77. Iron assisted Synthesis of highly Monodisperse and Magnetic Citrate-stabilized Small Silver Nanoparticles
Maria Blanco-Formoso, Mariacristina Turino, Beatriz Rivas-Murias, Luca Guerrini, Alexey Shavel, Roberto de la Rica, Miguel A. Correa-Duarte, Verónica Salgueiriño, Nicolás Pazos-Pérez and Ramón Álvarez-Puebla
J. Phys. Chem. C (2020), 124, 3270-3276 (DOI: 10.1021/acs.jpcc.9b10606).
Herein, we present an optimized bottom-up approach for the fabrication of homogeneous small spherical silver nanoparticles, with average diameter sizes ranging from 10 to 30 nm and the associated plasmon resonances located between 390 and 410 nm. The presented method relies on the use of tiny amounts of Fe(III) as silver dopant during the growth process, which enables the production of very homogeneous nanoparticles (standard deviations < 6%). The characterization of the obtained materials with surface-enhanced Raman scattering spectroscopy shows optical enhancing properties similar, or even better, than those observed with standard silver nanoparticles. Moreover, these noble nanomaterials are also endorsed with an intrinsic magnetic functionality.
76. Recent Advances in Nano- and Micromotors
Marina Fernández-Medina, Miguel A. Ramos-Docampo, Ondrej Hovorka, Verónica Salgueiriño and Brigitte Städler
Advanced Functional Materials (2020), 1908283 (DOI: 10.1002/adfm.201908283).
75. Partial FeO-Fe3O4 Phase Transition along the <111> Direction of the Cubic Crystalline Structure in Iron Oxide Nanocrystals
Martín Testa-Anta, Benito Rodríguez-González and Verónica Salgueiriño
Particle & Particle Systems Characterization (2019), 36, 1900283 (DOI: 10.1002/ppsc.201900283).
The iron oxide nanocrystals described herein stem from a ketonic decarboxylation reaction which fosters the delivery of -FeO- as an intermedium product. This intermedium product working as a monomer nucleates into FeO seeds which grow to attain a cubic shape with tips. This kinetically-controlled second stage of growth favors the deposition of -FeO- at the apexes and promotes a partial topochemical FeO to Fe3O4 phase transition mainly along the elongated <111> direction of the cubic crystalline structures.
74. Microswimmers with Heat Delivery Capacity for 3D Cell Spheroid Penetration
Miguel A. Ramos-Docampo, Marina Fernández-Medina, Essi Taipaleenmäki, Ondrej Hovorka, Verónica Salgueiriño and Brigitte Städler
ACS Nano (2019), 13, 12192-12205 (DOI: 10.1021/acsnano.9b06869).
We report microswimmers that employ collagen, a major extracellular matrix constituent, as fuel and that have the ability to deliver heat via incorporated magnetic nanoparticles when exposed to an alternating magnetic field. Their assembly and heating properties are outlined followed by the assessment of their calcium-triggered mobility in aqueous solution and collagen gels. Furthermore, the successful penetration of the swimmers into 3D cell spheroids upon exposure to the alternating magnetic field implies that the cell viability becomes impared due to the locally delivery heat.
73. Spin Frustration Drives Exchange Bias Sign Crossover in CoFe2O4-Cr2O3 Nanocomposites
Martín Testa-Anta, Beatriz Rivas-Murias, Verónica Salgueiriño
Advanced Functional Materials (2019), 1900030 (DOI: 10.1002/adfm.201900030).
A combined Raman spectroscopy and magnetometry study of CoFe2O4-Cr2O3 nanocomposites demonstrates the presence of spin-phonon interactions and exchange bias at the interface between the ferrimagnetic CoFe2O4 and the antiferromagnetic and magnetoelectric Cr2O3 phases. The pinned layer of uncompensated spins at the surface of the chromium oxide nanocrystals provides a source of unidirectional anisotropy and changes the sign of the exchange bias when transitioning from a canted to a frustrated situation, that is, as increasing the percentage of CoFe2O4 or decreasing the percentage of Cr2O3 in the composites. This assessment of the distinctive interfaces attained in the final oxide heterostructures offers a prospective route for hybrid materials on which upholding a magnetoelectric effect.