Fluorescence sensing of Cu within a pseudo 18-crown-6 cavity

We report herein a pseudo-crown based fluorescent receptor (1) for the selective detection of Cu²⁺ cation. Receptor 1 can detect Cu²⁺ even in 5 μM level in acetonitrile-water (9:1 v/v). Compound 1 is very effective for the detection of Cu²⁺ amongst the series of metal ions studied (Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Pb²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Mn²⁺).     

Phenothiazine-pyridyl chalcone: an easily accessible colorimetric and fluorimetric ‘on-off’ dual sensing probe for Cu

Phenothiazine-pyridyl chalcone, a new internal charge transfer (ICT) probe, has been designed that allows naked eye detection and a reversible, ratiometric ‘on-off’ sensing capability for biologically and environmentally significant Cu²⁺ in CH₃OH-H₂O (4:1 v/v) under buffered conditions. The association constants determined using spectrophotometric and the fluorimetric techniques follow the order Cu²⁺ > Ni²⁺ > Co²⁺ > Zn²⁺ > Cd²⁺ > Mg²⁺ ≈ Ba²⁺ ≈ Ca²⁺ ≈ K⁺≈ Na⁺ ≈ Li⁺.     

ICT-based Cu(II)-sensing 9,10-anthraquinonecalix[4]crown

A series of calix[4]arene-based chromogenic sensors bearing the 9,10-anthraquinone moiety have been synthesized and examined for their abilities to recognize various cations such as Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Cd²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Co²⁺, and Cu²⁺ by UV-vis spectroscopy. In acetonitrile, the presence of Cu²⁺ induces the formation of the 1:1 ligand/metal complex, which exhibits a new absorption band centered at 450 nm, and leads to an obvious color change from yellow to red.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

A diamide-diamine based Cu chromogenic sensor for highly selective visual and spectrophotometric detection

A diamide-diamine based sensor 3 possessing anthracene-9,10-dione as a chromogenic moiety has been synthesized and demonstrates a highly selective colour change from red to blue with Cu²⁺ for visual detection of Cu²⁺ (5-50 μM). Other metal ions, viz. Fe²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Ag⁺, Pb²⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations do not lead to any change in colour and their presence does not interfere with the visual and quantitative analysis of Cu²⁺. The selective deprotonation of an aryl amine NH by Cu²⁺ is responsible for a bathochromic shift and significant colour changes. Significantly, the stability of the 3·Cu²⁺ complex between pH 7 and 12 allows Cu²⁺ estimation under neutral and basic conditions.     

Polarographic and voltammetric investigations in N-methylpyrrolidinone(2) and N-methylthiopyrrolidinone(2)

Polarographic and voltammetric methods were employed to study the influence of N-methylpyrrolidinone(2) (NMP) and N-methylthiopyrrolidinone(2) (NMTP) towards a series of cations. In NMP reversible electrode reactions were observed for Na⁺, K⁺, Tl⁺, Zn²⁺, Cd²⁺, Cu²⁺, Ag⁺ and irreversible reductions for Ba²⁺, Mn²⁺, Co²⁺ and Ni²⁺. 0.1 mol l^?1 tetraethylammoniumperchlorate solutions served as supporting electrolytes. Li⁺ was not electroactive in the supporting electrolyte mentioned, but yielded an irreversible cathodic wave in tetra-n-butylammonium perchlorate. In NMTP, Li⁺, Na⁺, Tl⁺, Zn²⁺, Cd²⁺, Cu⁺ and Ag⁺ gave reversible cathodic waves on the DME, while Mn²⁺, Co²⁺ and Ni²⁺ were reduced in an irreversible electrode process. Bisbiphenylchromium iodide serving as a reference system throughout this study showed reversible behaviour in both solvents. A comparison of E_1/2 for given ions in both solvents showed a shift of about 0.5 V to more positive values in the case of a typically hard cation such as Na⁺ whereas soft cations such as Ag⁺ and Cu⁺ shifted by more than 0.8 V to more negative values. The effects of these two solvents on the cations studied is discussed in terms of donor acceptor interactions between the cation and the solvent molecules with special respect to the changes caused by replacing the oxygen atom in NMP by a sulphur atom.     

Zn selective luminescent ‘off-on’ probes derived from diaryl oxadiazole and aza-15-crown-5

New photo-induced electron transfer (PET) probes OMOX and OBOX, carrying an additional binding site in the form of ‘oxadiazole nitrogen’ have been designed to evaluate binding interactions with biologically significant Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, and Zn²⁺ including environmentally toxic Ba²⁺ and Cd²⁺ using optical spectral techniques. While Li⁺, Na⁺, and K⁺ did not appreciably perturb either the absorption or emission spectra, Ba²⁺, Ca²⁺, Mg²⁺, Zn²⁺, and Cd²⁺ induced slight red shifts (2-8 nm) in the UV-visible spectra as well as pronounced chelation induced enhanced fluorescence (CHEF). Both OMOX and OBOX exhibited the highest CHEF in contact with the zinc ion, whereas Ba²⁺, Ca²⁺, Mg²⁺, and Cd²⁺ induced relatively less emission enhancements. OBOX, which is a poorer emitter (Φ_f=0.0062) than OMOX (Φ_f=0.015), showed highly promising 160-fold emission enhancement in the presence of Zn²⁺. Potential, therefore is available in OBOX to function as a selective luminescent ‘off-on’ sensor for Zn²⁺ in the presence of coordinatively competing Ba²⁺, Ca²⁺, Mg²⁺, and Cd²⁺ ions.     

Fluorescent chemosensor based-on naphthol-quinoline for selective detection of aluminum ions

In this study, an assay to quantify the presence of aluminum ions with a receptor containing naphthol and quinoline moieties was developed using a turn-on fluorescence enhancement approach. Upon treatment with aluminum ions, the fluorescence of the receptor was enhanced at 510 nm due to the formation of a complex between the ligand and aluminum ions at room temperature. As the concentration of Al³⁺ was increased, the fluorescence gradually increased. Other metal ions, such as K⁺, Ag⁺, Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺, Cr³⁺, Fe³⁺, In³⁺, had no significant effect on the fluorescence.     

A simple internal charge transfer probe offering dual optical detection of Co (II) via color and fluorescence modulations

A newly designed internal charge transfer chemosensor, DIPZON exhibits Co²⁺ selective optical responses, which include 112 nm red shift in absorption and a dramatic 37-fold enhancement in the fluorescence output in the buffer CH₃OH/H₂O (1:1 v/v) system. By contrast, the optical responses were not as sensitive with several other biologically relevant metal ions examined with the binding interactions following the sequence Co²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺ >> Ba²⁺ ≈ Ca²⁺ ≈ Mg²⁺ ≈ K⁺ ≈ Na⁺ ≈ Li⁺.     

Fluorescence quenching studies on the interaction of a novel deepened cavitand towards some transition metal ions

A novel ‘three-level’ deepened cavitand featuring a significantly sizable portal has been synthesized and its interaction with some transition metal ions has been investigated in THF/H₂O binary solvent using fluorescence quenching technique. The results suggest that among the used transition metal ions including Ag⁺, Cd²⁺, Cu²⁺, Fe³⁺, Cr³⁺, Hg²⁺, La³⁺, Mn²⁺, Ni²⁺, Zn²⁺ and Co²⁺, only Fe³⁺ and Cu²⁺ show good quenching ability. In order to interpret the quenching mechanism, the Stern–Volmer kinetics, and the presence of both the dynamic and static quenching have been discussed. It was found that the simultaneous presence of the sphere-of-action static quenching and dynamic quenching model agrees very well with the experimental results. The limits of detection for Fe³⁺ and Cu²⁺ were found to be 2.1 × 10⁻⁶ mol L⁻¹ (3σ) and 3.6 × 10⁻⁶ mol L⁻¹ (3σ), respectively. Cations with potential interference, such as K⁺, Na⁺, Mg²⁺, Ca²⁺, Co²⁺, La³⁺ and Mn²⁺ do not have significant effects on the determinations of Fe³⁺ and Cu²⁺. This cavitand can be potentially applied as optical sensor for the detection of Fe³⁺ and Cu²⁺.     

Anthracene-tethered aminomethyl oxadiazole chemosensor: a probe offering selective chromo- and fluorogenic signalings for targeting Cu(II)

A new optical chemosensor featuring anthracene as a fluorophore and an aminomethyl oxadiazole moiety as a bidentate chelate has been synthesized. From photophysical studies, we find the probe to offer remarkably selective chromo- and fluorogenic signaling responses towards biologically and environmentally significant Cu²⁺. In the presence of Cu²⁺, fluorescence is quenched to the extent of 95%, while the absorbance due to the anthracene chromophore is nearly completely bleached out. On the other hand, Li⁺, Na⁺, K⁺, Ba²⁺, Ca²⁺, Zn²⁺, Mg²⁺, Cd²⁺, Co²⁺, Ni²⁺, Ag⁺, Pb²⁺ and Hg²⁺ even at 10 times higher concentration than Cu²⁺ do not cause detectable photophysical perturbations. The stability constants, logK for Cu²⁺ were calculated to be 4.36 and 4.76 on the basis of spectrophotometric and fluorimetric titrations, respectively. However, logKs for other metal ions are too low (<0.1) to pose any interferences in the optical detection of Cu²⁺. Though, not fully defined, the uncommon phenomenon of the absorbance bleaching by Cu²⁺ is tentatively explained by invoking the involvement of non-covalent anthracene-Cu²⁺ complex.     

A New Fluorescent Chemosensor for Cu2+ Based on 1,2,3,4,5,6,7,8,9,10‐Decahydroacridine‐1,8‐dione Fluorophore

A new chemosensor for Cu²⁺ was synthesized based on 1,2,3,4,5,6,7,8,9,10‐decahydroacridine‐1,8‐dione dyes, which exhibited an obvious fluorescent selectivity to the sensing of Cu²⁺ ions over other cations, such as Na⁺, K⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Zn²⁺, Ag⁺ and Pb²⁺. Moreover, it presented a fluorescent switch function when EDTA was added to the compound‐Cu²⁺ complex in examined systems.     

Solvent donor and acceptor properties of pyridine

Polarographic and cyclovoltammetric measurements on the perchlorates of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Tl⁺, Ba²⁺ and Ni²⁺ as well as on the trifluoromethane sulfonates of Zn²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Cu⁺, Mn²⁺ and Co²⁺ were carried out. The data allowed the evaluation of the different donor behavior of pyridine towards hard, border line and soft cations. The conclusions drawn from electrochemical investigations were supported by Gibbs energies of transfer for cations, which were derived from both electrochemical measurements based on the bis(biphenyl)chromium assumption and from solubility studies based on the tetraphenylarsonium tetraphenylborate assumption. The acceptor properties of pyridine were obtained from the solvatochromic dyes bis(cyano)bis(1,10-phenanthroline)iron(II) and bis(cyano)bis(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II) and the results were compared with the acceptor number and the E _T -value.     

Laser induced breakdown spectroscopy (LIBS) as an analytical tool for the detection of metal ions in aqueous solutions

Laser induced breakdown spectroscopy (LIBS) is applied to analyze aqueous solutions of Li⁺, Na⁺, Ca²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Er³⁺ and suspensions of ErBa₂Cu₃O_x particles (d=0.2 m). An excimer (308 nm) pumped dye laser with laser pulse at 500 nm and pulse energy at 22±2 mJ is used to produce plasma in aqueous solution. Plasma emission lines of the elements are detected by a photodiode array detector. Detection limits of the metal ions are 500 mg/l for Cd²⁺, 12.5 mg/l for Pb²⁺, 6.8 mg/l for Ba²⁺, 0.13 mg/l for Ca²⁺, 13 g/l for Li⁺ and 7.5 g/l for Na⁺. No mercury and erbium emission can be detected, even at Hg²⁺ and Er³⁺ concentrations of up to the g/l range. On the other side, for Er in suspensions of ErBa₂Cu₃O_x particles a more than 10³ times higher sensitivity is found than for dissolved Er³⁺. This result gives a possibility to analyze colloid-borne metal ions with an increased sensitivity.     

An acyclic,dansyl based colorimetric and fluorescent chemosensor for Hg(II) via twisted intramolecular charge transfer (TICT)

An efficient fluorescent chemosensor for Hg²⁺ ion, based on 5-(dimethylamino)-N-(2-mercaptophenyl)naphthalene-1-sulfonamide, has been developed. It exhibits Hg²⁺-selective on–off fluorescence quenching behavior via twisted intramolecular charge transfer (TICT) mechanism, which is rationalized by time dependent density functional theory (TD-DFT) calculations. The system exhibits visible color change from colorless to gray upon Hg²⁺ binding with very high selectivity and sensitivity (as low as 5.0 × 10⁻¹⁰ mol L⁻¹) over other metal ions such as K⁺, Na⁺, Ag⁺, Mn²⁺, Ca²⁺, Ba²⁺, Fe²⁺, Zn²⁺, Pb²⁺, Cu²⁺, Sn²⁺, Cd²⁺, Ni²⁺ and Co²⁺. The present sensing system is also successfully applied for the detection of Hg²⁺ ion in real samples.     

A chelating resin with bis[2-(2-benzothiazolylthioethyl)sulfoxide]: Synthesis, characterization and properties for the removal of trace heavy metal ion in water samples

A new chelating resin containing bis[2-(2-benzothiazolylthioethyl)sulfoxide] was synthesized using chloromethylated polystyrene as material and characterized by elemental analysis and infrared spectra. The adsorption capacities of the newly formed resin for Hg²⁺, Ag⁺, Cu²⁺, Zn²⁺, Pb²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Fe³⁺ were investigated over the pH range 1.0-6.0. The resin exhibited no affinity for alkali or alkaline earth metal ions. The maximum adsorption capacities of the resin for Hg²⁺, Ag⁺, Cu²⁺, Zn²⁺, Pb²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Fe³⁺ were 1.49, 0.96, 0.58, 0.11, 0.37, 0, 0.24, 0.36 and 0.25 mmol g⁻¹, respectively. In column operation it had been observed that Hg²⁺ and Ag⁺ in trace quantity could be separated from different binary mixtures and Hg²⁺ could be effectively removed from industrial wastewater and the natural water spiked with Hg²⁺ at usual pH.     

Synthesis of a novel poly(para‐phenylene ethynylene) for highly selective and sensitive sensing mercury (II) ions

A new poly(p‐phenylene ethynylene) derivative with pendant 2,2′‐bipyridyl groups and glycol units (PPE‐bipy) has been prepared, and its metal ion sensing properties were investigated. The polymer of PPE‐bipy exhibited high selectivity for Hg²⁺ as compared with Li⁺, Na⁺, K⁺, Ba²⁺, Ca²⁺, Mg²⁺, Al³⁺, Mn²⁺, Ag⁺, Zn²⁺, Pb²⁺, Ni²⁺, Cd²⁺, Cu²⁺, Co,²⁺ and Fe³⁺ in THF/EtOH (1:1, v/v) solution. The fluorescence of PPE‐bipy was efficiently quenched by Hg²⁺ ions, and the detection limit was found to be 8.0 nM in a THF/EtOH (1:1, v/v) solvent system. PPE‐bipy also showed a selective chromogenic behavior toward Hg²⁺ ions by changing the color of the solution from slight yellow to colorless, which can be detected with the naked eye. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1998–2007, 2008     

A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu<Superscript>2+</Superscript> cation

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu²⁺ over a wide range of other cations. The solution of 1 (10 μmol/L) upon addition of Cu²⁺ displayed distinguishing pink color compared with other cations including K⁺, Ni²⁺, Ca²⁺, Mn²⁺, Na⁺, Sr²⁺, Zn²⁺, Co²⁺, Cd²⁺, Mg²⁺, Cr³⁺, Ag⁺, and Ba²⁺, indicating the sensitivity and selectivity of 1 to Cu²⁺. Thus, the advantage of this assay is that naked-eye detection of Cu²⁺ becomes possible. Moreover, among these metal ions investigated, only Cu²⁺ quenched more than half fluorescent intensity of 1. The ESI-TOF spectrum of a mixture of 1 and CuCl₂ in combination of the fluorescence titration spectra of 1 (10 μmol/L) upon addition of various amounts of Cu²⁺ revealed the formation of a 2:1 metal-ligand complex through the metal coordination interaction. Supported by the National Natural Science Foundation of China (Grant Nos. 20872101 & 20772086)     

DDB liver drug as a novel ionophore for potentiometric barium (II) membrane sensor

Dimethyl-4,4-dimethoxy-5,6,5′,6′-dimethylene dioxy biphenyl-2,2-dicarboxylate (DDB) liver drug is used as a novel ionophore in plasticized poly (vinyl chloride) (PVC) matrix membrane sensors for barium ions. Optimum performance characteristics are displayed by membrane sensor incorporating DDB ionophore, potassium tetrakis(4-chlorophenyl)borate as lipophilic salt, and o-nitrophenyloctyl ether as plasticizer. The sensor exhibits a linear response over the concentration range 10⁻¹-10⁻⁵ mol l⁻¹ BaCl₂ with a Nernstian slope of 30 mV per decade and high selectivity towards Ba²⁺ with respect to Li⁺, Na⁺, K⁺, Rb⁺, NH₄⁺, Mg²⁺, Ca²⁺, Sr²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cd²⁺, Al³⁺, La³⁺, and Ce³⁺ ions. The sensor response is stable over a wide pH range (4-9) and the lifetime is about 2 months. The proposed sensor is successfully applied to the determination of Ba²⁺contents of some rocks.