201 research outputs found
Electrochemical Liquid Phase TEM in Aqueous Electrolytes for Energy Applications: the Role of Liquid Flow Configuration
Get PDFElectrochemical liquid phase transmission electron microscopy (EC-LPTEM) is an invaluable tool for investigating the structural and morphological properties of functional materials in electrochemical systems for energy transition.Despite its potential, standardized experimental protocols and a consensus on data interpretation are lacking, due to a variety of commercial and customized electrical and microfluidic configurations. Given the small size of a typical electrochemical cell used in these experiments, frequent electrolyte renewal is crucial to minimize local chemical alterations from reactions and radiolysis. This study explores the effects of modifying the flow configuration within the liquid cell under experimental conditions relevant for energy applications in aqueous-based electrolytes, revealing how changes in mass transport dynamics drastically influence the electrochemical response of the cell. Two different cell designs are compared: convection- and diffusion–governed. Ex situ and in situ comparative flow experiments show that the diffusion cell mitigates gas bubbles formation and improves removal of gaseous products. The electrodeposition of Zn nanostructures and the characterization of a Cu-based catalyst are presented as proof-of-concept experiments for energy storage and CO2 reduction reaction (CO2RR) applications, respectively. The reported findings demonstrate that controlling mass transport in the liquid cell setup is crucial to obtain reliable operando experimental electrochemical conditions
Recovery of Permittivity and Depth from Near-Field Data as a Step toward Optical Nanotomography
Get PDFThe increasing complexity of composite materials structured on the nanometer scale requires highly sensitive analytical tools for nanoscale chemical identification, ideally in three dimensions. While infrared near-field microscopy provides high chemical sensitivity and nanoscopic spatial resolution in two dimensions, the quantitative extraction of material properties of three-dimensionally structured samples has not been achieved yet. Here we introduce a method to perform rapid recovery of the thickness and permittivity of simple 3D structures, such as thin films and nanostructures from near-field measurements, and provide its first experimental demonstration. This is accomplished via a novel nonlinear invertible model of the imaging process, taking advantage of the near-field data recorded at multiple harmonics of the oscillation frequency of the near-field probe. Our work enables the quantitative nanoscale-resolved optical studies of thin films, coatings, and functionalization layers, as well as the structural analysis of multiphase materials, among others. It represents a major step toward the further goal of a general near-field tomography of samples.Fil: Govyadinov, Alexander A.. CIC nanoGUNE; EspañaFil: Mastel, Stefan. CIC nanoGUNE; EspañaFil: Golmar, Federico. CIC nanoGUNE; España. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chuvilin, Andrey. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Carney, P. Scott. University of Illinois at Urbana; Estados UnidosFil: Hillenbrand, Rainer. CIC nanoGUNE; España. Universidad del País Vasco; Españ
Thermoresponsive Nanosystems based on Gold Nanoparticles
Get PDF130 p.Esta tesis tiene como objetivo el desarrollo de nuevos materiales termoresponsivos basados ennanopartículas de oro y el correspondiente análisis en tiempo real de su autoensamblaje dinámico.Estos materiales presentan aplicaciones prometedoras en dispositivos optoelectrónicos o comomateriales autorreguladores.En primer lugar, mediante el análisis en tiempo real se pudieron describir características dinámicascomo la histéresis o las auto-oscilaciones, y se demostró cómo estas características pueden controlarsequímica y experimentalmente.Además, más adelante se seleccionó la luz como estimulo, aprovechando la eficiente conversión de luzen calor de los nanorods de oro anisotrópicos.La luz como estímulo externo permite la manipulación espacio-temporal. Aprovechando estacaracterística, se pudo demostrar el concepto de auto-oscilación, el cual puede tener una importanciasignificativa para los nanomotores alimentados por luz.Además, se demostró que el autoensamblaje puede ser controlado por un combustible químico queprovoca una reacción exotérmica y que el estado de alta energía (nanopartículas dispersas) se mantienemientras dura la reacción química. Esto demuestra que estos sistemas termoresponsivos puedenfuncionar en medios complejos.En resumen, se sintetizaron y caracterizaron nuevos nanomateriales termoresponsivos que permitieronel desarrollo de nuevas propiedades conceptuales de dichos materiales dinámicos.DIPC; CICnanoGUN
Orchestrated mass transport for quantitative liquid-phase transmission electron microscopy
No full text209 p.This doctoral thesis was realized at the frontier between Liquid-Phase Transmission Electron Microscopy (LP-TEM) and Microfluidics. It contributes to the elevation of LP-TEM to a quantitative experimental technique for the study of nanoscale dynamics in liquid environments by applying concepts established in microfluidics.A workflow combining numeric modelling and experiments was elaborated. The workflow reveals and quantifies the effect of structural elements of microfluidic LP-TEM reactors on mass transport. Moreover, the effect of flow on the radiolysis reaction network was analysed. The acquired knowledge led to the development of customized LP-TEM mixing reactors with optimized mass transport.This manuscript derives general guidelines for LP-TEM flow experiments and showcases model experiments to demonstrate the progress towards quantitative LP-TEM studies.CICnanoGUN
Thermoresponsive Nanosystems based on Gold Nanoparticles
No full text130 p.Esta tesis tiene como objetivo el desarrollo de nuevos materiales termoresponsivos basados ennanopartículas de oro y el correspondiente análisis en tiempo real de su autoensamblaje dinámico.Estos materiales presentan aplicaciones prometedoras en dispositivos optoelectrónicos o comomateriales autorreguladores.En primer lugar, mediante el análisis en tiempo real se pudieron describir características dinámicascomo la histéresis o las auto-oscilaciones, y se demostró cómo estas características pueden controlarsequímica y experimentalmente.Además, más adelante se seleccionó la luz como estimulo, aprovechando la eficiente conversión de luzen calor de los nanorods de oro anisotrópicos.La luz como estímulo externo permite la manipulación espacio-temporal. Aprovechando estacaracterística, se pudo demostrar el concepto de auto-oscilación, el cual puede tener una importanciasignificativa para los nanomotores alimentados por luz.Además, se demostró que el autoensamblaje puede ser controlado por un combustible químico queprovoca una reacción exotérmica y que el estado de alta energía (nanopartículas dispersas) se mantienemientras dura la reacción química. Esto demuestra que estos sistemas termoresponsivos puedenfuncionar en medios complejos.En resumen, se sintetizaron y caracterizaron nuevos nanomateriales termoresponsivos que permitieronel desarrollo de nuevas propiedades conceptuales de dichos materiales dinámicos.DIPC; CICnanoGUN
Room-temperature air-stable spin transport in bathocuproine-based spin valves
Get PDFOrganic semiconductors, characterized by weak spin-scattering mechanisms, are attractive materials for those spintronic applications in which the spin information needs to be retained for long times. Prototypical spin-valve devices employing organic interlayers sandwiched between ferromagnetic materials possess a figure of merit (magnetoresistance (MR)) comparable to their fully inorganic counterparts. However, these results are a matter of debate as the conductivity of the devices does not show the expected temperature dependence. Here we show spin valves with an interlayer of bathocuproine in which the transport takes place unambiguously through the organic layer and where the electron spin coherence is maintained over large distances (>60 nm) at room temperature. Additionally, the devices show excellent air stability, with MR values almost unaltered after 70 days of storage under ambient conditions, making bathocuproine an interesting material for future spintronic applications.Fil: Sun, Xiangnan. CIC nanoGUNE; EspañaFil: Gobbi, Marco. Université de Strasbourg; Francia. CIC nanoGUNE; EspañaFil: Bedoya Pinto, Amilcar. CIC nanoGUNE; EspañaFil: Txoperena, Oihana. CIC nanoGUNE; EspañaFil: Golmar, Federico. CIC nanoGUNE; España. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llopis, Roger. CIC nanoGUNE; EspañaFil: Chuvilin, Andrey. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Casanova, Félix. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Hueso, Luis E.. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; Españ
In situ monitoring of DNA-aptavalve gating function on mesoporous silica nanoparticles
No full textOzalp, Veli Cengiz/0000-0002-7659-5990; Chuvilin, Andrey/0000-0002-3712-5638; nanoGUNE, CIC/0000-0001-7874-5254Mesoporous silica nanoparticles have proved to be efficient stimuli-responsive controlled release systems for drug delivery when functionalized with nanovalves. Nucleic acid aptamers have recently been adapted to function as novel nanovalves, so-called aptavalves, with molecular-recognition capabilities and target concentration-dependent actuation in nanopore-controlled drug delivery and membrane separation systems. The working mechanism of aptavales relies on their structural rearrangement triggered by a specific target molecule. As a consequence, a controlled and concentration-dependent release of payload occurs rendering this system particularly appealing for therapeutic applications. However, straightforward monitoring techniques are necessary in order to elucidate the function of aptavalves in situ and varying experimental conditions. Here, the structure-switching mechanical movements of an ATP-responsive aptavalve on the surface of mesoporous silica are characterized in real-time and in situ using circular dichroism (CD). The experimental data obtained on the aptavalve actuation are in excellent agreement with the payload release kinetics determined by fluorescence measurements. It is shown that CD serves as a reliable real-time analysis of the function of aptalvalves, and that the results obtained obey furthermore standard controlled release models. This allows in principle to pre-determine the release rate of the modified silica particles according to particular application requirements.European Research Council through ERC Starting Grant [209842-MATRIX]This work was supported by the European Research Council through ERC Starting Grant 209842-MATRIX. T.S. would like to thank Prof. P. M. Echenique for being hosted in the Donostia International Physics Centre (DIPC)
Microstructural aspects of the transition between two regimes in orthogonal cutting of AISI 1045 steel
Get PDFIn depth understanding of tool-chip friction behavior is a significant aspect for tool wear performance in steels. In the present work attention has been paid to the strain mode of the chip section in contact with the rake surface of the tool, and its influence on the mechanics of material removal. There is a multitude of evidence for the existence of qualitatively different cutting regimes in orthogonal machining of annealed AISI-1045 steel with uncoated P15 carbide cutting tools in dry conditions at cutting speeds between 5 and 200 m/min. The evaluation of chip morphology and microstructure, and cutting and feed forces, revealed an abrupt step-like transition at a cutting speed in the range of 50–60 m/min, which was attributed to the transition from built-up edge (BUE) mode developed at low cutting speed, to the mode at which the chip slides directly over the tool surface. These qualitatively distinct mechanisms of tool-chip interaction are determined by two different microstructural effects: work hardening by severe plastic deformation and microstructural softening by dynamic recrystallization (DRX). It is argued that the onset of DRX is the reason for further instability of BUE and thus is the main cause of change of the cutting regime
In-SEM micro-machining reveals the origins of the size effect in the cutting energy
Get PDFHigh-precision metal cutting is increasingly relevant in advanced applications. Such precision normally requires a cutting feed in the micron or even sub-micron dimension scale, which raises questions about applicability of concepts developed in industrial scale machining. To address this challenge, we have developed a device to perform linear cutting with force measurement in the vacuum chamber of an electron microscope, which has been utilised to study the cutting process down to 200 nm of the feed and the tool tip radius. The machining experiments carried out in-operando in SEM have shown that the main classical deformation zones of metal cutting: primary, secondary and tertiary shear zones—were preserved even at sub-micron feeds. In-operando observations and subsequent structural analysis in FIB/SEM revealed a number of microstructural peculiarities, such as: a substantial cutting force related to the development of the primary shear zone; dependence of the ternary shear zone thickness on the underlaying grain crystal orientation. Measurement of the cutting forces at deep submicron feeds and cutting tool apex radii has been exploited to discriminate different sources for the size effect on the cutting energy (dependence of the energy on the feed and tool radius). It was observed that typical industrial values of feed and tool radius imposes a size effect determined primarily by geometrical factors, while in a sub-micrometre feed range the contribution of the strain hardening in the primary share zone becomes relevant
Models of radiolysis in liquid reactors for transmission electron microscopy
No full text165 p.Liquid-phase transmission electron microscopy has enabled direct observation of dynamic processes at the nanoscale in native conditions, driven by advances in fluidic, heating, and biasing holders and electron-transparent membranes like silicon nitride and graphene. These allow encapsulation of liquids in high vacuum environments of electron microscopes, enhancing our understanding of colloids, polymers, minerals, and viruses. However, challenges arise from electron beam-induced radiolysis, creating reactive species that may affect observations, necessitating improved understanding and mitigation. Radiolysis modeling in LP-TEM, essential for comprehending these effects, stems from nuclear research, yet faces issues of oversimplification and outdated assumptions. Modern fluidic reactor designs in liquid holders introduce complexities like convection and diffusion. This thesis advances LP-TEM by developing numerical models that integrate diffusion, convection, and kinetics, using finite element methods to simulate the radiochemical environment accurately. It validates new models, reduces computational demands, and aligns theoretical predictions with experimental data, establishing a framework for future radiolysis research and practical applications in electron microscop
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