Saccharide imprinting of poly(aniline boronic acid) in the presence of fluoride

A new approach for the electrosynthesis of saccharide-imprinted poly(aniline boronic acid) is described. The method involves the formation of a saccharide-aminophenylboronic acid complex in the presence of fluoride to allow the electropolymerization of a self-doped, molecularly imprinted polyaniline. The formation of the anionic monomer complex enables electrochemical polymerization at near neutral pH (5-7) ensuring the incorporation of saccharide in the resulting, self-doped polymer. In this work, films were imprinted with D-fructose where saccharide-aminophenylboronic acid complexation occurred in the presence of one equivalent of fluoride. The selectivity toward D-fructose relative to D-glucose showed an increase of over 25% as a result of imprinting. In addition to the enhanced selectivity, to the best of our knowledge this is the first example of the electropolymerization of a self-doped polyaniline homopolymer under neutral pH conditions.     

Indirect Electrochemical Determination of Ribavirin Using Boronic Acid-Diol Recognition on a 3-Aminophenylboronic Acid-Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode (APBA/ERGO/GCE)

A novel method for the indirect electrochemical determination of ribavirin based on boronic acid-diol recognition was developed using the platform as the sensing element. The device was constructed using a 3-aminophenylboronic acid (APBA)-electrochemically reduced graphene oxide (ERGO) modified electrode. When the electrode was immersed in a solution of ribavirin, complexation of boronic acid groups of APBA with ribavirin occurred at the surface of the electrode and simultaneously caused steric hindrance, resulting in a current decrease because the ferricyanide redox probe was unable access the surface. Under the optimized conditions, a linear relationship was obtained between the relative change in current (%Δi) of [Fe(CN)₆]^3?/4?and the concentration of ribavirin at levels from 10.0 to 7.50?×?10²?ng mL^?1. The proposed electrochemical sensor performed with acceptable sensitivity and reproducibility and was successfully used to determine the content of ribavirin in an injection with satisfactory results.     

基于有机硼化合物的氟离子化学传感器的研究进展

有机硼化合物中硼原子空的pπ轨道使其作为路易斯酸能够选择性的结合氟离子,其与氟离子的结合破坏了硼中心与芳香取代基的pπ-π共轭,引起有机硼化合物光物理性质的变化。因此,有机硼化合物能够用作高选择性的氟离子化学传感器材料。本文从具有三芳基硼结构及硼酸或硼酸酯结构的这两类有机硼化合物出发,综述了它们在氟离子化学传感器领域的研究进展。     

A switchable self-doped polyaniline: interconversion between self-doped and non-self-doped forms

A novel strategy for the synthesis of a substituted polyaniline that can be switched between a self-doped and non-self-doped state is presented. The approach uses the complexation between boronic acid-substituted aniline, a diol (d-fructose), and fluoride to generate an anionic monomer. Under these conditions, chemical polymerization results in a self-doped, water-soluble, conducting polyaniline under neutral aqueous conditions. The self-doped polymer can be simply and reversibly converted to an insoluble non-self-doped form by reducing the concentration of fluoride. Characteristics of the polymerization reaction and the resulting polymer are discussed.     

Organoboron compounds as Lewis acid receptors of fluoride ions in polymeric membranes

Newly synthesized organoboron compounds – 4-octyloxyphenylboronic acid (OPBA) and pinacol ester of 2,4,6-trifluorophenylboronic acid (PE-PBA) – were applied as Lewis acid receptors of fluoride anions. Despite enhanced selectivity, the polymer membrane electrodes containing the lipophilic receptor OPBA exhibited non-Nernstian slopes of the responses toward fluoride ions in acidic conditions. Such behavior was explained by the lability of the B–O bond in the boronic acids, and the OH⁻/F⁻ exchange at higher fluoride content in the sample solution. In consequence, the stoichiometry of the OPBA–fluoride complexes in the membrane could vary during the calibration, changing the equilibrium concentration of the primary anion in membrane and providing super-Nernstian responses. The proposed mechanism was supported by ¹⁹F NMR studies, which indicated that the fluoride complexation proceeds more effectively in acidic solution leading mainly to PhBF₃⁻ species. Finally, the performances of the membranes based on the phenylboronic acid pinacol ester, with a more stable B–O bond, were tested. As it was expected, Nernstian fluoride responses were recorded for such membranes with worsened fluoride selectivity.     

Colorimetric fluoride ion sensing by polyborylated ferrocenes: structural influences on thermodynamics and kinetics

The thermodynamic factors underlying the use of ferroceneboronic esters as electrochemical or colorimetric fluoride ion sensors have been investigated through the synthesis of a range of systematically related derivatives differing in the number/nature of the boronic ester substituents and in the nature of ancillary ligands. Thus, if the shift in electrochemical potential associated with the conversion of one (or more) boronic ester group(s) to anionic boronate(s) on fluoride binding is sufficient to allow oxidation of the resulting host/guest complex by dioxygen, colorimetric sensing is possible. In practice, while monofunctional systems of the type CpFe[eta(5)-C(5)H(4)B(OR)(2)] offer selectivity in fluoride binding, electrochemical shifts in chloroform solution are insufficient to allow for a colorimetric response. Two chemical modification strategies have been shown to be successful in realizing a colorimetric sensor: (i) the use of the more strongly electron-donating Cp(*) ancillary ligand (which shifts the oxidation potential of both the free receptor and the resulting fluoride adduct cathodically by ca. -400 mV) and (ii) receptors featuring two or more binding sites and consequently a larger fluoride-induced electrochemical shift. Thus, in the case of [eta(5)-C(5)H(4)B(OR)(2)](2)Fe [(OR)(2) = OC(H)PhC(H)PhO, 2(s)], the binding of 2 equiv of fluoride gives an electrochemical shift (in chloroform) of -960 mV (cf. -530 mV for the corresponding monofunctional analogue, 1(s)). Related tris- and tetrakis-functionalized systems are also shown to be oxidized as the bis(fluoride) adducts, presumably because of fast oxidation kinetics, relative to the rate of the (electrostatically unfavorable) binding of a third equivalent of fluoride. Furthermore, the rate of sensor response (as measured by UV/vis spectroscopy) is found to be strongly enhanced by the presence of pendant (uncomplexed) three-coordinate boronic ester functions (e.g., a rate enhancement of 1-2 orders of magnitude for 3(s)/4(s) with respect to 2(s)) and/or delocalized aromatic substituents.     

Polymethacrylate polymers with appended aluminum(III)-tetraphenylporphyrins: Synthesis, characterization and evaluation as macromolecular ionophores for electrochemical and optical fluoride sensors

The synthesis and characterization of a novel polymethacylate polymer with covalently linked Al(III)-tetraphenylporphyrin (Al(III)-TPP) groups is reported. The new polymer is examined as a potential macromolecular ionophore for the preparation of polymeric membrane-based potentiometric and optical fluoride selective sensors. To prepare the polymer, an Al(III) porphyrin monomer modified with a methacrylate functionality is synthesized, allowing insertion into a polymethacrylate block copolymer (methyl methacrylate and decyl methacrylate) backbone. The resulting polymer can then be incorporated, along with appropriate additives, into conventional plasticized poly(vinyl chloride) films for testing electrochemical and optical fluoride response properties. The covalent attachment of the Al(III)-TPP ionophore to the copolymer matrix provides potentiometric sensors that exhibit significant selectivity for fluoride ion with extended lifetimes (compared to ion-selective membrane electrodes formulated with conventional free Al(III)-TPP structure). However, quite surprisingly, the attachment of the ionophore to the polymer does not eliminate the interaction of Al(III)-TPP structures to form dimeric species within the membrane phase in the presence of fluoride ion. Such interactions are confirmed by UV/visible spectroscopy of the blended polymeric films. Use of the new polymer-Al(III)-TPP conjugates to prepare optical fluoride sensors by co-incorporating a lipophilic pH indicator (4′,5′-dibromofluorescein octadecyl ester; ETH7075) is also examined and the resulting optical sensing films are shown to exhibit excellent selectivity for fluoride, with the potential for prolonged operational lifetime.     

以马来松香丙烯酸乙二醇酯为交联剂的咖啡因分子印迹电化学传感器

以咖啡因为模板分子, 含菲环骨架的马来松香丙烯酸乙二醇酯为交联剂, 甲基丙烯酸为功能单体, 在玻碳电极表面以自由基热聚合的方式制备分子印迹聚合物敏感膜, 构建了测定咖啡因的新型分子印迹膜电化学传感器. 通过循环伏安法、 差分脉冲伏安法及电化学交流阻抗法研究了传感器对咖啡因的响应特性. 结果表明, 在最佳的实验条件下, 传感器的峰电流与咖啡因浓度在3.00×10^-3~2.73 mmol/L范围内呈现良好的线性关系, 检出限(S/N=3)为1.12×10^-4 mmol/L. 传感器具有良好的选择性和重现性. 将该传感器用于可口可乐饮料中咖啡因含量的测定, 平均回收率为98.7%.     

Fluoride anion binding by cyclic boronic esters: influence of backbone chelate on receptor integrity

A systematic investigation of fluoride anion binding properties as a function of chelate backbone has been carried out for ferrocene functionalised boronic esters of the types FcB(OR)2 and fc[B(OR)2]2 [Fc = ferrocenyl = (eta5-C5H5)Fe(eta5-C5H4); fc = ferrocendiyl = Fe(eta5-C5H4)2]. Cyclic boronic esters containing a saturated five- or six-membered chelate ring are readily synthesized from ferrocene, and selectively bind fluoride via Lewis acid/base chemistry in chloroform solution. The resulting complexes are characterized by relatively weak fluoride binding (e.g.K = 35.8 +/- 9.8 M(-1) for FcBO2C2H2Ph2-S,S), and by cathodic shifts in the ferrocene oxidation potential that form the basis for electrochemical or colorimetric fluoride detection. The fluoride selectivity of these systems is attributed to relatively weak Lewis acidity, resulting in weak F- binding, and essentially no binding of potentially competitive anions. By contrast, more elaborate Lewis acid frameworks based on calix[4]arene (calixH4), such as (FcB)2calix or fcB2calix, do not survive intact exposure to standard fluoride sources (e.g. [nBu4N]F.xH2O solutions in chloroform or acetonitrile). Instead B-O bond cleavage occurs yielding the parent calixarene; the differences between alkoxo- and aryloxo-functionalised derivatives can be rationalised, at least in part, by consideration of the differences in electron donating capabilities of RO- (R = alkyl, aryl).     

A Selective Film Based on Poly(3‐octylthiophene) Doped with Dihydroxyanthraquinone Sulfonate

A stable film of poly(3‐octylthiophene)–dihydroxyanthraquinone sulfonate has been synthesized electrochemically in non‐aqueous solution. The incorporation of dihydroxyanthraquinone sulfonate as an anionic complexing ligand into poly(3‐octylthiophene) film during electropolymerization was achieved and copper ions were accumulated by reduction on the electrode surface. The presence of dihydroxyanthraquinone sulfonate during the electrochemical polymerization of 3‐octylthiophene is shown to impact the sensitivity and the stability of the organic conducting film electrode response. The electroanalysis of copper(II) ions using conducting polymer electrode was achieved by differential pulse anodic stripping voltammetry with remarkable selectivity. The analytical performance was evaluated and linear calibration graphs were obtained in the concentration range of 50–400 ng mL^?1 copper(II) ion for 240 seconds accumulation time and the limit of detection was found to be 7.8 ng mL^?1. To check the selectivity of the proposed stripping voltammetric method for copper(II) ion, various metal ions as potential interferents were tested. The developed method was applied to copper(II) determination in certified reference material, NWRI‐TMDA‐61, trace elements in fortified water.     

Molecularly imprinted polymers (MIPs) combined with nanomaterials as electrochemical sensing applications for environmental pollutants

It is known that environmental pollution, which is the result of human-induced industrial, domestic, and agricultural practices, poses a threat to our planet. The increasing human population caused several problems such as water and air pollution, which have reached levels threatening human health. There are many different hazardous chemical and biological environmental pollutants in soil, air, and wastewater. It is extremely important to evaluate these health risks and detect these pollutants. The use of electrochemical methods for the detection of environmental pollutants comes to the forefront recently with advantages such as sensitivity, fast response, low cost, and practical use by miniaturization. The molecular imprinting technique is a popular method used for substance analysis by creating a cavity specific to the substance to be analyzed with the polymer used. The use of molecularly imprinted polymer in electrochemical methods and its modification with various nanomaterials bring advantages such as high selectivity, robustness, and sensitivity to electrochemical sensors. Here, the sensitive determination of environmental pollutants with different nanomaterial-modified molecularly imprinted polymer-based electrochemical sensors, the use of different polymerization techniques, and nano-sized modification agents in sensors are evaluated by reviewing recent studies in the literature.     

Poly(glyceryl glycerol): A multi‐functional hydrophilic polymer for labeling with boronic acids

The synthesis of poly(glyceryl glycerol) (PGG), a polymer featuring a polyethylene oxide backbone and 1,2‐diol groups in every repeating unit, is presented. PGG was prepared by monomer‐activated ring‐opening polymerization of (dl ?1,2‐isopropylidene glyceryl) glycidyl ether, introducing a functional azido‐ or bromo‐head group to each chain. The 1,2‐diol groups, which were released by acidic deprotection, readily reacted with boronic acid derivatives, enabling the attachment of functional moieties under mild aqueous conditions. PGG was conjugated to poly(l ‐lactide) (PLLA) via azide‐alkyne cycloaddition and the resulting copolymer assembled into nanoparticles of 70 nm diameter in aqueous solution. Labeling of the PGG–PLLA particles was achieved by simple mixing with a boronic acid‐functional fluorophore. The labeling efficiency was determined by fluorescence spectroscopy to be 85.5% for boronic acid‐functional rhodamine B compared with 0.2% for plain rhodamine B. The strong interaction of PGG with boronic acids is ascribed to its polyol structure. This study demonstrates the usefulness and versatility of PGG as a hydrophilic polymer for possible biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1822–1830     

低头-头链含量的聚偏氟乙烯合成

研究了偏氟乙烯的聚合条件与其聚合物的头-头链含量的关系。实验表明聚合物的头-头链的含量与聚合温度有关,而与引发剂的种类无关。因而,可以在较低的聚合温度下聚合制得带有低的头-头结构(约3％)的聚偏氟乙烯。将聚合物链的A结构含量对其熔点作图,得一直线,可表示为方程式A=24.8+0.362T_m(％)。     

Fluorescent boron bis(phenolate) with association response to chloride and dissociation response to fluoride

Addition of chloride ions to boron bis(phenolate) 5 in dichloromethane solution produces a selective fluorescence decrease. The fluorescence change is believed to be caused by associative hydrogen bonding between the chloride ion and two boronic acid groups. While addition of fluoride ions to bis(phenolate) 5 generates a purple colorimetric response, the colorimetric response is caused by fluoride induced B-O bond cleavage and air oxidation of the phenolate anion formed by this dissociation.     

A stable glucose biosensor prepared by co-immobilizing glucose oxidase into poly(p-chlorophenol) at a platinum electrode

An amperometric glucose biosensor was successfully developed by electrochemical polymerization of p-chlorophenol (4-CP) at a Pt electrode in the presence of glucose oxidase. The amperometric response of this biosensor to hydrogen peroxide, formed as the product of enzymatic reaction, was measured at a potential of 0.6 V (vs. SCE) in phosphate buffer solution. The performances of sensors, prepared at different monomer concentrations and polymerization potentials, were investigated in detail. The biosensor prepared under optimal conditions had a linear response to glucose ranging from 2.5 x 10(-4) to 1.5 x 10(-2) mol L(-1) with a correlation coefficient of 0.997 and a response time of less than 2 s. Substrate selectivity of the polymer-based enzyme electrode was tested for coexisting interferents such as uric acid and ascorbic acid, and no discernible response was observed. After 90 days, the response of the biosensor remained almost unchanged, indicating very good stability.     

Immobilization of tyrosinase on poly(indole-5-carboxylic acid) evidenced by electrochemical and spectroscopic methods

A conducting, polymeric film of poly(indole-5 carboxylic acid) has been prepared by electrochemical polymerization for covalent immobilization of an enzyme belonging to the family of phenoloxidases-tyrosinase. The polymer was characterized by cyclic voltammetry, UV-VIS and Raman spectroscopy in a buffer solution. As the polymer contains pendant carboxylic groups one-step carbodiimide method was used to immobilize tyrosinase on the polymer matrix. Immobilization of tyrosinase was confirmed by surface enhanced resonance Raman scattering spectra (SERRS) and by cyclic voltammetry as well. Tyrosinase was shown to retain its biological activity when being immobilized on the polymer surface. As proved by the electrochemical and spectroelectrochemical (UV-VIS) experiments, tyrosinase covalently bonded to the polymer matrix effectively catalyzes oxidation of catechol. The reduction current of o-quinones was measured as a function of catechol concentration. The linear dependence was found to be 15 microM of catechol with sensitivity of 250 mA/M cm2.     

铜(Ⅱ)离子印迹聚合物的制备及性能

选择油酸为功能单体, 二乙烯基苯为交联剂, 应用乳液聚合方法制备了Cu(Ⅱ)离子印迹聚合物, 并对其性能和吸附机理进行了研究.     

Boronic acid building blocks: tools for sensing and separation

In this feature article the use of boronic acids to monitor, identify and isolate analytes within physiological, environmental and industrial scenarios is discussed. Boronic acids recognise diol motifs through boronic ester formation and interact with anions generating boronates, as such they have been exploited in sensing and separation protocols for diol appended molecules such as saccharides and anions alike. Therefore robust molecular sensors with the capacity to detect chosen molecules selectively and signal their presence continues to attract substantial attention, and boronic acids have been exploited with some success to monitor the presence of various analytes. Reversible boronic acid-diol interactions have also been exploited in boron affinity chromatography realising new separation domains through the same binding events. Boronic acid diol and anion interactions pertaining to sensing and separation are surveyed.     

可溶性聚3-[(二茂铁甲酸乙酯)三乙氧基]氧基噻吩的合成与性质表征

采用化学聚合方法合成了一种含二茂铁电活性基团的新型导电聚噻吩衍生物聚3-[(二茂铁甲酸乙酯)三乙氧基]氧基噻吩, 用1H NMR和红外光谱等方法对其结构进行了表征. 实验结果表明, 该聚合物可溶于三氯甲烷、四氢呋喃和丙酮等有机溶剂, 并且二茂铁在聚合物中依然保持良好的氧化还原活性, 对钠离子具有良好的选择性络合作用.     

SYNTHESIS OF POLY(VINYLIDENE FLUORIDE) WITH LOW CONTENTS OF HEAD-TO-HEAD CHAIN

The relations between polymerization conditions of vinylidene fluoride and contents of head-tohead chain in the polymer have been studied. It shows that the contents of head-to-head chain of the polymer are related to its polymerization temperature, but are not related with the kinds of initiators used. Therefore, poly(vinylidene fluoride) with low contents of head-to-head chain (ca. 3%) can be prepared under lower polymerization temperature. Plot of the contents of A chains against melting points of the polymer is linear, which can be expressed by an equation: A=24.8 + 0.362 T_m(%).