Untitled - Materials Science Institute of Madrid - Consejo Superior de ...
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11. Moléculas orgánicas y biológicas<br />
sobre superficies<br />
El estudio <strong>de</strong> la interacción <strong>de</strong> distintas moléculas orgánicas<br />
y biomoléculas con las superficies <strong>de</strong> materiales<br />
es un tema <strong>de</strong> gran importancia en nanociencia y nanotecnología,<br />
por ejemplo en el diseño y fabricación <strong>de</strong><br />
sensores y biosensores. Nosotros preten<strong>de</strong>mos mo<strong>de</strong>lizar<br />
y compren<strong>de</strong>r estos procesos mediante el estudio<br />
<strong>de</strong> la adsorción controlada <strong>de</strong> moléculas sobre superficies.<br />
Así buscamos una <strong>de</strong>scripción estructural que nos<br />
permita <strong>de</strong>terminar la geometría y el sitio <strong>de</strong> adsorción<br />
<strong>de</strong> la molécula, y relacionar este con la modificación <strong>de</strong><br />
las propieda<strong>de</strong>s electrónicas <strong>de</strong>l material. Hasta ahora<br />
estudiábamos la adsorción molecular <strong>de</strong>ntro <strong>de</strong> equipos<br />
<strong>de</strong> vacío, recientemente hemos comenzado a estudiar<br />
la adsorción <strong>de</strong> moléculas <strong>de</strong>ntro <strong>de</strong> una solución.<br />
En concreto hemos estudiado tanto la adsorción <strong>de</strong><br />
capas <strong>de</strong> azufre como <strong>de</strong> alkanotioles sobre oro <strong>de</strong>s<strong>de</strong><br />
un ambiente líquido. Por otra parte estudiamos la<br />
inmobilización <strong>de</strong> ca<strong>de</strong>nas <strong>de</strong> DNA, con secuencia<br />
conocida, sobre Au, que presenten capacidad para<br />
reconocer DNA complementario. Las técnicas empleadas<br />
para su caracterización son <strong>de</strong> dos tipos, por una<br />
parte electroquímica mediante el voltamograma y por<br />
otra parte técnicas <strong>de</strong> análisis <strong>de</strong> superficies, como<br />
espectroscopía <strong>de</strong> fotoemisión (XPS) y microscopía<br />
túnel (STM), así como difracción <strong>de</strong> rayos X rasante o<br />
absorción <strong>de</strong> rayos X realizada in-situ, <strong>de</strong>ntro <strong>de</strong> una<br />
celda electroquímica en el sincrotrón ESRF.<br />
11. Organic and bio molecules on surfaces<br />
The study <strong>of</strong> the interaction <strong>of</strong> different organic molecules<br />
and bio-molecules with surfaces is <strong>of</strong> a great<br />
importance in nanoscience and for the <strong>de</strong>signing <strong>of</strong><br />
sensors and biosensors. Our objective is to mo<strong>de</strong>l the<br />
molecular adsorption, <strong>de</strong>sorption and reaction processes<br />
on well <strong>de</strong>fined surfaces. Our studies are forwar<strong>de</strong>d<br />
to find out the molecular structure and the electronic<br />
changes induced in the material for the presence <strong>of</strong> a<br />
molecular adsorbed layer. We have studied until now<br />
the adsorption process in vacuum environment.<br />
Recently, we have started to study the adsorption process<br />
from a solution. In particular we have studied S<br />
and alkenothiol layers on gold surfaces from a liquid<br />
environment. Furthermore, we have immobilized and<br />
characterized DNA on gold surfaces in such a way that<br />
they maintain its capability for recognizing complementary<br />
DNA. We have used for its characterization<br />
both electrochemical and surface science related techniques,<br />
as cyclic voltammetry, X-Ray photoelectron<br />
spectroscopy (XPS), scanning tunneling microscopy<br />
(STM) and surface X-Ray diffraction and absorption performed<br />
in-situ, (liquid environment) at the synchrotron<br />
facility ESRF<br />
1. C. Vericat, M. E. Vela, J. Gago and R. C. Salvarezza. Electrochimica Acta 49, 3643-3649 (2004)<br />
2. E. Casero, J.A. Martín- Gago, F. Pariente and E. Lorenzo. European BioPhysics Journal. 33, 726-731 (2004).<br />
3. C. Briones, E. Mateo-Marti, C.Gómez-Navarro, V. Parro, E. Román and J.A. Martín-Gago. Phys. Rev. Lett, 93, 208103-4 (2004)<br />
Proyectos: mat2002-395<br />
12. Nano-composites y bio-nanocomposites<br />
Se han preparado nanocomposites polímero-arcilla por<br />
el procedimiento <strong>de</strong> “polimerización intercalativa” <strong>de</strong><br />
pirrol en silicatos laminares conteniendo Fe(III) en su<br />
estructura cristalina o como catión <strong>de</strong> cambio.<br />
Mediante impedancia electroquímica, se observó que la<br />
formación <strong>de</strong> polipirrol conductor viene <strong>de</strong>terminada<br />
por la localización estructural <strong>de</strong>l hierro. Biopolímeros<br />
catiónicos (quitosano) y aniónicos (alginato, pectina,<br />
carragenanos) incorporados a sólidos laminares (HDLs,<br />
montmorillonita, hectorita) y fibrosos (sepiolita) permiten<br />
obtener bio-nanocomposites. Variando la naturaleza<br />
y proporción <strong>de</strong> biopolímero se pue<strong>de</strong> pre<strong>de</strong>terminar<br />
el tipo <strong>de</strong> carga eléctrica superficial <strong>de</strong>l material<br />
híbrido formado. Los bionanocomposites<br />
quitosano/silicato tienen propieda<strong>de</strong>s <strong>de</strong> intercambio<br />
aniónico actuando como fases activas <strong>de</strong> sensores electroquímicos.<br />
Inversamente, i-carragenano/HDL son bionanocomposites<br />
intercambiadores <strong>de</strong> cationes, mostrando<br />
actividad en el reconocimiento selectivo <strong>de</strong><br />
iones Ca 2+ . La sepiolita genera bio-nanocomposites <strong>de</strong><br />
morfología micr<strong>of</strong>ibrosa, capaces <strong>de</strong> estabilizar colorantes<br />
iónicos para su empleo en fase soportada <strong>de</strong><br />
interés para <strong>de</strong>sarrollar dispositivos ópticos.<br />
12. Nano-composites and bio-nanocomposites<br />
Polymer-clay nanocomposites were prepared by intercalative<br />
polymerization <strong>of</strong> pyrrole in layered silicates<br />
containing structural Fe(III) and/or iron <strong>de</strong>liberately<br />
incorporated as exchangeable cation. Electrochemical<br />
Impedance Spectroscopy shows that the formation <strong>of</strong><br />
conductive polypyrrole is <strong>de</strong>termined by the Fe location<br />
in the silicate structure. Cationic (chitosan) and anionic<br />
(alginate, pectine, carragenan) natural biopolymers<br />
were incorporated in layered (montmorillonite, hectorite,<br />
LDHs) and fibrous (sepiolite) inorganic solids resulting<br />
bio-nanocomposites. Surface electrical charge can<br />
be pre<strong>de</strong>termined by varying the nature and ratio <strong>of</strong> the<br />
incorporated biopolymer. Chitosan/silicates bionanocomposites<br />
show anion-exchanging properties being<br />
used as active phase <strong>of</strong> electrochemical sensors.<br />
Contrarily the i-carragenane/LDH bionanocomposites<br />
show cation-exchange properties acting as active phase<br />
<strong>of</strong> electro<strong>de</strong>s for selective recognition <strong>of</strong> Ca 2+ ions. Bionanocomposites<br />
based on sepiolite show a micr<strong>of</strong>ibrous<br />
texture showing interesting properties in the stabilization<br />
<strong>of</strong> ionic dyes for potential applications in the<br />
<strong>de</strong>velopment <strong>of</strong> optics <strong>de</strong>vices.<br />
1. Ruiz-Hitzky, E.; Aranda, P.; Serratosa, J.M., “Chapter 3. Organic/Polymeric Interactions with Clays” en Handbook <strong>of</strong> Layered <strong>Materials</strong>,<br />
Auerbach, S.M.; Carrado, K.A.; Dutta, P.K., Eds., pag. 91-154, Marcel Dekker, Nueva York 2004.<br />
2. Letaief, S.; Aranda, P.; Ruiz-Hitzky, E., Appl. Clay Sci. 28, 183-198 (2005)<br />
3. Dar<strong>de</strong>r, M.; Colilla, M.; Ruiz-Hitzky, E., Appl. Clay Sci. 28, 199-208 (2005)<br />
Proyectos: MAT2000-0096-P4-02, BTE2003-05757-C02-02, MAT2003-06003-C02-01, PTR1995-0677-OP, 07N/0070/2002<br />
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