Surface segregation and homogenization of Pd70Ag30 alloy nanoparticles

Pd70Ag30 alloy nanoparticles were prepared using three different reducing agents at various pH values. The composition homogeneity inside the alloy nanoparticles was tuned by the reduction conditions. The surface segregation and homogenization during heating was then studied. Alloy nanoparticles with the smallest size and the highest homogeneity were prepared by the strongest reducing agent NaBH4, and the change of surface composition after heating was the smallest. The surface segregation of Ag was small and the sintering was retarded by the high concentration of surface Pd or by the residual B from the reducing agent. There was significant surface segregation of Ag and sintering after heating for the alloy nanoparticles prepared by HCHO, where a higher concentration gradient existed inside the nanoparticles. The reducing capability of N2H4 was in between those of HCHO and NaBH4 and the behavior of nanoparticles prepared by N2H4 also exhibited a behavior between those of the other two samples. (c) 2006 Elsevier B.V. All rights reserved.