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Luego del seminario del Prof. Wollyness el viernes 24/8, el programa es
como sigue:<br><br>
<div align="center"><font size=5><b>Lunes 27 de agosto - 13 hs<br><br>
</b>Aula de Seminarios INQUIMAE-DQIAQF (3º piso Pab. II) <br><br>
<br>
</font><font size=6><b>Prof. Henry S. White <br>
</font><font size=4><i>Department of Chemistry, University of
Utah</i></font><font size=6> <br>
</font><font size=4><i>315 S 1400 E, Salt Lake City, Utah, 84112
U.S.A.<br><br>
<br>
</i></font><font size=5>"ELECTROCHEMISTRY IN SYNTHETIC AND
BIOLOGICAL NANOPORES"<br><br>
<br>
</b></font></div>
Abstract:<br>
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.<br>
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.<br><br>
<br>
Henry S. White<br>
Activities & Awards<br>
Grahame Award of the Electrochemical Society, 2005<br>
ACS Analytical Division Award in Electrochemistry, 2004<br>
University of Utah, Distinguished Research Award, 2004<br>
Faraday Medal, Royal Society of Chemistry, London, 2002<br>
Reilley Award of the Society of Electroanalytical Chemistry, 2000<br>
Shell Chair of Chemical Engineering and Materials Science, University
of<br>
Minnesota, 1992<br>
Associate Editor, Journal of the American Chemical Society<br>
President, Society of Electroanalytical Chemistry, 2003-05<br>
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<br>
<div align="center"><font size=5 color="#0000FF"><b>Jueves
30</font><font size=5> de agosto - 13 hs<br><br>
</b>Aula de Seminarios INQUIMAE-DQIAQF (3º piso Pab. II) <br><br>
<br>
</font><font size=6><b>Dra. Susana I. Córdoba de Torresi <br>
</font><font size=4><i>Instituto de Quimica<br>
Universidade de São Paulo<br><br>
<br>
</i></font><font size=5>"Materiales poliméricos electroactivos
aplicados a dispositivos biomédicos"<br><br>
</b></font></div>
Abstract:<br>
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.<br><br>
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<br>
<div align="center"><font size=5><b>Viernes 31 de agosto - 11 hs<br><br>
</b>Aula de Seminarios INQUIMAE-DQIAQF (3º piso Pab. II) <br><br>
<b>DEFENSA DE TESIS<br><br>
</font><font size=6>Lic. Leonardo Lizarraga <br><br>
<br>
</font><font size=5>"Propiedades electroquimiomecánicas de polímeros
de arilaminas"<br><br>
</b></font></div>
Resumen:<br><br>
<pre>La tesis que aquí se presenta estudia los cambios de volúmenes de
films</i> 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</i> 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.
</pre>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.<br>
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.</body>
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