Yazar "Flores-Moreno, Roberto" seçeneğine göre listele

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    Interaction of pristine and novel graphene allotropes with copper nanoparticles: Coupled density functional and molecular dynamics study
    (Elsevier Science Sa, 2023) Katin, Konstantin P.; Kochaev, Alexey I.; Bereznitskiy, Igor V.; Kalika, Elizaveta B.; Kaya, Savas; Flores-Moreno, Roberto; Maslov, Mikhail M.
    We combined the density functional theory and classical molecular dynamics to study the time evolution and thermal stability of copper nanoparticles wrapped in graphene flakes. We observed a strong attraction between nanoparticles and flakes, which was underestimated in many previous simulations. We found that the twoparameter Lennard-Jones potential with parameters & epsilon; = 0.074 eV and r0 = 3.310 & ANGS; reproduces DFT data better than other empirical potentials. We confirmed that a nanoparticle could be held reliable inside a graphene flake. The graphene-coated copper system remains stable over the temperature range of 300-1000 K. In addition to pristine graphene, we considered several strained allotropes containing pentagons, as well as heptagons, octagons, and nanometer-sized pores. Strained allotropes interact with copper nanoparticles approximately twice more strongly as compared to pristine graphene. Molecular dynamics revealed nanoparticle flattening due to strong interaction with graphene allotropes at elevated temperatures. The wettability of graphene with respect to copper strongly depends on the sheet structure and can vary significantly for different allotropes. The results may be useful for further research on copper-graphene composites, which are suitable for catalytic and biomedical applications.
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    On point perforating defects in bilayer structures
    (Royal Soc Chemistry, 2023) Kochaev, Aleksey I.; Efimov, Vladimir V.; Kaya, Savas; Flores-Moreno, Roberto; Katin, Konstantin P.; Maslov, Mikhail M.
    This article deals with the issue of perforating point defects (pores) in a bilayer heterostructure composed of striped borophene and graphene. Three types of non-equivalent vacancies of the minimum size are considered. These include a single vacancy and two double vacancies. The study of the properties and stability of the perforating defects in borophene-graphene heterostructures is important given the increasing role of such structures in membranes for water purification, renewable energy generation, and other osmotic applications. Using the DFT method, the atomic configurations and main energy characteristics of the proposed defects are obtained. The results show that the formation of a single boron vacancy on the borophene side of borophene-graphene requires less energy than the formation of a carbon vacancy in graphene. Comparisons between double vacancies in nanoscale materials are unreliable because different reference systems produce the different chemical potentials. The problem of choosing the reference system for reliable calculation of the vacancy formation energies is posed and discussed. Using borophene-graphene as an example, it is shown that the reference system strongly affects the magnitude and sign of the vacancy formation energy. Hydrogenation is tested to stabilize the proposed defects. This article deals with the issue of perforating point defects (pores) in a bilayer heterostructure composed of striped borophene and graphene.
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    Semiempirical Approach to the Fukui Function Analysis of Uric Acid under Different pH Conditions
    (Amer Chemical Soc, 2023) Fontanini, Roberto E.; Flores-Moreno, Roberto; Zuniga-Gutierrez, Bernardo A.; Kaya, Savas; Katin, Konstantin P.; Maslov, Mikhail M.; Kochaev, Aleksey
    Analytic Fukui functions calculated at a first-principles level are combined with experimental pK(a) values and the calculation of tautomerization energies to obtain the effective regioselectivity of uric acid toward electron-transfer reactions under different pH conditions. Second-order electron binding energies are also computed to determine which of the tautomers is more likely to participate in the electron transfer. A comparison of vertical and adiabatic proton detachment energies allows us to conclude that tautomerization is not mediating deprotonation and that two monoanionic species are of comparable relevance. The main difference between these monoanionic species is the ring that has been deprotonated. Both monoanionic species are produced from a single neutral tautomer and mainly produce a single dianionic tautomer. As a method for the analysis of systems affected by pH such as uric acid, we propose to plot condensed Fukui functions versus pH, allowing us to draw the effect of pH on the regioselectivity of electron transfer in a single image.