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A special issue of Chemosensors (ISSN 2227-9040). This special issue belongs to the section "Optical Chemical Sensors".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 29249

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Prof. Dr. Guo-Hui Pan

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State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dong Nanhu Road, Changchun 130033, China
Interests: optical sensor; fluorescent probe; rare earth luminescence; quantum dots; opo-electronic device

Prof. Dr. Hongshang Peng

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Optoelectronics Research Center, College of Science, Minzu University of China, Beijing 100081, China
Interests: luminescent oxygen sensor; photodynamic thereapy; quantum dots
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Prof. Dr. Biao Dong

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State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
Interests: optical properties of rare earth doped nanomaterials; circulating tumor cells/DNA sensing; fluorescence/electrochemical tumor markers; VOC gas sensor
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The development of activatable sensors for the recognition and detection of environmentally and biologically important species led to a major progression in science and technology and facilitated economic growth. Scientists worked for years to develop sensors with a rapid response, high selectivity and supersensitivity. Among various sensing techniques, fluorescence sensing (fluorometry), referring to chemosensors based on fluorescence spectroscopy, has specific advantages in term of simplicity, versatility and easy manipulation. Fluorescence sensing can achieve the detection of specific analytes of cations, anions, and biomolecules; the imaging of cell and biological tissue; the measurement of physical and industrial parameters of temperature, pH and humidity; and even the probing of local microstructures of materials, etc.

The luminescent species involved in fluorescence sensing could be small-molecule fluorophores, organocomplexes (organometallics, lanthanide chelates), polymers, nanoparticles (quantum dots, lanthanide or transition-metal-doped nanocrystals), nanostructures, and even bulk solids. The configuration of the fluorescent sensors can consist of molecules, fine particles or large surfaces/interfaces of materials/devices. The indicators adopted for sensing can range from spectral position, fluorescence intensity, fluorescence intensity ratio, band shape, band width to lifetime, etc. The excited processes involved in the sensitive evolution of fluorescence signals can derive from intramolecular charge transfer (ICT), photoinduced electron transfer (PET), Förster resonance energy transfer (FRET), excited-state intramolecular proton transfer (ESIPT) and chelation-induced enhanced fluorescence (CHEF).

Recently, there has been rapid progress in fluorescence sensing; some new and popular topics are emerging. Here, we propose a Special Issue to highlight “Advances in Fluorescence Sensing”, which encompasses a broad range of fluorescent sensors and their applications, including ions/molecules sensing, pH and humidity sensing, optical thermometry, bioimaging and diagnostics applications, etc. It is anticipated that this Special Issue will provide a forum for mutual communication among researchers in the fields of chemistry, materials science, spectroscopy, and biology.

Prof. Dr. Guo-Hui Pan
Prof. Dr. Hongshang Peng
Prof. Dr. Biao Dong
Guest Editors

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Keywords

fluorescence sensing
organic dyes
luminescent nanoparticles
luminescent nanostructures
ions sensing
molecules sensing
pH sensing
optical thermometry
fluorescence imaging
luminescnent protein

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Published Papers (11 papers)

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22 pages, 7653 KiB

Open AccessArticle

A Facile Synthetic Approach toward Obtaining N-Doped Carbon Quantum Dots from Citric Acid and Amino Acids, and Their Application in Selective Detection of Fe(III) Ions

by Silvija Šafranko, Kristina Janđel, Monika Kovačević, Anamarija Stanković, Maja Dutour Sikirić, Šimun Mandić, Aleksandar Széchenyi, Ljubica Glavaš Obrovac, Marijana Leventić, Ivica Strelec, Krunoslav Aladić and Stela Jokić

Chemosensors 2023, 11(4), 205; https://doi.org/10.3390/chemosensors11040205 - 24 Mar 2023

Cited by 7 | Viewed by 3260

Abstract

This work reports the preparation of amino acid-functionalized CQDs from citric acid by facile hydrothermal synthesis. The prepared N-doped CQDs exhibited excellent optical, physical, and chemical properties, and the differences were observed among the six different amino acids used as nitrogen dopants (Leu, Trp, Lys, Arg, Ala, His). Compared to the blank sample (without the addition of amino acids), N-doped CQDs have shown significantly higher quantum yield, also demonstrating the potential in metal ion sensing. The highest quantum yield of 36.45%, with a peak excitation/emission of 340/406 nm, was achieved using citric acid and amino acid Leu (CQD@Leu), treated at temperature of 180 °C during 9 h. The prepared samples were investigated toward metal ion selectivity (Ca²⁺, Cu²⁺, Fe³⁺, K⁺, Hg²⁺, Mg²⁺, Al³⁺, Mn²⁺, and Na⁺), and the CQD@Leu showed a selective and sensitive response upon the addition of Fe³⁺ ions. Therefore, CQD@Leu was selected for further investigation in Fe³⁺ detection in the model system and real well water samples. A developed model was described by a logistic function with a good coefficient of determination of R² = 0.9982, while the linear range was determined in the concentration range from 0.3 mol dm⁻³ to 30 mol dm⁻³, with a determined limit of detection of LOD = 1.77 ± 0.01 mol dm⁻³ and limit of quantification of LOQ = 5.89 ± 0.04 mol dm⁻³. Furthermore, the results of the in vitro cytotoxicity test (MTT) with normal and tumor cell lines (MRC-5, HeLa, NCI-H358, and CaCo-2) clearly demonstrate the excellent biocompatibility of CQD@Leu. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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16 pages, 4154 KiB

Open AccessArticle

Macrocyclic Compounds Comprising Tris(3-Aminopropyl)Amine Units and Fluorophore Moieties: Synthesis and Spectroscopic Studies in the Presence of Metal Salts

by Daria S. Kuliukhina, Nataliya M. Chernichenko, Alexei D. Averin, Anton S. Abel, Olga A. Maloshitskaya and Irina P. Beletskaya

Chemosensors 2023, 11(3), 186; https://doi.org/10.3390/chemosensors11030186 - 10 Mar 2023

Cited by 1 | Viewed by 1683

Abstract

The synthesis of a variety of polyazamacrocyclic compounds comprising structural units of tris(3-aminopropyl)amine (TRPN) and oxadiamines, decorated with one or two fluorophore groups (dansyl or quinoline) at different nitrogen atoms, was carried out using Pd(0)-catalyzed amination. The dependence of the yields of the macrocycles on the synthetic path was observed. The spectrophotometric and fluorescent properties of the target compounds were studied, and their coordination with metal cations using UV–vis, fluorescence spectra as well as NMR titration was investigated. The stoichiometry and binding constants of several complexes with Cu(II), Zn(II), Cd(II), Pb(II) and Hg(II) were established. Three of the six studied macrocycles can be judged as prospective detectors of Zn(II) cations due to the substantial enhancement of fluorescence. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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16 pages, 3438 KiB

Open AccessArticle

New ICT-Based Ratiometric Two-Photon near Infrared Probe for Imaging Tyrosinase in Living Cells, Tissues, and Whole Organisms

by Javier Valverde-Pozo, Jose Manuel Paredes, Maria Eugenia García-Rubiño, Thomas J. Widmann, Carmen Griñan-Lison, Silvia Lobon-Moles, Juan Antonio Marchal, Jose Maria Alvarez-Pez and Eva Maria Talavera

Chemosensors 2023, 11(2), 145; https://doi.org/10.3390/chemosensors11020145 - 16 Feb 2023

Viewed by 2496

Abstract

Melanoma is a type of highly malignant and metastatic skin cancer. In situ molecular imaging of endogenous levels of the melanoma biomarker tyrosinase (TYR) may decrease the likelihood of mortality. In this study, we proposed the weakly fluorescent probe 1-(4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenyl)-3-(4-hydroxybenzyl)urea (DCM-HBU), which releases a strong red-shifted fluorescent signal after a TYR-mediated oxidation followed by hydrolysis of the urea linkage. The large Stokes shift of the dye is owed to the recovery of the intramolecular charge transfer (ICT) effect. The resulting probe derivate shows a highly ratiometric fluorescence output. Furthermore, the simultaneous excitation by two near-infrared (NIR) photons of the released derivative of dicyanomethylene-4H-pyran (DCM-NH₂) fluorophore could avoid the usual drawbacks, such as cellular absorption, autofluorescence, and light scattering, due to an usually short wavelength of the excitation light on biological systems, resulting in images with deeper tissue penetration. In addition, the probe is useful for the quantitative sensing of TYR activity in vivo, as demonstrated in zebrafish larvae. This new ratiometric two-photon NIR fluorescent probe is expected to be useful for the accurate detection of TYR in complex biosystems at greater depths than other one-photon excited fluorescent probes. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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14 pages, 5289 KiB

Open AccessArticle

Preparation and Photoluminescent Properties of Tb³⁺-Doped Lu₂W₃O₁₂ and Lu₂Mo₃O₁₂ Green Phosphors

by Nihui Huang, Guojun Lu, Bihai Bai, Zijun Chen, Min Zhang, Yuechan Li, Chunyan Cao and An Xie

Chemosensors 2022, 10(12), 533; https://doi.org/10.3390/chemosensors10120533 - 14 Dec 2022

Cited by 7 | Viewed by 1700

Abstract

Tungstate and molybdate phosphors have received great attention for their excellent photoluminescent properties and thermal stabilities. In the article, Tb³⁺-activated tungstate and molybdate green phosphors were prepared by a solid-state reaction method at different caline temperatures and were compared and studied. The crystal structures and the morphologies of samples were characterized by X-ray diffraction (XRD) patterns and field emission scanning electron microscopy (FE-SEM) images. The energy-dispersive spectra (EDS) proved the compositions of the prepared samples. The photoluminescence (PL) spectra showed that the PL excitation spectra of Tb³⁺-doped Lu₂W₃O₁₂ and Lu₂Mo₃O₁₂ green phosphors consisted of a broad and strong charge transfer band (CTB) and 4f–5d transitions of Tb³⁺ in the ultraviolet (UV) wavelength range and some narrowed excitation peaks from the 4f–4f transition of Tb³⁺ in the near ultraviolet (NUV) wavelength region. The PL emission spectra of the phosphors exhibited the characteristic green emissions owing to the ⁵D₄→⁷F₅ transition of Tb³⁺ located at about 547 nm. The values of energy gap E_g were calculated based on the diffuse reflection spectra (DRS). The measuring temperature-dependent PL spectra illustrated the thermal stabilities of phosphors. The Tb³⁺-doped Lu₂Mo₃O₁₂ phosphor presented normal thermal quenching phenomena and the values of the thermal activation energy E_a were calculated based on the measuring temperature dependent PL emission spectra. The Tb³⁺-doped Lu₂W₃O₁₂ phosphor exhibited abnormal thermal enhancing CTB excitation intensity at about 170 °C. Furthermore, the PL decay curves suggested that the lifetime corresponding to the ⁵D₄ level of Tb³⁺ in the Lu₂W₃O₁₂ host lattice was longer than that in the Lu₂Mo₃O₁₂ host lattice. Compared the Tb³⁺-doped Lu₂Mo₃O₁₂ phosphor, the Tb³⁺-doped Lu₂W₃O₁₂ phosphor has shown potential as an application in temperature sensors. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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19 pages, 5129 KiB

Open AccessArticle

Microstructure and Photoluminescence of ZrTiO₄:Eu³⁺ Phosphors: Host-Sensitized Energy Transfer and Optical Thermometry

by Anheng Gu, Guo-Hui Pan, Huajun Wu, Liangliang Zhang, Ligong Zhang, Hao Wu and Jiahua Zhang

Chemosensors 2022, 10(12), 527; https://doi.org/10.3390/chemosensors10120527 - 12 Dec 2022

Cited by 5 | Viewed by 2261

Abstract

Orthorhombic ZrTiO₄ is an attractive dielectric material; its optical properties are, however, less known. In this paper, we reported on the microstructure and luminescence studies of pristine ZrTiO₄ and Eu³⁺-doped ZrTiO₄ phosphors. The results indicated that two types of TiO₆ octahedra, the isolated/ localized and coupled/delocalized, coexisted in host matrix. Eu³⁺ doping could induce oxygen vacancy defect states located below the bottom of the conduction band. Pristine ZrTiO₄ showed bright yellow luminescence via STEs recombination at defects sites at low temperatures, but significant thermal quenching occurred due to STEs migration to quenching centers at elevated temperatures. Effective host sensitized energy transfer to Eu³⁺ was observed in ZrTiO₄:Eu³⁺ phosphors and yielded the red characteristic emissions of Eu³⁺. Anomalous STEs luminescence enhancement and spectral blue-shift in the excitation spectra with higher Eu^{3 +} concentration appeared and were explained by considering three factors: competitive absorption between electron transitions from the top of the valence band to the defect states and host conduction band, Eu³⁺ doping driving the production of more isolated TiO₆ octahedra, and energy back-transfer from Eu³⁺ activators to other titanate groups. On the basis of the dual-emitting combination strategy involving host STEs and Eu³⁺ luminescence, ZrTiO₄:Eu³⁺ phosphors were demonstrated to be ratiometric self-referencing optical thermometric materials, with a working range of 153–313 K and a maxima of relative sensitivity to ~1.1% K⁻¹ at 243 K. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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13 pages, 3672 KiB

Open AccessArticle

New Quantum-Dot-Based Fluorescent Immunosensor for Cancer Biomarker Detection

by Mariana P. Sousa, Ana Margarida L. Piloto, Ana Cláudia Pereira, Fernando C. Schmitt, Ruben Fernandes and Felismina T. C. Moreira

Chemosensors 2022, 10(12), 518; https://doi.org/10.3390/chemosensors10120518 - 7 Dec 2022

Cited by 6 | Viewed by 2632

Abstract

Cancer antigen 15-3 (CA 15-3) is a biomarker for breast cancer used to monitor response to treatments and disease recurrence. The present work demonstrates the preparation and application of a fluorescent biosensor for ultrasensitive detection of the cancer antigen CA 15-3 protein tumor marker using mercaptopropionic-acid-functionalized cadmium telluride (CdTe@MPA) quantum dots (QDs) conjugated with CA 15-3 antibodies. First, the QDs were synthesized by the hydrothermal route, resulting in spherical nanoparticles up to 3.50 nm in diameter. Subsequently, the QD conjugates were characterized by Fourier transform infrared spectroscopy (FTIR), UV absorption, and fluorescence. The interaction between the conjugates and the protein was studied by fluorescence spectroscopy in buffer and in 10-fold diluted commercial human serum. Calibration in spiked serum samples gave a detection limit of 0.027 U/mL, 1000-fold lower than the clinical limit for CA 15-3 (25 U/mL to 30 U/mL), indicating that this is an ultrasensitive technique. In addition, a rapid response was obtained within 10 min. The biosensor was selective in the presence of the interfering serum proteins BSA, CEA, and CA-125, with a maximum interference of 2% for BSA. The percent recovery was close to 100% with maximum relative standard deviation (RSD%) values of 1.56. Overall, the developed CA 15-3 biosensor provides a simple and sensitive method for ultrasensitive monitoring of breast cancer, as well as the ability to detect other molecules of interest in human serum matrices. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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16 pages, 2804 KiB

Open AccessArticle

Novel Hydrazone Chromophore Sensor for Metallochromic Determination of Cadmium Ions

by Islam El-Nagar, Ahmed M. Youssef, A. A. Abd El-Hakim, El-Refaie Kenawy, Hamada S. A. Mandour and Tawfik A. Khattab

Chemosensors 2022, 10(11), 451; https://doi.org/10.3390/chemosensors10110451 - 1 Nov 2022

Cited by 6 | Viewed by 1998

Abstract

For the detection of Cd(II) in aquatic media, a novel dicyanomethylene dihydrofuran hydrazone(DCDHFH)-based colorimetric chemosensor was developed. DCDHFH was prepared by an azo-coupling process involving the diazonium chloride of 2, 4-dichloroaniline and a dicyanomethylene dihydrofuran heterocyclic moiety bearing an active methyl group. The DCDHFH chromophore showed strong solvatochromism depending on solvent polarity due to electronic delocalization. The pH sensory effects of the DCDHFH chromophore were also explored. DCDHFH could be used to identify Cd(II) in the presence of other competitive metals, as indicated by variations in color and absorbance spectra. In the presence of cadmium ions, the synthesized DCDHFH probe with hydrazone recognition moiety exhibited a significant sensitivity and selectivity to cadmium ions at the ppm concentration level (10–250 ppm). A DCDHFH-immobilized paper test strip was also prepared and effectively used for the detection of cadmium in aqueous media at various concentrations. According to CIE Lab’s criteria, colorimetric strength (K/S), and the UV–Vis absorbance spectra, the cadmium detection abilities of the DCDHFH-immobilized paper strips were evaluated. The optimal pH range for the determination of Cd(II) was monitored in the area of 5.5–6.3, with a fast chromogenic change from yellow to red relying on the Cd(II) concentration. The deposition of dicyanomethylene dihydrofuran hydrazone onto the paper strip’s surface was studied by scanning electron microscopy (SEM). Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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14 pages, 4752 KiB

Open AccessArticle

Conjugated Polymer Nanoparticles Based on Anthracene and Tetraphenylethene for Nitroaromatics Detection in Aqueous Phase

by Tianwen Ouyang, Xue Guo, Qihao Cui, Wei Zhang, Wenyue Dong and Teng Fei

Chemosensors 2022, 10(9), 366; https://doi.org/10.3390/chemosensors10090366 - 14 Sep 2022

Cited by 6 | Viewed by 2157

Abstract

The sensitive and selective detection of nitroaromatic explosives is of great significance to national security and human health. Herein, the novel linear polymer l-PAnTPE and cross-linked polymer PAnTPE nanoparticles based on anthracene and tetraphenylethene groups were designed and successfully synthesized via Suzuki-miniemulsion polymerization. The particle sizes of the polymers are around 73 nm, making them well dispersible in water. The cross-linked polymer PAnTPE exhibits porous structure, which is beneficial for the diffusion/adsorption of analytes. The fluorescence sensing towards nitroaromatics was performed in the aqueous phase, and l-PAnTPE and PAnTPE nanoparticles showed different quenching degree towards different nitroaromatics. Among them, the quenching constant K_SV values of l-PAnTPE and PAnTPE towards 2,4,6-trinitrophenol (TNP) reach 1.8 × 10⁴ M⁻¹ and 4.0 × 10⁴ M⁻¹, respectively, which are 1–2 orders of magnitude higher than other nitroaromatic explosives, thus demonstrating the high sensitivity and selectivity of TNP detection in the aqueous phase. The sensing mechanism was further discussed to clarify this phenomenon by analyzing UV–Vis absorption, excitation, fluorescence spectra, cyclic voltammograms and fluorescence decay measurements. In addition, the paper strips tests exhibit that l-PAnTPE and PAnTPE have great potential in the application of fast, low-cost and on-site nitroaromatics detection. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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21 pages, 3630 KiB

Open AccessArticle

In Vitro and In Silico Evaluation of Indole-Bearing Squaraine Dyes as Potential Human Serum Albumin Fluorescent Probes

by Margarida A. Sousa, Eurico Lima, Octávio Ferreira, Renato E. Boto, Paulo Almeida and Lucinda V. Reis

Chemosensors 2022, 10(8), 314; https://doi.org/10.3390/chemosensors10080314 - 6 Aug 2022

Cited by 3 | Viewed by 2445

Abstract

The quantitative determination of proteins is an important parameter in biochemistry, biotechnology and immunodiagnostics, and the importance of serum albumin in clinical diagnosis should be highlighted, given that alterations in its concentration are generally associated with certain diseases. As possible probes for this purpose, squaraine dyes have been arousing the interest of many researchers due to their unique properties, such as absorption in the visible spectra, moderate relative fluorescence quantum yields and increased fluorescence intensity after non-covalent binding to specific ligands. In this work, five squaraine dyes, four of which have never been reported in the literature, were characterized and evaluated in vitro and in silico concerning their potential application as fluorescent probes for human serum albumin detection. After interaction with the protein, the fluorescence intensity increased from 12 to 41 times, depending on the dye under study. High sensitivity (1.0 × 10⁵–5.4 × 10⁵ nM), low detection limits (168–352 nM) and moderate quantitation limits (560–1172 nM) were obtained, proving the efficiency of the method. In addition, moderate-to-excellent selectivity was observed compared to γ-globulin proteins. Molecular docking suggests that the dyes interact more effectively with the Sudlow site I, and binding energies have been markedly higher than those of warfarin, a molecule known to bind to this site specifically. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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13 pages, 1810 KiB

Open AccessEditor’s ChoiceArticle

UV-Excited Fluorescence as a Basis for the In-Situ Identification of Natural Binders in Historical Painting: A Critical Study on Model Samples

by Margherita Longoni, Ester Sara Cacciola and Silvia Bruni

Chemosensors 2022, 10(7), 256; https://doi.org/10.3390/chemosensors10070256 - 1 Jul 2022

Cited by 4 | Viewed by 2945

Abstract

The fluorescence emission by aged organic binders used in painting is a well-known phenomenon. Several literature studies were devoted to its investigation, both on pure binders and on their mixtures with some pigments. Nevertheless, a systematic study about the real possibility of exploiting such a phenomenon for the non-invasive identification of binders in ancient paintings is still lacking. In the present work, a prototype portable fluorimeter was used to analyze a significant number of model painting samples containing different binders (drying oils, egg yolk, milk, animal glue, and gum Arabic) mixed with various pigments having different hues. The model samples were naturally aged in a period ranging from fifteen to one year. The effects on the spectral pattern due to the different binders, the recipes used to prepare them, and the pigments mixed with them were examined. The fluorescence spectra were corrected for the absorption of the emitted radiation due to the pigments. Finally, the corrected spectra were treated by principal component analysis to determine if the possibility of distinguishing at least the most fluorescent and common binders, i.e., drying oils and egg, existed. It was shown that, even if the technique cannot be effectively applied in the case of mixed or superimposed binders, it allows to put forward at least a preliminary hypothesis when pure binders are used. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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38 pages, 31045 KiB

Open AccessReview

Self-Immobilizing Quinone Methides for the Fluorescent Sensing of Enzyme Activity

by Dóra Kern and Attila Kormos

Chemosensors 2023, 11(3), 155; https://doi.org/10.3390/chemosensors11030155 - 23 Feb 2023

Cited by 5 | Viewed by 3055

Abstract

Gaining insight into biological processes relies on sensitive analytical techniques. These often require labeling of biomolecules that help visualize them. Selective covalent labeling without preliminary modification of the biomolecules is an advantageous method. For example, this can be achieved by using probes that are capable of in situ quinone methide (QM) formation. The QM can be masked to give a stable precursor, and the highly reactive form is only generated upon activation by a specific trigger. The in situ formed QM then binds covalently to the nucleophilic side chains of either the target protein or a protein in close proximity. Using fluorogenic probes further improves this method by reducing non-specific background signals, thus improving signal-to-noise ratios. In this review we summarize the development of quinone methide-based probes from mechanism-based inactivation to red-emitting, fluorogenic activity probes, focusing on enzyme-triggered activation. Full article

(This article belongs to the Special Issue Advances in Fluorescence Sensing)

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