Temperature-Induced Interfacial Change in Au@SiO2 Core-Shell Nanoparticles Detected by Extended X-ray Absorption Fine Structure

Core-shell nanoparticles were widely studied because of their potential application. However, there are few reports about the interfacial structure and its stability. In this paper, Au@SiO2 nanoparticles have been synthesized by using the traditional sol-gel method. In situ extended X-ray absorption fine structure technique was used to characterize the structural change with temperature. It is found that the interfacial bonding between the Au core and the silica shell has changed from a Au-N bond to a Au-Si bond when the temperature is above 600 degrees C. The Au-silica interface with Au-Si bonds between the Au core and silica shell can be stably existed in the temperature range of 600 to 1000 degrees C. The mechanism of bond change is described. The thermal expansion coefficient of Au nanoparticles in the Au@SiO2 core-shell system is obtained to be 1.4 x 10(-5) K-1, which is almost the same with Au bulk. The details of the structural changes and thermal expansion behavior are discussed in this paper.