Functional hybrid nickel nanostructures as recyclable SERS substrates: detection of explosives and biowarfare agents

Abstract

We present the synthesis of highly anisotropic nickel nanowires (NWs) and large area, free-standing carpets extending over cm² area by simple solution phase chemistry. The materials can be post-synthetically manipulated to produce hybrid tubes, wires, and carpets by galvanic exchange reactions with Au³⁺, Ag⁺, Pt²⁺, and Pd²⁺. All of these structures, especially the hybrid carpets and tubes, have been prepared in bulk and are surface enhanced Raman scattering (SERS) active substrates. Molecules of relevance such as dipicolinic acid (constituting 5–15% of the dry weight of bacterial spores of Bacillus anthracis), dinitrotoluene, hexahydro-1,3,5-triazine (RDX), and trinitrotoluene at nanomolar concentrations have been detected. An enhancement factor of ∼10¹⁰ was observed for the Ni–Au nanocarpet. The reusability of the Ni–Au nanocarpet for SERS applications was tested 5 times without affecting the sensitivity. The reusability and sensitivity over large area have been demonstrated by Raman microscopy. Our method provides an easy and cost effective way to produce recyclable, large area, SERS active substrates with high sensitivity and reproducibility which can overcome the limitation of one-time use of traditional SERS substrates.