Chemosensors For Metal Ions Research Articles

Naphthalen-2-yl-N′-(2-hydroxybenzoyl)benzohydrazonate as dual metal ion chemosensor for the detection of Fe3+ and Na+ ions

New probe naphthalen-2-yl-N′-(2-hydroxybenzoyl)benzohydrazonate (NHBH) chemosensor has been prepared and characterized by IR, 1H NMR, 13C NMR and Mass Spectroscopic techniques. The probe (NHBH) was subjected to study its cation sensing ability with twelve different metal chloride salt (Al3+, Ca2+, Co2+, Cr3+, Fe3+, Cu2+, Mn2+, Ni2+, Zn2+, Hg2+, K+ and Na+) in 1:4 methanol water medium by using absorption and emission titration experiments. The results showed that the probe detected Fe3+ and Na ​+ ​ions by showing absorption enhancement and fluorescence emission quenching. Further, NHBH exhibited good selectivity for Fe3+ and Na ​+ ​ions in the presence of mostother metal ions. Job's plot analysis authenticated the 1:1 binding nature of NHBH with Fe3+ and Na ​+ ​ions. Further, DFT studies validated the formation of probe (NHBH), fluorophore-quencher (Fe-NHBH) complex formation.

Indole-based Fluorometric and Colorimetric Chemosensors for the Selective Detection of Cu2+: A Brief Review From the Year 2011-2021

The development of chemosensors has been driven by concurrently advanced research in fluorescence and colorimetric chemosensing. Over the last few decades, the development of copper ion-selective fluorogenic and chromogenic chemosensors has been extensively studied due to their high sensitivity, low cost, and simplicity. They can interact with the metal ion in a unique manner and create measurable color, fluorescence, or redox potential changes. Copper (Cu2+) ion is deemed the third most prevalent transition metal in human beings owing to its various biological and physiological processes. It has drawn a great deal of attention from many researchers in various disciplines such as biology, medicine, and environmental studies. However, an excessive buildup of copper in the body has been linked to several diseases. Thus, more recent research is being focused on developing fluorometric and colorimetric chemosensors for the selective detection of copper ions. Recently, there have been a lot of studies reported in this field of study that describe highly sensitive and sophisticated indole-based chemosensors for various metal ions of interest. In addition, indole derivatives possess inherent fluorescence properties due to their electron-rich nature caused by the π-excessive system of indole, and therefore they can be employed in chemosensors for metal ion detection. Both cations and anions employ it as a molecular recognition system. This review summarizes selective and sensitive Cu2+ ion detection accomplished byvarious indole-based chemosensors between the years 2011 to 2021. Furthermore, sensor design, sensing methods, ligand-metal binding stoichiometry, association constant, and the detection limit by the chemosensors are all summarized and explored.
 Keywords: Indole, Fluorescent chemosensors, Colorimetric chemosensors, Cu2+, Turn-on, Turn-off

Photoswitchable Rhodamine‐Based Multianalyte Sensors for Metal Ion Detection

AbstractWe have developed three azobenzene‐core‐based molecular systems decorated with different numbers of rhodamine units as photoswitchable multianalyte sensors. Exploiting the ring‐opening of the spirolactam part of the rhodamine unit, the resulting fluorescence response, and modulation of it through the photoswitching of azobenzene by light, we utilized them in the detection of multiple metal ions (Fe3+, Fe2+, Sn2+ and Al3+). The binding sites, stoichiometry, binding constants, fluorescent lifetimes and limit of detection (LOD) for each probe have been deduced using appropriate spectroscopic techniques. The limit of detection (LOD) of 5 a, 5 b and 5 c for Fe3+ are found to be 4.2×10−7±7.8×10−9 M, 2.2×10−7±4.6×10−9 M and 1.2×10−7±4.6×10−9 M, respectively. The fluorescence response of the metal‐chelated complex can be manipulated effectively by employing the photoswitching ability of azobenzene that makes them useful as chemosensors for various individual metal ions.

A turn-on mode fluorescent diarylethene having an azacrown ether receptor: Metal-ion-gated enhancement of the photoreactivity and fluorescence

We report the metal-ion-gated enhancement of the photoreaction and fluorescence of a newly synthesized photoswitchable fluorescent diarylethene derivative having an azacrown ether receptor. In the absence of metal ions, the diarylethene molecule underwent the photoisomerization and turn-on mode switching of fluorescence, but the photoreactivity and fluorescing ability were suppressed by intramolecular photoinduced electron transfer (PET) from the azacrown ether moiety to the diarylethene unit. Upon binding of a metal ion to the azacrown ether, the PET process was blocked, and the photoreactivity and fluorescence were significantly enhanced. Such photoswitchable fluorescent molecules that change their photoresponsive properties upon recognizing metal ions have the potential to function as metal-ion chemosensors and molecular probes in metal-ion-sensitive super-resolution fluorescence microscopy.

Printed colorimetric chemosensor array on a 96-microwell paper substrate for metal ions in river water.

Here, we propose a printed 96-well microtiter paper-based chemosensor array device (PCSAD) to simultaneously detect metal ions for river water assessment. Colorimetric chemosensors for metal ions have been designed based on molecular self-assembly using off-the-shelf catechol dyes and a phenylboronic acid (PBA) derivative. The colorimetric self-assembled chemosensors consisting of catechol dyes and a PBA derivative on a 96-well microtiter paper substrate demonstrated various color changes according to the disassembly of the ensembles by the addition of nine types of metal ions. An in-house-made algorithm was used to automate imaging analysis and extract color intensities at seven types of color channels from a captured digital image, allowing for rapid data processing. The obtained information-rich inset data showed fingerprint-like colorimetric responses and was applied to the qualitative and quantitative pattern recognition of metal ions using chemometric techniques. The feasibility of the 96-well microtiter PCSAD for environmental assessment has been revealed by the demonstration of a spike-and-recovery test against metal ions in a river water sample.

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.

Spontaneous preparation of a fluorescent ratiometric chemosensor for metal ions using off-the-shelf materials.

A self-assembled chemosensor prepared using off-the-shelf materials has shown various fluorescence responses including ratiometric and simple ON-OFF switching profiles by adding different toxic metal ions. The unique fingerprint-like responses have been applied to pattern recognition of metal ions in river water for environmental analysis.

Colorimetric/fluorometric optical chemosensors based on oxazolidine for highly selective detection of Fe3+ and Ag+ in aqueous media: Development of ionochromic security papers

Photodetection of metal ions in different environments is a noteworthy research. Some sensitive oxazolidine derivatives were synthesized and their responsivities toward different metal ions were investigated. The OX1 and OX2 derivatives were synthesized from 2,3,3-trimethylindolenin and 1,1,2-trimethylbenz[e]indole, respectively. In addition, two hydroxyl and naphthalene functionalities were applied to both of the OX1 and OX2 derivatives to obtain OX1-OH and OX2-OH and also OX1-Naph and OX2-Naph derivatives, respectively. Investigation of ionochromic properties of oxazolidine derivatives showed their potential applications as highly-selective and sensitive optical chemosensors for detection of metal ions. The results showed colorimetric and fluorometric photodetection of Fe3+ ions in aqueous solution, where OX2-NaPh displayed selective photodetection of Ag+ in addition to Fe3+. For the development of paper-based colorimetric/fluorometric metal ion chemosensors and also high-security anticounterfeiting technology, ionochromic cellulosic papers based on oxazolidine derivatives were prepared via layer-by-layer coating strategy, which showed fluorescence emission in different colors with impregnation in aqueous solution of Fe3+ or Ag+. In addition, the Fe3+ and Ag+ aqueous solutions were used as anticounterfeiting ink for handwriting and printing on the ionochromic papers with pink, cyan blue, and dark blue fluorescence emissions of the written or printed marks. Therefore, the prepared ionochromic cellulosic papers have potential applications as colorimetric/fluorometric metal ion chemosensors and also in anticounterfeiting technology based on ionochromic security papers.

Synthesis and structural analysis of push-pull imidazole-triazole based fluorescent bifunctional chemosensor for Cu2+ and Fe2+ detection

Fluorescent imidazole-triazole based ligands L1 and L2 have been designed as chemical push-pull chemosensors for divalent metal ions and synthesized through palladium-catalyzed cross-coupling reactions using indium organometallics and click chemistry. The novel ligands exhibit intense absorption in the ultraviolet region with high molar extinction coefficients, and strong fluorescence emission with large Stokes displacements. On the basis of UV–Vis absorption spectroscopy and fluorescence emission data in acetonitrile, L1 is shown as a bifuncional chemosensor with differential response for Fe2+ and Cu2+ over a range of selected 3d divalent and other metal ions. The binding site of the ligand was established by single-crystal X-ray diffraction and 1H NMR spectroscopy studies. The association constants, determined by spectrofluorimetric titrations, show a steady binding affinity of L1 for Cu2+ and Fe2+ in comparison with other previously reported fluorescent bidentate chemosensors, offering the lowest limit of detection (LOD) with Cu2+. DFT calculations provide a rationale properly understanding and interpreting the experimentally observed results. Indeed, a mechanism of the different optical responses of L1 towards 3d divalent metal ions is proposed.

Development of highly sensitive metal-ion chemosensor and key-lock anticounterfeiting technology based on oxazolidine

Optical chemosensors and ionochromic cellulosic papers based on oxazolidine chromophores were developed for selective photosensing of metal ions and information encryption as security tags, respectively. The oxazolidine molecules have been displayed highly intense fluorescent emission and coloration characteristics that are usable in sensing and anticounterfeiting applications. Obtained results indicated that oxazolidine molecules can be used for selective detection of pb2+ (0.01 M), and photosensing of Fe3+, Co2+ and Ag+ metal ion solutions by colorimetric and fluorometric mechanisms with higher intensity and sensitivity. Also, oxazolidine derivatives were coated on cellulosic papers via layer-by-layer method to prepare ionochromic papers. Prepared ionochromic papers were used for printing and handwriting of optical security tags by using of metal ion solutions as a new class of anticounterfeiting inks with dual-mode fluorometric and colorimetric securities. The ionochromic cellulosic papers can be used for photodetection of metal ions in a fast and facile manner that presence of metal ions is detectable by naked eyes. Also, key-lock anticounterfeiting technology based on ionochromic papers and metal ion solution as ink is the most significant strategy for encryption of information to optical tags with higher security.

Metal organic frameworks of ethylenediaminetetraacetic acid as chemosensors for heavy metal ions in water

Metal organic frameworks of zinc, copper and manganese with ethylenediaminetetraacetic acid have been synthesised using a solvothermal approach. They have been characterised using IR, PXRD, SEM, EDAX and UV spectral analyses. The efficiency of these MOFs in the sensing of toxic heavy metal ions such as cadmium, lead and chromium was analysed using the changes observed in the UV absorption spectra. Their efficiency in sensing these ions in water having a mixture of these ions have also been analysed.

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.

A terpyridine-based chemosensor for detection transition metal ions in aqueous solution: Synthesis and characterization

A hydrophilic terpyridine-based copolymer chemosensor containing acrylic acid and fluorescence fragments to detect transition metal ions in aqueous solution were synthesized and well characterized. Characteristic color changes, which were resulted from chelating with specific metal ions and visible to the naked eye under natural and ultraviolet light provided possibility for real-time monitoring. Absorption and luminescence properties were adopted for further study, which exhibited unique response when treated with various metal ions. Intensity of absorption peak at 284 nm decreased with the increase of all kinds of metal ions while the secondary absorption peak at 335 nm increased with a certain concentration range. Different metal ions bring fluorescence enhancement or quenching response to the copolymer in aqueous solution. The unique fluorescence enhancing resulting from coordination of terpyridine and Zn2+ endows the polymer excellent detection ability. In particular, owing to metal-ligand charge transfer (MLCT) process, a new absorption peak appeared at 570 nm with the addition of Fe2+, and the polymer showed obvious color change.

A Systematic Review on Fluorescent and Colorimetric Chemosensors for Ion Recognition

The development of fluorescent and colorimetric chemosensors for selective recognition and sensing of cations has received significant attention in recent decades attributed to their diverse applications in the area of environmental and biological sciences. Chemosensors for the detection of different ions offer advantages, such as high selectivity, sensitivity, low cost and rapid response time with versatility. Therefore, a large number of fluorescent/colorimetric chemosensors have been reported for the detection of biologically and environmentally important species. This review introduces the history, provides a general overview of the recent advances in the developments of fluorescent and colorimetric chemosensors, and discusses some innovative and representative works done by our research group and researchers in the field of chemosensors for target metal ions, such as Al3+, Fe3+, Cu2+, Ag+, Cd2+, Hg2+ and Sn2+ over 7 years’ period, from 2013 to 2020.

Specific detection of Cu2+ by a pH-independent colorimetric rhodamine based chemosensor

A new colorimetric “off-on” rhodamine based chemosensor for metal ions (2,4,6-trihydroxybenzaldehyde rhodamine B hydrazone, THB ) was synthesized via Schiff base chemistry between rhodamine B hydrazide and 2,4,6-trihydroxybenzaldehyde. Of all the metal ions tested, it selectively turned pink in the presence of Cu 2+ , and its sensitivity was evaluated. Coordination with Cu 2+ was accompanied by a binding constant of 5.95 × 10 3 M −1 whilst its detection limit is remarkably low (0.48 μM; WHO acceptable limit = 31.5 μM). Moreover, detection of Cu 2+ with THB was independent of pH as pinkish mixture with high absorbance was observed in a wide range from pH 4–12. Consequently, a 1:1 binding ratio of THB to Cu 2+ was verified. Additionally, THB can be reversibly used for up to three times with administration of EDTA and the coordination of THB with Cu 2+ was corroborated by the shifting of carbonyl amide peak in the FT-IR spectra. Then, the prototype of THB as an on-site test kit for detection of Cu 2+ in 100% aqueous condition was also successfully demonstrated. However, THB is weakly cytotoxic against the colorectal adenocarcinoma cell line HT-29 albeit non-toxic towards the non-cancerous colon cell line CCD-18Co (IC 50 via MTT: HT-29 = 39.24 ± 1.59 μM; CCD-18Co > 50.62 μM). Nonetheless, these findings proposed the potential of THB as a simple and feasible sensor in multiple practical applications. • Excellent selectivity of THB towards copper ions. • Wide pH detection range for Cu 2+ . • Versatile application of THB in both acidic and alkaline conditions. • Detection limit of 0.48 μM, well below WHO acceptable levels (31.5 μM). • Application of THB as an on-site testing kit.

Coumarin Grafted Polyethylene Matrix as Colorimetric and Fluorescent Chemosensor for Metal Ions

AbstractA coumarin‐based chemosensor is synthesized and grafted onto a polyethylene (PE) surface by means of gamma radiation. The obtained polymeric film results to work as test‐paper‐like colorimetric sensor for the detection of Cu2+ ions. After immersion of the grafted PE film into a solution of Cu2+ in chloroform/methanol (8/2), a color change from colorless to green is observed by naked eye together with a quenching of the fluorescence emission. Control experiment with methoxy‐grafted PE films shows no response after the immersion in the same Cu2+ solution. The polymeric sensor can be washed and reused over several cycles for the detection of Cu2+. Moreover, the obtained polymeric sensor is used to detect Zn2+ by means of photoinduced electron transfer (PET) quenching disrupting mechanism. The fluorescence emission increases about three times after immersion in a solution containing Zn2+. A similar behavior is observed in the presence of acidic protons.

Metal-Ligand Coordination Induced Ionochromism for π-Conjugated Materials.

Recent studies indicated that the toxicity of heavy metal ions caused a series of environmental, food, and human health problems. Chemical ionochromic sensors are crucial for detecting these toxicity ions. Incorporating organic ligands into π-conjugated polymers made them receptors for metal ions, resulting in an ionochromism phenomenon, which is promising to develop chemosensors for metal ions. This review highlights the recent advances in π-conjugated polymers with ionochromism to metal ions, which may guide rational structural design and evaluation of chemosensors.

Synthesis of Nitrogen Containing Chalcone: A Highly Sensitive and Selective Fluorescent Chemosensor for the Fe3+ Metal Ion in Aqueous Media

Title compound (PTPO) was synthesized by the reaction of 2-acetyl pyridine with 3,4,5-trimethoxy benzaldehyde. The structure of the compound has been confirmed by spectroscopic techniques. Interaction of chalcone with different metal cations was analyzed based on the fluorescence behavior. Results show that chalcone act as on-off switching fluorescent chemosensor for selective and sensitive detection iron metal ion. Mechanism of quenching and complexation were resolute by Benesi-Hildebrand, Stern-Volmer plot and Job-plot.

Novel spiropyran derivative based reversible photo-driven colorimetric and fluorescent probes for recognizing Fe3+, Cr3+ and Al3+ metal ions

A novel spiropyran derivative, 3-(5-methoxy-6′-nitro-3H-spiro[benzo[d]thiazole-2,2′-chromen]-3-yl)propane-1-sulfonate (MO-SP) as a chemosensor for metal ions has been synthesized. The prepared MO-SP as a colorimetric and fluorescent sensor is sensitive to common trivalent metal ions (Al3+, Cr3+ and Fe3+). In addition, it can be used as a “naked eye” identification agent of Fe3+, Cr3+ and Al3+. When Fe3+, Cr3+ or Al3+ was added, the color changed from orange to yellow, meanwhile, the absorbance at the maximum absorption wavelength decreased obviously, but it did not change significantly when other metal ions were added. The MO-SP is proved to be sensitive, selective, good linear-relationship and low detection limit for recognition of Fe3+, Cr3+ and Al3+. Moreover, the MO-SP also could be employed as molecular logic function.

Multi-step synthesis, photophysical and physicochemical investigation of novel pyrazoline a heterocyclic D- π -A chromophore as a fluorescent chemosensor for the detection of Fe3+ metal ion

The title compound has been 2-(1-(benzo[d]thiazol-2-yl)-5-(3,4-dimethoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl)phenol (BTDP) synthesized by reaction of (E)-3-(3,4-dimethoxyphenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (DMPO) with 2-Hydrazinylbenzo[d]thiazole. DMPO was synthesized by the reaction of 1-(2 hydroxyphenyl)ethan-1-one with 3,4-dimethoxybenzaldehyde. Structure of compound has been confirmed by the elemental analysis and spectroscopic techniques (FT-IR, 1H NMR and 13C NMR). Photophysical properties of the BTDP such as absorption, emission, stokes shift, transition dipole moments and fluorescence quantum yield have been studied in various solvents of different polarity and chromophore demonstrated positive solvatochromism. The chromophore undergoes micellization in two different micelles and its can be used as probe to determine the critical micelle concentration of surfactant such as CTAB and SDS. In addition, Pyrazoline derivative used as fluorescent chemosensor for metal ion selectively based on fluorometric detraction and pyrazoline displayed as on-off fluorescence chemosensor for the determination of Fe3+ ion in solution. Hildebrand, Stern-Volmer and job’s plot method has described quenching behavior of chromophore with Fe3+ ion.