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17 pages, 6512 KiB

Open AccessArticle

Spectral Investigations of Fluorescence Tracers in Automotive and Aviation Fuels under Cryogenic Conditions

by Matthias Koegl, Jonas Vogler and Lars Zigan

Sensors 2024, 24(3), 724; https://doi.org/10.3390/s24030724 - 23 Jan 2024

Viewed by 1108

Abstract

This study investigated spectral laser-induced fluorescence signals of dyes in fuels for automotive and aerospace applications under low temperatures and cryogenic conditions down to 183 K. For this purpose, a fluorescence chamber was developed based on cooling with liquid nitrogen. The design enabled [...] Read more.

This study investigated spectral laser-induced fluorescence signals of dyes in fuels for automotive and aerospace applications under low temperatures and cryogenic conditions down to 183 K. For this purpose, a fluorescence chamber was developed based on cooling with liquid nitrogen. The design enabled a minimal inner chamber temperature of 153 K. Furthermore, the applicability of two-color LIF for liquid thermometry was evaluated under these conditions. The temperature determination was based on the temperature-sensitive fluorescence intensity ratio of the special dyes doped into the fuels determined in suitable spectral regions, which represented common bandpass filters. For this purpose, the fluorescence signals of the dye doped into the gasoline and jet fuel surrogate isooctane were tested as well as blends of isooctane and the ethanol biofuels E20 (comprising 80 vol.% isooctane and 20 vol.% ethanol), E40, and E100. Additionally, a realistic multi-component fuel Jet A-1 mixed with a suitable fluorescence dye was investigated. E100 was doped with Eosin-Y, and the remaining fuels were doped with Nile red. Temperature-dependent spectral LIF intensities were recorded in the range of 183 K–293 K, which simulate extreme environments for aerospace and automotive applications. Frozen fuel–dye mixtures cause significant extinction effects and prevent sufficient signal detection at low and cryogenic temperatures, defining the detection limit. A temperature decrease led to a spectral shift in the emission peaks of E100 doped with Eosin-Y toward shorter wavelengths, while the spectra of mixtures doped with Nile red were shifted toward longer wavelengths. The suggested bandpass filters produced the temperature-sensitive intensity ratio (the average over the temperature interval) of the dyes with the largest sensitivity for Jet A-1 (5.2%/K), followed by E100 (4.95%/K), E40 (4.07%/K), E20 (3.23%/K), and isooctane (3.07%/K), even at cryogenic temperatures. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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11 pages, 1930 KiB

Open AccessArticle

A Zinc(II) Schiff Base Complex as Fluorescent Chemosensor for the Selective and Sensitive Detection of Copper(II) in Aqueous Solution

by Ivan Pietro Oliveri, Agostino Attinà and Santo Di Bella

Sensors 2023, 23(8), 3925; https://doi.org/10.3390/s23083925 - 12 Apr 2023

Cited by 5 | Viewed by 2693

Abstract

The development of chemosensors able to detect analytes in a variety of sample matrices through a low-cost, fast, and direct approach is of current interest in food, health, industrial, and environmental fields. This contribution presents a simple approach for the selective and sensitive [...] Read more.

The development of chemosensors able to detect analytes in a variety of sample matrices through a low-cost, fast, and direct approach is of current interest in food, health, industrial, and environmental fields. This contribution presents a simple approach for the selective and sensitive detection of Cu²⁺ ions in aqueous solution based on a transmetalation process of a fluorescent substituted Zn(salmal) complex. Transmetalation is accompanied by relevant optical absorption changes and quenching of the fluorescence emission, leading to high selectivity and sensitivity of the chemosensor, with the advantage of not requiring any sample pretreatment or pH adjustment. Competitive experiments demonstrate a high selectivity of the chemosensor towards Cu²⁺ with respect to the most common metal cations as potential interferents. A limit of detection down to 0.20 μM and a dynamic linear range up to 40 μM are achieved from fluorometric data. By exploiting the fluorescence quenching upon formation of the copper(II) complex, simple paper-based sensor strips, visible to naked eyes under UV light, are used for the rapid, qualitative, and quantitative in situ detection of Cu²⁺ ions in aqueous solution over a wide concentration range, up to 10.0 mM, in specific environments, such as in industrial wastewater, where higher concentrations of Cu²⁺ ions can occur. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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13 pages, 2270 KiB

Open AccessArticle

Serotonin-Derived Fluorophore: A Novel Fluorescent Biomaterial for Copper Detection in Urine

by Mariagrazia Lettieri, Simona Scarano, Laura Caponi, Andrea Bertolini, Alessandro Saba, Pasquale Palladino and Maria Minunni

Sensors 2023, 23(6), 3030; https://doi.org/10.3390/s23063030 - 10 Mar 2023

Cited by 3 | Viewed by 1594

Abstract

We took advantage of the fluorescent features of a serotonin-derived fluorophore to develop a simple and low-cost assay for copper in urine. The quenching-based fluorescence assay linearly responds within the concentration range of clinical interest in buffer and in artificial urine, showing very [...] Read more.

We took advantage of the fluorescent features of a serotonin-derived fluorophore to develop a simple and low-cost assay for copper in urine. The quenching-based fluorescence assay linearly responds within the concentration range of clinical interest in buffer and in artificial urine, showing very good reproducibility (CV_av% = 4% and 3%) and low detection limits (16 ± 1 μg L⁻¹ and 23 ± 1 μg L⁻¹). The Cu²⁺ content was also estimated in human urine samples, showing excellent analytical performances (CV_av% = 1%), with a limit of detection of 59 ± 3 μg L⁻¹ and a limit of quantification of 97 ± 11 μg L⁻¹, which are below the reference value for a pathological Cu²⁺ concentration. The assay was successfully validated through mass spectrometry measurements. To the best of our knowledge, this is the first example of copper ion detection exploiting the fluorescence quenching of a biopolymer, offering a potential diagnostic tool for copper-dependent diseases. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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14 pages, 4515 KiB

Open AccessArticle

Sol-Gel Dipping Devices for H₂S Visualization

by Maria Strianese, Giovanni Ferrara, Viktoriia Vykhovanets, Naym Blal, Daniela Guarnieri, Alessandro Landi, Marina Lamberti, Andrea Peluso and Claudio Pellecchia

Sensors 2023, 23(4), 2023; https://doi.org/10.3390/s23042023 - 10 Feb 2023

Cited by 4 | Viewed by 1309

Abstract

In this contribution we report the synthesis and full characterization, via a combination of different spectroscopies (e.g., ¹H NMR, UV-vis, fluorescence, MALDI), of a new family of fluorescent zinc complexes with extended π-conjugated systems, with the final aim of setting up higher [...] Read more.

In this contribution we report the synthesis and full characterization, via a combination of different spectroscopies (e.g., ¹H NMR, UV-vis, fluorescence, MALDI), of a new family of fluorescent zinc complexes with extended π-conjugated systems, with the final aim of setting up higher performance H₂S sensing devices. Immobilization of the systems into a polymeric matrix for use in a solid-state portable device was also explored. The results provided proof-of-principle that the title complexes could be successfully implemented in a fast, simple and cost-effective H₂S sensing device. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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20 pages, 13292 KiB

Open AccessArticle

Discriminative ‘Turn-on’ Detection of Al³⁺ and Ga³⁺ Ions as Well as Aspartic Acid by Two Fluorescent Chemosensors

by Hina Goyal, Ibrahim Annan, Deepali Ahluwalia, Arijit Bag and Rajeev Gupta

Sensors 2023, 23(4), 1798; https://doi.org/10.3390/s23041798 - 6 Feb 2023

Cited by 8 | Viewed by 2761

Abstract

In this work, two Schiff-base-based chemosensors L1 and L2 containing electron-rich quinoline and anthracene rings were designed. L1 is AIEE active in a MeOH-H₂O solvent system while formed aggregates as confirmed by the DLS measurements and fluorescence lifetime studies. The chemosensor [...] Read more.

In this work, two Schiff-base-based chemosensors L1 and L2 containing electron-rich quinoline and anthracene rings were designed. L1 is AIEE active in a MeOH-H₂O solvent system while formed aggregates as confirmed by the DLS measurements and fluorescence lifetime studies. The chemosensor L1 was used for the sensitive, selective, and reversible ‘turn-on’ detection of Al³⁺ and Ga³⁺ ions as well as Aspartic Acid (Asp). Chemosensor L2, an isomer of L1, was able to selectively detect Ga³⁺ ion even in the presence of Al³⁺ ions and thus was able to discriminate between the two ions. The binding mode of chemosensors with analytes was substantiated through a combination of ¹H NMR spectra, mass spectra, and DFT studies. The ‘turn-on’ nature of fluorescence sensing by the two chemosensors enabled the development of colorimetric detection, filter-paper-based test strips, and polystyrene film-based detection techniques. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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15 pages, 4118 KiB

Open AccessArticle

Exploring Coumarin-Based Boron Emissive Complexes as Temperature Thermometers in Polymer-Supported Materials

by Gonçalo Pedro, Frederico Duarte, Dmitrii A. Cheptsov, Nikita Yu. Volodin, Ivan V. Ivanov, Hugo M. Santos, Jose Luis Capelo-Martinez, Cristián Cuerva, Elisabete Oliveira, Valerii F. Traven and Carlos Lodeiro

Sensors 2023, 23(3), 1689; https://doi.org/10.3390/s23031689 - 3 Feb 2023

Cited by 4 | Viewed by 2492

Abstract

Three coumarin-based boron complexes (L1, L2 and L3) were designed and successfully incorporated into polymeric matrixes for evaluation as temperature probes. The photophysical properties of the complexes were carried out in different solvents and in the solid state. In solution, compound L1 exhibited [...] Read more.

Three coumarin-based boron complexes (L1, L2 and L3) were designed and successfully incorporated into polymeric matrixes for evaluation as temperature probes. The photophysical properties of the complexes were carried out in different solvents and in the solid state. In solution, compound L1 exhibited the highest fluorescence quantum yield, 33%, with a positive solvatochromism also being observed on the absorption and emission when the polarity of the solvent increased. Additionally in the presence of anions, L1 showed a colour change from yellow to pink, followed by a quenching in the emission intensity, which is due to deprotonation with the formation of a quinone base. Absorption and fluorescence spectra of L1 were calculated at different temperatures by the DFT/B3LYP method. The decrease in fluorescence of compound L1 with an increase in temperature seems to be due to the presence of pronounced torsional vibrations of the donor and acceptor fragments relative to the single bond with C(carbonyl)-C (styrene fragment). L1, L2 and L3, through their incorporation into the polymeric matrixes, became highly emissive by aggregation. These dye@doped polymers were evaluated as temperature sensors, showing an excellent fluorescent response and reversibility after 15 cycles of heating and cooling. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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17 pages, 3769 KiB

Open AccessArticle

Fluorescence Detecting of Paraquat and Diquat Using Host–Guest Chemistry with a Fluorophore-Pendant Calix[6]arene

by Ermanno Vasca, Francesco Siano and Tonino Caruso

Sensors 2023, 23(3), 1120; https://doi.org/10.3390/s23031120 - 18 Jan 2023

Cited by 3 | Viewed by 1668

Abstract

Paraquat (PQ) and diquat (DQ), some of the most widely used herbicides in the world, both present a high mortality index after intentional exposure. In this paper, a fluorescence sensing method for PQ and DQ, based on host–guest molecular recognition, is proposed. Calix[6]arene [...] Read more.

Paraquat (PQ) and diquat (DQ), some of the most widely used herbicides in the world, both present a high mortality index after intentional exposure. In this paper, a fluorescence sensing method for PQ and DQ, based on host–guest molecular recognition, is proposed. Calix[6]arene derivatives containing anthracene or naphthalene as pendant fluorophore at their lower rim recognize DQ and PQ in hydroalcoholic solution with a broad linear response range at the μg L⁻¹ level concentration. The linear response ranges were found from 1.0 to 18 μg L⁻¹ with the detection limit of 31 ng L⁻¹ for paraquat, and from 1.0 to 44 μg L⁻¹ with the detection limit of 0.16 μg L⁻¹ for diquat. The recognition process is detected by following the decrease in the fluorescence emission consequent to complexation. The proposed quenching method has been applied to the determination of paraquat in drinking water samples. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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Review

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22 pages, 4943 KiB

Open AccessReview

Fluorescence-Based Portable Assays for Detection of Biological and Chemical Analytes

by Peuli Nath, Kazi Ridita Mahtaba and Aniruddha Ray

Sensors 2023, 23(11), 5053; https://doi.org/10.3390/s23115053 - 25 May 2023

Cited by 9 | Viewed by 5754

Abstract

Fluorescence-based detection techniques are part of an ever-expanding field and are widely used in biomedical and environmental research as a biosensing tool. These techniques have high sensitivity, selectivity, and a short response time, making them a valuable tool for developing bio-chemical assays. The [...] Read more.

Fluorescence-based detection techniques are part of an ever-expanding field and are widely used in biomedical and environmental research as a biosensing tool. These techniques have high sensitivity, selectivity, and a short response time, making them a valuable tool for developing bio-chemical assays. The endpoint of these assays is defined by changes in fluorescence signal, in terms of its intensity, lifetime, and/or shift in spectrum, which is monitored using readout devices such as microscopes, fluorometers, and cytometers. However, these devices are often bulky, expensive, and require supervision to operate, which makes them inaccessible in resource-limited settings. To address these issues, significant effort has been directed towards integrating fluorescence-based assays into miniature platforms based on papers, hydrogels, and microfluidic devices, and to couple these assays with portable readout devices like smartphones and wearable optical sensors, thereby enabling point-of-care detection of bio-chemical analytes. This review highlights some of the recently developed portable fluorescence-based assays by discussing the design of fluorescent sensor molecules, their sensing strategy, and the fabrication of point-of-care devices. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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25 pages, 5348 KiB

Open AccessReview

New Insights to Design Electrospun Fibers with Tunable Electrical Conductive–Semiconductive Properties

by William Serrano-Garcia, Irene Bonadies, Sylvia W. Thomas and Vincenzo Guarino

Sensors 2023, 23(3), 1606; https://doi.org/10.3390/s23031606 - 1 Feb 2023

Cited by 17 | Viewed by 3036

Abstract

Fiber electronics, such as those produced by the electrospinning technique, have an extensive range of applications including electrode surfaces for batteries and sensors, energy storage, electromagnetic interference shielding, antistatic coatings, catalysts, drug delivery, tissue engineering, and smart textiles. New composite materials and blends [...] Read more.

Fiber electronics, such as those produced by the electrospinning technique, have an extensive range of applications including electrode surfaces for batteries and sensors, energy storage, electromagnetic interference shielding, antistatic coatings, catalysts, drug delivery, tissue engineering, and smart textiles. New composite materials and blends from conductive–semiconductive polymers (C-SPs) offer high surface area-to-volume ratios with electrical tunability, making them suitable for use in fields including electronics, biofiltration, tissue engineering, biosensors, and “green polymers”. These materials and structures show great potential for embedded-electronics tissue engineering, active drug delivery, and smart biosensing due to their electronic transport behavior and mechanical flexibility with effective biocompatibility. Doping, processing methods, and morphologies can significantly impact the properties and performance of C-SPs and their composites. This review provides an overview of the current literature on the processing of C-SPs as nanomaterials and nanofibrous structures, mainly emphasizing the electroactive properties that make these structures suitable for various applications. Full article

(This article belongs to the Special Issue Editorial Board Members' Collection Series: Fluorescent Sensors)

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