No description available.

No description available.

This work centres around the electrochemical and structural studies of 1,2,3,5 and 1,3,2,4 dithiadiazolylium salts and associated radical derivatives. Chapter one provides a brief history of sulphur nitrogen chemistry, in particular developments of 1,2,3,5 and 1,3,2,4 dithiadiazolyUum/ heterocyclic species. Also a quick outline of the pathways my research took are discussed. The following chapter is solely dedicated to the electrochemical investigations of (i) mono substituted aryl 1,2,3,4 and 1,3,2,4, (ii) di substituted aryl 1,2,3,4 and 1,3,2,4 and (iii) pyridyl 1,2,3,5 dithiadiazolylium salts and associated derivatives. This electrochemical process of interest involved the reduction of the 6π dithiadiazolylium cation going to the 7π radical. This was studied using a technique called Cyclic Voltammetry. Results from this survey revealed that all the derivatives studied were quasi-reversible to the same degree under these experimental conditions. The E(_pc/2) potentials of meta and Para derivatives were observed to increase with acceptor property of the substituent group attached. Using the relationship E(_pc/2) = σp, when the potentials of these derivatives were plotted against corresponding Hammett a values two excellent linear free energy relationships for both sets of derivatives were seen to exist. For the other systems this is not found to be so. Rationalisation of these responses are described by examination of electronic, solvent and steric factors of analogous benzoic acid and dithiadiazolylium/zolyl derivatives and how they compare with each other. Chapter three concentrates on the structural properties of dithiadiazolyls and discusses the potential of these types of derivatives to form conducting, charge transfer or magnetically interesting materials. The X-ray structures of the following compounds were obtained and are described in detail: pMeS-C(_6)H(_4)-CNSSN•, pF-C(_6)H(_4)-CNSSN•, pCF(_3)-C(_6)H(_4)-CNSSN•, pNO(_2)-C(_6)H(_4)-CNSSN•, mBr- C(_6)H(_4)-CNSSN•, mClpMe-C(_6)H(_4)-CNSSN•,| mC(_5)H(_4)N-CNSSN• and pC(_5)F(_4)N-CNSSN•. Comparisons of how these and similar dithiadiazolyl compounds pack with a view to rationalising packing trends, in order to molecular tailor materials for applications, is tackled as well. The forth chapter concerns the experimental details of this research and features information on technical procedures, synthetic routes and characterisation on the compounds examined. Finally chapter five attempts to bridge the results of the previous chapters all together.

Ce travail de thèse a eu pour thème central la birnessite, un oxyde de manganèse ubiquiste dans le milieu naturel et jouant un rôle fondamental dans la géochimie des sols. La première partie de cette thèse a été consacrée à l’électrodépôt et à la caractérisation de la birnessite par des méthodes électrochimiques couplées à la diffraction des rayons X. La caractérisation DRX in-situ au cours de l’électrodépôt a permis de mettre en évidence, lorsqu’on est en présence du cation électrolytique Na+, la formation d’un précurseur, la busérite, alors qu’en présence du cation électrolytique K+, la synthèse aboutit directement à la birnessite sans formation d’intermédiaire. La réduction électrochimique de la birnessite a également été étudiée en fonction du milieu ([Mn(II)], pH, potentiel). Cette dernière se réduit en hausmannite(Mn3O4), feitknechtite (-MnOOH), ou en composé amorphe de Mn(II), selon les conditions expérimentales. Dans la deuxième partie de cette thèse, les films minces ont été utilisés pour étudier la réactivité de la birnessite vis-à-vis du glyphosate, ainsi que celle de son principal métabolite l’AMPA (acide amino-méthyl-phosphonique). Le glyphosate est dégradé avec formation simultanée d’AMPA, de formaldéhyde, d’ions phosphate, nitrate et ammonium sans modification macroscopique de la birnessite. Les quatre derniers sous-produits sont également obtenus lors de la dégradation de l’AMPA par la birnessite. Les bons rendements de dégradation obtenus au cours des interactions glyphosate/birnessite et AMPA/birnessite laissent envisager une possible application de ces échantillons pour le traitement des eaux usées. / This thesis has been focused on birnessite, a ubiquitous manganese oxide in the environment, which plays a fundamental role in soil geochemistry. The first part of this thesis has been devoted to the electrodeposition and the characterizations of birnessite by electrochemical methods coupled with X-ray diffraction. The in-situ XRD characterization during electrodeposition has shown, in presence of the electrolytic cation Na+, the formation of a precursor, buserite, whereas no precursor is formed in presence of electrolytic cation K+, the synthesis leading directly to birnessite. The electrochemical reduction of birnessite has also been studied in function of the medium ([Mn (II)], pH, potential). Birnessite is reduced into hausmannite (Mn3O4), feitknechtite (-MnOOH), or an amorphous compound of Mn (II), as function of experimental conditions. In the second part of this thesis, the thin films have been used to study the reactivity of birnessite for degrading glyphosate and its metabolite AMPA (amino-methyl phosphonic). Glyphosate is degraded with simultaneous formation of AMPA, formaldehyde, phosphate ion, nitrate ion and ammonium ion, without macroscopic modification of birnessite. The last four by-products are also obtained during the degradation of AMPA by birnessite. The good yields obtained during glyphosate / birnessite and AMPA / birnessite interactions permit to envisage a possible application of these thin films for the treatment of wastewater.

In this research,we used the electrochemical (cyclic voltammetry) method to synthesize (polyaniline) PANI thin film on the top of ITO substrate which applied extensively on polymer organic light emitting diodes based on ITO (170nm) / PANI (55nm ) / PFG(60 nm )/LiF(1nm)/Ca(10nm) / Al (200nm) . The PANI thin films have excellent optical and electric properties. According to the measurement results of ultraviolet visible spectrophotometry, the PANI thin films with different aniline monomer concentrations display the absorption peak at the range of 500nm to 600nm and have high light transmission near 90%. The conductivity of PANI thin film (2.02x10-2(s/cm)) is higher than that of PEDOT:PSS thin film (1.28x10-2(s/cm)). The highest occupied molecular orbital value of PANI thin film is about 5.0 eV that close to PEDOT:PSS thin film. Therefore, it is suitable act as hole transporting layer. In this study, we can control the surface morphology of PANI thin film by exchanging synthesized parameters. Finally, we have fabricated a PLED device with PANI as a hole transporting layer by electrochemical synthesis with at the aniline monomer concentration of 0.3M and the scan rate of 0.0.1 V/s. The device exhibits a maximum luminance of 10500 cd/m2 at 15 V and power efficiency of 0.25 lm/W at 10V.

No description available.

Aluminum-nickel (Al-Ni) alloys and Al/Ni bilayers were successfully electrodeposited from AlCl3-EMIM-NiCl2 electrolyte at room temperature. Dissolution of NiCl2 was shown to be favorable in Lewis basic (with molar ratio of AlCl3 < 0.5) AlCl3-EMIM solution. The use of electrochemically active Cu working electrode as opposed to inert W induced additional Cu oxidation and dissolution in the cyclic voltammetry scan. The reduction potentials of Al and Ni were found to be ~ – 0.3 and 0.15 V vs. Al/Al3+ respectively. Increasing [NiCl2] in the electrolyte leads to an increase of Ni concentration in the deposited structures. Dense and well-adherent Al-Ni alloys with Ni concentration up to 17.7 at.% were deposited by potential control. XRD analysis revealed that the deposited Al-Ni exhibit a supersaturated fcc crystalline structure. The visual appearance of the deposits ranged from bright silver, dull silver, grey, to black, where the darker shade typically indicated higher Ni content. SEM analysis revealed that the surface morphology of the deposits ranged from nodular to flake-like structures. Al-Ni alloy typically showed nodular morphology with cauliflower structure. Flake structures, which were independent of substrate roughness, were found to develop under pulsed potential deposition with 1:1 duty ratio. The concentration of Ni in electrodeposited Al-Ni alloys increases nonlinearly with the increase in molarity of NiCl2. Al and Ni contents increase with increasing the time of positive and negative cycle of the pulse respectively. Decreasing the frequency by half resulted in almost double the amount of Ni in the deposited alloy. A smoother substrate increased Ni concentration from 6 to 17.7 at.%. Al/Ni bilayer was successfully deposited in 1.5:1 AlCl3-EMIM containing 0.026 M NiCl2. Deposition of Al on Ni was achieved using constant potential and pulse potential control. The deposition of Ni on Al is complicated since the deposition potential of Ni lies in the vicinity of Al stripping potential thus inducing competition between Ni deposition and Al stripping.

tert-butyl 1-methoxycarbonyl-1-ferrocenecarbamate, Boc-NH-Fc-COOMe, (1) was synthesized according to the literature procedure and modified to 1-amino-n′-ferrocenemethylcarboxylate, 1,n′-H2N-Fc-COOCH3 (2) by removing the Boc-group with TFA/Et3N mixture in dichloromethane. Compound 2 reacted with alkylating agents like MeI, EtI, EtSCH2CH2Cl (MA) and (CN)(EtO)2P(O) (NA) to form MeNH-Fc-COOMe (3), EtNH-Fc-COOMe (4), EtSCH2CH2NH-Fc-COOMe (5), (EtO)2P(O)NH-Fc-COOMe (6), respectively. Cyclic voltammetry (CV) of these compounds showed different half-wave potential characteristics compared to aminoferrocene and was dependent on the nature of the substituents, which was rationalized by molecular orbital calculations. Electron donating groups (Me, Et and 2-chloroethyl ethylsulfide, MA) shifted the half-wave potential towards the cathodic direction while electron withdrawing group like diethyl cyanophosphonate, NA, shifted it toward anodic direction. Anodic to cathodic peak separation were found to be within 62-88 mV indicating a quasi-reversible system. <p>Hydrolysis of compound 1 resulted in the formation of tert-butyl 1-methoxycarbonyl-1-ferrocenecarboxylic acid, Boc-NH-Fc-COOH, (11) which was coupled with cystamine using the EDC/HOBt protocol to synthesize the cystamine conjugate [BocHN-Fc-CO-CSA]2 (12). This molecule is equipped with an amino group that directly linked to the redox receptor. Compound 12 was fully characterized by spectroscopic methods and by single crystal x-ray diffraction. The cystamine conjugate 12 formed films on gold substrates, which upon deprotection of the amino group, reacted with chemical warfare agents (CWAs) mimics, such as EtSCH2CH2Cl (MA), a simulant for the sulfur mustard HD, and (CN)(EtO)2P(O) (NA), a simulant for the nerve agent Tabun. Their reaction with the surface-bound ferrocene derivative results in the formation of N-substituted products. <p>CV measurements showed anodic shifts of the Fc redox potentials by 50 (±5) mV after exposure to MA, and NA. Measurements by quartz crystal microbalance (QCM) showed an increase in mass upon exposure to MA and NA. Ellipsometry measured a film thickness increase from 6 (±1) Å for the deprotected film to 10 (±4) Å for the film modified with MA and to 7 (±2) Å for the film modified with NA. The surfaces were analyzed by x-ray photoelectron spectroscopy (XPS) and clearly showed the attachment of the cystamine conjugate on the surface and its reaction with CWAs mimics.

Metal hydrides are used as anode material in nickel metal hydride batteries and are of particular interest because of the potential to be a part of energy systems completely involving renewable sources (e.g. solar power, wind power etc.). Preparation and electrochemical characterization of metal hydride electrodes have not previously been performed at the Department of Chemistry – Ångström Laboratory. Two basic techniques that are desired to be used in the characterization are cyclic voltammetry and chronopotentiometry. This thesis work is aimed at preparation and electrochemical characterization of a metal hydride electrode and, as a complement, study the electrode with X-ray diffraction. LaNi3.55Co0.75Mn0.4Al0.3, a standard material for metal hydride electrodes previously studied by Khaldi et al. was chosen, to ensure that electrochemical absorption of hydrogen was possible, and to be able to compare electrochemical results [1-3]. LaNi3.55Co0.75Mn0.4Al0.3 was synthesized with arc melting, with additional annealing at 900˚C for five days, ground in a cemented carbide ball mill and sieved to less than 56 µm. Electrodes were prepared containing 90 wt.-% of LaNi3.55Co0.75Mn0.4Al0.3 powder, 5 wt.-% of polytetrafluoroethylene and 5 wt.-% of carbon black. The hydrogen absorption and desorption capabilities of the electrode were studied electrochemically with cyclic voltammetry and chronopotentiometry, and the structural changes associated with absorption of hydrogen was studied with X-ray diffraction. The capacity increased, probably from activation of the material, during initial cycling up to the maximum capacity of 294 mAh/g, obtained after 9 cycles, followed by a small decrease, probably caused by corrosion and passivation of the material, in capacity of the remaining 11 cycles. Activation of the material causes the charge and the discharge potential to shift to a more positive and a more negative value, respectively. The final values for the charge potential and the discharge potential were -841mV and -945 mV vs. Hg/HgO, respectively, after 16 cycles. Khalid et al. [1-3]reported a maximum capacity of 300 mAh/g, a charge potential of about -960 mV and a discharge potential of about -840 mV after 16 cycles the results obtained in this study are considered to be in good agreement with those reported. X-ray diffraction of the electrodes revealed, as expected, a cell volume change of the charged electrode compared to the discharged electrode. The change in cell volume corresponds to an estimated capacity of 303 mAh/g, which is very close to the, above mentioned, electrochemically obtained maximum capacity of 294 mAh/g.

tert-butyl 1-methoxycarbonyl-1-ferrocenecarbamate, Boc-NH-Fc-COOMe, (1) was synthesized according to the literature procedure and modified to 1-amino-n′-ferrocenemethylcarboxylate, 1,n′-H2N-Fc-COOCH3 (2) by removing the Boc-group with TFA/Et3N mixture in dichloromethane. Compound 2 reacted with alkylating agents like MeI, EtI, EtSCH2CH2Cl (MA) and (CN)(EtO)2P(O) (NA) to form MeNH-Fc-COOMe (3), EtNH-Fc-COOMe (4), EtSCH2CH2NH-Fc-COOMe (5), (EtO)2P(O)NH-Fc-COOMe (6), respectively. Cyclic voltammetry (CV) of these compounds showed different half-wave potential characteristics compared to aminoferrocene and was dependent on the nature of the substituents, which was rationalized by molecular orbital calculations. Electron donating groups (Me, Et and 2-chloroethyl ethylsulfide, MA) shifted the half-wave potential towards the cathodic direction while electron withdrawing group like diethyl cyanophosphonate, NA, shifted it toward anodic direction. Anodic to cathodic peak separation were found to be within 62-88 mV indicating a quasi-reversible system. <p>Hydrolysis of compound 1 resulted in the formation of tert-butyl 1-methoxycarbonyl-1-ferrocenecarboxylic acid, Boc-NH-Fc-COOH, (11) which was coupled with cystamine using the EDC/HOBt protocol to synthesize the cystamine conjugate [BocHN-Fc-CO-CSA]2 (12). This molecule is equipped with an amino group that directly linked to the redox receptor. Compound 12 was fully characterized by spectroscopic methods and by single crystal x-ray diffraction. The cystamine conjugate 12 formed films on gold substrates, which upon deprotection of the amino group, reacted with chemical warfare agents (CWAs) mimics, such as EtSCH2CH2Cl (MA), a simulant for the sulfur mustard HD, and (CN)(EtO)2P(O) (NA), a simulant for the nerve agent Tabun. Their reaction with the surface-bound ferrocene derivative results in the formation of N-substituted products. <p>CV measurements showed anodic shifts of the Fc redox potentials by 50 (±5) mV after exposure to MA, and NA. Measurements by quartz crystal microbalance (QCM) showed an increase in mass upon exposure to MA and NA. Ellipsometry measured a film thickness increase from 6 (±1) Å for the deprotected film to 10 (±4) Å for the film modified with MA and to 7 (±2) Å for the film modified with NA. The surfaces were analyzed by x-ray photoelectron spectroscopy (XPS) and clearly showed the attachment of the cystamine conjugate on the surface and its reaction with CWAs mimics.