Fig. 1.

(a) and (b) Illustrate the aggregation of silver and gold nanoparticles in the presence of target DNA. As the nanoparticles aggregate their surface plasmons couple, the resonance condition changes, and their characteristic optical peaks red shift. (c) 600 uL of gold nanoparticles, silver nanoparticles and a combination of both are shown, illustrating their optical properties. In the orange gold and silver solution each type of nanoparticle can be functionalized to react differently, allowing for either color change reaction to take place independently.