Formation, thermal stability, and surface composition of size-selected AuFe nanoparticles

The surface composition of isolated $Au0.5Fe0.5$ nanoparticles (NPs) synthesized by micelle encapsulation and supported on $TiO2(110)$ has been investigated. The study reveals that phase-segregated structures are present after annealing at $300°C$⁠. A subsequent thermal treatment at $700°C$ resulted in the formation of a AuFe alloy. At this temperature, a state characteristic of Fe was identified at the NPs’ surface. Annealing at $900°C$ resulted in the disappearance of the Fe surface state, which is attributed to Au segregation to the surface. The initial hexagonal NP arrangement on the $TiO2(110)$ surface was preserved up to $900°C$⁠. At $1000°C$⁠, Au desorption was observed.