In this work, the preparation of regular nanosized columnar structures of titanium dioxide by means of glancing angle deposition with magnetron sputtering (MS‐GLAD) followed by thermal annealing is reported. MS‐GLAD gives rise to metallic titanium columnar structures with regular width and length that after thermal treatment are fully oxidized to form TiO2 nanocolumns that maintain the morphological features of the original metallic ones. Further functionalization with gold by means of multiple ion cluster source results in well‐dispersed Au nanoparticles across the nanocolumns’ surface with a narrow size distribution centered at ca. 8.5 nm. The obtained nanostructures show photocatalytic self‐cleaning activity as shown by the elimination of an organic layer deposited on their surface and the detection of hydroxyl radicals. Photoelectrochemical measurements show a better charge separation at the Au/TiO2 interface. In addition, wettability studies show that the degree of hydrophobicity of the surface is increased by the presence of nanocolumns, both in the dark and under UV illumination. This behavior is not modified by the presence of Au nanoparticles on the surface. The obtained results open up interesting implications in the tunability of the properties of nanostructured thin films for this kind of photo‐activated application.

No abstract

This work presents the gas phase synthesis of CoCr nanoparticles using a magnetron-based gas aggregation source. The effect of the particle size and Co/Cr ratio on the properties of the nanoparticles is investigated. In particular, we report the synthesis of nanoparticles from two alloy targets, Co90Cr10 and Co80Cr20. In the first case, we observe a size threshold for the spontaneous formation of a segregated core@shell structure, related to the surface to volume ratio. When this ratio is above one, a shell cannot be properly formed, whereas when this ratio decreases below unity the proportion of Cr atoms is high enough to allow the formation of a shell. In the latter case, the segregation of the Cr atoms towards the surface gives rise to the formation of a shell surrounding the Co core. When the proportion of Cr is increased in the target (Co80Cr20), a thicker shell is spontaneously formed for a similar nanoparticle size. The magnetic response was evaluated, and the influence of the structure and composition of the nanoparticles is discussed. An enhancement of the global magnetic anisotropy caused by exchange bias and dipolar interactions, which enables the thermal stability of the studied small particles up to relatively large temperatures, is reported.