Uvigo


General Overview of our Research


Our research is basically focussed on the synthesis, characterization and applications of nanoparticles and assemblies thereof. Core-shell nanoparticles are our favourite systems, so that we can control the properties of the colloid by means of careful modification of the dimensions of the core-shell geometry and of the nature of both the core and the shell. By chosing an insulating material as the shell, we can build up nanostructures, both in 2D and 3D, where the spacing between neighboring particles is determined by the thickness of the shell. Such a lattice control permits us to tailor the properties of the nanostructures. We search for applications mainly on magnetic and optical properties.

For references, see the Publications page.


Nanoparticle synthesis: size and shape control
Plasmonics of metal nanoparticles
Nanoparticle assemblies
Composite colloids
Evaluation of the optical enhancing properties of nanoparticles and nanoparticle arrays
Integration of nanoparticles into complex sensors for environmental pollution monitoring diagnosis and biodetection
Reactivity in nanoheterogeneous media



Nanoparticle synthesis: size and shape control


Morphology control in the nanoscale is a hot topic because of the spectacular effects that small changes in the shape of nanoparticles have on a variety of physical (optical, magnetic, electronic...) properties of the material. Colloidal synthesis has proven extremely useful to prepare a wide variety of nanoparticles with tight control of size and shape. Still, much of the knowledge in this area is empirical and no general rules can be provided for a rational nanomaterial design. We are particularly interested in understanding the mechanisms involved in nanoparticle growth, which determine the final size and shape. Though eminently fundamental, this research is required for the design of nanoparticle materials with tailored properties that can be used for practical applications.
Examples of nanoparticles with various morphologies are shown in our picture gallery.

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Plasmonics of metal nanoparticles


Nanoparticles of noble metals (Au, Ag, Cu) display very interesting optical properties due to so-called surface plasmon resonances, which involve the collective oscillation of conduction electrons in resonance with the alternating electric field of incident electromagnetic radiation, as sketched below.

The frequency of the surface plasmon mainly depends on the nature (dielectric function) of the metal, but is largely affected by the size and shape of the nanoparticles, or by their dielectric environment, among other parameters. Such resonances result in bright colours, as well as large enhancements of the electric field around the particles.
One of the main interests of our group is the fine tuning of the optical response of metal nanoparticles with tailored composition, size and shape. Characterization of plasmon modes is carried out both for

Examples of nanoparticles and their colours are shown in our picture gallery. For more information, see a recent review.

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Nanoparticle assemblies


The preparation of thin films is based in the layer-by-layer assembly method, which is sketched below. The (negatively charged) substrate (1) is first dipped in a solution of a positively charged polyelectrolyte (2), so that a first monolayer is deposited. Then the modified substrate is immersed in a colloid of negatively charged nanoparticles (3), which attach due to electrostatic interactions. The process can be repeated in a cyclic fashion to build multilayers.

For AFM pictures of the films, visit our picture gallery.

Applications of these films can be found in the magnetic storage technology, since the decoupling between magnetic moments provided by the insulating layer implies a reduction of the noise to signal ratio.

The same methodology can also be applied to assemble nanoparticles on larger colloidal templates, which we have applied to assemble metal nanoparticles on latex spheres and carbon nanotubes. A few examples of TEM images are shown in our picture gallery as well.

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Composite colloids


This area of research focuses on the synthesis of nanoparticles or larger colloids comprising multiple functionalities, typically magnetic and optical, for applications either in nanoparticle directed assembly and orientation, or for biomedical uses, such as biolabelling and hyperthermia. We follow various approaches, either through seeded growth or through assembly of the components in the colloidal dispersion. Assembly typically involves using polyelectrolytes or other types of surface modification of the larger substrate.

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Evaluation of the optical enhancing properties of nanoparticles and nanoparticle arrays

Surface enhanced spectroscopies (SERS, SEF and SEIRA), with detection limits down to the single molecule regime, are known to be the ultimate analytical tools. This family of techniques is also called plasmon assisted spectroscopies because of the need of metallic nanoparticles to provide the electromagnetic field necessary for optical enhancement. Key aspects of the enhancing activity of nanostructures are related with size, shape, composition and surface chemistry of the nanoparticles. In this research line, we evaluate the suitability of different colloids for SES and direct sensing.

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Integration of nanoparticles into complex sensors for environmental pollution monitoring diagnosis and biodetection

Besides direct approaches in the evaluation of components in a given sample, other powerful approaches include indirect detection by taking advantage of the spectroscopic properties of certain molecular systems. The fabrication of hybrid systems based on nanoparticles is taking prominence as a method for the fabrication of complex sensor elements based on recognition events (key-and-lock sensors) or indirect interactions (cross-reactive arrays). In this research line, we investigate new sensing technologies by using SPR and SES with applications in high-throughput screening and real time analysis.

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Reactivity in in nanoheterogeneous media

We study the capability of different nanoheterogeneous systems such as micelles, microemulsions, vesicles and metallic nanoparticles to modulate chemical reactions, focusing in their kinetic aspects; catalytic activity and changes in the reaction mechanisms.

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