Synthesis and transport abilities of new membrane materials incorporating mono- and bi-pyrazolic compounds

The membrane materials were obtained by photopolymerisation of formulation that contain the active monomer spread on a polyacrylonitrile support. The facilitated transport and the extraction power of Cd(II), Pb(II) and Hg(II) through the synthesised membranes were reported. We have determined both the diffusion flux of different cations and the selectivity of the prepared membranes towards each cations.     

Complexing Polymer Films in The Preparation of Modified Electrodes for Detection of Metal Ions

Summary: The complexing properties of poly (3-(pyrrol-1-yl)propylmalonic acid) (poly1) and poly(N,N′-ethylenebis[N-[(3-(pyrrole-1-yl)propyl) carbamoyl) methyl]-glycine (poly2) coated electrodes (C|poly1 and C|poly2) towards Cu(II), Pb(II), Hg(II) and Cd(II) cations using the open circuit chemical preconcentration-anodic stripping technique were studied. Sorption process of metal cations onto complexing surfaces was readily investigated through the combination of a chemical pre-concentration-anodic stripping technique with a Langmuir isotherm model. The modified electrodes were used for the voltammetric determination of Cu(II), Pb(II), Hg(II) and Cd(II) ions, giving low detection limits for Cu(II) (5 × 10⁻⁹ mol L⁻¹) and Pb(II) (5 × 10⁻¹⁰ mol L⁻¹). The ability of the modified electrodes to analyze Cu(II) ions in natural sample has been demonstrated by the analysis of a tap water sample. The results of the preconcentration process under competitive conditions clearly shows that the selectivity of complexing molecular electrode materials can be subtly tuned upon playing on the accumulation time, polymer thickness and/or memory effect of the binding polymers, opening up new avenues towards evolutive and efficient smart sensing materials.     

Novel fluorogenic calix[4]arene-bis(crown-6-ether) for selective recognition of thallium(I)

A new fluorogenic, dansyl group-containing derivative of 1,3-alternate calix[4]arene-bis(crown-6-ether) provides optical recognition of Tl+ with selectivity over many other metal cations, including Na+, K+, Ca2+, Ag+, Hg2+ and Pb2+, and embodies the first example of a calixarene-based fluorescent Tl+-chemosensor.     

Synthesis and characterization of nano-composite ion-exchanger; its adsorption behavior

A novel organic-inorganic nanocomposite cation-exchanger has been synthesized via sol-gel method. It was characterized on the basis of FTIR, XRD, SEM, TEM, AFM and Raman studies. The structural studies reveal semi-crystalline nature of the material with the particle size ranging from 1-5 nm. Physiochemical properties such as ion-exchange capacity, chemical and thermal stability of composite material have also been determined. Bifunctional behavior of the material has been indicated by its pH titrations curves. The nanocomposite material exhibits improved thermal stability, higher ion-exchange capacity and better selectivity for toxic heavy metals. The ion-exchange material shows an ion-exchange capacity of 1.8 meq g(-1) for Na(+) ions. Sorption behavior of metal ions on the material was studied in different solvents. The cation exchanger was found to be selective for Pb(II), Hg(II) and Zr(IV) ions. The limit of detection (LOD) and the limit of quantification (LOQ) for Pb(II) ion was found to be 0.85 and 2.85 μg L(-1). Analytically important separations of heavy metal ions in synthetic mixtures as well as industrial effluents and natural water were achieved with the exchanger. The practical utility of polyanilineZr(IV)sulphosalicylate cation exchanger has been established for the analysis and recovery of heavy metal ions in environmental samples.     

Lipophilic ionic additive for controlling the selectivity of ion-selective electrodes reversible to cations of nitrogen-containing organic bases

The effect of a lipophilic ionic additive, a tetradecylammonium salt of a liquid ion exchanger, on the selectivity of ion-selective electrodes (ISEs) for cations of nitrogen-containing organic bases was studied. Additive-containing ISEs exhibited a higher selectivity for cations of primary to tertiary amines as compared to that for quaternary ammonium cations. A maximum change in selectivity (up to more than two orders of magnitude) due to the introduction of tetradecylammonium was observed for membranes containing dinonyladipate as a plasticizer and tris(nonyloxy)benzene sulfonic acid as an ion exchanger. In this case, the introduction of lipophilic ionic additive may lead to the reversal of the selectivity series. The effect of the lipophilic ionic additive on the selectivity of ISEs with membranes plasticized with o-nitrophenyl octyl ether decreased approximately by an order of magnitude. The selectivity of ISEs with the membranes containing tetrakis(4-chlorophenyl) borate as a cation exchanger was virtually independent of the presence of lipophilic ionic additives. The results obtained were explained by the peculiarities of ion-pair formation in the membrane.     

Effect of membrane composition on the selectivity of electrodes selective for alkylammonium ions with different degrees of substitution

The effect of the nature of an ion exchanger and a plasticizer on the selectivity of ion-selective electrodes for cations of primary-tertiary amines and quaternary ammonium bases was studied. The increments of methylene and ionic groups in the logarithms of selectivity coefficients were calculated. It was demonstrated that the effect of the membrane composition on the selectivity coefficient was governed by changes in the increments of corresponding groups. The maximum change in selectivity, which may attain three orders of magnitude, was observed for pairs of primary-quaternary alkylammonium cations. It was shown that the effect of the nature of the cation exchanger on selectivity coefficients was comparable with that of the plasticizer nature.     

Voltammetric Sensing of Mercury and Copper Cations at Poly(EDTA‐like) Film Modified Electrode

Complexing polymer‐coated electrodes have been synthesized by oxidative electropolymerization of ethylenediamine tetra‐N‐(3‐pyrrole‐1‐yl)propylacetamide (monomer L ). The presence of four polymerizable pyrrole fragments on the same EDTA skeleton was thought to confer enhanced rigidity and controlled dimensionality to the resulting complexing materials, which were used for the electrochemical detection of Hg(II), Cu(II), Pb(II) and Cd(II) ions by means of the chemical preconcentration‐anodic stripping technique. The polyamide electrode material showed particularly a significant selectivity towards mercury ions, even in the presence of a large excess of other metal cations. Moreover, the use of imprinted polymer‐coated electrodes prepared by electropolymerization of L in the presence of metal cations turned out to significantly improve the detection limits, down to 5×10^?10 mol L^?1 for Hg(II) and Cu(II) species.     

Ion-selective electrodes for determination of organic ammonium ions: Ways for selectivity control

The influence of the ISE membrane composition on the selectivity for primary, secondary, tertiary, and quaternary alkylammonium cations, as well as for cations of physiologically active amines, has been investigated. Factors studied include the effect of plasticizer (2-nitrophenyl octyl ether, o-NPOE; dibutyl phthalate, DBP; dinonyl adipate, DNA; tris(2-ethylhexyl) phosphate, TEHP) and ion exchanger (potassium tetrakis(4-chlorophenyl)borate, K(TpClPB); potassium tris(nonyloxy)benzenesulfonate, K(TNOBS)), as well as that of the lipophilic cationic additive (tetradecylammonium nitrate, (TDA)NO(3)) and neutral carrier (dibenzo-18-crown-6) presence in membrane. It has been established that plasticizer nature affects K(i,j)(pot) values both when the target and/or foreign ions have non-ionic polar groups capable of specific interaction with plasticizer, and when the only difference consists in the substitution degree of their ionic groups. K(i,j)(pot) values for quaternary alkylammonium cations over primary-tertiary ones change in the following order: TEHP>DBP approximately DNA>o-NPOE. The highest K(i,j)(pot) value change is achieved for the primary-quaternary alkylammonium cation pair, amounting to 3 and 4.7 orders for membranes containing K(TNOBS) and K(TpClPB) as ion exchangers, respectively. In its turn, the ion exchanger influence on the selectivity depends on plasticizer nature, it being maximal for o-NPOE (about 2 orders) and practically non-existent for TEHP. On the whole, as compared to K(TpClPB)-based ISEs, those based on K(TNOBS) show higher selectivity for primary-tertiary alkylammonium cations over quaternary ones. Incorporation of (TDA)NO(3) into membrane causes further improvement of selectivity for primary-tertiary alkylammonium cations in the case of K(TNOBS) only. The maximal total effect of the ion exchanger and lipophilic ionic additive is observed for ISEs with DNA-plasticized membranes and is over 3 orders. The influence of crown ether on the selectivity also depends significantly upon ion exchanger and plasticizer nature. For ISEs with o-NPOE-plasticized membranes the K(i,j)(pot) value changes can be as great as 3 (ion exchanger K(TNOBS)) and even 4.5 (ion exchanger K(TpClPB)) orders. On the contrary, for ISEs with TEHP-plasticized membranes the crown ether effect on the selectivity is unessential. The results obtained are explained by peculiarities of organic ammonium cations solvating by plasticizer and association of cations with ion exchangers.     

The influence of the plasticizer nature on the selectivity of ion-selective electrodes to physiologically active amine cations: Regularities and abnormalities

The influence of the nature of plasticizer in the membrane of an ion-selective electrode (ISE) on its selectivity to cations of more than 20 physiologically active amines (PAA) is studied. It is found that an increase in the basicity of the plasticizer leads to a sharp increase in the membrane selectivity to PAA cations with lower degrees of the substitution of the salt-forming nitrogen atom, and also to PAA cations with nonionic polar groups capable of forming hydrogen bonds with Lewis bases. PAA cations forming intermolecular hydrogen bonds are an exception. The effect of the nature of the ion exchanger on the selectivity to PAA cations is strongest when plasticizers with low basicity are used; the selectivity of membranes with plasticizers of high basicity does not depend on the nature of the ion exchanger. For ISEs based on the neutral carrier dibenzo-18-crown-6 (DB-18-C-6), the best selectivity to primary amine cations in comparison to secondary and tertiary ones is achieved using plasticizers with low basicity.     

Ferrocene-based heteroditopic receptors displaying high selectivity toward lead and mercury metal cations through different channels

The synthesis and electrochemical, optical, and ion-sensing properties of ferrocene-imidazophenazine dyads are presented. Dyad 4 behaves as a highly selective chemosensor molecule for Pb(2+) cations in CH(3)-CN/H(2)O (9:1). The emission spectrum (λ(exc) = 317 nm) undergoes an important chelation-enhanced fluorescence effect (CHEF = 47) in the presence of Pb(2+) cations, a new low-energy band appeared at 502 nm, in its UV/vis spectrun, and the oxidation redox peak is anodically shifted (ΔE(1/2) = 230 mV). The presence of Hg(2+) cations also induced a perturbation of the redox potencial although in less extension than those found with Pb(2+) cations. Dyad 7, bearing two fused pyridine rings, has shown its ability for sensing Hg(2+) cations selectively through three channels: electrochemical, optical, and fluorescent; the oxidation redox peak is anodically shifted (ΔE(1/2) = 200 mV), a new low-energy band of the absorption spectrum appeared at 485 nm, and the emission spectrum (λ(exc) = 340 nm) is red-shifted by 32 nm accompanied by a remarkable chelation-enhanced fluorescent effect (CHEF = 165). Linear sweep voltammetry revealed that Cu(2+) cations induced oxidation of the ferrocene unit in both dyads. (1)H NMR studies have been carried out to obtain information about the molecular sites which are involved in the binding process.     

Rhodamine-based Hg2+-selective chemodosimeter in aqueous solution: fluorescent OFF-ON

[reaction: see text] N-(Rhodamine-6G)lactam-N'-phenylthiourea-ethylenediamine (1) was developed as a fluorescent and colorimetric chemodosimeter in aqueous solution with a broad pH span (5 approximately 10) and high selectivity toward Hg2+ but no significant response toward other competitive cations, such as Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Ca2+, Mg2+, K+, Na+, etc. The Hg2+-promoted ring opening of spirolactam of the rhodamine moiety induced cyclic guanylation of the thiourea moiety, which resulted in the dual chromo- and fluorogenic observation (OFF-ON).     

Gold nanoparticles generated through "green route" bind Hg2+ with a concomitant blue shift in plasmon absorption peak

We discuss here a quick, simple, economic and ecofriendly method through a completely green route for the selective detection of Hg(2+) in aqueous samples. Here we exploited the ability of chitosan to generate gold nanoparticles and subsequently to act as a stabilizer for the formed nanoparticles. When chitosan stabilized gold nanoparticles (CH-Au NPs) are interacted with Hg(2+) a blue shift for its localized surface plasmon resonance absorbance (LSPR) band is observed. The blue shift is reasoned to be due to the formation of a thin layer of mercury over gold. A concentration as low as 0.01 ppm to a maximum of 100 ppm Hg(2+) can be detected based on this blue shift of the CH-Au NPs. While all other reported methods demand complex reaction steps and costly chemicals, the method we reported here is a simple, rapid and selective approach for the detection of Hg(2+). Our results also show that the CH-Au NPs have excellent selectivity to Hg(2+) over common cations namely, Pb(2+), Cd(2+), Mn(2+), Fe(2+), Ag(1+), Ce(4+), Ni(2+), and Cu(2+).     

Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier.

A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.     

Lead and mercury sensing by calixarene-based fluoroionophores bearing two or four dansyl fluorophores

A detailed study on the photophysical and complexing properties of calixarenes bearing two and four dansyl derivatives (Calix-DANS2 and Calix-DANS4) in a CH3CN/H2O mixture (60:40 v/v) is reported. Calix-DANS2 shows a high selectivity towards Hg2+ over interfering cations (Na+, K+, Ca2+, Cu2+, Zn2+, Cd2+ and Pb2+) and a sensitivity in the 10(-7) mol L(-1) concentration range. The complexation of mercury ion induces a strong fluorescence quenching due to a well-defined electron transfer process from the fluorophore to the metal center. Calix-DANS4 exhibits an extremely high affinity for Pb2+ with a high selectivity over various competing ions. The unprecedented detection limit (4 microg L(-1)) is fully compatible with the level defined by the World Health Organisation. The affinity of Calix-DANS4 for Pb2+ can be rationalized by the activation of the inert pair of electrons on Pb2+. The number of fluorophores involved in the complexation can be determined from a careful time-resolved fluorescence characterization.     

Multicolor fluorescence of a styrylquinoline dye tuned by metal cations

A styrylquinoline dye with a dipicolylamine (DPA) moiety (1) has been synthesized. The dye 1 in acetonitrile demonstrates multicolor fluorescence upon addition of different metal cations. Compound 1 shows a green fluorescence without cations. Coordination of 1 with Cd(2+) shows a blue emission, while with Hg(2+) and Pb(2+) exhibits yellow and orange emissions, respectively. The different fluorescence spectra are due to the change in intramolecular charge transfer (ICT) properties of 1 upon coordination with different cations. The DPA and quinoline moieties of 1 behave as the electron donor and acceptor units, respectively, and both units act as the coordination site for metal cations. Cd(2+) coordinates with the DPA unit. This reduces the donor ability of the unit and decreases the energy level of HOMO. This results in an increase in HOMO-LUMO gap and blue shifts the emission. Hg(2+) or Pb(2+) coordinate with both DPA and quinoline units. The coordination with the quinoline unit decreases the energy level of LUMO. This results in a decrease in HOMO-LUMO gap and red shifts the emission. Addition of two different metal cations successfully creates intermediate colors; in particular, the addition of Cd(2+) and Pb(2+) at once creates a bright white fluorescence.     

Synthesis,characterization and adsorption behaviour of TX-100 based Sn(IV) phosphate,a new hybrid ion exchanger

A new hybrid ion exchanger, Triton X-100 based tin(IV) phosphate (TX-100SnP) has been synthesized and characterized by ion exchange and physico-chemical methods such as ion exchange capacity, elution and concentration behaviour, IR, X-ray, TG/DTA and elemental analysis. Its adsorption behaviour has also been studied for some alkaline earths and heavy metal ions in different acidic media. It has been found generally more selective for metal ions as compared to tin(IV) phosphate prepared earlier. For Pb(II), Hg(II) and Fe(III) its selectivity has been found to be exceptionally good. On this basis, some binary separations have been performed involving these metal ions. Thermal studies show a high thermal stability of the material. It retains 54.54% of its i.e.c. at 200°C and 27.27% at 300°C.     

Chelating resins: Sorption characteristics in chloride media

The chelating resins Dowex A1 and its purified form, Chelex 100, contain the iminodiacetate functional group. The resins can exchange cations from solutions of high pH and anions from low pH solutions. Further, the iminodiacetate functional group provides chelating capability leading to special selectivity for multivalent ions such as Sb(V) and Hg(II). A systematic study of the sorption characteristics of Chelex 100 was initiated in our laboratory. Distribution coefficient values (K_d) were measured for Zn(II), Cd(II), Sn(IV), Sb(V) and Hg(II) as a function of HCl concentration and for Cu(II) and Pb(II) as a function of pH. The results obtained thus far indicate that Sb(V) and Hg(II) have high K_d values in acid chloride solutions. A radiochemical separation procedure was developed for the determination of Hg by neutron activation analysis using sorption onto Chelex 100.     

Aldimines generated from aza-Wittig reaction between bis(iminophosphoranes) derived from 1,1'-diazidoferrocene and aromatic or heteroaromatic aldehydes: electrochemical and optical behaviour towards metal cations

Aldimine 4 bearing a 2-quinolyl group was prepared by aza-Wittig reaction between the triphenyliminophosphorane derived from the 1,1'-diazidoferrocene and 2-formylquinoline. However, aldimine 5, bearing a pyrene ring, was prepared using the most reactive tributyliminophosphorane derivative and the corresponding 1-formylpyrene. On the other hand, formation of aldimine 8 involves a tandem process, Staudinger reaction/intramolecular aza-Wittig reaction, by using directly 1,1'-diazidoferrocene and 2-(diphenylphosphonyl)benzaldehyde. Aldimine 4 behaves as chemosensor molecule for Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+) cations through two different channels: electrochemical (ΔE(1/2) = 222-361 mV) and chromogenic (Δλ = 122-153 nm), which can be used for the "naked eye" detection of these metal cations. Aldimine 5 behaves as a highly selective redox (in CH(3)CN) and fluorescent (in CH(3)Cl-DMF) probe for Hg(2+) metal cations even in the presence of a large excess of the other metal cations tested. Aldimine 8 displays electrochemical affinity (ΔE(1/2) = 60-288 mV) to Li(+), Ca(2+), Mg(2+), Zn(2+) and Pb(2+) metal cations, with the phosphorus oxide functionality as a binding site. From the (1)H NMR titration data as well as DFT calculations, different tentative binding modes have been established, for these structurally related ferrocenyl derivatives.     

新型氮杂大环化合物的研究Ⅲ.取代不对称多齿氮杂大环化合物的合成、表征与配位性能

合成了四种以Nsp2 和Nsp3为配位原子的取代不对称多齿氮杂大环化合物 ,制备了它们与不同金属离子的配合物 ,通过元素分析和光谱表征 ,研究了配体的结构与其配位性能的关系 .以吡啶环为侧链功能基的配体L1和L2可根据其环大小选择性地识别Na+或K+离子 ,与过渡金属离子形成 1∶1型配合物 ,而与Hg2 +,Cd2 +等离子则形成1∶2型配合物 .大环配体L3与Co2 +和Na+离子形成的双核配合物中两个冠醚环和一个Na+离子形成夹心配位结构 .L5环中有两个配位中心 ,因而可同时与两个Ru2 +离子配位 .L1和L2 均表现出对不同金属离子良好的液膜传输性能和传输选择性     

Response of a benzoxainone derivative linked to monoaza-15-crown-5 with divalent heavy metals

The response of a monoaza-15-crown-5 with an optically active aminobenzoxazinone moiety to divalent cations was investigated. The crown ether was found to undergo a strong emission shift to the blue when complexed with specific divalent metals that have ionic diameters between 1.9-2.4 A. Consequently the photoactive macrocycle is responsive to Mg(2+), Ca(2+), Ba(2+), Sr(2+), Cd(2+), and particularly responsive to Hg(2+)and Pb(2+). Macrocycle emission spectra are shown to be a function of cation concentration. Alkaline metal cations and smaller transition metals ions such as Ni(2+), Co(2+)and Zn(2+)do not cause significant changes in the macrocycle emission spectra. Emission, absorption, and complex stability constants are determined. Mechanisms of cation selectivity and spectral emission shifts are discussed. Challenges involving immobilization of the macrocycle while preserving its spectral response to cations are explored.