Light-emitting nanocomposite cds-polymer electrospun fibres via in-situ nanoparticle generation

We report on the simple, in situ generation of CdS nanocrystals inside electrospun polymer fibres by thermal decomposition of a cadmium thiolate precursor, leading to nanocomposite light-emitting fibres. The modifications induced in the precursor by the thermal decomposition are investigated by a morphological, structural and spectroscopic analysis of the resulting nanocomposite fibres. This approach allows us to overcome nanofabrication difficulties related to disfavoured micro- or nanofluidic molecular flow as given by the direct incorporation of particles in the electrospinning solution. This method therefore enables the synthesis of luminescent, CdS-based composite fibres with emission peaked in the visible range, suitable as building blocks for nanophotonic devices based on light-emitting nanomaterials

Role of substrate on nucleation and morphology of gold nanoparticles produced by pulsed laser deposition

This work compares the morphology of gold nanoparticles (NPs) produced at room temperature on single-crystalline (MgO nanocubes and plates) and amorphous (carbon/glass plates) substrates by pulsed laser deposition (PLD). The results show that similar deposition and nucleation rates (>5× 1013 cm-2 s-1) are achieved irrespective of the nature of the substrate. Instead, the shape of NPs is substrate dependent, i.e., quasispheres and faceted NPs in amorphous and single-crystalline substrates, respectively. The shape of the latter is octahedral for small NPs and truncated octahedral for large ones, with the degree of truncation being well explained using the Wulff-Kaichew theorem. Furthermore, epitaxial growth at room temperature is demonstrated for single-crystalline substrate. The large fraction of ions having energies higher than 200 eV and the large flux of species arriving to the substrate (1016 at. cm-2 s-1) involved in the PLD process are, respectively, found to be responsible for the high nucleation rates and epitaxial growth at room temperature. © 2009 The American Physical Society.This work has partially been supported by EU Grant No. HPRN-CT-2002-00328 and MEC Spain Grant No. MAT2005-06508-C02-01 .Peer Reviewe

The importance of the energetic species in pulsed laser deposition for nanostructuring

This work reports on the optical and structural properties of nanostructured films formed by Ag nano-objects embedded in amorphous aluminium oxide (a-Al 2O 3) prepared by alternate pulsed laser deposition (PLD). The aim is to understand the importance of the energetic species involved in the PLD process for nanostructuring, i.e.for organizing nanoparticles (NPs) in layers or for self-assembling them into nanocolumns (NCls), all oriented perpendicular to the substrate. In order to change the kinetic energy of the species arriving at the substrate, we use a background gas during the deposition of the embedding a-Al 2O 3 host. It was produced either in vacuum or in a gas pressure (helium and argon) while the metal NPs were always produced in vacuum. The formation of NPs or NCls is easily identified through the features of the surface plasmon resonances (SPR) in the extinction spectra and confirmed by electron microscopy. The results show that both the layer organization and self-assembling of the metal are prevented when the host is produced in a gas pressure. This result is discussed in terms of the deceleration of species arriving at the substrate in gas that reduces the metal sputtering by host species (by ≈58%) as well as the density of the host material (by 19%). These reductions promote the formation of large voids along which the metal easily diffuses, thus preventing organization and self-organisation, as well as an enhancement of the amount of metal that is deposited. © 2012 IOP Publishing Ltd.Peer Reviewe

Control of self-organised metal nanostructures through the kinetic energy of host species

10th International Conference on Laser Ablation, Singapore, November 22-27, 2009N

Coverage induced regulation of Au nanoparticles during pulsed laser deposition

The effects induced during the covering/embedding of metal nanoparticles (NPs) produced by pulsed laser deposition (PLD) and their impact on the structural and optical properties have been studied by producing pairs of samples containing Au NPs that are either uncovered (i.e., at the surface) or covered (i.e., embedded in an amorphous a-Al2O3 host). The main result is that covering species can sputter up to 100% of the Au atoms, the smaller the NPs the higher the sputtered fraction. This fraction has been simulated using standard models for ion bombardment and taking into account the kinetic energy distribution of arriving species and the cohesive energy dependence on NPs dimensions. Although all models well predict the order of magnitude of the sputtering yield, the calculated values are generally smaller than the experimental ones and do not account for the experimental dependence on NPs dimensions. This disagreement is discussed in terms of the limitations of standard models that do not take into account the lower adhesion of small NPs to the substrate, the high flux of species involved in PLD and, possibly to lesser extent, the use of some bulk material parameters. The metal sputtering during the coverage regulates the NPs morphology, through a reduction of dimensions and dimension dispersion. Most changes of structural features and optical spectra when covering the NPs are directly related to the variation in the amount of metal with the exception of a strong blueshift of the surface plasmon resonance when NPs are covered. This shift could be consistent with mixing of covering layer species and metal at the surface of the NPs. © 2011 American Institute of Physics.This work was partially supported by MAT2009-14282- C02-01 (Spain).Peer Reviewe

Role of substrate on nucleation and morphology of gold nanoparticles produced by pulsed laser deposition

This work compares the morphology of gold nanoparticles NPs produced at room temperature on singlecrystalline MgO nanocubes and plates and amorphous carbon/glass plates substrates by pulsed laser deposition PLD. The results show that similar deposition and nucleation rates 51013 cm−2 s−1 are achieved irrespective of the nature of the substrate. Instead, the shape of NPs is substrate dependent, i.e., quasispheres and faceted NPs in amorphous and single-crystalline substrates, respectively. The shape of the latter is octahedral for small NPs and truncated octahedral for large ones, with the degree of truncation being well explained using the Wulff-Kaichew theorem. Furthermore, epitaxial growth at room temperature is demonstrated for single-crystalline substrate. The large fraction of ions having energies higher than 200 eV and the large flux of species arriving to the substrate 1016 at. cm−2 s−1 involved in the PLD process are, respectively, found to be responsible for the high nucleation rates and epitaxial growth at room temperature

Metal-hydride transformation Kinetics in Mg nanoparticles

The hydrogen sorption kinetics of magnesium nanoparticles prepared by inert gas condensation and coated by a magnesium oxide layer were investigated by a volumetric apparatus. The metal-hydride transformation was studied by transmission electron microscopy of the nanoparticles both in the as prepared state and after hydrogen cycling