Composition modulation of optical absorption in AgxAu1−x alloy nanocrystals in situ formed within pores of mesoporous silica

Nanoscaled ${\mathrm{Ag}}_x{\mathrm{Au}}_{\text{1−x}}$ $\text{(0.2<x<0.8)}$ alloy particles were synthesized by putting gold and silver particles into pores of monolithic mesoporous silica by soaking and annealing method. It has been found that in optical absorption spectrum, the surface plasmon resonance (SPR) maximum of ${\mathrm{Ag}}_x{\mathrm{Au}}_{\text{1−x}}$ alloy particles can shift from about 524 nm (SPR maximum of Au nanoparticles) to about 400 nm (SPR maximum of Ag nanoparticles) with increasing concentration of Ag in ${\mathrm{Ag}}_x{\mathrm{Au}}_{\text{1−x}}$ alloy particle. The simulation of optical absorption spectrum of ${\mathrm{Ag}}_x{\mathrm{Au}}_{\text{1−x}}$ alloy particles was conducted based on Mie theory. The calculated values are found to be consistent with the experimental results.