Polypyrrol (PPy) ist ein typischer Vertreter der intrinsisch leitfähigen Polymere und wird auf zahlreichen Gebieten, wie Analytik, Korrosionsschutz oder Elektrotechnik angewendet. Dabei nutzt man die elektronische Schaltbarkeit, die Stabilität und die gute Oxidierbarkeit sowie die Wasserlöslichkeit der Monomere aus. Im Rahmen dieser Arbeit wurde der Einfluss verschiedener Parameter, wie Temperatur, Monomerkonzentration und Leitsalz, auf die elektrochemische Polymerisation von Pyrrol untersucht. Des Weiteren sollte die Wirkung eines statischen Magnetfeldes auf die Synthese und das Ionenaustauschverhalten überprüft werden. Als Messverfahren kamen die elektrochemische Quarzmikrowaage (EQCM) und die elektrochemische Impedanzspektroskopie (EIS) zum Einsatz. Bei der Auswertung der EQCM-Daten wurde ein von Efimov entwickeltes mathematisches Modell zur Bestimmung des komplexen Schermoduls angewendet. Dadurch war eine in situ Verfolgung der viskoelastischen Eigenschaften während der Abscheidung und des Ionenaustausches möglich. Um den hydrodynamischen Einfluss auf die Synthese von PPy zu untersuchen, wurden Messungen an einer rotierenden Scheibenelektrode durchgeführt. Die daraus gewonnenen Erkenntnisse vermittelten eine Vorstellung, wie sich eine durch den magnetohydrodynamischen Effekt hervorgerufene Rührung auf die Grenzströme der potentiostatischen Abscheidung verschiedener PPy|Leitsalz Systeme auswirkt. Ferner ist die Abscheidung von PPy aus Phosphorsäure betrachtet worden, da diese Schichten eine Relevanz für den Korrosionsschutz besitzen.

Electrooxidation has been used to deposit thin film polyaniline as well as its derivative - thin film poly (ortho-phenylenediamine) (POPD) and poly (meta-phenylenediamine) (PMPD) on carbon electrodes, which are subsequently used to monitor the environmental heavy metal ions (Hg2+, Pb2+ ,Cd2+) through a rather unusual "blocking" of anodic stripping for these metals. Using Hg2+ as a model, its cyclic voltammogram for a modified glassy carbon electrode with the resultant polymer shows an enhanced cathodic peak that increases linearly with the analyte ion concentration. POPD also exhibits unique selective detection for organic species. Acetaminophen and uric acid can be preferentially detected over ascorbic acid from a mixture of these three compounds. In addition, the effect of carbon nanotubes incorporated in polyaniline (PAN) film is observed to have enhanced electrochemical catalytic activities on the remedy of environmental dichromate.

No description available.

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Philosophiae Doctor - PhD / This thesis is based on the study of electropolymerization and electrochromism of poly(4,7- dithien-2-yl-2,1,3-benzothiadiazole) (P(DTBT) and its copolymer with 3-methoxythiophene (MOT) in imidazolium ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimbf4) hydrophilic, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimpf6) and 1- butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (bmimtnf2) hydrophobic ILs. Traditional organic solvents acetonitrile and dichloromethane in the presence of 0.1 M tetrabutylammonium perchlorate (n-Bu4NClO4) as a supportive electrolyte was also used as a medium for comparison. Besides, a more hydrophobic ionic liquid, 1-octyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide (octmimtnf2) was also used for the electrodeposition of poly(3-methoxythiophene) (PMOT). The techniques employed are cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), uv-visible spectroelectrochemistry and scanning electron microscopy (SEM). 4,7-Dithien-2-yl-2,1,3-benzothiadiazole (DTBT) a type of donor –acceptor monomer and 3- methoxythiophene (MOT) has been electropolymerized using ionic liquids as growth and supportive electrolytes.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work was realized characterization studies of a new material, poly (3- hidroxyphenylacetic acid) and its application for the construction of an amperometric immunosensor for detection of Acute Myocardial Infarction (AMI). Initially, it was carried out the electropolymerization of 3-hidroxyphenylacetic acid at three different pH's (0.0, 6.5 and 12.0) which could be assessed, electrochemically, the relationship between the behavior of the polymer and the reaction s pH. It was found that in the acid solutions (pH 0.0) the formation of electrochemically active material is more evident. Moreover, using electrochemical techniques, were carried out investigations on the structure of the polymeric material by using cationic and anionic probes. Monomer and polymer were characterized by infrared spectroscopy (FTIR), Ultra-Violet (UV/Vis.) and fluorescence; thermal analysis (DTA and TGA) and structural analysis (XDR). These studies were extremely important to highlight the main differences between the starting material (monomer) and electropolymerized material (polymer), and in particular assess the main characteristics of the polymer in order to enable its use as a platform to the proposed immunosensor. Studies of the immunosensor were conducted using two substances that acted as indicators of the reaction between the specific antibody for the AMI (anti-troponin T) and specific antigen for AMI (troponin T), hexaaminruthenium chloride and ferro/ferricyanide potassium. The results showed that the hexaaminruthenium chloride showed the best performance to indicate the formation of antibody-antigen complex wich occurs in the AMI. / Neste trabalho foram realizados estudos de caracterização de um novo material, o poli(ácido 3-hidroxifenilacético) e sua aplicação para construção de um imunossensor amperométrico para detecção do Infarto Agudo do Miocárdio (IAM). Inicialmente, foi realizada a eletropolimerização do ácido 3-hidroxifenilacético em três pH s diferentes (0,0; 6,5 e 12,0) onde foi possível avaliar, eletroquimicamente, a relação entre o comportamento do polímero formado e o pH do meio reacional. Foi possível constatar que em meio ácido (pH 0,0) a formação do material eletroquimicamente ativo é mais evidenciada. Além disso, com o auxílio de técnicas eletroquímicas, foram realizadas investigações sobre a estrutura do material polimérico formado, utilizando sondas catiônicas e aniônicas. Monômero e polímero foram caracterizados por técnicas espectroscópicas de Infravermelho (FTIR), Ultra-Violeta (UV/Vis.) e Fluorescência; análises térmicas (TGA e DTA) e análises estruturais (DRX). Estes estudos foram de extrema importância para destacar as principais diferenças entre o monômero e o material eletropolimerizado e, principalmente, avaliar as principais características do polímero, no sentido de viabilizar a sua utilização como plataforma do imunossensor proposto. Os estudos do imunossensor foram conduzidos utilizando-se duas substâncias que atuaram como indicadores da reação entre anticorpo específico para o IAM (antitroponina T) e antígeno específico para o IAM (troponina T), o cloreto de hexaaminrutênio II e o ferro/ferricianeto de potássio. Os resultados obtidos mostraram que o cloreto de hexaaminrutênio II teve melhor desempenho para indicar a formação do complexo anticorpo-antígeno, característico no evento do IAM. / Mestre em Química

Philosophiae Doctor - PhD

The main motivation of this thesis is derived from the fact that physics of disordered systems like conjugated polymer has yet not achieved as concrete understanding as ordered and crystalline systems such as inorganic semiconductors. Through the work done in this thesis, several efforts have been made in order to understand basic charge transport (hopping, current injection) phenomena and photo-physical properties (photoluminescence quenching, absorption, photoconductivity) in conjugated polymer and their hybrid composites. The thesis consists of 7 chapters. Chapter 1 discusses the background knowledge and information of the general properties of conjugated polymers, quantum dots and their hybrid nanocomposites. Chapter 2 deals with the sample preparation and experimental techniques used in this thesis. Chapter 3 elaborates the temperature and field dependent anisotropic charge transport in polypyrrole. Chapter 4 presents an idea to probe and correlate disorder and transport properties using impedance and Raman spectroscopy. Chapter 5 mainly talks about the doping level dependent photophysical and electrical properties of poly(3-hexylthiophene). Chapter 6 reveals the charge transport phenomena in hybrid composites of poly(3,4-ethyldioxythiophene):polysterene sulfonate (PEDOT:PSS) and cadmium telluride quantum dots. Chapter 1: Conjugated polymers and their hybrid systems are easily processible and cost effective material having huge scope for advanced materials of the future. Although variable range hopping (VRH) is widely accepted to model charge transport in π-conjugated systems, but at very low temperatures, high fields, high carrier concentrations one need to explore other models. Conjugated polymers are anisotropic intrinsically. Therefore, anisotropic charge transport can provide basic insights about the physics of charge hopping. Quantum dots, and their hybrid nanocomposites with semiconducting polymers receiving a huge attention for light emission and photovoltaic purposes. It is important to learn about the charge injection,barrier heights, etc. in order to achieve efficient hybrid devices. Chapter 2: Synthesis of the samples, both conjugated polymers and quantum dots, and fabrication of hybrid devices is an important and integral part of this thesis. An Electropolymerization technique is used for making polymer samples on conducting substrates. This is quite interesting because one can tune doping level, disorder and thickness simultaneously. Hydrothermal process is adopted to get highly aqua-dispersible quantum dots. Samples are characterized by different techniques like Raman spectroscopy, energy dispersive spectroscopy. Photoluminescence, UV-Vis absorption, transmission electron microscopy and atomic force microscopy are used to explore several properties of the polymer and hybrid nanocomposites. Chapter 3: It is known that conjugated polymers are intrinsically one–dimensional materials. Therefore it is important to learn anisotropic behavior of these complex systems. Hence, a comparison of electronic transport to their morphology has been carried out and role of carrier density and disorder is discussed further. Both in-plane and out-of-plane charge transport is studied in electrochemically deposited polypyrrole on platinum. Strong anisotropy is observed in the system which is correlated to granular morphology. Field dependence of anisotropic conductivity is also explored. Field scaling analysis shows that all field dependent curves of conductance at different temperatures can fall on to single master curve. Glazman – Matveev model is used to describe nonlinear conduction in field dependence and nonlinearity exponent is estimated. Disorder and carrier density along with the morphological structure like length and orientation of polymer chains with stacking arrangement of different layers in PPy films play an important role in governing the anisotropy in transport properties. Chapter 4: Two different techniques, namely impedance and Raman spectroscopies are used to probe disorder and transport properties in the polypyrrole. An effort is made to correlate the transport properties to the morphology by probing disorder via two different spectroscopic techniques. Frequency dependence of both real and imaginary part has shown that disorder and inhomogeneity varies in different PPy devices, which thus affect the transport properties like conductivity and mobility. Mobility values along the thickness direction for each sample reveal the impact of disorder on out-of¬plane geometry. A circuit based on consideration of the distributed relaxation times, is successfully used to obtain the best fit for the Cole–Cole plot of various PPy devices. FWHM of the de-convoluted peaks of Raman spectra is attributed to the change in distribution of the conjugation length in the PPy films. Chapter 5: The main focus of this chapter is the qualitative exploration of different photo-physical and electrical properties of electropolymerized poly(3-hexylthiophene) and their dependence on doping level. Photoluminescence quenching, band edge shifting in absorption spectra, electrochromic effect, significant enhancement in photocurrent at optimum doping level, two relaxation behaviors in reactance spectra and presence of negative capacitance at low frequencies are distinct features which are observed in poly(3-hexylthiophene) in this work. Quenching in photoluminescence intensity is attributed to charge transfer occurring between polymer chains and dopant ions. Two semicircles in the Cole-Cole plots refer to two type of relaxation process occurring in bulk layer and at interface. Frequency response of capacitance at higher bias and lo side of frequency shows a negative capacitance due to the relaxation mechanism associated with the space-charge effect. Chapter 6: Synthesis of quantum dots and fabrication of hybrid devices is one of the catchy parts of this chapter. Huge quenching photoluminescence intensity and very high increment (~ 400 %) in photocurrent clearly depict the charge transfer at molecular level. Temperature dependent current–voltage characteristics show the absence of thermionic emission since the barrier height is more than the thermal energy of the carriers. Further analysis confirms that the charge carrier injection of ITO/PPCdTe3/Al device is controlled by tunneling processes. The hybrid system has shown a peculiar transition from direct tunneling to Fowler–Nordheim tunneling mechanism which is because of the change in shape of the barrier height from trapezoidal to triangular type with increase in applied electric field. Chapter 7: The conclusions of the different works presented in this thesis are coherently summarized in this thesis. Thoughts and prospective for future directions are also summed up.