Articles publicats en revistes (Física Aplicada)
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ArticleAnalysis of the behavior of highly focused, radially coherent Dirichlet sources(Elsevier B.V., 2024-02-15) Martínez-Herrero, Rosario; Aviñoá, Marcos; Carnicer González, ArturoWe introduce a novel class of electromagnetic light sources that exhibit radial coherence, a degree of coherence characterized by a Dirichlet kernel, and with radial or azimuthal polarization. We provide a mathematical description of the spectral irradiance, 3D degree of polarization, and electromagnetic degree of coherence for such sources when they are focused using a high numerical aperture microscope lens. Since the incident beam can be described as a modal expansion, we also consider how the number of terms affects the behavior of the field in the focal area. The formal analysis is complemented with numerical simulations. The study reveals interesting properties in the focal area, despite the focused beam is no longer radially coherent.- ArticleMethod for reducing specular reflections in Mueller matrix imaging(Optical Society of America, 2025-05-12) Pardo, Iago; Bian, Subiao; Pascual Miralles, Esther; Arteaga Barriel, OriolMueller matrix polarimetry has emerged as a powerful tool for non-destructiveoptical analysis of biological tissues and bioorganic materials, offering detailed insights intopolarization-specific properties such as diattenuation, retardance, and depolarization. However,the accurate application of Mueller matrix polarimetry in biological media is often hindered byspecular reflections, which obscure signals from deeper tissue layers and degrade the samplevisualization and the polarimetric data quality. Existing methods to minimize specular reflectionhave limitations, especially in clinical or in vivo settings where sample positioning is constrained.Here, we introduce a new approach for avoiding or reducing specular highlights without havingto reduce light intensity. By using near-cross-polarization states between the polarization stategenerator and analyzer, we demonstrate that one can obtain an enhanced visualization of tissuestructures, reduce the appearance of specular reflections, and maintain a good polarimetriccontrast.
- ArticleQBOi El Niño-Southern Oscillation experiments: teleconnections of the QBO(European Geosciences Union (EGU), 2025-11-17) Naoe, Hiroaki; García-Franco, Jorge Luis; Park, Chang Hyun; Rodrigo Sánchez, Mario; Palmeiro, Froila M.; Serva, Federico; Taguchi, Masakazu; Yoshida, Kohei; Anstey, James A.; García-Serrano, Javier, 1980-; Son, Seok Woo; Kawatani, Yoshio; Butchart, Neal; Hamilton, Kevin; Chen, Chih Chieh; Glanville, Anne; Kerzenmacher, Tobias; Lott, François; Orbe, Clara; Osprey, Scott; Park, Mijeong; Richter, Jadwiga H.; Versick, Stefan; Watanabe, ShingoThis study investigates Quasi-Biennial Oscillation (QBO) teleconnections and their modulation by the El Niño–Southern Oscillation (ENSO) using a multi-model ensemble from the Atmospheric Processes And their Role in Climate (APARC) QBO initiative (QBOi). Analyzing observed QBO–ENSO teleconnections is challenging because it is difficult to separate the respective influences of QBO and ENSO outside the QBO region due to aliasing in the historical record. To isolate these signals, simulations were conducted with annually repeating prescribed sea-surface temperatures (SSTs) representing idealized El Niño and La Niña conditions (the QBOi EN and LN experiments, respectively), and results are compared with the QBOi control experiment (CTL) under ENSO-neutral conditions. The strength of the Holton-Tan relationship between the phase of the QBO and the strength of the polar vortex seen in observations is reproduced in fewer than three models in CTL and by one model in EN. In LN, three out of nine models reproduce the observed Holton–Tan relationship, but with less than half of the observed amplitude. In the Arctic winter climate, sudden stratospheric warmings (SSWs) occur more frequently in EN than in LN; however, unlike in observations, there is no discernible difference in SSW frequency between QBO westerly (QBO-W) and QBO easterly (QBO-E) phases. The Asia-Pacific subtropical jet (APJ) shifts significantly equatorward during QBO-W compared to QBO-E in observations, but this shift is not robust across models, regardless of ENSO phases. In the tropics, the sign and spatial pattern of the QBO precipitation response vary widely across models and experiments, indicating that any potential QBO signal is strongly modulated by the prevailing ENSO phases. Overall, the QBOi models exhibit unrealistically weak QBO wind amplitudes in the lower stratosphere, which may explain the weak polar vortex and APJ responses, as well as the weak precipitation signals in the tropics. In contrast, the QBO teleconnection with the Walker circulation during boreal summer and autumn shows consistent signals in both observations and most models. Specifically, the QBO-W phase is characterized by upper-level westerly and lower-level easterly anomalies over the Indian Ocean–Maritime Continent relative to QBO-E, although the amplitude and timing of these anomalies remain model-dependent. Notably, the influence of QBO phase on the Walker circulation appears insensitive to the ENSO phase.
- ArticleMechanisms of the QBO influence on the tropical troposphere: climatological SST conditions(Wiley, 2025-11-22) Rodrigo Sánchez, Mario; García-Franco, Jorge Luis; García-Serrano, Javier, 1980-; Bladé, Ileana; Palmeiro, Froila M.The Quasi-Biennial Oscillation (QBO), the leading mode of tropical stratospheric variability, is thought to influence the tropical troposphere. Disentangling this influence from the dominant effects of El Niño-Southern Oscillation (ENSO) remains challenging. In this study, we use an atmosphere-only experiment with climatological sea surface temperature to isolate the tropospheric impact of the QBO, while a companion article examines how ENSO further affects this impact. The analysis focuses on the QBO modulation of temperature and zonal wind in the upper troposphere-lower stratosphere (UTLS) and the accompanying effects on static stability, wind shear and vorticity. Our results show that the QBO modifies deep tropical convection over the Maritime Continent region, and affects both the zonal Walker circulation and, more notably, the meridional Hadley circulation. These impacts are highly seasonal, with the strongest effects in summer and autumn. A zonal asymmetry in the vertical structure of the QBO signal and its influence on tropical circulation is identified, with anomalies descending into the upper troposphere over the Indo-Pacific region. Our results also suggest that the timing of this teleconnection is primarily associated with QBO-induced changes in static stability, which exhibit a strong correlation with precipitation and arrive first at the UTLS, followed by changes in wind shear and vorticity.
- ArticleImproving lithium-ion battery performance through patterned growth of carbon nanotubes over vertically aligned silicon nanowires(Elsevier, 2024-11-10) Farid, Ghulam; Amade Rovira, Roger; Ma, Yang; Ospina, Rogelio; Serafin, Jarosław; Chaitoglou, Stefanos; Majumdar, Shubhadeep; Poveda, Adrian; Bertrán Serra, EnricThe pursuit of high-performance electrode materials for rechargeable energy storage systems has intensified recently. In this study, we introduce a novel fabrication method that precisely covers as-grown carbon nanotubes (CNTs) atop vertically aligned silicon nanowires (SiNWs), resulting in a unique CNT@SiNW hybrid structure. This innovative approach seeks to maximize the surface area of CNTs, with the ultimate goal of significantly enhancing the cycling stability of anodes in lithium-ion (Li-ion) batteries. The resulting hybrid structure exhibits a notably higher BET (Brunauer-Emmett-Teller) surface area, quantified at 150 m2/g, surpassing the 101 m2/g surface area of CNTs on silicon (Si) wafers. Moreover, the CNT@SiNW hybrid structure exhibits a larger pore size equal to 2.34 nm, compared to the 1.87 nm pore size observed for CNTs on Si wafers. Electrochemical assessments reveal the superior lithium storage performance of the CNT@SiNW hybrid structure compared to as-prepared CNTs electrodes. These improved electrochemical properties are primarily attributed to the synergistic effects between the CNTs and SiNW arrays, as well as the increased surface area of CNTs grown on the SiNW tips. Overall, the findings of this study strongly advocate for the promising potential of the CNT@SiNW hybrid structure as anode materials for high-performance energy storage devices.
- ArticleEnhancing hydrogen evolution: Carbon nanotubes as a scaffold for Mo2C deposition via magnetron sputtering and chemical vapor deposition(Elsevier Ltd., 2024-11-04) Majumdar, Shubhadeep; Chaitoglou, Stefanos; Serafin, Jarosław; Farid, Ghulam; Ospina, Rogelio; Ma, Y.; Amade Rovira, Roger; Bertrán Serra, EnricThis study presents an innovative approach to fabricating carbon nanotubes (CNTs) through magnetron sputtering and chemical vapor deposition (CVD). These CNTs serve as a robust structural scaffold for the deposition of molybdenum, which, through thermal annealing, becomes molybdenum carbide (Mo2C), which is highly efficient for hydrogen evolution reaction (HER). Our investigation delves into the physical and chemical attributes of these electrodes, revealing insights into the functionality of Mo2C on CNTs hybrid structures. Chemical characterization confirms the exceptional performance of the electrode. Our Mo2C on CNT hybrid system showcases remarkable electrocatalytic activity, with an onset potential of 103 mV at 1 mA/cm2 and an overpotential of 176 mV at 10 mA/cm2. Further validation comes from tests revealing a Tafel slope of 95 mV/dec, affirming its superiority in facilitating HER. Unparalleled combination of low charge transfer resistance and accelerated reaction kinetics, Mo2C on CNTs hybrid structure is poised to significantly enhance HER activity.
- ArticleComprehensive analysis of MAX phase and MXene materials for advanced photocatalysis, electrocatalysis and adsorption in hydrogen evolution and storage(Elsevier, 2024-12-01) Serafin, Jarosław; Dziejarski, Bartosz; Achieng, George Oindo; Vendrell, Xavier; Chaitoglou, Stefanos; Amade Rovira, RogerOver the past twenty-five years, MAX phases and their derivatives, MXenes, have become a focal point in materials research. These compounds seamlessly blend ceramic and metallic properties, offering high thermal and electrical conductivity, mechanical strength, low density, and resistance to extreme conditions. Their versatility positions them as promising candidates for diverse applications, particularly in advanced photo-catalysis and electro-catalysis for hydrogen evolution. Furthermore, MAX phases and MXenes are potential hydrogen storage materials, with unique structures that provide ample space for efficient hydrogen gas storage and release, vital for clean energy technologies like fuel cells. This review aims to comprehensively analyze their roles in photo-catalysis, electro-catalysis, and hydrogen storage, with a focus on their layered crystal structure. MAX phases integrate superior metal and ceramic attributes, while MXenes offer tunable electronic structures that enhance catalytic performance. Continued exploration is crucial to unlock their full potential, advancing clean energy technologies and beyond.
- ArticleThe minimal chemotactic cell(American Association for the Advancement of Science, 2025-07-25) Battaglia, Giuseppe; Borges Fernandes, Barbara; Apriceno, Azzurra; Arango-Restrepo, Andrés; Almadhi, Safa; Ghosh, Subhadip; Forth, Joe; López-Alonso, Jorge Pedro; Ubarretxena-Belandia, Iban; Rubi, José Miguel; Ruiz-Perez, Lorena; Williams, IanThe movement of cells and microorganisms in response to chemical gradients (chemotaxis) has played an essential role in the evolution of many biological processes. Cellular navigation works via the holistic assembly of numerous components into machineries that transform chemical energy into locomotion. Herein we present and discuss the minimal elements required for cell-like vesicles to be chemotactic. We show that lipid vesicles can propel themselves in response to chemical gradients when only a transmembrane protein and an encapsulated enzyme are incorporated into the vesicle structure. The herein proposed model serves as a proof of concept to show that even the simplest cell-like structure can experience chemotactic navigation.
- ArticleRapid amyloid-β clearance and cognitive recovery through multivalent modulation of blood–brain barrier transport(Springer Nature, 2025-12-01) Gong, Qiyong; Tian, Xiaohe; Battaglia, Giuseppe; Chen, Junyang; Xiang, Pan; Duro-Castano, Aroa; Cai, Huawei; Guo, Bin; Liu, Xiqin; Yu, Yifan; Lui, Su; Luo, Kui; Ke, Bowen; Ruiz-Perez, LorenaThe blood‒brain barrier (BBB) is a highly selective permeability barrier that safeguards the central nervous system (CNS) from potentially harmful substances while regulating the transport of essential molecules. Its dysfunction is increasingly recognized as a pivotal factor in the pathogenesis of Alzheimer’s disease (AD), contributing to the accumulation of amyloid-β (Aβ) plaques. We present a novel therapeutic strategy that targets low-density lipoprotein receptor-related protein 1 (LRP1) on the BBB. Our design leverages the multivalent nature and precise size of LRP1-targeted polymersomes to modulate receptor-mediated transport, biasing LRP1 traf cking toward transcytosis and thereby upregulating its expression to promote ef cient Aβ removal. In AD model mice, this intervention signi cantly reduced brain Aβ levels by nearly 45% and increased plasma Aβ levels by 8-fold within 2 h, as measured by ELISA. Multiple imaging techniques con rmed the reduction in brain Aβ signals after treatment. Cognitive assessments revealed that treated AD mice exhibited signi cant improvements in spatial learning and memory, with performance levels comparable to those of wild-type mice. These cognitive bene ts persisted for up to 6 months post-treatment. This work pioneers a new paradigm in drug design, where function arises from the supramolecular nature of the nanomedicine, harnessing multivalency to elicit biological action at the membrane traf cking level. Our ndings also reaf rm the critical role of the BBB in AD pathogenesis and demonstrate that targeting the BBB can make therapeutic interventions signi cantly more effective. We establish a compelling case for BBB modulation and LRP1-mediated Aβ clearance as a transformative foundation for future AD therapies.
- ArticleThermoplasmonic Polymersome Membranes by In Situ Synthesis(American Chemical Society, 2025-04-18) Barbieri, Valentino; González Colsa, Javier; Matias, Diana; Duro-Castano, Aroa; Thapa, Anshu; Ruiz-Perez, Lorena; Albella, Pablo; Volpe, Giorgio; Battaglia, GiuseppeThermoplasmonic nanoparticles, known for releasing heat upon illumination, find diverse applications in catalysis, optics, and biomedicine. Incorporating plasmonic metals within organic vesicle membranes can lead to the formation of nanoreactors capable of regulating temperature-sensitive microscopic processes. Yet, the controlled formation of stable hybrid vesicles displaying significant thermoplasmonic properties remains challenging. This work presents the in situ synthesis of highly efficient thermoplasmonic polymer vesicles, or hybrid polymersomes, by nucleating ∼2 nm gold nanoparticles within preformed polymersome membranes. This process preserves the vesicles’ morphology, stability, and overall functionality. Despite the small size of the embedded plasmonic nanoparticles, these hybrid polymersomes can efficiently convert laser light into a notable temperature increase on a larger scale through collective heating. We develop a theoretical framework that rationalizes the structure–property relations of hybrid polymersomes and accurately predicts their collective thermoplasmonic response. Finally, we demonstrate the biomedical potential of our polymersomes by employing their photothermal properties to induce the hyperthermal death of cancer cells in vitro, an effect amplified by their superior cellular uptake. We envision that these hybrid polymersomes will evolve into a versatile platform for precise control over nanoscale chemical and biological processes through plasmonic heating, unlocking numerous opportunities across various scientific and medical contexts.
- ArticleMeteorological factors and incidence of COVID-19 during the FIRST wave of the pandemic in Catalonia (Spain): A multi-county study(Elsevier B.V., 2021-03-29) Tobias, Aurelio; Molina, Tomàs, 1963-; Rodrigo Sánchez, Mario; Saez, MarcThe transmission of coronaviruses can be affected by several factors, including the climate. Due to the rapid spread of COVID-19 and the urgent need for rapid responses to contain the pandemic, it is essential to understand the role that weather conditions on the transmission of SARS-CoV-2. We evaluate the influence of meteorological factors on the incidence of COVID-19 during the first wave of the epidemic in Catalonia. We conducted a geographical analysis at the county level to evaluate the association between mean temperature, absolute humidity, solar radiation, and the cumulative incidence of COVID-19. Next, we used a time-series design to assess the short-term effects of meteorological factors on the daily incidence of COVID-19. We found a geographical association between meteorological factors and the cumulative incidence of COVID-19, from the end of March to June 2020, and a lesser extent in the short-term on the daily incidence during the first wave of the epidemic in Spain. Our findings suggest that warm and wet climates may reduce the incidence of COVID-19 in Catalonia. However, policy makers must interpret with caution any COVID-19 risk predictions based on climate information alone.
- ArticleQuasi-Biennial Oscillation influence on tropical convection and El Niño variability(American Geophysical Union (AGU), 2025-05-26) Rodrigo Sánchez, Mario; García-Serrano, Javier, 1980-; Bladé, IleanaThe Quasi‐Biennial Oscillation (QBO) of descending zonal winds is the leading mode of tropical stratospheric variability. Numerous studies have explored its connection with the troposphere, including its sensitivity to El Niño‐Southern Oscillation (ENSO). While it is accepted that an upward ENSO impact on the QBO exists, little investigation has been devoted to the potential downward influence of the QBO. Observational and model evidence show that the QBO modulates upper‐tropospheric divergence, with reduced outflow over the Maritime Continent during the westerly phase. It can also impact the warm phase of ENSO, El Niño, characterized by a weakened Walker circulation. Results show that the westerly phase of the QBO further suppresses tropical convection in the western Pacific and thus accentuates the weakening of the Walker circulation during El Niño. These results suggest that considering the QBO state could improve El Niño prediction and projection, particularly for extreme events.
- ArticleC60 fullerene as an on-demand single photon source at room temperature(American Chemical Society, 2025-10-03) Lahoz Sanz, Raul; Lozano Martín, Lidia; Brú Cortés, Adrià; Hernández Márquez, Sergi; Duocastella, Martí; Gómez Cama, José María; Juliá-Díaz, BrunoSingle photon sources are fundamental for applications in quantum computing, secure communication, and sensing, as they enable the generation of individual photons and ensure strict control over photon number statistics. However, current single photon sources can be limited by a lack of robustness, difficulty of integration into existing optical or electronic devices, and high cost. In this study, we present the use of off-the-shelf C60 fullerene molecules embedded in polystyrene as room-temperature reliable single-photon emitters. As our results demonstrate, these molecules exhibit on-demand single-photon emission, with short fluorescence lifetimes and, consequently, high emission rates. The wide availability and ease of preparation and manipulation of fullerenes as single photon sources can pave the way for the development of practical, economic and scalable quantum photonic technologies.
- ArticleOne-pot synthesis of oxidation-sensitive supramolecular gels and vesicles(American Chemical Society, 2021-11-11) Duro-Castano, Aroa; Rodríguez-Arco, Laura; Ruiz-Perez, Lorena; De Pace, Cesare; Marchello, Gabriele; Noble-Jesus, Carlos; Battaglia, GiuseppeThe open-source article introduces a one-pot synthesis method for oxidation-sensitive supramolecular gels and vesicles, marking asignificant advancement in biodegradable and environmentally friendly nanomaterials. Investigations that use green chemistry, such as thearticle in Aportación 1 and this particular one, are highly relevant to the current framework of sustainable innovative materials, offering asustainable alternative to synthetic, non-degradable polymers. The journal website, https://pubs.acs.org/doi/10.1021/acs.biomac.1c01039?goto=articleMetrics&ref=pdf, reported that the article was viewed and downloaded 3028 times. Article Views are theCOUNTER-compliant sum of full-text article downloads across all institutions and individuals since November 2008 (both PDF and HTML).The high number of downloads indicates that the article has significantly impacted and is relevant. These metrics are regularly updated toreflect usage up to the last few days. However, The Altrimetric data is not available online for unknown reasons.
- ArticleChemotactic synthetic vesicles: Design and applications in blood-brain barrier crossing(American Association for the Advancement of Science, 2017-08-02) Azizi, Juzaili; Joseph, Adrian; Contini, Claudia; Cecchin, Denis; Nyberg, Sophie; Ruiz-Perez, Lorena; Preston, Jane; Volpe, Giorgio; Battaglia, Giuseppe; Gaitzsch, Jens; Fullstone, Gavin; Tian, XiaoheIn recent years, scientists have created artificial microscopic and nanoscopic self-propelling particles, often referred to as nano- or microswimmers, capable of mimicking biological locomotion and taxis. This active diffusion enables the engineering of complex operations that so far have not been possible at the micro- and nanoscale. One of the most promising tasks is the ability to engineer nanocarriers that can autonomously navigate within tissues and organs, accessing nearly every site of the human body guided by endogenous chemical gradients. We report a fully synthetic, organic, nanoscopic system that exhibits attractive chemotaxis driven by enzymatic conversion of glucose. We achieve this by encapsulating glucose oxidase alone or in combination with catalase into nanoscopic and biocompatible asymmetric polymer vesicles (known as polymersomes). We show that these vesicles self-propel in response to an external gradient of glucose by inducing a slip velocity on their surface, which makes them move in an extremely sensitive way toward higher-concentration regions. We finally demonstrate that the chemotactic behavior of these nanoswimmers, in combination with LRP-1 (low-density lipoprotein receptor–related protein 1) targeting, enables a fourfold increase in penetration to the brain compared to nonchemotactic systems. recent years,
- ArticleThe Land Surface Interactions with the Atmosphere over the IberianSemi-Arid Environment (LIAISE) field campaign(Elsevier B.V., 2025-06) Boone, Aaron; Bellvert, Joaquim; Best, Martin; Brooke, Jennifer K.; Canut-Rocafort, Guylaine; Udina Sistach, Mireia; et al.One of the greatest challenges facing environmental science is to better understand the impacts of predicted future changes in the terrestrial hydrological cycle. It has been recognized that human activities play a key role and must therefore be considered in future climate simulations. The representation of anthropization in land surface schemes within global earth system models is at a relatively nascent stage and must be improved for more accurate future projections of water resources. The understanding of the impact of anthropogenic processes has been hampered by the lack of consistent and extensive observations. Here, we present the Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment (LIAISE) project field campaign which brought together ground-based (surface energy budget estimated at 7 sites, 269 radio soundings made at 2 sites and multiple remote sensing instruments for profiling the lower atmosphere), airborne measurements (3 airplanes and numerous drones measuring surface and atmospheric properties) and satellite data (to derive estimates of irrigation timing, soil moisture, evapotranspiration and surface temperature) to improve our understanding of key natural and anthropogenic land processes and boundary layer feedbacks. The study area is in the Ebro basin of northeastern Spain in a hot, dry Mediterranean climate, with a sharp demarcation between a vast intensively irrigated region and a much drier rainfed zone to the east. Analysis of the observations reveal strong surface heterogeneities of evapotranspiration within the irrigated zone (differences upwards of approximately 7 mm day-1 between fields), linked to the crop type, vegetation phenology and soil moisture, all of which were modulated by irrigation. The significant surface flux differences between the irrigated and rainfed zones were found to result in strongly contrasting atmospheric boundary layer properties (between 2 supersites separated by 14 km) extending upwards through the lowest several km of the atmosphere.
- ArticleIn situ formation of magnetopolymersomes via electroporation for MRI(Nature Publishing Group, 2015-09-22) Bain, Jennifer; Ruiz-Perez, Lorena; Kennerley, Aneurin J.; Muench, Stephen; Thompson, Rebecca; Battaglia, Giuseppe; Staniland, Sarah S.As the development of diagnostic/therapeutic (and combined: theranostic) nanomedicine grows, smart drug-delivery vehicles become ever more critical. Currently therapies consist of drugs tethered to, or encapsulated within nanoparticles or vesicles. There is growing interest in functionalising them with magnetic nanoparticles (MNPs) to target the therapeutics by localising them using magnetic fields. An alternating magnetic field induces remote heating of the particles (hyperthermia) triggering drug release or cell death. Furthermore, MNPs are diagnostic MRI contrast agents. There is considerable interest in MNP embedded vehicles for nanomedicine, but their development is hindered by difficulties producing consistently monodisperse MNPs and their reliable loading into vesicles. Furthermore, it is highly advantageous to "trigger" MNP production and to tune the MNP's size and magnetic response. Here we present the first example of a tuneable, switchable magnetic delivery vehicle for nanomedical application. These are comprised of robust, tailored polymer vesicles (polymersomes) embedded with superparamagnetic magnetite MNPs (magnetopolymersomes) which show good MRI contrast (R2* = 148.8 s−1) and have a vacant core for loading of therapeutics. Critically, the magnetopolymersomes are produced by a pioneering nanoreactor method whereby electroporation triggers the in situ formation of MNPs within the vesicle membrane, offering a switchable, tuneable magnetic responsive theranostic delivery vehicle.
- ArticleResponsive brushes and gels as components of soft nanotechnology(Royal Society of Chemistry, 2004-09-14) Ryan, A.J.; Crook, C.J.; Howse, J.R.; Topham, P.; Jones, R.A.L.; Geoghegan, M.; Parnell, A.J.; Ruiz-Perez, Lorena; Martin, S.J.; Cadby, A.; Menelle, A.; Webster, J.R.P.; Gleeson, A.J.; Bras, W.Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, “grafted from” brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1 < pH < 7.0, has been used to drive periodic oscillations in volume in a pH responsive hydrogel. The gel is coupled to the reaction and changes volume by a factor of at least 6. A continuously stirred, constant volume, tank reactor was set-up on an optical microscope and the reaction pH and gel size monitored. The cyclic force generation of this system has been measured directly in a modified JKR experiment. The responsive nature of polyelectrolyte brushes, grown by surface initiated ATRP, have been characterised by scanning force microscopy, neutron reflectometry and single molecule force measurements. Triblock copolymers, based on hydrophobic end-blocks and either polyacid or polybase mid-block, have been used to produce polymer gels where the deformation of the molecules can be followed directly by SAXS and a correlation between molecular shape change and macroscopic deformation has been established. The three systems studied allow both the macroscopic and a molecular response to be investigated independently for the crosslinked gels and the brushes. The triblock copolymers demonstrate that the individual response of the polyelectrolyte molecules scale-up to give the macroscopic response of the system in an oscillating chemical reaction.
- ArticleSpin-orbit entanglement driven by the Jahn-Teller effect(Nature Publishing Group, 2024-10-08) Miñarro, Alejandro S.; Villa, Mario; Casals Montserrat, Blai; Plana-Ruiz, Sergi; Sánchez, Florencio; Gázquez, Jaume; Herranz Casabona, GervasiSpin-orbit entanglement in 4d and 5d transition metal systems can enhance electronic correlations, leading to nontrivial ground states and the emergence of exotic excitations. There is also an interest to investigate spin-orbit entanglement in 3d compounds, though this is challenging due to their smaller spin-orbit coupling. Here we demonstrate that the Jahn-Teller effect in Mn3+ reduces the energy gap between high- and low- spin-orbital states that lead to enhanced spin-orbit entanglement. Our results show a rare example of synergistic effects of Jahn-Teller and spin-orbit interactions and provide a way to entangle different degrees of freedom in d-metal oxides, which may allow paths to explore the interplay of orbital, lattice and spins in 3d correlated systems.
- ArticleFast topographic optical imaging using encoded search focal scan(Nature Publishing Group, 2024-12-01) Vilar, Narcís; Artigas, Roger; Duocastella, Martí; Carles, GuillemA central quest in optics is to rapidly extract quantitative information from a sample. Existing topographical imaging tools allow non-contact and three-dimensional measurements at the micro and nanoscales and are essential in applications including precision engineering and optical quality control. However, these techniques involve acquiring a focal stack of images, a time-consuming process that prevents measurement of moving samples. Here, we propose a method for increasing the speed of topographic imaging by orders of magnitude. Our approach involves collecting a reduced set of images, each integrated during the full focal scan, whilst the illumination is synchronously modulated during exposure. By properly designing the modulation sequence for each image, unambiguous reconstruction of the object height map is achieved using far fewer images than conventional methods. We describe the theoretical foundations of our technique, characterise its performance, and demonstrate sub-micrometric topographic imaging over 100 µm range of static and dynamic systems at rates as high as 67 topographies per second, limited by the camera frame rate. The high speed of the technique and its ease of implementation could enable a paradigm shift in optical metrology, allowing the real-time characterisation of large or rapidly moving samples.