This dissertation describes the electrochemical synthesis of conducting polypyrrole (PPy), poly(N-methylpyrrole) (PNMPy), poly(3-methylpyrrole) (P3MPy), poly(pyrrole-2,6-dimethyl-β-cyclodextrin) P(Py-β-DMCD), poly(N-methylpyrrole-2,6-dimethyl-β-cyclodextrin) P(NMPy-β-DMCD) and poly(3-methylpyrrole-2,6-dimethyl-β-cyclodextrin) P(3MPy-β-DMCD) films by electrode potential cycling on a gold electrode in aqueous and nonaqueous (acetonitrile) electrolyte solutions containing lithium perchlorate. The resulting products were characterized by cyclic voltammetry, in situ UV-Vis spectroscopy, ex situ FT-IR spectroscopy, in situ surface enhanced Raman scattering (SERS) and in situ resistance measurements. For electrosynthesis of polymers in the presence of cyclodextrin, a (1:1) (mole-mole) compounds (host-guest-complex) of β-DMCD with Py, NMPy and 3MPy, respectively; previously characterized with proton NMR spectroscopy was used as starting material. Different cyclic voltammetric behavior was observed for polymers in aqueous and nonaqueous solutions during electrosynthesis. The results show that in nonaqueous solutions the oxidation potential of Py, NMPy and 3MPy monomers increases in the presence of cyclodextrin. The same results were observed for P(Py-β-DMCD) and P(NMPy-β-DMCD) in aqueous solution. The slight shift of the oxidation peak for polymers in the presence of cyclodextrin (CD) compared to polymers in absence of CD may be a result of the hydrophobic monomer partly or entirely included in the CD hydrophobic interior cavity. In situ resistance measurements of the PPy and PNMPy show that films prepared in acetonitrile solution have less resistance than those synthesized in aqueous solutions. Meanwhile, the results show that the resistance of the polymer increased in the following order PPy < P3MPy < PNMPy and P(Py-β-DMCD) < P(3MPy-β-DMCD) < P(NMPy-β-DMCD). The FT-IR spectroscopy was used to identify the polymers and to find evidence for the presence of the CD in the material. The spectra suggests no CD incorporation in the P(Py-β-DMCD) and P(NMPy-β-DMCD) films. In situ UV-Vis spectroscopy and in situ SERS measurements for the study of the structure and properties of electronically conducting PPy, PNMPy, P3MPy, P(Py-β-DMCD), P(NMPy-β-DMCD) and P(3MPy-β-DMCD) were carried out in two different media. The in situ SERS spectra of polymers deposited on the roughened gold substrate with ORC (oxidation-reduction cycle) pre-treatment indicated both a marked increase in intensity and a better resolution. / Diese Dissertation beschreibt die elektrochemische Synthese von leitfähigem Polypyrrol (PPy), Poly-N-Methylpyrrol (PNMPy), Poly(3-Methylpyrrol) (P3MPy), Poly(Pyrrol-2,6-dimethyl-β-cyclodextrin) P(Py-β-DMCD), Poly(N-Methylpyrrol-2,6-dimethyl-β-cyclodextrin) P(NMPy-β-DMCD) und Poly(3-Methylpyrrol-2,6-dimethyl-β-cyclodextrin) P(3MPy-β-DMCD) auf einer Goldelektrode durch Potentialzyklen in wässrigen und nichtwässrigen (Acetonitril) Elektrolytlösungen mit Lithiumperchlorat als Leitsalz. Die erhaltenen Stoffe wurden mit zyklischer Voltammetrie, in situ UV-Vis-Spektroskopie, ex situ FT-IR Spektroskopie, in situ oberflächen verstärkter Ramanspektroskopie (SERS) und in situ Widerstandmessungen charakterisiert. Für die Elektrosynthese der Polymere in Gegenwart von Cyclodextrin wurden 1:1 (Molverhältnis) Verbindungen (Wirt-Gast-Komplex) von β-DMCD mit Py, NMPy und 3MPy resp., charakterisiert mit Proton-NMR-Spektroskopie, als Ausgangsmaterial eingesetzt. Die zyklischen Voltammogramme ergaben unterschiedliches Verhalten der Polymere in wässrigen und nichtwässrigen Lösungen während der Elektrosynthese. Die Ergebnisse zeigen, dass sich in nichtwässrigen Lösungen das Oxidationspotenzial von Py, NMPy und 3MPy-Monomeren bei Anwesenheit von Cyclodextrin erhöht. Dieselben Resultate ergaben sich für P(Py-β-DMCD) und P(NMPy-β-DMCD) in wässriger Lösung. Die leichte Verschiebung des Oxidationspeaks der Polymere bei Anwesenheit von Cyclodextrin (CD) verglichen mit den Polymeren bei Abwesenheit von CD könnte das Resultat der teilweise oder vollständig im hydrophoben Hohlraum der CD eingeschlossenen hydrophoben Monomere sein. In situ Leitfähigkeitsmessungen von PPy und PNMPy zeigen, dass Filme, die in Acetonitrillösungen hergestellt wurden besser leitfähig sind als die Filme, die in wässrigen Lösungen hergestellt wurden. Die Ergebnisse zeigen, dass der Widerstand der Polymere in der folgenden Reihenfolge steigt: PPy < P3MPy < PNMPy and P(Py-β-DMCD) < P(3MPy-β-DMCD) < P(NMPy-β-DMCD). Die FT-IR-Spektroskopie wurde verwendet die Polymere zu identifizieren und die Anwesenheit der CD in das Material. Die Spektren schlägt vor, keine CD-Aufnahme in den P (Py-β-DMCD) und P (NMPy-β-DMCD) Filme. In situ UV-Vis- und in situ SERS-Messungen zur Untersuchung der Struktur und der Eigenschaften der elektronisch leitfähigen PPy, PNMPy, P3MPy, P(Py-β-DMCD), P(NMPy-β-DMCD) and P(3MPy-β-DMCD) wurden in 2 verschiedenen Medien durchgeführt. Die in situ SERS-Spektren der Polymere, abgeschieden auf aufgerauhter Goldoberfläche und Substrat durch ORC (Oxidations-Reduktions-Zyklus) –Vorbehandlung zeigten sowohl eine deutliche Erhöhung der Intensität als auch eine bessere Auflösung.

Supercapacitors are well known for their improvised power density compared to batteries. Ongoing research is mainly focused on improving the energy density of supercapacitors by using different electrode material nanocomposites. The recent research has revealed that graphene (G)-polyaniline (PANI) nanocomposite could be a promising material for supercapacitor applications. The supercapacitor is also associated with self-leakage current regardless of any electrode material. The main objectives of the project are to: (i) synthesize highly fabricate supercapacitor based of G-PANI electrode; (ii) improve the energy density of supercapacitor by applying ultrathin monolayer/monolayers film electrode surface. It is crucial to either improve or retain the effective capacitance of the dielectric film. The dielectric material chosen is polyvinylidene fluoride (PVDF) due to its dielectric constant and electrochemical properties. Langmuir-Schaefer (LS) technique is used to deposit the PVDF film onto the substrate. The optical properties of electrode materials were measured by UV-vis spectrophotometer. The surface morphology of the fabricated electrode material has been investigated using scanning electron microscopic (SEM) and atomic force microscopic (AFM) studies. The supercapacitor with and without dielectric layer have been studied using cyclic voltammetry, charging and discharging, and electrochemical impedance techniques, respectively. The specific capacitance has been found to increase by application of one monolayer of PVDF film of G-PANI electrode. However, the LS film of PVDF does not show the minimization of leakage current but revealed an increase in the specific capacitance due to enhancement in surface area associated with the electrode besides PVDF is also an electrochemical active material. The electrochemical investigation of various layers of PVDF on G-PANI in symmetric and asymmetric supercapacitor configuration has been presented in thesis. The future scope of the project could be designing the electrode with various number of layers of dielectric material that could reduce the leakage current, and retaining the specific capacitance of G-PANI nanocomposite electrodes.

M. Tech. Engineering: Chemical / Researches the usability and efficiency of the synthesized PPy/Al2O3 nanocomposite as adsorbent in Cr(VI) remediation from contaminated wastewaters.The specific objectives of the study are:to synthesise and characterize the PPy/Al2O3 nanocomposite ; to characterize the prepared nanocomposite using several sophisticated instruments such as, SEM, BET, XRD, et cetera ; to carryout batch adsorption equilibrium and kinetics studies for evaluating the performance of the nanosorbent and to gain insight into the underlying adsorption mechanisms.; to apply adsorption equilibrium and kinetic models.; to assess the breakthrough performance of the PPy/Al2O3 nanocomposite for Cr(VI) adsorption by varying operating parameters, in fixed bed column mode and to apply existing mathematical models to predict the performance of fixed bed adsorption systems and to obtain column design parameters.

In the field of chemical and biological sensors, the increased need for better sensitivity, faster response and higher selectivity during an analysis process, requires the development of more and more efficient transducing sensing layers. In this context, and with the aim to detect small non-electroactive molecules, such as atrazine (ATZ), we designed, characterized and developed sensing layers constituted by functionalized Molecularly Imprinted Conducting Polymers (MICP) and we integrated them into electrochemical and gravimetrical sensors. Starting from acetonitrile pre-polymerization media containing ATZ as template molecules in the presence of thiophene-based functional monomers (FM, namely TMA, TAA, EDOT, TMeOH or Th), differently functionalized and structurally different polythiophene-based FM-MICP films were electrosynthesized onto gold substrates and used for ATZ detection. The sensing properties of FM-MICP layers were shown to result from the presence in their backbones of pre-shaped FM-functionalized imprinted cavities which keep the memory of the targets. Nevertheless, non-specific adsorption onto the surface of the sensing layers takes place systematically, which affects the selectivity of the recognition process. Thanks to surface characterization techniques, we highlighted the influence of the thickness and of the structural properties of the layers on the efficiency of the recognition process. Besides, this latter was shown to operate in the bulk of the polymer matrixes thanks to layers porosity. On another hand, electrochemical measurements correlated with semi-empirical calculations demonstrated the influence of the nature of FM on the strength of the ATZ-FM interaction in the pre-polymerization medium, and then on the number of ATZ molecular imprints and on the sensitivity towards ATZ of the FM-MICP layers. We showed that TAA-MICP, which presents a low limit of detection (10-9 mol L-1) and a large dynamic range (10-8 to 10-4 mol L-1), is the best sensing layer since it offers the best compromise between high level of specific detection of ATZ and low level of non-specific adsorption. Finally, TAA-MICP was used as sensitive layer in an original Electrochemical Surface Acoustic Wave sensor (ESAW) which enabled simultaneous coupled gravimetric and electrochemical measurements.

First- principles modeling is used to predict hydrogen permeability through Palladium (Pd)-rich binary alloy membranes as a function of temperature and H2 pressure. We introduce a simplified model that incorporates only a few factors and yields quantitative prediction. This model is used to predict hydrogen permeability in a wide range of binary alloy membranes and to find promising alloys that have high hydrogen permeability. We show how our efficient Density Functional Theory (DFT)-based model predicts the chemical stability and proton conductivity of doped barium zirconate (BaZrO3), barium stannate (BaSnO3), and barium hafnate (BaHfO3). Our data is also used to explore the physical origins of the trends in chemical stability and proton conductivity among different dopants. We also study potassium tantalate (KTaO3), which is a prototype perovskite, to examine the characteristics of undoped perovskites. Specifically, we study the impacts of isotope effects, tunneling effects, and native point defects on proton mobility in KTaO3. It is important to find and develop solid-state Li-ion electrolyte materials that are chemically stable and have high ionic conductivities for high performance Li-ion batteries. We show how we predict the chemical stability of Li7La3Zr2O12, Li7La3Sn2O12, and Li7La3Hf2O12 with respect to carbonate and hydroxide formation reactions.

The work presented in the thesis is about the evaluation of Organic Electrochemical Transistors (OECTs) for fast scan cyclic voltammetry (FSCV). FSCV is a method which has been used for real time dopamine sensing both in vivo and in vitro. The method is sensitive to noise and could therefore benefit from signal preamplification at the point of sensing, which could be achieved by incorporation of OECTs. In this study the OECTs are based on the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The gate consists of gold microelectrodes of different sizes to be used one at a time. When dopamine is reacted at the gate electrode, the redox state of the PEDOT:PSS OECT channel is modulated and the resulting change in drain current can be measured. The gate current, which contains the sensing information, is after filtering obtained by differentiating the channel potential with respect to time. The derived gate current is plotted in cyclic voltammogram for different dopamine concentrations and the amplitude of the oxidation/reduction peaks can be used to determine the dopamine concentration. In this thesis for the first time it is demonstrated that OECTs can be used for FSCV detection of dopamine. The results are discussed and an outlook on future work is given.

P-xylene-bis(diethylsulphonium chloride) (PXBDC) monomer was synthesized by the reaction of &amp / #945 / ,&amp / #945 / -dichloro-p-xylene with tetrahydrothiophene or diethyl sulphide. Electrochemical behavior of this monomer (PXBDC) was examined by cyclic voltametry. Polymerization was achieved both by using electrochemical and chemical polymerization techniques. In the electrochemical technique, PPV was synthesized by constant potential electrolysis in acetonitrile-tetrabutylammonium tetrafluoroborate (TBAFB) solvent-electrolyte couple. The polymer obtained from the electrode surface was converted to the poly(p-phenylene vinylene) (PPV) by the thermal elimination reaction of diethyl sulphide and HCl. Also, PPV was doped via electrochemical doping with ClO4- dopant ion. The chemical structures were confirmed both by Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). The thermal behavior of chemically and electrochemically synthesized conducting polymers were investigated by Differential Scanning Calorimetry (DSC). Also, electrochromic and spectroelectrochemical properties of PPV was investigated by using UV-VIS spectrophotometer.

ABSTRACT IMMOBILIZATION OF INVERTASE, POLYPHENOL OXIDASE AND GLUCOSE OXIDASE IN CONDUCTING COPOLYMERS OF THIOPHENE-CAPPED POLYTETRAHYDROFURAN AND PYRROLE B&ouml / y&uuml / kbayram, AySe Elif Ph.D., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare January 2005, 123 pages Immobilization of invertase, polyphenol oxidase (PPO) and glucose oxidase (GOD) enzymes were performed in electrochemically synthesized two types of conducting copolymers. One end and two end thiophene-capped polytetrahydrofuran (TPTHF-1 and TPTHF-2) were copolymerized with pyrrole under conditions of constant potential electrolysis. The copolymers were characterized by thermal, spectroscopic and scanning electron microscopy analyses. Immobilization was carried out via entrapment of enzymes in two types of matrices during the copolymerization of pyrrole with the insulating polymers in the presence of sodium dodecyl sulphate (SDS). Kinetic parameters: Maximum reaction rate (Vmax) and Michaelis-Menten constant (Km) were determined for the enzyme electrodes. Temperature optimization, pH optimization, operational stability and shelf-life of the enzyme electrodes were investigated. Enzyme electrodes of polyphenol oxidase and glucose oxidase were used to determine the amount of their substrates in samples. Polyphenol oxidase converts mono and diphenols to quinone. Amount of phenolic compounds in two kinds of wines were determined by analyzing the quinone amount. Glucose oxidase converts &amp / #61538 / -D-glucose to D-glucono-1,5-lactone. Glucose amount was determined in two kind of factory-produced orange juices by analyzing D-glucono-1,5-lactone.

Two new monomers / 2-benzyl-5,12-dihydro-2Hpyrrolo[ 3&rsquo / ,4&rsquo / :2,3][1,4]dioxocino[6,7-b]quinoxaline (DPOQ) and 5,12- dihydrothieno[3&rsquo / ,4&rsquo / :2,3][1,4]dithiocino[6,7-b]quinoxaline (DTTQ), were synthesized. The chemical structures of the monomers were characterized by Nuclear Magnetic Resonance (1H-NMR), Fourier Transform Infrared (FTIR) and Mass Spectrometry (MS). Copolymer of DPOQ with bithiophene (BT) was synthesized via potentiostatic electrochemical polymerization in acetonitrile (ACN)-tetrabutylammonium tetrafluoroborate (TBAFB) solvent-electrolyte couple. For DTTQ, copolymerization with bithiophene was achieved via potentiodynamic method in dichloromethane (DCM)-tetrabutylammonium hexafluorophosphate (TBAFP) solvent-electrolyte couple. Characterizations of the resulting copolymers were performed by cyclic voltammetry (CV), FTIR, Scanning Electron Microscopy (SEM) and UV-Vis Spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the copolymer films were investigated. In addition, dual type polymer electrochromic devices (ECDs) based on P(DPOQ-co-BT) and P(DTTQ-co-BT) with poly(3,4- ethylenedioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.

The first chapter of this thesis describes the motivation behind using room temperature ionic liquids (RTILs) in gas sensor research and reviews current applications of RTILs in various sensors. The second chapter describes electrochemical polymerization of aniline in room temperature 1-butyl-3-methylimmidazolium ionic liquids without addition of any acid. It is shown that the polymerization of aniline in BMI(BF4) does require small but controlled amounts of water whereas the polymerization in BMI(PF6) and in BMI(TF2N) does not require any water addition. The third chapter describes the construction of reference electrodes for RTIL applications that have a known and reproducible potential versus the ferrocene/ ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag+ couple type, or of the second kind, based on Ag/AgCl in M+Cl-. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized. The fourth chapter describes the electrochemical preparation and spectral analysis of gold clusters by adding gold atoms one-by-one through polyaniline s ability to form a strong complex with chloroaurate at the protonated imine sites. Our results confirm that both the amount and the size of gold clusters affects the properties of the composite material. The fifth chapter describes the development and characterization of a CHEMFET sensing layer based on a composite of CSA-doped polyaniline (PANI), and the room temperature ionic liquid BMI(TF2N) for the sensing of ammonia gas. The work function responses of the cast films with and without IL are analyzed by step-wise changes of ammonia gas concentration from 0.5 to 694 ppm in air as a function of the mole fraction of IL to PANI. The PANI CSA/BMI(TF2N) layers shows enhanced sensitivities, lower detection limit and shorter response times. The final chapter describes the preparation and characterization of field-effect transistors with mixed ionic-electronic conductors that have been created by varying the ratio of room temperature ionic liquid and emeraldine salt of polyaniline. Transistor with high electronic conductivity (32mol% ES-PANI) and Au gate contact exhibited theoretical behavior of an IGFET; whereas, the purely ionic gate behaved irreproducibly, indicating that a capacitive divider has been formed in the gate.