Coordination-Mediated Programmable Assembly of Unmodified Oligonucleotides on Plasmonic Silver Nanoparticles

DNA-decorated metal nanoparticles have found numerous applications, most of which rely on thiolated DNA (SH-DNA)-modified gold nanoparticles (AuNPs). Whereas silver nanoparticles (AgNPs) are known to have stronger plasmonic properties than AuNPs, modification of AgNPs with SH-DNA is technically challenging, partially due to the instability of Ag-S bonding. Here we demonstrate a facile approach to self-assemble unmodified DNA on AgNPs by exploiting intrinsic silver-cytosine (Ag-C) coordination. The strong Ag-C coordination allows for the ready formation of DNA-AgNP conjugates, which show favorable stability under conditions of high ionic strength and high temperature. These nanoconjugates possess much higher efficient molecular recognition capability and faster hybridization kinetics than thiolated DNA-modified AgNPs. More importantly, we could programmably tune the DNA density on AgNPs with the regulation of silver-cytosine coordination numbers, which in turn modulated their hybridizability. We further demonstrated that these DNA-AgNP conjugates could serve as excellent building blocks for assembling silver and hybrid silver-gold nanostructures with superior plasmonic properties.