Metallic Nanoparticles Embedded in Mesoporous Titania Films: Study and Control of Local Electrical Properties by SPM

MERCEDES LINARES MOREAU; LETICIA GRANJA; EDUARDO MARTÍNEZ; IANINA L. VIOLI; M. CECILIA FUERTES; L. LÓPEZ MIR; C. OCAL; PABLO LEVY; GALO J. A. A. SOLER-ILLIA

Bueno Aires

Simposio; Frontiers in Physical Sciences; 2016

Max Plank

Mesoporous titania (MT) thin films present a variety of applications in several fields, such as catalysis,optics, sensing and biomaterials, among others. Loading MT with metallic nanoparticles (NPs) inside the pores allows to take advantage of the size and confinement of the NPs, protecting them from the environment. In this work we present a study of the local effects in the electric properties and topography of MT thin films embedded with gold and silver NPs, by means of Conducting Atomic Force Microscopy (CAFM) and Kelvin Probe Force Microscopy (KPFM). These studies are relevant in the development and characterization of micro- and nanodevices based on TiO2 and TiO2-metal nanocomposites.The MT films were synthesized by sol-gel and dip coating, using conductive Si substrates. Metallic NPs were incorporated to the films using two methods: in situ AuCl4 adsorption-reduction cycles for the MT-Au samples; and photoreduction of Ag+ ions in solution for the MT-Ag samples. For the latter, it is possible to selectively embed regions of the film with micron resolution through a lithographic mask [1]. Local electric transport and contact surface potential were studied by CT-AFM and KPFM. Sample morphology and composition were also studied by SEM and EDS. The results show that it is possible to locally modify the electric resistance and topography using CAFM scans under bias voltage for both systems.For the MT-Ag samples, the results suggest Ag+ ion migration and redistribution in the porous matrix driven by the electric field applied by the AFM tip. Previous studies in this system confirm that the electric transport develops three-dimensionally inside the film, which further supports this hypothesis[2]. For the MT-Au case, KPFM measurements provide information on the distribution of the Au NPs inside the film even when they are not electrically ?connected? to the substrate, in contrast to CAFM images. These results were compared to previous studies in the MT film with no NPs, in which we have confirmed a similar effect that depends strongly on ambient humidity and film porosity.[1] Martínez, E. D., Bellino, M. G., Soler-Illia, G. J. A. A., Appl. Mater. Interfaces 1 (4), 746-749 (2009).[2] Martínez, E. D., Granja, L., Bellino, M. G., Soler-Illia, G. J. A. A., Phys. Chem. Chem. Phys. 2 (43), 14445-14448 (2010).[3] Linares Moreau, M. M., Granja, L. P., Fuertes, M. C., Martínez, E. D., Ferrari, V., Levy, P. E., Soler-Illia, G. J. A. A., J. Phys. Chem. C 119 (52), 28954-28960 (2015).