaged under modified atmosphere, the sensors based on ungrafted polypropylene fabric, impregnated with PtBP dye by the swelling method, outperformed the other sensors. The sensors are also stable upon storage under normal atmospheric conditions for at least 12 months, without any significant changes in calibration. Full article

(This article belongs to the Collection Optical Chemosensors and Biosensors)

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13 pages, 2253 KiB

Open AccessArticle

From Batch to Flow Stripping Analysis with Screen-Printed Electrodes: A Possible Way to Decentralize Trace Inorganic Analysis

by Carlo Dossi, Damiano Monticelli, Andrea Pozzi and Sandro Recchia

Chemosensors 2018, 6(3), 37; https://doi.org/10.3390/chemosensors6030037 - 5 Sep 2018

Cited by 1 | Viewed by 3392

Abstract

Decentralization of on-site and in-site trace metal analysis has been a key topic over the last 30 years, owing to the increasing need for environmental protection as well as industrial and health-based field applications. In trace (and ultratrace) metal analysis, electrochemical stripping analysis [...] Read more.

Decentralization of on-site and in-site trace metal analysis has been a key topic over the last 30 years, owing to the increasing need for environmental protection as well as industrial and health-based field applications. In trace (and ultratrace) metal analysis, electrochemical stripping analysis with mercury (or bismuth) screen-printed film electrodes has shown a fast growth in popularity thanks to the good limits of detection, the ease of application in the field, and the low cost. Moreover, the availability of new wall-jet flow cells has opened the opportunity for their use in in situ industrial monitoring. The analytical figures of merit in stripping voltammetry with screen-printed electrodes (SPEs) under decentralized conditions and/or with sensor arrays are heavily affected by some analytical factors, primarily the presence of a pseudo-reference electrode, the efficiency of mass transport during the preconcentration step, and the need for external calibration. A careful model investigation of the analytical parameters for an efficient use of SPEs in decentralized conditions has been undertaken and discussed. Different instrumental approaches were investigated, comparing optimized batch conditions and flow cell operation under either continuous flow or stopped-flow sample injection. The stripping efficiency under wall-jet flow conditions was found to be high and comparable to that in batch conditions, leading to sub-ppb (μg/L) limit of detection (LOD) figures. Finally, external calibration in stripping voltammetry was studied as a viable alternative to conventional standard addition quantitation. Results showed, indeed, that external calibration was demonstrated to be reliable for quantitation of Pb and Cd in real water samples. Full article

(This article belongs to the Special Issue Printed Electroanalytical Tools for De-Centralized Applications)

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6 pages, 2075 KiB

Open AccessLetter

Gold Nanoparticle Conjugated Water Soluble Multiwall Carbon Nanotubes

by Tamoghna Bhattacharyya

Chemosensors 2018, 6(3), 36; https://doi.org/10.3390/chemosensors6030036 - 1 Sep 2018

Viewed by 3531

Abstract

The poor solubility and dispersibility of carbon nanotubes in both aqueous and organic solvents restrict their applications in biological science. Herein, a simple and cheap method for synthesizing and purification of water soluble multiwall carbon nanotubes from coal combustion fly ash and characterization [...] Read more.

The poor solubility and dispersibility of carbon nanotubes in both aqueous and organic solvents restrict their applications in biological science. Herein, a simple and cheap method for synthesizing and purification of water soluble multiwall carbon nanotubes from coal combustion fly ash and characterization of this water soluble multiwall carbon nanotubes after conjugation with gold nanoparticles has been described. Full article

(This article belongs to the Special Issue Carbon Nanotube Sensors)

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12 pages, 1656 KiB

Open AccessArticle

Increasing the Efficiency and Accuracy of Labile Cu Measurement in Wine with Screen-Printed Electrodes

by Andrew C. Clark and Nikolaos Kontoudakis

Chemosensors 2018, 6(3), 35; https://doi.org/10.3390/chemosensors6030035 - 17 Aug 2018

Cited by 4 | Viewed by 3091

Abstract

Development of oxidative and reductive flavors in wine can be influenced by the concentration and form of Cu within the wine. Electrochemical techniques have been devised to quantitate electrochemically active Cu (labile) in wine, as opposed to inactive Cu (non-labile). However, the electrochemical [...] Read more.

Development of oxidative and reductive flavors in wine can be influenced by the concentration and form of Cu within the wine. Electrochemical techniques have been devised to quantitate electrochemically active Cu (labile) in wine, as opposed to inactive Cu (non-labile). However, the electrochemical methods to measure labile Cu may be biased by the wine matrix, require lengthy calibration processes and/or unduly perturb the wine matrix during measurement. In this study, medium exchange stripping potentiometry was utilized with a thin mercury film on a screen-printed carbon electrode to provide a quantitation method that could largely overcome these limitations. The best average recoveries for 0.040 mg/L of labile Cu of 101 ± 15% (n = 12) were observed using composite calibration graphs prepared in oxidized wines and on multiple electrodes and using Pb as an internal standard. Composite calibration curves performed on different electrodes to the sample analysis were as effective in quantifying labile Cu as calibration curves performed on the same electrode as the sample. The results allow selection of a quantitation procedure that will suit the required speed and accuracy of labile Cu determination. Full article

(This article belongs to the Special Issue Printed Electroanalytical Tools for De-Centralized Applications)

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11 pages, 2663 KiB

Open AccessArticle

Nanoporous Silica-Dye Microspheres for Enhanced Colorimetric Detection of Cyclohexanone

by Zheng Li

Chemosensors 2018, 6(3), 34; https://doi.org/10.3390/chemosensors6030034 - 13 Aug 2018

Cited by 10 | Viewed by 4680

Abstract

Forensic detection of non-volatile nitro explosives poses a difficult analytical challenge. A colorimetric sensor comprising of ultrasonically prepared silica-dye microspheres was developed for the sensitive gas detection of cyclohexanone, a volatile marker of explosives 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). The silica-dye composites were [...] Read more.

Forensic detection of non-volatile nitro explosives poses a difficult analytical challenge. A colorimetric sensor comprising of ultrasonically prepared silica-dye microspheres was developed for the sensitive gas detection of cyclohexanone, a volatile marker of explosives 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). The silica-dye composites were synthesized from the hydrolysis of ultrasonically sprayed organosiloxanes under mild heating conditions (150 °C), which yielded microspherical, nanoporous structures with high surface area (~300 m²/g) for gas exposure. The sensor inks were deposited on cellulose paper and given sensitive colorimetric responses to trace the amount of cyclohexanone vapors even at sub-ppm levels, with a detection limit down to ~150 ppb. The sensor showed high chemical specificity towards cyclohexanone against humidity and other classes of common solvents, including ethanol, acetonitrile, ether, ethyl acetate, and ammonia. Paper-based colorimetric sensors with hierarchical nanostructures could represent an alternative sensing material for practical applications in the detection of explosives. Full article

(This article belongs to the Special Issue Hierarchical Nanostructures for Gas Sensors)

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10 pages, 18536 KiB

Open AccessArticle

Label-Free Biosensing Method for the Detection of a Pancreatic Cancer Biomarker Based on Dielectrophoresis Spectroscopy

by Fleming Dackson Gudagunti, Logeeshan Velmanickam, Dharmakeerthi Nawarathna and Ivan T. Lima, Jr.

Chemosensors 2018, 6(3), 33; https://doi.org/10.3390/chemosensors6030033 - 11 Aug 2018

Cited by 12 | Viewed by 5788

Abstract

We show that negative dielectrophoresis (DEP) spectroscopy is an effective transduction mechanism of a biosensor for the diagnosis and prognosis of pancreatic cancer using the biomarker CA 19-9. A substantial change in the negative DEP force applied to functionalized polystyrene microspheres (PM) was [...] Read more.

We show that negative dielectrophoresis (DEP) spectroscopy is an effective transduction mechanism of a biosensor for the diagnosis and prognosis of pancreatic cancer using the biomarker CA 19-9. A substantial change in the negative DEP force applied to functionalized polystyrene microspheres (PM) was observed with respect to both the concentration level of the pancreatic cancer biomarker CA 19-9 and the frequency of the electric field produced by a pearl shaped interdigitated gold micro-electrode. The velocity of repulsion of a set of PM functionalized to a monoclonal antibody to CA 19-9 was calculated for several concentration cutoff levels of CA 19-9, including 0 U/mL and 37 U/mL, at the frequency range from 0.5 to 2 MHz. The velocity of repulsion of the PM from the electrode was determined using a side illumination and an automated software using a real-time image processing technique that captures the Mie scattering from the PM. Since negative DEP spectroscopy is an effective transduction mechanism for the detection of the cutoff levels of CA 19-9, it has the potential to be used in the early stage diagnosis and in the prognosis of pancreatic cancer. Full article

(This article belongs to the Special Issue Label-Free Biosensors and Chemical Sensors)

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16 pages, 1295 KiB

Open AccessEditor’s ChoiceReview

From Gas Sensors to Biomimetic Artificial Noses

by Paolo Pelosi, Jiao Zhu and Wolfgang Knoll

Chemosensors 2018, 6(3), 32; https://doi.org/10.3390/chemosensors6030032 - 7 Aug 2018

Cited by 45 | Viewed by 6870

Abstract

Since the first attempts to mimic the human nose with artificial devices, a variety of sensors have been developed, ranging from simple inorganic and organic gas detectors to biosensing elements incorporating proteins of the biological olfactory system. In order to design a device [...] Read more.

Since the first attempts to mimic the human nose with artificial devices, a variety of sensors have been developed, ranging from simple inorganic and organic gas detectors to biosensing elements incorporating proteins of the biological olfactory system. In order to design a device able to mimic the human nose, two major issues still need to be addressed regarding the complexity of olfactory coding and the extreme sensitivity of the biological system. So far, only 50 of the approximately 300–400 functioning olfactory receptors have been de-orphanized, still a long way from breaking the human olfactory code. On the other hand, the exceptional sensitivity of the human nose is based on amplification mechanisms difficult to reproduce with electronic circuits, and perhaps novel approaches are required to address this issue. Here, we review the recent literature on chemical sensing both in biological systems and artificial devices, and try to establish the state-of-the-art towards the design of an electronic nose. Full article

(This article belongs to the Special Issue Electronic nose’s, Machine Olfaction and Electronic Tongue’s)

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10 pages, 1593 KiB

Open AccessArticle

Measuring Vapor and Liquid Concentrations for Binary and Ternary Systems in a Microbubble Distillation Unit via Gas Sensors

by Nada N. Abdulrazzaq, Baseem H. Al-Sabbagh, Julia M. Rees and William B. Zimmerman

Chemosensors 2018, 6(3), 31; https://doi.org/10.3390/chemosensors6030031 - 3 Aug 2018

Cited by 2 | Viewed by 4580

Abstract

A cost effective, fast, and accurate technique was needed to measure the vapor composition of a binary system (ethanol-water) and also that of a liquid composition in a ternary system (acetic acid-acetol–water) in a microbubble distillation unit. Cheap TGS-series gas sensors were used [...] Read more.

A cost effective, fast, and accurate technique was needed to measure the vapor composition of a binary system (ethanol-water) and also that of a liquid composition in a ternary system (acetic acid-acetol–water) in a microbubble distillation unit. Cheap TGS-series gas sensors were used for this purpose with both calibrations and measurements carried out in a specially designed chamber. A single parameter polynomial regression was fitted to the binary system, and a two parameter polynomial with an interaction term was fitted to the ternary system. The correlation coefficient, R-squared, was found to be greater than 0.99 for both systems, thus validating the implementation of this novel sensor. Full article

(This article belongs to the Special Issue Electronic nose’s, Machine Olfaction and Electronic Tongue’s)

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15 pages, 1930 KiB

Open AccessArticle

Broad-Range Hydrogel-Based pH Sensor with Capacitive Readout Manufactured on a Flexible Substrate

by Krister Hammarling, Magnus Engholm, Henrik Andersson, Mats Sandberg and Hans-Erik Nilsson

Chemosensors 2018, 6(3), 30; https://doi.org/10.3390/chemosensors6030030 - 25 Jul 2018

Cited by 11 | Viewed by 5196

Abstract

Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, [...] Read more.

Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, there is a need for new sensors and sensor systems that suits these type of measurements. However, the diversity of sensors suitable for low, battery powered- and large area sensor systems are limited. We have manufactured and characterized a flexible pH sensor using laser processing and blade coating techniques that is able to measure pH between 2.94 and 11.80. The sensor consists of an interdigital capacitance with a pH sensitive hydrogel coating. Thin sensors can reach 95% of their final value value within 3 min, and are stable after 4 min. Good repeatability was achieved in regard to cycling of the sensor with different pH and multiple measurements from dry state. We have also studied the relation between an interdigital capacitance penetration depth and hydrogels expansion. We believe that our passive sensor is suitable to be used in low power and large area sensor networks. Full article

(This article belongs to the Special Issue Thin Film Based Sensors)

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20 pages, 284 KiB

Open AccessReview

Application of Fecal Volatile Organic Compound Analysis in Clinical Practice: Current State and Future Perspectives

by Sofia El Manouni el Hassani, Daniel J. C. Berkhout, Sofie Bosch, Marc A. Benninga, Nanne K. H. De Boer and Tim G. J. De Meij

Chemosensors 2018, 6(3), 29; https://doi.org/10.3390/chemosensors6030029 - 23 Jul 2018

Cited by 15 | Viewed by 5565

Abstract

Increasing interest is noticed in the potential of volatile organic compound (VOC) analysis as non-invasive diagnostic biomarker in clinical medical practice. The spectrum of VOCs, originating from (patho)physiological metabolic processes in the human body and detectable in bodily excrements, such as exhaled breath, [...] Read more.

Increasing interest is noticed in the potential of volatile organic compound (VOC) analysis as non-invasive diagnostic biomarker in clinical medical practice. The spectrum of VOCs, originating from (patho)physiological metabolic processes in the human body and detectable in bodily excrements, such as exhaled breath, urine and feces, harbors a magnificent source of information. Thus far, the majority of studies have focused on VOC analysis in exhaled breath, aiming at identification of disease-specific VOC profiles. Recently, an increasing number of studies have evaluated the usability of VOC present in the headspace of feces in the diagnostic work-up of a wide range of gastrointestinal diseases. Promising results have been demonstrated particularly in those diseases in which microbiota alterations are considered to play a significant etiological role, such as colorectal carcinoma, inflammatory bowel disease, irritable bowel syndrome, celiac disease and infectious bowel diseases. In addition, fecal VOC analysis seems to have potential as a diagnostic biomarker for extra-intestinal diseases, including bronchopulmonary dysplasia and sepsis. Different methods for VOC analysis have been used in medical studies, such as gas-chromatography mass spectrometry, selected-ion flow tube-mass spectrometry, ion-mobility spectrometry, and electronic nose devices. In this review, the available literature on the potential of fecal VOCs as diagnostic biomarker, including an overview of relevant VOC detection techniques, is discussed. In addition, future hurdles, which need to be taken prior to implementation of VOC analysis in daily clinical practice, are outlined. Full article

(This article belongs to the Special Issue Electronic nose’s, Machine Olfaction and Electronic Tongue’s)

25 pages, 948 KiB

Open AccessReview

Honey Evaluation Using Electronic Tongues: An Overview

by Ana C. A. Veloso, Mara E. B. C. Sousa, Leticia Estevinho, Luís G. Dias and António M. Peres

Chemosensors 2018, 6(3), 28; https://doi.org/10.3390/chemosensors6030028 - 19 Jul 2018

Cited by 23 | Viewed by 5860

Abstract

Honey-rich composition in biologically active compounds makes honey a food products highly appreciated due to the nutritional and healthy properties. Food-manufacturing is very prone to different types of adulterations and fraudulent labelling making it urgent to establish accurate, fast and cost-effective analytical techniques [...] Read more.

Honey-rich composition in biologically active compounds makes honey a food products highly appreciated due to the nutritional and healthy properties. Food-manufacturing is very prone to different types of adulterations and fraudulent labelling making it urgent to establish accurate, fast and cost-effective analytical techniques for honey assessment. In addition to the classical techniques (e.g., physicochemical analysis, microscopy, chromatography, immunoassay, DNA metabarcoding, spectroscopy), electrochemical based-sensor devices have arisen as reliable and green techniques for food analysis including honey evaluation, allowing in-situ and on-line assessment, being a user-friendly procedure not requiring high technical expertise. In this work, the use of electronic tongues, also known as taste sensor devices, for honey authenticity and assessment is reviewed. Also, the versatility of electronic tongues to qualitative (e.g., botanical and/or geographical origin assessment as well as detection of adulteration) and quantitative (e.g., assessment of adulterants levels, determination of flavonoids levels or antibiotics and insecticides residues, flavonoids) honey analysis is shown. The review is mainly focused on the research outputs reported during the last decade aiming to demonstrate the potentialities of potentiometric and voltammetric multi-sensor devices, pointing out their main advantages and present and future challenges for becoming a practical quality analytical tool at industrial and commercial levels. Full article

(This article belongs to the Special Issue Electronic nose’s, Machine Olfaction and Electronic Tongue’s)

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12 pages, 10675 KiB

Open AccessArticle

Characterization of a Novel Polypyrrole (PPy) Conductive Polymer Coated Patterned Vertical CNT (pvCNT) Dry ECG Electrode

by Mohammad Abu-Saude and Bashir I. Morshed

Chemosensors 2018, 6(3), 27; https://doi.org/10.3390/chemosensors6030027 - 17 Jul 2018

Cited by 21 | Viewed by 7882

Abstract

Conventional electrode-based technologies, such as the electrocardiogram (ECG), capture physiological signals using an electrolyte solution or gel that evaporates shortly after exposure, resulting in a decrease in the quality of the signal. Previously, we reported a novel dry impedimetric electrode using patterned vertically-aligned [...] Read more.

Conventional electrode-based technologies, such as the electrocardiogram (ECG), capture physiological signals using an electrolyte solution or gel that evaporates shortly after exposure, resulting in a decrease in the quality of the signal. Previously, we reported a novel dry impedimetric electrode using patterned vertically-aligned Carbon NanoTubes (pvCNT) for biopotential measurement applications. The mechanical adhesion strength of the pvCNT electrode to the substrate was weak, hence, we have improved this electrode using a thin coating of the conductive polymer polypyrrole (PPy) that strengthens its mechanical properties. Multiwall CNTs were grown vertically on a circular stainless-steel disc (⌀ = 10 mm) substrate of 50 µm thickness forming patterned pillars on a square base (100 µm × 100 µm) with an inter-pillar spacing of 200 µm and height up to 1.5 mm. The PPy coating procedure involves applying 10 µL of PPy mixed with 70% ethyl alcohol solution and rapid drying at 300 °C using a hot air gun at a distance of 10 cm. A comparative study demonstrated that the coated pvCNT had higher impedance compared to a non-coated pvCNT but lower impedance compared to the standard gel electrode. The PPy-coated pvCNT had comparable signal capture quality but stronger mechanical adhesion to the substrate. Full article

(This article belongs to the Special Issue Carbon Nanotube Sensors)

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11 pages, 2646 KiB

Open AccessArticle

Lifetime and Fluorescence Quantum Yield of Two Fluorescein-Amino Acid-Based Compounds in Different Organic Solvents and Gold Colloidal Suspensions

by Viviane Pilla, Augusto C. Gonçalves, Alcindo A. Dos Santos and Carlos Lodeiro

Chemosensors 2018, 6(3), 26; https://doi.org/10.3390/chemosensors6030026 - 30 Jun 2018

Cited by 13 | Viewed by 7647

Abstract

Fluorescein and its derivatives are yellowish-green emitting dyes with outstanding potential in advanced molecular probes for different applications. In this work, two fluorescent compounds containing fluorescein and an amino acid residue (compounds 1 and 2) were photophysically explored. Compounds 1 and 2 [...] Read more.

Fluorescein and its derivatives are yellowish-green emitting dyes with outstanding potential in advanced molecular probes for different applications. In this work, two fluorescent compounds containing fluorescein and an amino acid residue (compounds 1 and 2) were photophysically explored. Compounds 1 and 2 were previously synthesized via ester linkage between fluorescein ethyl ester and Boc-ser (TMS)-OH or Boc-cys(4-methyl benzyl)-OH. Studies on the time-resolved fluorescence lifetime and relative fluorescence quantum yield (φ) were performed for 1 and 2 diluted in acetonitrile, ethanol, dimethyl sulfoxide, and tetrahydrofuran solvents. The discussion considered the dielectric constants of the studied solvents (range between 7.5 and 47.2) and the photophysical parameters. The results of the lifetime and φ were compared with those obtained for compounds 1, 2 and fluorescein without an amino acid residue in alkaline aqueous solutions. Moreover, as a preliminary result compound 2 (S-cysteine) was tested in the presence of gold nanoparticles as an aggregation colorimetric probe. Full article

(This article belongs to the Special Issue New insides in Fluorescent and Colorimetric Probes)

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7 pages, 811 KiB

Open AccessReview

Potentiometric Biosensing Applications of Graphene Electrodes with Stabilized Polymer Lipid Membranes

by Georgia-Paraskevi Nikoleli, Dimitrios P. Nikolelis, Christina G. Siontorou, Marianna-Thalia Nikolelis and Stephanos Karapetis

Chemosensors 2018, 6(3), 25; https://doi.org/10.3390/chemosensors6030025 - 28 Jun 2018

Cited by 2 | Viewed by 3475

Abstract

This review provides information and details about the fabrication of biosensors composed of lipid membranes that can be used to rapidly detect toxic compounds in food, environmental pollutants, and analytes of clinical interest. Biosensors based on polymeric lipid membranes have been used to [...] Read more.

This review provides information and details about the fabrication of biosensors composed of lipid membranes that can be used to rapidly detect toxic compounds in food, environmental pollutants, and analytes of clinical interest. Biosensors based on polymeric lipid membranes have been used to rapidly detect a wide range of these analytes, offering several advantages including fast response times, high sensitivity and selectivity, portability for field applications, and small size. A description of the construction of these devices and their applications for the rapid detection of toxic substances in food, environmental pollutants, and analytes of clinical interest is provided in this review. Full article

(This article belongs to the Special Issue Ion Selective Electrodes and Interfaces: Fundamental, Education and Applications)

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Chemosensors, Volume 6, Issue 3 (September 2018) – 18 articles

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