Nanowires (Nws) play a crucial role in titanium dioxide's photo-physical and photochemical applications, such as photovoltaics, photocatalysis, and water splitting. Among the techniques employed to synthesise nanostructures, the Au seed-assisted thermal oxidation is the simplest and the most intriguing. TiO2 NWs, with Au-nanoparticles (AuNPs) on the tip, can be obtained by annealing in air, a thin Au film deposited on a metallic Ti. Au-NPs, formed during the annealing, act as seeds for NWs growth, while the oxide layer, formed during oxidation, inhibits the Nws growth. An in-depth investigation is conducted on the effects of various substrates, oxide layer thickness, and oxidation time. We propose a diffusion mechanism involving the transport of Ti interstitials from the metallic Ti substrate, through the TiO2, to the surface. Moreover, high-resolution conductive AFM analysis at the AuNp/TiO2 interface suggests the formation of a nanometric heterojunction. The heterojunction electric field promotes a localised enrichment of Ti interstitials close to AuNps, thereby enhancing the oxidation rate and resulting in the creation of TiO2 nanowires.
TiO2 nanowires growth mechanism via thermal oxidation assisted by Au nanoparticles
Zimbone M.
;Calcagno L.;Lo Po' C.;Ruffino F.;
2026-01-01
Abstract
Nanowires (Nws) play a crucial role in titanium dioxide's photo-physical and photochemical applications, such as photovoltaics, photocatalysis, and water splitting. Among the techniques employed to synthesise nanostructures, the Au seed-assisted thermal oxidation is the simplest and the most intriguing. TiO2 NWs, with Au-nanoparticles (AuNPs) on the tip, can be obtained by annealing in air, a thin Au film deposited on a metallic Ti. Au-NPs, formed during the annealing, act as seeds for NWs growth, while the oxide layer, formed during oxidation, inhibits the Nws growth. An in-depth investigation is conducted on the effects of various substrates, oxide layer thickness, and oxidation time. We propose a diffusion mechanism involving the transport of Ti interstitials from the metallic Ti substrate, through the TiO2, to the surface. Moreover, high-resolution conductive AFM analysis at the AuNp/TiO2 interface suggests the formation of a nanometric heterojunction. The heterojunction electric field promotes a localised enrichment of Ti interstitials close to AuNps, thereby enhancing the oxidation rate and resulting in the creation of TiO2 nanowires.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
