Ratiometric Fluorescent Chemosensor Research Articles

A ratiometric fluorescence chemosenser for Hg2+ based on Primuline and layered double hydroxide ultrafilms

The fabrication of fluorescence indicator/layered double hydroxide (LDH) ultrathin films (UTFs) by alternate assembly of Primuline and Mg-Al LDH nanosheets using the layer-by-layer (LBL) deposition technique has been reported, and their application as a raitometric fluorescence chemosensor for Hg2+ is demonstrated. The Primuline/LDH UTFs show a stepwise and regular growth of upon increasing deposition cycles proved by UV–vis absorption and fluorescence emission spectroscopy, and a periodical layered structure perpendicular to the substrates with a thickness of 2.41–2.48nm per bilayer observed by X-ray diffraction and scanning electron microscopy. Furthermore, a linear correlation between the fluorescence intensity ratio (I422/I377) of the UTF and the concentration of Hg2+ is obtained (I422/I377=2.63–0.01c nM, r2=0.99), with a detection limit of 0.13pM. The results have also exhibited that the ratiometric fluorescence chemosensor possess a good repeatability, high stability (light, storage and mechanics) as well as excellent selectivity. In addition, the mechanism of measurement–regeneration cycle for the ratiometric fluorescence chemosensor indicates Hg2+ enters/departs from the Primuline/LDH UTF giving rise to reversible change in chemical composition, surface morphology and fluorescence anisotropy of the UTF. Therefore, this work provides new opportunities for fabrication and application of chromophore/LDH UTFs as ratiometric fluorescence chemosensors.

Surface‐Immobilized Monolayers of Conjugated Oligomers as a Platform for Fluorescent Sensors Design: The Effect of Exciton Delocalization on Chemosensing Performance

Surface-immobilized monolayers of fluorescent molecular sensors consisting of a short conjugated oligo(p-phenylene ethynylene) core end-capped with an acceptor fluorophore (analyte receptor) display significant signal amplification due to enhanced intermolecular energy transfer within the monolayer. This general phenomenon offers a superior platform for designing ratiometric fluorescent sensors. An example of how this can be used to convert a narrow-range threshold fluorescent pH indicator (fluorescein) to a broad-range ratiometric fluorescent chemosensor is described.

A DFT study of pyrrole-isoxazole derivatives as chemosensors for fluoride anion.

The interactions between chemosensors, 3-amino-5-(4,5,6,7-tetrahydro-1H-indol-2-yl)isoxazole-4-carboxamide (AIC) derivatives, and different anions (F− Cl−, Br−, AcO−, and H2PO4−) have been theoretically investigated using DFT approaches. It turned out that the unique selectivity of AIC derivatives for F− is ascribed to their ability of deprotonating the host sensors. Frontier molecular orbital (FMO) analyses have shown that the vertical electronic transitions of absorption and emission for the sensing signals are characterized as intramolecular charge transfer (ICT). The study of substituent effects suggests that all the substituted derivatives are expected to be promising candidates for fluoride chemosensors both in UV-vis and fluorescence spectra except for derivative with benzo[d]thieno[3,2-b]thiophene fragment that can serve as ratiometric fluorescent fluoride chemosensor only.

Design and Synthesis of a Ratiometric Fluorescent Chemosensor for Cu(II) with a Fluorophore Hybridization Approach

A new ratiometric fluorescent sensor for Cu(2+), WLN, has been developed via integrating a 1,8-naphthalimide fluorophore with 8-aminoquinoline. WLN exhibits a highly selective ratiometric response to Cu(2+) over other transition metal ions in aqueous media. Moreover, its practical ratiometric imaging ability for intracellular Cu(2+) has been confirmed in human breast adenocarcinoma cells (MCF-7 cells) using a confocal microscope.

Theoretical study of chemosensor for fluoride anion and optical properties of the derivatives of diketopyrrolopyrrole

The interactions between chemosensors, diketopyrrolopyrrole (DPP) derivatives, and different halides (F−, Cl−, and Br−) anions have been theoretically investigated using DFT approaches. Theoretical investigations have been performed to explore the optical, electronic, charge transport, and stability properties of DPP derivatives as charge transport and/or luminescent materials. It turned out that the unique selectivity of DPP derivatives for F− is ascribed to their ability of deprotonating the host sensors. The atoms in molecules theory and natural bond orbitals charge analysis of the complexes consisting of DPP derivatives and X− (X = F, Cl, and Br) confirm that the protons are almost completely abstracted by F−. The study of substituent effects suggests that all the substituted derivatives are expected to be promising candidates for ratiometric fluorescent fluoride chemosensors as well as chromogenic chemosensors. Furthermore, the derivatives with biphenyl, 2-(thiophen-2-yl)thiophene, and benzo[d]thieno[3,2-b]thiophene fragments are expected to be promising luminescent materials. In addition, derivatives with 2-(thiophen-2-yl)thiophene and 4,9-dihydrothieno[3,4-b]quinoxaline fragments can serve as good electron transport materials for OLEDs as well.

A highly selective fluorescent chemosensor for Ag+ based on calix[4]arene with lower-rim proximal triazolylpyrenes

Ligand 3, a calix[4]arene with lower-rim proximal triazolylpyrenes, is a ratiometric fluorescent chemosensor for Ag+ with higher sensitivity compared to ligand 5, a calix[4]arene with lower-rim distal triazolylpyrenes, and the conventional fluoroionophore with non-conjugated triazole and pyrene. In a polar protic solvent, the binding ratios for 3·Ag+ was determined to be 1:1 and the association constant was found to be 7.0 × 103 M−1. The detection of Ag+ by ligand 3 even works in aqueous methanol solution.

A highly selective ratiometric fluorescent chemosensor for Zn2+ ion based on a polyimine macrocycle

A new ratiometric fluorescent chemosensor based on a polyimine macrocycle ligand 1 has been synthesized. The chemosensor can exhibit a pronounced fluorescence response and high selectivity to Zn2+ ion over other 15 metal ions, including Cd2+. Sensor 1 appears an emission peak at 370 nm. Upon the addition of Zn2+ ion, the typical emission peak for 1 at 370 nm is obviously quenched, but a new emission peak at around 470 nm appears and shows a large enhancement due to the formation of a 1:1 Zn2+-1 complex. In addition, there is a good linear relationship between the fluorescence ratio I470nm/I370nm and the concentration of Zn2+, which makes a ratiometric assay of Zn2+ ion possible.

Synthesis of a ratiometric fluorescent peptide sensor for the highly selective detection of Cd2+

A novel ratiometric fluorescent peptidyl chemosensor (Dansyl-Cys-Pro-Gly-Cys-Trp-NH2, D-P5) for metal ions detection has been synthesized via Fmoc solid-phase peptide synthesis. The chemosensor exhibited a high selectivity for Cd2+ over other metal ions including competitive transition and Group I and II metal ions in neutral pH. The fluorescence emission intensity of D-P5 was significantly enhanced in the presence of Cd2+ by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The binding stoichiometry, detection limit, binding affinity, reversibility and pH sensitivity of the sensor for Cd2+ were investigated.

Ratiometric Fluorescent Chemosensor for Hg2+ Based on Heptamethine Cyanine Containing a Thymine Moiety

Based on a T-Hg(2+)-T binding mode, a sensitive ratiometric fluorescent chemosensor for aqueous Hg(2+) was developed with a heptamethine cyanine chromophore containing a thymine moiety.

Colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on perylene diimide derivatives

Based on a perylene diimide derivatives(PDIs) platform, AM-PDIs was rationally designed and synthesized as a new colorimetric and ratiometric fluorescent sensor for naked-eye detection of fluoride ion with high selectivity over other halide ions. Addition of fluoride ion to a dichloromethane(DCM) solution of AM-PDIs resulted in an obvious color change (from red to blackish green) because of a large red shift (151 nm) in absorption. The recognition mechanism was attributed to the intermolecular proton transfer between a hydrogen atom on the amide N position of sensor and the fluoride anion. The detection limit was calculated to be 0.14 μM.

A boron-containing carbazole dimer: synthesis, photophysical properties and sensing properties

A novel boron-containing π-conjugated compound has been synthesized by the introduction of electron-acceptors (dimesitylboron groups) at the 3,3'-positions of a carbazole dimer (electron-donor). The compound possesses excellent electrochemical properties and high fluorescence quantum yields. In addition, is a sensitive fluorescence sensor with remarkable colour changes and the results could be confirmed through theoretical calculations of the compounds and [(n)Bu(4)N](+)(2)[·(F)(2)](2-). Our studies indicate that could be used as an excellent optoelectronic material in OLED devices and a ratiometric fluorescent chemosensor.

A heptamethine cyanine-based colorimetric and ratiometric fluorescent chemosensor for the selective detection of Ag+ in an aqueous medium

A highly selective and sensitive ratiometric fluorescent chemosensor for Ag(+) in aqueous solution was developed, in a linear range of 0.6 × 10(-7) to 50 × 10(-7) mol L(-1), based on a A-Ag(+)-A binding mode with a heptamethine cyanine motif containing one adenine moiety.

A ratiometric fluorescent chemosensor for iron: discrimination of Fe2+ and Fe3+ and living cell application

A newly designed probe, 6-thiophen-2-yl-5,6-dihydrobenzo[4,5]imidazo-[1,2-c] quinazoline (HL(1)) behaves as a highly selective ratiometric fluorescent sensor for Fe(2+) at pH 4.0-5.0 and Fe(3+) at pH 6.5-8.0 in acetonitrile-HEPES buffer (1/4) (v/v) medium. A decrease in fluorescence at 412 nm and increase in fluorescence at 472 nm with an isoemissive point at 436 nm with the addition of Fe(2+) salt solution is due to the formation of mononuclear Fe(2+) complex [Fe(II)(HL)(ClO(4))(2)(CH(3)CN)(2)] (1) in acetonitrile-HEPES buffer (100 mM, 1/4, v/v) at pH 4.5 and a decrease in fluorescence at 412 nm and increase in fluorescence at 482 nm with an isoemissive point at 445 nm during titration by Fe(3+) salt due to the formation of binary Fe(3+) complex, [Fe(III)(L)(2)(ClO(4))(H(2)O)] (2) with co-solvent at biological pH 7.4 have been established. Binding constants (K(a)) in the solution state were calculated to be 3.88 × 10(5) M(-1) for Fe(2+) and 0.21 × 10(3) M(-1/2) for Fe(3+) and ratiometric detection limits for Fe(2+) and Fe(3+) were found to be 2.0 μM and 3.5 μM, respectively. The probe is a "naked eye" chemosensor for two states of iron. Theoretical calculations were studied to establish the configurations of probe-iron complexes. The sensor is efficient for detecting Fe(3+)in vitro by developing a good image of the biological organelles.

First theophylline-based ratiometric fluorescent synthetic receptor for selective recognition of dihydrogenphosphate and biological phosphate ions

We have developed a new ratiometric fluorescent chemosensor 1 based on xanthine alkaloid theophylline moiety for the detection of dihydrogen phosphate and ATP. The chemosensor 1 selectively recognizes tetrabutylammonium dihydrogen phosphate in CH(3)CN/H(2)O (9:1) by exhibiting a significant decrease in the emission of naphthalene and its sensing properties regarding ATP and other related phosphate species were evaluated. The anion binding properties of 1 were evaluated by (1)H NMR, UV-vis, and fluorescence spectroscopic methods.

New regioisomeric naphthol-substituted thiazole based ratiometric fluorescence sensor for Zn 2+ with a remarkable red shift in emission spectra

Ratiometric fluorescent chemosensors based on the position of ring annulation of the naphthol–thiazole moiety for quantification of zinc ions in aqueous ethanol were synthesized and investigated. It was found that sensor 3 exhibited a remarkably large red shift of 140 nm in emission upon complexation with Zn 2+. A TD-B3LYP/6-31G (d,p) calculation was performed to characterize the nature of the fluorescence behavior of sensor 3 upon Zn 2+ complexation. The combination of experimental and computational analyses provides a more complete understanding of the molecular level origin of these unique photophysical properties of this type of chemosensor.

Colorimetric and Ratiometric Fluorescent Chemosensor Based on Diketopyrrolopyrrole for Selective Detection of Thiols: An Experimental and Theoretical Study

A colorimetric and ratiometric fluorescent thiol probe was devised with diketopyrrolopyrrole (DPP) fluorophore. The probe gives absorption and emission at 523 and 666 nm, respectively. In the presence of thiols, such as cysteine, the absorption and emission band shifted to 479 and 540 nm, respectively. Correspondingly, the color of the probe solution changed from purple to yellow, and the fluorescence changed from red to yellow. The emission intensity at 540 nm was enhanced by 140-fold. The Stokes shift of probe 1 (107 nm) is much larger than the unsubstituted DPP fluorophore (56 nm). Mass spectral analysis demonstrated that besides the expected Michael addition of thiols to the C═C bonds, the CN groups of the malonitrile moieties also react with thiols to form 4,5-dihydrothiazole structure. Probe 1 was used for fluorescence imaging of intracellular thiols. In the presence of thiols, both the green and red channel of the microscopy are active. With removal of the intracellular thiols, signal can only be detected through the red channel; thus, ratiometric bioimaging of intracellular thiols was achieved. The ratiometric response of probe 1 was rationalized by DFT calculations. Our complementary experimental and theoretical studies will be useful for design of ratiometric/colorimetric molecular probes.

Analyte-Reactive Amphiphilic Thermoresponsive Diblock Copolymer Micelles-Based Multifunctional Ratiometric Fluorescent Chemosensors

We report on the fabrication of amphiphilic thermoresponsive diblock copolymer micelle-based multifunctional ratiometric fluorescent chemosensors for metal ions (Hg2+ and Cu2+), pH, and temperature...

Fluorescent Chemosensors for Chromium(III) Ions and the Cr3+/Cr2+ Ratio

Abstract The shielded linear trisphenanthroline 1 is utilized as a triple reassurance probe and as an ON–OFF–ON signaling unit (after addition of Cu2+) for the detection and quantification of Cr3+ ions. The analogous monophenanthroline 2 served as a ratiometric fluorescent chemosensor for analyzing the Cr3+/Cr2+ ratio.

Ratiometric Fluorescent Chemosensor for Silver Ion at Physiological pH

Bis-pyrene derivative 1, bearing two pyrene and pyridine groups, was synthesized as a ratiometric fluorescent chemosensor for Ag(+) in aqueous solution. Fluorescent chemosensor 1 displayed a selective ratiometric change with Ag(+), which was attributed to the excimer-monomer emissions of pyrenes. A mechanism for the binding mode was proposed based on fluorescence changes, NMR experiments, and theoretical calculations.

Development of a highly selective cell-permeable ratiometric fluorescent chemosensor for oxorhenium(v) ion

A novel 6-(2-pyridinyl)-5,6-dihydrobenzimidazo[1,2-c]quinazoline (HL) serves as a first-time highly selective and sensitive ratiometric fluorescent chemosensor probe for oxorhenium (ReO(V)) ion in acetonitrile : water = 9 : 1 (v/v) at 25 °C. The decrease in fluorescence at 410 nm and increase in fluorescence at 478 nm with an isoemissive point at 444 nm in the presence of ReO(V) ion is accounted for by the formation of mononuclear [ReOL(2)Cl] complex, characterized by physico-chemical and spectroscopic tools. The fluorescence quantum yield of the chemosensor (HL) was only 0.198 at 410 nm, and it increased more than 3-fold in the presence of 2 equiv. of the ReO(V) ion at 478 nm. Interestingly, the introduction of other metal ions and relevant anions caused the fluorescence intensity at 478 nm to be either unchanged or weakened. The fluorescence-response fits a Hill coefficient of 2.088 indicates the formation of a 1 : 2 stoichiometry for the L-ReO(V) complex. In the concentration range of 0-20 μM of oxorhenium(V) species calibration graph was linear with correlation coefficient (R) of 0.99994 and the calibration sensitivity was found to be 4.0 × 10(-7) M. The cellular image in the confocal microscope clearly indicated the presence of ReO(V) in Candida albicans cells using this chemosensor (HL).