The　common　drawbacks　of　current　colorimetric　sensors　using　gold　nanoparticle　aggregation　is　its　relatively　low　sensitivity　and　narrow　dynamic　range,　which　restrict　their　application　in　real　sample　analysis　when　competing　with　other　analytical　techniques　such　as　fluorescence　and　chemiluminescence.　In　this　article,　we　demonstrate　a　novel　strategy　to　construct　colorimetric　sensors　based　on　gold　nanoparticle　aggregation.　Unlike　the　conventional　colorimetric　sensors　which　cause　the　formation　of　large　nanoparticle　aggregates,　in　our　strategy,　dimers　are　selectively　formed　upon　target　binding,　which　results　in　significantly　improved　long-term　stability　and　a　more　than　2　orders　of　magnitude　wider　dynamic　range　of　detection　than　that　of　the　conventional　colorimetric　sensors.　In　addition,　a　strategy　to　minimize　the　interparticle　gap　through　the　formation　of　a　Y-shaped　DNA　duplex　enables　to　increase　the　limit　of　detection　by　10　000　times.　The　analytical　figures　of　merit　of　the　proposed　sensor　are　comparable　to　those　of　the　fluorescence-based　sensors.　©　2013　American　Chemical　Society.