[Todos] SEMINARIOS SIGUIENTES

[Fernando V. Molina]

Luego del seminario del Prof. Wollyness el 
viernes 24/8, el programa es como sigue:

Lunes 27 de agosto - 13 hs

Aula de Seminarios INQUIMAE-DQIAQF (3º piso Pab. II)


Prof. Henry S. White
Department of Chemistry, University of Utah
315 S 1400 E, Salt Lake City, Utah, 84112 U.S.A.


"ELECTROCHEMISTRY IN SYNTHETIC AND BIOLOGICAL NANOPORES"


Abstract:
Advances in molecular biology and analytical 
chemistry have led to a new class of sensors 
based on electrochemical and electrical 
measurements of molecular fluxes and ion 
conductances in pores of nanometer dimensions. In 
this presentation, the fabrication of biochemical 
sensors based on “glass nanopore electrodes” and 
“glass nanopore membranes”, will be described.
These structures are fabricated from glass and 
quartz, and contain a single conical shaped pore 
with orifice radius between 5 and 500 nm. A 
consequence of the conical shape is that the 
observable ion conductance (or redox molecule 
flux) largely reflects the magnitude of the 
solution resistance in the immediate vicinity of 
the pore orifice. This property makes the 
electrical response of the glass nanopores very 
sensitive to small numbers of chemical 
interactions between analyte molecules and the 
orifice surface. Glass nanopore electrodes and 
membranes with orifice radii as small as 5 nm 
have been chemically modified by: covalent 
attachment of receptor molecules to the glass 
surfaces; by filling the pore volume with 
polymers and hydrogels; and by deposition of 
lipid bilayers across the pore orifice. These 
chemical modifications impart selectivity and 
sensitivity (single molecule and single particle 
detection) for a diverse range of applications, 
including use as solid supports for protein ion 
channel recordings resistive pulse counting of 
particles with diameters as small as 10 nm; 
sensors for a variety of environmental stimuli 
(e.g., photons, pH); and use as a structural 
support for ion selective electrodes upon filling 
the pore with reference electrodes and permselective membranes.


Henry S. White
Activities & Awards
Grahame Award of the Electrochemical Society, 2005
ACS Analytical Division Award in Electrochemistry, 2004
University of Utah, Distinguished Research Award, 2004
Faraday Medal, Royal Society of Chemistry, London, 2002
Reilley Award of the Society of Electroanalytical Chemistry, 2000
Shell Chair of Chemical Engineering and Materials Science, University of
Minnesota, 1992
Associate Editor, Journal of the American Chemical Society
President, Society of Electroanalytical Chemistry, 2003-05
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Jueves 30 de agosto - 13 hs

Aula de Seminarios INQUIMAE-DQIAQF (3º piso Pab. II)


Dra. Susana I. Córdoba de Torresi
Instituto de Quimica
Universidade de São Paulo


"Materiales poliméricos electroactivos aplicados a dispositivos biomédicos"

Abstract:
The aim of this work is to study polymeric 
systems and nanoparticles for biosensing and 
electrochemically controlled drug release 
devices. Transition metal oxides nanoparticles 
prepared by sonochemical method and immobilized 
by different techniques, were used as mediators 
in enzymatic biosensors. On the other hand, in 
drug delivery systems, hydrogels have played a 
more expressive role than conducting polymers and 
in this work they will be used as substrates for 
electrochemical growth of different conducting 
polymers. A model for the electrochemical growth 
of poly(aniline) and poly(pyrrole) inside the 
pores of a chemically reticulated poly(acryl 
amide) matrix, is proposed based on Raman 
spectroscopy , SEM and Atomic Force Microscopy 
measurements. Safranin and pyrocatecol, were 
chosen as model molecules for electrochemically 
controlled release experiments considering that 
the change in the oxidation state of the 
conducting polymers inside the pores could 
modulate the rate in which the species is released.

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Viernes 31 de agosto - 11 hs

Aula de Seminarios INQUIMAE-DQIAQF (3º piso Pab. II)

DEFENSA DE TESIS

Lic. Leonardo Lizarraga


"Propiedades electroquimiomecánicas de polímeros de arilaminas"

Resumen:

La tesis que aquí se presenta estudia los cambios 
de volúmenes de films gruesos (~200 mm) de 
poliarilaminas (principalmente polianilina) que 
ocurren durante la conmutación redox entre los 
estados denominados leucoesmeraldina y 
esmeraldina en medio ácido fuerte. Estas 
variaciones de volumen o 
cambios  electroquimiomecánicos fueron estudiados 
por técnicas electroquímicas, por microscopía 
óptica, por espectroscopia infrarroja y por 
métodos de espectrometría de masa (técnicas de 
Pirólisis–CG/MS y UV-MALDI-TOF). Por otra parte, 
se formuló un modelo mecanoestadístico para 
entender e interpretar los cambios de volumen que 
ocurren en el proceso redox. El modelo presentó 
una buena concordancia con los resultados experimentales.
A partir de los resultados experimentales y 
teóricos, se encontró que el comportamiento 
electroquímico y electroquimiomecánico de la 
primera cupla redox en medio ácido (conmutación 
redox) puede ser satisfactoriamente descripto 
considerando dos etapas de óxido-reducción. La 
primera etapa presenta un comportamiento clásico 
nernstiano con un potencial formal definido, 
mientras que la segunda etapa requiere la 
introducción de una distribución de potenciales 
formales cuasi-Gaussiana. El estado intermedio, 
protoesmeraldina, es considerado una forma estable.
La principal contribución a los cambios de 
volumen en medio ácido fuerte durante la 
conmutación redox son los cambios 
conformacionales que se producen en la estructura 
polimérica por las variaciones de los ángulos de 
enlaces y formación de estructuras quinónicas 
cuando el polímero cambia su  estado desde el 
completamente reducido leucoesmeraldina al estado 
parcialmente oxidado esmeraldina. Las evidencias 
experimentales indican dependencia con el anión, 
con la presencia de interacciones anión-polímero 
fuertemente dependientes de la naturaleza del anión. 
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