Switchable nanodumbbell probes for analyte detection.

Nanodumbbell gold nanoparticle (AuNP) dimers connected by DNA show significant change in interparticle distance in the presence of a specific analyte, ATP. The nanodumbbell begins in an extended state, but after the addition of the analyte, the DNA connecting the AuNPs forms a stable hairpin, which causes a large decrease in the interparticle distance.