Self-assembled wire-like and honeycomb-like osmium nanoclusters (NCs) in DNA with pronounced catalytic and SERS activities

Abstract

A new route to the formation of ultra-small Os nanoparticles (NPs) in DNA is reported. The Os NPs that are initially formed are self-assembled together to form Os nanoclusters (NCs) which have wire-like and honeycomb-like morphologies. The synthesis was carried out within a minute using microwave heating by the reaction of Os salt with ethanol. The size of the individual Os NPs varies between 1 and 3 nm and the synthesized particles are stabilized in DNA. The stable Os NCs showed a coupled SPR band near 600 nm in the visible region, which is useful for using the material as a potential SERS substrate. The SERS study was carried out using methylene blue (MB) as a model SERS probe molecule and the observed EF value is ∼10⁷, which is much higher compared to a recent report for Os NPs. Apart from SERS, the Os NCs have also been tested in a catalysis reaction. The catalysis reaction was carried out for the first time for the reduction of organic nitro compounds in the presence of excess NaBH₄. The catalytic reaction rate using Os NCs as a catalyst was found to be superior compared to earlier reports with other metal NPs, like Au or Ag. The improved catalytic and SERS activities of the Os NCs due to their ultra-small size with a high surface area might be useful in future in the field of biosensors, biomedicine, nano devices and other organic catalysis reactions.