Surface segregation phenomenon in goldbased bimetallic nanoparticles

Au-based bimetallic nanoparticles, composed of two distinct metal elements, have the superior chemical and physical properties than monometallic Au nanoparticles owning to the synergistic effect in alloy. However, the improved performance is critically dependent on the surface state, because most catalytic and biological reactions merely take place on the surface during the catalytic process. Surface segregation is a common phenomenon existing in bimetallic nanoparticles, which can make one component in the nanoparticle bulk spontaneously migrate onto the surface and occur the enrichment of surface concentration. The driving force of surface segregation is derived from minimization of system energy and establishment of new equilibrium. In this chapter, we introduce the most recent and important progress of the surface segregation in Au-based bimetallic nanoparticles including surface characterization techniques, typical segregation inducements, and phase separation. The unique features involving surface properties make the surface segregation owning the huge potentials for physical, chemical, and biological applications. Therefore, we face unprecedented challenges and opportunities to convert surface segregation to a new surface controlling technique.