Highly selective and sensitive fluorescent chemosensor for Hg in aqueous solution

A new indole-based fluorescent chemosensor 1 was prepared and its metal ion sensing properties were investigated. It exhibits high sensitivity and selectivity toward Hg²⁺ among a series of metal ions in H₂O-EtOH (7:1, v/v). The association constant of the 1:1 complex formation for 1-Hg²⁺ was calculated to be 9.57 × 10³ M⁻¹, and the detection limit for Hg²⁺ was found to be 2.25 × 10⁻⁵ M. Computational results revealed that 1 and Hg²⁺ ion formed with a central tetrahedron-coordinated Hg²⁺.     

A new acridine derivative as a fluorescent chemosensor for zinc ions in an 100% aqueous solution: a comparison of binding property with anthracene derivative

A new acridine derivative was synthesized as a fluorescent chemosensor for Zn²⁺ in an 100% aqueous solution. Compound 1 displayed a selective CHEF (chelation enhanced fluorescence) effect with Zn²⁺, on the other hand, a similar anthracene derivative 2 did not display any significant change with the metal ions examined.     

Aminoxy-linked rhodamine hydroxamate as fluorescent chemosensor for Fe in aqueous media

A novel feric ion-selective rhodamine-based fluorescent chemosensor, which contains a bis-aminoxy chain moiety, has been developed. The multi-dentate binding site of rhodamine fluorophore shows selective detection of ferric iron over other biologically important metal ions in aqueous media and also shows 1:1 binding stoichiometry.     

A fluorescent and colorimetric chemosensor for selective detection of aluminum in aqueous solution

We have synthesized a new Schiff base 1, which detects Al³⁺ through fluorescence and naked eye in aqueous solution. The sensor 1 exhibited selective and sensitive recognition toward Al³⁺ via significant fluorescence enhancement (31-fold). Moreover, it showed a significant color change from colorless to yellow. The complex formation was proposed to be 1:1 ratio, based on the Job plot, ESI-mass spectrometry analysis, ¹H NMR titration, and IR analysis. The detection limit was 1.00 μM, which is below the WHO acceptable limit (1.85 μM) in drinking water. In addition, the sensor 1 could be recyclable simply through treatment with a proper reagent such as EDTA.     

Benzimidazole-based tripodal receptor: highly selective fluorescent chemosensor for iodide in aqueous solution

We synthesized a novel tripodal fluorescent receptor bearing benzimidazole motifs as recognition sites in the pods of the receptor. The recognition behavior of the receptor toward various anions was evaluated in CH3CN/H2O (9:1, v/v) solution. The receptor showed changes in fluorescent intensity only with I-, but it showed no significant changes on addition of other anions such as F-, Cl-, Br-, HSO4-, NO3-, CH3COO-, and H2PO4-.     

Colorimetric and fluorescent chemosensor for citrate based on a rhodamine and Pb complex in aqueous solution

In this paper we unveil a novel rhodamine compound based fluorescent chemosensor (1-Pb²⁺) for colormetric and fluorescent detection of citrate in aqueous solution. This is the first fluorescent chemosensor for citrate based on rhodamine compound. The comparison of this method with some other fluorescence methods for citrate indicates that the method can detect citrate in aqueous solution by both color changes and fluorescent changes with long emission wavelength. In the new developed sensing system, 1-Pb²⁺ is fluorescent due to Pb²⁺-induced fluorescence enhancement of 1. However, the addition of citrate may release 1 into the solution with quenching of fluorescence. The chemosensor can be applied to the quantification of citrate with a linear range covering from 1.0 × 10⁻⁷ to 5.0 × 10⁻⁵ M and a detection limit of 2.5 × 10⁻⁸ M. The experiment results show that the response behavior of 1-Pb²⁺ towards citrate is pH independent in medium condition (pH 6.0–8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for citrate in the presence of other anions (even those that exist in high concentration), which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward citrate is fast (response time less than 1 min). In addition, the chemosensor has been used for determination of citrate in urine samples with satisfactory results.     

Synthesis of triazolyl anthracene as a selective fluorescent chemosensor for the Cu(II) ion

The Cu(I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) has been used to synthesize an anthracene-based fluorescent compound that undergoes strong fluorescence quenching in the presence of Cu(II). Fluorescence studies indicate that the compound forms a 1:1 complex and can be used to quantitatively determine micromolar concentrations of Cu(II) in aqueous solution.     

A new perylene diimide-based fluorescent chemosensor for selective detection of ATP in aqueous solution

A new perylene diimide (PDI) ligand (1) functionalized with a Zn²⁺–dipicolylethylenediamine (Zn²⁺–DPEN) moiety was synthesized and first used as a fluorometric chemosensor to specifically detect the presence of ATP over other phosphate anions in aqueous solution. The solution of 1 upon addition of ATP displayed a remarkable absorption decrease compared with other anions, indicating the selectivity of 1 to ATP. Moreover, among these anions investigated, only ATP showed a considerable enhancement of fluorescent intensity of 1. The fluorescence molar ratio plot combined with the ESI-TOF mass measurement determined that binding stoichiometry between 1 and ATP is 1:1.     

A new fluorescent as well as chromogenic chemosensor for anions based on an anthracene carbamate derivative

A new fluorescent as well as chromogenic anion sensor, 1,8-anthradiol bis(N-phenylcarbamate) 2, was synthesized. It exhibits new selective red-shifted absorption and fluorescence bands with F⁻ and AcO⁻, which could be attributed to the anthracene moiety directly involved in the bonding interaction with the anions.     

A fluorescent chemosensor for Hg based on naphthalimide derivative by fluorescence enhancement in aqueous solution

Naphthalimide derivative (compound 1) containing hydrophilic hexanoic acid group was synthesized and used to recognize Hg²⁺ in aqueous solution. The fluorescence enhancement of 1 is attributed to the formation of a complex between 1 and Hg²⁺ by 1:1 complex ratio (K = 2.08 × 10⁵), which has been utilized as the basis of fabrication of the Hg²⁺-sensitive fluorescent chemosensor. The comparison of this method with some other fluorescence methods for the determination of Hg²⁺ indicated that the method can be applied in aqueous solution rather than organic solution. The analytical performance characteristics of the proposed Hg²⁺-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Hg²⁺ with a linear range covering from 2.57 × 10⁻⁷ to 9.27 × 10⁻⁵ M and a detection limit of 4.93 × 10⁻⁸ M. The experiment results show that the response behavior of 1 toward Hg²⁺ is pH independent in medium condition (pH 4.0–8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Hg²⁺ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward Hg²⁺ is fast (response time less than 1 min). In addition, the chemosensor has been used for determination of Hg²⁺ in hair samples with satisfactory results, which further demonstrates its value of practical applications.     

Rosamine-based fluorescent chemosensor for selective detection of silver(I) in an aqueous solution

The synthesis and photophysical properties of a rosamine-based fluorescent chemosensor, RosAg, for detecting Ag ion in an aqueous solution are described. This fluorescent sensor has a negligible quantum yield (<0.005) in the absence of Ag(+), whereas a significant increase in fluorescence is observed upon complexation with Ag(+) under physiological conditions. The crystal structure of the silver complex with the chelator moiety of RosAg reveals a trigonal-planar coordination geometry in which three S atoms occupy the metal center. Although a strong coordinative interaction of Ag-N is not observed in the crystal structure, the (1)H NMR experiments suggest that aniline nitrogen is likely to be associated with the Ag(+) center in the solution state. This may inhibit the photoinduced electron transfer process and result in the enhancement of fluorescence.     

Thermo and pH sensitive fluorescent polymer sensor for metal cations in aqueous solution

A new monomeric fluorophore N‐acryl‐N'‐(quinolin‐8‐yl)thiourea (AQT) was synthesized. Free radical copolymerization was carried out in order to prepare a water‐soluble fluorescent copolymer, based on N‐isopropylacrylamide. The fluorescent characteristic of the aqueous solutions of copolymers was investigated both in varied pH and in the presence of metal cations. The polymer‐ contained AQT was found to be a selective chemosensor for Ni, Pb, Co ions especially for Co ion. The obtained copolymers show thermo‐sensitive lower critical solution temperature (LCST) ranging from 32.5 to 37.5°C with varied ratios of AQT, N, N‐dimethylacrylamide and N‐isopropylamide. Copyright © 2007 John Wiley & Sons, Ltd.     

A novel fluorescent chemosensor for Cu(II) in aqueous solution based on a β-aminobisphosphonate receptor

A novel β-aminobisphosphonate receptor has been combined with naphthalene in the fluorophore-spacer-receptor format of a typical photoinduced electron transfer (PET) based sensor. The sensor was synthesised in two steps by first reacting aminomethylnaphthalene with diethyl vinylphosphonate to produce the parent tetraester, followed by deprotection with bromotrimethylsilane to afford the desired sensor. The fluorescence emission of the sensor was observed to remain ‘On’ over a wide pH range (2-10). Cu(II) was found to bind strongly to the sensor resulting in an ‘On-Off’ fluorescent response with sensitivity in the μM range.     

Dipodal fluorescent chemosensor for Cu and resultant complex as a chemosensor for iodide

A dipodal receptor was synthesized by condensation of isophthalaldehyde and p-toluenesulfonylhydrazide. The receptor was found to be selective for Cu²⁺ recognition in CH₃CN. The resultant Cu²⁺ receptor complex selectively recognized iodide through cation displacement assay in a CH₃CN/H₂O (8:2, v/v) solvent system.     

A highly selective and sensitive fluorescent chemosensor for Hg2+ in neutral buffer aqueous solution

A selective and sensitive fluorescent chemosensor for Hg2+, which was composed of two aminonaphthalimide fluorophores and a receptor of 2,6-bis(aminomethyl)pyridine, was synthesized through the reaction of 2,6-bis(chloromethyl)pyridine and N-[2-(2-hydroxyethoxy)ethyl]-4-piperazino-1,8-naphthalimide. The chemosensor showed an about 17-fold increase in fluorescence quantum yield upon addition of 1 equiv of Hg2+ in neutral buffer aqueous solution, and the other common metal ions did not notably disturb the detection of Hg2+.     

A new rhodamine-based fluorescent chemosensor for mercury in aqueous media

A new fluorescent ‘‘on–off' chemosensor for Hg2+initiated by a derivative of rhodamine B was designed and synthesized. Compound 1 exhibited high sensitivity and selectivity for Hg2+over other commonly coexistent metal ions in aqueous media. Upon the addition of Hg2+, the spirocyclic ring of probe is opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm is observed. The colorimetric and fluorescent response to Hg2+can be conveniently detected by the naked eye, which provides a facile method for visual detection of Hg2+. From the molecular structure and spectral results of 1, an irreversible, hydrolysis, desulfurization reaction mechanism is proposed.     

Naphthalene-derived Al3+-selective fluorescent chemosensor based on PET and ESIPT in aqueous solution

A simple fluorescent chemosensor HL based on naphthalene with high selectivity and sensitivity towards Al³⁺ over other commonly coexisting metal cations in fully aqueous solution to enhance the potential applications of the fluorescent chemosensor was developed. HL exhibited a significant fluorescence enhancement at 475?nm in the presence of Al³⁺ over other competitive metal ions with a low detection limit of 0.43?μM due to the inhibition of the photo induced electron transfer (PET) and the excited-state intramolecular proton transfer (ESIPT). The 1:1 binding stoichiometry between HL and Al³⁺ was corroborated by the Job plot and the ESI-MS spectrum. Importantly, the reversible recognition process of HL to Al³⁺ will make HL could be used circularly and repeatedly in practical applications by addition of Na₂EDTA. In addition, the binding behavior and sensing mechanism of HL to Al³⁺ were illustrated in detail by the ¹H NMR titration experiment.     

A lanthanide hybrid cluster as a selective optical chemosensor for phosphate-containing anions in aqueous solution.

An europium-chelating [2Fe-2S] cluster was used to assemble an optical molecular chemosensor highly selective for phosphate-containing anions. Phosphate, pyrophosphate, AMP, ADP, ATP, DNA and RNA were well distinguished by UV/V is absorption or fluorescence studies.     

Preparation of a metal–ligand fluorescent chemosensor and enantioselective recognition of carboxylate anions in aqueous solution

Two chiral fluorescent chemosensors 1 and 2 were synthesized, and the structure characterized by IR, ¹H NMR, ¹³C NMR, MS spectra and elemental analysis. Their recognition ability was studied in aqueous solution (Tris–HCl buffer pH 7.4, MeOH/H₂O = 1:1) through fluorescence spectra. Receptors 1 and 2 showed a good binding ability to the copper ion. The host 1-Cu²⁺ complex showed a chiral recognition ability to mandelate anions with a preferable binding to l-mandelate than d-mandelate anions. The host 1-Cu²⁺ complex and l- or d-mandelate anions formed 1:1 stoichiometric complex. The binding constant for l-mandelate is 576 M⁻¹, whereas that for d-mandelate is only 38 M⁻¹, which can be distinguished by the different change of fluorescence intensity.     

Rhodamine-based highly sensitive colorimetric off-on fluorescent chemosensor for Hg2+ in aqueous solution and for live cell imaging

A novel rhodamine-based highly sensitive and selective colorimetric off-on fluorescent chemosensor for Hg(2+) ions is designed and prepared by using the well-known thiospirolactam rhodamine chromophore and furfural hydrazone as signal-reporting groups. The photophysical characterization and Hg(2+)-binding properties of sensor RS1 in neutral N, N-dimethylformamide (DMF) aqueous solution are also investigated. The signal change of the chemosensor is based on a specific metal ion induced reversible ring-opening mechanism of the rhodamine spirolactam. The response of the chemosensor for Hg(2+) ions is instantaneous and reversible. And it successfully exhibits a remarkably "turn on" response toward Hg(2+) over other metal ions (even those that exist in high concentration). Moreover, this sensor is applied for in vivo imaging in Rat Schwann cells to confirm that RS1 can be used as a fluorescent probe for monitoring Hg(2+) in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems.