Suspensions of electrocatalytic gold nanoparticles with radii as small as 83 ± 13 nm that are functionalised with DNA only in one region have been created using templated electrodeposition. The integrity of the bound DNA following nanoparticle desorption from the electrode is demonstrated by detecting picomolar concentrations of DNA without the need for molecular, e.g., PCR or NASBA, amplification.