A Beacon of Light

We demonstrated controlled conversion of DNA/Ag NCs between bright and dark states and designed a new molecular probe, NCB, for homogeneous detection of nucleic acid targets. Not relying on Forster energy transfer as the fluorescence on/off switching mechanism, NCBs have the potential to reach an ultrahigh S/B ratio in molecular sensing. Since the fluorescence enhancement is caused by intrinsic nucleobases, our detection technique is simple, inexpensive, and compatible with commercial DNA synthesizers. Here, we demonstrated that a palette of NCB light-up colors can be produced from the same origin by employing different proximal sequences. We also showed that the NC-nucleation sequences capable of achieving strong red fluorescence enhancement share a common 5´-C₃NNNNNC₄ motif.