Synthesis of metal oxide nanoparticles for superconducting nanocomposites and other applications

Los proceso térmicos y por microondas, se utilizan para sintetizar nanopartículas de diferentes óxidos metálicos tales como magnetita (Fe3O4) y óxido de cerio (CeO2). Mediante la modificación de los precursores Fe(R2diket)3 (R = Ph, tBu y CF3), Ce(acac)3 y Ce(OAc)3, y siguiendo la misma ruta de síntesis, es posible controlar el tamaño y la forma de los nanocristales obtenidos. La ruta general se lleva a cabo en trietilenglicol (TREG) o benzylalcohol (BnOH), debido a su alto punto de ebullición y que además puede actuar como estabilizante de las nanopartículas en disolventes polares. Las nanopartículas se han caracterizado por varias técnicas de laboratorio comunes: Alta Resolución Microscopía Electrónica de Transmisión (HR TEM), espectroscopia infrarroja (IR), Rayos X (XRPD), magnetometría tal como Superconducting Quantum Interference Device (SQUID), Resonancia Magnética Nuclear (RMN), Cromatografía de Gases-Espectroscopía de Masas (GC-MS), Espectroscopia de fotoelectrones emitidos por rayos X (XPS) y Análisis Termogravimétrico (TGA). Con todas estas técnicas, el tamaño final, la forma, la composición, la estructura cristalina, el comportamiento magnético y la interacción del ligando con la superficie de las nanopartículas han sido estudiadas y caracterizadas. Además, se demuestra la alta eficiencia de los das dos metodologías que se han optimizado para sintetizar nanopartículas de diferentes familias. Las soluciones coloidales estables obtenidas en etanol se han utilizado para generar capas superconductoras de YBa2Cu3O7-δ (YBCO) debido a que la corriente crítica se puede aumentar cuando se incrustan las nanopartículas. Finalmente, una nueva aplicación como comportamiento antioxidante en células humanas se ha llevado a cabo para el caso de las nanopartículas de CeO2 debido a sus específicas propiedades que las hacen muy interesantes en este nuevo campo.Thermal and microwave methodologies are used to synthesize different metal oxides nanoparticles such as magnetite (Fe3O4), cerium oxide (CeO2). By modifying the precursors (Fe(R2diket)3 (R= Ph, tBu and CF3), Ce(acac)3 and Ce(OAc)3), and following the same synthetic route, it is possible to control the size and shape of the nanocrystals obtained. The general route is carried out in triethylene glycol (TREG) or benzyl alcohol (BnOH) media, due to its high boiling point and, which acts also as a capping ligand of the nanoparticles, stabilizing them in polar solvents. Nanoparticles have been characterized by several common physical laboratory techniques: High Resolution Transmission Electron Microscopy (HR TEM), infrared spectroscopy (IR), X-ray Powder Diffraction (XRPD), magnetometry via Superconducting Quantum Interference Device (SQUID), Nuclear Magnetic Resonance (RMN), Gas Chromatography-Mass Spectroscopy (GC-MS), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA). With all these techniques, the final size, shape, composition, crystal structure, magnetic behaviour and capping ligand interaction have been studied, showing the high quality crystals generated. In addition, we demonstrate the high efficiency of all two one-pot methodologies that have been optimized to synthesize different families of nanoparticles. The stable colloidal solutions obtained in ethanol have been used to generate ex-situ hybrid YBa2Cu3O7-δ (YBCO) superconducting layers because the critical current can be increased when the nanoparticles are embedded. Finally, a new application as an antioxidant behaviour in human cells is tested for the case of CeO2 nanoparticles due to their specifically properties that make them really interested in this new field

Efecte dels grups substituents en la formació de nanopartícules de Fe3O4 per descomposició de complexos de Fe(III)

En aquest treball d'investigació, s'estudiaran nanopartícules magnètiques concretament nanopartícules de magnetita (Fe3O4) on a partir de diferents precursors i amb unes condicions determinades es poden variar la seva forma i la seva mida. Aquestes mides i formes diferents són molt útils a l'hora d'introduir-les dins d'una solució de precursor del material superconductor ceràmic YBa2Cu3O7-δ (YBCO) ja que es produeix un augment significatiu de la densitat de corrent crítica. El mètode sintètic utilitzat en aquests treball d'investigació, és l'anomenat descomposició tèrmica, que ens permet sintetitzar nanopartícules de magnetita amb el corresponent control de mida i de forma desitjats

Electrochemical Stability of Rhodium-Platinum Core-Shell Nanoparticles : An Identical Location Scanning Transmission Electron Microscopy Study

Rhodium-platinum core-shell nanoparticles on a carbon support (Rh@Pt/C NPs) are promising candidates as anode catalysts for polymer electrolyte membrane fuel cells. However, their electrochemical stability needs to be further explored for successful application in commercial fuel cells. Here we employ identical location scanning transmission electron microscopy to track the morphological and compositional changes of Rh@Pt/C NPs during potential cycling (10 000 cycles, 0.06-0.8 V, 0.5 HSO) down to the atomic level, which are then used for understanding the current evolution occurring during the potential cycles. Our results reveal a high stability of the Rh@Pt/C system and point toward particle detachment from the carbon support as the main degradation mechanism

Synthesis of Metal Oxide Nanoparticles for Superconducting Nanocomposites and Other Applications

Los proceso térmicos y por microondas, se utilizan para sintetizar nanopartículas de diferentes óxidos metálicos tales como magnetita (Fe3O4) y óxido de cerio (CeO2). Mediante la modificación de los precursores Fe(R2diket)3 (R = Ph, tBu y CF3), Ce(acac)3 y Ce(OAc)3, y siguiendo la misma ruta de síntesis, es posible controlar el tamaño y la forma de los nanocristales obtenidos. La ruta general se lleva a cabo en trietilenglicol (TREG) o benzylalcohol (BnOH), debido a su alto punto de ebullición y que además puede actuar como estabilizante de las nanopartículas en disolventes polares. Las nanopartículas se han caracterizado por varias técnicas de laboratorio comunes: Alta Resolución Microscopía Electrónica de Transmisión (HR TEM), espectroscopia infrarroja (IR), Rayos X (XRPD), magnetometría tal como Superconducting Quantum Interference Device (SQUID), Resonancia Magnética Nuclear (RMN), Cromatografía de Gases-Espectroscopía de Masas (GC-MS), Espectroscopia de fotoelectrones emitidos por rayos X (XPS) y Análisis Termogravimétrico (TGA). Con todas estas técnicas, el tamaño final, la forma, la composición, la estructura cristalina, el comportamiento magnético y la interacción del ligando con la superficie de las nanopartículas han sido estudiadas y caracterizadas. Además, se demuestra la alta eficiencia de los das dos metodologías que se han optimizado para sintetizar nanopartículas de diferentes familias. Las soluciones coloidales estables obtenidas en etanol se han utilizado para generar capas superconductoras de YBa2Cu3O7-δ (YBCO) debido a que la corriente crítica se puede aumentar cuando se incrustan las nanopartículas. Finalmente, una nueva aplicación como comportamiento antioxidante en células humanas se ha llevado a cabo para el caso de las nanopartículas de CeO2 debido a sus específicas propiedades que las hacen muy interesantes en este nuevo campo.Thermal and microwave methodologies are used to synthesize different metal oxides nanoparticles such as magnetite (Fe3O4), cerium oxide (CeO2). By modifying the precursors (Fe(R2diket)3 (R= Ph, tBu and CF3), Ce(acac)3 and Ce(OAc)3), and following the same synthetic route, it is possible to control the size and shape of the nanocrystals obtained. The general route is carried out in triethylene glycol (TREG) or benzyl alcohol (BnOH) media, due to its high boiling point and, which acts also as a capping ligand of the nanoparticles, stabilizing them in polar solvents. Nanoparticles have been characterized by several common physical laboratory techniques: High Resolution Transmission Electron Microscopy (HR TEM), infrared spectroscopy (IR), X-ray Powder Diffraction (XRPD), magnetometry via Superconducting Quantum Interference Device (SQUID), Nuclear Magnetic Resonance (RMN), Gas Chromatography-Mass Spectroscopy (GC-MS), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA). With all these techniques, the final size, shape, composition, crystal structure, magnetic behaviour and capping ligand interaction have been studied, showing the high quality crystals generated. In addition, we demonstrate the high efficiency of all two one-pot methodologies that have been optimized to synthesize different families of nanoparticles. The stable colloidal solutions obtained in ethanol have been used to generate ex-situ hybrid YBa2Cu3O7-δ (YBCO) superconducting layers because the critical current can be increased when the nanoparticles are embedded. Finally, a new application as an antioxidant behaviour in human cells is tested for the case of CeO2 nanoparticles due to their specifically properties that make them really interested in this new field

Efecte dels grups substituents en la formació de nanopartícules de Fe3O4 per descomposició de complexos de Fe(III)

En aquest treball d’investigació, s’estudiaran nanopartícules magnètiques concretament nanopartícules de magnetita (Fe3O4) on a partir de diferents precursors i amb unes condicions determinades es poden variar la seva forma i la seva mida. Aquestes mides i formes diferents són molt útils a l’hora d’introduir-les dins d’una solució de precursor del material superconductor ceràmic YBa2Cu3O7-δ (YBCO) ja que es produeix un augment significatiu de la densitat de corrent crítica. El mètode sintètic utilitzat en aquests treball d’investigació, és l’anomenat descomposició tèrmica, que ens permet sintetitzar nanopartícules de magnetita amb el corresponent control de mida i de forma desitjats

Controlling the Amorphous and Crystalline State of Multinary Alloy Nanoparticles in An Ionic Liquid

Controlling the amorphous or crystalline state of multinary Cr-Mn-Fe-Co-Ni alloy nanoparticles with sizes in the range between ~1.7 nm and ~4.8 nm is achieved using three processing routes. Direct current sputtering from an alloy target in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide leads to amorphous nanoparticles as observed by high-resolution transmission electron microscopy. Crystalline nanoparticles can be achieved in situ in a transmission electron microscope by exposure to an electron beam, ex situ by heating in vacuum, or directly during synthesis by using a high-power impulse magnetron sputtering process. Growth of the nanoparticles with respect to the amorphous particles was observed. Furthermore, the crystal structure can be manipulated by the processing conditions. For example, a body-centered cubic structure is formed during in situ electron beam crystallization while longer ex situ annealing induces a face-centered cubic structure

Elemental (im-)miscibility determines phase formation of multinary nanoparticles co-sputtered in ionic liquids

Non-equilibrium synthesis methods allow to alloy bulk-immiscible elements into multinary nanoparticles, which broadens the design space for new materials. Whereas sputtering onto solid substrates can combine immiscible elements into thin film solid solutions, this is not clear for sputtering of nanoparticles in ionic liquids. Thus, the suitability of sputtering in ionic liquids for producing nanoparticles of immiscible elements is investigated by co-sputtering the systems Au-Cu (miscible), Au-Ru and Cu-Ru (both immiscible), and Au-Cu-Ru on the surface of the ionic liquid 1-butyl-3-methylimidazolium bis-trifluoromethylsulfonyl)imide [Bmim][(Tf)2N]. The sputtered nanoparticles were analyzed to obtain (i) knowledge concerning the general formation process of nanoparticles when sputtering onto ionic liquid surfaces and (ii) information, if alloy nanoparticles of immiscible elements can be synthesized as well as (iii) evidence if the Hume-Rothery rules for solid solubility are valid for sputtered nanoparticles. Accompanying atomistic simulations using density-functional theory for clusters of different size and ordering confirm that the miscibility of Au-Cu and the immiscibility of Au-Ru and Cu-Ru govern the thermodynamic stability of the nanoparticles. Based on the matching experimental and theoretical results for the NP/IL-systems concerning NP stability, a formation model of multinary NPs in ILs was developed

Efecte dels grups substituents en la formació de nanopartícules de Fe3O4 per descomposició de complexos de Fe(III)

En aquest treball d'investigació, s'estudiaran nanopartícules magnètiques concretament nanopartícules de magnetita (Fe3O4) on a partir de diferents precursors i amb unes condicions determinades es poden variar la seva forma i la seva mida. Aquestes mides i formes diferents són molt útils a l'hora d'introduir-les dins d'una solució de precursor del material superconductor ceràmic YBa2Cu3O7-δ (YBCO) ja que es produeix un augment significatiu de la densitat de corrent crítica. El mètode sintètic utilitzat en aquests treball d'investigació, és l'anomenat descomposició tèrmica, que ens permet sintetitzar nanopartícules de magnetita amb el corresponent control de mida i de forma desitjats

Exploring stability of a nanoscale complex solid solution thin film by in situ\textit {in situ} heating transmission electron microscopy

Combining thin film deposition with $\textit {in situ}$ heating electron microscopy allows to understand the thermal stability of complex solid solution nanomaterials. From a CrMnFeCoNi alloy target a thin film with an average thickness of ~10 nm was directly sputtered onto a heating chip for $\textit {in situ}$ transmission electron microscopy. We investigate the growth process and the thermal stability of the alloy and compare our results with other investigations on bulk alloys or bulk-like films thicker than 100 nm. For the chosen sputtering condition and SiNx substrate, the sputter process leads to the Stranski–Krastanov growth type (i.e., islands forming on the top of a continuous layer). Directly after sputtering, we detect two different phases, namely CoNi-rich nanoscale islands and a continuous CrMnFe-rich layer. $\textit {in situ}$ annealing of the thin film up to 700°C leads to Ostwald ripening of the islands, which is enhanced in the areas irradiated by the electron beam during heating. Besides Ostwald ripening, the chemical composition of the continuous layer and the islands changed during the heating process. After annealing, the islands are still CoNi-rich, but lower amounts of Fe and Cr are observed and Mn was completely absent. The continuous layer also changed its composition. Co and Ni were removed, and the amount of Cr lowered. These results confirm that the synthesis of a CrMnFeCoNi thin film with an average thickness of ~10 nm can lead to a different morphology, chemical composition, and stability compared to thicker films (>100 nm)