RESUMEN
In the present work, the magnetron sputtering technique was used to prepare new catalysts of formic acid electrooxidation based on TiO2 nanotubes decorated with Pt (platinum), Pd (palladium) or Pd + Pt nanoparticles. TiO2 nanotubes (TiO2 NTs) with strictly defined geometry were produced by anodization of Ti foil and Ti mesh in a mixture of glycerol and water with ammonium fluoride electrolyte. The above mentioned catalytically active metal nanoparticles (NPs) were located mainly on the top of the TiO2 NTs, forming 'rings' and agglomerates. A part of metal nanoparticles decorated also TiO2 NTs walls, thus providing sufficient electronic conductivity for electron transportation between the metal nanoparticle rings and Ti current collector. The electrocatalytic activity of the TiO2 NTs/Ti foil, decorated by Pt, Pd and/or Pd + Pt NPs was investigated by cyclic voltammetry (CV) and new Pd/TiO2 NTs/Ti mesh catalyst was additionally tested in a direct formic acid fuel cell (DFAFC). The results so obtained were compared with commercial catalyst-Pd/Vulcan. CV tests have shown for carbon supported catalysts, that the activity of TiO2 NTs decorated with Pd was considerably higher than that one decorated with Pt. Moreover, for TiO2 NTs supported Pd catalyst specific activity (per mg of metal) was higher than that for well dispersed carbon supported commercial catalyst. The tests at DFAFC have revealed also that the maximum of specific power for 0.2 Pd/TiO2 catalyst was 70% higher than that of the commercial one, Pd/Vulcan. Morphological features, and/or peculiarities, as well as surface composition of the resulting catalysts have been studied by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and chemical surface analytical methods (X-ray photoelectron spectroscopy-XPS; Auger electron spectroscopy-AES).
RESUMEN
Deposition of plazmonic metal nanoparticles on nanostructured oxide templates is an important part in preparation and design of suitable substrates for surface-enhanced Raman scattering (SERS) measurements. In this contribution we analyze the influence of the Ag deposition methods (magnetron sputtering and evaporation in vacuum, which are often used interchangeably) on SERS activity of the resultant Ag-n/ZrO2/Zr composite samples fabricated. We found that deposition of the same amount of Ag (0.020mg/cm2) on the ZrO2 nanoporous layers using magnetron sputtering and evaporation in vacuum leads to formation of two different surface morphologies, which can be distinguished on the basis of high-resolution scanning electron microscopy (HR-SEM) measurements. Those differences distinctly affect SERS intensity measured for probe molecules: pyridine and sodium 2-mercaptoethanesulfonate. SERS substrates obtained using evaporation technique are ca. 1.5 times more efficient than substrates prepared using magnetron sputtering.
RESUMEN
The new generation of medical implants made by titanium is functionalized with different coatings to improve their bioactivity and reduce a risk of infection. This article describes how these goals can be achieved via deposition of silver nanoparticles and calcium phosphate coating. TiO(2) nanotubes were grown on a Ti substrate via electrochemical oxidation at constant voltage in a mixture of glycerol, deionized water, and NH(4) F. Silver particles with a size of 2-50 nm were deposited on the surface using the sputter deposition technique. Calcium phosphate coatings were grown on the nanotubular titania by simple immersion in Hanks' solution. It has been found that the silver nanoparticles are distributed homogeneously in the coating, which is promising for maintaining a steady antibacterial effect. The results show also that the Ag-incorporated TiO(2) nanotubes significantly stimulate apatite deposition from Hanks' solution. The highly ordered Ag-incorporated TiO(2) nanotube arrays with apatite coating may offer unique surface features for biomedical implants, ensuring both biocompatibility and antibacterial properties.
