Ratiometric Chemosensor Research Articles

Development of a cell permeable ratiometric chemosensor and biomarker for hydrogen sulphate ions in aqueous solution

A newly designed benzimidazol-based water soluble ratiometric chemosensor selective for HSO4− ions behaves as an efficient biomarker for the detection of the distribution of HSO4− ions in living cells in HEPES buffer (1 mM; water : ethanol (v/v), 98 : 2).

A pyrene thiazole conjugate as a ratiometric chemosensor with high selectivity and sensitivity for tin (Sn4+) and its application in imaging live cells

A new pyrene thiazole-conjugate amine based fluoroionophore, PTC was developed for ratiometric detection of Sn4+ ion in organo-aqueous medium.

Direct evidence of a blocking heavy atom effect on the water-assisted fluorescence enhancement detection of Hg(2+) based on a ratiometric chemosensor.

At the current stage of chemosensor chemistry, the critical question now is whether the heavy atom effect caused by HTM ions can be blocked or avoided. In the present work, we provide unequivocal evidence to confirm that the heavy atom effect of Hg(2+) is inhibited by water and other solvent molecules based on results using the chemosensor L. Most importantly, the heavy atom effect and blocking thereof were monitored within the same system by the use of ratiometric fluorescence signal changes of the pyrene motif. These observations not only serve as the foundation for the design of new 'turn-on' chemosensors for HTM ions, but also open up new opportunities for the monitoring of organic reactions.

A water soluble FRET-based ratiometric chemosensor for Hg(ii) and S2−applicable in living cell staining

A new water soluble rhodamine-based ratiometric dual ‘off–on–off’ probe can selectively detect Hg2+ions in ppb level through time dependent FRET process with reversibility in presence of S2−anions.

A FRET-based ‘off–on’ molecular switch: an effective design strategy for the selective detection of nanomolar Al3+ ions in aqueous media

A FRET-based ratiometric chemosensor (L1) is highly selective for Al3+ ions (as low as 6.19 × 10−9 M) and could be used to acquire images of Al3+ ions in living cells.

A quinazoline derivative as quick-response red-shifted reporter for nanomolar Al3+and applicable to living cell staining

A newly designed and structurally characterized non-cytotoxic quinazoline based ratiometric chemosensor (L) selectively detects Al3+ions upto 1.48 nM through ICT and CHEF processes in water–DMSO (9 : 1, v/v) and it is also applicable in living cell staining.

Reaction‐Based Ratiometric Chemosensor for Instant Detection of Cyanide in Water with High Selectivity and Sensitivity

A highly selective chemosensor 1 based on an acylhydrazone group as binding site and naphthalene group as the fluorescence signal group were described, which could instantly detect CN(-) in water with specific selectivity and high sensitivity. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the carbonyl group, which could be confirmed by (1)H NMR, (13)C NMR, ESI-MS and DFT calculations. The addition of CN(-) to sensor 1 induced a remarkable color change from colorless to yellow and generated a blue fluorescence, these sense procedure could not interfered by other coexistent competitive anions (F(-), Cl(-), Br(-), I(-), AcO(-), H2PO4(-), HSO4(-), ClO4(-), SCN(-), S(2-), NO3(-) and SO4(2-)). The detection limits were 5.0×10(-7) M and 2.0×10(-9) M of CN(-) using the visual fluorescent color changes and fluorescence spectra changes respectively, which is far lower than the WHO guideline of 1.9×10(-6) M. Test strips based on sensor 1 were fabricated, which could act as a convenient and efficient CN(-) test kit to detect CN(-) in pure water for "in-the-field" measurement.

Efficient FRET-based colorimetric and ratiometric fluorescent chemosensor for Al3+ in living cells

In this paper, we have developed the first example for colormetric and ratiometric fluorescent detection of Al3+ based on naphthalimide-rhodamine compound (1a). The ratiometric fluorescent signal change of the chemosensor is on the basis of FRET Off-On mechanism modulated by Al3+ induced configuration transformation of the rhodamine from a spirolactam ring to the ring-opened amide. In comparison with the fluorescent chemosensors based on single emission intensity change, ratiometric chemosensors are beneficial for increasing the dynamic response range and providing built-in correction for environmental effects. Under optimized experimental conditions, the chemosensor exhibits a stable response for Al3+ over a concentration range from 5.0×10−7 to 1.0×10−5M, with a detection limit of 1.0×10−7M. The experiment results show that the response behavior of 1a toward Al3+ is pH independent in medium condition (pH 6.0–8.0). Moreover, the fluorescence changes of the chemosensor are remarkably specific for Al3+ in the presence of other metal ions except Mn2+, which can meet the selective requirements for practical application. In addition, the chemosensor was successfully applied for ratiometric visualization of Al3+ in living cells.

Rhodamine–pyrene conjugated chemosensors for ratiometric detection of Hg2+ ions: Different sensing behavior between a spirolactone and a spirothiolactone

Abstract Two novel rhodamine–pyrene conjugated chemosensors were successfully designed and synthesized, which exhibited high affinity to Hg2+ ions. As ratiometric chemosensors, each displayed highly selective and sensitive colorimetric and fluorogenic dual-responses toward Hg2+. The comparison of two chemosensors indicated that the spirothiolactone containing sensor was superior to the spirolactone analog in sensing behavior when detecting Hg2+, presumably due to the thiophilic nature of mercury and the different sensing mechanisms in operation. Upon interaction with Hg2+, the spirothiolactone showed a 1:1 stoichiometry for the Hg2+ complex, accompanied with a weakened fluorescence resonance energy transfer (FRET) behavior. However, the spirolactone was hydrolyzed and consequently induced the monomer–excimer switch of the resulted pyrene in the presence of Hg2+ ions.

A ratiometric fluorescent sensor for selective recognition of Al3+ ions based on a simple benzimidazole platform

An efficient new ratiometric chemosensor, 6-imidazo-2-yl-5,6-dihydro-benzo[4,5]imidazo[1,2-c]quinazoline (PB), which enables selective sensing of Al3+ in aqueous DMSO was synthesized by a facile one step condensation reaction of imidazole-2-carboxaldehyde with 2-(2-aminophenyl)-1H-benzimidazole. The probe PB was characterized by elemental analysis, 1H and 13C NMR, ESI-MS and IR spectral techniques. Upon addition of Al3+, the fluorescent probe PB induces ratiometric responses in both absorption and fluorescence spectra on the basis of a charge transfer mechanism. The receptor PB serves for highly selective, sensitive and ratiometric detection of Al3+ without the interference of biologically and environmentally relevant cations. The detection limit is found to be 5.3 × 10−7 M. The Job's plot analysis indicates the binding stoichiometry of the complex to be 1 : 1 (host/guest).

Thin-film ratiometric fluorescent chemosensors with tunable performance characteristics

A simple method for tuning the performance characteristics of fluorescent ratiometric sensors based on surface-immobilized monolayers of π-conjugated molecules enabled gradual adjustment of the sensitivity and the analyte detection range of the sensor. This approach has been applied to fine-tune the sensing performance of a prototype ratiometric chemosensor for fluoride ions.

Synthesis and spectroscopic–electrochemical properties of novel ratiometric Hg (II) chemosensor containing Bodipy and the N-phenylaza-15-crown-5 moiety

The aryl-amine containing azacrown ether ring and alkyl-chloro boradiazaindacene (Bodipy) were synthesized by the Schiff base condensation. The absorption and emission of a novel Schiff base derivative (based on azacrown–Bodipy) were performed in presence of different cations such as Zn2+, Ga3+, Pb2+, Hg2+, NH4+ Ca2+, Cu2+, Na+, Ni2+, Cd2+ and Cr3+. The complexation property of the Schiff base was studied in dimethylformamide (DMF) by interacting azacrown-ether group and transition metal nitrates–ammonium chloride. The electrochemical behavior of the Schiff base has also been investigated by cyclic voltammetry. All experimental results indicated that the new compound acts as a selective ratiometric chemosensor for Hg2+.

Tricolor Emission of a Fluorescent Heteroditopic Ligand over a Concentration Gradient of Zinc(II) Ions

The internal charge transfer (ICT) type fluoroionophore arylvinyl-bipy (bipy = 2,2'-bipyridyl) is covalently tethered to the spirolactam form of rhodamine to afford fluorescent heteroditopic ligand 4. Compound 4 can be excited in the visible region, the emission of which undergoes sequential bathochromic shifts over an increasing concentration gradient of Zn(ClO(4))(2) in acetonitrile. Coordination of Zn(2+) stabilizes the ICT excited state of the arylvinyl-bipy component of 4, leading to the first emission color shift from blue to green. At sufficiently high concentrations of Zn(ClO(4))(2), the nonfluorescent spirolactam component of 4 is transformed to the fluorescent rhodamine, which turns the emission color from green to orange via intramolecular fluorescence resonance energy transfer (FRET) from the Zn(2+)-bound arylvinyl-bipy fluorophore to rhodamine. While this work offers a new design of ratiometric chemosensors, in which sequential analyte-induced emission band shifts result in the sampling of multiple colors at different concentration ranges (i.e., from blue to green to orange as [Zn(2+)] increases in the current case), it also reveals the nuances of rhodamine spirolactam chemistry that have not been sufficiently addressed in the published literature. These issues include the ability of rhodamine spirolactam as a fluorescence quencher via electron transfer, and the slow kinetics of spirolactam ring-opening effected by Zn(2+) coordination under pH neutral aqueous conditions.

A new colorimetric and fluorescent ratiometric sensor for Hg2+ based on 4-pyren-1-yl-pyrimidine

A novel fluorescent ratiometric chemosensor based on 4-pyren-1-yl-pyrimidine (PPM) has been designed and prepared for the detection of Hg2+ in the presence of other competing metal ions in acetonitrile. The photo exhibits fluorescence color change of PPM from blue to green without and with Hg2+, which red shift of wavelength about 105nm in fluorescence emission spectra. It can serve as a highly selective chemodosimeter for Hg2+ with ratiometric and naked-eye detection. The photophysical properties of PPM confirmed a 2:1 (PPM–Hg2+) binding model and the spectral response toward Hg2+ was proved to be reversible.

Rational Design of a Dual Chemosensor for Cyanide Anion Sensing Based on Dicyanovinyl-Substituted Benzofurazan

A dicyanovinyl-substituted benzofurazan derivative (C1) was prepared as an efficient ratiometric chemosensor for cyanide anion detection in aqueous acetonitrile solution. Mechanism studies suggested that the nucleophilic addition of cyanide to the α-position of the dicyanovinyl group blocked the ICT progress of C1 and induced remarkable emission and absorption shift.

Synthesis in aqueous solution and characterisation of a new cobalt-doped ZnS quantum dot as a hybrid ratiometric chemosensor

In this paper, cobalt (Co 2+)-doped (CoD) ZnS quantum dots (QDs) are synthesised in aqueous solution and characterised for the first time. l-Cysteine ( l-Cys) ligands on the surface of CoD ZnS QDs can bind 2,4,6-trinitrotoluene (TNT) to form Meisenheimer complexes (MHCs) mainly through acid–base pairing interactions between TNT and l-Cys and the assistance of hydrogen bonding and electrostatic co-interactions among l-Cys intermolecules. The aggregation of inter-dots induced by MHCs greatly influenced the light scattering property of the QDs in aqueous solution, and Rayleigh scattering (RS) enhancement at the defect-related emission wavelengths as well as its left side was observed with the excitation of CoD ZnS QDs by violet light. RS enhancement, combining with the quenching of the orange transition emission induced by TNT anions, resulted in a change in the ratiometric visualisation of the system being investigated. A novel CoD ZnS QD-based hybrid ratiometric chemosensor has therefore been developed for simple and sensitive analysis of TNT in water. This ratiometric probe can assay down to 25 nM TNT in solution without interference from a matrix of real water sample and other nitroaromatic compounds. Because of the excellent electron-accepting ability and strong affinity of TNT to l-Cys on the surface of CoD ZnS QDs, the CoD photoluminescent nanomaterials reported here are well suited for detecting ultra-trace TNT and for distinguishing different nitro-compounds in aqueous solution.

An FRET-based ratiometric chemosensor for in vitro cellular fluorescence analyses of pH

Ratiometric fluorescence sensing is an important technique for precise and quantitative analysis of biological events occurring under complex conditions by simultaneously recording fluorescence intensities at two wavelengths and calculating their ratios. Herein, we design a ratiometric chemosensor for pH that is based on photo-induced electron transfer (PET) and binding-induced modulation of fluorescence resonance energy transfer (FRET) mechanisms. This ratiometric chemosensor was constructed by introduction of a pH-insensitive coumarin fluorophore as an FRET donor into a pH-sensitive amino-naphthalimide derivative as the FRET acceptor. The sensor exhibited clear dual-mission signal changes in blue and green spectral windows upon pH changes. The pH sensor was applied for not only measuring cellular pH, but also for visualizing stimulus-responsive changes of intracellular pH values.

A specific and ratiometric chemosensor for Hg 2+ based on triazole coupled ortho-methoxyphenylazocalix[4]arene

Calix[4]arene 3, which contains two distal triazole groups on the lower rim and two distal o-methoxyphenylazo groups on the upper rim, was synthesized and found to be a specific and ratiometric sensor for Hg 2+ in a polar protic solvent. A series of o-methoxyphenylazo derivatives ( 3, 4, 5, 7, and 9) were synthesized, which proved that the lower-rim triazoles and the hydroxyl azophenol(s) were the major ligands for metal ion binding. Though analogues 4 and 10 showed some sensitivity for Hg 2+, compound 3 was the only ratiometric chemosensor for Hg 2+ among the series of azocalix[4]arenes synthesized in this work. The formation of 3·Hg 2+ complex was supported by UV/vis and NMR titration studies and Mass spectrometry. Based on the symmetrical features of NMR spectra of 3·Hg 2+, the complex is believed to be symmetrical with respect to the calix[4]arene cavity. Furthermore, the complex was determined to be 1:1 binding stoichiometry by Job’s plot, and the association constant was determined to be 4.02×10 3 M −1 using Benesi–Hildebrand plot.

Ratiometric fluorescent Zn 2+ chemosensor constructed by appending a pair of carboxamidoquinoline on 1,2-diaminocyclohexane scaffold

By appending a pair of carboxamidoquinoline pendants onto 1,2-diaminocyclohexane scaffold via N-alkylation, multifunctionalized ACAQ was designed and synthesized as a water soluble fluorescent ratiometric chemosensor for Zn 2+. In 50% aqueous methanol buffer pH 7.4 solution, upon excitation at 316 nm, ACAQ (5 μM) displayed a selective ratiometric fluorescence changes with a shift from 410 to 490 nm in response to the interaction with Zn 2+. After binding with 1 equiv of Zn 2+, ACAQ exhibited a 12-fold enhancement in I 490/I 410 characterized by a clear isoemissive point at 440 nm. The metal sensor binding mode was established by Job’s plot and the combined fluorescence and 1H NMR spectroscopic method. The selectivity of the probe toward biological relevant cations and transition metal ions was proven to be good. In addition, the interference caused by Cu 2+ and Cd 2+ in the quantitation of Zn 2+ can be completely eliminated by the use of diethyldithiocarbamate as the screening agent. Exploitation of ACAQ as the sensing probe, ratiometric determination of Zn 2+ with the limit of detection (LOD) at 28.3 nm can be realized. In addition, the unique responsive properties of the probe toward Fe 3+ and Zn 2+ were used to construct a fluorescent switch. The membrane permeability of ACAQ to living cells and bio-imaging of Zn 2+ were demonstrated.

A simple coumarin-based colorimetric and ratiometric chemosensor for acetate and a selective fluorescence turn-on probe for iodide

A novel colorimetric and ratiometric anion chemosensor bearing phenylhydrazone- coumarin moieties as recognition sites was rationally designed and synthesized. Upon addition of a series of anions to receptor R1 in 1:1 CH 3CN/H 2O, only the appearance of the solution of receptor R1 with acetate showed a color change from pale yellow to purple (bathochromic shift from 411 to 573 nm) which can be detected by the naked eye at parts per million. The probe R1 developed herein represents the rational design of a fluorescence turn-on probe for iodide, which is a notorious fluorescence quencher due to the heavy atom effect. The probe developed herein represents the fluorescence amplified probe for iodide.