Ionic surface masking for low background in single- and double-stranded DNA-templated silver and copper nanorods

A straightforward procedure is presented for the fabrication of single-stranded DNA-templated silver nanorods and double-stranded DNA-templated copper nanorods with a low background of nonspecific metallic deposition. Alkali metal cations with high affinity for SiO2 are used to passivate the silicon surface, creating a physical and an electrostatic barrier against nonspecific silver or copper cation adsorption and subsequent metal deposition. For silver nanorods synthesized from single-stranded DNA, this ionic masking strategy leads to a 51% reduction in the number of nonspecifically deposited nanoparticles and an even greater decrease in their dimensions. For DNA-templated copper nanorods this surface blocking approach decreases the number of nonspecifically deposited nanoparticles by 74%. The demonstration of the use of single-stranded DNA as a template for nanorod fabrication is an important step toward the creation of nanoscale circuits by combining DNA metallization with direct surface hybridization of oligonucleotide-coupled, electronically active nanostructures at predetermined positions on single-stranded DNA.