Organic–Inorganic Hybrid Films of the Sulfate Dawson Polyoxometalate, [S₂W₁₈O₆₂]^4–, and Polypyrrole for Iodate Electrocatalysis

This article references 60 other publications.

1. 1

   Yang, B.; Pignatello, J. J.; Qu, D.; Xing, B. Reoxidation of photoreduced polyoxotungstate ([PW₁₂O₄₀]^4–) by different oxidants in the presence of a model pollutant. Kinetics and reaction mechanism. J. Phys. Chem. A 2015, 119, 1055– 1065,  DOI: 10.1021/jp510036x

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   1

   Reoxidation of Photoreduced Polyoxotungstate ([PW12O40]4-) by Different Oxidants in the Presence of a Model Pollutant. Kinetics and Reaction Mechanism

   Yang, Bing; Pignatello, Joseph J.; Qu, Dong; Xing, Baoshan

   Journal of Physical Chemistry A (2015), 119 (6), 1055-1065CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)

   Polyoxometalates (POMs) are attractive photocatalysts for water purifn. Reoxidn. of the photoreduced form of POM by a bulk oxidant is an important step in the cycle yet has received little attention. Photoreduced phosphotungstate ([PW12O40]4-; POM-) was reacted with bulk oxidants, XOOX, including H2O2 (HP), peroxyacetic acid (PAA), peroxymonosulfate (MS), peroxydisulfate (DS), and dioxygen (O2), in the presence of the model pollutant 2-propanol under various conditions, and the stoichiometries and rate laws were established. A unified chain reaction is proposed in which the rate-limiting step is outer-sphere one-electron transfer to XOOX yielding •OX (•OH, SO4•- or CH3CO2•). This step is proton-assisted when the leaving group OX- is a strong base (OH-), but independent of [H+] when the leaving group is a weak base (O2•-, SO42-). The rate of this step follows the order PAA > MS > O2 > HP > DS at pH 1.3, but O2 > PAA > MS > HP > DS at pH 4.1. The chain includes a no. of POM--regenerating steps that, with some bulk oxidants (esp. MS and DS), leads to further consumption of bulk oxidant and transformation of pollutant. These steps were identified through effects of conditions on reaction stoichiometry, order with respect to [POM-], and suppression by POM. Chloride short-circuits the chain by reducing •OX and forming Cl2•-, which scavenges POM-. The results provide insight into POM-catalyzed redox reactions in water purifn. and selective redox applications.

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2. 2

   Haviv, E.; Shimon, L. J.; Neumann, R. Photochemical reduction of CO₂ with visible light using a polyoxometalate as photoreductant. Chem. Eur. J 2017, 23, 92– 95,  DOI: 10.1002/chem.201605084

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   Photochemical reduction of CO2 with visible light using a polyoxometalate as photoreductant

   Haviv, Eynat; Shimon, Linda J. W.; Neumann, Ronny

   Chemistry - A European Journal (2017), 23 (1), 92-95CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)

   The photochem. redn. of CO2 to CO requires two electrons and two protons that, in the past, have been derived from sacrificial amine donors that are also non-innocent in the catalytic cycle. Towards the realization of a water-splitting reaction as the source of electrons and protons for CO2 redn., we have found that a reduced acidic polyoxometalate, H5PWV2W10O40, is a photoactive electron and proton donor with visible light through excitation of the intervalence charge-transfer band. Upon linking the polyoxometalate to a dirhenium mol. catalyst, a cascade of transformations occurs where the polyoxometalate is electrochem. reduced at a relatively low neg. potential of 1.3 V vs. Ag/AgNO3 and visible light, a 60 W tungsten lamp, or a red LED is used to transfer electrons from the polyoxometalate to the dirhenium catalyst active for the selective redn. of CO2 to CO.

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3. 3

   Wang, H.; Hamanaka, S.; Nishimoto, Y.; Irle, S.; Yokoyama, T.; Yoshikawa, H.; Awaga, K. In operando X-ray absorption fine structure studies of polyoxometalate molecular cluster batteries: polyoxometalates as electron sponges. J. Am. Chem. Soc. 2012, 134, 4918– 4924,  DOI: 10.1021/ja2117206

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   In Operando X-ray Absorption Fine Structure Studies of Polyoxometalate Molecular Cluster Batteries: Polyoxometalates as Electron Sponges

   Wang, Heng; Hamanaka, Shun; Nishimoto, Yoshio; Irle, Stephan; Yokoyama, Toshihiko; Yoshikawa, Hirofumi; Awaga, Kunio

   Journal of the American Chemical Society (2012), 134 (10), 4918-4924CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

   The authors carried out in operando Mo K-edge x-ray absorption fine structure measurements on the rechargeable mol. cluster batteries (MCBs) of polyoxometalates (POMs), in which a Keggin-type POM, [PMo12O40]3-, was used as a cathode active material with a Li metal anode. The POM-MCBs exhibit a large capacity of ∼270 (A h)/kg in a voltage range between V = 4.0 V and V = 1.5 V. X-ray absorption near-edge structure analyses demonstrate that all 12 Mo6+ ions in [PMo12O40]3- are reduced to Mo4+ in the discharging process. This means the formation of a super-reduced state of the POM, namely, [PMo12O40]27-, which stores 24 electrons, and this electron no. can explain the large capacity of the POM-MCBs. Also, extended x-ray absorption fine structure analyses reveal the mol. structure of [PMo12O40]27-, which is slightly reduced in size compared to the original [PMo12O40]3- and involves Mo4+ metal-metal-bonded triangles. D. functional theory calcns. suggest that these triangles are formed because of the large no. of addnl. electrons in the super-reduced state.

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4. 4

   Li, F.; Carpenter, S. H.; Higgins, R. F.; Hitt, M. G.; Brennessel, W. W.; Ferrier, M. G.; Cary, S. K.; Lezama-Pacheco, J. S.; Wright, J. T.; Stein, B. W. Polyoxovanadate–alkoxide clusters as a redox reservoir for iron. Inorg. Chem. 2017, 56, 7065– 7080,  DOI: 10.1021/acs.inorgchem.7b00650

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   Polyoxovanadate-Alkoxide Clusters as a Redox Reservoir for Iron

   Li, Feng; Carpenter, Stephanie H.; Higgins, Robert F.; Hitt, Mark G.; Brennessel, William W.; Ferrier, Maryline G.; Cary, Samantha K.; Lezama-Pacheco, Juan S.; Wright, Joshua T.; Stein, Benjamin W.; Shores, Matthew P.; Neidig, Michael L.; Kozimor, Stosh A.; Matson, Ellen M.

   Inorganic Chemistry (2017), 56 (12), 7065-7080CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)

   Inspired by the multielectron redox chem. achieved using conventional org.-based redox-active ligands, the authors have characterized Fe-functionalized polyoxovanadate-alkoxide clusters in which the metal oxide scaffold functions as a three-dimensional, electron-deficient metalloligand. Four heterometallic clusters were prepd. through sequential redn., demonstrating that the metal oxide scaffold is capable of storing up to four electrons. These reduced products were characterized by cyclic voltammetry, IR, electronic absorption, and 1H NMR spectroscopies. Also, Mossbauer and x-ray absorption spectroscopies suggest that the redox events involve primarily the V ions, while the Fe atoms remained in the 3+ oxidn. state throughout the redox series. In this sense, the V portion of the cluster mimics a conventional org.-based redox-active ligand bound to an Fe(III) ion. Magnetic coupling within the hexanuclear cluster was characterized using SQUID magnetometry. Overall, the results suggest extensive electronic delocalization between the metal centers of the cluster core. These results demonstrate the ability of electronically flexible, reducible metal oxide supports to function as redox-active reservoirs for transition-metal centers.

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5. 5

   Chen, W.-H.; Mi, J.-X. A new redox-based approach for synthesizing a mixed-valence hybrid polymolybdate uncommonly bicapped by Cr (III) coordination complexes. Polyhedron 2015, 85, 117– 123,  DOI: 10.1016/j.poly.2014.08.038

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   A new redox-based approach for synthesizing a mixed-valence hybrid polymolybdate uncommonly bicapped by Cr(III) coordination complexes

   Chen, Wu-Hua; Mi, Jin-Xiao

   Polyhedron (2015), 85 (), 117-123CODEN: PLYHDE; ISSN:0277-5387. (Elsevier Ltd.)

   The grafting of Cr(III) coordination complexes as capping units onto polyoxometalates (POMs), still remains a considerable synthetic challenge due to the difficulty in replacement of aqua-ligands in [Cr(H2O)6]3+ complexes. A new synthetic method was developed, from in situ reduced dichromate ions, to generate Cr(III) ions, which were designed to coordinate to org. ligands simultaneously, while they were linking to nucleophilic oxygen atoms of the POM. Using two-step redox reactions, the authors successfully synthesized a new mixed-valence hybrid polymolybdate, [H3O][Hdma]3[H2phen]{[Cr(phen)]2[MoV9MoVI3O36(PO4)]}·nH2O (n ≈ 1) (1) (dma = dimethylamine (C2H7N); phen = 1,10-phenanthroline (C12H8N2)) under hydrothermal conditions. The single-crystal x-ray diffraction anal. indicated that compd. 1 contains the first reported example of {[Cr(phen)]2[MoV9MoVI3O36(PO4)]}6- polyanion, a type of Keggin-structural heteropoly blue building block, uncommonly bicapped by Cr(III) coordination complexes. The structure was further characterized by FTIR, XPS, UV-visible spectroscopy, elemental anal., cerate oxidimetry, and thermal anal. measurements. This study provides a new method for the syntheses of other novel capped structural POMs using rate-controlling redox steps.

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6. 6

   Dong, B.-X.; Wu, Y.-C.; Tian, H.; Liu, C.-B.; Liu, W.-L.; Teng, Y.-L. Synthesis, Crystal Structure and Electrochemical Properties of A New 2D Network Containing Linear {ε-H₂PMo₈VMo₄^VIO₄₀Zn₄}^∞ Inorganic Chain. J. Clust. Sci. 2016, 27, 361– 371,  DOI: 10.1007/s10876-015-0935-1

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   Miras, H. N.; Vilà-Nadal, L.; Cronin, L. Polyoxometalate based open-frameworks (POM-OFs). Chem. Soc. Rev. 2014, 43, 5679– 5699,  DOI: 10.1039/C4CS00097H

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   Polyoxometalate based open-frameworks (POM-OFs)

   Miras, Haralampos N.; Vila-Nadal, Laia; Cronin, Leroy

   Chemical Society Reviews (2014), 43 (16), 5679-5699CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)

   A review. Polyoxometalate-based open frameworks (POM-OFs) are extended architectures incorporating metal-oxide cluster units and comprise an emergent family of materials with a large diversity of topologies, structural flexibility and functionality at the nanoscale. Not only do POM-OFs present a wide range of configurable structures, but also a have a vast array of phys. properties which reflect the properties of the various 'modular' mol. inputs. Here, the authors describe the methodologies that can be used to construct POM-OF materials with important catalytic, electronic, and structural properties and discuss the advantages compared to the metal org. framework analogs. The authors also show that it is possible to construct POM-OF materials and design and/or fine tune their functionality by manipulating the initially generated building block libraries as well as by controlling the self-assembly towards the specific intermediate (POM) species which is the chem. and structural "information" carrier of the targeted POM-OF material.

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8. 8

   Zhao, J.-W.; Li, Y.-Z.; Chen, L.-J.; Yang, G.-Y. Research progress on polyoxometalate-based transition-metal–rare-earth heterometallic derived materials: synthetic strategies, structural overview and functional applications. Chem. Commun. 2016, 52, 4418– 4445,  DOI: 10.1039/C5CC10447E

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   Research progress on polyoxometalate-based transition-metal-rare-earth heterometallic derived materials: synthetic strategies, structural overview and functional applications

   Zhao, Jun-Wei; Li, Yan-Zhou; Chen, Li-Juan; Yang, Guo-Yu

   Chemical Communications (Cambridge, United Kingdom) (2016), 52 (24), 4418-4445CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)

   A review. A review with the rapid development of science and technol. and the trend of multidisciplinary pervasion, POM-based TM-RE heterometallic chem. (POM = polyoxometalate, TM = transition-metal, RE = rare-earth) has become one of the most rapidly growing and challengeable areas of inorg. chem. due to the impressive structural diversities, various chem. compns. and potential applications of these materials in magnetism, optics, electrochem., electrocatalysis and materials science. A review over the past several years, continuous interest and persisting efforts were dedicated to the prepn. and exploration of POM-based TM-RE heterometallic derived materials (PTRHDMs), which led to more than two hundred PTRHDMs. A review, the authors summarize the structural types of reported PTRHDMs together with synthetic strategies, structural motifs and relevant functional applications. A review the exciting array of this emerging research theme presages continuous growth and great vitality. A review in the last section, some prospects of this branch are also presented and possible guidance for future work is outlined.

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9. 9

   Okuhara, T.; Mizuno, N.; Misono, M. Catalytic chemistry of heteropoly compounds. In Adv. Catal., Elsevier: 1996; 41, pp 113– 252.

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10. 10

    Walsh, J. J.; Bond, A. M.; Forster, R. J.; Keyes, T. E. Hybrid polyoxometalate materials for photo (electro-) chemical applications. Coord. Chem. Rev. 2016, 306, 217– 234,  DOI: 10.1016/j.ccr.2015.06.016

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    Hybrid polyoxometalate materials for photo(electro-) chemical applications

    Walsh, James J.; Bond, Alan M.; Forster, Robert J.; Keyes, Tia E.

    Coordination Chemistry Reviews (2016), 306 (Part_1), 217-234CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)

    A review. Polyoxometalate (POM) based supramol. assemblies have received significant attention over recent years because of their unique and diverse redox and photochem. behavior and their potential value across a range of important light driven applications such as photo-driven synthesis and photocatalysis. This review explores the dominant approaches to assembly of polyoxometalates into supramol. materials, both covalent and electrostatic, with particular focus on charge transfer materials and those capable of sensitized photoelectrocatalysis. The integration of POMs as components in devices such as dye sensitized solar cells, electrocatalytic photoanodes, sensing and waste remediation are considered.

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11. 11

    Yaqub, M.; Walsh, J. J.; Keyes, T. E.; Proust, A.; Rinfray, C.; Izzet, G.; McCormac, T.; Forster, R. J. Electron transfer to covalently immobilized Keggin polyoxotungstates on gold. Langmuir 2014, 30, 4509– 4516,  DOI: 10.1021/la4048648

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    11

    Electron Transfer to Covalently Immobilized Keggin Polyoxotungstates on Gold

    Yaqub, Mustansara; Walsh, James J.; Keyes, Tia E.; Proust, Anna; Rinfray, Corentin; Izzet, Guillaume; McCormac, Timothy; Forster, Robert J.

    Langmuir (2014), 30 (15), 4509-4516CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)

    Spontaneously adsorbed monolayers were formed on Au electrodes using a Keggin polyoxotungstate with covalently attached alkanethiol linkers of two different lengths. Films of both polyoxotungstates show two well-defined redn. processes assocd. with the polyoxotungstate centers where the ionic liq., [BMIM][BF4], acts as supporting electrolyte. The surface coverages are both less than that expected for a close-packed monolayer. For the short and long linkers, the voltammetric response can be described in terms of the Butler-Volmer response involving a surface confined species using std. heterogeneous electron transfer rate consts. of 170 and 140 s-1 for the 1st redn. and 150 and 100 s-1 for the 2nd redn. processes, resp. The rate of electron transfer to a soln. phase redox probe, ferrocyanide, is significantly more sensitive to the length of the linker than the rate of electron transfer to the tungstate centers. This behavior probably arises due to potential-induced changes in the film structure.

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12. 12

    Imar, S.; Yaqub, M.; Maccato, C.; Dickinson, C.; Laffir, F.; Vagin, M.; McCormac, T. Nitrate and Nitrite Electrocatalytic Reduction at Layer-by-Layer Films Composed of Dawson-type Heteropolyanions Mono-substituted with Transitional Metal Ions and Silver Nanoparticles. Electrochim. Acta 2015, 184, 323– 330,  DOI: 10.1016/j.electacta.2015.10.082

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    12

    Nitrate and Nitrite Electrocatalytic Reduction at Layer-by-Layer Films Composed of Dawson-type Heteropolyanions Mono-substituted with Transitional Metal Ions and Silver Nanoparticles

    Imar, Shahzad; Yaqub, Mustansara; Maccato, Chiara; Dickinson, Calum; Laffir, Fathima; Vagin, Mikhail; McCormac, Timothy

    Electrochimica Acta (2015), 184 (), 323-330CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)

    Dawson-type heteropolyanions (HPAs) mono-substituted with transitional metal ions (α2-[P2W17O61FeIII]8-, α2-[P2W17O61CuII]8- and α2-[P2W17O61NiII]8-) have exhibited electrocatalytic properties towards nitrate and nitrite redn. in slightly acidic media (pH 4.5). The immobilization of these HPAs into H2O-processable films developed via layer-by layer assembly with polymer-stabilized Ag nanoparticles led to the fabrication of the electrocatalytic interfaces for both nitrate and nitrite redn. The LBL assembly as well as the changes in the HPA properties by immobilization was characterized by electrochem. methods. The effects of the substituent ions, outer layers and the cationic moieties used for the films assembly of the developed film on the performances of nitrate electrocatalysis was elucidated.

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13. 13

    Zhang, H.-Y.; Miao, A.-J.; Jiang, M. Fabrication, characterization and electrochemistry of organic–inorganic multilayer films containing polyoxometalate and polyviologen via layer-by-layer self-assembly. Mater. Chem. Phys. 2013, 141, 482– 487,  DOI: 10.1016/j.matchemphys.2013.05.047

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    13

    Fabrication, characterization and electrochemistry of organic-inorganic multilayer films containing polyoxometalate and polyviologen via layer-by-layer self-assembly

    Zhang, Hong-Yu; Miao, Ai-Jing; Jiang, Min

    Materials Chemistry and Physics (2013), 141 (1), 482-487CODEN: MCHPDR; ISSN:0254-0584. (Elsevier B.V.)

    The novel org.-inorg. multilayer films contg. poly(butanyl viologen) (abbreviated as PBV) and phosphomolybdic acid (H3PMo12O40, abbreviated as PMo12) were fabricated on quartz slides, Si wafers and glassy C electrode by the layer-by-layer self-assembly technique. The highly ordered multilayer films were characterized by the UV-visible spectroscopy, FTIR spectroscopy, XPS, x-ray reflectometry (XRR), Atomic force microscopy (AFM) and cyclic voltammetry. UV-visible spectra revealed that the growth of the films for each deposition cycle was reproducible. FTIR and XPS spectra confirmed the incorporation of PBV and PMo12 into the multilayer films. XRR revealed the film thickness at nanoscale, and AFM showed film surface with uniform and smooth morphol. The electrochem. behavior of the multilayer films at room temp. was studied. As a result, the films presented good electrocatalytic activity toward BrO3-, H2O2 and NO2-, providing valuable information for exploring the potential applications in BrO3- sensors.

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14. 14

    Liu, R.; Li, S.; Yu, X.; Zhang, G.; Zhang, S.; Yao, J.; Zhi, L. A general green strategy for fabricating metal nanoparticles/polyoxometalate/graphene tri-component nanohybrids: enhanced electrocatalytic properties. J. Mater. Chem. 2012, 22, 3319– 3322,  DOI: 10.1039/c2jm15875b

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    A general green strategy for fabricating metal nanoparticles/polyoxometalate/graphene tri-component nanohybrids: enhanced electrocatalytic properties

    Liu, Rongji; Li, Shiwen; Yu, Xuelian; Zhang, Guangjin; Zhang, Suojiang; Yao, Jiannian; Zhi, Linjie

    Journal of Materials Chemistry (2012), 22 (8), 3319-3322CODEN: JMACEP; ISSN:0959-9428. (Royal Society of Chemistry)

    The well-defined metal NPs@POM-GNS tri-component nanohybrids were synthesized by a green, facile, 1-pot method. The obtained nanohybrids exhibited exciting electrocatalytic activity for MeOH and formic acid oxidn.

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15. 15

    Yaqub, M.; Walsh, J.; Laffir, F.; Olstoorn, P.; Kailas, L.; Forster, R.; Keyes, T. E.; Vagin, M.; McCormac, T. Polypyrrole entrapped 18-molybdodisulphate anion for the detection of hydrogen peroxide. Electrochim. Acta 2018, 287, 78– 86,  DOI: 10.1016/j.electacta.2018.08.053

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    Polypyrrole entrapped 18-molybdodisulphate anion for the detection of hydrogen peroxide

    Yaqub, Mustansara; Walsh, James; Laffir, Fathima; Olstoorn, Paula; Kailas, Lekshmi; Forster, Robert; Keyes, Tia E.; Vagin, Mikhail; McCormac, Timothy

    Electrochimica Acta (2018), 287 (), 78-86CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)

    Dawson-type 18-molybdodisulfate anion [S2Mo18O62]4-has been immobilized within polypyrrole film by means of electrochem. polymn. The polymer modified electrodes have been characterized with voltammetry and surface based techniques. The noticeable change in electrochem. properties of [S2Mo18O62]4- has been obsd. with immobilization, which is favors its electrocatalytic performance. Hydrogen peroxide redn. in neutral pH as a std. system for electrocatalytic properties assessment has been studied on composite film-modified electrodes and showed the sensitivity of 127 mAM-1cm-2. Developed system showed high stabilities towards redox switching and peroxide redn.

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16. 16

    Gomez-Romero, P. Hybrid organic–inorganic materials─in search of synergic activity. Adv. Mater. 2001, 13, 163– 174,  DOI: 10.1002/1521-4095(200102)13:3<163::AID-ADMA163>3.0.CO;2-U

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    Hybrid organic-inorganic materials-in search of synergic activity

    Gomez-Romero, Pedro

    Advanced Materials (Weinheim, Germany) (2001), 13 (3), 163-174CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH)

    A review with 304 refs. describing the work developed in the field of functional hybrid materials, esp. those contg. conducting org. polymers (COPs), in combination with a variety of inorg. species, from mol. to extended phases, including clusters and nano-sized inorg. particles. Depending on the dominating structural matrix, we distinguish and analyze org.-inorg. (OI) hybrids, nanocomposite materials, and inorg.-org. (IO) phases. These materials were used in a wide variety of applications, including energy-storage applications, electrocatalysis, the harnessing of electrochromic and photo-electrochromic properties, application in display devices, photovoltaics, and novel energy-conversion systems, proton-pump electrodes, sensors, or chemiresistive detectors, which work as artificial "noses".

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17. 17

    Shimidzu, T.; Ohtani, A.; Aiba, M.; Honda, K. Electrochromism of a conducting polypyrrole–phosphotungstate composite electrode. J. Chem. Soc., Faraday Trans. 1 1988, 84, 3941– 3949,  DOI: 10.1039/f19888403941

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    Electrochromism of a conducting polypyrrole-phosphotungstate composite electrode

    Shimidzu, Takeo; Ohtani, Akira; Aiba, Masaji; Honda, Kenichi

    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases (1988), 84 (11), 3941-9CODEN: JCFTAR; ISSN:0300-9599.

    A phosphotungstate-anion (PT)-incorporated polypyrrole (PPy/PT) electrode was prepd. by electrochem. polymn. in H2O contg. both pyrrole and the Na salt of PT. The PPy/PT electrode showed 2 redox peaks accompanying electrochromism. The peak at higher potential corresponds to an oxidn.-redn. of the incorporated PT, and the other at lower potential corresponds to that of the PPy. The incorporated PT is relased from the PPy matrix in neutral aq. soln. (pH 7) and is not released in acidic aq. soln. (pH 2) when the PPy is reduced at < -400 mV vs. SCE. The PPy/PT electrode in neutral soln. showed blue, red and yellow colors corresponding to the different redox states of the PPy/PT. However, the PPy/PT electrode in acidic soln. showed blue, red and blue-purple. The blue and yellow were assigned to the oxidative and the reductive PPy, resp. The red and blue-purple were assigned to the PT in the oxidative and the reductive PPy matrix, resp. The red color of the PT is a result of interaction between the incorporated PT and pyrrole moiety. The PPy/PT composite electrode is multielectrochromic.

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18. 18

    Hölscher, M.; Englert, U.; Zibrowius, B.; Hölderich, W. F. (H₃N(CH₂)₆NH₃)₄ [W₁₈P₂O₆₂]·3H₂O, ein mikroporöser Festkörper aus Dawson-Anionen und Hexamethylendiamin. Angew. Chem. 1994, 106, 2552– 2554,  DOI: 10.1002/ange.19941062325

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    18

    (H3N(CH2)6NH3)4[W18P2O62].3H2O, a microporous solid from Dawson anions and hexamethylenediamine

    Holscher, Markus; Englert, Ulli; Zibrowius, Bodo; Holderich, Wolfgang

    Angewandte Chemie (1994), 106 (23/24), 2552-4 (See also Angew. Chem., Int. Ed. Engl., 1994, 33(23/24), 2491-3)CODEN: ANCEAD; ISSN:0044-8249. (VCH)

    (H3N(CH2)6NH3)4[W18P2O62].3H2O, a microporous solid from Dawson anions, was prepd. by the hydrothermal reaction of W, WO3, H3PO4, and 1,6-hexamethylenediamine. The compd. is orthorhombic, space group Pmmn, Z = 2, R = 0.057, Rw = 0.053. The structure consists of discrete Dawson anions surrounded by 1,6-hexamethylenediamine in such a way that the protonated amino groups of 1 mol. connect 2 Dawson units. Thermoanal. shows that the compd. becomes amorphous at ∼ 200° and at 200-500° the diamine decompd. and the anion was oxidized.

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19. 19

    Zhang, J.; Bond, A. M.; Richardt, P. J.; Wedd, A. G. Voltammetric Reduction of α-and γ*-[S₂W₁₈O₆₂]^4– and α-, β-, and γ-[SiW₁₂O₄₀]^4–: Isomeric Dependence of Reversible Potentials of Polyoxometalate Anions Using Data Obtained by Novel Dissolution and Conventional Solution-Phase Processes. Inorg. Chem. 2004, 43, 8263– 8271,  DOI: 10.1021/ic049043x

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    19

    Voltammetric Reduction of α- and γ*-[S2W18O62]4- and α-, β-, and γ-[SiW12O40]4-: Isomeric Dependence of Reversible Potentials of Polyoxometalate Anions Using Data Obtained by Novel Dissolution and Conventional Solution-Phase Processes

    Zhang, Jie; Bond, Alan M.; Richardt, Peter J. S.; Wedd, Anthony G.

    Inorganic Chemistry (2004), 43 (26), 8263-8271CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)

    Comparative studies on the voltammetric redn. of the α and γ* isomers of Dawson [S2W18O62]4- and α, β, and γ forms of Keggin [SiW12O40]4- polyoxometalate anions were undertaken. For the 6 reversible 1-electron [S2W18O62]4-/5-/6-/7-/8-/9-/10- processes in MeCN, reversible potentials (E0') are independent of isomeric form within exptl. error (±5 mV). However, because both the α and γ* isomers of [Bu4N]4[S2W18O62] are insol. in H2O, solid-state voltammetric studies with microcrystals adhered to electrode surfaces in contact with aq. Et4NCl and Bu4NCl electrolyte media were also possible. Although no isomeric distinction was again detected in the solid-state studies, redn. of adhered solid by ≥4 electron equiv. led to rapid dissoln. When Et4NCl was the electrolyte, this dissoln. process coupled with potential cycling expts. enabled conventional soln.-phase data to be obtained in H2O for the analogous 6 1-electron redn. steps previously detected in MeCN. A strong medium effect attributed to Lewis acidity effects was apparent upon comparison with E0' data obtained in H2O and MeCN. But with the [SiW12O40]4- system, E0' values for the [SiW12O40]4-/5-/6-/7- processes in MeCN exhibited a larger (∼70 mV) dependence on isomeric form, and the isomerization step, [γ-SiW12O40]6-→ [α-SiW12O40]6-, was detected on the voltammetric time scale. The influence of isomeric form on reversible potential data is considered in terms of structural and charge d. differences exhibited in the [S2W18O62]4- and [SiW12O40]4- systems studied in this paper and published data available on the α, β, γ, and γ* isomers of [As2W18O62]6- and [P2W18O62]6- Dawson anions and Keggin systems.

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20. 20

    Richardt, P. J. S.; Gable, R. W.; Bond, A. M.; Wedd, A. G. Synthesis and Redox Characterization of the Polyoxo Anion, γ*-[S₂W₁₈O₆₂]^4–: A Unique Fast Oxidation Pathway Determines the Characteristic Reversible Electrochemical Behavior of Polyoxometalate Anions in Acidic Media. Inorg. Chem. 2001, 40, 703– 709,  DOI: 10.1021/ic000793q

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    20

    Synthesis and Redox Characterization of the Polyoxo Anion, γ*-[S2W18O62]4-: A Unique Fast Oxidation Pathway Determines the Characteristic Reversible Electrochemical Behavior of Polyoxometalate Anions in Acidic Media

    Richardt, Peter J. S.; Gable, Robert W.; Bond, Alan M.; Wedd, Anthony G.

    Inorganic Chemistry (2001), 40 (4), 703-709CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)

    The synthesis and characterization of (Bu4N)4[S2W18O62]·1.23MeCN·0.27H2O are reported. It crystallizes in the monoclinic space group C2/c with a 22.389(6), b 22.104(3), c 25.505(5) Å, β 95.690(15)°, and Z = 4. The anion exists as the γ* isomer, the second example of this isomer type to be characterized structurally. The equivalent Mo salt occurs as the α isomer. γ*-[S2W18O62]4- in MeCN soln. displayed four electrochem. reversible 1-electron redox processes at E1/2 values of -0.24, -0.62, -1.18, and -1.57 V vs. the Fc+/Fc couple. Upon addn. of acid in MeCN/H2O (95/5 vol./vol.), the two most cathodic processes converted to an overall two-electron process at -0.71 V. The total data suggested that this process actually comprises two 1-electron transfer processes, occurring at different potentials, with assocd. proton-transfer reactions. The interpretation is supported by simulation of the effect of acid titrn. upon the cyclic voltammetry. While multiple pathways for correlated redn. and protonation are present in both the Mo and W systems, only a single fast oxidn. pathway is available. As the reduced forms of [S2W18O62]4- are much weaker bases than those of [S2Mo18O62]4-, the individual oxidn. pathways are not the same. However, their existence dets. the highly reversible electrochem. behavior that is characteristic of these anions, and that of polyoxometalate systems in general.

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21. 21

    Way, D. M.; Cooper, J. B.; Sadek, M.; Vu, T.; Mahon, P. J.; Bond, A. M.; Brownlee, R. T.; Wedd, A. G. Systematic Electrochemical Synthesis of Reduced Forms of the α-[S₂Mo₁₈O₆₂]^4–Anion1. Inorg. Chem. 1997, 36, 4227– 4233,  DOI: 10.1021/ic970592v

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    21

    Systematic electrochemical synthesis of reduced forms of the α-[S2Mo18O62]4- anion

    Way, David M.; Cooper, John B.; Sadek, Maruse; Vu, Truc; Mahon, Peter J.; Bond, Alan M.; Brownlee, Robert T. C.; Wedd, Anthony G.

    Inorganic Chemistry (1997), 36 (19), 4227-4233CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)

    As proton concn. increases, the 1st two reversible (1 e-)-redn. processes of the anion α-[S2Mo18O62]4- in 95/5 MeCN/H2O convert to an overall (2 e-)-redn. process. Half-wave potentials for reversible 1-electron redn. of [S2Mo18O62]4- itself and its two 1-electron-reduced forms [S2Mo18O62]5- and [HS2Mo18O64]4- were estd. by voltammetry to be 0.12, -0.13, and 0.35 V, resp., vs. the ferrocenium/ferrocene couple. Simulation of cyclic voltammograms provided ests. of assocn. consts. of 1.4, 1.6 × 108, and 102 M-1 for protonation of the resp. products of the redns., [S2Mo18O62]5-, [S2Mo18O62]6-, and [HS2Mo18O62]5-. Equil. consts. for disproportionation of the (1 e-)-reduced species were derived. Rates of the electron transfer and protonation processes are very fast relative to the voltammetric time scale. Consideration of the equil. consts., plus information obtained from acid titrns. monitored by steady state voltammetry, helped define conditions for the isolation of salts of the (1 e-)-, (2 e-)-, (2 e-, 1 H+)-, (2 e-, 2 H+)-, (4 e-, 2 H+)- and (4 e-, 4 H+)-reduced derivs. of the [S2Mo18O62]4- anion. Anions at the (6 e-)- and (8 e-)-reduced levels undergo spontaneous oxidn. in the acid solns. and could not be isolated exptl. Directed synthesis of reduced species in different protonation states is possible for these complex systems if adequate voltammetric data are available.

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22. 22

    Neier, R.; Trojanowski, C.; Mattes, R. Reduced polyoxomolybdates with the Keggin and Dawson structures: preparation and crystal structures of two-electron reduced [K (18-crown^–6)]₂[N(PPh₃)₂]₂ [HPMo₁₂O₄₀]· 8MeCN· 18-crown-6 and four-electron reduced [NBu_n4] ₅[H₃S₂Mo₁₈O₆₂]·4MeCn (18-crown-6= 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane). J. Chem. Soc., Dalton Trans. 1995, 2521– 2528,  DOI: 10.1039/dt9950002521

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    22

    Reduced polyoxomolybdates with the Keggin and Dawson structures: preparation and crystal structures of two-electron reduced [K(18-crown-6)]2[N(PPh3)2]2[HPMo12O40].8MeCN.18-crown-6 and four-electron reduced [NBun4]5[H3S2Mo18O62].4MeCN (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane)

    Neier, Ralf; Trojanowski, Christa; Mattes, Rainer

    Journal of the Chemical Society, Dalton Transactions: Inorganic Chemistry (1995), (15), 2521-8CODEN: JCDTBI; ISSN:0300-9246. (Royal Society of Chemistry)

    By reaction of [K(18-crown-6)][N(PPh3)2]2[PMo12O40]·2MeCN 1 and [NBun4]4[S2Mo18O62] with PPh3 in MeCN [K(18-crown-6)]2[N(PPh3)2]2[HPMo12O40]·8MeCN·18-crown-6 2 (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane) and [NBun4]5[H3S2Mo18O62]·4MeCN 3 were prepd. 2 Contains the two-electron reduced [HPMo12O40]4- ion having the α-Keggin structure, 3 the four-electron reduced [H3S2Mo18O62]5- ion having the α-Dawson structure. 1-3 Were characterized by IR and NMR spectroscopy and x-ray diffraction. The structures of 1 and 2 are disordered in space group P‾1. The heteropolyanions show apparent Th symmetry; their actual symmetry is T. Upon redn. the Mo···Mo distances increase slightly. The strongly alternating 'short' (mean 1.814 Å) and 'long' (1.990 Å) Mo-O-Mo bonds in the unreduced compd. 1 become more equal in 2. The structural changes upon redn. obsd. in 3 were analyzed. The most significant alterations are an increase of the Mo···Mo distances between corner-sharing MoO6 octahedra in the equatorial belt by 0.066 Å, and a decrease of the Mo-O-Mo bond lengths connecting the two halves of the anion. The alternation of the Mo-O(bridge) bonds is nearly evened out after redn. All structural changes obsd. in 2 and 3 are consistent with the description that the addnl. electrons occupy delocalized MOs extending over the Mo-Ob framework.

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23. 23

    Cooper, J. B.; Way, D. M.; Bond, A. M.; Wedd, A. G. A green heteropoly blue: isolation of a stable, odd oxidation level in a Dawson molybdate anion,[S₂Mo₁₈O₆₂]⁵. Inorg. Chem. 1993, 32, 2416– 2420,  DOI: 10.1021/ic00063a035

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    23

    A green heteropoly blue: isolation of a stable, odd oxidation level in a Dawson molybdate anion, [S2Mo18O62]5-

    Cooper, John B.; Way, David M.; Bond, Alan M.; Wedd, Anthony G.

    Inorganic Chemistry (1993), 32 (11), 2416-20CODEN: INOCAJ; ISSN:0020-1669.

    Four consecutive and reversible 1-electron redn. processes are seen in the voltammetry of α-[S2Mo18O62]4- in MeCN. This contrasts with the 4 reversible 2-electron 2-proton redn. processes identified previously in acidified MeCN. The 1- and 2-electron redn. products in MeCN were isolated as the green and blue salts, (Bu4N)5[S2Mo18O62] and (Bu4N)6[S2Mo18O62], resp. The disproportionation const. for [S2Mo18O62]5- was estd. (Kdis = 8.8 × 10-5) and indicates <1% disproportionation in MeCN soln. In the presence of aq. acid, [S2Mo18O62]5- readily disproportionates to give equal concns. of [S2Mo18O62]4- and protonated [S2Mo18O62]6-. The microcryst. EPR spectrum at 253 K (-20°) of (Bu4N)5[S2Mo18O62] displays at least 91 lines due to hyperfine interaction with the 95,97Mo nuclei (I = 5/2; 25.5 at. %). A no. of isotopomers contribute to the obsd. spectrum. These observations, together with the dependence of the EPR linewidth on temp. (Ea, 0.0045 eV), are consistent with intramol. thermal delocalization of the odd green electron over all of the mol. framework at 77-253 K. Above 253 K, the temp. dependence increases by a factor of ∼20 (Ea = 0.087 eV). This observation is consistent with an intermol. hopping process at the higher temps.

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24. 24

    Walsh, J. J.; Zhu, J.; Zeng, Q.; Forster, R. J.; Keyes, T. E. Self assembled composites of luminescent Ru (ii) metallopolymers and the Dawson polyoxometalate α-[Mo ₁₈O₅₄(SO₄)₂] ^4–. Dalton Trans. 2012, 41, 9928– 9937,  DOI: 10.1039/c2dt30503h

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    24

    Self assembled composites of luminescent Ru(II) metallopolymers and the Dawson polyoxometalate α-[Mo18O54(SO4)2]4-

    Walsh, James J.; Zhu, Jie; Zeng, Qiang; Forster, Robert J.; Keyes, Tia E.

    Dalton Transactions (2012), 41 (33), 9928-9937CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)

    The interaction of two luminescent metallopolymers; [Ru(bpy)2(PVP)10]2+ and [Ru(bpy)2(CAIP)co-poly7]+, where bpy is 2,2'-bipyridyl, PVP is polyvinylpyridine, and (CAIP)co-poly7 is poly(styrene6-co-p-(aminomethyl)styrene) amide linked to 2-(4-carboxyphenyl)imidazo[4,5-f] [1,10]phenanthroline, with the Dawson polyoxomolybdate α-[Mo18O54(SO4)2]4- is described. Both metallopolymers undergo electrostatic assocn. with the polyoxometalate. From both electronic and luminescence spectroscopy the thermodn. products were detd. to be {[Ru(bpy)2(PVP)10]4.5[Mo18O54(SO4)2]}5+ and {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+, i.e. in both instances, the no. of ruthenium centers in the cluster exceeds the no. required for charge neutralization of the molybdate center. Assocn. quenches the luminescence of the metallopolymer although, consistent with the excess of Ru(ii) present in the assocd. composites, emission is not completely extinguished even when a large excess of [Mo18O54(SO4)2]4- is present. The obsd. emission lifetime was not affected by [Mo18O54(SO4)2]4- therefore quenching was deemed static. The luminescent intensity data was found to fit best to a (sphere of action) Perrin model from which the radii of the quenching were calcd. as 4.6 Å and 5.8 Å for [Ru(bpy)2(PVP)10]2+ and [Ru(bpy)2(CAIP co-poly)7]+ resp. Both UV/Vis and resonance Raman data indicate the presence of a new optical transition centered around 490 nm for the composite, {[Ru(bpy)2(PVP)10]4.5[Mo18O54(SO4)2]}5+ but not for {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+. This indicates strong electronic interaction between the metal centers in the former composite, which despite good thermodn. analogy, is not obsd. for {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+. These results are consistent with photoelectrochem. studies of layer by layer assemblies of these films which indicate that the ruthenium center sensitizes polyoxometalate photo-oxidn. of benzyl alc. in {[Ru(bpy)2(PVP)10]4.5[Mo18O54(SO4)2]}5+ but not in {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+.

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25. 25

    Fay, N.; Dempsey, E.; McCormac, T. Assembly, electrochemical characterisation and electrocatalytic ability of multilayer films based on [Fe(bpy)₃]²⁺, and the Dawson heteropolyanion,[P₂W₁₈O₆₂]^6–. J. Electroanal. Chem. 2005, 574, 359– 366,  DOI: 10.1016/j.jelechem.2004.07.038

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    25

    Assembly, electrochemical characterisation and electrocatalytic ability of multilayer films based on [Fe(bpy)3]2+, and the Dawson heteropolyanion, [P2W18O62]6-

    Fay, Nigel; Dempsey, Eithne; McCormac, Timothy

    Journal of Electroanalytical Chemistry (2005), 574 (2), 359-366CODEN: JECHES ISSN:. (Elsevier B.V.)

    Successive adsorption onto a glassy C electrode of the Dawson heteropolyanion, [P2W18O62]6-, and the multiply charged cation [Fe(bpy)3]2+, gave stable multilayer assemblies on the electrode surface. Surface coverages are typical of monolayer coverages for multilayer systems. Cyclic voltammetric studies of the assembly in aq. 0.5M NaHSO4, gave a range of redox couples assocd. with the Fe3+/2+ redox system, of the cationic [Fe(bpy)3]2+ moiety and the W-oxo framework of the Dawson parent heteropolyanion, [P2W18O62]6-. It was possible to immobilize up to thirty monolayers, with the system exhibiting well-behaved redox behavior. The stability of the assembly towards redox switching was studied, with it being found to be extremely stable once the outer layer is anionic. The immobilized film was also tested for electrocatalytic activity for the redn. of nitrite, H2O2 and bromate, and is an efficient electrocatalyst.

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26. 26

    Bernardini, G.; Wedd, A. G.; Zhao, C.; Bond, A. M. Photochemical oxidation of water and reduction of polyoxometalate anions at interfaces of water with ionic liquids or diethylether. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 11552– 11557,  DOI: 10.1073/pnas.1203818109

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    26

    Photochemical oxidation of water and reduction of polyoxometalate anions at interfaces of water with ionic liquids or diethylether

    Bernardini, Gianluca; Wedd, Anthony G.; Zhao, Chuan; Bond, Alan M.

    Proceedings of the National Academy of Sciences of the United States of America (2012), 109 (29), 11552-11557, S11552/1-S11552/3CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)

    Photoredn. of [P2W18O62]6-, [S2Mo18O62]4-, and [S2W18O62]4- polyoxometalate anions (POMs) and oxidn. of water occurs when water-ionic liq. and water-diethylether interfaces are irradiated with white light (275-750 nm) or sunlight. The ionic liqs. (ILs) employed were aprotic ([Bmim]X; Bmim = (1-butyl-3-methylimidazolium, X = BF4, PF6)) and protic (DEAS = diethanolamine hydrogen sulfate; DEAP = diethanolamine hydrogen phosphate). Photochem. formation of reduced POMs at both thermodynamically stable and unstable water-IL interfaces led to their initial diffusion into the aq. phase and subsequent extn. into the IL phase. The mass transport was monitored visually by color change and by steady-state voltammetry at microelectrodes placed near the interface and in the bulk soln. phases. However, no diffusion into the org. phase was obsd. when [P2W18O62]6- was photo-reduced at the water-diethylether interface. In all cases, water acted as the electron donor to give the overall process: 4POM + 2H2O + hν → 4POM- + 4H+ + O2. However, more highly reduced POM species are likely to be generated as intermediates. The rate of diffusion of photo-generated POM- was dependent on the initial concn. of oxidized POM and the viscosity of the IL (or.mixed phase system produced in cases in which the interface is thermodynamically unstable). In the water-DEAS system, the evolution of dioxygen was monitored in situ in the aq. phase by using a Clark-type oxygen sensor. Differences in the structures of bulk and interfacial water are implicated in the activation of water. An analogous series of reactions occurred upon irradn. of solid POM salts in the presence of water vapor.

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27. 27

    Cao, G.; Xiong, J.; Xue, Q.; Min, S.; Hu, H.; Xue, G. Organic–inorganic heteropoly blue based on Dawson-type molybdosulfate and organic dye and its characterization and application in electrocatalysis. Electrochim. Acta 2013, 106, 465– 471,  DOI: 10.1016/j.electacta.2013.05.072

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    27

    Organic-inorganic heteropoly blue based on Dawson-type molybdosulfate and organic dye and its characterization and application in electrocatalysis

    Cao, Guolei; Xiong, Jun; Xue, Qi; Min, Suotian; Hu, Huaiming; Xue, Ganglin

    Electrochimica Acta (2013), 106 (), 465-471CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)

    A new org.-inorg. heteropoly blue based on Dawson-type molybdosulfate and org. dye, (MB)5[S2MoV1Mo17VlO62]·MeCN (MB = C16H18N3S), was synthesized under ambient conditions and characterized by IR, fluorescence spectrum, single crystal x-ray diffraction, magnetism measurement and XPS anal. X-ray diffraction anal. shows that the polyoxoanions fill in the interspace formed by the MB cations and MeCN and interacted by Coulombic forces, complex H bonds, such as CH···O, CH···S and CH···N, and CH···π, π···π stacking interactions. The XPS data and magnetic measurements show that the polyanion was mixed valence as a result of one electron redn. The monotonous decrease of χMT from 0.28 cm3 mol-1 at ambient temp. down to 0.13 cm3 mol-1 K at 2 K indicates antiferromagnetic interactions among the mono-electron redn. polyanions, S2MoV1Mo17VlO625-. Studies of the photoluminescent properties in MeCN soln. suggest the formation of ion pairs of [S2Mo18O62]4- anion and MB cation or charge-transfer transitions between the cationic MB donor and the POM acceptor. Also, the org.-inorg. heteropoly blue was used to fabricate a modified C paste electrode (1-CPE), which exhibits five pair redox peaks in the potential range -300 mV to 700 mV and more pos. 1st redox potentials than P2Mo18O626-, higher stability and good electrocatalytic activity toward the redn. of nitrite, chlorate, bromate and H2O2 in acidic (1 M H2SO4) aq. soln.

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28. 28

    Yaqub, M.; Imar, S.; Laffir, F.; Armstrong, G.; McCormac, T. Investigations into the electrochemical, surface, and electrocatalytic properties of the surface-immobilized polyoxometalate, TBA₃K[SiW₁₀O₃₆(PhPO)₂]. ACS Appl. Mater. Interfaces 2015, 7, 1046– 1056,  DOI: 10.1021/am5017864

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    28

    Investigations into the Electrochemical, Surface, and Electrocatalytic Properties of the Surface-Immobilized Polyoxometalate, TBA3K[SiW10O36(PhPO)2]

    Yaqub, Mustansara; Imar, Shahzad; Laffir, Fathima; Armstrong, Gordon; McCormac, Timothy

    ACS Applied Materials & Interfaces (2015), 7 (2), 1046-1056CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)

    Surface anchoring of an org. functionalized POM, TBA3K[SiW10O36(PhPO)2] was carried out by two methods, the layer-by-layer (LBL) assembly technique by employing a pentaerythritol-based Ru(II) metallodendrimer as a cationic moiety and also by entrapping the POM in a conducting polypyrrole film. The redox behavior of the constructed films was studied by using cyclic voltammetry and electrochem. impedance spectroscopy. The surface morphologies of the constructed multilayers were examd. by SEM and at. force microscopy. XPS was conducted to confirm the elements present within the fabricated films. The multilayer assembly was also studied for its catalytic efficiency towards the redn. of nitrite.

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29. 29

    Lv, H.; Geletii, Y. V.; Zhao, C.; Vickers, J. W.; Zhu, G.; Luo, Z.; Song, J.; Lian, T.; Musaev, D. G.; Hill, C. L. Polyoxometalate water oxidation catalysts and the production of green fuel. Chem. Soc. Rev. 2012, 41, 7572– 7589,  DOI: 10.1039/c2cs35292c

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    Polyoxometalate water oxidation catalysts and the production of green fuel

    Lv, Hongjin; Geletii, Yurii V.; Zhao, Chongchao; Vickers, James W.; Zhu, Guibo; Luo, Zhen; Song, Jie; Lian, Tianquan; Musaev, Djamaladdin G.; Hill, Craig L.

    Chemical Society Reviews (2012), 41 (22), 7572-7589CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)

    A review. In the last five years and currently, research on solar fuels has been intense and no sub-area in this field has been more active than the development of water oxidn. catalysts (WOCs). In this time frame, a new class of mol. water oxidn. catalysts based on polyoxometalates have been reported that combine the advantages of homogeneous and heterogeneous catalysts. This review addresses central issues in green energy generation, the challenges in water oxidn. catalyst development, and the possible uses of polyoxometalates in green energy science.

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30. 30

    Ammam, M. Polyoxometalates: formation, structures, principal properties, main deposition methods and application in sensing. J. Mater. Chem. A 2013, 1, 6291– 6312,  DOI: 10.1039/c3ta01663c

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    Polyoxometalates: formation, structures, principal properties, main deposition methods and application in sensing

    Ammam, Malika

    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2013), 1 (21), 6291-6312CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)

    A review. Today, sensing represents one of the key topics in current science and technol. Polyoxometalates (POMs), which are defined as early transition metal clusters, are considered as one of the most growing fields of research and development in sensing. This paper discusses the promising prospects of POMs in sensing. The paper starts with brief definitions about the formation of POMs. The two basic structures of POMs, Keggin and Dawson, as well as some combined structures are discussed. The interesting properties of POMs particularly as acid catalysts, in medicine, in redox chem. and in magnetism are briefly mentioned. The main methods used for the deposition of POMs on solid supports (substrates) including chemisorption, electrodeposition, encapsulation in polymers and sol-gels, immobilization using the Langmuir-Blodgett process, layer by layer assemblies as well as deposition via formation of hybrid POM-org. moieties are discussed with their advantages and disadvantages. Finally, the potential applications of immobilized POMs on solid substrates as sensors for the detection and detn. of analytes both in liq. and in the gas phase are addressed and compared.

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31. 31

    Lu, X.-F.; Liao, P.-Q.; Wang, J.-W.; Wu, J.-X.; Chen, X.-W.; He, C.-T.; Zhang, J.-P.; Li, G.-R.; Chen, X.-M. An alkaline-stable, metal hydroxide mimicking metal–organic framework for efficient electrocatalytic oxygen evolution. J. Am. Chem. Soc 2016, 138, 8336– 8339,  DOI: 10.1021/jacs.6b03125

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    An Alkaline-Stable, Metal Hydroxide Mimicking Metal-Organic Framework for Efficient Electrocatalytic Oxygen Evolution

    Lu, Xue-Feng; Liao, Pei-Qin; Wang, Jia-Wei; Wu, Jun-Xi; Chen, Xun-Wei; He, Chun-Ting; Zhang, Jie-Peng; Li, Gao-Ren; Chen, Xiao-Ming

    Journal of the American Chemical Society (2016), 138 (27), 8336-8339CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)

    Postsynthetic ion exchange of [Co2(μ-Cl)2(btta)] (MAF-X27-Cl, H2bbta = 1H,5H-benzo(1,2-d:4,5-d')bistriazole) possessing open metal sites on its pore surface yields a material [Co2(μ-OH)2(bbta)] (MAF-X27-OH) functionalized by both open metal sites and hydroxide ligands, giving drastically improved electrocatalytic activities for the oxygen evolution reaction (an overpotential of 292 mV at 10.0 mA cm-2 in 1.0 M KOH soln.). Isotope tracing expts. further confirm that the hydroxide ligands are involved in the OER process to provide a low-energy intraframework coupling pathway.

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32. 32

    Papagianni, G. G.; Stergiou, D. V.; Armatas, G. S.; Kanatzidis, M. G.; Prodromidis, M. I. Synthesis, characterization and performance of polyaniline–polyoxometalates (XM12, X= P, Si and M= Mo, W) composites as electrocatalysts of bromates. Sens. Actuators, B 2012, 173, 346– 353,  DOI: 10.1016/j.snb.2012.07.020

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    32

    Synthesis, characterization and performance of polyaniline-polyoxometalates (XM12, X = P, Si and M = Mo, W) composites as electrocatalysts of bromates

    Papagianni, Grammatiki G.; Stergiou, Dimitrios V.; Armatas, Gerasimos S.; Kanatzidis, Mercouri G.; Prodromidis, Mamas I.

    Sensors and Actuators, B: Chemical (2012), 173 (), 346-353CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)

    Composite materials polyaniline (PANI)-polyoxometalates (POM = XM12, X = P, Si and M = Mo, W) were synthesized and characterized by FTIR, UV-visible, SEM, XRD, SAXS anal. and cyclic voltammetry. Suspensions of 2.5 mg mL-1 PANI-PMo12 in 2% (wt./vol.) poly(ethyleneimine) (PEI) in methanol were prepd. and deposited onto graphene oxide-modified graphite electrodes. These were tested as sensors for the ability to electrocatalyze the redn. of bromates by using cyclic voltammetry. Various exptl. variables such as the loading of the composite material, the concn. of PEI, the pH and the compn. of electrolyte, and the electrode material were optimized. By performing d.c. amperometry at a fixed potential of -0.3 V, vs. a Ag/AgCl ref. electrode, in 0.05M HCl, a linear calibration curve over the concn. range 7.5 × 10-6 to 5.0 × 10-4 M BrO3- was constructed. The 3σ limit of detection and the relative std. deviation of the method were 3.0 × 10-6 M BrO3- and 3% (n = 7, 1 × 10-4 M BrO3-), resp. The accuracy of the method was established by recovery studies in spiked drinking water and flour ext. samples. Recovery was 95.4-100.2%. Finally, the sensors exhibited a remarkable working and storage stability when they kept dry in ambient conditions.

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33. 33

    Ernst, A. Z.; Sun, L.; Wiaderek, K.; Kolary, A.; Zoladek, S.; Kulesza, P. J.; Cox, J. A. Synthesis of Polyoxometalate-Protected Gold Nanoparticles by a Ligand-Exchange Method: Application to the Electrocatalytic Reduction of Bromate. Electroanalysis 2007, 19, 2103– 2109,  DOI: 10.1002/elan.200703925

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    Synthesis of polyoxometalate-protected gold nanoparticles by a ligand-exchange method: application to the electrocatalytic reduction of bromate

    Ernst, Andrzej Z.; Sun, Laisheng; Wiaderek, Kamila; Kolary, Aneta; Zoladek, S.; Kulesza, Pawel J.; Cox, James A.

    Electroanalysis (2007), 19 (19-20), 2103-2109CODEN: ELANEU; ISSN:1040-0397. (Wiley-VCH Verlag GmbH & Co. KGaA)

    Gold nanoparticles (AuNPs) protected by an alkanethiol in nonaq. solvent are converted to AuNPs with a surrounding layer of a polyoxometalate, AuNP-POM, by ligand exchange and liq.-liq. extn. into aq. soln. without changing the size of the metal core. With glassy carbon electrodes modified with PMo12-AuNP (PMo12 = H3PMo12O40), the redn. of bromate was mediated by the first redox process of the MoVI centers; the redn. occurred at a lower overpotential and yielded a higher cathodic current than that obsd. with PMo12 alone as the mediator. This synergistic electrocatalysis, which approached a linear diffusion-controlled process, was used to demonstrate the feasibility of the detn. of bromate. A detection limit of 3 μM (k = 3 criterion) was achieved by pulse voltammetry.

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34. 34

    Medetalibeyoğlu, H.; Manap, S.; Yokuş, ÖA.; Beytur, M.; Kardaş, F.; Akyıldırım, O.; Özkan, V.; Yüksek, H.; Yola, M. L.; Atar, N. Fabrication of Pt/Pd nanoparticles/polyoxometalate/ionic liquid nanohybrid for electrocatalytic oxidation of methanol. J. Electrochem. Soc. 2018, 165, F338,  DOI: 10.1149/2.1041805jes

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    Fabrication of Pt/Pd Nanoparticles/Polyoxometalate/Ionic Liquid Nanohybrid for Electrocatalytic Oxidation of Methanol

    Medetalibeyoglu, Hilal; Manap, Sevda; Yokus, Ozlem Aktas; Beytur, Murat; Kardas, Faruk; Akyildirim, Onur; Ozkan, Vildan; Yuksek, Haydar; Yola, Mehmet Lutfi; Atar, Necip

    Journal of the Electrochemical Society (2018), 165 (5), F338-F341CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)

    Fuel cells have important applications in recent decades due to high-energy demands, fossil fuel depletions, and environmental pollution throughout world. Pt/Pd nanoparticles/polyoxometalate/ionic liq. (ILs) nanohybrid synthesized for the 1st time and characterized by transmission electron microscope, scanning electron microscope, x-ray photo electron spectroscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction method. A cost-effective catalyst was developed on Pt/Pd nanoparticles/polyoxometalate/ionic liq. nanohybrid. The developed catalyst based on bimetallic nanoparticle demonstrates effective MeOH oxidn. in comparison with catalysts on monometallic nanoparticle and polyoxometalate/ionic liq. nanohybrid.

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35. 35

    Foster, K.; Bi, L.; McCormac, T. Immobilisation of the polyoxometallate cluster, K₆NaH [Sb₂W₂₀Fe₂O₇₀(H₂O)₆]·29H₂O, in a polypyrrole film. Electrochim. Acta 2008, 54, 868– 875,  DOI: 10.1016/j.electacta.2008.03.058

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    Immobilization of the polyoxometallate cluster, K6NaH[Sb2W20Fe2O70(H2O)6]·29H2O, in a polypyrrole film

    Foster, Kevin; Bi, Lihua; McCormac, Timothy

    Electrochimica Acta (2008), 54 (2), 868-875CODEN: ELCAAV; ISSN:0013-4686. (Elsevier B.V.)

    The conducting polymer, polypyrrole was successfully employed to surface immobilize the Krebs type polyoxometallate, K6NaH[Sb2W20Fe2O70(H2O)6]·29H2O, through cyclic voltammetry. The resulting K6NaH[Sb2W20Fe2O70(H2O)6]·29H2O doped polypyrrole films exhibit the redox activity assocd. with both the Fe(III) and W-O redox centers within the polyoxometallate (POM). The former is situated at potentials within the conducting part of the polymer while the latter redox process was in the insulating domain of the polypyrrole. The Fe(III/II) POM based redox process is pH dependent. Upon redox switching of the polymer through this Fe(III/II) redox system, a process of cation insertion and expulsion into the polypyrrole matrix was obsd. with both the nature and concn. of the supporting electrolyte having a substantial effect upon the potential values at which this process occurred. This cation insertion-expulsion process was studied through the application of the Electrochem. Quartz Crystal Microbalance (EQCM) technique. The result of which indicated that it was both the passage of alkali metal cations and protons from the background electrolyte into the polymer film which maintained electroneutrality within the POM polypyrrole films upon redox switching through the Fe(III/II) redox system. Finally the POM doped polypyrrole films exhibited a clear catalytic property towards the redn. of H2O2 with a sensitivity of 131.8 (±3.5) μA cm-2/mM with a LOD of 16.6 μM at neutral pH.

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36. 36

    Anwar, N.; Vagin, M.; Laffir, F.; Armstrong, G.; Dickinson, C.; McCormac, T. Transition metal ion-substituted polyoxometalates entrapped in polypyrrole as an electrochemical sensor for hydrogen peroxide. Analyst 2012, 137, 624– 630,  DOI: 10.1039/C1AN15665A

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    Transition metal ion-substituted polyoxometalates entrapped in polypyrrole as an electrochemical sensor for hydrogen peroxide

    Anwar, Nargis; Vagin, Mikhail; Laffir, Fathima; Armstrong, Gordon; Dickinson, Calum; McCormac, Timothy

    Analyst (Cambridge, United Kingdom) (2012), 137 (3), 624-630CODEN: ANALAO; ISSN:0003-2654. (Royal Society of Chemistry)

    A conducting polymer was used for the immobilization of various transition metal ion-substituted Dawson-type polyoxometalates (POMs) onto glassy carbon electrodes. Voltammetric responses of films of different thicknesses were stable within the pH domain 2-7 and reveal redox processes assocd. with the conducting polymer, the entrapped POMs and incorporated metal ions. The resulting POM doped polypyrrole films are extremely stable towards redox switching between the various redox states assocd. with the incorporated POM. An amperometric sensor for hydrogen peroxide detection based upon the POM doped polymer films was studied. The detection limits were 0.3 and 0.6 μM, for the Cu2+- and Fe3+-substituted POM-doped polypyrrole films, resp., with a linear region from 0.1 up to 2 mM H2O2. Surface characterization of the polymer films was carried out using at. force microscopy, XPS and SEM.

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37. 37

    Ali, B.; Laffir, F.; Kailas, L.; Armstrong, G.; Kailas, L.; O’Connell, R.; O’Connell, R.; McCormac, T. Electrochemical Characterisation of NiII-Crown-Type Polyoxometalate-Doped Polypyrrole Films for the Catalytic Reduction of Bromate in Water. Eur. J. Inorg. Chem. 2019, 2019, 394– 401,  DOI: 10.1002/ejic.201801106

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    Electrochemical Characterisation of NiII-Crown-Type Polyoxometalate-Doped Polypyrrole Films for the Catalytic Reduction of Bromate in Water

    Ali, Bushra; Laffir, Fathima; Kailas, Lekshmi; Armstrong, Gordon; Kailas, Lekshmi; O'Connell, Robbie; McCormac, Timothy

    European Journal of Inorganic Chemistry (2019), 2019 (3-4), 394-401CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)

    The nickel substituted [Ni4(P8W48O184)(WO2)]28-, crown type polyoxometalate was electrochem. polymerised with conducting polymer pyrrole for the electrocatalytic redn. of bromate in water. The immobilized films of different thickness were characterised by electrochem. and surface based techniques. The resulting films were found to be extremely stable towards redox switching between the various redox states assocd. with the incorporated POM. This system was found to effectively electrocatalyze the redn. of bromate in water without the interference of other common anions. The detection limit was found to be 0.2μM, with a linear region from 0.1 mM up to 2 mM bromate. The resulting POM doped polypyrrole films were found to be highly conductive by AC impedance. Surface characterization of the polymer films was carried out by using XPS, at. force microscopy, and SEM.

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38. 38

    Zimmermann, M. B.; Jooste, P. L.; Pandav, C. S. Iodine-deficiency disorders. The Lancet 2008, 372, 1251– 1262,  DOI: 10.1016/S0140-6736(08)61005-3

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    Iodine-deficiency disorders

    Zimmermann, Michael B.; Jooste, Pieter L.; Pandav, Chandrakant S.

    Lancet (2008), 372 (9645), 1251-1262CODEN: LANCAO; ISSN:0140-6736. (Elsevier Ltd.)

    A review. Summary: 2 billion individuals worldwide have insufficient iodine intake, with those in south Asia and sub-Saharan Africa particularly affected. Iodine deficiency has many adverse effects on growth and development. These effects are due to inadequate prodn. of thyroid hormone and are termed iodine-deficiency disorders. Iodine deficiency is the most common cause of preventable mental impairment worldwide. Assessment methods include urinary iodine concn., goiter, newborn TSH, and blood thyroglobulin. In nearly all countries, the best strategy to control iodine deficiency is iodization of salt, which is one of the most cost-effective ways to contribute to economic and social development. When iodization of salt is not possible, iodine supplements can be given to susceptible groups. Introduction of iodized salt to regions of chronic iodine-deficiency disorders might transiently increase the proportion of thyroid disorders, but overall the small risks of iodine excess are far outweighed by the substantial risks of iodine deficiency. International efforts to control iodine-deficiency disorders are slowing, and reaching the third of the worldwide population that remains deficient poses major challenges.

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39. 39

    Yadav, K.; Pandav, C. S. National iodine deficiency disorders control programme: current status & future strategy. Indian J. Med. Res. 2018, 148, 503,  DOI: 10.4103/ijmr.IJMR_1717_18

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    National Iodine Deficiency Disorders Control Programme: Current status & future strategy

    Yadav Kapil; Pandav Chandrakant S

    The Indian journal of medical research (2018), 148 (5), 503-510 ISSN:0971-5916.

    Iodine deficiency disorders (IDDs) constitute a significant public health problem globally. In India, the entire population is prone to IDDs due to deficiency of iodine in the soil of the sub-continent and thus both animal and plant source food grown on the iodine-deficient soil. IDDs encompass the spectrum of disability and disease and include goitre, cretinism, hypothyroidism, abortion, stillbirth, brain damage, learning disabilities, mental retardation, psychomotor defects, hearing and speech impairment. Iodine deficiency is known to be the single largest cause of preventable brain damage. IDDs with their causal association with brain development, cognition, and learning disabilities impair the human resource development and progress of the country. The children born in iodine-deficient regions on an average have 13.5 intelligence quotient (IQ) points lesser than children born in iodine-sufficient regions. IDD control programme in India is a public health success story, with 92 per cent of the population consuming iodized salt. The partnership between government agencies, academic institutions, salt industry, development agencies and civil society has been key to achieve this success story. The sustainable elimination of iodine deficiency in India is within reach, what is required is accelerated and coordinated effort by all key stakeholder at national and State level.

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    Wang, T.; Zhao, S.; Shen, C.; Tang, J.; Wang, D. Determination of iodate in table salt by transient isotachophoresis–capillary zone electrophoresis. Food Chem. 2009, 112, 215– 220,  DOI: 10.1016/j.foodchem.2008.03.090

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    Niazi, A. K.; Niazi, S. K. Endocrine effects of Fukushima: Radiation-induced endocrinopathy. Indian J. Endocrinol. Metab. 2011, 15, 91,  DOI: 10.4103/2230-8210.81936

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    Endocrine effects of Fukushima: Radiation-induced endocrinopathy

    Niazi Asfandyar Khan; Niazi Shaharyar Khan

    Indian journal of endocrinology and metabolism (2011), 15 (2), 91-5 ISSN:.

    The unfortunate accidents of Chernobyl and Fukushima have led to an enormous amount of radioactive material being released into the atmosphere. Radiation exposure to the human body may be as a result of accidents, such as those in Chernobyl and Fukushima, or due to occupational hazards, such as in the employees of nuclear plants, or due to therapeutic or diagnostic procedures. These different sources of radiations may affect the human body as a whole or may cause localized damage to a certain area of the body, depending upon the extent and dosage of the irradiation. More or less every organ is affected by radiation exposure. Some require a higher dose to be affected while others may be affected at a lower dose. All the endocrine glands are susceptible to damage by radiation exposure; however, pituitary, thyroid and gonads are most likely to be affected. In addition to the endocrine effects, the rates of birth defects and carcinomas may also be increased in the population exposed to excessive radiation.

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42. 42

    Chandra, S.; Lokesh, K. S.; Langa, H. Iodide recognition by the N,N-bis-succinamide-based dendritic molecule [CH₂C(O)NHC(CH₂CH₂C(O)OtBu)₃]₂. Sens. Actuators, B 2009, 137, 350– 356,  DOI: 10.1016/j.snb.2008.12.013

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    Iodide recognition by the N,N-bis-succinamide-based dendritic molecule [CH2C(O)NHC(CH2CH2C(O)OtBu)3]2

    Chandra, Sudeshna; Lokesh, Koodlur Sannegowda; Lang, Heinrich

    Sensors and Actuators, B: Chemical (2009), B137 (1), 350-356CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)

    Ion selective membrane electrode doped with amide functionalized dendritic [CH2C(O)NHC(CH2CH2C(O)OtBu)3]2 macromol. was evaluated as anion sensor. The ability of the membrane has been explored by incorporating it into a plasticized PVC matrix on glassy carbon electrode. The effects of membrane compn., pH and the influence of anion additives, and also the nature of the plasticizers on the response characteristics of the electrode were investigated. The resulting electrode exhibits an anti-Hofmeister selectivity pattern with remarkable specificity towards iodide over other lipophilic inorg. anions. The optimum membrane compn. for best potentiometric performance was achieved with a DPE-plasticized membrane (DPE = di-Ph ether) doped with 15% TBAB (TBAB = tetra-Bu ammonium bromide), suggesting that the ionophore operates via a neutral carrier mechanism. It has a linear response to iodide with a detection limit of 4.46 × 10-7 M and a slope of 59.6 mV/decade, a satisfactory reproducibility and a rapid response time. The selectivity coeffs. for I- towards interferences from ClO4-, NO3- and Cl- were estd. to be KpotI-,anion- = 1.25 × 10-4, 1.99 × 10-4 and 7.94 × 10-5, resp. Application of the electrode to the potentiometric titrn. of iodide ion with silver nitrate is also reported.

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    Fardousi, M. Determination of Iodine Content in Different Brands Table Salt of Bangladesh; East West University, 2012.

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    Sharifi, M.; Dianat, S.; Hosseinian, A. Electrochemical investigation and amperometry determination iodate based on ionic liquid/ polyoxotungstate/P-doped electrochemically reduced graphene oxide multi-component nanocomposite modified glassy carbon electrode. RSC Adv. 2021, 11, 8993– 9007,  DOI: 10.1039/D1RA00845E

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    Electrochemical investigation and amperometry determination iodate based on ionic liquid/polyoxotungstate/P-doped electrochemically reduced graphene oxide multi-component nanocomposite modified glassy carbon electrode

    Sharifi, Minoo; Dianat, Somayeh; Hosseinian, Amin

    RSC Advances (2021), 11 (15), 8993-9007CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)

    A novel modified glassy carbon electrode (GCE) was successfully fabricated with a tetra-component nanocomposite consisting of (1,1'-(1,4-butanediyl)dipyridinium) ionic liq. (bdpy), SiW11O39Ni(H2O) (SiW11Ni) Keggin-type polyoxometalate (POM), and phosphorus-doped electrochem. reduced graphene oxide (P-ERGO) by electrodeposition technique. The (bdpy)SiW11Ni/GO hybrid nanocomposite was synthesized by a one-pot hydrothermal method and characterized by UV-vis absorption, Fourier transform IR (FT-IR) spectroscopy, X-ray diffraction (XRD) anal., thermogravimetric-DTA (TGA/DTA), and transmission electron microscopy (TEM). The morphol., electrochem. performance, and electrocatalysis activity of the nanocomposite modified glassy carbon electrode ((bdpy)SiW11Ni/P-ERGO/GCE) were analyzed by field emission SEM (FE-SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), cyclic voltammetry (CV), square wave voltammetry (SWV), and amperometry, resp. Under the optimum exptl. conditions, the as-prepd. sensor showed high sensitivity of 28.1 μA mM-1 and good selectivity for iodate (IO3-) redn., enabling the detection of IO3- within a linear range of 10-1600 μmol L-1 (R2 = 0.9999) with a limit of detection (LOD) of 0.47 nmol L-1 (S/N = 3). The proposed electrochem. sensor exhibited good reproducibility, and repeatability, high stability, and excellent anti-interference ability, as well as anal. performance in mineral water, tap water, and com. edible iodized salt which might provide a capable platform for the detn. of IO3-.

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45. 45

    Wang, B.; Meng, R-Q.; Xu, L-X.; Wu, L-X.; Bi, L-H. A novel detection of nitrite, iodate and bromate based on a luminescent polyoxometalate. Anal. Methods 2013, 5, 885– 890,  DOI: 10.1039/c2ay26217g

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    45

    A novel detection of nitrite, iodate and bromate based on a luminescent polyoxometalate

    Wang, Bin; Meng, Rui-Qi; Xu, Ling-Xiao; Wu, Li-Xin; Bi, Li-Hua

    Analytical Methods (2013), 5 (4), 885-890CODEN: AMNEGX; ISSN:1759-9679. (Royal Society of Chemistry)

    Described is the detection of NO2-, IO3-, and BrO3- in solns. through combining the electrochem. and the redox reaction accompanying the color change and luminescence switching based on Eu3+-contg. tungstogermanate [(CH3)4N]2.5H7.5[Eu(GeW11O39)(H2O)2]2·4.5H2O (Eu-POM). Eu-POM was electroreduced to form the reduced Eu-POM accompanied by a color change from colorless to blue and luminescence quenching, while the discoloration and luminescence recovery were obsd. after the addn. of NO2-, IO3- and BrO3- because of the spontaneous redox reactions of NO2-, IO3-, and BrO3- with the reduced Eu-POM. Based on this observation, the changes of absorbances and luminescence intensities of the reduced Eu-POM with the concns. of NO2-, IO3-, and BrO3- were investigated and good linear ranges and lower detection limits for the three substances based on S/N = 3 were obtained. This method successfully combines the electrochromic and luminescent properties of polyoxometalate to develop a novel detection of NO2-, IO3-, and BrO3- with good reversibility and high sensitivity as well as a wide linear range. Therefore, such as system shows great potential for the detection of NO2-, IO3-, and BrO3-.

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46. 46

    Zhang, S.; He, P.; Lei, W.; Zhang, G. Novel attapulgite/polyaniline/phosphomolybdic acid-based modified electrode for the electrochemical determination of iodate. J. Electroanal. Chem. 2014, 724, 29– 35,  DOI: 10.1016/j.jelechem.2014.04.011

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    46

    Novel attapulgite/polyaniline/phosphomolybdic acid-based modified electrode for the electrochemical determination of iodate

    Zhang, Susu; He, Ping; Lei, Wen; Zhang, Guangli

    Journal of Electroanalytical Chemistry (2014), 724 (), 29-35CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)

    A novel attapulgite/polyaniline/phosphomolybdic acid-based amperometric sensing platform was constructed for the detn. of iodate. Nanostructured attapulgite was used for reducing agglomeration of polyaniline particles, and the as prepd. attapulgite/polyaniline composite was used to immobilize phosphomolybdic acid. Excellent electrocatalytic performance was obtained due to the synergistic effect of nanostructured attapulgite, polyaniline and phosphomolybdic acid. The electrochem. responses of as prepd. modified electrode were studied by cyclic voltammetry and chronoamperometry. The modified electrode exhibited linear amperometric response for iodate in the concn. range of 2.0 × 10-6 M-5.2 × 10-4 M (R = 0.999). The detection limit was calcd. as 5.3 × 10-7 M. Good reproducibility, high stability, fast amperometric response, and possibility of rapid prepn. were also great advantages of this modified electrode. Based on this work, the attapulgite/polyaniline/phosphomolybdic acid modified electrode was successfully applied to det. iodate in a com. table salt sample.

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47. 47

    McCormac, T.; Farrell, D.; Drennan, D.; Bidan, G. Immobilization of a series of Dawson type heteropolyanions. Electroanalysis 2001, 13, 836– 842,  DOI: 10.1002/1521-4109(200106)13:10<836::AID-ELAN836>3.0.CO;2-F

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    47

    Immobilization of a series of Dawson type heteropolyanions

    McCormac, Timothy; Farrell, David; Drennan, Dennis; Bidan, Gerard

    Electroanalysis (2001), 13 (10), 836-842CODEN: ELANEU; ISSN:1040-0397. (Wiley-VCH Verlag GmbH)

    Attempts to immobilize a series of Dawson type heteropolyanions (HPAs) by anodization and the use of polymeric, polyvinylpyridine (PVP), and conducting pyrrole and N-methylpyrrole, films has been undertaken. A stable film of the Dawson Parent, [P2W18O62]6-, HPA was obtained on an anodized carbon electrode, the film exhibited thin layer behavior and was stable up to a pH value of 2.00. The same HPA was successfully immobilized in a protonated PVP film with the resultant modified electrode being stable between pH values of 1.00 and 8.00, with the redox activity of the immobilized HPA exhibiting the same pH dependence as shown by the soln. phase species. It was shown that a stable polypyrrole film doped with the Dawson parent HPA was obtained when the cycling of the film was restricted to the first two tungsten-oxo based redox processes in buffer solns. more alk. than 2.00. The CuII Dawson HPA was successfully immobilized in a polypyrrole matrix exhibiting good stability and clear redox activity for the CuII HPA. Poly(N-methylpyrrole) was found to be the most suitable conducting polymer film for the immobilization of the FeIII Dawson HPA. The film was found to be extremely stable to electrochem. cycling in a buffer soln. of pH 4.50. The redox activity of the immobilized HPA was clearly obsd. and well behaved. In addn. to this the electrocatalytic properties of the FeIII HPA towards the redn. of nitrite, as obsd. in soln., was preserved in the immobilized state.

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48. 48

    Baffert, C.; Boas, J. F.; Bond, A. M.; Kögerler, P.; Long, D. L.; Pilbrow, J. R.; Cronin, L. Experimental and Theoretical Investigations of the Sulfite-Based Polyoxometalate Cluster Redox Series: α-and β-[Mo₁₈O₅₄(SO₃)₂]^{4–/5–/6–}. Chem. Eur. J 2006, 12, 8472– 8483,  DOI: 10.1002/chem.200501450

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    48

    Experimental and theoretical investigations of the sulfite-based polyoxometalate cluster redox series: α- and β-[Mo18O54(SO3)2]4-/5-/6-

    Baffert, Carole; Boas, John F.; Bond, Alan M.; Koegerler, Paul; Long, De-Liang; Pilbrow, John R.; Cronin, Leroy

    Chemistry - A European Journal (2006), 12 (33), 8472-8483CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)

    The synthesis, isolation and structural characterization of the sulfite polyoxomolybdate clusters α-(D3h)-(C20H44N)4{α-[Mo18O54(SO3)2]}.MeCN and β-(D3d)(C20H44N)4{β-[Mo18O54(SO3)2]}·MeCN is presented. Voltammetric studies in MeCN (0.1M Hx4NClO4, Hx4N = tetra-n-hexylammonium) reveal an extensive series of six 1-electron redn. processes for both isomers. Under conditions of bulk electrolysis, the initial [Mo18O54(SO3)2]4-/5- and [Mo18O54-(SO3)2]5-/6- processes produce stable [MO18O54(SO3)2]5- and [Mo18O54- (SO3)2]6- species, resp., and the same reduced species may be produced by photochem. redn. Spectroelectrochem. data imply that retention of structural form results upon redn., so that both α and β isomers are available at each of the 4-, 5-, and 6-redox levels. However, the α isomer is the thermodynamically favored species in both the 1- and two-electron-reduced states, with β → α isomerization being detected in both cases on long time scales (days). EPR spectra also imply that increasing localization of the unpaired electron occurs over the α- and β-[Mo18O54(SO3)2]5- frameworks as the temp. approaches 2 K where the EPR spectra show orthorhombic symmetry with different g and hyperfine values for the α and β isomers. Theor. studies support the observation that it is easier to reduce the α cluster than the β form and also provide insight into the driving force for β → α isomerization in the reduced state. Data are compared with that obtained for the well studied α-[Mo18O54-(SO4)2]4- sulfate cluster.

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49. 49

    Fay, N.; Bond, A. M.; Baffert, C.; Boas, J. F.; Pilbrow, J. R.; Long, D.-L.; Cronin, L. Structural, electrochemical, and spectroscopic characterization of a redox pair of sulfite-based polyoxotungstates: α-[W₁₈O₅₄(SO₃)₂]^4–and α-[W₁₈O₅₄(SO3) 2] 5. Inorg. chem. 2007, 46, 3502– 3510,  DOI: 10.1021/ic062067e

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    49

    Structural, Electrochemical, and Spectroscopic Characterization of a Redox Pair of Sulfite-Based Polyoxotungstates: α-[W18O54(SO3)2]4- and α-[W18O54(SO3)2]5-

    Fay, Nigel; Bond, Alan M.; Baffert, Carole; Boas, John F.; Pilbrow, John R.; Long, De-Liang; Cronin, Leroy

    Inorganic Chemistry (2007), 46 (9), 3502-3510CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)

    The synthesis, isolation, and structural characterization of the fully oxidized sulfite-based polyoxotungstate cluster (Pr4N)4{α-[W18O54(SO3)2]}·2MeCN and the 1-electron reduced form (Pr4N)5{α-[W18O54(SO3)2]}·2MeCN was achieved. α-[W18O54(SO3)2]5- was obtained as a Pr4N+ salt by reducing the Trojan Horse [W18O56(SO3)2(H2O)2]8- cluster via a template orientation transformation. MeCN solns. of pure α-[W18O54(SO3)2]5- also were prepd. electrochem. by 1-electron bulk reductive electrolysis of α-[W18O54(SO3)2]4-. Cyclic voltammetry of α-[W18O54(SO3)2]4- and α-[W18O54(SO3)2]5- in MeCN (0.1M Hx4NClO4) produces evidence for an extensive series of reversible 1-electron redox processes, that are assocd. with the W-oxo framework of the polyoxometalate cluster. Hydrodynamic voltammograms in MeCN exhibit the expected sign and magnitude of the steady-state limiting current values for the α-[W18O54(SO3)2]4-/5-/6- series and confirm the existence of a stable 1-electron reduced species, α-[W18O54(SO3)2]5-. Employment of the Randles-Sevcik (cyclic voltammetry) and Levich (rotating disk electrode) equations at a glassy C electrode (d = 3 mm) enable diffusion coeff. values of 3.7 and 3.8 × 10-6 cm2 s-1 to be obtained for α-[W18O54(SO3)2]4- and α-[W18O54(SO3)2]5-, resp. The W polyoxometalates are highly photoactive, since measurable photocurrents and color changes are detected for both species upon irradn. with white light. EPR spectra obtained from both MeCN soln. and solid samples, down to temps. ≥2.3 K, of the chem. and electrochem. prepd. 1-electron reduced species provided evidence that the unpaired electron in α-[W18O54(SO3)2]5- is delocalized over a no. of atoms in the polyoxometalate structure, even at very low temps.

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50. 50

    Mei, B.-A.; Munteshari, O.; Lau, J.; Dunn, B.; Pilon, L. Physical interpretations of Nyquist plots for EDLC electrodes and devices. J. Phys. Chem. C 2018, 122, 194– 206,  DOI: 10.1021/acs.jpcc.7b10582

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    50

    Physical Interpretations of Nyquist Plots for EDLC Electrodes and Devices

    Mei, Bing-Ang; Munteshari, Obaidallah; Lau, Jonathan; Dunn, Bruce; Pilon, Laurent

    Journal of Physical Chemistry C (2018), 122 (1), 194-206CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)

    Electrochem. impedance spectroscopy (EIS) consists of plotting Nyquist plots representing the imaginary vs. the real parts of the complex impedance of individual electrodes or electrochem. cells. To date, interpretations of Nyquist plots were based on phys. intuition and/or on the use of equiv. RC circuits. However, phys. interpretations of Nyquist plots and equiv. RC circuits are not unique and have often been inconsistent in the literature. This study aims to provide unequivocal phys. interpretations of electrochem. impedance spectroscopy (EIS) results for elec. double layer capacitor (EDLC) electrodes and devices. To do so, a physicochem. transport model was used for numerically reproducing Nyquist plots accounting for (i) elec. double layer (EDL) formation at the electrode/electrolyte interface, (ii) charge transport in the electrode, and (iii) ion electrodiffusion in binary and sym. electrolytes. The Nyquist plots of EDLC electrodes were numerically generated for different electrode cond. and thickness, electrolyte domain thickness, as well as ion diam., diffusion coeff., and concns. The electrode resistance, electrolyte resistance, and the equil. differential capacitance were identified from Nyquist plots without relying on equiv. RC circuits. The internal resistance retrieved from the numerically generated Nyquist plots was comparable to that retrieved from the IR drop in numerically simulated galvanostatic cycling. Also, EIS simulations were performed for EDLC devices and similar interpretations of Nyquist plots were obtained. Finally, these results and interpretations were confirmed exptl. using EDLC devices consisting of two identical activated-C electrodes in both aq. and nonaq. electrolytes.

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51. 51

    Ueda, T.; Ohnishi, M.; Kawamoto, T.; Guo, Si-X.; Boasc, J. F.; Bond, A. M. Voltammetric behavior of 1- and 4-[S₂VVW₁₇O₆₂]^5– in acidified acetonitrile. Dalton Trans. 2015, 44, 11660– 11668,  DOI: 10.1039/C5DT01530H

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    51

    Voltammetric behavior of 1- and 4-[S2VVW17O62]5- in acidified acetonitrile

    Ueda, Tadaharu; Ohnishi, Miho; Kawamoto, Daisuke; Guo, Si-Xuan; Boas, John F.; Bond, Alan M.

    Dalton Transactions (2015), 44 (25), 11660-11668CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)

    Data derived from a voltammetric and spectroscopic study of the VV/IV couple assocd. with the initial redn. of the Wells-Dawson-type mono vanadium-substituted polyoxometalates, 1- and 4-[S2VVW17O62]5- in MeCN as a function of CF3SO3H acid concn. were obtained. 51V NMR (VV component) and EPR (VIV component) spectra were measured in MeCN in the presence and absence of an acid. These data showed a small fraction of the 1-isomer in the 4-[S2VVW17O62]5- sample and that protonation could occur at both redox levels for both isomers. From the mechanism postulated from the voltammetric and spectroscopic data, simulations of cyclic voltammograms were undertaken for the redn. of the isomerically pure 1-[S2VVW17O62]5- isomer over a wide acid concn. range, and the results were compared with exptl. data. Cyclic voltammograms of the VV/IV couple derived from the redn. of 1- and 4-[X2VVW17O62]7- (X = P, As) were also obtained in MeCN and the results were compared with those for 1- and 4-[S2VVW17O62]5-. Reversible potentials for the VV/IV couple are dependent on the anion charge of the polyoxometalate. Anal. of cyclic voltammograms obtained for 1- and 4-[S2VVW17O62]5- in MeCN, acetone, DMSO, DMF and nitromethane showed that these VV/IV reversible potentials are also dependent on the acceptor nos. and the polarity index (ENT) values of the org. solvents.

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52. 52

    Barthwal, S.; Singha, B.; Singh, N. B. A novel electrochemical sensor fabricated by embedding ZnO nano particles on MWCNT for morphine detection. Mater. Today 2018, 5, 9061– 9066,  DOI: 10.1016/j.matpr.2017.10.021

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    A novel electrochemical sensor fabricated by embedding ZnO nano particles on MWCNT for morphine detection

    Barthwal, Subodh; Singh, Bhim; Singh, Nakshatra B.

    Materials Today: Proceedings (2018), 5 (3_Part_1), 9061-9066CODEN: MTPAC4; ISSN:2214-7853. (Elsevier Ltd.)

    A review. Sol-gel method was used to synthesize ZnO-MWCNT ionic liq. carbon paste electrode (ZnO/MWCNTs/IL/CPE) taking 1-methyl-3-butylimidazolium bromide as appropriate binder in carbon paste matrix for detection of morphine. X-ray diffraction (XRD), Transmission electron microscopic (TEM), Scanning electron microscopic (SEM) and Energy-Dispersive X-ray spectroscopic (EDS) techniques were used to characterize the nanocomposite. The results obtained by electrochem. oxidn. of morphine on ZnO/MWCNTs/IL/CPE shows the detection of morphine in the linear range of 0.1 to 700μmol L-1 and in the detection limit of 0.06μmol L-1 (3σ). The simple fabrication method, high sensitivity, stability and low cost of the modified electrode were the main features of the prepd. electrochem. sensor.

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53. 53

    Abraham, P.; Renjini, S.; Vijayan, P.; Nisha, V.; Sreevalsan, K.; Anithakumary, V. Review on the Progress in Electrochemical Detection of Morphine Based on Different Modified Electrodes. J. Electrochem. Soc. 2020, 167, 037559  DOI: 10.1149/1945-7111/ab6cf6

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    Review-review on the progress in electrochemical detection of morphine based on different modified electrodes

    Abraham, Pinky; Renjini, S.; Vijayan, Poornima; Nisha, V.; Sreevalsan, Krishna; Anithakumary, V.

    Journal of the Electrochemical Society (2020), 167 (3), 037559CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)

    A review. Morphine is a powerful opioid pain medication and commonly used narcotic pain killer and is toxic during overdose or when abused. Compared to conventional anal. techniques, the electroanal. method has significant advantages viz. low cost, simplicity, ease of operation and facile miniaturization. In the present paper different approaches based on various modifications adopted for effective electrochem. sensing of morphine are reviewed in a comprehensive way. Among different modified electrodes available for the detection of morphine, C based materials-CNTs and graphene-display effective quantification and are attractive in terms of cost compared to noble metals. The performance of reported sensors in terms of their including detection range (LDR), limit of detection (LOD) and technique used are presented. The present review compares various electroanal. techniques adopted for the detn. of morphine.

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54. 54

    Cho, E.; Perebikovsky, A.; Benice, O.; Holmberg, S.; Madou, M.; Ghazinejad, M. Rapid iodine sensing on mechanically treated carbon nanofibers. Sensors 2018, 18, 1486,  DOI: 10.3390/s18051486

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    54

    Rapid iodine sensing on mechanically treated carbon nanofibers

    Cho, Eunbyul; Perebikovsky, Alexandra; Benice, Olivia; Holmberg, Sunshine; Madou, Marc; Ghazinejad, Maziar

    Sensors (2018), 18 (5), 1486/1-1486/9CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)

    In this work, we report on a rapid, efficient electrochem. iodine sensor based on mech. treated carbon nanofiber (MCNF) electrodes. The electrode's highly graphitic content, unique microstructure, and the presence of nitrogen heteroatoms in its at. lattice contribute to increased heterogeneous electron transfer and improved kinetics compared to conventional pyrolytic carbons. The electrode demonstrates selectivity for iodide ions in the presence of both interfering agents and high salt concns. The sensor exhibits clin. relevant limits of detection of 0.59 M and 1.41 M, in 1X PBS and synthetic urine, resp., and a wide dynamic range between 5 M and 700 M. These results illustrate the advantages of the material's unique electrochem. properties for iodide sensing, in addn. to its simple, inexpensive fabrication. The reported iodine sensor eliminates the need for specimen processing, revealing its aptitude for applications in point-of-care diagnostics.

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55. 55

    Ibupoto, Z. H.; Khun, K.; Willander, M. A selective iodide ion sensor electrode based on functionalized ZnO nanotubes. Sensors 2013, 13, 1984– 1997,  DOI: 10.3390/s130201984

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    A selective iodide ion sensor electrode based on functionalized ZnO nanotubes

    Ibupoto, Zafar Hussain; Khun, Kimleang; Willander, Magnus

    Sensors (2013), 13 (), 1984-1997CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)

    ZnO nanotubes were fabricated on a gold-coated glass substrate through chem. etching by the aq. chem. growth method. For the first time a nanostructure-based iodide ion-selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the emf. (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concns. (1 × 10-6 to 1 × 10-1 M) and excellent sensitivity of -62 ±1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10-7 M. The effects of pH, temp., additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of <5 s and high selectivity against common org. and the inorg. anions. The iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of I- in environmental water samples, pharmaceutical products, and other real samples.

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56. 56

    Nosuhi, M.; Nezamzadeh-Ejhieh, A. An indirect application aspect of zeolite modified electrodes for voltammetric determination of iodate. J. Electroanal. Chem. 2018, 810, 119– 128,  DOI: 10.1016/j.jelechem.2017.12.075

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    An indirect application aspect of zeolite modified electrodes for voltammetric determination of iodate

    Nosuhi, Motahare; Nezamzadeh-Ejhieh, Alireza

    Journal of Electroanalytical Chemistry (2018), 810 (), 119-128CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)

    Clinoptilolite nanoparticles (NClin) were Fe(II)-exchanged and used for the modification of C paste electrode (Fe(II)-NClin-CPE) in indirect detn. of iodate. The voltammetric peak current of Fe(II)/Fe(III) redox system was decreased in the presence of iodate in soln. Sufficient characterization was applied for the raw and modified zeolite and CPE. The electrochem. impedance spectroscopy (EIS) confirmed that Fe(II)-NClin/CPE had the best charge transfer ability with respect to the raw CPE and NClin/CPE. The simultaneous effects of the most important influencing variables of square wave voltammetry (modifier%, soln. pH, step potential and amplitude) were studied by designing the expts. by using response surface methodol. (RSM). The optimal run obtained at pH 2.18, amplitude = 0.472 V, modifier% = 17.5 and step potential = 0.0202 V. Under the optimum conditions, the current response of Fe(II)-NClin/CPE was inversely proportional to IO-3 concn. at 4-100 μmol L-1 with a detection limit of 0.64 μmol L-1. Capability of the modified electrode for the detn. of iodate in iodofolic pharmaceutical tablet was studied and the obtained results were statistically compared with the results obtained by iodometric titrn. as a std. method.

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57. 57

    Manivel, A.; Sivakumar, R.; Anandan, S.; Ashokkumar, M. Ultrasound-Assisted Synthesis of Hybrid Phosphomolybdate–Polybenzidine Containing Silver Nanoparticles for Electrocatalytic Detection of Chlorate, Bromate and Iodate Ions in Aqueous Solutions. Electrocatalysis 2012, 3, 22– 29,  DOI: 10.1007/s12678-011-0072-z

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    Ultrasound-assisted synthesis of hybrid phosphomolybdate-polybenzidine containing silver nanoparticles for electrocatalytic detection of chlorate, bromate, and iodate ions in aqueous solutions

    Manivel, Arumugam; Sivakumar, Radhakrishnan; Anandan, Sambandam; Ashokkumar, Muthupandian

    Electrocatalysis (2012), 3 (1), 22-29CODEN: ELECCF; ISSN:1868-2529. (Springer)

    Reported is a hybrid electroactive material composed of Ag nanoparticle-embedded polybenzidine matrix contg. phosphomolybdic acid as the active inorg. component by an ultrasound-assisted method for the electrochem. detection of ClO3-, BrO3- and IO3- in aq. solns. The prepd. hybrid material was characterized for its physicochem. properties: x-ray diffraction and TEM analyses provided evidence for the presence of Ag nanoparticles (≈12 nm) in the hybrid material. The hybrid material was successfully fabricated on a glassy carbon electrode, and cyclic voltammetry was used to probe its electrochem. properties in 1 M H2SO4 soln. Amperometry was employed to find out the detection limits of ClO3-, BrO3-, and IO3- in aq. solns. This hybrid electrochem. interface showed the lowest detection limits of 86.3 nM, 1.45 μM and 1.66 μM for BrO3-, IO3- and ClO3-, resp. Phosphomolybdate anion (PMo12) present in the hybrid material acted as both effective mediator and the source of mobile protons at the electrochem. interface. Ag nanoparticles present in the hybrid material further influenced the electroactivity of the modified electrode.

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58. 58

    Adekunle, A. S.; Arotiba, O. A.; Mamba, B. B. Electrochemical studies and sensing of iodate, periodate and sulphite ions at carbon nanotubes/Prussian blue films modified platinum electrode. Int. J. Electrochem. Sci. 2012, 7, 8503– 8521

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    58

    Electrochemical studies and sensing of iodate, periodate and sulphite ions at carbon nanotubes/Prussian blue films modified platinum electrode

    Adekunle, Abolanle S.; Arotiba, Omotayo A.; Mamba, Bhekie B.

    International Journal of Electrochemical Science (2012), 7 (9), 8503-8521CODEN: IJESIV; ISSN:1452-3981. (Electrochemical Science Group)

    This work describes the modification of Pt electrode with and without functionalized multi-walled C nanotubes (MWCNT-SO32-) and prussian blue nanoparticles (PB) for the detection of iodate, periodate and sulfite ions. The modified electrodes were characterized using techniques such as TEM, electron dispersive x-ray spectroscopy (EDX), cyclic voltammetry (CVs) and electrochem. impedance spectroscopy (EIS). The Pt-MWCNT-PB electrode exhibited enhanced electron transport and catalytic efficiency towards the electrocatalysis of iodate (IO3-), periodate (IO4-) and sulfite (SO32-) compared to the other electrodes studied. The electrode was characterized by some level of adsorption due to adsorbed intermediates. The degree of adsorption was quantified as indicated by the Tafel values of 211.0, 176.2, and 129.2 mVdec-1 for iodate, periodate and sulfite, resp. The analytes were detected at micromolar level. The limit of detection and the catalytic rate const. were 8.30 μM (1.37 × 106 cm3mol-1s-1), 8.06 μM (0.34 × 106 cm3mol-1s-1) and 4.70 μM (5.24 × 107 cm3mol-1s-1) for iodate, periodate and sulfite. The electrode detects iodate in the presence of the interfering effect from other oxo-anions. This electrode can be reliably used to assay iodate in real or com. salt compn.

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59. 59

    Haghighi, B.; Hamidi, H.; Gorton, L. Formation of a robust and stable film comprising ionic liquid and polyoxometalate on glassy carbon electrode modified with multiwalled carbon nanotubes: Toward sensitive and fast detection of hydrogen peroxide and iodate. Electroch. Acta 2010, 55, 4750– 4757,  DOI: 10.1016/j.electacta.2010.03.041

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60. 60

    Zou, B.-X.; Liu, X.-X.; Diamond, D.; Lau, K.-T. Electrochemical synthesis of WO₃/PANI composite for electrocatalytic reduction of iodate. Electrochim. Acta 2010, 55, 3915– 3920,  DOI: 10.1016/j.electacta.2010.02.034

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    60

    Electrochemical synthesis of WO3/PANI composite for electrocatalytic reduction of iodate

    Zou, Ben-Xue; Liu, Xiao-Xia; Diamond, Dermot; Lau, King-Tong

    Electrochimica Acta (2010), 55 (12), 3915-3920CODEN: ELCAAV; ISSN:0013-4686. (Elsevier B.V.)

    Composite film of polyaniline (PANI) and WO3 was electrodeposited by cyclic voltammetric technique from a soln. of aniline and tungstic acid. The obtained WO3/PANI film displayed a significant enhancement of electrocatalytic activity for iodate redn. and a better stability than that of pure WO3 and PANI films. Result of amperometric expt. revealed a good linear relation with concn. of IO3- from 20 to 500 μM, with a high sensitivity of 0.54 μA/μM and a detection limit of 2.7 μM for the detn. of iodate. This composite film was also successfully applied in detn. of iodate in com. table salt.

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