Lidia Martínez - Academia.edu (original) (raw)
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Papers by Lidia Martínez
The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) gr... more The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) grown using a gas-phase aggregation source and embedded in Au and V matrices is presented. We investigate how the matrix, the number of embedded nanoparticles (counted by coverage percentage), the interparticle interactions and the complex nanoparticles/matrix interface structure define the magnetic properties of the studied systems. A threshold coverage of 3.5% of a monolayer was found in both studied systems: below this coverage, nanoparticles behave as an assembly of independent single-domain magnetic entities with uniaxial anisotropy. Above the threshold it is found that the magnetic behavior of the systems is more matrix dependent. While magnetic relaxation and Henkel plots measurements stress the importance of the dipolar interactions and the formation of coherent clusters in the case of the Au matrix, the magnetic behavior of cobalt clusters embedded in the vanadium matrix is explained through the formation of a spin glass-like state at the V–Co interface that screens the magnetic interactions between NPs.
Materials Research Express, 2014
The Journal of Physical Chemistry C, 2013
Review of Scientific Instruments, 2011
Physical Chemistry Chemical Physics, 2013
Physical Chemistry Chemical Physics, 2010
Journal of Nanoparticle Research, 2011
Journal of Alloys and Compounds, 2009
European Biophysics Journal, 2010
CrystEngComm, 2011
ABSTRACT The extended use of self-assembling approaches for the generation of oxidenanostructures... more ABSTRACT The extended use of self-assembling approaches for the generation of oxidenanostructures with engineered functional properties firstly relies on the ability to control their growth processes. In this paper, we focus on the growth of Ce1−xGdxO2−y (CGO) nanoislands on ABO3 substrates (i.e. LaAlO3 (LAO)) as a model system to investigate the nucleation and kinetic evolution of epitaxial nanostructures grown by high-throughput ex situ methods based on chemical solution deposition. Fine-tuning of growth conditions enables us to select the crystallographic orientation of CGO leading to two systems with different equilibrium shapes and kinetics. Self-assembled (001)CGO‖(001)LAOnanostructures grow with stable uniform square-based nanopyramid shape, whereas the nucleation of (011)CGO‖(001)LAO leads to highly elongated nanowires with enhanced diffusive mobility. At high temperatures, shape selection is merely achieved through a modified growth atmosphere (oxidizing or reducing). However, a temperature-induced nucleation orientation crossover occurs under the reducing growth atmosphere, allowing the tuning of a nanodot-to-nanowire ratio through kinetic control. We prove by XPS that an enhanced concentration of oxygen vacancies in the nanowires is linked to their ultrafast coarsening. The nucleation processes are scrutinized through thermodynamic analysis, and it is concluded that the supersaturation degree controls the nanoislands' orientation.
Applied Surface Science, 2010
![Research paper thumbnail of X-ray absorption and magnetic circular dichroism characterization of a novel ferromagnetic MnN[sub x] phase in Mn/Si[sub 3]N[sub 4] multilayers](https://attachments.academia-assets.com/43352509/thumbnails/1.jpg)
](Applied Physics Letters, 2008
Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (... more Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (DLC) coatings in order to modify their surface and tribological properties. Measurements of water contact angle were performed by the sessile drop method and showed that the coated samples are more hydrophobic with water contact angles up to 116°. The surface free energy of the elastomers was calculated by the acid–base regression method considering polar and dispersive contributions and the results were correlated with changes in the surface chemistry measured by X-ray photoelectron spectroscopy. It has been found that the lower presence of oxygen functional groups on the elastomer surfaces led to lower surface free energies, even though the polar contribution was not predominant. We also found that the DLC coatings led to a significant decrease of the surface free energy (up to 16%) and that there is a good correlation between the surface free energy values and the corresponding water contact angle values. The coefficient of friction was also measured and presented a significant decrease after coating with DLC.
The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) gr... more The study of the magnetic properties of Co nanoparticles (with an average diameter of 10.3 nm) grown using a gas-phase aggregation source and embedded in Au and V matrices is presented. We investigate how the matrix, the number of embedded nanoparticles (counted by coverage percentage), the interparticle interactions and the complex nanoparticles/matrix interface structure define the magnetic properties of the studied systems. A threshold coverage of 3.5% of a monolayer was found in both studied systems: below this coverage, nanoparticles behave as an assembly of independent single-domain magnetic entities with uniaxial anisotropy. Above the threshold it is found that the magnetic behavior of the systems is more matrix dependent. While magnetic relaxation and Henkel plots measurements stress the importance of the dipolar interactions and the formation of coherent clusters in the case of the Au matrix, the magnetic behavior of cobalt clusters embedded in the vanadium matrix is explained through the formation of a spin glass-like state at the V–Co interface that screens the magnetic interactions between NPs.
Materials Research Express, 2014
The Journal of Physical Chemistry C, 2013
Review of Scientific Instruments, 2011
Physical Chemistry Chemical Physics, 2013
Physical Chemistry Chemical Physics, 2010
Journal of Nanoparticle Research, 2011
Journal of Alloys and Compounds, 2009
European Biophysics Journal, 2010
CrystEngComm, 2011
ABSTRACT The extended use of self-assembling approaches for the generation of oxidenanostructures... more ABSTRACT The extended use of self-assembling approaches for the generation of oxidenanostructures with engineered functional properties firstly relies on the ability to control their growth processes. In this paper, we focus on the growth of Ce1−xGdxO2−y (CGO) nanoislands on ABO3 substrates (i.e. LaAlO3 (LAO)) as a model system to investigate the nucleation and kinetic evolution of epitaxial nanostructures grown by high-throughput ex situ methods based on chemical solution deposition. Fine-tuning of growth conditions enables us to select the crystallographic orientation of CGO leading to two systems with different equilibrium shapes and kinetics. Self-assembled (001)CGO‖(001)LAOnanostructures grow with stable uniform square-based nanopyramid shape, whereas the nucleation of (011)CGO‖(001)LAO leads to highly elongated nanowires with enhanced diffusive mobility. At high temperatures, shape selection is merely achieved through a modified growth atmosphere (oxidizing or reducing). However, a temperature-induced nucleation orientation crossover occurs under the reducing growth atmosphere, allowing the tuning of a nanodot-to-nanowire ratio through kinetic control. We prove by XPS that an enhanced concentration of oxygen vacancies in the nanowires is linked to their ultrafast coarsening. The nucleation processes are scrutinized through thermodynamic analysis, and it is concluded that the supersaturation degree controls the nanoislands' orientation.
Applied Surface Science, 2010
Applied Physics Letters, 2008
Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (... more Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (DLC) coatings in order to modify their surface and tribological properties. Measurements of water contact angle were performed by the sessile drop method and showed that the coated samples are more hydrophobic with water contact angles up to 116°. The surface free energy of the elastomers was calculated by the acid–base regression method considering polar and dispersive contributions and the results were correlated with changes in the surface chemistry measured by X-ray photoelectron spectroscopy. It has been found that the lower presence of oxygen functional groups on the elastomer surfaces led to lower surface free energies, even though the polar contribution was not predominant. We also found that the DLC coatings led to a significant decrease of the surface free energy (up to 16%) and that there is a good correlation between the surface free energy values and the corresponding water contact angle values. The coefficient of friction was also measured and presented a significant decrease after coating with DLC.