Role of Surfaces in the Magnetic and Ozone Gas-Sensing Properties of ZnFe₂O₄ Nanoparticles: Theoretical and Experimental Insights

Abstract

The magnetic properties and ozone (O3) gas-sensing activity of zinc ferrite (ZnFe2O4) nanoparticles (NPs) were discussed by the combination of the results acquired by experimental procedures and density functional theory simulations. The ZnFe2O4 NPs were synthesized via the microwave-assisted hydrothermal method by varying the reaction time in order to obtain ZnFe2O4 NPs with different exposed surfaces and evaluate the influence on its properties. Regardless of the reaction time employed in the synthesis, the zero-field-cooled and field-cooled magnetization measurements showed superparamagnetic ZnFe2O4 NPs with an average blocking temperature of 12 K. The (100), (110), (111), and (311) surfaces were computationally modeled, displaying the different undercoordinated surfaces. The good sensing activity of ZnFe2O4 NPs was discussed in relation to the presence of the (110) surface, which exhibited low (−0.69 eV) adsorption enthalpy, promoting reversibility and preventing the saturation of the sensor surface. Finally, the O3 gas-sensing mechanism could be explained based on the conduction changes of the ZnFe2O4 surface and the increase in the height of the electron-depletion layer upon exposure toward the target gas. The results obtained allowed us to propose a mechanism for understanding the relationship between the morphological changes and the magnetic and O3 gas-sensing properties of ZnFe2O4 NPs.

Detailed Structural Features of the Perovskite-Related Halide RbPbI3 for Solar Cell Applications

“…These powders resulting from ball milling can be dispersed in a particular medium (e.g., isopropyl alcohol) in order to be used for drop-coating-based thin films 42 or spin-coating technique. 43 As the stability of the powder sample is higher than that compared to the solvent-based method, as reported previously by our group, 44 there is a good chance that the thin films could also show an enhanced stability.…”

Interaction between Filler and Polymeric Matrix in Nanocomposites: Magnetic Approach and Applications

“…This change is fundamental since superparamagnetic behavior originates in NPs, which is defined by having a high magnetic susceptibility [95], but with the characteristic of being of turning the spins randomly under the influence of temperature. Moreover, magnetic nanoparticles also exhibit other interesting structural, optical, electrical, and gas sensing properties, which have been extensively reported in the literature [100][101][102].…”

Unconventional Disorder by Femtosecond Laser Irradiation in Fe2O3

“…The advance of the simulation of the magnetic properties in surfaces progressed in the last years. − Thus, to deeply investigate the magnetic properties of the α-Fe 2 O 3 and ε-Fe 2 O 3 morphologies, it is essential to know the magnetization index ( M ) in each ( hkl ) Miller index. To reach this goal, we applied a recent and innovative method. − In the first stage, the magnetization index ( D μ ) of a given ( hk l) surface (eq ) is calculated, where D μ is connected to the magnetic moment (μ B ) in a particular ( hkl ) surface per unit cell area ( A ).…”