Rhod-5N as a Fluorescent Molecular Sensor of Cadmium(II) Ion

The photophysical and complexing properties of Rhod-5N (commercially available) in MOPS buffer are reported. This fluorescent molecular sensor consists of a BAPTA chelating moiety bound to a rhodamine fluorophore. Its fluorescence quantum yield is low and a drastic enhancement of fluorescence intensity upon cation binding was observed. Special attention was paid to the complexation with Cd²⁺, a well known toxic metal ion. Possible interference with other metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, Pb²⁺) was examined. Rhod-5N was found to be highly selective of Cd²⁺ over those interfering cations except Pb²⁺. The limit of detection is 3.1 μg l⁻¹.     

Fluorescence Sensors for Selective Detection of Hg2+ Ion Using a Water-Soluble Poly(vinyl alcohol) Bearing Rhodamine B Moieties

The novel water-soluble poly(vinyl alcohol) with pendant rhodamine B moiety as colorimetric and fluorescene chemosensor for Hg²⁺ ions was prepared by grafting poly(vinyl alcohol) using rhodamine B hydrazide and hexamethylenediisocyanate as fluorescent dye and coupling agent, respectively. Because of their good water-solubility, the polymers binding rhodamine B can be used as chemosensors in aqueous media. With the addition of Hg²⁺ ions into the aqueous solution, visual color changes and fluorescence enhancements were detected. In addition, we also noticed that other metal ions such as Ag⁺, Cd²⁺, Co²⁺, Cu²⁺, K⁺, Mg²⁺, Ba²⁺, Fe²⁺, Ni²⁺, Pb²⁺, Cr³⁺, Fe³⁺ and Zn²⁺ cannot induce obvious changes to the fluorescence spectra of the polymer chemosensors. The combination of water solubility and positive fluorescence response as well as color change are hence particularly promising for the practical utility of the sensors.     

Interaction Between Methylene Blue and CalfThymus Deoxyribonucleic Acid by Spectroscopic Technologies

Characterization of the interaction between methylene blue (MB) and calf thymus deoxyribonucleic acid (ctDNA) was investigated by UV absorption spectra, fluorescence spectra, fluorescence polarization and fluorescence quenching experiments by ferrocyanide. The above results indicated that the binding modes of MB to ctDNA were relative to the molar ratio γ (γ=[DNA]/[MB]). At low γ ratios (γ < 4), remarkable hypochromic effect with no shift of λ_max in the absorption spectra of MB was observed in the presence of increasing amounts of ctDNA, the fluorescence of MB was efficiently quenched by the ctDNA bases and the fluorescence polarization of MB was slightly increased, which indicated that MB cations bound to phosphate groups of ctDNA by electrostatic interaction and then stacked on the surface of ctDNA helix. While at high γ ratios (γ > 6), besides the fluorescence of MB was quenched efficiently by the ctDNA bases, a red shift (about 3 nm) in the absorption spectra of MB was observed and the fluorescence polarization of MB was obviously increased, which indicated the intercalation binding that MB molecules were intercalated into the space of two neighbouring DNA base pairs was the preferred mode. Effects of K₄Fe(CN)₆ on the fluorescence quenching of the MB-ctDNA system at low and high γ ratios were also performed. The results showed that at γ = 1.7, the quenching effect by ferrocyanide was higher than that of pure MB, while at γ = 13.6 a decreased quenching of the fluorescence intensity was observed as compared with that of pure MB, which further proved the above conclusion. In addition, the mechanisms of the hypochromic effect and the fluorescence quenching were also discussed in detail.     

Fluorescent and Chromogenic Receptor Bearing Amine and Hydroxyl Functionality for Iron (III) Detection in Aqueous Solution

The noncyclic 2,2′-[ethane-1,2-diylbis (iminomethanediyl)]diphenol (4) fluorescent receptor bearing two amine and hydroxyl groups have been designed and investigated for their binding properties towards various cations. The fluorescent spectral measurements revealed that receptor 4 is a selective fluorescent sensor for Fe³⁺ ions but not for metal ions such as Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ and Bi³⁺. The binding ability was confirmed with spectroscopic methods and density functional theory calculation (DFT). This straightforward and cost effective receptor provides rapid detection of Fe³⁺ ions at concentrations as low as 2.5 μM and expected to be useful to design efficient chemically and biological sensor.     

Complex formation of pyridine‐azacrown ether amide macrocycles with proton and heavy metal ions in aqueous solution

This research concerns the analysis of the proton and metal ion binding of amide macrocycles of different structures and sizes by potentiometric, ¹H NMR and X‐ray diffraction methods. Protonated ligands exist as a 3D network structures. The ligands form 1:1 complexes with heavy metal ions (Cu²⁺, Cd²⁺, Pb²⁺, Zn²⁺, and Ni²⁺) in aqueous solutions and demonstrate the high selectivity towards Cu²⁺ cations. The pyridine‐2,6‐dicarbamide fragment provides structural rigidity to crown ether, resulting the molecule has an open cavity and faster kinetics of metal complexes formation. Copyright © 2015 John Wiley & Sons, Ltd.     

Removal of heavy metals from aqueous solutions using Fe3O4, ZnO, and CuO nanoparticles

This study investigated the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ from aqueous solutions with novel nanoparticle sorbents (Fe₃O₄, ZnO, and CuO) using a range of experimental approaches, including, pH, competing ions, sorbent masses, contact time, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The images showed that Fe₃O₄, ZnO, and CuO particles had mean diameters of about 50?nm (spheroid), 25?nm (rod shape), and 75?nm (spheroid), respectively. Tests were performed under batch conditions to determine the adsorption rate and uptake at equilibrium from single and multiple component solutions. The maximum uptake values (sum of four metals) in multiple component solutions were 360.6, 114.5, and 73.0?mg?g^?1, for ZnO, CuO, and Fe₃O₄, respectively. Based on the average metal removal by the three nanoparticles, the following order was determined for single component solutions: Cd²⁺?>?Pb²⁺?>?Cu²⁺?>?Ni²⁺, while the following order was determined in multiple component solutions: Pb²⁺?>?Cu²⁺?>?Cd²⁺?>?Ni²⁺. Sorption equilibrium isotherms could be described using the Freundlich model in some cases, whereas other isotherms did not follow this model. Furthermore, a pseudo-second order kinetic model was found to correctly describe the experimental data for all nanoparticles. Scanning electron microscopy, energy dispersive X-ray before and after metal sorption, and soil solution saturation indices showed that the main mechanism of sorption for Cd²⁺ and Pb²⁺ was adsorption, whereas both Cu²⁺ and Ni²⁺ sorption were due to adsorption and precipitation. These nanoparticles have potential for use as efficient sorbents for the removal of heavy metals from aqueous solutions and ZnO nanoparticles were identified as the most promising sorbent due to their high metal uptake.     

Conductometric study of complex formations between some substituted pyrimidines and some metal ions in acetonitrile and the determination of thermodynamic parameters

The complexation reactions between Cr³⁺, Cd²⁺, Co²⁺, Ni²⁺, Hg²⁺, Zn²⁺, Pb²⁺,and Ag⁺ metal ions with diethyl-3-(4-hydroxy-6-methylpyrimidin-2-yl) guanidine (L1), 2-amino,4-hydroxy,6-methylpyrimidine (L2), and 2-(diethylamin),4-hydroxy,6-methylpyrimidine (L3) in acetonitrile (AN) were studied using a conductometric method. The formation constants of the resulting complexes were determined from computer fitting conductance-mole ratio data. The results revealed that the formation constants of L1 with metal ions are varying in order of Cr³⁺ > Pb²⁺ > Zn²⁺ > Co²⁺ > Hg²⁺ > Ag⁺ ~ Cd²⁺ > Ni²⁺. For L2 and L3 the sequence of complex formation constants are follow as Cr³⁺ > Pb²⁺ > Zn²⁺ > Co²⁺ > Cd²⁺ > Hg²⁺ > Ag⁺ > Ni²⁺ and Cr³⁺ > Pb²⁺ > Zn²⁺ > Co²⁺ > Ni²⁺ ~ Hg²⁺ ~ Cd²⁺ ~ Ag⁺, respectively. The values of the thermodynamic parameters (ΔH, ΔS and ΔG) for complexation reactions were obtained from the temperature dependence of the stability constants. In all cases, the complexes were found to be enthalpy stabilized but entropy destabilized. In addition, some ab-initio quantum-mechanical calculations were carried out, in order to obtain a clue about the degree tendency of ligands to metal ions.     

8-Hydroxyquinoline Functionalized Graphene Oxide: an Efficient Fluorescent Nanosensor for Zn<Superscript>2+</Superscript> in Aqueous Media

A nanosensor, based on 8-hydroxyquinoline functionalized graphene oxide, was developed for the fluorescence detection of Zn²⁺. It showed high selectivity and sensitivity for Zn²⁺ion in aqueous solution over other metal ions such as Li⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Fe²⁺, Fe³⁺and Cr³⁺. Due to the linearity of the emission intensity toward Zn²⁺ concentration, fluorescent technique could be used for the detection of Zn²⁺ ion even at very low concentrations.     

Design,synthesis and sensor activity of a highly photostable blue emitting 1,8-naphthalimide

This work reports on the design, synthesis and photophysical properties of a highly photostable blue emitting 1,8-naphthalimide, containing hindered amine radical scavenger moiety and a tertiary amine cation receptor. The novel compound was configured as “fluorophore-spacer-receptor” system based on photoinduced electron transfer. Photophysical characteristics of the examined compound were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compound to detect cations was evaluated by the changes in its fluorescence intensity in the presence of metal ions (Cu²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe³⁺ and Zn²⁺) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer resulting in enhancement of the 1,8-naphthalimide fluorescence intensity. Among the tested metal ions only Cu²⁺ was efficiently detected. Also, it is clearly shown that the 2,2,6,6-tetramethylpiperidine fragment, incorporated in the structure of the novel 1,8-naphthalimide, considerably improves the sensor's photostability, sensitivity and selectivity.     

A Novel Highly Sensitive and Selective Fluorescent Sensor for Imaging Copper (II) in Living Cells

In this work, we designed and synthesized a novel quinolin-based derivative which exhibited signaling behaviors for Cu²⁺. Upon the addition of Cu²⁺ to the solution of the molecule, it displayed an obvious fluorescence quenching in a linear fashion due to the formation of a 1:1 metal–ligand complex. This fluorescent sensor exhibited a rare sensitivity toward Cu(II) (the level of magnitude could be 6?×?10^?8), a rapid response (<10 s) and also high selectivity toward Cu²⁺ over other metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Fe³⁺, Mn²⁺, Hg²⁺, Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, Zn²⁺ and Al³⁺. Simultaneously, the cell imaging experiments and filter paper test demonstrated its extensive applicability.     

Design and Synthesis of a Pyridine Based Chemosensor: Highly Selective Fluorescent Probe For Pb2+

A pyridine based imine-linked chemosensor has been synthesized and evaluated its binding affinity with library of transition metal ions. It has prominent selectivity towards Pb²⁺ among other metal ions in DMF/H₂O (9:1, v/v) solvent system. The 1:1 stoichiometric was confirmed by job’s plot and has a binding constant (K_a)?=?5.142?×?10³ M^?1 on fluorescence. A B3LYP/6-31G and B3LYP/LanL2DZ basis sets were employed for optimization of 3 and 3.Pb²⁺.     

Urea Based Dipodal Fluorescence Receptor for Sensing of Fe3+ Ion in Semi-Aqueous Medium

Urea based fluorescent chemosensor 1 was synthesized. Receptor 1 shows unique selectivity for the Fe³⁺ion and no such significant response was noticed with other metal ions (Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ and Bi³⁺) in DMSO/H₂O (50:50,v/v) semi-aqueous solution. The binding features have been established by absorption and fluorescence spectroscopic methods. The binding constant (K) values obtained from Benesi-Hildebrand, Scatchard and Connor plot for receptor 1 is (8.3?±?0.3) × 10³ M^?1 and has good detection limit 0.7?μM. The stoichiometry of 1.Fe³⁺ complex was confirmed by mass spectroscopy and Job’s plot.

Synthesis of Tapioca Cellulose-based Poly(amidoxime) Ligand for Removal of Heavy Metal Ions

Poly(acrylonitrile)/cellulose block copolymer (PAN-b-cell) was prepared by using a free radical initiating process and then the nitrile functional groups of the PAN blocks of the copolymers were transformed into amidoxime ligands. The resulting poly(amidoxime) ligands could complex with heavy metal ions; for example, the reflectance spectra of the [Cu -ligand]ⁿ⁺ was found to be at the highest absorbance, about 94%, at pH 6. The pH was the key parameter for metal ions sensing by the ligand. The adsorption capacity for copper was very good, 272 mg g^?1, with a fast adsorption rate (t_1/2 = 10 min). The adsorption capacities for other heavy metal ions such as Fe³⁺, Cr³⁺, Co³⁺ and Ni²⁺ were also good, being 242, 219, 201 and 195 mg g^?1, respectively, at pH 6. The heavy metal ions removal efficiency from water was 98% at low concentration. The data proved that the heavy metal ions adsorption onto the polymer ligands were well fitted with the Langmuir isotherm model (R²>0.99), which suggests that the cellulose-based adsorbent surface namely the poly(amidoxime) ligand, was homogenous and a monolayer. The reusability was examined by a sorption/desorption process for six cycles and the extraction efficiency was determined. This new adsorbent could be reused for 6 cycles without any significant loss in its original removal function.     

New dithiacrown–ether butadienyl dyes: synthesis,structure, and complex formation with heavy metal cations

Benzothiazole type butadienyl dyes containing a dithia‐15‐crown‐5 ( 2a ) or dithia‐18‐crown‐6 ether ( 2b ) moieties were synthesized. The structures of dyes 2a , b and their complexes with Ag⁺ and Pb²⁺ were studied by an X‐ray crystallography. It was found that the conformations of dithiacrown–ether moieties of dyes 2a , b are unfavorable for complex formation and change significantly upon binding of Ag⁺ or Pb²⁺. The complexation of 2a , b with Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺ in water–acetonitrile mixtures with different contents of water (P_W = 0–75%, v/v) was studied by ¹H NMR, UV–Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd²⁺ < Pb²⁺ ≤ Ag⁺ << Hg²⁺ in the case of 2a and in the sequence Cd²⁺ < Ag⁺ < Pb²⁺ << Hg²⁺ in the case of 2b . As P_W increases, the thermodynamic stability of Ag⁺ complexes increases. The opposite effect is observed for the complexes with Cd²⁺, Pb²⁺, and Hg²⁺. When P_W ～ 50%, the stability constants of complexes with Cd²⁺ and Pb²⁺ become too small to be measured. The selectivity of ligands 2a , b toward Hg²⁺ versus Ag⁺ is very high at any P_W values (selectivity coefficients > 10⁴). The complexation of 2a , b with Hg²⁺ at P_W ≤ 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown‐containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of two new fluorescent macrocycles: A novel fluorescent chemosensor for zinc ion

Two new macrocyclic systems (L¹, L²) containing two emissive naphthalene were synthesized and characterized. The macrocycles were studied by ¹H NMR, ¹³C NMR, COSY, HMQC, DEPT, microanalysis and mass spectroscopy. The influence of metal cations Na⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺ on the spectroscopic properties of the macrocyclic systems in acetonitrile/DMF 9:1 (v/v) mixtures were investigated by means of absorption and emission spectrophotometry. The macrocycle L¹ was found to be as an effective fluorescence sensor for Zn²⁺ ions. Zn²⁺ and Cd²⁺ ions show the most effects on the fluorescence intensity of L².     

Analytical Evaluation of Cu<Superscript>2+</Superscript> Selective Behavior of calix[4]arene Derivative

The present article describes the solvatochromic effect including solvent system selection, time study and a detailed complexation study along with exploration of extraction properties of 5,11,17,23-tetrakis[(diethylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4) that bears nitrogen atom as a donor group available for chelating metal ions. Complexation properties of 4 toward selected transition metal ions have been investigated by UV-visible and fluorescence spectroscopies. The% efficiency of 4 toward selected transition metal ions was found in order Cu²⁺> Ni²⁺> Hg²⁺> Zn²⁺> Co²⁺> Cd²⁺> Pb²⁺. It has been noticed that 4 is not only proved to be an efficient Cu²⁺ selective chromoionophore but also possesses an effective extraction property for transferring Cu²⁺ ions from an aqueous to dichloromethane layer. The FT-IR spectroscopic method has also been applied for further confirmation of the complexation phenomenon of 4 with Cu²⁺ ion and found adequate.     

A Highly Selective and Sensitive Fluorescent Chemosensor for Aluminum Ions Based on Schiff Base

An efficient “off–on” type fluorescent chemosensor, (E)-N′-(4-(diethylamino)-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H ₂ L), based on Schiff base for the determination of Al³⁺ has been designed, synthesized, and evaluated. Upon treated with Al³⁺, the fluorescence of H ₂ L was enhanced 45-fold due to the chelation-enhanced fluorescence (CHEF) effect based on the formation of a 1:1 complex between the chemosensor and Al³⁺. Other metal ions, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Ga³⁺, Zn²⁺, Cr³⁺, Cd²⁺, Ag⁺, Fe³⁺, In³⁺, Mn²⁺, Pb²⁺, Co²⁺, and Ni²⁺ had little effect on the fluorescence. The results demonstrate that the chemosensor H ₂ L has stronger affinity with Al³⁺ than other metal ions. The detection limit of H ₂ L for sensing Al³⁺ is 3.60 × 10^?6 M in EtOH–H₂O (3:7, v/v) solution. And the recognizing behavior has been investigated both experimentally and computationally.     

A Selective Fluorescent Sensor for Hg2+

A novel rhodamine based fluorescent chemosensor RQP was prepared and characterized by ¹HNMR, ¹³CNMR and HR-MS. The properties of RQP were studied through UV–Vis spectroscopy and fluorescence spectroscopy. RQP showed highly selectivity toward Hg²⁺ over other metal ions, including Ag⁺, Cd²⁺, Cu²⁺, Na⁺, Mg²⁺, Ni²⁺, Pb²⁺, Fe³⁺, and Zn²⁺ in aqueous solutions. The recognition process is reversible and confirmed by EDTA experiment.     

A Rhodamine Derivative Based Chemosensor with High Selectivity and Quick Respond to Cr<Superscript>3+</Superscript> in Aqueous Solution

In this paper, a new kind of colorimetric chemsensor aiming at detecting Cr³⁺ has been synthesized, and it is based on the “Off-On” effect of a rhodamine derivative. Comparing with other metal irons (Na⁺, K⁺, Ni²⁺, Hg²⁺, Fe³⁺, Mn²⁺, Co²⁺, Cd²⁺, Cu²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Ba²⁺, Ag⁺, Fe²⁺, Ce³⁺), the chemsensor has a quick and accurate response to Cr³⁺ in H₂O-EtOH solution (4/1, v/v). There is an obvious change in color, from colorless to bright pink when Cr³⁺ is detected. According to the fitting curve based on Benesi-Hildebrand equation and working curve of absorption strength in UV-vis spectrum, the binding pattern of Cr³⁺ and the rhodamine derivative follows a 1:1 stoichiometry. The chemsensor shows great potential in monitoring Cr³⁺ in the aqueous medium with high efficiency, which is supposed to complete the recognition in the minimum as 5.2?×?10^?7 mol/L within 5 min.