The self-assembling of DNA-templated Au nanoparticles into nanowires and their enhanced SERS and catalytic applications

Abstract

A simple photochemical technique is described for the synthesis of organized assemblies of Au nanoparticles (NPs) on a DNA template in a shorter time scale. The smaller Au nanoparticles (NPs) are initially formed in the DNA solution, self-assembled together, and generate the nanowire structures. The diameter and the length of the nanowires can be tuned by controlling the different reaction parameters. The average diameters of the individual Au NPs could be varied in the range of 10–50 nm, whereas their lengths could be extended to the level of several micrometres. The mechanism for the formation of the self-assembled structure of Au NPs on DNA is elaborated upon. The DNA–Au nanowire shows a highly stable and reproducible signal in surface enhanced Raman scattering (SERS) studies. The SERS activity was examined with Rhodamine 6 G (R6G) as a model dye molecule and the observed enhancement factor (EF) was ∼106. The catalytic activity was tested for the reduction of 4-nitroaniline (4-NA) with sodium borohydride in aqueous solution. The synthesized Au nanowires were found to be stable for more than six months under ambient conditions at room temperature without any change of the optical properties. The superior SERS and catalytic activities of the material might be useful in future for different applications in organic catalysis reactions and in a variety of SERS based detections of bio-molecules, as sensors etc.