Selective Fluoroionophore Research Articles

Sodium-Selective Fluoroionophore-Based Optodes for Seawater Salinity Measurement.

A new fluorescent sensor for Na+ is presented. The sensor relies on a Na+ selective fluoroionophore based on a bright red-emitting BODIPY chromophore. The fluorescence of the fluoroionophore is enhanced upon binding of Na+-ions to the highly selective aza-crown ether receptor due to reduction of the photoinduced electron transfer (PET) quenching. Solid state sensing materials were prepared by physically embedding the fluoroionophore into water-swellable biocompatible polymer matrices (polyurethane hydrogels), thus enabling continuous measurements of aqueous samples. Despite the simple design, the sensor showed no leaching of the indicator and featured fast and reversible response. Among different polyurethane hydrogels investigated, the hydrogel D1 featuring the highest water uptake was found to be the most suitable due to the highest dynamics between "off" and "on" states. Due to little or no cross sensitivity to other ions (e.g., Mg2+, Ca2+, K+) and its insensitivity to potential changes in pH, this sensor is promising for use in clinical diagnostics and for biological and marine applications. Fiber-optic sensors based on referenced read-out with a compact phase fluorimeter were prepared. To demonstrate their practical applicability, the sensors were used to determine the salinity in the seawater and brackish water of the Baltic Sea.

Design of Na+ -Selective Fluorescent Probes: A Systematic Study of the Na+ -Complex Stability and the Na+ /K+ Selectivity in Acetonitrile and Water.

There is a tremendous demand for highly Na+ -selective fluoroionophores to monitor the top analyte Na+ in life science. Here, we report a systematic route to develop highly Na+ /K+ selective fluorescent probes. Thus, we synthesized a set of fluoroionophores 1, 3, 4, 5, 8 and 9 (see Scheme ) to investigate the Na+ /K+ selectivity and Na+ - complex stability in CH3 CN and H2 O. These Na+ -probes bear different 15-crown-5 moieties to bind Na+ stronger than K+ . In the set of the diethylaminocoumarin-substituted fluoroionophores 1-5, the following trend of fluorescence quenching 1>3>2>4>5 in CH3 CN was observed. Therefore, the flexibility of the aza-15-crown-5 moieties in 1-4 determines the conjugation of the nitrogen lone pair with the aromatic ring. As a consequence, 1 showed in CH3 CN the highest Na+ -induced fluorescence enhancement (FE) by a factor of 46.5 and a weaker K+ induced FE of 3.7. The Na+ -complex stability of 1-4 in CH3 CN is enhanced in the following order of 2>4>3>1, assuming that the O-atom of the methoxy group in the ortho-position, as shown in 2, strengthened the Na+ -complex formation. Furthermore, we found for the N-(o-methoxyphenyl)aza-15-crown-5 substituted fluoroionophores 2, 8 and 9 in H2 O, an enhanced Na+ -complex stability in the following order 8>2>9 and an increased Na+ /K+ selectivity in the reverse order 9>2>8. Notably, the Na+ -induced FE of 8 (FEF=10.9), 2 (FEF=5.0) and 9 (FEF=2.0) showed a similar trend associated with a decreased K+ -induced FE [8 (FEF=2.7)>2 (FEF=1.5)>9 (FEF=1.1)]. Here, the Na+ -complex stability and Na+ /K+ selectivity is also influenced by the fluorophore moiety. Thus, fluorescent probe 8 (Kd =48 mm) allows high-contrast, sensitive, and selective Na+ measurements over extracellular K+ levels. A higher Na+ /K+ selectivity showed fluorescent probe 9, but also a higher Kd value of 223 mm. Therefore, 9 is a suitable tool to measure Na+ concentrations up to 300 mm at a fluorescence emission of 614 nm.

Sulphur-rich functionalized calix[4]arenes for selective complexation of Hg2+ over Cu2+, Zn2+ and Cd2.

The syntheses of two new ligands based on a calix[4]arene scaffold in the cone conformation functionalized on the phenolic positions 1 and 3 by diethylthiophosphonates (L1) or tetra(tri)thioethyleneglycol (L2) crowns are described. Together with ligand L3, the parent calix[4]arene substituted by a penta(tetra)thioethyleneglycol crown, the spectroscopic properties of the ligands were determined by means of UV-Vis absorption spectroscopy and steady-state and time-resolved fluorescence spectroscopy, showing that the ligands display modest but non-negligible intrinsic fluorescence properties (ϕfluo = 0.023; 0.026 and 0.029 for L1, L2 and L3 in CH2Cl2, respectively). The X-ray crystal structures of ligand L1, and of its synthetic precursor were determined and analyzed for their capacity to accommodate the incoming cationic species. The ligands were further investigated for their complexation properties of divalent cations such as Cu2+, Zn2+, Hg2+ and Cd2+ (under their nitrate salts) in 1 : 1 CH3CN/CH2Cl2 solutions (I = 0.01 M Et4NNO3, T = 25.0(2) °C), in which the additions of cations were monitored by absorption and steady-state fluorescence spectrophotometries. The stoichiometries of the corresponding complexes were assessed by ESI-MS, while insights into the structures of the complexes in solution were obtained with density functional theory (DFT) calculations. The influence of the sulphur and phenol coordinating moieties was addressed to show that the thiocrown compounds L2 and L3 displayed a marked affinity towards the soft mercuric cation (Δlog K ≥ 2), with no particular size selectivity effect, whereas ligand L1 can accommodate both the thio and phenol units to coordinate with Cu(ii). Altogether, these results point to the use of L3 as a selective fluoroionophore for detection of Hg2+.

A Highly K(+) -Selective Fluorescent Probe - Tuning the K(+) -Complex Stability and the K(+) /Na(+) Selectivity by Varying the Lariat-Alkoxy Unit of a Phenylaza[18]crown-6 Ionophore.

A desirable goal is to synthesize easily accessible and highly K(+) /Na(+) -selective fluoroionophores to monitor physiological K(+) levels in vitro and in vivo. Therefore, highly K(+) /Na(+) -selective ionophores have to be developed. Herein, we obtained in a sequence of only four synthetic steps a set of K(+) -responsive fluorescent probes 4, 5 and 6. In a systematic study, we investigated the influence of the alkoxy substitution in ortho position of the aniline moiety in π-conjugated aniline-1,2,3-triazole-coumarin-fluoroionophores 4, 5 and 6 [R=MeO (4), EtO (5) and iPrO (6)] towards the K(+) -complex stability and K(+) /Na(+) selectivity. The highest K(+) -complex stability showed fluoroionophore 4 with a dissociation constant Kd of 19 mm, but the Kd value increases to 31 mm in combined K(+) /Na(+) solutions, indicating a poor K(+) /Na(+) selectivity. By contrast, 6 showed even in the presence of competitive Na(+) ions equal Kd values (Kd (K+) =45 mm and Kd (K+/Na+) =45 mm) and equal K(+) -induced fluorescence enhancement factors (FEFs=2.3). Thus, the fluorescent probe 6 showed an outstanding K(+) /Na(+) selectivity and is a suitable fluorescent tool to measure physiological K(+) levels in the range of 10-80 mm in vitro. Further, the isopropoxy-substituted N-phenylaza[18]crown-6 ionophore in 6 is a highly K(+) -selective building block with a feasible synthetic route.

An ultra sensitive fluorescent nanosensor for detection of ionic copper

A stable and ultra sensitive nano-scale fluorescent chemo-sensor for trace amounts of Cu2+ was proposed. The Cu2+ selective fluoroionophore 2-{[(2-aminophenyl)imino]methyl}-4,6-di-tert-butylphenol (DMK-7) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanofibers and thin films. When embedded in polymers, the exploited DMK-7 dye exhibited enhanced photophysical characteristics in absorbance, Stoke’s shift, fluorescence quantum yield, and short and long-term photostability with respect to the solution phase. Sensing abilities of the nanofibers and thin films were tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-7-doped electrospun nanofibrous materials for copper sensing. The offered sensor displayed a sensitive response with a detection limit of 3.3×10−13M for Cu2+ ions over a wide concentration range of 5.0×10−12–5.0×10−5. Additionally, exhibited high selectivity over convenient cations; Na+, K+, Ca2+, Mg2+, NH4+ and Ag+, Al3+, Ba2+, Co2+, Cr3+, Fe3+, Fe2+, Hg2+, Li+, Mn2+, Ni2+, Pb2+, Sn2+ and Zn2+.

Detection of trace amounts of Hg2+ in different real samples based on immobilization of novel unsymmetrical tetradentate Schiff base within PVC membrane

A novel fluorescence optical sensor for sensitive and selective determination of Hg2+ ions in aqueous solution has been prepared. The sensing system is made of a novel unsymmetrical tetradentate Schiff base namely N-(2-hydroxyphenyl)-N′-(2-mercaptophenyl)-o-phthalylidene (HMP), as a neutral Hg2+-selective fluoroionophore immobilized in a plasticized PVC membrane containing potassium tetrakis-(4-chlorophenyl) borate (KTpClPB) as a lipophilic anionic additive. The response of the optode is based on the strong fluorescence enhancement of HMP upon exposure to Hg2+ ions. Under the optimum conditions, the proposed sensor displays a linear response in concentration range of 2.27×10−11 to 1.13×10−3mol/L, with a detection limit of 9.57×10−12mol/L. Furthermore, the proposed optode displays a good selectivity toward Hg2+ ions in comparison with common coexisting cations. The sensor was applied successfully for determination of mercury ions in different real samples.

A novel fluorescent nano-scale sensor for detection of trace amounts of Ca (II) ions

A photo-induced electron transfer (PET) based sensing approach for the direct determination of trace amounts of calcium ions is presented. The Ca2+ selective fluoroionophore Bis, 2,2'-{1,2 phenylenebis [nitrilomethylylidene]} diphenol (DMK) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanofibers, exploiting the prepared polymer. When embedded in nanomaterials, the DMK dye yielded strong absorbance, large Stoke's shift, high fluorescence quantum yield, and excellent short and long-term photostability. The sensing ability of the nanofibers was tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-doped electrospun nanofibrous materials for calcium sensing. The offered nanosensor displays a sensitive response with a detection limit of 0.016nM for Ca2+ ions over a wide concentration range, 1.0×10−10–1.0×10−4M, and exhibits high selectivity over Mg 2+ and other cations. Accuracy of the sensing system was proven by recovery tests.

Holmium(III)-selective fluorimetric optode based on N,N-bis(salicylidene)-naphthylene-1,8-diamine as a neutral fluorogenic ionophore

For the first time a highly sensitive and selective fluorimetric optode for determination of trace amounts of Ho3+ ions was prepared. The sensing system was prepared by incorporating of N,N-bis(salicylidene)-naphthylene-1,8-diamine (L) as a neutral Ho3+-selective fluoroionophore, in a plasticized PVC membrane containing sodium tetraphenyl borate as a lipophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Ho3+ ions. At pH 5.4, the proposed sensor displays a calibration curve over a wide concentration range of 1.0×10−10–1.0×10−3M, with a relatively fast response time of less than 1min. In addition to high stability, high reproducibility and a relatively long working lifetime, the sensor shows a good selectivity towards Ho3+ ion with respect to common coexisting cations. The fluorescence optode was applied to determination of holmium ion contents of water samples.

A new acridine derivative as a highly selective fluoroionophore for Cu2+ in 100% aqueous solution

A new acridine fluoroionophore containing two iminodiacetic acid ligands, Acridinyl Tetra Acid (ATA), was synthesized. The fluorescence sensing behavior of ATA toward metal ions was investigated in buffered aqueous media. The presence of Cu2+ resulted in significant quenching of the fluorescence emission from ATA, while other metal ions posed little interferences, if any. The fluorescence response was concentration-dependent and can be well described by the modified Stern–Volmer equation. A good linear relationship (R2=0.9952) was observed up to 3.0×10−6molL−1 Cu2+ ions. The detection limit, calculated following the 3σ IUPAC criteria, was 1.24×10−7molL−1. The presence of Cu2+ induces the formation of a 1:1 ligand/metal complex at neutral pH.

Li+-selective optodes – effect of fluoroionophore distribution in mesoporous silica thin films on Li+ response

This paper describes the development and the characterization of a Li+ optical sensor (optode) based on a Li+ selective fluoroionophore (KBL-01-Si), immobilized to a mesoporous silica thin film. KBL-01-Si was synthesized by the formation of a urethane bond between the hydroxyl terminated alkoxy chain of KBL-01 and 3-isocyanatopropyl-triethoxysilane. Li+ optodes with different amounts of KBL-01-Si fluoroionophore were fabricated by changing the grafting time of KBL-01-Si to mesoporous silica thin films with two different pore sizes. When the concentration of KBL-01-Si immobilized to the pore surface of the mesoporous silica thin films was low, response curves following a theoretical 1 : 1 complex formation equilibrium with binding constants for Li+ (log K) between 4.38 and 5.04 were observed. At higher concentrations of immobilized fluoroionophore, the response curves deviated from the fitting curve based on a theoretical chemical equilibrium, and the dynamic response was extended over a broad range from 10−6 to 1 M. In addition, it was observed by XPS depth profiling that KBL-01-Si was mainly localized on pore surface areas close to the channel entrances. These results indicate that not only the design of the fluoroionophore, but also the matrix for immobilization, and the microscale distribution of the fluoroionophore affect the characteristics of an ion sensor.

An efficient and selective flourescent chemical sensor based on 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane as a new fluoroionophore for determination of iron(III) ions. A novel probe for iron speciation

A novel fluorescent chemical sensor for the highly sensitive and selective determination of Fe3+ ions in aqueous solutions is prepared. The iron sensing system was prepared by incorporating 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a neutral Fe3+-selective fluoroionophore in the plasticized PVC membrane containing sodium tetraphenylborate as a liphophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Fe3+ ions. At pH 5.5, the proposed sensor displays a calibration curve over a wide concentration range from 6.0×10−4 to 1.0×10−7M, with a relatively fast response time of less than 2min. In addition to a high stability and reproducibility, the sensor shows a unique selectivity toward Fe3+ ion with respect to common coexisting cations. The proposed fluorescence optode was applied to the determination of iron(III) content of straw of rice, spinach and different water samples. The fluorescent sensor was also used as a novel probe for Fe3+/Fe2+ speciation in aqueous solution.

Fluorescence response of TICT-active aminostilbenes to copper(II) ions: redox reaction vs ion recognition

Cu(II)-selective fluorescence enhancement (1, 2, and 4) or fluorescence quenching (3) was observed for aminostilbenes 1–4 in acetonitrile. The fluorescence responses result from efficient Cu(II)-mediated oxidation of 1–4 that forms new fluorescent species rather than from any specific noncovalent interactions. Evidence of redox reactions includes irreversible Cu(II) titration spectra, spectroscopic observation of the radical cations, and isolation of oxidized aminostilbene dimers. These results provide a new method for synthesis of tetrasubstituted tetrahydrofurans and suggest that aminostilbenes with twisted intramolecular charge-transfer activity are potential fluorescence-enhanced Cu(II) chemodosimeters. The role of Cu(II)-mediated redox reactions should be always taken into account in mechanisms for sensing of arylamine-based Cu(II)-selective fluoroionophores.

Lanthanide recognition: A dysprosium(III) selective fluorimetric bulk optode

A fluorescence optical sensor for sensitive and selective determination of dysprosium(III) ions in aqueous solution has been prepared. The sensing system is made of 5-(dimethylamino)-N-(furan-2-yl-methylene)-naphthalene-1-sulfonohydrazide (L), as a neutral Dy3+-selective fluoroionophore, and a plasticized PVC membrane containing sodium tetraphenyl borate as a liphophilic anionic additive. The response of the optode is based on the strong fluorescence quenching of L by Dy3+ ions. At a pH of 5.0 the proposed sensor displays linear response in a rather wide concentration range of 1.0 × 10−10 to 1.0 × 10−2 M, with a fast response time of <35 s. Furthermore, the proposed optode displays a good selectivity toward Dy3+ ions in comparison with common coexisting cations. Also, it was applied successfully for determination of dysprosium ions in water samples.

Determination of terbium in phosphate rock by Tb 3+-selective fluorimetric optode based on dansyl derivative as a neutral fluorogenic ionophore

For the first time a highly sensitive and selective fluorimetric optode membrane was prepared for determination of trace amounts of Tb(III) ions in phosphate rock samples. The Tb(III) sensing system was constructed by incorporating 5-(dimethylamino)-N′-(2-hydroxy-1-naphthoyl) naphthalene-1-sulfonohydrazine (L) as a neutral Tb(III)-selective fluoroionophore, in the plasticized PVC membrane containing sodium tetraphenyl borate as a liphophilic anionic additive. The response of the optode is based on the strong fluorescence quenching of L by Tb 3+ ions. At a pH value of 5.0, the optode displays a wide concentration range of 1.0 × 10 −7 to 1.0 × 10 −2 M, with a relatively fast response time of less than 45 s. In addition, to high stability and reproducibility, the sensor shows a unique selectivity towards Tb 3+ ion with respect to common cations. The optode was applied successfully to the trace determination of terbium ion in binary mixture and water samples and the determination of Tb 3+ in phosphate rock samples.

Novel selective optode membrane for terbium ion based on fluorescence quenching of the 2-(5-(dimethylamino) naphthalen-1-ylsulfonyl)-N-henylhydrazinecarbothioamid

For the first time, a highly sensitive and selective fluorimetric optode membrane sensor for determination of trace amounts of Tb(III) ions was prepared. The Tb(III) sensing system was prepared by incorporating 2-(5-(dimethylamino) naphthalen-1-ylsulfonyl)-N-phenylhydrazinecarbothioamide (L) as a neutral Tb(III)-selective fluoroionophore, in the plasticized PVC membrane containing sodium tetraphenyl borate as a liphophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Tb(III) ions. At pH 4.7, the proposed sensor displays a calibration curve over a wide concentration range of 1.0 × 10 −2 to 1.0 × 10 −8 M, with a relatively fast response time of less than 1 min, high stability, high reproducibility and a relatively long working lifetime. The sensor shows a good selectivity towards Tb(III) ion respect to all lanthanide and common coexisting cations. The proposed fluorescence optode was applied successfully to determination of Tb(III) ion in water and phosphate rock samples.

Combination of a CT modulated PET and an intramolecular excimer formation to quantify PdCl2 by large fluorescence enhancement

The [6.6](9,10)anthracenophane 1 (Scheme 1) is a selective fluoroionophore for the detection of PdCl(2) with a large fluorescence enhancement factor (I/I(0) > 250).

Novel erbium (III)-selective fluorimetric bulk optode

For the first time a highly sensitive and selective fluorimetric optode membrane was prepared for the determination of trace amounts of Er(III) ions. The Er(III) sensing system was constructed by incorporating 5-(dimethylamino) naphthalene-1-sulfonyl-4-phenylsemicarbazide (L) as a neutral Er(III)-selective fluoroionophore, in the plasticized PVC-membrane containing sodium tetraphenyl borate as a lipophilic anionic additive. The response of the optode is based on the strong fluorescence quenching of L by Er 3+ ions. At a pH value of 5.0, the proposed optode displays a wide concentration range of 1.0 × 10 −10 to 1.0 × 10 −2 M, with a relatively fast response time of less than 50 s. In addition, to high stability and reproducibility, the sensor shows a unique selectivity towards Er 3+ ion with respect to common cations. The proposed optode was applied successfully to the trace determination of erbium ion in binary mixture and water samples.

A Selective Fluoroionophore Based on BODIPY‐functionalized Magnetic Silica Nanoparticles: Removal of Pb2+ from Human Blood

Get the lead out: The title fluorescence receptor exhibits a high affinity and selectivity for Pb(2+) over competing metal ions in water (see picture) with an overall emission change of approximately 8-fold at the emission maximum for Pb(2+). The fluorescence receptor can remove 96 % of 100 ppb Pb(2+) from human blood, and can be useful and effective for the selective and rapid removal of Pb(2+) in vivo.

A Selective Fluoroionophore Based on BODIPY‐functionalized Magnetic Silica Nanoparticles: Removal of Pb2+ from Human Blood

AbstractWeg mit Blei: Der Fluoreszenzrezeptor im Titel zeichnet sich durch eine hohe Affinität und Selektivität für Pb2+ gegenüber konkurrierenden Metallionen in Wasser aus (siehe Bild), wobei der Faktor der gesamten Emissionsänderung am Emissionsmaximum für Pb2+ etwa 8 beträgt. Der Fluoreszenzrezeptor kann 96 % von 100 ppb Pb2+ aus menschlichem Blut entfernen und eignet sich für die effektive, selektive und schnelle Entfernung von Pb2+ in vivo.magnified image

A highly Li+-selective glass optode based on fluorescence ratiometry

This paper presents the preparation and characterization of a single-excitation, dual-emission ratiometric optical Li(+)-sensing device using a newly designed and synthesized highly Li(+)-selective fluoroionophore (KBL-01) carrying 14-crown-4 ether with tetramethyl and benzene blocking subunits as Li(+)-binding site and boron-dipyrromethene as fluorophore. The indicator dye was covalently immobilized on the surface of a porous glass support having a large internal surface area using a silane-coupling agent. The resulting Li(+)-selective glass optode shows dual fluorescence emission response in pseudo-serum at varying Li(+) concentrations, allowing ratiometric signal processing. The obtained signal is independent of the presence of possibly interfering cations (Na(+), K(+), Mg(2+) and Ca(2+)) and pH. The sensor response was found to be reversible within the Li(+) concentration range from 10(-4) to 10(-1) M, and showed good repeatability and light stability. The plots of the ratiometric signal versus the Li(+) concentrations in spiked real human serum go along with the response curve in pseudo-serum. These results indicate that the novel Li(+)-selective glass optode can be employed as a Li(+)-sensing device with high durability, sensitivity and accuracy for medical analyses.