https://uvadoc.uva.es/handle/10324/1242 Dpto. Física de la Materia Condensada, Cristalografía y Mineralogía - Artículos de revista 2026-04-04T11:14:51Z https://uvadoc.uva.es/handle/10324/82297 In this study, we present a fast and facile self-resistive heating method to fabricate copper oxide (CuO) nanowires (NWs) using copper wire substrates. The effect of growth temperature and time were investigated through both experiment and simulations. X-ray diffraction and Raman spectroscopy confirmed the successful formation of highly crystalline CuO phase. Scanning electron microscopy images demonstrated that the NWs were uniform in size and at high density, indicating an efficient synthesis process. Additional analyses were conducted to further elucidate a thermodynamic mechanism of the growth of CuO NWs. Our extensive experimental and simulation data on synthesis parameters provide a detailed view on the growth of the NWs and explain the efficient growth of aligned CuO NWs synthesized by the resistive heating method. 2026-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/81870 Surface-enhanced Raman scattering (SERS) is a powerful technique for detecting pollutants. Recent studies have shown that the sensitivity of SERS can be further improved by using appropriate light excitation before or during Raman measurements, a phenomenon known as photo-induced enhanced Raman scattering (PIERS). In this study, we developed a highly sensitive SERS substrate by fabricating a ZnO/Au thin film using radio frequency magnetron sputtering and post-annealing processes. The resulting substrate exhibited high crystallinity and high sensitivity for pollutant detection. The study found that in situ UV excitation significantly enhanced the Raman signal, up to 5.5 times more efficiently than the traditional SERS technique. The excitation process was reversible, leading to a quick recovery of the Raman intensity to its initial level when the UV excitation was turned off. This relaxation process is attributed to the recombination of electrons and holes. The investigation shows that ZnO/Au thin films was able to detect fungicide thiram with a limit of detection of 10 8 M. PIER also helps to lower the detection threshold down to 10 9 M. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/78657 Electroluminescence (EL) imaging is a widely used tool for identifying defects in the solar cells of photovoltaic (PV) modules. Traditional EL inspections require dark conditions and module disassembly, making them costly and logistically challenging. Daylight Electroluminescence (dEL) has emerged as a cost-effective alternative, enabling on-site inspections under any irradiance conditions without module dismounting and thereby reducing costs. However, EL inspections require current injection, necessitating an external power source. Solutions like bidirectional inverters have been proposed to address this challenge. This study proposes a novel self-powered dEL methodology that uses other PV strings in the plant to supply the necessary current. The method employs a switching procedure to filter ambient light and allows entire string inspection without dismounting modules or using external power. Field tests across various irradiance conditions show that the resulting images are com- parable to those obtained in controlled darkroom environments, validating the method’s effectiveness and operational advantages. 2025-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/78649 Daylight photoluminescence (dPL) has emerged in recent years as a useful tool for inspecting solar panels, allowing for theidentification of various types of defects with good spatial resolution and is now considered a useful technique for on-site quali-fication of field-deployed PV modules. The advantage of dPL is that it does not require an electrical power source, although theswitching between two states is generally necessary to filter the ambient light. Several practical solutions have been implementedto carry out this type of measurement. In this paper, we describe the method based on the fast electrical switching using anelectronic device connected to a string or substring in such a way that allows it to be switched between two states, with differentcurrents drawn from the panels. The inspection is carried out with the string in operation, which makes it easier to monitor thecondition of the panels throughout the life of the installation. The advantage of this method is being able to switch—in a veryfast and noninvasive manner—the state of the string, between the maximum power point state and a state at (or very close to)open circuit conditions, once the electrical device has been installed. A demonstrative test has been carried out on a substring ofpanels, testing the response of two different inverters, in addition to a demonstration (using a microinverter) related to inspectinga whole string. Changes in the currents drawn from the panels, the response of the inverter, the background filtering procedure,and the quality of the images obtained are discussed in detail. dPL measurements obtained using this procedure are comparedwith previous dPL measurements and with daylight electroluminescence (dEL) measurements in order to verify the informationprovided by this new procedure. 2025-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/77004 Investigation of cell wall composition is necessary to understand the interactions between fungi and the environment as it is the external layer exposed to stimuli and detected by other organisms. Pochonia chlamydosporia and Akanthomyces lecanii, two fungal species living in the soil and infecting nematodes and insects, exhibit endophytic interactions with various plant species. Determination of cell wall composition is essential to understand the mechanisms underlying these interactions. Therefore, in this study, for the first time, we assessed the relative amounts of chitin and chitosan in the cell walls of P. chlamydosporia (PC123) and A. lecanii (69NZ, 85SCT, 126KNY, and 447SAF) via Raman spectroscopy. The isolate with the highest chitosan percentage was 69NZ, followed by 85SCT, PC123, 447SAF, and 126KNY. Moreover, combination with conventional approaches for chitin and chitosan quantification yielded quantitative results for all cell wall components. Overall, these results highlight the mechanisms by which fungi exhibit chitosan resistance and avoid detection by the host plant during root colonization. 2025-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75209 Nowadays, silicon solar plants consist of hundreds of thousands of panels. The detection and characterization of solar cell defects, particularly on-site, is crucial to maintaining high productivity at the solar plant. Among the different techniques for the inspection of the solar cell defects, luminescence techniques provide very useful information about the spatial distribution of defects. Electroluminescence performed in dark conditions (nEL) is the most commonly used technique. However, daylight EL (dEL) and daylight photoluminescence (dPL) have recently attracted interest, because they present noteworthy advantages for on-site inspections. In this paper, we present a detailed characterization of both damaged mono- and multicrystalline silicon solar cells using dEL and dPL, comparing the results provided by these techniques with those obtained with high-resolution nEL and indoor PL (performed under excitation with a laser diode). Among these techniques, dEL provides reliable and reproducible results, while dPL shows more dependence on the experimental conditions, demanding additional efforts for analysis. The limited resolution obtained with the actual IR camera technologies is a limiting factor of the dEL and dPL techniques. On the other hand, they can be performed on-site, testing a very large number of panels. Therefore, we can assert that on-site dEL is well suited for massive inspection of solar plants, while more research is necessary for dPL. 2023-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75201 Pre-Roman glass craftsmanship reached its summit with the development of complex polychrome glass beads, being the Phoenician glass pendants the most exquisite and elaborate example. The uniqueness and complexity of such findings could reveal key information for the understanding of the production and trade of glass pieces at that age. However, these findings have practically never been studied from a physic-chemical perspective. In this work, a remarkable polychrome glass pendant (2nd -1st c. BC) found at the archaeological site of Pintia (Padilla de Duero, Valladolid, Spain) is studied by a multi-analytical non-destructive approach, employing X-ray tomography to understand its fabrication procedure, as well as X-ray fluorescence (XRF) and Raman spectroscopy, both employed in microscopic mode, to determine the composition of each glass employed in its fabrication. The outstanding preservation state and well-defined archaeological context of this glass pendant offered a unique opportunity to expand the understanding of pre-Roman glass pieces, while the combination of the experimental techniques employed provided the first complete and detailed study of a Phoenician glass pendant. The fabrication procedure of the pendant has been identified step-by-step, showing evidence of the use of pre-made pieces for the eyes, as well as hints of its fabrication in a secondary workshop. Moreover, the microchemical analysis of the vividly colored glasses by XRF and Raman spectroscopy revealed a composition compatible with the use of natron as fluxing agent, typical of Phoenician glass, the presence of surface alterations corresponding to carbonatation processes, as well as the nature of the employed chromophores or pigments: Mn, Cu, and Co for the blue, Fe-S for the black, CaSb2O7 and CaSb2O7 + TiO2 for two diverse white glasses, and a pyrochloric triple oxide (Pb2Sb2 − xSnxO7−x/2) and lead oxides for the yellow. Remarkably, the use of pyrochloric triple oxides as yellow pigments has scarcely been previously reported at that age. Finally, the identification by Raman spectroscopy of CaSb2O7 and the β-phase of CaSiO3, as well as the Raman spectra features of the glass matrix corresponding to the blue glass, indicated maximum firing tem- peratures below 1100 °C. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75175 The global plastic consumption, as one of the paramount concerns of our society, opens new paths of investigation in green materials. This study presents contribution to the field with the obtention of natural rubber latex foams (NRLF using egg white powder (EW) as the biostabilizing agent. The route followed to develop these samples is based on a two-step process, a previous aeration, followed by microwave dehydration. This synthesis route is greener and ecofriendlier than conventional ones due to the use of bio-based bulk materials, the utilization of microwave radiation which reduces the energy consumption in comparison with conventional heating methods, and the elimination of the vulcanization process typically used when producing latex foams. Herein, a deep study of the effect of EW on NRLF obtained at three water content levels (i.e., 40, 70, 90 phr) is carried out. The density and cellular structure parameters are measured for the formulations of liquid and solid foams to comprehend the stabilization mechanisms due to the presence of the EW and the effect of water content. It has been possible to produce open-cell natural rubber latex foams with densities as low as 53 kg m−3 and cell sizes as low as 114 μm. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75100 Electrospun polymeric membranes, crucial in industries like water treatment, biomedical engineering, and gas separation, rely on their mechanical properties, including tensile strength, elasticity, and durability, for effectiveness and longevity. Optimal mechanical properties enable those membranes to withstand pressure fluctuations, aggressive chemicals, and various usage cycles, enhancing operational efficiency and sustainability. The tunability of these properties is key to customizing membranes for specific applications. In this regard, Atomic Force Microscopy (AFM) has proven its efficacy in the nanomechanical characterization of soft materials over the past two decades. This work reviews recent literature on AFM methods to measure mechanical properties in electrospun materials, discussing their potentialities and current applications. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75099 Understanding how polymer chains are altered by confinement or physical constraints not only is a fundamental question in polymer physics but also holds significant relevance across various fields, as it can elucidate diverse properties of the macroscopic materials. This phenomenon takes places in a wide variety of nanomaterials with different geometries. In the last decade, fabricating and researching polymeric nanomaterials has raised interest as their properties can overcome those of the starting polymer. It is thought that molecular confinement could help tailor mechanical, thermal, rheological, or chemical properties. Therefore, this review aims to present an overview of the recent advancements in the study of the dynamics of polymeric chains within different polymeric nanomaterials, putting emphasis on nanoporous ones. The review includes (i) a description of diverse polymeric nanomaterials and the origin of molecular confinement and its influence on their properties, (ii) an overview of the advancements on molecular confinement and its effects on polymeric nanoporous materials, and (iii) a summary of well-stablished facts and knowledge gaps. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75098 In this study, a novel application of synchrotron X-ray nanotomography based on high-resolution full-field transmission X-ray microscopy for characterizing the structure and morphology of micrometric hollow polymeric fibers is presented. By employing postimage analysis using an open-source software such as Tomviz and ImageJ, various key parameters in fiber morphology, including diameter, wall thickness, wall thickness distribution, pore size, porosity, and surface roughness, were assessed. Electrospun polycaprolactone fibers with micrometric diameters and submicrometric features with induced porosity via gas dissolution foaming were used to this aim. The acquired synchrotron X-ray nanotomography data were analyzed using two approaches: 3D tomographic reconstruction and 2D radiographic projection-based analysis. The results of the combination of both approaches demonstrate unique capabilities of this technique, not achievable by other available techniques, allowing for a full characterization of the internal and external morphology and structure of the fibers as well as to obtain valuable qualitative insights into the overall fiber structure. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/75066 Bound states in the continuum (BICs) in all-dielectric metasurfaces enhance light–matter interaction at the nanoscale due to their infinite Q factors and strong field confinement. Among a variety of phenomena already reported, their impact on chiral light has recently attracted great interest. Here we investigate the emergence of intrinsic and extrinsic optical chirality associated with the excitation of BICs in various metasurfaces made of Si nanorod dimers on a quartz substrate, comparing three cases: parallel nanorods (neutral) and shifted and slanted dimers, with/without index-matching superstrate. We analyze both the circular dichroism (CD) of the far-field (FF) interaction and the helicity of the near-field (NF) distribution. We show that the best approach to achieve chiral response in the FF based on extrinsic chirality is to exploit quasi-BICs (q-BICs) appearing in the case of slanted nanorod dimers. By contrast, the helicity density is largely enhanced in the case of shifted dimers, as it presents intrinsic chirality, with values 2 orders of magnitude larger than those of circularly polarized plane waves. These so-called superchiral electromagnetic fields concentrated at the nanoscale within the metasurface hold promise of appealing implications in phenomena such as strong-coupling, photoluminescence emission, or other local light–matter interactions. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/73922 Safe water supply has become one of the main concerns of our society due to the intense industrial activities generating hazardous waste. Among the water pollutants, copper ions are known for potential diseases caused by accumulation of this metal. Therefore, different adsorbents have been produced for this purpose, highlighting aerogels for their effective adsorption owing to their high surface areas and porosity. Herein the synthesis of a novel silica aerogel-based composite for copper removal is described. It was produced by the sol–gel technique, synthesizing the silica aerogel into a reticulated-polyurethane foam that acted as a macrocellular skeleton, preventing a strong shrinkage of the aerogel during the ambient pressure drying. The produced aerogels and composites were characterized in terms of density, textural properties, hydrophobicity, and copper removal efficiency. Isotherm studies revealed a significantly improved adsorption capacity in comparison with the monolithic aerogel, reaching a maximum value of 46.13 mg g−1. The predominant adsorption mechanism was Langmuir- Freundlich adsorption. The adsorption kinetics were also evaluated by different models, as well as the ability to function as filtration medium. Therefore, this work provides a promising strategy for copper uptake avoiding tedious filtration steps to separate the adsorbent, thus reducing time and costs. 2024-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/73915 In the present work, the influence of the addition of graphene nanoplatelets presenting different dimensions on polyurethane–polyisocyanurate aerogel structure and properties has been studied. The obtained aerogels synthesized through a sol–gel method have been fully characterized in terms of density, porosity, specific surface area, mechanical stiffness, thermal conductivity, and speed of sound. Opacified aerogels showing high porosity (>92%) and low densities (78–98 kg/m3) have been produced, and the effect of the size and content of graphene nanoplatelets has been studied. It has been observed that formulations with less than 5 wt.% of graphene nanoplatelets larger than 2 microns can effectively reduce the total thermal conductivity by absorption and scattering of the infrared radiation, reducing the heat transfer by this mechanism. The resulting opacified samples are highly insulating materials, with thermal conductivities less than 18 mW/m·K. Moreover, it has been observed that smaller particles with ca. 200 nm of average length can promote an increase in the elastic modulus, therefore obtaining stiffer aerogels, combined with thermal conductivities lower than 20 mW/m·K. Results have been studied in detail, providing a further understanding of the mechanisms for improving the final properties of these materials, making them more suitable for industrial applications. 2025-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/73909 Silica-based aerogels have been successfully reinforced by means of reticulated polymeric polyurethane (PU) foams with different cell sizes. The resultant silica aerogel-PU foam composites (Sil-PU composites) were fully characterized (density, shrinkage, aerogel percentage, and porous structure), and the mechanical properties and thermal conductivities were analyzed. Moreover, the effect of the application of a surface modification was assessed. A clear influence of the foam pore size on the final properties was found, and the mechanical properties of the aerogels have been notably improved reaching higher elastic modulus (from 130 to 307 kPa), excellent recovery ratios (above 95%), and significant deformations (more than 70%) without breaking. Therefore, the synthesized composites showed a great elasticity (high recovery ratios), tenacity, resilience, and stiffness in comparison with the non-reinforced aerogels. The obtained samples also showed excellent insulating capacities, reaching values between 14.0 and 12.3 mW/(m·K) for the surface-modified composites that were dried under supercritical conditions. Thus, using reticulated PU foams as a skeleton for aerogels is a promising strategy for a broad spectrum of applications in which silica aerogels are suitable candidates. 2022-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/73305 Constant monitoring of manufacturing processes is crucial for ensuring high-quality products and cost-effectiveness. Non-destructive testing (NDT) techniques, such as eddy current testing (ECT), offer a direct and accurate means of evaluating weld quality in real-time. ECT can assess microstructural changes in welded materials by measuring electrical conductivity. Establishing a robust correlation between electrical conductivity and microstructural changes induced by FSW process parameters remains a critical step to bridge existing knowledge gaps. In this study, electrical conductivity field analysis using eddy currents was conducted on AA6082-T6 FSW joints. A pivotal factor controlling process heat input and influencing defect formation and weld microstructural features is the ratios of FSW tool rotational speed (ω) to travel speed (v). Previous works often evaluated only one set of process parameters, while our study examines multiple combinations of ω and welding speed v to develop a more robust correlation between electrical conductivity and microstructural changes. Both defective and defect-free joints were obtained employing various ω/v ratio and electrical conductivity results were compared with hardness measurements and tensile test results. The analysis reveals a consistent trend between electrical conductivity variations, microstructural changes in weld zones, and microhardness as the ω/ν ratio varies. Our findings show that, at a constant travel speed, an increasing ω/ν ratio is associated with enhanced microhardness and decreased electrical conductivity, attributed to grain refinement. Conversely, at a constant rotational speed, a higher ω/ν ratio leads to increased electrical conductivity, due to the enhanced dissolution of strengthening precipitates. Furthermore, analyzing electrical conductivity profiles and identifying local maxima corresponding to weld failure zones could strengthen the correlation. This approach suggests the potential to assess variations in mechanical properties resulting from process drift, specifically influenced by changes in the ω/v parameter over time. Microstructural analysis through electrical conductivity evaluation emerges as a valuable and predictive tool for assessing weld properties, with promising applications in process monitoring. 2024-01-01T00:00:00Z