We are presenting a method for modulating the size of US nanoparticles by templating their formation with oligo(guanine)(n) oligomers where n varied from 5 to 20. The variation in template length resulted in observable changes in the size distribution of the US nanoparticles. Statistical analysis of AFM images showed a general trend whereby the US average height decreased for longer oligoG(n) and increased for shorter oligoG(n). Concomitantly, shorter oligoG(n). yielded more dispersed populations, while longer oligoGn gave less dispersed populations. This synthetic methodology could be extended to the synthesis of other nanoparticles and even to mixed-metal nanoparticles resulting in a powerful method for fine-tuning size-dependent properties.