Complexes cationiques POCOP de nickel : synthèse, caractérisation, réactivité et étude catalytique

Ce mémoire traite de la chimie des complexes pinceurs de nickel (II) cationiques ayant un ligand de type POCOP. Elle se divise en deux parties. La première traite de la synthèse, de la caractérisation et de la réactivité des complexes cationiques pinceurs de Ni(II) de type POCOP (POCOP = 1,3-bis(phosphinitobenzene), où C fait partie d’un cycle benzénique et est lié au métal, et P est un ligand phosphoré aussi lié au métal). Ces complexes ont un ligand acétonitrile coordonné au centre métallique et sont du type [(R-POCOPR’)Ni(NCMe)][OSO2CF3], où R est un substituant du cycle benzénique et R’ est un substituant sur le ligand phosphoré (R’ = iPr: R = H (1), p-Me(2), p-OMe(3), p-CO2Me(4), p-Br(5), m,m-tBu2(6), m-OMe(7), m-CO2Me(8); R’ = t-Bu : R = H (9), p-CO2Me(10)). Les complexes cationiques sont préparés en faisant réagir le dérivé Ni(II) neutre correspondant R-(POCOPR’)Ni-Br avec Ag(OSO2CF3¬) dans l’acétonitrile à température ambiante. L’impact des groupements R et R’ du ligand POCOP sur la structure et sur les propriétées électroniques du complexe a été étudié par spectroscopies RMN, UV-VIS et IR, analyse électrochimique, et diffraction des rayons X. Les valeurs de fréquence du lien C≡N (ν(C≡N)) augmentent avec le caractère électroattracteur du complexe, dans l’ordre 7 < 3 ~ 2 ~ 6 < 1 < 5 ~ 8 < 4 et 9 < 10. Ces résultats sont en accord avec le fait qu’une augmentation du caractère électrophile du centre métallique devrait résulter en une augmentation de la donation σ MeCN→Ni. De plus, les complexes cationiques montrent tous un potentiel d’oxydation Ni(II)/Ni(III) plus élevé que leurs analogues neutres Ni-Br. Ensuite, une étude d’équilibre entre un complexe neutre (R-POCOPR’)NiBr et un complexe cationique [(R-POCOPR’)Ni(NCMe)][OSO2CF3] démontre l’échange facile des ligands MeCN et Br. La deuxième partie de ce mémoire consiste en deux chapitres. Le premier (Chapitre 3) est une étude structurelle permettant une meilleure compréhension du mécanisme d’hydroamination des oléfines activées promue par les complexes présentés au chapitre 1, suivi de tentatives de synthèse de nouveaux composés POCOP cationiques comportant un ligand amine et nitrile, et de déplacement du groupement amine par un groupement nitrile. Le deuxième chapitre (4) décrit la réactivité et la cinétique de la réaction d’hydroamination et d’hydroalkoxylation d’oléfines activées, qui permet ainsi de mieux comprendre l’impact des différentes variables du système (groupements R et R’, température, substrats, solvent, etc.) sur la réactivité catalytique.

Voltammetric Investigation of Xanthate Chemisorption on a Chalcopyrite Surface

Cyclic Voltammetry experiments have been conducted on copper, iron, and chalcopyrite (CuFeS2) and compared to mass-balanced EH-pH Diagrams. Potassium ethyl xanthate (KEX) was added to solution and additional voltammetry experiments were performed to determine the surface chemistry reactions of flotation collector in solution with these minerals. The ultimate goal of this research was to investigate the possibility of xanthate chemisorption onto the chalcopyrite mineral surface. Results of the copper mineral testing confirm previous literature studies and corroborate published isotherm data. Results of the iron mineral testing showed changes in surface reactions with the addition of potassium ethyl xanthate to solution, however, these results were not attributed to the chemisorption of xanthate. Results of the chalcopyrite mineral testing indicate that the surface of the mineral oxidizes to chalcocite (Cu2S). In the presence of ethyl xanthate, small currents were observed and attributed to chemisorption of the potassium ethyl xanthate at the chalcocite surface, suggesting that the mineral's hydrophobicity is induced by more than dixanthogen. This phenomenon was found to be pH-dependent under a range of alkaline conditions (i.e., pH 7-12) at narrow potentials (i.e., 0 to -200mV).

Electrochemical Immunosensing of Cortisol in an Automated Microfluidic System Towards Point-of-Care Applications

This dissertation describes the development of a label-free, electrochemical immunosensing platform integrated into a low-cost microfluidic system for the sensitive, selective and accurate detection of cortisol, a steroid hormone co-related with many physiological disorders. Abnormal levels of cortisol is indicative of conditions such as Cushing’s syndrome, Addison’s disease, adrenal insufficiencies and more recently post-traumatic stress disorder (PTSD). Electrochemical detection of immuno-complex formation is utilized for the sensitive detection of Cortisol using Anti-Cortisol antibodies immobilized on sensing electrodes. Electrochemical detection techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been utilized for the characterization and sensing of the label-free detection of Cortisol. The utilization of nanomaterial’s as the immobilizing matrix for Anti-cortisol antibodies that leads to improved sensor response has been explored. A hybrid nano-composite of Polyanaline-Ag/AgO film has been fabricated onto Au substrate using electrophoretic deposition for the preparation of electrochemical immunosening of cortisol. Using a conventional 3-electrode electrochemical cell, a linear sensing range of 1pM to 1µM at a sensitivity of 66µA/M and detection limit of 0.64pg/mL has been demonstrated for detection of cortisol. Alternately, a self-assembled monolayer (SAM) of dithiobis(succinimidylpropionte) (DTSP) has been fabricated for the modification of sensing electrode to immobilize with Anti-Cortisol antibodies. To increase the sensitivity at lower detection limit and to develop a point-of-care sensing platform, the DTSP-SAM has been fabricated on micromachined interdigitated microelectrodes (µIDE). Detection of cortisol is demonstrated at a sensitivity of 20.7µA/M and detection limit of 10pg/mL for a linear sensing range of 10pM to 200nM using the µIDE’s. A simple, low-cost microfluidic system is designed using low-temperature co-fired ceramics (LTCC) technology for the integration of the electrochemical cortisol immunosensor and automation of the immunoassay. For the first time, the non-specific adsorption of analyte on LTCC has been characterized for microfluidic applications. The design, fabrication technique and fluidic characterization of the immunoassay are presented. The DTSP-SAM based electrochemical immunosensor on µIDE is integrated into the LTCC microfluidic system and cortisol detection is achieved in the microfluidic system in a fully automated assay. The fully automated microfluidic immunosensor hold great promise for accurate, sensitive detection of cortisol in point-of-care applications.

Complexes cationiques POCOP de nickel : synthèse, caractérisation, réactivité et étude catalytique

Ce mémoire traite de la chimie des complexes pinceurs de nickel (II) cationiques ayant un ligand de type POCOP. Elle se divise en deux parties. La première traite de la synthèse, de la caractérisation et de la réactivité des complexes cationiques pinceurs de Ni(II) de type POCOP (POCOP = 1,3-bis(phosphinitobenzene), où C fait partie d’un cycle benzénique et est lié au métal, et P est un ligand phosphoré aussi lié au métal). Ces complexes ont un ligand acétonitrile coordonné au centre métallique et sont du type [(R-POCOPR’)Ni(NCMe)][OSO2CF3], où R est un substituant du cycle benzénique et R’ est un substituant sur le ligand phosphoré (R’ = iPr: R = H (1), p-Me(2), p-OMe(3), p-CO2Me(4), p-Br(5), m,m-tBu2(6), m-OMe(7), m-CO2Me(8); R’ = t-Bu : R = H (9), p-CO2Me(10)). Les complexes cationiques sont préparés en faisant réagir le dérivé Ni(II) neutre correspondant R-(POCOPR’)Ni-Br avec Ag(OSO2CF3¬) dans l’acétonitrile à température ambiante. L’impact des groupements R et R’ du ligand POCOP sur la structure et sur les propriétées électroniques du complexe a été étudié par spectroscopies RMN, UV-VIS et IR, analyse électrochimique, et diffraction des rayons X. Les valeurs de fréquence du lien C≡N (ν(C≡N)) augmentent avec le caractère électroattracteur du complexe, dans l’ordre 7 < 3 ~ 2 ~ 6 < 1 < 5 ~ 8 < 4 et 9 < 10. Ces résultats sont en accord avec le fait qu’une augmentation du caractère électrophile du centre métallique devrait résulter en une augmentation de la donation σ MeCN→Ni. De plus, les complexes cationiques montrent tous un potentiel d’oxydation Ni(II)/Ni(III) plus élevé que leurs analogues neutres Ni-Br. Ensuite, une étude d’équilibre entre un complexe neutre (R-POCOPR’)NiBr et un complexe cationique [(R-POCOPR’)Ni(NCMe)][OSO2CF3] démontre l’échange facile des ligands MeCN et Br. La deuxième partie de ce mémoire consiste en deux chapitres. Le premier (Chapitre 3) est une étude structurelle permettant une meilleure compréhension du mécanisme d’hydroamination des oléfines activées promue par les complexes présentés au chapitre 1, suivi de tentatives de synthèse de nouveaux composés POCOP cationiques comportant un ligand amine et nitrile, et de déplacement du groupement amine par un groupement nitrile. Le deuxième chapitre (4) décrit la réactivité et la cinétique de la réaction d’hydroamination et d’hydroalkoxylation d’oléfines activées, qui permet ainsi de mieux comprendre l’impact des différentes variables du système (groupements R et R’, température, substrats, solvent, etc.) sur la réactivité catalytique.

Desenvolvimento de métodos electroquímicos de quantificação de fármacos em amostras de água contaminadas

Este trabalho teve como objectivo, o desenvolvimento de um método electroquímico, para quantificação do fármaco carbamazepina (CBZ) em águas contaminadas. Neste trabalho foram utilizados quatro métodos voltamétricos: a voltametria cíclica, a voltametria de varrimento linear, a voltametria de onda quadrada e a voltametria de impulso diferencial. Os eléctrodos de trabalho utilizados foram, o eléctrodo de mercúrio de gota suspensa, o eléctrodo de carbono vítreo clássico e um eléctrodo de carbono vítreo modificado com um filme de nanotubos de carbono de paredes múltiplas (MWCNTs). O eléctrodo de mercúrio de gota suspensa permitiu o estudo da redução da CBZ numa região de potencial mais catódico, e os eléctrodos de carbono vítreo, com e sem modificação, permitiram o estudo da oxidação da CBZ numa região de potencial mais anódico. Nas condições experimentais estudadas, o eléctrodo de mercúrio de gota suspensa revelou ser um sensor voltamétrico pouco eficaz na determinação quantitativa da carbamazepina, em amostras com uma matriz complexa. Entre os eléctrodos de carbono vítreo, o eléctrodo de carbono vítreo modificado com os MWCNTs revelou ser o sensor voltamétrico mais eficaz e sensível, na detecção e determinação da carbamazepina. Modificado com um filme de nanotubos de carbono de paredes múltiplas, que previamente foram dispersos em dihexadecilhidrogenofosfato (DHP) e água, este novo eléctrodo permitiu obter uma resposta electroquímica da CBZ, consideravelmente superior ao eléctrodo não modificado. Utilizando a voltametria de varrimento linear e as condições experimentais consideradas óptimas, o eléctrodo nanoestruturado permitiu obter uma relação linear entre o sinal medido e a concentração da CBZ no intervalo 0.13- 1.60 M (30.7- 378 g -1), com os limites de detecção e quantificação mais baixos, até à data reportados com métodos electroquímicos (0.04 e 0.14M, respectivamente). O eléctrodo modificado foi aplicado na quantificação da CBZ, em formulações farmacêuticas, em águas naturais tratadas e em amostras de águas residuais, ambas dopadas, obtendo-se taxas de recuperação consideravelmente elevadas (100.6%, 98.0%,95.8%, respectivamente). Os resultados obtidos, na análise da CBZ em amostras ambientais, com o eléctrodo modificado, foram comparados com resultados obtidos por HPLC-UV e LC­ ESI-MS/MS, validando o método electroquímico desenvolvido neste trabalho. ABSTRACT: The aim of this work was to develop a new electrochemical method for the quantification of carbamazepine (CBZ) in contaminated waters. ln this study, four voltammetric methods were used: cyclic voltammetry, linear sweep voltammetry, square wave voltammetry and differential pulse voltammetry. the working electrodes used were the hanging mercury drop electrode (HMDE), the classical glassy carbon electrode (GCE), and a glassy carbon electrode modified with a film of multi-walled carbon nanotubes (MWCNls). Using HMDE, the reduction of CBZ was studied in the cathodic potential region. the CGE sensors, with or without modification, allowed the study of CBZ oxidation in the anodic potential region. ln the tested conditions, the results obtained for the quantification of CBZ using the HMDE sensor were not very satisfactory, especially when more complex samples were analysed. When the MWCNls-dihexadecyl hydrogen phosphate (DHP) film­ coated GCE was used for the voltammetric determination of CBZ, the results obtained showed that this modified electrode exhibits excellent enhancement effects on the electrochemical oxidation of CBZ. the oxidation peak current of CBZ at this film­ modified electrode increased significantly, when compared with that at a bare glassy carbon electrode. The enhanced electrooxidation and voltammetry of CBZ at the surface of MWCNTs-DHP film coated GCE in phosphate buffer solution (pH 6.71) was attributed to the unique properties of MWCNTs such as large specific surface area and strong adsorptive properties providing more reaction sites. The proposed method was applied to the quantification of CBZ in pharmaceutical formulations, drinking water and wastewater samples with good recoveries and low limits of detection and quantification (0.04 and 0.14 M, respectively), and was positively compared with chromatographic techniques usually used in the quantification of pharmaceutical compounds in environmental samples. HPLC-UV and LC-ESI-MS/MS were also used in the quantification of CBZ in pharmaceutical formulations and wastewater samples to prove the importance and accuracy of his voltammetric method.

New functional polythiophene based materials: fine-tuning of photovoltaic or chiroptical properties

There is a remarkable level of interest in the development of π-conjugated polymers (ICPs) which have been employed, thanks to their promising optical and electronic properties, in numerous applications including photovoltaic cells, light emitting diodes and thin-film transistors. Although high power conversion efficiency can be reached using poly(3-alkylthiophenes) (P3ATs) as electron-donating materials in polymeric solar cells of the Bulk-Heterojunction type (BHJ), their relatively large band gap limits the solar spectrum fraction that can be utilized. The research work described in this dissertation thus concerns the synthesis, characterization and study of the optical and photoactivity properties of new organic semiconducting materials based on polythiophenes. In detail, various narrow band gap polymers and copolymers were developed through different approaches and were characterized by several complementary techniques, such as gel permeation chromatography (GPC), NMR spectroscopy, thermal analyses (DSC, TGA), UV-Vis/PL spectroscopy and cyclic voltammetry (CV), in order to investigate their structural and chemical/photophysical properties. Moreover, the polymeric derivatives were tested as active material in air-processed organic solar cells. The activity has also been devoted to investigate the behavior of polythiophenes with chiral side chain, that are fascinating materials capable to assume helix supramolecular structures, exhibiting optical activity in the aggregated state.

3D electrocatalysts for the selective glucose oxidation

Nowadays, one of the most important scientific and environmental concern is to reduce global dependence on fossil fuels. The use of lignocellulosic biomass makes it possible to produce important platform molecules such as D-glucose, which is used to synthesize high value-added chemical products such as gluconic acid (GO) and glucaric acid (GA). Moreover, the electrocatalytic oxidation of glucose shows advantages compared to the classical synthesis route, such as the use of non-toxic reactants and milder conditions, making the process greener and more sustainable. In this work, electrocatalysts based on open-cell Ni metal foams were investigated for the glucose electrooxidation. They were used as supplied, oxidized at 500°C and 600°C, and after electrodeposition of Ni(OH)2. The electrocatalysts were characterized by cyclic voltammetry in NaOH solution 0.1M and in a basic D-glucose solution with different glucose concentrations (10mM and 50mM). The effect of the potential applied, the glucose concentration and the reaction time on conversion, selectivity and faradic efficiency were also investigated. 3D Ni electrocatalyst showed promising activity in the conversion of glucose towards gluconic acid, the sample calcined at 500°C showing the best results.

Sintesi e caratterizzazione di CaCu3Ti4O12 (CCTO) per applicazioni in fotoelettrocatalisi

A promising strategy to mitigate both the energy crisis and global warming is the development of solar fuels and chemicals using as feedstock CO2 in combination with simple molecules such as water. This process stores the solar energy into chemical bonds, leading to a carbon-neutral approach of fuels and chemicals production. Aim of this thesis was the synthesis and characterization of CaCu3Ti4O12 (CCTO)- based compounds to be used as visible light photocatalyst for CO2 to chemical conversion. Different compositions were produced doping CCTO with increasing concentration of iron into the perovskite’s A site in order to identify the materials with the highest photo- and photoelectrocatalytic properties. The most promising compositions were used to produce photoelectrodes by screen printing that were characterized by linear and cyclic voltammetry, impedance spectroscopy and Mott-Schottky analysis to evaluate the electrical conductivity and calculate the flat band potential and the number of charge carriers in the samples. The photoelectrodes were then tested in a photoelectrochemical (PEC) cell for the conversion of CO2 into fuel and chemicals. The results obtained confirm that CCTO-based materials can be considered promising materials for carbon dioxide photo-electrochemical reduction.

Sensori elettrochimici a base di PEDOT:PSS stampati a getto di inchiostro

Conductive polymers (CPS) are a class of carbon-based materials, capable of conducting electric current, characterized by metallic properties in combination with the intrinsic properties of conventional polymers. The structural model of the CP consists of a system of double π-conjugated on the backbone (polyene structure) which can easily undergo reversible doping reaching a wide range of conductivity. Thanks to their versatility and peculiar properties (mechanical flexibility, biocompatibility, transparency, ease of chemical functionalization, high thermal stability), CPS have revolutionized the science of materials giving rise to Organic Bioelectronics, the discipline resulting from the convergence between biology and electronics. The Poly (3,4-ethylenedioxythiophene) : poly (styrenesulfonate) (PEDOT: PSS), complex polyelectrolyte, in the form of a thin film, currently represents the reference standard in applications concerning Bioelectronics. In this project, two types of electrochemical sensors ink-jet printed on a flexible polymeric substrate, the polyethylene terephthalate, have been developed and characterized. The Drop on Demand (DOD) inkjet technology has allowed to control the positioning of fluid volumes of the order of picoliters with an accuracy of ± 25μm. This resulted in the creation of amperometric sensors and organic electrochemical transistors (OECT) all-PEDOT: PSS with high reproducibility. The sensors have been used for the determination of Ascorbic Acid (AA) which is currently considered an important benchmark in the field of sensors. In Cyclic Voltammetry, the amperometric sensor has detected AA at potentials less than 0.2 V vs. SCE thanks to the electrocatalytic properties of the PEDOT: PSS. On the other hand, the OECT detected AA concentrations equal to 10 nanomolar in Chronoamperometry. Furthermore, a promising new generation of all-printed OECTS, consisting of silver metal contacts, has been created. Preliminary results are presented.

Synthesis, Characterization, and Applications of a Novel Cu(II)-MOF Based on a Propargylcarbamate-Functionalized Isophthalate Ligand

This work describes the synthesis of a propargylcarbamate-functionalized isophthalate ligand and its use in the solvothermal preparation of a new copper(II)-based metal organic framework named [Cu(1,3-YBDC)]ˑxH2O (also abbreviated as Cu-MOF. The characterization of this compound was performed using several complementary techniques such as infrared (ATR-FTIR) and Raman spectroscopy, X-ray powder diffraction spectroscopy (PXRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS) as well as thermal and surface area measurements. Synchrotron X-ray diffraction analysis revealed that this MOF contains a complex network of 5-substituted isophthalate anions bound to Cu(II) centers, arranged in pairs within paddlewheel (or “Chinese lantern”) structure with a short Cu…Cu distance of 2.633 Å. Quite unexpectedly, the apical atom in the paddlewheel structure belongs to the carbamate carbonyl oxygen atom. Such extra coordination by the propargylcarbamate groups drastically reduces the MOF porosity, a feature that was also confirmed by BET measurements. Indeed, its surface area was determined to be low (14.5 ± 0.8 m2/g) as its total pore volume (46 mm3/g). Successively the Cu-MOF was treated with HAuCl4 with the aim of studying the ability of the propargylcarbamate functionality to capture the Au(III) ion and reduce it to Au(0) to give gold nanoparticles (AuNPs). The overall amount of gold retained by the Cu-MOF/Au was determined by AAS while the amount of gold and its oxidation state on the surface of the MOF was studied by XPS. A glassy carbon (GC) electrode was drop-casted with a Cu-MOF suspension to electrochemically characterize the material through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The performance of the modified electrodes towards nitrite oxidation was tested by CV and chronoamperometry.

Polyaniline-based materials and nanocomposites: from energy storage to sensing applications

The research work described in this thesis concerns materials for both energy storage and sensoristics applications. Firstly, the synthesis and characterization of magnetite (Fe3O4) functionalyzed with [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) capable to reduce the gold precursor chloroauric acid (HAuCl4) without the need of additional reducing or stabilising agents is described. These nanoparticles were tested to improve performances of symmetric capacitors based on polyaniline and graphite foil. Energy storage applications were investigated also during six months stay at EPFL University of Lausanne where an investigation about different tailored catalysts for Oxygen Evolution Reaction in a particular Redox Flow Battery was carried out. For what concerns sensing applications, new materials based on cellulose modified with polyaniline and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAMPSA) were synthesized, characterized and applied to monitor pressure, humidity, heart rate and lastly, bread fermentation in collaboration with the University of Fribourg and Zurich. The characterizations of all the materials investigated compriseed numerous techniques such as infrared attenuated total reflectance spectroscopy (IR-ATR), thermogravimetric analysis (TGA), scanning and transmission electron microscopy (SEM and TEM), alongside linear and cyclic voltammetry (LSV and CV), electrochemical impedance spectroscopy (EIS) and chronoamperometric analyses.

Design, synthesis and photovoltaic properties of some thiophene-based conjugated polymers for organic solar cells

The current issue of the resource of energy combined with the tendency to give a green footprint to our lifestyle have prompted the research to focus the attention on alternative sources with great strides in the optimization of polymeric photovoltaic devices. The research work described in this dissertation consists in the study of different semiconducting π-conjugated materials based on polythiophenes (Chapter I). In detail, the GRIM polymerization was deepened defining the synthetic conditions to obtain regioregular poly(3-alkylthiophene) (Chapter II). Since the use of symmetrical monomers functionalized with oxygen atom(s) allows to adopt easy synthesis leading to performing materials, disubstituted poly(3,4-dialkoxythiophene)s were successfully prepared, characterized and tested as photoactive materials in solar cells (Chapter III). A “green” resource of energy should be employed through sustainable devices and, for this purpose, the research work was continued on the synthesis of thiophene derivatives soluble in eco-friendly solvents. To make this possible, the photoactive layer was completely tailored starting from the electron-acceptor material. A fullerene derivative soluble in alcohols was successfully synthetized and adopted for the realization of the new devices (Chapter IV). New water/alcohol soluble electron-donor materials with different functional groups were prepared and their properties were compared (Chapter V). Once found the best ionic functional group, a new double-cable material was synthetized optimizing the surface area between the different materials (Chapter VI). Finally, other water/alcohol soluble materials were synthetized, characterized and used as cathode interlayers in eco-friendly devices (Chapter VII). In this work, all prepared materials were characterized by spectroscopy analyses, gel permeation chromatography and thermal analyses. Cyclic voltammetry, X-ray diffraction, atomic force microscopy and external quantum efficiency were used to investigate some peculiar aspects.

Inkjet-printed poly(N-isopropylacrylamide)/graphene electrodes for selective electroanalytical sensing

The main research topic of the present master thesis consisted in the modification and electrochemical testing of inkjet printed graphene electrodes with a thin polymeric hydrogel layer made of cross-linked poly(N-isopropylacrylamide) (PNIPAAM) acting as a functional layer to fabricate selective sensors. The first experimental activities dealt with the synthesis of the polymeric hydrogel and the modification of the active surface of graphene sensors through photopolymerization. Simultaneous inkjet printing and photopolymerization of the hydrogel precursor inks onto graphene demonstrated to be the most effective and reproducible technique for the modification of the electrode with PNIPAAM. The electrochemical performance of the modified electrodes was tested through cyclic voltammetry. Voltammograms with standard redox couples with either positive, neutral or negative charges, suggested an electrostatic filtering effect by the hydrogel blocking negatively charged redox species in near neutral pH electrolyte solutions from reaching the electrode surface. PNIPAAM is a known thermo-responsive polymer, but the variation of temperature did not influence the filtering properties of the hydrogels for the redox couples studied. However, a variation of the filter capacity of the material was observed at pH 2 in which the PNIPAAM hydrogel, most likely in protonated form, became impermeable to positively charged redox species and permeable to negatively charged species. Finally, the filtering capacity of the electrodes modified with PNIPAAM was evaluated for the electrochemical determination of analytes in presence of negatively charge potential interferents, such as antioxidants like ascorbic acid. The outcome of the final experiments suggested the possibility to use the inkjet-printed PNIPAAM thin layer for electroanalytical applications as an electrostatic filter against interferents of opposite charges, typically present in complex matrices, such as food and beverages.

Electrochemical Investigations into Blended Electrolytes Containing Ionic Liquids and a Glyme Solvent for Li-O­2 batteries

The Li-O2 battery may theoretically possess practical gravimetric energy densities several times greater than the current state-of-the-art Li-ion batteries.1 This magnitude of development is a requisite for true realization of electric vehicles capable of competing with the traditional combustion engine. However, significant challenges must be addressed before practical application may be considered. These include low efficiencies, low rate capabilities and the parasitic decomposition reactions of electrolyte/electrode materials resulting in very poor rechargeability.2-4 Ionic liquids, ILs, typically display several properties, extremely low vapor pressure and high electrochemical and thermal stability, which make them particularly interesting for Li-O2 battery electrolytes. However, the typically sluggish transport properties generally inhibit rate performance and cells suffer similar inefficiencies during cycling.5,6

In addition to the design of new ILs with tailored properties, formulating blended electrolytes using molecular solvents with ILs has been considered to improve their performance.7,8 In this work, we will discuss the physical properties vs. the electrochemical performance of a range of formulated electrolytes based on tetraglyme, a benchmark Li-O2 battery electrolyte solvent, and several ILs. The selected ILs are based on the bis{(trifluoromethyl)sulfonyl}imide anion and alkyl/ether functionalized cyclic alkylammonium cations, which exhibit very good stability and moderate viscosity.9 O2 electrochemistry will be investigated in these media using macro and microdisk voltammetry and O2 solubility/diffusivity is quantified as a function of the electrolyte formulation. Furthermore, galvanostatic cycling of selected electrolytes in Li-O2 cells will be discussed to probe their practical electrochemical performance. Finally, the physical characterization of the blended electrolytes will be reported in parallel to further determine structure (or formulation) vs. property relationships and to, therefore, assess the importance of certain electrolyte properties (viscosity, O2supply capability, donor number) on their performance.

This work was funded by the EPSRC (EP/L505262/1) and Innovate UK for the Practical Lithium-Air Batteries project (project number: 101577).

1. P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nat. Mater., 11, 19 (2012).

2. S. A. Freunberger, Y. Chen, N. E. Drewett, L. J. Hardwick, F. Barde and P. G. Bruce, Angew. Chem., Int. Ed., 50, 8609 (2011).

3. B. D. McCloskey, A. Speidel, R. Scheffler, D. C. Miller, V. Viswanathan, J. S. Hummelshøj, J. K. Nørskov and A. C. Luntz, J. Phys. Chem. Lett., 3, 997 (2012).

4. D. G. Kwabi, T. P. Batcho, C. V. Amanchukwu, N. Ortiz-Vitoriano, P. Hammond, C. V. Thompson and Y. Shao-Horn, J. Phys. Chem. Lett., 5, 2850 (2014).

5. Z. H. Cui, W. G. Fan and X. X. Guo, J. Power Sources, 235, 251 (2013).

6. F. Soavi, S. Monaco and M. Mastragostino, J. Power Sources, 224, 115 (2013).

7. L. Cecchetto, M. Salomon, B. Scrosati and F. Croce, J. Power Sources, 213, 233 (2012).

8. A. Khan and C. Zhao, Electrochem. Commun., 49, 1 (2014).

9. Z. J. Chen, T. Xue and J.-M. Lee, RSC Adv., 2, 10564 (2012).

An unusual axial–axial combination of alternating cyclic rings in the chair conformations of hexameric water and chlorine-water clusters

An alternating hexameric water (H2O)(6) cluster and a chlorine-water cluster [Cl-2(H2O)(4)](2-) in the chair forms combine axially to each other to form a 1D chain [{Cl-2(H2O)(6)}(2-)](n) in complex [FeL2]Cl center dot(H2O)(3) (L=2-[(2-methylaminoethylimino)-methyl]-phenol)]. The water molecules display extensive H-bonding interactions with monomeric iron-organic units to form a hydrogen-bonded 2D supramolecular assembly.