Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas
This work is devoted to the synthesis, characterization and study of the plasmonic and catalytic properties of gold or silver metal nanoparticles and gold-silver bimetallic nanoparticles, obtained through an organometallic approach, i.e. without the need of an external reducing agent and using organ...
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Universidad de La Rioja (España)
2014
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This work is devoted to the synthesis, characterization and study of the plasmonic and catalytic properties of gold or silver metal nanoparticles and gold-silver bimetallic nanoparticles, obtained through an organometallic approach, i.e. without the need of an external reducing agent and using organometallic compounds under mild reaction conditions and short reaction times.
This study has been carried out by the use of gold(I), silver(I) and bimetallic gold(I)-silver(I) organometallic precursor complexes bearing pentafluorophenyl ligands or similar organometallic gold(I) complexes bearing also imidazolium of N-heterocyclic carbene ligands and their decomposition in the presence of different stabilizing ligands. The use of this organometallic approach has allowed us to synthesize new metal nanostructures by exerting a strict control on the size, morphology and composition of the obtained nanoparticles. Thus, bimetallic gold-silver alloy nanoparticles, ultrathin bimetallic gold-silver alloy nanowires, bimetallic core-shell silver-gold nanoprisms and carbene-stabilized ultrasmall gold nanoparticles have been obtained. Finally, we have carried out the study of the plasmonic properties of the different bimetallic nanostructures obtained and the catalytic properties of mono- and bimetallic gold-silver nanoparticles in the reduction of 4-nitrophenol.
Hence, this work is divided into five chapters:
The first chapter is focused on the synthesis and characterization of spherical bimetallic gold-silver nanoparticles constituted by an alloy of both metals and stabilized with hexadecylamine. The use of different amounts of the stabilizing agent and solvents of different boiling points such as tetrahydrofuran, toluene or mesitylene has permitted to exert an excellent control on the size and metal composition of the nanoparticles, allowing us to carry out a deep study of the plasmonic properties of the obtained nanoparticles. This work is completed with a study of the nanoparticles formation by the use of the nuclear magnetic resonance technique, which has provided interesting information about the mechanism and the molecular species involved in the formation of the nanostructures.
In the second chapter of this work the synthesis and characterization of unidimensional ultrafine bimetallic gold-silver nanostructures stabilized with oleic acid is shown. We have studied the influence of the reaction conditions on the shape of the obtained nanostructures. Thus, we have carried out the decomposition of the organometallic precursor [Au2Ag2(C6F5)4(Et2O)]n by employing different amounts of oleic acid in the presence or not of an organic solvent (tetrahidrofuran). We have also carried out a complete structural characterization of the nanostructures by using advanced transmission electron microscopy and EDX techniques. The work is completed with the study of the mechanism of formation of the nanostructures through UV-Vis absorption spectroscopy and nuclear magnetic resonance, which has allowed us to know mechanism and the molecular species involved in the formation of these bimetallic nanostructures.
In the third chapter the synthesis of bimetallic core-shell silver-gold nanostructures is described. We have carried out the decomposition of the organometallic complex [Au(C6F5)(tht)] over silver seed nanoparticles, obtained by decomposition of [Ag(C6F5)]n in the presence of hexadecylamine. This strategy of successive reactions has permitted the growth of prismatic nanostructures over the spherical silver seed nanoparticles. The use of different gold:silver molar ratios has allowed us to exert a good control on the size and the shape of the synthesized nanostructures. We have carried out the characterization of the core-shell morphology through HAADF-STEM and EDX techniques. In the same way as in the former chapters we have studied the formation of the new nanostructures by the use of UV-Vis absorption spectroscopy, transmission electron microscopy and nuclear magnetic resonance, what has provided important information about the mechanism of formation and the molecular species involved in the nanostructure formation.
The fourth chapter is focused on the synthesis and characterization of new organometallic complexes of the type [CxMIM][Au(C6F5)2], [CxMIM][Au(C6F5)Cl] y [Au(C6F5)(NHCx)] (MIM = 1-methyl-3-octylimidazolium, 1-methyl-3- dodecylimidazolium, 1-methyl-3-octadecylimidazolium where x = 8 or 18; NHC = 1- methyl-3-octylimidazolium-2-ilidene, 1-methyl-3-dodecylimidazolium-2-ilidene, 1- methyl-3-octadecylimidazolium-2-ilidene where x = 8, 12 or 18) and their use as precursors for the synthesis of ultrasmall (1-2 nm) gold nanoparticles. This type of gold complexes bear in the coordination sphere of the metal centre all the features needed for the formation and stabilization of the nanoparticles, since they display low melting points, due to the presence of long alkyl chains in the imidazolium or carbene ligands, what permits a fast change to the liquid phase at moderate temperatures and pentafluorophenyl ligands, which could give rise to a reductive elimination process under thermal conditions obtaining gold(0) atoms and decafluorobiphenyl as byproduct. We complete this work with the study of the reaction of formation of the nanoparticles and of their surface state through nuclear magnetic resonance and theoretical DFT calculations, which rely interesting information about the mechanism of formation and stabilization of the nanoparticles.
Finally, the fifth chapter of this work deals with the synthesis and characterization of silver, gold and gold-silver nanoparticles stabilized with polyvinylpyrrolidone (PVP) polymer and their deposition over inorganic substrates such as 3-aminopropyl functionalized silica or silica nanoparticles. We have used these nanomaterials as catalysts in the reduction of 4-nitrophenol to 4-aminophenol, in the presence of an excess of NaBH4. The same reaction has been catalysed using ultrasmall gold nanoparticles, described in the previous chapter, also supported on functionalized silica. The study of the reduction of 4-nitrophenol catalysed by the nanoparticles has been monitored through 1H nuclear magnetic resonance, using the PVP-stabilized nanoparticles, and through UV-Vis absorption spectroscopy in the case of silicasupported nanoparticles, studying in the latter the pseudo-first order kinetics of 4- aminophenol formation. |
| author2 |
Olmos Pérez, María Elena (Universidad de La Rioja) |
| author_facet |
Olmos Pérez, María Elena (Universidad de La Rioja) Crespo Gutiérrez, Julián |
| format |
text (thesis) |
| author |
Crespo Gutiérrez, Julián |
| spellingShingle |
Crespo Gutiérrez, Julián Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas |
| author_sort |
Crespo Gutiérrez, Julián |
| title |
Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas |
| title_short |
Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas |
| title_full |
Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas |
| title_fullStr |
Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas |
| title_full_unstemmed |
Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticas |
| title_sort |
síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: propiedades plasmónicas y catalíticas |
| publisher |
Universidad de La Rioja (España) |
| publishDate |
2014 |
| url |
https://dialnet.unirioja.es/servlet/oaites?codigo=43240 |
| work_keys_str_mv |
AT crespogutierrezjulian sintesisdenanoestruturasmetalicasdeoroyplataapartirdeprecursoresorganometalicospropiedadesplasmonicasycataliticas |
| _version_ |
1718346617054035968 |
| spelling |
oai-TES00000068542019-06-29Síntesis de nanoestruturas metálicas de oro y plata a partir de precursores organometálicos: Propiedades plasmónicas y catalíticasCrespo Gutiérrez, JuliánThis work is devoted to the synthesis, characterization and study of the plasmonic and catalytic properties of gold or silver metal nanoparticles and gold-silver bimetallic nanoparticles, obtained through an organometallic approach, i.e. without the need of an external reducing agent and using organometallic compounds under mild reaction conditions and short reaction times. This study has been carried out by the use of gold(I), silver(I) and bimetallic gold(I)-silver(I) organometallic precursor complexes bearing pentafluorophenyl ligands or similar organometallic gold(I) complexes bearing also imidazolium of N-heterocyclic carbene ligands and their decomposition in the presence of different stabilizing ligands. The use of this organometallic approach has allowed us to synthesize new metal nanostructures by exerting a strict control on the size, morphology and composition of the obtained nanoparticles. Thus, bimetallic gold-silver alloy nanoparticles, ultrathin bimetallic gold-silver alloy nanowires, bimetallic core-shell silver-gold nanoprisms and carbene-stabilized ultrasmall gold nanoparticles have been obtained. Finally, we have carried out the study of the plasmonic properties of the different bimetallic nanostructures obtained and the catalytic properties of mono- and bimetallic gold-silver nanoparticles in the reduction of 4-nitrophenol. Hence, this work is divided into five chapters: The first chapter is focused on the synthesis and characterization of spherical bimetallic gold-silver nanoparticles constituted by an alloy of both metals and stabilized with hexadecylamine. The use of different amounts of the stabilizing agent and solvents of different boiling points such as tetrahydrofuran, toluene or mesitylene has permitted to exert an excellent control on the size and metal composition of the nanoparticles, allowing us to carry out a deep study of the plasmonic properties of the obtained nanoparticles. This work is completed with a study of the nanoparticles formation by the use of the nuclear magnetic resonance technique, which has provided interesting information about the mechanism and the molecular species involved in the formation of the nanostructures. In the second chapter of this work the synthesis and characterization of unidimensional ultrafine bimetallic gold-silver nanostructures stabilized with oleic acid is shown. We have studied the influence of the reaction conditions on the shape of the obtained nanostructures. Thus, we have carried out the decomposition of the organometallic precursor [Au2Ag2(C6F5)4(Et2O)]n by employing different amounts of oleic acid in the presence or not of an organic solvent (tetrahidrofuran). We have also carried out a complete structural characterization of the nanostructures by using advanced transmission electron microscopy and EDX techniques. The work is completed with the study of the mechanism of formation of the nanostructures through UV-Vis absorption spectroscopy and nuclear magnetic resonance, which has allowed us to know mechanism and the molecular species involved in the formation of these bimetallic nanostructures. In the third chapter the synthesis of bimetallic core-shell silver-gold nanostructures is described. We have carried out the decomposition of the organometallic complex [Au(C6F5)(tht)] over silver seed nanoparticles, obtained by decomposition of [Ag(C6F5)]n in the presence of hexadecylamine. This strategy of successive reactions has permitted the growth of prismatic nanostructures over the spherical silver seed nanoparticles. The use of different gold:silver molar ratios has allowed us to exert a good control on the size and the shape of the synthesized nanostructures. We have carried out the characterization of the core-shell morphology through HAADF-STEM and EDX techniques. In the same way as in the former chapters we have studied the formation of the new nanostructures by the use of UV-Vis absorption spectroscopy, transmission electron microscopy and nuclear magnetic resonance, what has provided important information about the mechanism of formation and the molecular species involved in the nanostructure formation. The fourth chapter is focused on the synthesis and characterization of new organometallic complexes of the type [CxMIM][Au(C6F5)2], [CxMIM][Au(C6F5)Cl] y [Au(C6F5)(NHCx)] (MIM = 1-methyl-3-octylimidazolium, 1-methyl-3- dodecylimidazolium, 1-methyl-3-octadecylimidazolium where x = 8 or 18; NHC = 1- methyl-3-octylimidazolium-2-ilidene, 1-methyl-3-dodecylimidazolium-2-ilidene, 1- methyl-3-octadecylimidazolium-2-ilidene where x = 8, 12 or 18) and their use as precursors for the synthesis of ultrasmall (1-2 nm) gold nanoparticles. This type of gold complexes bear in the coordination sphere of the metal centre all the features needed for the formation and stabilization of the nanoparticles, since they display low melting points, due to the presence of long alkyl chains in the imidazolium or carbene ligands, what permits a fast change to the liquid phase at moderate temperatures and pentafluorophenyl ligands, which could give rise to a reductive elimination process under thermal conditions obtaining gold(0) atoms and decafluorobiphenyl as byproduct. We complete this work with the study of the reaction of formation of the nanoparticles and of their surface state through nuclear magnetic resonance and theoretical DFT calculations, which rely interesting information about the mechanism of formation and stabilization of the nanoparticles. Finally, the fifth chapter of this work deals with the synthesis and characterization of silver, gold and gold-silver nanoparticles stabilized with polyvinylpyrrolidone (PVP) polymer and their deposition over inorganic substrates such as 3-aminopropyl functionalized silica or silica nanoparticles. We have used these nanomaterials as catalysts in the reduction of 4-nitrophenol to 4-aminophenol, in the presence of an excess of NaBH4. The same reaction has been catalysed using ultrasmall gold nanoparticles, described in the previous chapter, also supported on functionalized silica. The study of the reduction of 4-nitrophenol catalysed by the nanoparticles has been monitored through 1H nuclear magnetic resonance, using the PVP-stabilized nanoparticles, and through UV-Vis absorption spectroscopy in the case of silicasupported nanoparticles, studying in the latter the pseudo-first order kinetics of 4- aminophenol formation.El siguiente trabajo está dedicado a la síntesis, caracterización y estudio de las propiedades plasmónicas y catalíticas de nanopartículas metálicas de oro, de plata y bimetálicas de oro-plata obtenidas a través de un método organometálico, es decir, sin necesidad de la presencia de un agente reductor externo y utilizando compuestos organometálicos, condiciones de reacción suaves y tiempos de reacción cortos. Este estudio se ha llevado a cabo mediante el empleo de complejos precursores organometálicos de oro(I), de plata(I) y bimetálicos de oro(I) y plata(I) con ligandos pentafluorofenilo, y de complejos organometálicos de oro(I) que, además, contienen ligandos imidazolio o carbeno N-heterocíclico y su posterior descomposición en presencia de diferentes agentes estabilizantes. El empleo de esta aproximación organometálica ha permitido la síntesis de nuevas nanoestructuras metálicas ejerciendo un estricto control sobre el tamaño, la morfología y la composición de las nanopartículas obtenidas. Así, se han obtenido nanopartículas bimetálicas de aleaciones oro-plata esféricas, nanohilos ultrafinos bimetálicos de aleaciones oroplata, nanoprismas bimetálicos de plata-oro con una distribución núcleo-capa de los metales y nanopartículas ultrapequeñas de oro estabilizadas con ligandos carbeno. Finalmente, se han estudiado las propiedades plasmónicas de las diferentes nanoestructuras bimetálicas obtenidas, así como las propiedades catalíticas de nanopartículas mono- y bimetálicas de oro-plata en la reducción de 4-nitrofenol. De este modo, este trabajo se divide en cinco capítulos: El primer capítulo de este trabajo está centrado en la síntesis y caracterización de nanopartículas bimetálicas esféricas de oro y plata constituidas por una aleación de ambos metales y estabilizadas con hexadecilamina. El empleo de diferentes cantidades de agente estabilizante y de disolventes de diferente punto de ebullición como tetrahidrofurano, tolueno o mesitileno ha permitido ejercer un excelente control sobre el tamaño y la composición de las nanopartículas sintetizadas, permitiéndonos llevar a cabo un estudio detallado de las propiedades plasmónicas de las nanopartículas obtenidas. Este trabajo se completa con un estudio en profundidad de la reacción de formación de las nanopartículas mediante la técnica de resonancia magnética nuclear que ha permitido conocer el mecanismo y las especies moleculares involucradas en la formación de las nanopartículas. En el segundo capítulo de esta Memoria se muestra la síntesis y caracterización de nanoestructuras bimetálicas de oro-plata unidimensionales y ultrafinas estabilizadas con ácido oleico. En este capítulo se ha estudiado la influencia de las condiciones de reacción en la forma de las nanoestructuras obtenidas. Así, se ha ensayado la descomposición del precursor organometálico [Au2Ag2(C6F5)4(Et2O)]n empleando diferentes cantidades de ácido oleico en presencia o no de disolvente orgánico (tetrahidrofurano). Se ha llevado a cabo un completo estudio de técnicas avanzadas de microscopía electrónica de transmisión y EDX para caracterizar las nanoestructuras obtenidas. Este trabajo se completa con el estudio de la reacción de formación de las nanoestructuras mediante espectroscopía de absorción UV-Vis y resonancia magnética nuclear, que han permitido conocer el mecanismo y las especies moleculares involucradas en la formación de las nanoestructuras bimetálicas. El tercer capítulo de esta Memoria aborda la síntesis de nanoestructuras bimetálicas de tipo núcleo-capa de plata-oro a través de la descomposición del complejo organometálico [Au(C6F5)(tht)] sobre nanopartículas semilla de plata obtenidas mediante la descomposición de [Ag(C6F5)]n en presencia de hexadecilamina. Esta estrategia de reacciones sucesivas ha permitido el crecimiento de nanoestructuras prismáticas sobre las nanopartículas esféricas de plata semilla. El uso de diferentes relaciones molares oro:plata ha permitido ejercer un control sobre el tamaño y la forma de las nanoestructuras sintetizadas. Se ha llevado a cabo la caracterización de la morfología núcleo-capa mediante la técnica de microscopía electrónica HAADF-STEM y la técnica EDX. Al igual que en los capítulos precedentes se ha estudiado la reacción de formación de las nuevas nanoestructuras mediante espectroscopía de absorción UVVis, microscopía de transmisión electrónica y resonancia magnética nuclear, lo que ha permitido conocer el mecanismo y las especies moleculares involucradas en la formación de las nanopartículas. El cuarto capítulo de esta Memoria se ha centrado en la síntesis y caracterización de nuevos compuestos organometálicos del tipo [CxMIM][Au(C6F5)2], [CxMIM][Au(C6F5)Cl] y [Au(C6F5)(NHCx)] (MIM = 1-metil-3-octilimidazolio, 1-metil-3- dodecilimidazolio, 1-metil-3-octadecilimidazolio para x = 8 ó 18, respectivamente; NHC = 1-metil-3-octilimidazolio-2-ilideno, 1-metil-3-dodecilimidazolio-2-ilideno, 1-metil-3- octadecilimidazolio-2-ilideno para x = 8, 12 ó 18, respectivamente) y su empleo como precursores de nanopartículas de oro ultrapequeñas (1-2 nm). Este tipo de complejos de oro presentan en la esfera de coordinación del centro metálico todas las características necesarias para la formación y estabilización de nanopartículas, ya que poseen bajos puntos de fusión debido a la presencia de ligandos imidazolio o carbeno con cadenas alquílicas largas, que permiten un rápido cambio a la fase líquida a temperaturas moderadas y ligandos pentafluorofenilo, los cuales empleando condiciones térmicas podrán dar lugar a la eliminación reductora necesaria para la obtención de átomos de oro en estado de oxidación 0 y el subproducto de reacción decafluorobifenilo. Este trabajo se completa con el estudio de la reacción de formación de las nanopartículas y del estado superficial de las mismas mediante resonancia magnética nuclear y cálculos teóricos DFT, que han revelado información interesante sobre el mecanismo de formación y de estabilización de las nanopartículas. Por último, el quinto capítulo de esta Memoria trata sobre la síntesis y caracterización de nanopartículas de plata, de oro y bimetálicas de oro-plata estabilizadas con el polímero polivinilpirrolidona (PVP) y su posterior deposición sobre sustratos inorgánicos como son sílice funcionalizada y nanopartículas de sílice funcionalizada con grupos 3-aminopropilo. Se ha llevado a cabo el estudio de la actividad catalítica de estas nanopartículas en la reacción de reducción de 4-nitrofenol a 4-aminofenol, en presencia de exceso de NaBH4. Esta misma reacción se ha estudiado empleando nanopartículas ultrapequeñas de oro, descritas en el capítulo anterior, depositadas sobre sílice funcionalizada. El estudio de la reacción de reducción de 4-nitrofenol catalizada por las nanopartículas se ha monitorizado mediante resonancia magnética nuclear de 1H, empleando las nanopartículas estabilizadas únicamente con el polímero PVP, y mediante espectroscopía de absorción UV-Vis en el caso de las nanopartículas soportadas sobre sílice, estudiándose en este último caso la cinética de pseudo-primer orden de formación de 4-aminofenol.Universidad de La Rioja (España)Olmos Pérez, María Elena (Universidad de La Rioja)Monge Oroz, Miguel (Universidad de La Rioja)2014text (thesis)application/pdfhttps://dialnet.unirioja.es/servlet/oaites?codigo=43240spaLICENCIA DE USO: Los documentos a texto completo incluidos en Dialnet son de acceso libre y propiedad de sus autores y/o editores. Por tanto, cualquier acto de reproducción, distribución, comunicación pública y/o transformación total o parcial requiere el consentimiento expreso y escrito de aquéllos. 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