Scientific Papers in SCI

Two gold-based catalysts were obtained by Au chemical reduction of the HAuCl(4 )precursor. The resulting nanoparticles were stabilized and immobilized on montmorillonite (Mt) and montmorillonite-ceria (Mt/CeO2). All prepared catalysts were active in 4-nitrophenol to aminophenol reduction at room temperature. Synergy between montmorillonite and ceria is postulated in such a way that the montmorillonite phase hinders particle growth either by influencing the nucleation behavior of gold or by increasing the number of nucleation sites and raising the overall dispersion. The role of the ceria support, on the other hand, may be associated with the 4-NP adsorption at the ceria-gold interface, stabilizing the reaction intermediate and hence lowering the activation barrier for the reduction of 4-NP to 4-AP. 

Traditionally porous silicon based photonic structures have been prepared by electrochemically etching of silicon. In this work, porous multilayers of nanocolumnar SiOx and SiO2 thin films acting as near infrared (NIR) 1D-photonic nanostructures are prepared by magnetron sputtering deposition at oblique angles (MS-OA). Simultaneous control of porosity and stoichiometry of the stacked films is achieved by adjusting the deposition angle and oxygen partial pressure according to a parametric formula. This new methodologoy is proved for the synthesis of SiOx thin films with x close to 0.4, 0.8, 1.2, 1.6 and nanostructures varying from compact (at 0 degrees deposition angle) to highly porous and nanocolumnar (at 70 degrees and 85 degrees deposition angles). The strict control of composition, structure and nanostructure provided by this technique permits a fine tuning of the absorption edge and refraction index at 1500 nm of the porous films and their manufacturing in the form of SiOx-SiO2 porous multilayers acting as near infrared (NIR) 1D-photonic structures with well-defined optofluidic responses. Liquid tunable NIR Bragg mirrors and Bragg microcavities for liquid sensing applications are presented as proof of concept of the possibilities of this MS-OA manufacturing method as an alternative to the conventional electrochemical fabrication of silicon based photonic structures.