Synthesis of ultra-small Rh nanoparticles congregated over DNA for catalysis and SERS applications

Exploration of rare earth metals for the Surface Enhanced Raman Scattering (SERS) is greatly preferred to identify probe molecules even at nano molar level. Highly stable Rh nanoparticles (NPs) which are ultra-small size have been prepared within 20 min of reaction time as a colloidal solution using a bio-molecular scaffold DNA and NaBH₄ as a reducing agent under room temperature. While keeping metal ion concentration fixed and by making difference in DNA concentration, three different sets of Rh@DNA such as 0.08, 0.085 and 0.09 M were formed as nanochains like structure with varying diameters. The average chain length of Rh NPs for varying concentrations of DNA is ∼98 nm and the Rh particles size is below 5 nm in all the cases. These ultra-small Rh NPs have been utilized for two distinct potential applications such as in catalysis and SERS studies. From the catalysis reaction, reduction of 4-Nitro benzaldehyde to 4-amino benzaldehyde, Rh@DNA (0.08 M) has shown rate constant value of 0.26 min^-1 which is highest among other concentrations studied. SERS study revealed that the calculated Enhancement Factor (EF) value was 1.19 × 10⁵ for Rh@DNA (0.08 M) which is highest while compared with other concentrations. Apart from catalysis and SERS, the as-synthesized Rh NPs can find applications in other interdisciplinary fields such as organic catalysis, electro-catalysis and so on in near future.