Tipo
Documentos Académicos
Tipo de Documento
Tese de Doutoramento
Título
Polímeros Condutores e MonocamadasAuto-montadas na Concepção de Novas arquitecturas contendo Nanopartículas Metálicas: Preparação, Caracterização e desempenho para Electrocatálise e Biosensores.
Participantes na publicação
Virgínia Clara Teixeira Ferreira (Author)
Dep. Química e Bioquímica
Dep. Química e Bioquímica
CQB
Resumo
Homogeneously sized and shaped, gold and platinum nanoparticles (NPs) are chemically synthesized and analysed by means of UV-vis spectroscopy, XRD and TEM. The Au-NPs electrochemical characterization (under-potential deposition of lead) reveals spherical NPs with poly-oriented crystalline domains and cubic and rod-shaped particles displaying (100) and (111)+(110) facets, respectively. Enhanced electrocatalytic behaviour, towards the ascorbic acid oxidation reaction, is achieved in rod nanoparticles.\nGold surfaces modified with self-assembled alpha,omega-alkanedithiols and Au-NPs, are analysed by STM, AFM, cyclic voltammetry and QCM. The amount of attached Au-NPs is imparted by the free thiol groups distribution at the SAM/solution interface. Long chain alkanedithiols (1,10-decanedithiol) mixed SAMs are more organized, stable and display better electron transfer blocking properties than the corresponding simple dithiol monolayers.\nP(3-MeT) and PEDOT films are electrochemically synthesized on platinum. A potentiostatic electropolymerisation efficiency of 44-54% is retrieved from the EQCM data. The frequency change recorded simultaneously with redox conversion, reveals a complex process which involves the solvent; hysteresis is not observed in the Δm vs Q curves in thin polymer films (e.g., Qox. = 2.3 mC cm-2), although for thicker layers the de-doping is delayed, i.e. ions and solvent are retained due to the low density of the external layer.\nPolymer/NPs composites, formed by Metal-S interaction, are investigated by spectroscopic, microscopic, microgravimetric and electrochemical techniques. For the P(3-MeT), inactive for the hydrazine oxidation, it is shown that the composite with Pt-NPs (? = 3 nm), displays electrocatalytic response. Using PEDOT films, displaying similar electroactivity as P(3-MeT), the superior amount of immobilized NPs is due to a rougher polymer surface; the composite shows good electrocatalytic performance (280, 220 and 60 mV lower over-potentials than for PEDOT, P(3-MeT)/Pt-NPs and platinum electrode, respectively) to the substrate under study.\nThe behaviour of the Au(111) and P(3-MeT)/Pt-NPs composite surfaces, modified with thiolated oligonucleotides, as DNA biosensors, is evaluated; the conducting properties and the high surface area of the composites enable the detection of the hybridization with the complementary sequence (1.6 x 10-11 mol cm-2 ) by cyclic voltammetry and QCM.
Instituição
FACULDADE DE CIÊNCIAS DA UNIVERSIDADE DE LISBOA
Identificadores da Publicação
Keywords
SAMs
alpha-omega-alkanedithiols
poly(3-methylthiophene)
poly(3
4-ethylenedioxythiophene)
metal nanoparticles
electrocatalysis
(bio)sensors