Self-assembling of metallic Rh over DNA as nano-chains: An effective organosol for catalysis and SERS studies

Abstract

Rarely explored materials in organic medium for catalytic applications are one of the promising methods for high rate conversion and selectivity to achieve monodispersity. In this present work, for the first time, we have prepared Rh NPs in organic medium (as organosol) using microwave heating condition. The process results a colloidal solution that is stable for more than five months while keeping at low temperature in refrigerator. The self-assembled Rh-DNA as organosol was formed in two different morphologies such as nano-chains and nano-beads simply by varying the metal ions to DNA molar concentration as Rh-DNA (0.0035 M) and Rh-DNA (0.007 M), respectively. Interestingly, here, DNA was used as a scaffold which has manifold advantages over other commonly used scaffolds by providing its aromatic base pairs, negative phosphate groups and hydroxyl groups to stabilize Rh3+ metal ions. This colloidal solution can readily be dispersed in many organic solvents (protic and aprotic) which is an added advantage compared to aquasol where dispersion to other organic solvents is a problem for catalytic applications. The as prepared two set of Rh-DNA (0.0035 and 0.007 M) were applied for catalytic nitro compound reduction and Surface Enhanced Raman Scattering (SERS) studies. The synthesized two sets of Rh-DNA organosol was highly capable of reducing four different nitro compounds and comparatively, Rh-DNA (0.0035 M) showed better catalytic activity than other one. The enhancement factor (EF) values was calculated at different concentrations ranging from 10−3 M to 10−6 M and the obtained highest EF value is 2.89 × 106 for Rh-DNA (0.0035 M) while using methylene blue (MB) as a Raman probe molecule. This method of synthesis is too simple and gives highly stable solution of Rh-DNA that can be successfully utilized in multidisciplinary applications particularly in medicinal and energy related fields in near future.