Conjugated polymers that exhibit high electronic conductivities play key roles in the emerging field of molecular electronics. In particular, linking metal centres with useful electrochemical, photophysical, or catalytic properties to the backbone, or within the polymer chain itself, is a topic which has attracted a significant amount of interest lately. Structurally rigid monomers that can be electropolymerised to form highly conducting molecular wires may provide new insights into conduction mechanisms, e.g., exploiting resonant superexchange (electron-hopping) by tuning the energies of redox centre and bridge states. The focus of this thesis lies on the electrochemical investigation of preparation, growth dynamics, and charge transport dynamics of oligothiophene/transition metal hybrid materials. The incorporation of ruthenium(II) and osmium(II) terpyridine complexes into such polymeric assemblies was accomplished by an electropolymerisation procedure, to produce rod-like oligothienyl-bridged metallopolymers. The properties of the monomers used were characterised by optical spectroscopy and electrochemical techniques. Charge transport was studied in detail for some of the materials created, and it was found that the electron transport rate and dc conductivity was enhanced by up to two orders of magnitude compared to relevant non-conjugated polymers, demonstrating the usefulness of this approach for optimization of charge transport in metallopolymers. The charge transport diffusion coefficent was determined to (2.6 ± 0.5) x 10-6 cm2 s-1 for a quaterthienyl-bridged {Os(tpy)2} polymer by use of an electrochemical steady-state method carried out using a transistor-like experimental geometry. It was found that charge transport in these materials is concentration-gradient driven. The rate limiting step of the charge transport process was investigated using electrochemical impedance spectroscopy. The electropolymerisation dynamics of one of the monomers was studied using microelectrodes, and the results obtained shows that electropolymerisation is highly efficient, and indicate that mass transport controls this process. Through a combination of controlled potential deposition and SEM imaging it was demonstrated that it is possible to exploit the edge effect of microelectrodes to promote film growth in a direction co-planar with the electrode surface.

In this study three different 3-ester substituted thiophene monomers were synthesized via esterification reaction of 3-thiophene ethanol with adipoyl chloride or sebacoyl chloride or octanoyl chloride in the presence of triethylamine at 00C. Characterizations of the monomers were performed by 1H-NMR, 13C-NMR, FTIR, DSC, TGA techniques. Electrochemical behavior of the monomers both in presence or absence of BFEE were studied by cyclic voltammetry. Results showed the astonishing effect of BFEE on the polymerization, where free standing films of the homopolymers could be synthesized. Copolymers of the monomers with thiophene or 3-methyl thiophene were synthesized at constant potential electrolysis and the resultant polymers were characterized by FTIR, DSC, TGA, SEM and conductivity measurements. Second part of the study was devoted to investigate the one of most interesting property of conducting polymers, the ability to switch reversibly between the two states of different optical properties, &lsquo / electrochromism&rsquo / . In recent years there has been a growing interest in application of conducting polymers in electrochromic devices. Thus, electrochromic properties of the synthesized conducting polymers were investigated by several methods like spectroelectrochemistry, kinetic and colorimetry studies. Spectroelectrochemistry experiments were performed in order to investigate key properties of conjugated polymers such as band gap, maximum absorption wavelength, the intergap states that appear upon doping and evolution of polaron and bipolaron bands. Switching time and optical contrast of the homopolymers and copolymers were evaluated via kinetic studies. Results implied the possible use of these materials in electrochromic devices due to their satisfactory electrochromic properties like short switching time and stability. Generally the homopolymers displayed color changes between yellow, green and blue colors upon variation of applied potentials. Fine tuning of the colors of the polymers were accomplished by techniques like copolymerization and lamination. These studies were supported with experiments like spectroelectrochemistry and FTIR. Results showed the possible control of the color of the electrochromic material in a predictable, controlled and reproducible manner. Yet, it was possible to achieve different tones of yellow, green, orange color in neutral state of these materials. As the last part of the study, dual type electrochromic devices based on polymers of 3-ester substituted thiophenes with poly(3,4-ethylenedioxythiophene) were constructed, where the former and the later functioned as anodically and cathodically coloring layers respectively. Spectroelectrochemistry, switching ability, stability, open circuit memory and color of the devices were investigated and the results revealed that these devices have satisfactory electrochromic parameters.

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.

Die elektrochemische Copolymerisation von Furan und Thiophen oder 3-Chlorothiophen wurde erfolgreich realisiert in einer Elektrolytlösung von Bortrifluorid-Diethylether + Ethylether (Verhältnis 1:2) bei konstantem Elektrodenpotenzial. Die Zugabe von Trifluoroessigsäure (TFA) (10 Vol-%) zu Bortrifluorid-Diethylether + Ethylether (Verhältnis 1:2) erniedrigte das Oxidationspotenzial der Monomere; die Polymerisationsgeschwindigkeit erhöhte sich, da TFA die Ionenleitfähigkeit des Elektrolyts vergrößert. Die Homopolymere zeigen nur einen Redoxpeak, verursacht durch Polymeroxidation und - reduktion. Die elektrochemische Copolymerisation wird bei verschiedenen Potenzialen und mit unterschiedlichen Thiophen- oder 3-Chlorothiophenkonzentrationen untersucht. Die Copolymere zeigen ein Redoxpeakpaar, dessen Position sich wesentlich von der der Homopolymere unterscheidet. Mit zunehmendem Polymerisationspotenzial und/oder zunehmender Konzentration an Thiophen- oder 3-Chlorothiophen werden auch mehr Thiophen- oder 3-Chlorothiopheneinheiten in den Copolymerfilm eingebaut. Ein Elektropolymerisationmechanismus wird für die Copolymere vermutet und die Copolymere weisen eine recht gute Langzeitstabilität der Redoxaktivität nach Zyklen in Acetonitril auf. In situ UV-Vis-Spektren der Homo- und Copolymerfilme wurden gemessen und λ1max, welches dem π → π*- Übergang entspricht, wurde bestimmt. Der optische Übergang bei λ2max vom Valenzband in das höhere Bipolaronband wurde ebenfalls bestimmt. Die Bandlücke für die Homo- und Copolymerfilme beim direkten Übergang wurde von der Kante im Absorptionsspektrum abgeschätzt. Die elektrochemische Thermodynamik für die Homo- und Copolymerfilme deutet darauf hin, dass jeweils ein Elektron von den Polymersegmenten, bestehend aus 4 Monomereinheiten, entfernt wird. Die untersuchten leitfähigen Filme zeigen einen Leitfähigkeitssprung mit einer stabilen Leitfähigkeit bis EAg/AgCl= 2 V. Diese Leitfähigkeitsänderung ist reversibel. Polyfuran hat verglichen mit Polythiophen eine geringere Leitfähigkeit und die Leitfähigkeit von Poly(3-chlorothiophen) ist rund eine Zehnerpotenz niedriger als die von Polythiophen. Da das in situ Leitfähigkeitsverhalten der Copolymere nicht die Summe der einzelnen Homopolymere bildet, kann man ausschließen, dass es sich bei den abgeschiedenen Copolymeren um Blockcopolymere handelt. Mit Hilfe der FTIR-Spektroskopie wurden Schwingungsspektren der Homo- und Copolymerfilme aufgenommen. Die Ergebnisse zeigen, dass es zur α-α'-Verknüpfung zwischen den Radikalkationen während der Copolymerisation kommt, was charakteristisch ist für α-substituierte fünfgliedrige heterozyklische Verbindungen. Der Mechanismus der elektrochemischen Degradation von Furan-Thiophen-Copolymeren wird ebenfalls mit Hilfe der gemessenen Spektren beschrieben. Die in situ Resonanz-Raman-Spektroskopie ergab, dass die spektroskopischen Eigenschaften der Copolymere zwischen denen der Homopolymere lagen. Bei höheren Polymerisationspotenzialen und höheren Konzentrationen an Thiophen oder 3-Chlorothiophen werden mehr Thiophen- oder 3- Chlorothiopheneinheiten in die Copolymerketten eingebaut. Es ist offensichtlich, dass die Ramanspektren der Copolymere wesentlich komplexer sind als die der Homopolymere, wodurch die Auswertung erschwert wird. Dennoch erinnern die Ramanspektren der Copolymere an die der Homopolymere. Die spektroelektrochemischen Eigenschaften der Copolymere haben bestätigt, dass deren Charakteristika zwischen denen der Homopolymere liegen, was deutlich macht, dass die Oxidation von Monomeren möglich ist und dass die Copolymerketten demnach aus Furan- und Thiophen- bzw. 3- Chlorothiopheneinheiten bestehen können. / Electrochemical copolymerization of furan and thiophene or 3-chlorothiophene was successfully realized in a solvent system consisting of boron trifluoride ethyl ether (BFEE) + ethyl ether (EE) (ratio 1:2) at constant electrode potential. The addition of trifluoroacetic acid (TFA) (10 % by volume) to BFEE + EE (ratio 1:2) decreased the oxidation potential of the monomers; the polymerization rate was also accelerated because TFA increases the ionic conductivity of the electrolyte. The homopolymers have only one redox peak caused by polymer oxidation and reduction. Electrochemical copolymerization both at different potentials and with different thiophene or 3-chlorothiophene concentrations is investigated. The copolymers show one anodic/cathodic peak couple that appears at a position quite different from the positions observed with homopolymers. More thiophene or 3-chlorothiophene units are incorporated into the copolymer film with an increasing polymerization potential of the copolymer and/or with an increasing concentration of thiophene or 3- chlorothiophene in the feed. An electropolymerization mechanism of copolymers has been proposed, and the copolymers show a fairly good long-term stability of the redox activity after cycling in acetonitrile. In situ UV-Vis spectra of the homo- and copolymer films were measured and λ1max which corresponds to the π → π* transition is determined. The optical transition with λ2max from the valence band into the higher bipolaron band is also assigned. The band gap (Eg) for homo- and copolymer films from a direct interband transition is estimated from the absorption edge of the spectrum. The redox thermodynamics of the homo- and copolymer films suggest that one electron is removed from polymer segments containing four monomer units. The studied conducting films show a single conductivity change with a stable conductivity up to EAg/AgCl= 2 V. The conductivity of these films is almost restored when the potential shift direction is reversed. Polyfuran compared to polythiophene, has a lower conductivity and the conductivity of poly(3-chlorothiophene) is around one order of magnitude lower than that of polythiophene. The in situ conductivity properties of the copolymers are not the sum of those of the individual homopolymers. This result may eliminate the possibility that the copolymers can be considered as block copolymers. Vibrational spectra of homo- and copolymer films investigated in this study have been obtained using FTIR spectroscopy. The results indicate that α-α' coupling of radical cations has taken place in the copolymerization. This is a characteristic of α-substituted five-membered heterocyclic compounds. The electrochemical degradation mechanism of furan-thiophene copolymers is also described using the obtained spectra. The in situ resonance Raman spectroscopy of the copolymers shows spectroscopic properties intermediate between those of homopolymers. At higher polymerization potentials and at higher concentrations of thiophene or 3-chlorothiophene in the feed more thiophene or 3-chlorothiophene units are incorporated into the copolymer chains. It is obvious that the Raman spectra of the copolymers are more complex than those of homopolymers, which makes the assignment difficult. However, the in situ Raman spectra of the copolymers are reminiscent of those of the homopolymers. The spectroelectrochemical properties of the copolymers confirmed that the copolymers show intermediate characteristics between the homopolymers, implying that oxidation of monomers is possible and the copolymer chains may accordingly be composed of furan and thiophene or 3-chlorothiophene units.

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.

>Magister Scientiae - MSc / These days there are deep concerns over the environmental consequences of the rate of consumption of energy from non-renewable sources because of the accelerated increase in greenhouse effect. There is, therefore, increasing interest in research activities on renewable energy systems (e.g., supercapacitors, batteries, fuel cells and photovoltaic cells) and their materials. Supercapacitor materials have attracted much attention because of their high energy storage capacity, large surface area, high specific power density (watts/kg) and low cost. The development of advanced supercapacitor devices requires active electrode materials with high storage capacity and dispensability. Graphene oxide-dendritic star copolymer nanocomposites are fascinating as electrode materials, both scientifically and technologically, due to their exceptional properties, including light weight and high potential. / 2020-08-31

Made available in DSpace on 2014-06-11T19:29:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-28Bitstream added on 2014-06-13T20:48:16Z : No. of bitstreams: 1 pereira_par_me_sjrp.pdf: 2491155 bytes, checksum: 9deb7dfefe2de27d42938548e5d1567a (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os polímeros condutores a Base de Tiofeno-Schiff despontam como materiais alternativos para obtenção de eletrodos modificados com potencial aplicação em sensores químicos devido as excelentes propriedades condutoras e quelantes conferidas pelo poli-tiofeno e pelas Bases de Schiff, respectivamente. Neste trabalho, o complexo Tiofeno-Salen foi sintetizado e caracterizado por UV8Vis e FTIR, em seguida, monômeros complexos metálicos-tiofeno-Schiff foram sintetizados com a complexação de cátions metálicos de transição como Ni2+, Cu2+, VO2+, Fe3+, Ru3+ e Ce4+ e novamente caracterizados por UV8Vis e FTIR para comprovar a formação dos monômeros complexos metálicos-tiofeno-Schiff. Filmes poliméricos desses complexos metálicos foram obtidos pela técnica de eletropolimerização anódica e foram caracterizados eletroquimicamente por voltametria cíclica em solução aquosa. Verificou-se a influência de diversas variáveis experimentais tais como solvente, eletrólito de suporte, intervalo de varredura de potenciais, velocidade de varredura de potenciais, concentração do monômero e número de ciclos durante a etapa de eletropolimerização. Os substratos condutores utilizados na etapa de eletropolimerização foram o eletrodo de platina e o eletrodo de carbono vítreo, demonstrando a influência do substrato condutor na etapa de eletropolimerização e verificou-se que o eletrodo de platina apresentou maior eficiência de transferência eletrônica quando comparado ao eletrodo de carbono vítreo devido a natureza amorfa do carbono vítreo para esses filmes poliméricos estudados. Os eletrodos de platina modificados com esses filmes poliméricos foram também utilizados no estudo das suas propriedades eletroquímicas para a detecção de analitos de interesse analítico como L-dopa, ditionito, piridoxina, sulfito, nitrito, L-tiroxina e ácido gálico. / Conducting polymers of the Thiophene-Schiff Bases emerge as alternative materials to obtain modified electrodes with potential applications in chemical sensors due to the excellent conductive chelating properties conferred by the poly-thiophene and the Schiff Bases, respectively. In this work, the complex Thiophene-Salen was synthesized and characterized by UV-Vis and FTIR, then monomers complex metals8thiophene8Schiff were synthesized with the complexation of cations of transition metals such as Ni2+, Cu2+, VO2+, Fe3+, Ru3+ and Ce4+ and again characterized by UV-Vis and FTIR to confirm the formation of monomer-metal complexes with thiophene-Schiff. Polymer films of these complexes were obtained by anodic electropolymerization technique and were characterized electrochemically by cyclic voltammetry in aqueous solution. There was the influence of different experimental variables such as solvent, supporting electrolyte, potential scan range, potential scan rate, monomer concentration and number of cycles during the electropolymerization. The conductive substrates used in the electropolymerization were platinum electrode and a glassy carbon electrode, demonstrating the influence of the conductive substrate in the electropolymerization and was found that the platinum electrode showed a higher electron transfer efficiency when compared to the carbon electrode vitreous due to amorphous nature of glassy carbon for these polymer films studied. The platinum modified electrodes with these polymer films were also used to study their electrochemical properties for the detection of analytes of analytical interest as L-dopa, dithionite, pyridoxine, sulphite, nitrite, L-thyroxine and gallic acid presented higher apllication as chemical sensors for these analytes.

In this work was developed an electrochemical immunosensor that can detect label free specific antibody for visceral leishmaniasis using graphite electrode modified with poly(4-HPA) as a platform and DPV as electrochemical technique support. Therefore, investigations of main structural characteristics, thermal and electrochemical poly(4-HPA), obtained by electropolymerization of acid 4-HPA, were conducted using the following techniques: FTIR, UV-vis and Fluorescence. The FTIR spectra showed that the functional groups present in the monomer are preserved and that new groups are formed after electropolymerization, and the obtained polymer is 1,2,4,5-tetra-substituted, with strong evidences that these two new substituents are diphenyl ethers and ring-ring bonds, which justifies the increase in the extension of conjugation and the presence of new chromophore groups observed in UV-vis and Fluorescence studies. Thus, it was possible to discuss about the structure of poly(4-HPA), as well as propose the possible reaction mechanisms involved in its formation. These studies were of great importance in the search for a better understanding and discussion of the results. The thermal stability of the polymer, evaluated by TGA shows that the poly(4-HPA) presents a complex and heterogeneous structure and do not exhibits good thermal stability after 100 ° C. It was also investigated the growth of polymer in function of the number of potential scans. Through of this investigation it was possible obtained a profile for the increased electrochemical response of this material in relation to the time of electropolymerization, and such profile showed that the number of potential scans used in electrosynthesis is a good parameter to be used at the studies of this material. For the immunosensor development, the immobilization of the rK39 antigen, specific for visceral leishmaniasis, onto EG/poly(4-HPA) was confirmed through electrochemical studies. A electrochemical detection of IgG+ was conducted using CV and DPV techniques, using Coomassie Brilliant Blue G-250 and ruthenium hexamine II chloride as possible indicators of the formation of Antigen-Antibody complex. The Coomassie was efficient to indicate the surface modification of EG/poly(4-HPA) with rK39, however, did not show satisfactory sensitivity for IgG+, as well as selectivity for the non-complementary target (IgG-, negative control). However, the ruthenium hexamine II chloride, showed high efficiency to indicate the surface modification of EG/poly (4-HFA) with rK39 and good sensitivity for IgG+ and selectivity towards IgG-; enabling the development of the electrochemical immunosensor proposed in this work. / Neste trabalho foi desenvolvido um imunossensor eletroquímico capaz de detectar o anticorpo, livre de marcação, específico para leishmaniose visceral utilizando-se EG modificado com ácido poli(4-HFA) como plataforma e VPD como técnica eletroquímica suporte. Para isso, investigações das principais características estruturais, térmicas e eletroquímicas do ácido poli(4-HFA), obtido por eletropolimerização do ácido 4-HFA, foram conduzidas utilizando-se as técnicas FTIR, UV-vis e Fluorescência. Os espectros de FTIR mostraram que os grupos funcionais presentes no monômero são preservados e que novos grupos são formados após a eletropolimerização, e ainda, que o polímero obtido é tetra-1,2,4,5-substituído, com fortes indícios de que esses dois novos substituintes sejam éteres difenílicos e ligações anel-anel, justificando o aumento na extensão de conjugação e a presença de novos grupos cromóforos observados nos estudos de UV-vis e Fluorescência. Neste sentido, foi possível iniciar as discussões sobre a estrutura do ácido poli(4-HFA), bem como, dos possíveis mecanismos de reação envolvidos na sua formação, e estes estudos foram de grande importância na busca de uma melhor compreensão e discussão dos resultados obtidos. A estabilidade térmica do polímero, avaliada por TGA, mostrou que o ácido poli(4-HFA) apresenta estrutura heterogênea e complexa e que este não apresenta boa estabilidade térmica após 100 °C. Investigou-se também o crescimento do filme polimérico em função do número de varreduras de potencial. Com esta investigação foi possível traçar um perfil para o aumento da resposta eletroquímica desse material em função do tempo de eletropolimerização e, tal perfil, indicou que o número de varreduras potenciais utilizados na eletrossíntese é um bom parâmetro a ser empregado na condução dos estudos deste material. Para o desenvolvimento do imunossensor, a imobilização do antígeno rK39, específico para leishmaniose visceral, sob EG/poli(4-HFA) foi comprovada por meio dos estudos eletroquímicos. A detecção eletroquímica do IgG+ foi conduzida por meio das técnicas de VC e VPD utilizando Coomassie Brillant Blue G-250 e Cloreto de hexaaminrutênio II como possíveis indicadores da formação do complexo Ag-Ac. O Coomassie mostrou-se eficiente para indicar a modificação da superfície do EG/poli(4-HFA) com rK39, entretanto, não apresentou sensibilidade satisfatória para o IgG+, bem como, seletividade perante o alvo não complementar (IgG-, controle negativo). Já o Cloreto de hexaminrutênio II, além de apresentar alta eficiência para indicar a modificação da superfície do EG/poli(4-HFA) com rK39, também apresentou boa sensibilidade para o IgG+ e seletividade perante IgG-, possibilitando o desenvolvimento do imunossensor eletroquímico proposto neste trabalho. / Mestre em Química

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