An experimental and theoretical study on mechanistic insights into urolithin-based ratiometric fluorescent probe for instant quantitative detection of fluoride ions

Fluoride detection has been playing an important role in chemical, biological, and medicinal field, especially for keeping physical health and resisting environmental pollution. Herein, a urolithin B fluorescent probe has been successfully developed with good sensitivity, selectivity, anti-interference ability. The low limit of detection (LOD) refers to 0.156 μM, and the instant response time to F- is less than 1 s. The probe is suitable for quantitatively and qualitatively ratiometric detection for F- in solution with two distinct emission bands at 425 (blue) and 566 nm (orange), with the coordinate change of CIE from (0.38, 0.41) to (0.22, 0.11). Urolithin B displayed a remarkable ratiometric fluorescence response towards F-. The detection mechanistic was further proposed by NMR and electronic spectroscopic experiments combining with time-dependent density functional theoretical calculation.

A Handy Chemical Sensor Based on Benzaldehyde and Imidazo[1,2-a]pyridine Mixture for Naked-eye Colorimetric and Fluorescent Detection of F. J Fluoresc 2023;33:2381-2390. [PMID: 37071230 DOI: 10.1007/s10895-023-03195-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Upon the Schiff base condensation reaction of imidazo[1,2-a]pyridine-2-carbohydrazide and 2,5-dihydroxybenzaldehyde, a bimodal colorimetric and fluorescent chemosensor 1o for assaying fluoride (F-) in DMSO was synthesized. The characterization of 1o structure was obtained by 1H NMR, 13C NMR and MS.The structure of 1o was characterized by 1H NMR, 13C NMR and MS. Under the presence of various anions, 1o could be applied for naked-eye and fluorescent detection of F- (naked eye: colorless to yellow; fluorescence: dark to green) and displayed promising performance, such as high selectivity and sensitivity, as well as a low detection limit. Upon calculation, the detection limit of chemosensor 1o for F- was 193.5 nM, which is well below the allowed maximum value of F- (1.5 mg/L) by WHO. As the intermolecular proton transfer mechanism induced "turn-on" fluorescent signal and naked-eye color change of F- to 1o through deprotonation effect, which was confirmed by Job's plot curve, mass spectrometry and 1H NMR titration. Alternatively, the chemosensor 1o can be effectively manufactured into test strips to detect fluoride in solid state, which is user-friendly with no additional equipment required.

Polymer-based lab-on-a-molecule for the selective and sensitive recognition of fluoride and cyanide

A polymer chemical sensor based on lab-on-a-molecule was synthesised by amine-aldehyde polymerisation for selective detection of fluorine ions (F^-) and cyanide (CN^-). The polymer chemical sensor shows significant absorption and fluorescence changes upon the addition of F^- and CN^-, which can be observed by the naked eye and optical reactions. The polymer has a higher fluorescence enhancement effect than its monomer and the distance of wavelength of each anion increased which could be applied to better distinguish the two anions.

Coumarin functionalized molecular scaffolds for the effectual detection of hazardous fluoride and cyanide

Fluoride and cyanide contamination in drinking water imposes detrimental impacts on human health above their permissible limits. Hence, the quantitative detection of these colourless water-soluble toxins has attracted attention. Even though a plethora of chemosensors have been reported so far for the detection of fluoride and cyanide from various matrices, still their applicability is limited to a few examples. Nevertheless, recent advances in the syntheses of coumarin derivatives have shown significant impact on fluoride and cyanide detection. Therefore, this present review provides a brief overview of the application of coumarin-coupled molecular scaffolds towards the detection of perilous fluoride and cyanide along with their sensing mechanisms in order to develop more innovative, simple, sensitive, real-time responsive and cost-effective coumarin-based supramolecular chemosensors to promote next generation approaches towards the ultra-trace quantitative detection of these toxic anions.

Zn2+ detection of a benzimidazole 8-aminoquinoline fluorescent sensor by inhibited tautomerization

The sensor shows a high selectivity and sensitivity toward zinc cations, accompanied by a distinct green fluorescence emission.

Coumarin-Based Small-Molecule Fluorescent Chemosensors

Coumarins are a very large family of compounds containing the unique 2H-chromen-2-one motif, as it is known according to IUPAC nomenclature. Coumarin derivatives are widely found in nature, especially in plants and are constituents of several essential oils. Up to now, thousands of coumarin derivatives have been isolated from nature or produced by chemists. More recently, the coumarin platform has been widely adopted in the design of small-molecule fluorescent chemosensors because of its excellent biocompatibility, strong and stable fluorescence emission, and good structural flexibility. This scaffold has found wide applications in the development of fluorescent chemosensors in the fields of molecular recognition, molecular imaging, bioorganic chemistry, analytical chemistry, materials chemistry, as well as in the biology and medical science communities. This review focuses on the important progress of coumarin-based small-molecule fluorescent chemosensors during the period of 2012-2018. This comprehensive and critical review may facilitate the development of more powerful fluorescent chemosensors for broad and exciting applications in the future.

A quinoxaline-diaminomaleonitrile conjugate system for colorimetric detection of Cu2+ in 100% aqueous medium: observation of aldehyde to acid transformation

In this work, we have strategically incorporated a quinoxaline derivative and a diaminomaleonitrile moiety to construct a chemosensor, 2-amino-3-[(quinoxalin-2-ylmethylene)-amino]-but-2-enedinitrile (H2qm). The notable feature of this strategy is to generate a highly conjugated Schiff base platform with interesting binding properties. Remarkably, H2qm exhibited a visual sensing ability towards Cu2+ in 100% aqueous medium. The effectiveness of the chemosensor has been demonstrated by utilizing it to determine the Cu2+ concentration in real samples. Interestingly, the reaction between H2qm and Cu(ClO4)2·6H2O in DMSO yielded a quinoxaline-2-carboxylic acid based compound and single crystal X-ray diffraction analysis unveiled the resulting structure as [(qa)2Cu(H2O)2] (Hqa = quinoxaline-2-carboxylic acid).

A selective diaminomaleonitrile-based dual channel emissive probe for Al3+ and its application in living cell imaging

A selective diaminomaleonitrile-based fluorescent probe for Al³⁺(L) has been synthesized and characterized. The sensing behavior of L towards different metal ions was investigated by fluorescent spectra and competition experiment. The results showed that L exhibited a dual channel emission (λ_em 522 & 558 nm) with yellow fluorescence in the presence of Al³⁺ over other metal ions in EtOH solution. The probe L was bound to Al³⁺ in a 1:2 stoichiometric manner as supported by Job's plot analysis. The binding constant was 9.55 × 10⁸ M^-2 with the detection limit of 10.3 nM. The turn-on response was attributed to the inhibition of PET and CN isomerization after binding with Al³⁺ while the dual emissions were due to ESIPT and ICT processes. In addition, the application of L for imaging Al³⁺ in living Hela cells was achieved.

A phenolphthalein-based fluorescent probe for the sequential sensing of Al3+ and F- ions in aqueous medium and live cells

A novel fluorescent probe, phenolphthalein‑dialdehyde‑(2‑pyridyl) hydrazone (L), for sequentially detecting Al³⁺ and F^- in almost 100% aqueous medium was successfully designed and synthesized. The probe offers two binding pockets for Al³⁺ to form a 1: 2 ligand/metal complex, leading to a significant fluorescence enhancement at 465 nm. Further, the in-situ formed L-Al complex acts as a secondary fluorescent chemosensor for F^- by quenching the fluorescence of the complex with high selectivity. The detection limit for Al³⁺ and F^- sensing is 2.28 nM and 0.13 μM, respectively, which are far below the World Health Organization (WHO) acceptable limits (7.41 μM for Al³⁺ ion and 79 μM for F^-) in drinking water. The probe L was successfully applied to the detection of Al³⁺ and F^- in cells using fluorescence microscopy.

A novel bifunctional fluorescent and colorimetric probe for detection of mercury and fluoride ions

A fluorescent and colorimetric probe L1 based on a simple coumarin derivative for detection of Hg²⁺ and F^- ions was developed. Upon addition of Hg²⁺ and F^- ions, L1 underwent desulfurization and desilylation, respectively, to induce marked increase in the fluorescence intensity and sharp color change from light yellow to dark purple and light brown, respectively. Probe L1 could be used for sensing and for quantitative measurement of Hg²⁺ and F^- ions by both UV-vis and fluorescence spectra. The bifunctional probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range.

Solvent-induced terbium metal–organic frameworks for highly selective detection of manganese(ii) ions

A pair of Tb framework isomers (UPC-36 and UPC-37) is obtained. 2D layer UPC-37 exhibits higher sensitivity and extra selectivity for the detection of Mn²⁺.

A simple urea-based multianalyte and multichannel chemosensor for the selective detection of F−, Hg2+ and Cu2+ in solution and cells and the extraction of Hg2+ and Cu2+ from real water sources: a logic gate mimic ensemble

Herein, a hydrazine-based chromogenic, fluorogenic and electrochemical chemosensor BCC [1,5-bis(4-cyanophenyl) carbonohydrazide] was reported.

Recent progress in development of 2,3-diaminomaleonitrile (DAMN) based chemosensors for sensing of ionic and reactive oxygen species

2,3-Diaminomaleonitrile (DAMN) has proved to be a valuable organic π-conjugated molecule having many applications in the area of chemosensors for sensing of ionic and neutral species because of its ability to act as a building block for well-defined molecular architectures and scaffolds for preorganised arrays of functionality. In this article, we discussed the utilization of 2,3-diaminomaleonitrile (DAMN) for the design and development of chemosensor molecules and their application in the area of metal ion, anion and reactive oxygen species sensing. Along with these, we present different examples of DAMN based chemosensors for multiple ion sensing. We also discuss the ion sensing mechanism and potential uses in other related areas of research.

2,3-Diamniomaleonitrile (DAMN) is valuable π-conjugated organic scaffold molecule for designing of efficient chemosensors for sensing of ionic and Reactive Oxygen Species (ROS).

A highly selective colorimetric and ratiometric fluorescent probe for instantaneous sensing of Hg2+ in water, soil and seafood and its application on test strips

A new simple and efficient oligothiophene-based colorimetric and ratiometric fluorescent probe has been developed for highly sensitive and fast detection of Hg2+ in water, soil and seafood. The probe 5-(1,3-dithiolan-2-yl)-2,2':5',2″-terthiophene 3 TS can selectively detect Hg2+ via the Hg2+-promoted deprotection reaction of thioacetals, which caused a remarkable color change from colorless to yellow and a strong fluorescence enhancement with emission color varying from blue to yellow, enabling naked-eye detection of Hg2+. The probe shows high sensitivity with the detection limit down to 1.03 × 10-8 M. Visual color changes of 3 TS were observed on filter paper and TLC testing strips when they were impregnated on testing strips and immersed in Hg2+ solution. Moreover, the probe 3 TS has been successfully used to rapidly detect trace amounts of hazardous Hg2+ ions in tap, distilled, river and lake water, cropland soil, fish, shrimp and kelp samples with acceptable results and good recoveries.

Spectroscopic studies of the intramolecular hydrogen bonding in o-hydroxy Schiff bases, derived from diaminomaleonitrile, and their deprotonation reaction products

The structural study of five Schiff bases derived from diaminomaleonitrile (DAMN) and 2-hydroxy carbonyl compounds was performed using ¹H, ¹³C and ¹⁵N NMR methods in solution and in the solid state as well. ATR-FTIR and X-Ray spectroscopies were used for confirmation of the results obtained by NMR method. The imine obtained from DAMN and benzaldehyde was synthesized as a model compound which lacks intramolecular hydrogen bond. Deprotonation of all synthesized compounds was done by treating with tetramethylguanidine (TMG). NMR data revealed that salicylidene Schiff bases in DMSO solution exist as OH forms without intramolecular hydrogen bonds and independent on the substituents in aromatic ring. In the case of 2-hydroxy naphthyl derivative, the OH proton is engaged into weak intramolecular hydrogen bond. Two of imines (salDAMN and 5-BrsalDAMN) exist in DMSO solution as equilibrium mixtures of two isomers (A and B). The structures of equilibrium mixture in the solid state have been studied by NMR, ATR-FTIR and X-Ray methods. The deprotonation of three studied compounds (salDAMN, 5-BrsalDAMN, and 5-CH₃salDAMN) proceeded in two different ways: deprotonation of oxygen atom (X form) or of nitrogen atom of free primary amine group of DAMN moiety (Y form). For 5-NO₂salDAMN and naphDAMN only one form (X) was observed.

The fluorescent property of 3-[(2-hydroxy-1-naphthyl) methylideneamino]benzoic acid and its application as fluorescent chemosensor for Hg2+ and Al3+ ions

This manuscript studies the fluorescent property of 3-[(2-hydroxy-1-naphthyl)methylideneamino]benzoic acid (H₂L). Fluorescent spectra show that in different solvents, H₂L displays different fluorescent properties, which can be attributed to the interaction between the solvents and H₂L. Further study indicates that H₂L exhibits a highly selective and sensitive recognition for Hg²⁺ ions in dimethylsulfoxide (DMSO), Al³⁺ ions in methanol and N,N'-dimethylformamide/water (DMF/H₂O, 1/1, v/v). The bonding modes and bonding ratio of H₂L and metal ions in different solvents are explored by Job's plot, ¹H NMR titration, and electrospray ionization mass spectrometry (ESI-MS). The probable mechanisms were discussed.

Furan and Julolidine-Based "Turn-on" Fluorescence Chemosensor for Detection of F- in a Near-Perfect Aqueous Solution

A new fluorescent sensor 1, containing furan and julolidine moieties linked through a Schiff-base, has been synthesized. Distinct "turn-on" fluorescence enhancement of 1 was observed upon the addition of F^- in a near-perfect aqueous solution. The binding capabilities of 1 with F^- were studied by using fluorescent spectroscopic techniques, ESI-mass analysis and NMR titration measurements. The detection limit for the analysis of F^- was found to be 10.02 μM, which is below the WHO guideline (79 μM) for drinking water. Practically, the sensing ability of 1 for F^- was successfully applied in real water samples. The sensing mechanism for F^- was proposed to be the ICT mechanism via the hydrogen bonding, which was well explained by theoretical calculations.

Rhodamine Diaminomaleonitrile Conjugate as a Novel Colorimetric Fluorescent Sensor for Recognition of Cd2+ Ion

Rhodamine diaminomaleonitrile linked probe (RD-1) shows highly sensitive colorimetric and selective turn-on fluorescent response to Cd²⁺ over other metal ions. The fluorescence intensity and absorbance of the probe RD-1 showed a good linearity, with very low detection limits of 18.5 nm. The probe RD-1 was preliminarily applied to the determination of Cd²⁺ ion in water samples from river and tap water with satisfying results. The live cell image confocal microscopy, HeLa cell demonstrated that RD-1 had low cytotoxicity with good membrane permeable property is successfully applied to fluorescence microscopic imaging for the detection of Cd²⁺ ions.

Facile synthesis of a water-soluble fluorescence sensor for Al3+ in aqueous solution and on paper substrate

In this study, a facile water-soluble fluorescence sensor 2-((2-hydroxybenzylidene)-amino)-2-(hydroxymethyl)propane-1,3-diol (ST) was synthesized via one-step reaction, and its fluorescence sensing performance for Al³⁺ both in aqueous solution and on paper substrate was evaluated. The results showed that ST exhibited an specific fluorescence "turn-on" response to Al³⁺ over other cations in aqueous solution as well as on the test paper. The limit of detection was found to be 3.2×10^-7M, which revealed that the obtained Schiff-base based fluorescence chemosensor ST possessed a great potential for the rapid, quantitative and qualitative detection of Al³⁺.

A new multifunctional Schiff-based chemosensor for mask-free fluorimetric and colorimetric sensing of F⁻ and CN⁻

A Schiff-based chemosensor DSS was designed for selective and simultaneous detection and/or determination of F(-) and CN(-) by distinguishable changes in both solution color and spectroscopic responses within same sample due to the strong emission enhancement at distinct emission bands without any mask. In addition, the sensing mechanism was evaluated by NMR titration and DFT calculations.

A highly selective fluorescent sensor for the detection of Al3+ and CN− in aqueous solution: biological applications and DFT calculations

A new turn-on fluorescent chemosensor 1 was developed to detect both Al³⁺ and CN⁻ and used for practical and biological applications.

Distinction between Mn(iii) and Mn(ii) by using a colorimetric chemosensor in aqueous solution

A new colorimetric chemosensor for Mn(iii) and Mn(ii) was developed and used to differentiate between Mn(iii) and Mn(ii).

A selective colorimetric chemosensor with an electron-withdrawing group for multi-analytes CN− and F−

A colorimetric chemosensor with an electron-withdrawing group (–NO₂) 1 for the detection of CN⁻ and F⁻ was developed.

Chromogenic naked-eye detection of copper ion and fluoride

Colorimetric chemosensor was reported for detection of Cu²⁺ and F⁻via the color change from colorless to yellow and to orange.

A highly selective and sensitive fluorescence “turn-on” fluoride ion sensor

A highly selective and sensitive fluorescence “turn-on” and colorimetric dual-channel fluoride ion sensor.

Benzimidazolium-based chemosensors: selective recognition of H2PO4−, HP2O73−, F− and ATP through fluorescence and gelation studies

Benzimidazolium-based receptors 1 and 2 exhibit sensing properties towards different anions such as H₂PO₄⁻, HP₂O₇³⁻ and F⁻ under identical condition. Experimental results are correlated with the theoretical findings.