Silver core/silica shell (Ag@SiO2) nanoprisms are prepared by passivating silver nanoprism cores with 16-mercaptohexadecanoic acid (MHA), which prevents their etching and aggregation during the subsequent silica coating reaction. The resulting triangular Ag@SiO2 nanoprisms can be dispersed in organic media, environment in which the bare silver prisms are unstable, and modified with a wide variety of functional groups, including oligonucleotides.