Artículos (Química Física)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10914

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Effect of Gold Nanoparticle Aggregation on the Kinetic Aspect of AuNPs/DNA Interactions
(Austin Publishing Group, 2021-03-10) Grueso Molina, Elia María; Giráldez Pérez, Rosa María; Prado Gotor, Rafael; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla
Since successful therapy for curing cancer and others genetic diseases requires the transport of DNA into the cell by delivery vehicles, the understanding of the factors that control the complexation and condensation of the DNA is a key problem. During the last decade, researchers have developed some uses of nanoparticles-DNA systems, the majority of these studies dealing with NPs, which are covalently bound to the DNA. However, the kinetic aspect of AuNPs/DNA system by non-covalent interactions is less explored. Moreover, the role of high salt concentrations in these studies is of great interest due to the majority of nanoparticles have a great tendency to aggregate upon exposure to biological medium, significantly alter the uptake extent, rate, and mechanism of AuNPs/DNA interaction. As a contribution to this field, we have studied kinetics aspects of the binding of small tiopronin gold nanoparticles, AuNPs, to double stranded DNA in at high salt concentration by using the stopped-flow technique. The kinetic curves are biexponential and reveal the presence of two kinetic steps. Moreover, AFM studies reveal AuNPs aggregation in the presence of high salt content, while the same particle are well-dispersed in water. A two-step series mechanism reaction scheme was proposed. According to the reaction scheme, the formation of an intermediate complex formed by aggregated gold nanoparticles and DNA precedes the rate-determining step of the reaction.
Properties of polyplexes formed between a cationic polymer derived from l-arabinitol and nucleic acids
(Royal Society of Chemistry, 2021-05-14) Pérez Alfonso, David; López López, Manuel; López-Cornejo, María del Pilar; Romero Azogil, Lucía; Benito Hernández, Elena María; García Martín, María de Gracia; García Calderón, Clara Beatriz; Valle Rosado, Iván; Romero Balestra, Fernando; Huertas Sánchez, Pablo; García Calderón, Margarita; Moyá Morán, María Luisa; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Universidad de Sevilla. Departamento de Química Orgánica y Farmacéutica; Universidad de Sevilla. Departamento de Genética; Junta de Andalucía; Universidad de Sevilla; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE)
In this work a sugar-based cationic polymer derived from L-arabinitol, PUArab, was prepared and its interactions with the linear calf thymus DNA and with the circular plasmid pEGFP-C1 were investigated at different N/P ratios. The polyplexes were characterized by using several techniques. For both nucleic acids, a charge inversion was observed, together with a conformational change from a coiled structure to a more compacted one. However, the N/P ratio required to observe the DNA condensation depended on the nucleic acid architecture. PUArab presents low toxicity in several cell lines. The transfection efficiency, TE, of the PUArab/pEGFP-C1 polyplexes was investigated at several N/P ratios in order to study their potential as vectors in gene transfection.
Phosphorylation of cytochrome c at tyrosine 48 finely regulates its binding to the histone chaperone SET/TAF-Iβ in the nucleus
(Wiley, 2024-11-16) Tamargo Azpilicueta, Joaquín; Casado Combreras, Miguel Ángel; Giner Arroyo, Rafael Luis; Velázquez Campoy, Adrián; Márquez Escudero, Inmaculada; Olloqui Sariego, José Luis; Rosa Acosta, Miguel Ángel de la; Díaz Moreno, Irene; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE); Junta de Andalucía
Post-translational modifications (PTMs) of proteins are ubiquitous processes present in all life kingdoms, involved in the regulation of protein stability, subcellular location and activity. In this context, cytochrome c (Cc) is an excellent case study to analyze the structural and functional changes induced by PTMS as Cc is a small, moonlighting protein playing different roles in different cell compartments at different cell-cycle stages. Cc is actually a key component of the mitochondrial electron transport chain (ETC) under homeostatic conditions but is translocated to the cytoplasm and even the nucleus under apoptotic conditions and/or DNA damage. Phosphorylation does specifically alter the Cc redox activity in the mitochondria and the Cc non-redox interaction with apoptosis-related targets in the cytoplasm. However, little is known on how phosphorylation alters the interaction of Cc with histone chaperones in the nucleus. Here, we report the effect of Cc Tyr48 phosphorylation by examining the protein interaction with SET/TAF-Iβ in the nuclear compartment using a combination of molecular dynamics simulations, biophysical and structural approaches such as isothermal titration calorimetry (ITC) and nuclear magnetic resonance (NMR) and in cell proximity ligation assays. From these experiments, we infer that Tyr48 phosphorylation allows a fine-tuning of the Cc-mediated inhibition of SET/TAF-Iβ histone chaperone activity in vitro. Our findings likewise reveal that phosphorylation impacts the nuclear, stress-responsive functions of Cc, and provide an experimental framework to explore novel aspects of Cc post-translational regulation in the nucleus.
Mechanisms for the Spin-State Switching of Strapped Ni-Porphyrin Complexes Deposited on Metal Surfaces: Insights from Quantum Chemical Calculations
(John Wiley & Sons, 2024-11-06) Montenegro-Pohlhammer, Nicolas; Sánchez de Armas, María Rocío; Gruber, Manuel; Jiménez Calzado, Carmen; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Deutsche Forschungsgemeinschaft / German Research Foundation (DFG)
The incorporation of molecular switches on nanodevices requires both the intactness of the molecule once deposited on a substrate and the persistence of the reversible switching feature. Recently, the reversible spin-switching of strapped Ni(II)-porphyrin complexes deposited on Ag(111) surface is demonstrated with low-temperature scanning tunneling microscopy (STM). The spin transition is accompanied by the coordination change of the metal center, a phenomenon denominated in coordination-induced spin-state switching (CISSS). In this contribution, the spin switching of the deposited strapped Ni-porphyrin molecules using different quantum chemistry approaches is explored. This calculations inform about the geometry and electronic structure of the adsorbed molecules and the origin of the voltage-dependent switching promoted by the STM tip. Two different mechanisms are inspected to elucidate the key role of the tip, mainly the electron injection between the tip and the molecule and the differential stabilization of the two spin states by the applied electric field between the tip and the silver surface. This study puts in evidence the relevance of the pyridine ligand contained in the strap in the transport properties as in the CISSS process itself.
The HIV-1 reservoir landscape in persistent elite controllers and transient elite controllers
(American Society for Clinical Investigation, 2024-04-15) Gasca-Capote, Carmen; Lian, Xiaodong; Gao, Ce; Roseto, Isabelle C.; Jiménez León, María Reyes; Gladkov, Gregory; Camacho Sojo, María Inés; Pérez Gómez, Alberto; Gallego, Isabel; López-Cortes, Luis Eduardo; Bachiller, Sara; Rafii-El-Idrissi Benhnia, Mohammed; Ostos Marcos, Francisco José; López Cortés, Luis Fernando; Ruiz-Mateos, Ezequiel; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Médica y Biología Molecular e Inmunología; Universidad de Sevilla. Departamento de Medicina; Instituto de Salud Carlos III; Junta de Andalucía; National Institutes of Health. United States; Bill and Melinda Gates Foundation
BACKGROUND. Persistent controllers (PCs) maintain antiretroviral-free HIV-1 control indefinitely over time, while transient controllers (TCs) eventually lose virological control. It is essential to characterize the quality of the HIV reservoir in terms of these phenotypes in order to identify the factors that lead to HIV progression and to open new avenues toward an HIV cure. METHODS. The characterization of HIV-1 reservoir from peripheral blood mononuclear cells was performed using next-generation sequencing techniques, such as full-length individual and matched integration site proviral sequencing (FLIP-Seq; MIP-Seq). RESULTS. PCs and TCs, before losing virological control, presented significantly lower total, intact, and defective proviruses compared with those of participants on antiretroviral therapy (ART). No differences were found in total and defective proviruses between PCs and TCs. However, intact provirus levels were lower in PCs compared with TCs; indeed the intact/ defective HIV-DNA ratio was significantly higher in TCs. Clonally expanded intact proviruses were found only in PCs and located in centromeric satellite DNA or zinc-finger genes, both associated with heterochromatin features. In contrast, sampled intact proviruses were located in permissive genic euchromatic positions in TCs. CONCLUSIONS. These results suggest the need for, and can give guidance to, the design of future research to identify a distinct proviral landscape that may be associated with the persistent control of HIV-1 without ART.
Design Principles Guided by DFT Calculations and High-Throughput Frameworks for the Discovery of New Diamond-like Chalcogenide Thermoelectric Materials
(American Chemical Society, 2024-06-05) Rosado-Miranda, Adolfo E.; Posligua, Víctor; Fernández Sanz, Javier; Márquez Cruz, Antonio Marcial; Nath, Pinku; Plata Ramos, José Javier; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Red Española de Supercomputación (RES)
Biocompatible metal-organic frameworks as promising platforms to eradicate HIV reservoirs ex vivo in people living with HIV
(Royal Society of Chemistry, 2024-04-17) Lebrón Romero, José Antonio; Ostos Marcos, Francisco José; Martínez-Santa, Marta; García-Moscoso, Francisco; López-López, Manuel; Moyá Morán, María Luisa; Bernal Pérez, Eva; Bachiller, Sara; González-Ulloa, Gabriel; Rodríguez Lucena, David; Lopes-Costa, Tania; Fernández Torres, Rut; Ruiz-Mateos, Ezequiel; Pedrosa, José María; Rafii-El-Idrissi Benhnia, Mohammed; López-Cornejo, María del Pilar; Universidad de Sevilla. Departamento de Química Analítica; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Química orgánica; Universidad de Sevilla. Departamento de Bioquímica Médica y Biología Molecular e Inmunología; Junta de Andalucía; Universidad de Sevilla; Ministerio de Ciencia e Innovación (MICIN). España
The HIV attacks the immune system provoking an infection that is considered a global health challenge. Despite antiretroviral treatments being effective in reducing the plasma viral load in the blood to undetectable levels in people living with HIV (PLWH), the disease is not cured and has become chronic. This happens because of the existence of anatomical and cellular viral reservoirs, mainly located in the lymph nodes and gastrointestinal tract, which are composed of infected CD4+ T cells with a resting memory phenotype and inaccessible to antiretroviral therapy. Herein, a new therapeutic strategy based on nanotechnology is presented. Different combinations of antiretroviral drugs (bictegravir/tenofovir/emtricitabine and nevirapine/tenofovir/emtricitabine) and toll-like receptor agonists were encapsulated into metal-organic frameworks (MOFs) PCN-224 and ZIF-8. The encapsulation efficiencies of all the drugs, as well as their release rate from the carriers, were measured. In vitro studies about the cell viability, the hemocompatibility, and the platelet aggregation of the MOFs were carried out. Epifluorescence microscopy assays confirmed the ability of ZIF-8 to target a carboxyfluorescein probe inside HeLa cell lines and PBMCs. These results pave the way for the use of these structures to eliminate latent HIV reservoirs from anatomical compartments through the activation of innate immune cells, and a higher efficacy of the triplet combinations of antiretroviral drugs.
Exploring the impact of nanoshaped ceria in the methanol decomposition reaction pathway for clean energy production
(Elsevier, 2024-09-27) Luque Álvarez, Ligia A.; Núñez Carballo, Ana; Lacroix, Bertrand; Sánchez de Armas, María Rocío; Centeno, Miguel A.; Pastor Pérez, Laura; Odriozola Gordón, José Antonio; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España
The effect of facet exposure in ceria nanostructures on the catalytic properties of Pd/CeO₂ during methanol decomposition was investigated. The results showed the structure sensitive nature of this reaction, with the catalytic activity depending on the facet exposed in the ceria nanostructures. Operando DRIFTS-MS and DFT calculations demonstrated that methanol decomposition proceeds mainly via two reaction pathways depending on the exposed nanofacets: the formate and the formaldehyde pathways. The formaldehyde pathway is inhibited on the (111) nanofacets, where only the formate pathway is energetically favoured, in contrast to the (100) and (110) facets. Superior specific catalytic activity was observed in the catalyst with octahedral morphology, attributed to the higher number of oxygen vacancies per unit surface area, which facilitates the decomposition of formates. By gaining a better understanding of the relationship between the shape control of the catalyst, this work contributes to the collective effort of discovering and implementing sustainable low-carbon energy solutions.
Tautomerism of adsorbed thymine on gold electrodes: an in situ surface-enhanced infrared spectroscopy study
(Elsevier, 2016-04-27) Prieto Dapena, Francisco; Álvarez Malmagro, Julia; Rueda Rueda, Manuela; Orts, José M.; Universidad de Sevilla. Departamento de Química Física; Ministerio de Economía y Competitividad (MINECO). España; Junta de Andalucía; Universidad de Sevilla. FQM202: Electroquímica Fundamental y Aplicada a Farmacia
The adsorption of thymine on gold electrodes has been studied by ATR-SEIRAS in situ spectroscopy at three pH values (1, 7 and 12), in order to analyse the tautomeric equilibrium of deprotonated thymine in the adsorbed state. The anionic form which is deprotonated in nitrogen N1 (N1 tautomer) and the one deprotonated in nitrogen N3 (N3 tautomer) are considered. The spectroscopic results have been interpreted in the light of DFT ab-initio calculations of both tautomeric forms adsorbed on gold surfaces. The basis sets 6-311 + +G(d,p) for C, H, O and N atoms and LANDL2DZ for Au atoms have been used. The electrode surface has been simulated as an unreconstructed Au(111) surface of 19 atoms. The preponderance of each tautomer of adsorbed thymine as a function of pH has been inferred from the analysis of the spectral signals in the 1500–1800 cm−1 wavenumber region related mostly to stretching modes of the carbonyl groups. It has been found that the adsorbed N3 tautomer predominates in the case of adsorption from acid media while the N1 tautomer predominates in the adsorption from basic media but the adsorption of both forms have been distinguished in the experiments from neutral media. Moreover, the plausible changes in the orientation of the two adsorbed tautomers with the electric field have been determined by analysing the relative intensities of the characteristic CH stretching signals in the 2800–3300 cm−1 spectral region. It is proposed that the N3 tautomer undergoes changes in the interaction sites with the metal and in the molecular plane orientation on the electrode as the electric potential is increased, but the N1 tautomer molecule keeps the interaction sites while the molecular plane slightly rotates to facilitate the electrostatic interaction with the field.
Evidences of adenine–thymine Interactions at gold electrodes interfaces as provided by in-situ infrared spectroscopy
(Elsevier, 2013) Rueda Rueda, Manuela; Prieto Dapena, Francisco; Álvarez Malmagro, Julia; Rodes, Antonio; Universidad de Sevilla. Departamento de Química Física; Ministerio de Educación. España; Generalitat Valenciana
The co-adsorption of complementary DNA bases adenine and thymine on gold thin-film electrodes from 0.1 M HClO4 solutions in H2O and D2O is studied by surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode (ATR-SEIRAS). The comparison of the spectra in the range 1750–1550 cm− 1 for co-adsorbed adenine and thymine at controlled potentials to those of the individual adsorbed bases shows the enhancement of the signals associated to the vibration modes of adenine and the inhibition of those of thymine. The results can be explained by invoking the rearrangement of both molecules on the electrode surface in order to facilitate the Watson–Crick (W–C) and/or Hoogsteen (HG) interactions between the bases. The co-adsorption seems to be a cooperative process in which a low surface concentration of each base can induce the rearrangement of the complementary base molecules on the surface.
Controlled formation of CoOOH/Co(III)-MOF active phase for boosting electrocatalytic alkaline water oxidation
(Elsevier, 2025) Márquez Escudero, Inmaculada; Gutiérrez Tarriño, Silvia; Portorreal Bottier, Arismendy Antonio; Río Rodríguez, José Luis del; Hernández Salvador, Sergio; Calvente Pacheco, Juan José; Oña Burgos, Pascual; Olloqui Sariego, José Luis; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
Surface reconstituted metal-organic frameworks (MOFs) offer appealing properties for electrocatalysis due to their unique structural and compositional advantages. In this work, a controlled potential-induced reconstruction of a two-dimensional cobalt metal-organic framework for boosting oxygen evolution reaction in alkaline media is reported. The current MOF is shown to undergo a partial structural transformation that generates a heterogeneous system, where the original MOF coexists with an oxyhydroxide phase. In fact, the potential-induced stabilization of Co(III) metal centers in the MOF is crucial for delaying its full degradation in alkaline media. This partial retention of the Co(III)MOF phase in the so-derived heterogeneous catalyst has been demonstrated to be decisive for boosting the alkaline electrocatalytic oxygen evolution reaction (OER), displaying superior OER activity in terms of both thermodynamic and kinetic merits compared to the benchmark IrO2 and RuO2 electrocatalysts and the prototypical cobalt (oxy)hydroxides, with a Tafel slope of 52 mV dec−1 and a turnover frequency (TOF) of 6.8 s−1 at 450 mV. Remarkably, the generated final product is stable, exhibiting high robustness and long durability for long-term OER electrolysis. This work provides new insight into the impact of the reconstruction of a MOF for alkaline OER under typical electrochemical conditions, which ultimately benefits the rational design of MOF-based catalysts with high electrocatalytic activity for oxidation reactions.
Electrochemical Impedance Spectroscopy study of the adsorption of adenine on Au(111) electrodes as a function of the pH
(2017-04-15) Prieto Dapena, Francisco; Álvarez Malmagro, Julia; Rueda Rueda, Manuela; Universidad de Sevilla. Departamento de Química Física; Ministerio de Economía y Competitividad (MINECO). España; Junta de Andalucía; Universidad de Sevilla. FQM202: Electroquímica Fundamental y Aplicada a Farmacia
The adsorption of the three adenine forms involved in two acid-base equilibria on Au(111) electrodes is studied by Electrochemical Impedance Spectroscopy. The experiments are performed in solutions of pH values 1, 7.5 and 12, at which the cationic, the neutral and the anionic adenine forms are present, respectively. Two adsorption models are adopted, both based on the theory of Frumkin and Melik-Gaykazyan for the adsorption process, but one of them takes also into account a deprotonation step preceding the adsorption step. The same frequency dependence of the impedance data is observed in the three pH media. The Nyquist admittance plots suggest a mixed kinetic control, by adsorption and by diffusion. The analysis of the electrode impedance or admittance as a function of the frequency according to the adsorption models provides the values of adsorption resistance, Rad, adsorption Warburg coefficient, σad and adsorption capacitance, Cad as a function of potential. From the σadvs E plot obtained at pH 1 an equilibrium constant for adenine deprotonation at the vicinity of the electrode surface of c.a. 0.03 is calculated, which is three orders of magnitude higher than the equilibrium constant in the bulk solution. The different potential dependency of the adsorption rates at the three pH values is discussed on the basis of a Frumkin isotherm for the adsorption of adenine and a Butler-Volmer type potential dependence for the adsorption rate constant.
Chemical nature evolution of solid supports used in electromembrane extraction procedures: A comparative analysis based on metric tools
(Elsevier, 2024-08-08) Román Hidalgo, Cristina; Villar Navarro, Mercedes; Martín Valero, María Jesús; López Pérez, Germán; Universidad de Sevilla. Departamento de Química Analítica; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España
Background: In recent decades, green chemistry has been focusing on the adaptation of different chemical methods towards environmental friendliness. Sample preparation procedures, which constitute a fundamental step in analytical methodology, have also been modified and implemented in this direction. In particular, electromembrane extraction (EME) procedures, which have traditionally used plastic supports, have been optimized towards greener approaches through the emergence of alternative materials. In this regard, biopolymer-based membranes (such as agarose or chitosan) have become versatile and very promising substitutes to perform these processes. Results: Different green metric tools (Analytical Eco-Scale, ComplexGAPI and AGREEprep have been applied to study the evolution of solid supports used in EME from nanostructured tissues and polymer inclusion membranes to agar films and chitosan flat membranes. The main goal is to evaluate the usage of these new biomaterials in the analytical procedure to quantify their environmental impact in the frame of Green Analytical Chemistry (GAC). In addition, both RGB model and BAGI metrics have been employed to study the sustainability of the whole procedure, including not only greenness, but also analytical performance and feasibility aspects. Results obtained after the performance of the mentioned metrics have demonstrated that the most efficient and environmentally friendly analytical methods are based on the use of chitosan supports. This improvement is mainly due to the chemical nature of this biopolymer as well as to the removal of organic solvents. Significance: This work highlights the advantages of biodegradable materials employment in EME procedures to achieve green analytical methodologies. These materials also contribute to raise the figure of merits regarding to the quantification parameters in a wide range of applications compared to classical supports employed in EME, thus enhancing sustainability of procedures.
Ultra-low Metal Loading Rhodium Phosphide Electrode for Efficient Alkaline Hydrogen Evolution Reaction
(Elsevier, 2024) Galdeano Ruano, Carmen; Márquez Escudero, Inmaculada; Lopes, Christian Wittee; Calvente Pacheco, Juan José; Agostini, Giovanni; Roldan, Alberto; Olloqui Sariego, José Luis; Oña Burgos, Pascual; Universidad de Sevilla. Departamento de Química Física; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE); Junta de Andalucía; Generalitat Valenciana
The practical production of hydrogen from water electrolyzers demands efficient electrocatalysts with maximized and optimized active sites that promote the Hydrogen Evolution Reaction (HER) at wide pH ranges. Herein, we successfully synthesized a rhodium-based nanomaterial with extremely low metal loading (2 μg/cm−2) as electrocatalyst for the HER. In particular, the material consists of carbon-supported rhodium phosphide (Rh2P) as active sites, which are partially covered with carbon patches. The so-developed nanomaterial exhibits high crystallinity, resistance to sintering, and outstanding electrocatalytic activity and operational stability in an extended pH interval. Notably, Rh2P displays specific-mass activities, ca. 2.5- and 5-fold higher than those of the benchmark 20 wt% Pt/C at an overpotential of 50 mV in acidic and alkaline media, respectively. Comparison of the electrocatalytic performance of the current Rh2P electrocatalyst with those of phosphorus-free rhodium NPs and an alternative rhodium phosphide nanomaterial, reveals that the inclusion of phosphorus atoms, the purity and crystallinity of the Rh2P phase are critical to boost the electrocatalytic HER. This is corroborated by theoretical simulations using DFT, which also prove that the presence of C-patches on Rh2P favors the H2O dissociation during HER electrocatalytic cycle and prevents phosphorous leaching. Overall, this work provides new insights for the rational design and controlled synthesis of small NPs for using as efficient electrocatalysts in hydrogen-based renewable energy devices.
High-Throughput Prediction of the Thermal and Electronic Transport Properties of Large Physical and Chemical Spaces Accelerated by Machine Learning: Charting the ZT of Binary Skutterudites
(American Chemical Society, 2024) Santana Andreo, Julia; Márquez Cruz, Antonio Marcial; Plata Ramos, José Javier; Blancas, Ernesto J.; González Sánchez, José Luis; Fernández Sanz, Javier; Nath, Pinku; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Red Española de Supercomputación (RES)
Thermal and electronic transport properties are the keys to many technological applications of materials. Thermoelectric, TE, materials can be considered a singular case in which not only one but three different transport properties are combined to describe their performance through their TE figure of merit, ZT. Despite the availability of high-throughput experimental techniques, synthesizing, characterizing, and measuring the properties of samples with numerous variables affecting ZT are not a cost- or time-efficient approach to lead this strategy. The significance of computational materials science in discovering new TE materials has been running in parallel to the development of new frameworks and methodologies to compute the electron and thermal transport properties linked to ZT. Nevertheless, the trade-off between computational cost and accuracy has hindered the reliable prediction of TE performance for large chemical spaces. In this work, we present for the first time the combination of new ab initio methodologies to predict transport properties with machine learning and a high-throughput framework to establish a solid foundation for the accurate prediction of thermal and electron transport properties. This strategy is applied to a whole family of materials, binary skutterudites, which are well-known as good TE candidates. Following this methodology, it is possible not only to connect ZT with the experimental synthetic (carrier concentration and grain size) and operando (temperature) variables but also to understand the physical and chemical phenomena that act as driving forces in the maximization of ZT for p-type and n-type binary skutterudites.
Dinitrogen Activation Mediated by the (P2PPh)Fe Complex: Electronic Structure, Dimerization Mechanism, and Magnetic Coupling
(American Chemical Society, 2024) Zapata Rivera, Jhon; Jiménez Calzado, Carmen; Universidad de Sevilla. Departamento de Química Física; Universidad de los Andes. Colombia; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España
Herein, we report the estimation of the extent of dinitrogen activation by different charged and structural forms of (P2PPh)Fe biomimetic catalysts, which, in the presence of light, exhibit significant yield in the N2-To-NH3 conversion. Complete active space self-consistent field (CASSCF) calculations have been used to determine the electronic structure of different reduced forms of the mononuclear complexes: The neutral (P2PPh)Fe(N2)2 adduct and the anionic [(P2PPh)Fe(N2)]- and [(P2PPh)Fe(N2)]2- complexes. These calculations also revealed that the extent of reduction of a dinitrogen molecule reaches up to one electron (N2 1-) due to the back-bonding from the Fe center, in agreement with the changes observed in the vibration frequency of the N-N bond in these complexes. In addition, the energy profile of the dimerization of the mononuclear (P2PPh)Fe(N2)2 complex to the dinuclear mono-N2-bridged [(P2PPh)Fe]2(μ-N2) complex has been determined by means of density functional theory (DFT) calculations. A three-step mechanism has been proposed for the dimerization, favored by both kinetics and thermodynamics criteria. Finally, the magnetic coupling constant in the diiron (μ-N2) complex is estimated from CASSCF/NEVPT2 calculations. Such a dinuclear complex presents a strong antiferromagnetic coupling resulting from the interaction between two S = 1 d6 Fe2+ ions, bridged by a highly activated dinitrogen molecule (N2 2-) with two electrons on the φ orbitals.
Understanding the potential-induced activation of a cobalt MOF electrocatalyst for the oxygen evolution reaction
(Elsevier, 2023-03-13) Gutiérrez Tarriño, Silvia; Portorreal Bottier, Arismendy Antonio; Trasobares, Susana; Calvente Pacheco, Juan José; Calvino, José J.; Olloqui Sariego, José Luis; Oña Burgos, Pascual; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Unión Europea (EU); Junta de Andalucía
Metal–organic frameworks (MOFs) are attractive porous materials for electrocatalytic applications associated with carbon-free energy storage and conversion. This type of material usually requires a post-treatment to be used as electrocatalyst. The present work comprehensively investigates the electrochemical activation of a cobalt-MOF@Nafion composite that produces outstanding electrocatalytic performance for the water oxidation reaction at neutral pH. A detailed electrochemical characterization reveals that the electroactivation of the composite requires the participation of the oxygen evolution reaction (OER) and leads to a significant increase in the electroactive population of cobalt centers. It is shown that an increase of the applied activation potential in the OER region results in a faster electroactivation of the Co-MOF without affecting the intrinsic electrocatalytic properties of the active cobalt centers, as evidenced by the unique linear correlation between the electrocatalytic OER current and the population of electroactive cobalt. In addition, at structural level, it is shown that the electrochemical activation causes the partial disruption of the Nafion adlayer, as well as morphological changes of the Co–MOF particles from a compact, rounded morphology, before electrochemical activation, to a more open and expanded structure, after electroactivation; with the concomitant increase of the number of surface–exposed cobalt centers. Interestingly, these cobalt centers retain their coordinative chemistry and their laminar distribution in the nanosheets at the nanoscale, which is consistent with the preservation of their intrinsic electrocatalytic activity after potential–induced activation. In this scenario, these results suggest that only the electroactivated cobalt centers with good accessibility to the electrolyte are electrochemically active. This work provides a better understanding of the processes and structural changes underlying the electrochemical activation at neutral pH of a Co–MOF for boosting the electrocatalytic water oxidation reaction.
Recursos TICs para la evaluación del proceso enseñanza-aprendizaje en clases prácticas de laboratorio
(Real e Ilustre Colegio Oficial de Farmacéuticos de Sevilla, 2023) Márquez Escudero, Inmaculada; Universidad de Sevilla. Departamento de Química Física
Recientemente, los recursos TICs han adquirido especial relevancia en la enseñanza universitaria debido a la gran variedad de contenido educativo que permiten generar en función de las necesidades de los estudiantes. Muchos de estos recursos están diseñados para mejorar la calidad de la enseñanza y favorecer el aprendizaje de una forma más rápida. Por ello, en el presente trabajo se propone el uso de recursos TICs en clases prácticas de laboratorio para el diagnóstico inicial de ideas previas y/o la evaluación final de los conocimientos adquiridos. El estudio llevado a cabo empleando las aplicaciones Socrative y Google Form muestra que el uso de estas herramientas constituye una forma adecuada de evaluar a tiempo real el nivel que presentan los alumnos antes de comenzar las sesiones prácticas y al finalizarlas, permitiendo adaptar el ritmo de las sesiones a sus necesidades. Asimismo, el empleo de recursos TICs fomenta la implicación de los alumnos en el proceso enseñanza-aprendizaje en las clases prácticas.
Theoretical Investigation of the Lattice Thermal Conductivities of II-IV-V2 Pnictide Semiconductors
(AMER Chemical Society, 2023-11-06) Posligua, Víctor; Plata Ramos, José Javier; Márquez Cruz, Antonio Marcial; Fernández Sanz, Javier; Grau-Crespo, Ricardo; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Unión Europea (UE); UK's Materials and Molecular Modelling Hub
Ternary pnictide semiconductors with II−IV−V2 stoichiometry hold potential as cost-effective thermoelectric materials with suitable electronic transport properties, but their lattice thermal conductivities (κ) are typically too high. Insights into their vibrational properties are therefore crucial to finding strategies to reduce κ and achieve improved thermoelectric performance. We present a theoretical exploration of the lattice thermal conductivities for a set of pnictide semiconductors with ABX2 composition (A = Zn, Cd; B = Si, Ge, Sn; and X = P, As) using machine-learning-based regression algorithms to extract force constants from a reduced number of density functional theory simulations and then solving the Boltzmann transport equation for phonons. Our results align well with available experimental data, decreasing the mean absolute error by ∼3 W m−1 K−1 with respect to the best previous set of theoretical predictions. Zn-based ternary pnictides have, on average, more than double the thermal conductivity of the Cd-based compounds. Anisotropic behavior increases with the mass difference between A and B cations, but while the nature of the anion does not affect the structural anisotropy, the thermal conductivity anisotropy is typically higher for arsenides than for phosphides. We identify compounds such as CdGeAs2, for which nanostructuring to an affordable range of particle sizes could lead to κ values low enough for thermoelectric applications.
Harnessing the unusually strong improvement of thermoelectric performance of AgInTe2 with nanostructuring
(Royal Society of Chemistry, 2023-07-20) Plata Ramos, José Javier; Blancas, Ernesto J.; Márquez Cruz, Antonio Marcial; Posligua, Víctor; Fernández Sanz, Javier; Grau Crespo, Ricardo; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE); Red Española de Supercomputación (RES); Engineering and Physical Sciences Research Council (EPSRC)
Nanostructuring is a well-established approach to improve the thermoelectric behavior of materials. However, its effectiveness is restricted if excessively small particle sizes are necessary to considerably decrease the lattice thermal conductivity. Furthermore, if the electrical conductivity is unfavorably affected by the nanostructuring, it could cancel out the advantages of this approach. Computer simulations predict that silver indium telluride, AgInTe2, is unique among chalcopyrite-structured chalcogenides in requiring only a mild reduction of particle size to achieve a substantial reduction in lattice thermal conductivity. Here, ab initio calculations and machine learning are combined to systematically chart the thermoelectric properties of nanostructured AgInTe2, in comparison with its Cu-based counterpart, CuInTe2. In addition to temperature and doping carrier concentration dependence, ZT is calculated for both materials as functions of the polycrystalline average grain size, taking into account the effect of nanostructuring on both phonon and electron transport. It is shown that the different order of magnitude between the mean free path of electrons and phonons disentangles the connection between the power factor and lattice thermal conductivity when reducing the crystal size. ZT values up to 2 are predicted for p-type AgInTe2 at 700 K when the average grain size is in the affordable 10–100 nm range.

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