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Shape, size, pressure and matrix effects on 2D spin crossover nanomaterials studied using density of states obtained by dynamic programming
(Elsevier, 2020-09-29)
In the present work, numerical simulations based on a new algorithm specific for 2D configurational topology of spin crossover nanoparticles embedded in a matrix are presented and discussed in the framework of the Ising-like model taking into account for short- (J) and long-range (G) interactions as for surface effects (L). The new algorithm is applied to calculate the density of states for each macro-state, which is then used to calculate exactly the thermal behavior of spin-crossover nanoparticles under an applied pressure. We find that the pressure plays the role of a conjugate parameter of the temperature. Thus, increasing pressure is somehow equivalent to reducing the temperature.
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Hexagonal-shaped spin crossover nanoparticles studied by Ising-like model solved by local mean field approximation
(MDPI AG, 2021-05-01)
The properties of spin crossover (SCO) nanoparticles were studied for five 2D hexagonal lattice structures of increasing sizes embedded in a matrix, thus affecting the thermal properties of the SCO region. These effects were modeled using the Ising-like model in the framework of local mean field approximation (LMFA). The systematic combined effect of the different types of couplings, consisting of (i) bulk short-and long-range interactions and (ii) edge and corner interactions at the surface mediated by the matrix environment, were investigated by using parameter values typical of SCO complexes. Gradual two and three hysteretic transition curves from the LS to HS states were obtained. The results were interpreted in terms of the competition between the structure-dependent order and disorder temperatures (TO.D. ) of internal coupling origin and the ligand field-dependent equilibrium temperatures (Teq ) of external origin.
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Synthesis, characterization and antifungal activity against Aspergillus ochraceopetaliformis of ZnO and copper-doped ZnO nanoparticles
(Elsevier, 2025)
In recent years, the interest in obtaining nanomaterials with antifungal properties has increased in the food industry. In this article, we present the synthesis by chemical precipitation and characterization of undoped/copper-doped ZnO nanoparticles. The obtained samples show a hexagonal arrangement (wurtzite) according to the X-ray diffraction (XRD) spectra. XRD confirmed that Cu ions enter the crystal lattice without affecting the structure of ZnO. Undoped/copper-doped ZnO nanoparticles exhibit spherical morphologies with average diameters of 19.56 ± 3.37 nm (0 at. % Cu), 26.21 ± 5.18 nm (0.4 at. % Cu) and 30.91 ± 2.43 nm (0.9 at. % Cu), respectively. The bandgap values of the prepared samples ZnO, ZnO:Cu (0.4 % at.) and ZnO:Cu (0.9 % at.) were lower (3.28 eV, 3.25 eV and 3.16 eV) than those reported for the ZnO bulk material (3.37 eV). Finally, the antifungal activity was tested against the fungus Aspergillus ochraceopetaliformis, and showed that the copper-doped nanoparticles had a higher inhibitory activity of up to 80 % on day 17 with concentrations of 9 and 12 mmol. The results suggest that it is possible to use the undoped/copper-doped ZnO Nps as antifungal agents against A. Ochraceopetaliformis.
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