Chemosensors For Anions Research Articles

Design and development of an azo dye‐based ultra‐sensitive chemosensor for the ubiquitous organic anion in aqueous solutions

AbstractOxalate plays a crucial role in various biological and industrial applications. Its involvement in diseases, drug‐ and toxin‐induced disorders, and disruption of industrial processes makes it a high‐priority chemical for the development of more precise, selective, and straightforward analytical methods. Herein, an innovative and efficient strategy for sequentially measuring Cu2+ and oxalate ions is reported. During an indicator displacement process, where Cu2+ and azo dye, ArsenazoIII (AAIII), are used as receiver and indicator, respectively, oxalate (C2O42−) is measured by a colorimetric method. Proof of concept results from UV–visible spectroscopy, naked eye, and signal reset of the indicator revealed a more robust interaction of the Cu2+ receptor with C2O42− than the AAIII indicator with high selectivity, good sensitivity, and lower detection limit(4.01 × 10−8 and 3.04 × 10−9mol L−1, for Cu2+ and C2O42−, respectively). The results of measuring C2O42− in actual samples (urine, mushrooms, and spinach) showed the applicability of the existing method. Most importantly, the colorimetric system based on molecular exchange in the indicator dislocation proceeding can serve as a colorimetric INHIBIT logic‐gate. It works like a molecular keypad lock system that can be controlled by two users with two different sets of chemical passwords (inputs) that can be identified through optical paths.

Ratiometric fluorescence-based and chromogenic sensors for the detection of fluoride ions and their application in real samples.

This review focuses on the results of synthetic ratiometric fluorescent and colorimetric probes, which have been applied to qualitatively and quantitatively detect fluoride anions in cells, living organisms, and real samples. Primary attention is given to progress made in the working mechanism and applications of these probes to detect fluoride ions in living systems. In addition, design strategies and detection limit for these probes are discussed. This review aims to deliver a comprehensive compilation of the examples reported from 2005 to 2021 on the developments of ratiometric chromogenic and fluorogenic chemosensors for fluoride anions. A total of 20 different ratiometric/colorimetric sensors have been selected for the novelty in their design, sensitivity, detection limit, dynamic range, and speed of detection based on the three fundamental principles of F- ion detection, namely Si-O bond cleavage; excimer emission; and intramolecular charge transfer emission through the B-F monomer, B-F-B bridged dimers, and deprotonation of the amide N-H. Special emphasis has been given to categorize the fluorophores that work in aqueous media, and possible strategies that might be adopted to design green sensors are discussed. Finally, a tabular summary of the comparative studies of all the sensors based on their sensitivity, detection limit, working solvent, and applications is provided. This extensive review may expedite improvements in the development of advanced fluorescent probes for vast and stimulating applications in the future.

A new colorimetric sensor based on semithiocarbazone for some anions: 2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-N-phenylhydrazine-1-carbothioamide

Carbazones are molecules containing important functional groups in designing anion chemosensors due to proton donor and acceptor sites in their structures. In this paper, we synthesize a novel colorimetric receptor with 1,3-dioxo-indene and thiosemicarbazone moieties by the reaction of ninhydrin and 4-phenyl-thiosemicarbazide in quantitative yield. We then identify its structure by means of FT-IR, $^{1}$H-NMR, $^{13}$C-NMR, and MS spectroscopic techniques. Moreover, we observe the reaction of the title compound with biologically important F$^¯$, OAc$^¯$, CN$^¯$, H2PO4$^¯$, and OH$^¯$ anions in the presence of other anions, such as Cl$^¯$, Br$^¯$, I$^¯$, SCN$^¯$, and OCl$^¯$ in dimethylsulfoxide solution through a color change from yellow to orange-red that can easily be distinguished even by the naked eye under ambient light. Finally, we evaluate the anion-sensing ability of the title compound via UV-vis spectroscopic studies.

UV-Vis spectroscopic and colorimetric anion detection and fluorescence properties of new 3-amino-4-hydroxybenzenesulfonic acid-based Schiff bases depending on the strength and position of the electron donor substitution

In this study, 3-amino-4-hydroxybenzenesulfonic acid-based imine compounds; 3-(2,5-dihydroxybenzylideneamino)-4-hydroxybenzenesulfonic acid (1), 3-(2,4-dihydroxybenzylideneamino)-4-hydroxybenzenesulfonic acid (2) and 4-hydroxy-3-(2-hydroxy-3-methoxybenzylideneamino)-4-hydroxybenzenesulfonic acid (3) was synthesized. The compounds were analyzed using various spectroscopy methods, and the experimental UV–vis data matched the theoretical predictions. The compound 1 displayed lower stability, higher reactivity, and easier photoexcitation due to a smaller HOMO-LUMO energy gap. The investigated compounds 1-3 showed promise as chemosensors for anions, providing visible detection in daylight conditions. The compound 3 exhibited selective fluorescence at specific wavelengths. The compounds 1-3 interacted with DNA through electrostatic interactions. Also, compounds 1-3 showed higher antioxidant activity than BHT. However, fluorescence measurements indicated that the emission signals were strongly influenced by the position and strength of the electron-donating group. Adding a hydroxy or methoxy moiety near the -OH group on the phenyl ring decreased the fluorescence signal due to intersystem crossing and intramolecular charge transfer mechanisms, respectively. These findings were supported by femtosecond transient absorption spectroscopy measurements. The results emphasize the significance of substituents in imines derived from 3-amino-4-hydroxybenzenesulfonic acid in determining their biological activities, as well as their optical and sensor properties.

Synthesis of two novel fluorescein appended dipyromethanes (DPMs): Naked-eye chemosensors for fluoride, acetate and phosphate anions

Two novel fluorescein based dipyromethane probes DPM1 and DPM2 were constructed from a simple and easily accessible fluorescein dye, and were fully characterized by means of standard spectroscopic techniques. Studies of the DPM1 and DPM2, investigated using UV–vis spectroscopy with different anions in CH3CN/DMSO, displayed selective colorimetric sensing towards fluoride, acetate and phosphate anions. Moreover, the fluorescence analysis was also accomplished with DPM1/DPM2, revealing the enhancement in the emission spectra of the fluoride, acetate and phosphate anions. From the studies, we noticed that the DPM1/DPM2 having spirolactone ring is non-fluorescent, which upon addition of the fluoride, phosphate and acetate, underwent ring-opening, resulting in the generation of strong fluorescence. The solid state images divulges that DPM1 shows green fluorescence and DPM2 displayed dark green fluorescence upon irradiating with UV-light of wavelength 254 nm. We infer that such types of naked eye sensors might reveal the potential applications in the selective and sensitive detection of fluoride/acetate/phosphate, and/or other biologically significant anions in nearby future.

Selective Luminescent Chemosensing of Chloride Based on a Cyclometalated Platinum(II) Complex in Water: Crystal Structures, Spectroscopic Studies, Extraction, and Bioimaging

Selective anion sensing by luminescent chemosensors capable of operating in aqueous conditions is a central field of modern supramolecular chemistry that impacts analytical and biological chemistry. A cationic cyclometalated [Pt(N^C^N)NCCH3]OTf complex, 1 [N^C^N = 1,3-bis(1-(p-tolyl)-benzimidazol-2'-yl)benzene, OTf = triflate], was prepared, structurally described by single-crystal X-ray diffraction and studied in-depth as a luminescent chemosensor for anions in aqueous phase and solid state. A series of related neutral [Pt(N^C^N)X] complexes (X = Cl, 2; CN, 3 and I, 4) were formed readily upon treatment of 1 with the respective NaX salt in aqueous media and were described structurally by X-ray diffraction. Complex 1 is hydrostable with phosphorescent green emission originated by intraligand transitions, and [dyz(Pt) → π*(N^C^N)] charge transfer transitions, as evidenced by TD-DFT calculations and lifetime. Additions of halides, pseudohalides, oxyanions, and dicarboxylates to a neutral aqueous solution of 1 modified its green emission intensity with a pronounced affinity (K = 1.5 × 105 M-1) and turn-on signal toward Cl- within the micromolar concentration range. Pt complex 1 is two orders of magnitude more selective for Cl- than the other halides, CN- and basic oxyanions. Such Cl- affinity for a metal-based chemosensor in aqueous media is still rare. On the basis of X-ray crystallographic analysis and multiple spectroscopic tools (NMR, UV-vis, luminescence, MS, lifetimes) the origin of this selectivity hinges on the cooperative three-point recognition involving one coordination bond (Pt-Cl) and two convergent short C-H···Cl- contacts. This strong affinity and efficient optical response can be utilized in quantitative Cl- sensing in real samples and solid-liquid extractions. Additionally, chloro-Pt complex, 2 may be relevant to bioimaging as a marker for cell nuclei, as revealed by its emission within living cells and intracellular distribution by confocal microscopic studies. These results demonstrate the usefulness of the new water-stable luminescent Pt-N^C^N complexes as effective analytical tools in anion sensing and extraction agents.

Development and Application of Ruthenium(II) and Iridium(III) Based Complexes for Anion Sensing.

Improvements in the design of receptors for the detection and quantification of anions are desirable and ongoing in the field of anion chemistry, and remarkable progress has been made in this direction. In this regard, the development of luminescent chemosensors for sensing anions is an imperative and demanding sub-area in supramolecular chemistry. This decade, in particular, witnessed advancements in chemosensors based on ruthenium and iridium complexes for anion sensing by virtue of their modular synthesis and rich chemical and photophysical properties, such as visible excitation wavelength, high quantum efficiency, high luminescence intensity, long lifetimes of phosphorescence, and large Stokes shifts, etc. Thus, this review aims to summarize the recent advances in the development of ruthenium(II) and iridium(III)-based complexes for their application as luminescent chemosensors for anion sensing. In addition, the focus was devoted to designing aspects of polypyridyl complexes of these two transition metals with different recognition motifs, which upon interacting with different inorganic anions, produces desirable quantifiable outputs.

A Near InfraRed Emissive Chemosensor for Zn2+ and Phosphate Derivatives Based on a Di-(2-picolyl)amine-styrylflavylium Push-Pull Fluorophore.

A new Near InfraRed (NIR) fluorescent chemosensor for metal ions and anions is herein presented. The fluorophore is based on a styrylflavylium dye, a synthetic analogue of the natural anthocyanin family, with a di-(2-picolyl)amine (DPA) moiety as the metal chelating unit. The substitution pattern of the styrylflavylium core (with tertiary amines on positions 7 and 4') shifts the optical properties of the dye towards the NIR region of the electronic spectra, due to a strong push-pull character over the π-conjugated system. The NIR chemosensor is highly sensitive to the presence of Zn2+, which induces a strong CHelation Enhanced Fluorescence (CHEF) effect upon binding to the DPA unit (2.7 fold increase). The strongest competing ion is Cu2+, with a complete fluorescence quenching, while other metals induce lower responses on the optical properties of the chemosensor. Subsequent anion screening of the Zn2+-chemosensor coordination compound has demonstrated a distinct selectivity towards adenosine 5'-triphosphate (ATP) and adenosine 5'-diphosphate (ADP), with high association constants (K ~ 106 M-1) and a strong CHEF effect (2.4 and 2.9 fold fluorescence increase for ATP and ADP, respectively). Intracellular studies with the Zn2+-complexed sensor showed strong luminescence in the cellular membrane of Gram- bacteria (E. coli) and mitochondrial membrane of mammalian cells (A659), which highlights its possible application for intracellular labelling.

Synthesis of Vanillin-Azine as Colorimetric Chemosensor of Sulfide Anion

Vanillin-azine (VA), (4,4'-((1E,1'E)-hydrazine-1,2-diylidenebis(methane-lylidene))bis(2-methoxyphenol) has been synthesized from vanillin and tested as anion colorimetric chemosensors for sulfide anion. The VA was obtained from a condensation reaction between vanillin and hydrazine hydrate with a mol ratio of 2:1 mol for 24 h at room temperature. The structure was elucidated using FTIR, GC-MS, 1H-NMR, and 13C-NMR spectrometers. The VA compound was examined as a colorimetric chemosensor for sulfide anion over several anions of CN−, F−, Cl−, Br−, I−, N3−, CH3COO−, and NO3−. The structure of the product showed agreement with all spectrometric data. The VA chemosensor tests indicated only selective to S2− anion followed by a color change from colorless to light blue in a DMF:HEPES buffer solution (DMF:HBS) medium (9:1, v/v, 10 mM, pH = 7.4). Filter paper strips can detect S2− anion with a color change from white to yellow. The VA chemosensor has a limit of detection (LOD) of 5.4 × 10−4 M, therefore, the VA chemosensor can be applied to detect S2− anion in tap water.

New Dinitrophenyl Hydrazones as Colorimetric Probes for Anions

Anion sensing is a dynamic research field due to the biological and environmental importance of some organic or inorganic anions. Hydrazones show promising properties in the design of anion chemosensors due to the presence of proton donor and acceptor sites in their structure. In this work, two novel dinitrophenyl hydrazones, functionalized with a quinoline moiety, were synthesized and characterized by spectroscopic and spectrometric techniques. The interaction between the new compounds 3a–b with different organic and inorganic anions was assessed. The two compounds showed a change in color from light yellow to magenta in the presence of H2PO4−, CH3COO−, BzO−, CN−, and F−. The interactions were analyzed by spectrophotometric titrations and the stoichiometry of the interaction was assessed by the method of continuous variation. Compound 3b showed a remarkable sensitivity to CN−, with a limit of detection of 0.35 µM. The interaction of compound 3b with CN− and F− was also analyzed by 1H NMR titrations, showing that an increasing concentration of anions induce a deprotonation of the NH and OH groups.

Synthesis, Characterization, and Application of Chalcone Derivatives as Chemosensors for Cyanide Anions

Background: The extreme toxicity of cyanide ions to living organisms encourages the researcher to develop new chemosensors for their sensitive and selective detection. Among various classes of chemosensors, chalcones are believed to be a promising candidate for designing new chemosensors for anions due to easy modification in their skeleton and conjugation system. Research Gap and Problem Statement: Despite having various medical applications and properties, the recognition ability of chalcone derivatives is not widely explored. The traditional methods known for the sensing of cyanide ions are ion chromatography or cyanide selective electrodes. However, these methods need skilled operators and are found to be expensive and time-consuming. Also, the available methods for the detection of cyanide ions are not suitable for on-site monitoring and show interference from other competitive anions, such as fluoride, acetate, and hydroxide ions. Hence, this encouraged us to explore the chalcone derivatives as chemical sensors that are capable of detecting the cyanide ions in the presence of competitive anions, such as fluoride, acetate, and hydroxide ions. Objectives: The development of new chalcone analogs (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6), which are particularly important for the future development of chemosensors for the detection of cyanide ions in the presence of various interfering ions, such as fluoride, acetate, and hydroxide ions. Methods: The sensing behavior of chalcone derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) have been investigated toward various anions (CN-, F-, Cl-, Br-, NO3 -, SO4 2-, PO4 2-, OH-, OAc-) using UV-vis spectroscopy. Interestingly, among various anions tested, derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2- yl)prop-2-en-1-one (6) function as highly selective chemosensors for the detection of cyanide ions. Results: We have synthesized two chalcone based derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3- one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) with simple condensation reaction for the detection of cyanide ions. The various results indicated the quick response of (1E,4E)-1,5-bis(4- chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) toward cyanide anions. These two chalcone derivatives showed not only spectral change with selectivity but also showed sensitivity for the detection of cyanide anions. The developed chalcone derivatives detect cyanide ions in the presence of various interfering ions, such as fluoride, acetate, and hydroxide ions. The chemosensors (1E,4E)- 1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) for the detection of cyanide ions are particularly smart due to their real-time analysis, simplicity, and low cost in comparison to other closely related processes, such as fluorescence. Conclusion: The sensitivity studies show the high reactivity of derivative 1,5-bis(4-chlorophenyl)penta-1,4- dien-3-one (3) as compared to (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6). The detection limit for derivatives (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4-dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2- en-1-one (6) was 1.2 μM and 300 μM, respectively. The results of (1E,4E)-1,5-bis(4-chlorophenyl)penta-1,4- dien-3-one (3) and (E)-3-phenyl-1-(pyridin-2-yl)prop-2-en-1-one (6) for cyanide detection were satisfying, suggesting their potential application for cyanide detection. Future Direction: The goal of further research of this field is to develop water-soluble chalcone-based probes, which show emission in the Near Infra-Red (NIR) region to provide favorable conditions for biological applications.

A Mini Review on Arsenic and Cadmium Ion Detection Using Fluorescent-Colorimetric Sensors

Heavy metals with high atomic numbers, mass, and density are five times greater than water. They are naturally occurring elements and widely distributed in the environment due to their numerous applications like agricultural, industrial, domestic, technological, and medical fields increasing issues about their potential impact on the environment and human health. In this mini review, we focused on cadmium and arsenic metals. Cadmium is also the non-essential toxic heavy metal element found naturally in the earth's crust, and it is easily affected by plants’ movements through the food cycle and also causes harm to live beings. Arsenic is a common element found in low amounts in almost all environmental compartments. Chemosensors play a pivotal role in environmental and analytical chemistry. Chemosensors can detect enzymes, anions, and hazardous heavy metal ions with excellent selectivity and sensitivity at a low cost. Colorimetric chemosensors are instruments that convert chemical data into analytically relevant signals that can be viewed with the naked eye. Fluorescent-based chemosensors for cations, anions, and neutral analytes have been used in a wide range of applications.

Importance of BODIPY-based Chemosensors for Cations and Anions in Bio-imaging Applications

Background:Chemosensor compounds are useful for sensitive selective detection of cations and anions with fluorophore groups in an attempt to develop the effective selectivity of the sensors. Although familiar fluorescent sensors utilizing inter-molecular interactions with the cations and anions, an extraordinary endeavor was executed the preparation of fluorescent-based sensor compounds. 4,4-difluoro-4- bora-3a,4a-diaza-s-indacene (Bodipy) and its derivatives were firstly used as an agent in the imaging of biomolecules due to their interesting structures, complexation, and fluorogenic properties. Among the fluorescent chemosensors used for cations and anions, Bodipy-based probes stand out owing to the excellent properties such as sharp emission profile, high stability, etc. In this review, we emphasize the Bodipy-based chemosensor compounds, which have been used to image cations and anions in living cells, because of as well as the biocompatibility and spectroscopic properties.Methods:Research and online content related to chemosensor online activity is reviewed. The advances, sensing mechanisms and design strategies of the fluorophore exploiting selective detection of some cation and anions with Bodipy-based chemosensors are explained. It could be claimed that the using of Bodipy-based chemosensors is very important for cations and anions in bio-imaging applications.Results:Molecular sensors or chemosensors are molecules that show a change can be detected when affected by the analyte. They are capable of producing a measurable signal when they are selective for a particular molecule. Molecular and ion recognition that it is important in biological systems such as enzymes, genes, environment, and chemical fields. Due to the toxic properties of many heavy metal ions, it is of great importance to identify these metals due to their harmful effects on living metabolism and the pollution they create in the environment. This process can be performed with analytical methods based on atomic absorption and emission. The fluorescence methods among chemosensor systems have many advantages such as sensitivity, selectivity, low price, simplicity of using the instrument and direct determination in solutions. The fluorescence studies can be applied at nanomolar concentrations.Conclusion:During a few decades, a lot of Bodipy-based chemosensors for the detection of cations & anions have been investigated in bio-imaging applications. For the Bodipy-based fluorescent chemosensors, the Bodipy derivatives were prepared by different ligand groups for the illumination of the photophysical and photochemical properties. The synthesized Bodipy-based chemosensors have remarkable photophysical properties, such as a high quantum yield, strong molar absorption coefficient etc. Moreover, these chemosensors were successfully implemented on living organisms for the detection of analytes.

Reversal of a Fluorescent Fluoride Chemosensor from Turn-Off to Turn-On Based on Aggregation Induced Emission Properties.

Here we present a new approach for the development of fluoride chemosensors taking advantage of aggregation induced emission (AIE) properties. Although AIE-based chemosensors have been described, they rely primarily on the analyte causing aggregation and hence fluorescence. We propose a new concept in the use of AIE for the development of fluorescent sensors. Our hypothesis is based on the fact that a turn-off chemosensor in solution can be transformed into turn-on in the solid state if the properties of ACQ and AIE are properly combined between the fluorescent molecules involved. To demonstrate this hypothesis, we have selected a fluorescent chemosensor for the fluoride anion with a conjugated structure of bis(styryl)pyrimidine that, while showing turn-off behavior in solution, becomes turn-on when it is brought to the solid state. We have also combined it with the advantages of a detection system based on the microfluidic paper-based analytical devices (μPAD). The system is fully characterized spectroscopically both in solution and in the solid state, and quantum mechanical calculations were performed to explain how the sensor works. The prepared device presents a high sensitivity, with no interference and with an LoD and LoQ that allow determination of fluoride concentrations in water 2 orders of magnitude below the maximum allowed by WHO.

Benzimidazole appended optical sensors for ionic species: Compilation of literature reports from 2017 to 2022

Rigorous advancement in the area of generation of optical (colorimetric/fluorescent) chemosensors has seen brilliant success as vibrant tools for the selective and sensitive tracking of analytes (cations and/or anions etc.) since the advent of supramolecular chemistry. Several benzimidazole derivatives and their impending significance in field of molecular recognition have been reported in this literature review, which point to the vitality of the chemosensing area. The present review delivers comprehensions into different benzimidazole based derivatives with varied structural modulations by pyridine, coumarin, pyrazole, pyrene, carbazole and Schiff base functionalities for optical detection of a variety of analytes (metal ions and/or anions). The discussed literature reports will excavate new avenues and enable research fraternities to develop superlative chemosensors with enhanced sensitivity and selectivity. This review highlights the development of various benzimidazole appended optical chemosensors for various metal ions and anions since 2017.

Efficient Colorimetric Fluoride Anion Sensor Based on π-Conjugated Carbazole Small Molecule.

The ability to detect fluoride anions with high selectivity and sensitivity by using the naked eye is crucial yet challenging. In this study, a novel, simple conjugated organic dye, N-tert-butyldimethylsilyl-3,6-diiodocarbazole (CA-TBMDS) was developed and used for the first time as a colorimetric sensor for fluoride. CA-TBMDS was found to be a highly sensitive fluoride chemosensor, with a detection limit as low as 3 × 10−5 M. The reaction of CA-TBMDS with fluoride anions in a tetrahydrofuran solution resulted in a color change from colorless to yellow under ambient light, which can be discriminated by the naked eye. The sensor operated via intermolecular proton transfer between the amide units and the fluoride anion, as confirmed by proton nuclear magnetic resonance titration. CA-TBMDS is not only highly sensitive to fluoride anions, but also exhibits high sensitivity in the presence of various ions. This work demonstrates that N-butyldimethylchlorosilane-based organic dyes have prospective utility as a type of fluoride anion chemosensor.

Hydrogen-Bonded Colorimetric and Fluorescence Chemosensor for Fluoride Anion With High Selectivity and Sensitivity: A Review.

In recent years, the wide application of fluoride materials has grown rapidly, therefore excessive discharge in the surrounding environment, especially in drinking water and organic effluent, has become a potential hazard to humans, and has even resulted in fluorosis disease. The development of a highly effective and convenient method to recognize fluoride anions in surrounding environments seems necessary and urgent. Among which, the development of a colorimetric and fluorescence fluoride chemosensor with obvious color changing allowing for naked-eye detection with high sensitivity and selectivity is more interesting and challenging. In this minireview, current novel colorimetric and fluorescence chemosensors for fluoride anions by hydrogen-bond interaction are introduced, including obvious color changing by naked-eye detection, high sensitivity and selectivity, non-pollution and fluoride extraction ability, aqueous detection, and other additional functions. Finally, the perspective of the fluoride chemosensor design concept and potential evolution trends are pointed out.

Recent Advances in Colorimetric and Fluorescent Chemosensors for Ionic Species: Design, Principle and Optical Signalling Mechanism

AbstractDevelopment of chemosensors for the biologically and chemically important ionic species has been an active area of research of supramolecular chemistry and received great attention because of their high sensitivity, selectivity, rapid response time and versatility. Moreover, exploration of new sensing mechanisms of interaction between recognition and signal reporting unit is of current interest. This minireview provides a detailed overview about the recent advances and developments in the field of colorimetric and fluorescent chemosensors, summarized types of optical chemosensors with their design principles and discuss various sensing mechanisms and photophysical processes like metal‐ligand charge transfer (MLCT), ligand‐metal charge transfer (LMCT), photoinduced electron transfer (PET), intramolecular charge transfer (ICT), paramagnetic fluorescence quenching, fluorescence resonance energy transfer (FRET), excited state intramolecular proton transfer (ESIPT), excimer/ exciplex formation that emerged in the past few years. Moreover, the mechanism of action of cation and anion chemosensors also summarizes in this review.

Phthalocyanine-Functionalized Magnetic Silica Nanoparticles as Anion Chemosensors.

Anionic species are one of the most common pollutants in residual and freshwaters. The presence of anthropogenic anions in water drastically increases the toxicity to living beings. Here, we report the preparation of a new optical active material based on tri(tosylamino)phthalocyanines grafted to ferromagnetic silica nanoparticles for anion detection and removal. The new unsymmetrical phthalocyanines (Pcs) proved to be excellent chemosensors for several anions (AcO−, Br−, Cl−, CN−, F−, H2PO4−, HSO4−, NO2−, NO3−, and OH−) in dimethyl sulfoxide (DMSO). Furthermore, the Pcs were grafted onto magnetic nanoparticles. The resulting novel hybrid material showed selectivity and sensitivity towards CN−, F−, and OH− anions in DMSO with limit of detection (LoD) of ≈4.0 µM. In water, the new hybrid chemosensor demonstrated selectivity and sensitivity for CN− and OH− anions with LoD of ≈0.2 µM. The new hybrids are easily recovered using a magnet, allowing recyclability and reusability, after acidic treatment, without losing the sensing proprieties.

Synthesis of Coumarin Derived Thiosemicarbazones as Colorimetric and Fluorescent 'Turn On' Chemosensors for Fluoride Ions

Chemosensors are getting attention day-by-day owing to their usage as analyte detector for environmental pollutants and in biological imaging. Coumarin based thiosemicarbazones (S1 and S-2) are reported as anionic chemosensors. The structural elucidation of the synthesized chemosensors is done by 1 H-NMR, 13 C-NMR, UV-Visible spectroscopy, and Fluorescence emission spectroscopy. The limit of detection (LOD) for F − ions was determined as 23.33 μM and 16.90 μM while the binding constant was assessed as 4.92 × 10 4 M −1 and 4.84 × 10 4 M −1 for sensor S1 and S2 respectively, based on UV–vis titration using Benesi-Hildebrand equation.