82. Unraveling the Multi-featured Magnetic Behavior of Nd0.75Sr0.25CoO3 Perovskite Nanocrystals annealed at different Temperatures
Hajer Chouaibi, Beatriz Rivas-Murias, Mourad Smari, Jalel Massoudi, Essebti Dhahri and Verónica Salgueiriño
Journal of Alloys and Compounds (2021), 874, 159870 (DOI: 10.1016/j.jallcom.2021.159870).
Perovskite nanocrystals are gaining increased attention because of their magnetic, transport and catalytic properties, and particularly there is a renewable interest of cobalt perovskites for catalysis. Accordingly, the correct interpretation of their properties stemming from a particular configuration of the cations within this crystalline structure is compulsory. Herein, we report the synthesis of Nd0.75Sr0.25CoO3 nanocrystals using the citrate sol-gel method and annealed at different final temperatues (600 °C, 700 °C, 800 °C and 1150 °C). Their characterization was carried out combining transmission electron microscopy, X-ray diffraction, Raman spectroscopy and vibrating sample magnetometry, demonstrating their complementarity to get the whole picutre of the multi-featured perovskite-based nanocrystal behavior.
81. A Caging Strategy for tuning the Magneto-Optical Properties of Cobalt Ferrite using a Single Plasmonic Nanoparticle
Martín Testa-Anta, Ana Sousa-Castillo, Alberto López-Ortega, Miguel A. Correa-Duarte, Antonio García-Martín, Paolo Vavassori and Verónica Salgueiriño
Journal of Materials Chemistry C (2021), 9, 5098-5104 (DOI: 10.1039/d1tc00580d).
The composite nanostructures with magnetic and plasmonic functionalities herein described were produced according to a unique synthetic strategy by which numerous cobalt ferrite nanoparticles accompanied by an individual gold nanoparticle were confined in silica capsules. This assembly offers a distinctive system on which the influence of the surface plasmon of a single 20 or 60 nm-in-diameter gold nanoparticle is proved to increase the visible range magneto-optical activity of the cobalt ferrite magnetic material. Consequently, it provides a key strategy for the production of nanostructures including different materials as building blocks, taking advantage of the confined coupling for the development of materials with enhanced magneto-optical capabilities.
80. Impact of Citrate and Lipid-Functionalized Magnetic Nanoparticles in Dehydropeptide Supramolecular Magnetogels: Properties, Design and Drug Release
Sergio Veloso, Joana Silva, Loic Hilliou, Cacilda Moura, Paulo Coutinho, José A. Martins, Martín Testa-Anta, Verónica Salgueiriño, Miguel A. Correa-Duarte, Paula Ferreira, Elisabete Castanheira
Nanomaterials (2021), 11, 16 (DOI: 10.3390/nano11010016).
Two different functionalized nanoparticles: citrate-stabilized and lipid-coated magnetic nanoparticles were used for the formation of dehydropeptide-based supramolecular magnetogels consisting of the ultra-short hydrogelator Cbz-L-Met-Z-ΔPheOH. While the lipid-coated nanoparticles were distributed along the hydrogel fibers, the citrate-stabilized nanoparticles were aggregated upon gelation, which resulted in different heating efficiency.
79. Structural and Magnetic Implications of Transition Metal Migration within Octahedral Core-Shell Nanocrystals
Beatriz Rivas-Murias, Martín Testa-Anta, Pau Torruella, Sònia Estradé, Francesca Peiró, Benito Rogríguez-González, Miguel Comesaña-Hermo and Verónica Salgueiriño
Chemistry of Materials (2020), 32, 10435-10446 (DOI: 10.1021/acs.chemmater.0c03017).
Octahedron-shaped cobalt oxide nanocrystals undergo a structural evolution once coated with thin shells of manganese or cobalt ferrite, by means of an asymmetric solid-solid diffusion occurring at the interface established between the oxides. The resultant mixed ferrites in the final nanostructures stem from the phase progression associated with a nonequilibrium kinetic product that evolves to reach the thermodynamic equilibrium. In this process, the initially strained crystalline lattice closer to the interface influences the progressive redistribution of Co2+ catoins diffusing out of the initial cobalt oxide core, dictating the final magnetic properties. When starting with a nonstoichiometric manganese ferrite shell, the preferential occupation of tetrahedral sites by Mn2+ cations forces the Co2+ to occupy octahedral sites, offering a Mn- and Co-doped magnetite shell onto the CoO core. However, when starting with a cobalt ferrite shell, an extra doping of Co2+ cations in the strained layers close to the interface forces this ferrite to transition from the inverse to the normal spienl structure, leading to core-shell nanocrystlas of CoO and Co-rich cobalt ferrite with an enhanced magnetic moment.
78. Magnetically Induced CO2 Methanation using Exchange-coupled Spinel Ferrites in Cuboctahedron-shaped Nanocrystals
Beatriz Rivas-Murias, Juan M. Asensio, Nicolas Mille, Benito Rogríguez-González, Pier-Francesco Fazzini, Julian Carrey, Bruno Chaudret and Verónica Salgueiriño
Angewandte Chemie I. Ed. (2020) 59, 15537-15542 (DOI: 10.1002/anie.202004908).
Magnetically induced catalysis can be promoted taking advantage of optimal heating properties from the magnetic nanoparticles to be employed. However, when unprotected, these heating agents that are usually air-sensitive, get sintered under the harsh catalytic conditions. In this context, we present, to the best of our knowlege, the first example of air-stable magnetic nanoparticles that: 1) show excellent performance as heating agents in the CO2 methanation catalyzed by Ni/SiRAlOx, with CH4 yields above 95%, and 2) do not sinter under reaction conditions. To attain both characteristics we demonstrate, first the exchange-coupled magnetic approach as an alternative and effective way to tune the magnetic response and heating efficiency, and second, the chemical stability of cuboctahedron-shaped core-shell hard CoFe2O4 - soft Fe3O4 nanoparticles.