A nanostructured material is nowadays a broad term used to refer to materials
that have been either patterned or have structural features in the nanometer
(nm) scale. The second approach is the one that allows achieving smaller
features (i.e. dimensions below 10 nm) and has been the most widely used in the
past for producing nanocrystalline segregation that eventually lead to a 3D
network of nanocrystallites with no organization.
More recent and versatile approaches lead to artificial structures such as nm
thick multi-layers (i.e. 1D nanometer control), nm sized objects embedded in a
host and organised in layers (i.e. 2D nanometer control) or the most complete 3D
control in which the organization of the nano-objects within the layer is in
We use the term nanostructuring for the last two approaches in which
nano-objects with controlled features smaller than 10 nm are embedded in a host
and organised. So far, results from resecrah conducted by Professor Carmen N.
Afonso and her colleagues at Instituto de Optica - Consejo Superior de Investigaciones
Científicas (CSIC) have demonstrated that the 2 D control is a very
promising tool for both understanding fundamental interaction phenomena as well
as enhance materials performance. This has been demonstrated for systems having
layers whose separation is controlled down to ~ 1 nm, the layers being formed by
either metal nanoparticles or rare-earth ions.
The design of these artificially engineering materials in the nanoscale can
be tailored to applications in many fields. The main interest of Professor Carmen
N. Afonso and her colleagues has been on optical applications and thus we
focused on systems formed by metal nanoparticles with dimensions < 10 nm or
rare-earth ions embedded in dielectric media with their distribution controlled
in-depth within a few nm. The former system has several applications mainly
related to its surface plasmon resonance features.
In addition, the nano-objects are large enough as to be imaged by electron
microscopy related techniques as shown in the figure and thus prove the concept.
The figure shows from left to right: cross-section and plan view images of a
specimen containing metal nanoparticles organised in equally spaced layers;
cross-section and plan view images of a specimen containing pairs of large and
small nanoparticle layers with controlled separation, the two layers being
appreciated in the plan view as a bi-modal distribution of large and small
nanoparticles; and a cross-section image of a specimen containing layers with
This approach has allowed Professor Carmen N. Afonso and her colleagues among others, to
reduce the absorption of nanocomposite materials in the neighbourhood of the
surface plasmon resonance by choosing an appropriate organisation of the
layers1 or demonstrating the optical activation (in
the visible) of magnetic nanoparticles through neighbouring silver nanoparticles
for a separation of ~ 4 nm.2
The concept has been extended to rare-earth (RE) ion doping, i.e. the
nanostructuring is achieved by organizing the RE ions in layers similarly to the
case of metal NPs but the ion layer concentration being two orders of magnitude
smaller than that of the metal in the case of nanoparticles.
The nanostructuring approach has been used to optimise key material
performance parameters for achieving optical gain at communications wavelength,
i.e. lifetime (through the Er-Er separation)3,
intensity (through Yb to Er separation)4 or
bandwidth (through Tm to Er separation)5.
Additionally, it has been proved an excellent approach to enhance the frequency
conversion capability of LiNbO3 films.6
1. A. Suarez-Garcia, R. del Coso, R. Serna, J. Solis, and C. N.
Afonso, "Controlling the transmission at the surface plasmon resonance of
nanocomposite films using photonic structures," Applied Physics Letters 83,
2. J. Margueritat, J. Gonzalo, C. N. Afonso,
U. Hormann, G. Van Tendeloo, A. Mlayah, D. B. Murray, L. Saviot, Y. Zhou, M. H.
Hong, and B. S. Luk'yanchuk, "Surface enhanced Raman scattering of silver
sensitized cobalt nanoparticles in metal-dielectric nanocomposites,"
Nanotechnology 19, 375701 (2008)
3. R. Serna, M. J. de Castro,
J. A. Chaos, A. Suarez-Garcia, C. N. Afonso, M. Fernandez, and I. Vickridge,
"Photoluminescence performance of pulsed-laser deposited Al2O3 thin films with
large erbium concentrations," Journal of Applied Physics 90, 5120-5125
4. A. Suarez-Garcia, R. Serna, M. J. de Castro, C. N.
Afonso, and I. Vickridge, "Nanostructuring the Er-Yb distribution to improve the
photoluminescence response of thin films," Applied Physics Letters 84, 2151-2153
5. Z. S. Xiao, R. Serna, and C. N. Afonso, "Broadband
emission in Er-Tm codoped Al2O3 films: The role of energy transfer from Er to
Tm," Journal of Applied Physics 101, 033112 (2007)
Gonzalo, J. A. Chaos, A. Suarez-Garcia, C. N. Afonso, and V. Pruneri, "Enhanced
second-order nonlinear optical response of LiNbO3 films upon Er doping," Applied
Physics Letters 81, 2532-2534 (2002)
Copyright AZoNano.com, Professor Carmen N. Afonso (Instituto de
Optica - Consejo Superior de Investigaciones Científicas (CSIC))
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