Victor Puntes

Peptides as capping ligands for in situ synthesis of water soluble Co nanoparticles for bioapplications

For the first time peptides were used as capping ligands for in situ synthesis of water-soluble cobalt nanoparticles (NP) with the aim to use these particles for biological applications. In this paper, we describe the synthetic method, and characterization of the samples by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometry. The peptides were found to facilitate the formation of nanoparticles and partly protect the nanoparticles from oxidation.

A new synthetic route to produce metal zeolites with subnanometric magnetic clusters

By using a Co layered silicate as a source of Co and SiO(2), Co-Beta and Co-ZSM-5 zeolites with tetrahedrically coordinated cobalt were synthesized. Subnanometric clusters of Co can be produced and a magnetic material with superparamagnetic-paramagnetic phase transition is obtained.

The Reactivity of Colloidal Inorganic Nanoparticles

The development of functional colloidal inorganic nanoparticles (INPs) has increased exponentially over the past decades offering a toolbox ready to be used in a wide range of applications such as materials science, catalysis, biology and medicine (Freitas, 1999; Alivisatos, 2001). This applicability relies on their unique size, morphology and structure, which determines not only their properties but also its reactivity. At the nanometer scale, the confinement of electrons, phonons and photons leads to a new generation of materials which have improved or new physico-chemical properties in comparison with bulk materials. Well-known examples are the size and shape dependence absorption and scattering in noble metal INPs (e.g. Au or Ag), the enhanced fluorescence in semiconductor quantum dots (QDs) (e.g. CdSe or PbS ) and the superparamagnetic moment in magnetic NPs (e.g. iron oxide or cobalt) (Burda et al., 2005). Additionally, as the size of the material is reduced and percentage of atoms at the surface becomes significant, the entire particles become more reactive (Bastus et al., 2008). Thus, in very small crystals, both the thermodynamics and kinetics of reactions can change with size. For instance, a large surface-to-volume ratio can be accompanied by a lowering of phase transition temperatures (Goldstein et al., 1992). Additionally, this high fraction of unsaturated atoms at INPs surface may lead to some instabilities which can further lead to degradation and corrosion processes. Although this secondary processes are often uncontrollable, the feature is extremely useful for catalysis applications (e.g. Pt NPs) allowing reactions at the active sites of their surfaces (Li & Somorjai, 2010).