Electrically conducting osmium nano-chain networks with superior catalytic and SERS performance

Abstract

A new route for the aqueous phase formation of highly dense, chain-like electrically conducting osmium (Os) nano-chain networks at room temperature within 30 minutes of reaction time is reported. Smaller Os particles were formed in the solution and grew in the sodium dodecyl sulphate (SDS) surfactant medium to generate the network structure. The average diameter of the individual Os particles was ∼1–3 nm, whereas the diameter of the nano-chains was ∼5–7 nm. The nominal lengths of the network structures were found to be in the range of 2 to 3 microns. The synthesized nano-chain networks showed a coupled surface plasmon resonance (SPR) band near the visible region, and could therefore be used as a substrate in surface-enhanced Raman scattering (SERS) studies. Based on our understanding and literature knowledge, this is the first example where Os particles were utilized for the catalytic decomposition of toxic KMnO₄ solutions. It was found out that the use of Os resulted in a better catalytic performance as compared to a traditional oxide based catalyst for the decomposition of toxic KMnO₄ solutions. The SERS study was performed using methylene blue (MB) as a model SERS probe molecule, and the observed enhancement factor (EF) value was 1.67 × 10⁷, which is the highest ever reported for Os NPs. Apart from its applications in catalysis and SERS, we also investigated the electronic properties of Os nano-chain based network structures for the first time. Based on a current–voltage (I–V) study, it was found that the network structure was electrically conducting and exhibited the Coulomb blockade effect at 298 K, and the resistance of the device was calculated to be ∼1.98 × 10⁸ Ω. This room temperature Coulomb blockade characteristic is indicative of “single electronic transport”. We believe that this technique provides a route for the formation of other series of nano-gap structures with uniform morphologies for other potential applications.