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The effects on the lattice structure and electronic properties of different polymorphs of silver halide, AgX (X = Cl, Br, and I), induced by laser irradiation (LI) and electron irradiation (EI) are investigated using a first-principles approach, based on the electronic temperature (Te) within a two-temperature model (TTM) and by increasing the total number of electrons (Ne), respectively. Ab initio molecular dynamics (AIMD) simulations provide a clear visualization of how Te and Ne induce a structural and electronic transformation process during LI/EI. Our results reveal the diffusion processes of Ag and X ions, the amorphization of the AgX lattices, and a straightforward interpretation of the time evolution for the formation of Ag and X nanoclusters under high values of Te and Ne. Overall, the present work provides fine details of the underlying mechanism of LI/EI and promises to be a powerful toolbox for further cross-scale modeling of other semiconductors.

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In this work, α-Ag2-2xCuxWO4 (0 ≤ x ≤ 0.16) solid solutions with enhanced antibacterial (against methicillin-resistant Staphylococcus aureus) and antifungal (against Candida albicans) activities are reported. A plethora of techniques (X-ray diffraction with Rietveld refinements, inductively coupled plasma atomic emission spectrometry, micro-Raman spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, field emission scanning electron microscopy, ultraviolet-visible spectroscopy, photoluminescence emissions, and X-ray photoelectron spectroscopy) were employed to characterize the as-synthetized samples and determine the local coordination geometry of Cu2+ cations at the orthorhombic lattice. To find a correlation between morphology and biocide activity, the experimental results were sustained by first-principles calculations at the density functional theory level to decipher the cluster coordinations and electronic properties of the exposed surfaces. Based on the analysis of the under-coordinated Ag and Cu clusters at the (010) and (101) exposed surfaces, we propose a mechanism to explain the biocide activity of these solid solutions.

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The current unprecedented coronavirus pandemic (COVID-19) is increasingly demanding advanced materials and new technologies to protect us and inactivate SARS-CoV-2. In this research work, we report the manufacture of Ag3PO4 (AP)/polypropylene (PP) composites using a simple method and also reveal their long-term anti-SARS-CoV-2 activity. This composite shows superior antibacterial (against Staphylococcus aureus and Escherichia coli) and antifungal activity (against Candida albicans), thus having potential for a variety of technological applications. The as-manufactured materials were characterized by XRD, Raman spectroscopy, FTIR spectroscopy, AFM, UV-vis spectroscopy, rheology, SEM, and contact angle to confirm their structural integrity. Based on the results of first-principles calculations at the density functional level, a plausible reaction mechanism for the initial events associated with the generation of both hydroxyl radical •OH and superoxide radical anion •O2- in the most reactive (110) surface of AP was proposed. AP/PP composites proved to be an attractive avenue to provide human beings with a broad spectrum of biocide activity.

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The structural behavior of some cutin monomers, when deposited on mica support, was extensively investigated by our research group. However, other events, such as esterification reaction (ER), are still a way to explore. In this paper, we explore possible ER that could occur when these monomers adsorb on support. Although classical molecular dynamics simulations are not able to capture reactive effects, here, we show that they become valuable strategies to analyze the initial structural configurations to predict the most favorable reaction routes. Thus, when depositing aleuritic acid (ALE), it is observed that the loss of capacity to form self-assembled (SA) systems favors different routes to occur ER. In pure ALE bilayers systems, an ER is given exclusively through the -COOH and primary -OH groups. In pure ALE monolayers systems, the ER does not happen when the system is self-assembled. However, for disorganized systems, it is able to occur by two possible routes: -COOH and primary -OH (route 1) and -COOH and secondary -OH (route 2). When palmitic acid (PAL) is added in small quantities, ALE SAMs can now form an ER. In this case, ER occurs mostly through the -COOH and secondary -OH groups. However, when the presence of PAL is dominant, ER can occur with either of both possibilities, that is, routes 1 and 2. Graphical abstract.

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In nanotechnology research, significant effort is devoted to fabricating patterns of metallic nanoparticles on the surfaces of different semiconductors to find innovative materials with favorable characteristics, such as antimicrobial and photocatalytic properties, for novel applications. We present experimental and computational progress, involving a combined approach, on the antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) of as-synthesized α-Ag2WO4 samples and Ag nanoparticle composites (Ag NPs)/α-Ag2WO4. The former included two morphologies: hexagonal rod-like (α-Ag2WO4-R) and cuboid-like (α-Ag2WO4-C), and the latter included composites formed under electron beam, Ag NPs/α-Ag2WO4-RE and Ag NPs/α-Ag2WO4-CE, and femtosecond (fs) laser irradiation, Ag NPs/α-Ag2WO4-RL and Ag NPs/α-Ag2WO4-CL. Direct observations of the arrangement of Ag NPs on the Ag NPs/α-Ag2WO4 composites irradiated with an electron beam and laser, through transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, and field-emission scanning electron microscopy, allow us to investigate the surface morphology, chemical composition, homogeneity, and crystallinity. Therefore, these experimental factors, and in particular, the facet-dependent response of Ag NPs/α-Ag2WO4 composites were discussed and analyzed from the perspective provided by the results obtained by first-principles calculations. On this basis, α-Ag2WO4-R material proved to be a better bactericidal agent than α-Ag2WO4-C with minimum bactericidal concentration (MBC) values of 128 and 256 µg/mL, respectively. However, the Ag NPs/α-Ag2WO4-CL composite is the most efficient bactericidal agent of all tested samples (MBC = 4 µg/mL). This superior performance can be attributed to the cooperative effects of crystal facets and defect engineering. These results on the synthesis and stability of the Ag NPs/α-Ag2WO4 composites can be used for the development of highly efficient bactericidal agents for use in environmental remediation and the potential extension of methods to produce materials with catalytic applications.

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Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements.

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Why and how Ag is formed when electron beam irradiation takes place on α-Ag2WO4 in a vacuum transmission electron microscopy chamber? To find an answer, the atomic-scale mechanisms underlying the formation and growth of Ag on α-Ag2WO4 have been investigated by detailed in situ transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) studies, density functional theory based calculations and ab initio molecular dynamics simulations. The growth process at different times, chemical composition, size distribution and element distribution were analyzed in depth at the nanoscale level using FE-SEM, operated at different voltages (5, 10, 15, and 20 kV), and TEM with energy dispersive spectroscopy (EDS) characterization. The size of Ag nanoparticles covers a wide range of values. Most of the Ag particles are in the 20-40 nm range. The nucleation and formation of Ag on α-Ag2WO4 is a result of structural and electronic changes in the AgOx (x = 2,4, 6, and 7) clusters used as constituent building blocks of this material, consistent with metallic Ag formation. First principle calculations point out that Ag-3 and Ag-4-fold coordinated centers, located in the sub-surface of the (100) surface, are the most energetically favorable to undergo the diffusion process to form metallic Ag. Ab initio molecular dynamics simulations and the nudged elastic band (NEB) method were used to investigate the minimum energy pathways of these Ag atoms from positions in the first slab layer to outward sites on the (100) surface of α-Ag2WO4. The results point out that the injection of electrons decreases the activation barrier for this diffusion step and this unusual behavior results from the presence of a lower energy barrier process.

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Las patologías del piso pelviano han ido ganando la atención de los cirujanos colorrectales durante los últimos 20 años. Distintos procedimientos diagnósticos han sido desarrollados. Algunos aún permanecen como experimentales y otros son ampliamente utilizados. La neurofisiología aplicada a las patologías del piso pelviano (por ej.: constipación e incontinencia) es rutinariamente utilizada como elementos tanto diagnósticos como terapéuticos. Los procedimientos diagnósticos en neurofisiología del piso pelviano son básicamente tres: 1) Tiempo de latencia de Nervios Pudendos, 2) Electromiografía con aguja electrodo concéntrico y 3) Electromiografía de fibra simple. En nuestra experiencia, la prolongación del Tiempo de Latencia de Nervios Pudendos, y el incremento en la densidad de fibra, no se correlacionó con un mayor score de incontinencia. Por el contrario, la disminución en el reclutamiento de potenciales de unidad motora sí se correlacionó con un score de incontinencia mayor. En el grupo de pacientes con constipación, este procedimiento contribuyó a diagnosticar un cuadro de contracción paradojal del haz puborrectal o una relajación incompleta del mismo en un 50 por ciento de los pacientes que consultaron con cuadros de constipación y/o dificultad evacuatoria. (AU)

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Las patologías del piso pelviano han ido ganando la atención de los cirujanos colorrectales durante los últimos 20 años. Distintos procedimientos diagnósticos han sido desarrollados. Algunos aún permanecen como experimentales y otros son ampliamente utilizados. La neurofisiología aplicada a las patologías del piso pelviano (por ej.: constipación e incontinencia) es rutinariamente utilizada como elementos tanto diagnósticos como terapéuticos. Los procedimientos diagnósticos en neurofisiología del piso pelviano son básicamente tres: 1) Tiempo de latencia de Nervios Pudendos, 2) Electromiografía con aguja electrodo concéntrico y 3) Electromiografía de fibra simple. En nuestra experiencia, la prolongación del Tiempo de Latencia de Nervios Pudendos, y el incremento en la densidad de fibra, no se correlacionó con un mayor score de incontinencia. Por el contrario, la disminución en el reclutamiento de potenciales de unidad motora sí se correlacionó con un score de incontinencia mayor. En el grupo de pacientes con constipación, este procedimiento contribuyó a diagnosticar un cuadro de contracción paradojal del haz puborrectal o una relajación incompleta del mismo en un 50 por ciento de los pacientes que consultaron con cuadros de constipación y/o dificultad evacuatoria.

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Tanto la manometría como la electromiografía son dos buenos procedimientos de evacuación objetiva del mecanismo esfinteriano, proveyendo información más precisa que el simple examen digital, en los casos de incontinencia anorrectal. El hallazgo de bajas presiones en el conducto anal, ya sea en toda su circunferencia o en alguna de sus caras, juntamente con una baja presión de contracción máxima, se ha correlacionado con un examen electromiográfico patológico. La aplicación clínica de estos procedimientos radica en una mejor planificación del tratamiento más adecuado para cada paciente, sea este quirúrgico, o de reaprendizaje con técnica de biofeddback.

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Tanto la manometría como la electromiografía son dos buenos procedimientos de evacuación objetiva del mecanismo esfinteriano, proveyendo información más precisa que el simple examen digital, en los casos de incontinencia anorrectal. El hallazgo de bajas presiones en el conducto anal, ya sea en toda su circunferencia o en alguna de sus caras, juntamente con una baja presión de contracción máxima, se ha correlacionado con un examen electromiográfico patológico. La aplicación clínica de estos procedimientos radica en una mejor planificación del tratamiento más adecuado para cada paciente, sea este quirúrgico, o de reaprendizaje con técnica de biofeddback. (AU)

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