Electric field and solvent model for Electrochemical SERS: excited-state and enhancement tuning

Being SERS a promising technique due to it potentially combining the well-known characterization prowess of Raman with the high sensitivity arising from nanoparticle-associated enhancement, 1 understanding the mechanisms due to which SERS differs from Normal Raman is key to accomplish effective applications of this technique. Following the consensus about the theoretical background that stablishes the enhancement mechanisms in SERS, 2 and focusing on electrode potential as a variable in Electrochemical (EC) SERS, for our work we have studied Pyridine (Py) SERS spectra modelling an EC-SERS nanostructured surface through an Ag 6 cluster in different orientations, with an electric field parallel to the Ag 6 -Py axis reproducing electrode potential, as depicted in Figure 1. The objective of such model is to simulate Pyridine SERS spectra and rationalizing these results based on well-established properties, accounting for symmetry considerations, coupling terms and the influence of the solvent on the system to carry out a straightforward understanding of SERS enhancement mechanisms. Our results are able to effectively reproduce the main relative intensities of Pyridine SERS spectra, shedding light on the influence of the aforementioned properties on the calculated lineshapes and intensities.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Modelling potential dependent surface-enhanced raman scattering: electric field and charged cluster dual model

The computation of electrochemical systems is very challenging because of the many variables involved. Among them, the effect of the electrode potential is particularly complex to be introduced in atomistic models. In this work, we propose a model where the surface excess of charge has been modelled with the tetrahedral-like clusters [Ag19]+, [Ag20]0 and [Ag19]-. We then modulate the effect of other surface charges implicitly as an external electric field and correlated a calculated magnitude like the electric charge on the adsorbate with the electrode potential, a purely experimental one. This model is tested with the potential-dependent Surface-Enhanced Raman Scattering (SERS) of pyridine. Namely, we investigated the changes in the Raman shifts and relative intensities due to the potential, and evaluated the different contributions (electromagnetic, charge-transfer) to the SERS spectra. Our preliminary results nicely reproduce the experimental trends and reveal that enhancement factors up to 10 to the 7th are achieved when the charge-transfer state interact with the bright local excitations of the metal cluster

Computational approaches for the charge-transfer mechanism in surface-enhanced Raman scattering

Surface-enhanced Raman Scattering (SERS) is spectroscopic technique with strong potential for basic and applied science due to the large enhancement of the Raman signal, typically from 10^6 up to 10^{14} in the most favorable situation. This amplification is the result of several contributions, being the charge-transfer (CT) mechanism the most controversial of it due to the intrinsic properties of CT states. Specifically, the vanishing electric transition dipole moment of CT states implies that this mechanism must be active by intensity borrowing from the very bright plasmonic transitions on the metal (PL), therefore, excited state coupling must be accounted for a proper estimation of the enhancement factors. In this contribution, a survey of different computational approaches is discussed, emphasizing on the strengths and limitations of each of them. Two adiabatic methods based on simulating direct transitions on the CT states or on mixed PL-CT states are analyzed, including interstate coupling as Herzberg-Teller approximation. In addition, a full non-adiabatic approach based on diabatization procedures and nuclear wavepacket propagations with a Linear Vibronic Coupling model is also presented.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Electric field and charged cluster dual model for Potential Depdendent Surface-Enhanced Raman Spectroscopy

The computation of electrochemical systems is very challenging because of the many variables involved.1 Among them, the effect of the electrode potential is particularly complex to be introduced in atomistic models. In this work, we propose a model where the surface excess of charge has been modelled with the tetrahedral-like clusters [Ag19]+, [Ag20]0 and [Ag19]-. We then modulate the effect of other surface charges implicitly as an external electric field and correlated a calculated magnitude like the electric charge on the adsorbate with the electrode potential, a purely experimental one. This model is tested with the potential-dependent Surface-Enhanced Raman Scattering (SERS) of pyridine. Namely, we investigated the changes in the Raman shifts and relative intensities due to the potential, and evaluated the different contributions (electromagnetic, charge-transfer) to the SERS spectra. Our preliminary results nicely reproduce the experimental trends and reveal that enhancement factors up to 107 are achieved when the charge-transfer state interact with the bright local excitations of the metal cluster.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

(R,S)-Equol 7-β-D-glucuronide, but not other circulating isoflavone metabolites, modulates migration and tubulogenesis in human aortic endothelial cells targeting the VEGF pathway

Funding Information: J. A. G.-B. was supported by a Standard European Marie Curie Individual Fellowship from the European Commission. D. G.-M. was supported by a Miguel Servet contract (AES 2021; CP21/00028) funded by the Institute Carlos III and by “ERDF a way of making Europe”. This work has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 838991. This work was supported by the Ramón y Cajal grant (RyC2021-032111-I) and by the grants CNS2022-135253 and TED2021-130962B-C22 funded by the MCIN/AEI/10.13039/501100011033 and by the “European Union NextGenerationEU/PRTR” program, grants PID2022-136915NA-I00 and PID2022-136419OB-I00 funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe” by the European Union, and the grant 22030/PI/22 funded by the Programa Regional de Fomento de la Investigación Científica y Técnica (Plan de Actuación 2022) de la Fundación Séneca-Agencia de Ciencia y Tecnología de la Región de Murcia, Spain. Publisher Copyright: © 2024 The Royal Society of Chemistry.Current knowledge indicates that the consumption of isoflavone-rich foodstuffs can have a beneficial impact on cardiovascular health. To what extent these isoflavones act as the main actors of that benefit is less clear. Genistein (GEN), daidzein (DAZ), and the DAZ-derived microbial metabolite equol (Eq) exhibit antiangiogenic effects in vitro, but their low bloodstream concentrations make it difficult to rationalize the in vivo effects. Their derived phase-II metabolites (glucuronides and sulfates) are major metabolites found in plasma, but their role as antiangiogenic molecules remains unexplored. We aimed here to first assess the anti-angiogenic activities of the main circulating isoflavone metabolites (glucuronides and sulfates) and compare them with their corresponding free forms at physiological concentrations (0.1-10 μM). The effects of the conjugated vs. free forms on tubulogenesis, cell migration, and VEGF-induced signalling were investigated in primary human aortic endothelial cells (HAECs). While (R,S)-equol 7-β-d-glucuronide (Eq 7-glur) exerted dose-dependent inhibition of tubulogenesis and endothelial migration comparable to that exerted by the free forms (GEN, DAZ, and Eq), the rest of the phase-II conjugates exhibited no significant effects. The underlying molecular mechanisms were independent of the bFGF but related to the modulation of the VEGF pathway. Besides, the observed dissimilar cellular metabolism (conjugation/deconjugation) places the phase-II metabolites as precursors of the free forms; however, the question of whether this metabolism impacts their biological activity requires additional studies. These new insights suggest that isoflavones and their circulating metabolites, including Eq 7-glur, may be involved in cardiovascular health (e.g., targeting angiogenesis).publishersversionepub_ahead_of_prin

Diabatic Approach for SERS: From Quantum Dynamics to Spectra.

SERS (Surface-Enhanced Raman Spectroscopy) has established itself as an important characterization technique, owing to both its characteristically high intensities and the large amount of information it is capable of yielding; however, this high sensibility also implies intrinsic complexity when it comes to extracting valuable information from the spectra. Electrochemical SERS (EC-SERS), in which the substrate is a nanostructured electrode for which the electrode potential (Vel) can be tuned, poses further challenge given the sensibility of SERS spectra of certain molecules to Vel. This is the case for Pyridine, the most emblematic SERS molecule, for which the interaction between Charge-Transfer (CT) states and Plasmons has been proven to play a crucial. In this work, we have performed full diabatizations for systems consisting of Pyridine attached to different silver clusters, giving the possibility to readily define CT states, whose energy is tunable by an applied external field E, a microscopic analogous to Vel. Nuclear wavepacket propagations on the coupled potential energy surfaces including both local excitations of the metal and CT states were performed to retrieve Resonance Raman spectra. Our results show that the population transfer from bright metal states to CT states plays a most pivotal role when it comes to the shape and absolute intensities of EC-SERS spectra of Pyridine.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Extracellular Monomeric Tau Is Internalized by Astrocytes

Tau is a microtubule-associated protein that is expressed in neurons. However, in a group of neurodegenerative diseases named tauopathies – characterized by an increase in aggregated and/or hyperphosphorylated Tau – the protein accumulates inside other cells, such as astrocytes and microglia. Given that these glial cells do not produce Tau, its presence can be explained by internalization from the extracellular medium and consequent formation of Tau aggregates. Among internalization mechanisms, heparan sulfate proteoglycans (HSPGs) have been proposed to be responsible for fibrillary Tau uptake in various cell types. Here we studied whether monomeric Tau, which has been observed to be internalized by glial cells such as microglia, was also taken up by astrocytes. Although this Tau form was internalized from the extracellular medium by these cells, the mechanism of uptake was found to be independent of HSPGsThis study was supported by the Spanish Ministry of Economy and Competitiveness [SAF-2014-53040-P (JÁ) and BFU2016- 77885-P (FH)] and the Centro de Investigación Biomédicaen Red sobre Enfermedades Neurodegenerativas (CIBERNED, Spain) (JÁ

Linear vibronic coupling approach for surface-enhanced raman scattering: quantifying the charge-transfer enhancement mechanism

The outstanding amplification observed in surface-enhanced Raman scattering (SERS) is due to several enhancement mechanisms, and standing out among them are the plasmonic (PL) and charge-transfer (CT) mechanisms. The theoretical estimation of the enhancement factors of the CT mechanism is challenging because the excited-state coupling between bright plasmons and dark CT states must be properly introduced into the model to obtain reliable intensities. In this work, we aim at simulating electrochemical SERS spectra, considering models of pyridine on silver clusters subjected to an external electric field E⃗ that represents the effect of an electrode potential Vel. The method adopts quantum dynamical propagations of nuclear wavepackets on the coupled PL and CT states described with linear vibronic coupling models parametrized for each E⃗ through a fragment-based maximum-overlap diabatization. By presenting results at different values of E⃗, we show that indeed there is a relation between the population transferred to the CT states and the total scattered intensity. The tuning and detuning processes of the CT states with the bright PLs as a function of the electric field are in good agreement with those observed in experiments. Finally, our estimations for the CT enhancement factors predict values in the order of 105 to 106, meaning that when the CT and PL states are both in resonance with the excitation wavelength, the CT and PL enhancements are comparable, and vibrational bands whose intensity is amplified by different mechanisms can be observed together, in agreement with what was measured by typical experiments on silver electrodes.Funding for open access charge: Universidad de Málaga / CBU

The search for the perfect race: ideas on procreation, old age and eugenics

Objetivo. El presente artículo se deriva de la investigación “Dilemas éticos para la toma de decisiones en tiempos de guerra”, la cual responde a los lineamientos y metas de la línea de investigación en ‘Biopolítica’ del Doctorado en Bioética de la Universidad Militar Nueva Granada; línea de investigación que tiene como objetivos buscar e indagar sobre los dilemas éticos en la toma de decisiones en tiempos de guerra. Metodología. La metodología fue un análisis histórico interpretativo de la tendencia a buscar la raza perfecta, lo que se conoce como prácticas eugenésicas, esto se busca especialmente en tiempos de guerra, y sus consecuencias para la sociedad. Resultados y conclusiones. Dentro de los dilemas éticos en tiempos de guerra, se analizarán decisiones en el III Reich”; dentro de los dilemas éticos del principio de la vida está la eugenesia como tendencia a perfeccionar la raza a costa incluso de la eliminación de los enfermos, los viejos, los individuos con necesidades especiales mentales y físicas. Este artículo expone el tratamiento de las ideas de eugenesia en el Tercer Reich, durante la época de Adolfo Hitler en el poder.Objective. This article is derived from the “Ethical dilemmas for decision-making in wartime.” research Project which responds to the guidelines and goals of the research line in ‘Bio-politics’ from the Doctorate program in Bioethics at Universidad Militar Nueva Granada, a line of research that aims to find and investigate the ethical dilemmas for decision-making in wartime. Methodology. The methodology was an interpretative historical analysis of the tendency to search for the perfect race which is known as eugenic practices this seeks especially in wartime. Results and conclusions. Decisions taken during the thrid Reich are analyzed. Eugenics, as a tendency to perfect the race even at the cost of eliminating the sick, the elderly, the individuals with mental and physical special needs, is part of the ethical dilemmas of the beginning of life. This article discusses the treatment of the ideas of eugenics in the Third Reich during Adolf Hitler’s time in power

About the Unexpected Structure and Properties of Molecules Bonded to Metal Nanoclusters.

SERS (Surface-Enhanced Raman Scattering) is a very powerful technique to gain insight into the nature of metal-molecule hybrids on a molecular level. We show the results of combining SERS and theoretical calculations (1) to analyze the subtle electronic structure of metal-molecule (M-A) interfaces, especially to study the dependence of their structure and properties on applied electric potentials or fields. An example of this is the huge efficiency of the potential (EV) in tuning the energies (E) of metal-molecule charge transfer (CT) states. An equivalence between both quantities is expected on the basis of classical electrochemistry (G=E/EV=1 eV/V) but observed energy gains up to G=4 or 5 eV/V can be explained by combining the dependence of the CT energies (E) on the excess of charge of the metal (qeff) (see Graphical Abstract) and the capacitive enhancement located at metallic nanostructures (2). Moreover, theoretical calculations predict a dual electronic structure of the M-A surface complex in the case of charged molecules bonded to charged metals. These two types of surface states of the same hybrid system are of a very different nature and are selected by the sign of the metal charge (qeff). It is predicted that a single M-A complex can be very strongly bonded (chemisorbed) or form weak and very polarizable complexes (physisorbed) depending on the charges of both the ionic species and the surface excess of the metal which is modulated by the applied potential. These two types of complexes determine the properties of the overall system in the ground electronic state, like the behavior of the wavenumbers of the CN stretching band adsorbed on metals (3-4), as well as in excited states, like the forward and reverse metal-molecule CT states of the isonicotinate anion bonded to positive (chemisorbed, G~0 eV/V) or negative (physisorbed, high G) silver clusters (5), respectively (see Graphical Abstract).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech