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 degrees C. A subsequent thermal treatment at 700 degrees 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 degrees 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 degrees C. At 1000 degrees C, Au desorption was observed.