23 research outputs found
Gold Nucleation Inhibition by Halide Ions: a Basis for a Seed-Mediated Approach
In the present work, we examine the effect of halide ions on gold nucleation, a typical synthetic variable in the wet-chemical production of gold nanostructures. It was found that the homogeneous nucleation of gold by the chemical reduction of aqueous gold ions is kinetically quenched by an increase in the concentration of halide ions, and this effect grows stronger as the Au–halide complex stability increases. The nucleation quenching is not exclusively related to a specific reducing agent, but appears to be a more general behavior, and is affected by the pH of the media. While no nucleation is observed, Au(I) metastable species coexist together with the reducer, constituting metastable solutions. It is demonstrated that nucleation inhibition by halide ions can be employed as a basis for a seed-mediated approach to produce gold nanostructures. The metastable solutions are proved to function as growth baths, where Au(I) reduction is triggered on the surface of previously synthesized gold nanoparticles, driving their growth in the absence of secondary nucleation. It is also shown how, with this approach, the synthesis conditions can be rationally designed to obtain gold nanoparticles with the desired properties in a controlled and reproducible fashion.Fil: Moiraghi, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Douglas Gallardo, Oscar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Coronado, Eduardo A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Macagno, Vicente Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Perez, Manuel Alejo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin
Plasmonic enhancement of molecular hydrogen dissociation on metallic magnesium nanoclusters
Light-driven plasmonic enhancement of chemical reactions on metal catalysts
is a promising strategy to achieve highly selective and efficient chemical
transformations. The study of plasmonic catalyst materials has traditionally
focused on late transition metals such as Au, Ag, and Cu. In recent years,
there has been increasing interest in the plasmonic properties of a set of
earth-abundant elements such as Mg, which exhibit interesting hydrogenation
chemistry with potential applications in hydrogen storage. This work explores
the optical, electronic, and catalytic properties of a set of metallic Mg
nanoclusters with up to 2057 atoms using time-dependent density functional
tight-binding and density functional theory calculations. Our results show that
Mg nanoclusters are able to produce highly energetic hot electrons with
energies of up to 4 eV. By electronic structure analysis, we find that these
hot electrons energetically align with electronic states of physisorbed
molecular hydrogen, occupation of which by hot electrons can promote the
hydrogen dissociation reaction. We also find that the reverse reaction,
hydrogen evolution on metallic Mg, can potentially be promoted by hot
electrons, but following a different mechanism. Thus, from a theoretical
perspective, Mg nanoclusters display very promising behaviour for their use in
light promoted storage and release of hydrogen
Importance of equivariant features in machine-learning interatomic potentials for reactive chemistry at metal surfaces
Reactive chemistry of molecular hydrogen at surfaces, notably dissociative
sticking and hydrogen evolution, play a crucial role in energy storage, fuel
cells, and chemical synthesis. Copper is a particularly interesting metal for
studying these processes due to its widespread use as both a catalyst in
industry and a model catalyst in fundamental research. Theoretical studies can
help to decipher underlying mechanisms and reaction design, but studying these
systems computationally is challenging due to the complex electronic structure
of metal surfaces and the high sensitivity towards reaction barriers. In
addition, ab initio molecular dynamics, based on density functional theory, is
too computationally demanding to explicitly simulate reactive sticking or
desorption probabilities. A promising solution to such problems can be provided
through high-dimensional machine learning-based interatomic potentials (MLIPs).
Despite the remarkable accuracy and fidelity of MLIPs, particularly in
molecular and bulk inorganic materials simulations, their application to
different facets of hybrid systems and the selection of appropriate
representations remain largely unexplored. This paper addresses these issues
and investigates how feature equivariance in MLIPs impacts adaptive sampling
workflows and data efficiency. Specifically, we develop high-dimensional MLIPs
to investigate reactive hydrogen scattering on copper surfaces and compare the
performance of various MLIPs that use equivariant features for atomic
representation (PaiNN) with those that use invariant representations (SchNet).
Our findings demonstrate that using equivariant features can greatly enhance
the accuracy and reliability of MLIPs for gas surface dynamics and that this
approach should become the standard in this field
Silver oxide particles/silver nanoparticles interconversion: Susceptibility of forward/backward reactions to the chemical environment at room temperature
The thermal stability of the silver oxide particles (Ag 2O)/ metallic silver nanoparticles (AgNPs) system in aqueous and gaseous environments is investigated with UV-Visible spectroscopy, TEM, SEM and DLS as characterisation techniques, and with calculations using electromagnetic theory. Thermal decomposition of aqueous Ag 2O colloids to produce AgNPs is conclusively demonstrated and used as a base reaction to produce clean AgNPs without any external reducing agent. Such a spontaneous character of Ag 2O decomposition in alkaline aqueous/water-enriched environments at room temperature makes the formation of silver oxide films on silver nanoparticles/nanostructures unlikely, keeping the silver surface oxide-free, a crucial feature in determining the silver catalytic and Raman enhancing properties. The synthetic suitability of this reaction to develop new routes to produce AgNPs is explored by analyzing the effect of temperature, complexing agents, and environment polarity on the AgNPs size/shape control. Thermal decomposition of Ag 2O colloids in aqueous/water-enriched environments offers the possibility to produce AgNPs at low cost, with easy, clean, safe and green chemistry procedures.Fil: Douglas Gallardo, Oscar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Moiraghi, Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Macchione, Micaela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Godoy, Jorge A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Perez, Manuel Alejo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Coronado, Eduardo A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Macagno, Vicente Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin
NQCDynamics.jl : a Julia package for nonadiabatic quantum classical molecular dynamics in the condensed phase
Accurate and efficient methods to simulate nonadiabatic and quantum nuclear effects in high-dimensional and dissipative systems are crucial for the prediction of chemical dynamics in condensed phase. To facilitate effective development, code sharing and uptake of newly developed dynamics methods, it is important that software implementations can be easily accessed and built upon.Using the Julia programming language, we have developed the \pkgname ~ package which provides a framework for established and emerging methods for performing semiclassical and mixed quantum-classical dynamics in condensed phase. The code provides several interfaces to existing atomistic simulation frameworks, electronic structure codes, and machine learning representations. In addition to the existing methods, the package provides infrastructure for developing and deploying new dynamics methods which we hope will benefit reproducibility and code sharing in the field of condensed phase quantum dynamics. Herein, we present our code design choices and the specific Julia programming features from which they benefit.We further demonstrate the capabilities of the package on two examples of chemical dynamics in condensed phase: the population dynamics of the spin-boson model as described by a wide variety of semi-classical and mixed quantum-classical nonadiabatic methods and the reactive scattering of H2 on Ag(111) using the Molecular Dynamics with Electronic Friction method. Together, they exemplify the broad scope of the package to study effective model Hamiltonians and realistic atomistic systems
Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study
: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI
Métodos Sintéticos para la producción de organosoles metálicos
Estudios fisicoquímico del mecanismo de cambio morfológico en sistemas experimentales modelo y su aplicación a la síntesis de metales activos.La nanociencia es una nueva área interdisciplinaria con foco en el estudio de objetos o estructuras que presentan al menos una de sus dimensiones (alto, largo, ancho) en la escala del nanómetro (1nm=10-9 m). Estas nanoestructuras (NEs) han ganado un enorme interés en el área debido a sus propiendades fisicoquímicas emergentes y a sus potenciales aplicaciones. En particular, las nanopárticulas (NPs) de metales nobles (Au, Ag) han sido ampliamenteestudiadas debido a sus promisorias aplicaciones en catálisis, reconocimiento de biomoléculas, propiedades ópticas dependientes del tamaño y la forma, estudios de dispersión Raman exacerbada por superficie (SERS) y aplicaciones biomédicas. Las propiedades emergentes resultan ser extremadamente sensible a la forma, el tamaño, la cristalinidad y composición química de las NPs. en este sentido, el estudio preciso de dichas propiedades demanda del desarrollo de métodos de síntesis y fabricación, capaces de producir NEs o NPs con las características morfológicas deseadas. Asi, la síntesis de NPs o NEs constituyente un pilar fundamental de la nanociencia y es, consecuentemente, un área de investigación muy activa. Si bien la síntesis de NPs resulta ser, en general, relativamente sencilla, la gran cantidad de variable sintéticas que entran en juego y que determinan el producto final hacen extremadamente complejo el estudio de dichos sistemas sinténticos. En este contexto el objetivo principal del trabajo de Tesis fue el desarrollo y la implementacion de rutas sintéticas reproducibles capaces de producir nanoestructuras metálicas con especial interés de materiales magnéticos.Este problema general se abordó mediante la investigación de los procesos fisicoquímicos involucrados haciendo foco en la quimica más que en la mera obtención de estos objetos. La estrategia de trabajo consistió en investigar sistemas experimentales modelos basados en la síntesis de nanopartículas de Au y Ag los cuales permitieron monitorear e identificar la influencia de diferentes variables experimentales en función de sus propiedades ópticas características
Communication: Photoinduced Carbon Dioxide Binding with Surface-Functionalized Silicon Quantum Dots
Nowadays, the search of efficient methods able to reduce the high atmospheric carbon dioxide
concentration has turned into a very dynamic research area. Several environmental problems
have been closely associated with the high atmospheric level of this greenhouse gas. Here,
a novel system based on the use of surface-functionalized silicon quantum dots (sf -SiQDs)
is theoretically proposed as a versatile device to bind carbon dioxide. Within this approach,
carbon dioxide trapping is modulated by a photoinduced charge redistribution between the
capping molecule and the silicon quantum dots (SiQDs). Chemical and electronic properties
of the proposed SiQDs have been studied with Density Functional Theory (DFT) and Density
Functional Tight-Binding (DFTB) approach along with a Time-Dependent model based on
the DFTB (TD-DFTB) framework. To the best of our knowledge, this is the first report
that proposes and explores the potential application of a versatile and friendly device based
on the use of sf -SiQDs for photochemically activated carbon dioxide fixation.
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Atomistic Insights into Chemical Interface Damping of Surface Plasmon Excitations in Silver Nanoclusters
A detailed description of the mechanism underlying chemical interface damping (CID) in silver nanoclusters is presented. The effect of adsorbates on the surface plasmon excitation in silver nanoclusters is explored by means of a method based on time-dependent self-consistent charge density functional tight binding (TD-SCC-DFTB). By using this tool, we have calculated the homogeneous line width of the surface plasmon resonance (SPR) band for both naked and capped silver nanoclusters. A new picture explaining the decreased lifetime of the surface plasmon excitations is provided, in which coupling between particles states via adsorbate states enhances the natural dephasing mechanism of the surface plasmon excitation. To the best of our knowledge, this is the first report that addresses this topic from a fully atomistic time-dependent approach considering nanosized particles.Fil: Douglas Gallardo, Oscar Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Berdakin, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Sanchez, Cristian Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin
Plasmon-Induced Hot-Carrier Generation differences in Gold and Silver Nanoclusters
In the last thirty years, the study of plasmonic properties of noble metal nanostructures has become a very dynamic research area. The design and manipulation of matter in the nanometric scale demand a deep understanding of the underlying physico-chemical processes that operate in this size regimen. Here, a fully atomistic study of the spectroscopic and photodynamic properties of different icosahedral silver and gold nanoclusters have been carried out by using Time-Dependent Density Functional Tight-Binding (TD-DFTB) model. Optical absorption spectra of different icosahedral silver and gold nanoclusters of diameters between 1 and 4 nanometers has been simulated. Furthermore, the energy absorption process have been quantified by means of calculating a fully quantum absorption cross-section using the information contained in the reduced single-electron density matrix. This approach allows us take into account for the quantum confinement effects dominating in this size regime. Likewise, the plasmon-induced hot-carrier generation process under laser illuminations have been explored from a fully dynamical perspective. We have found noticeable differences in the energy absorption mechanisms and the plasmon-induced hot-carrier generation process in both metals which can be explained by their respective electronic structures. These difference can be attributed to the existence of ultra-fast electronic dissipation channels in gold nanoclusters that are absented in silver nanoclusters. To the best of our knowledge, this is the first report that addresses this topic from a real time fully atomistic time-dependent approach. <br /