Redox Transmetalation of Prickly Nickel Nanowires for Morphology Controlled Hierarchical Synthesis of Nickel/Gold Nanostructures for Enhanced Catalytic Activity and SERS Responsive Functional Material

Abstract

A nonpolar surfactant assisted mild wet chemistry approach has been presented for controlled fabrication of ferromagnetic ultralong (several micrometers in length) prickly nickel nanowires in gram scale with the assistance of hydrazine hydrate as the reducing agent and nickel chloride as the metal ion precursor. Nanowire structures analogous to the natural plant Euphorbia milii resulted due to the magnetic dipole driven self-assembly, and their alignment was oriented desirably with an external magnetic field. Systematic microscopic characterizations identified the nanowire to be pure fcc-Ni (i.e., face-centered cubic Ni) without any signature of contamination, though X-ray photoelectron spectroscopy (XPS) and magnetization measurements refer to the existence of an ultrathin nickel oxide (NiO) layer over the nanostructures. The as-synthesized nanowires were used as a single-source precursor for the evolution of nanometric black NiO when calcined. Again, the Ni nanowires act as a sacrificial template that addresses deposition of metallic gold over the nanowire with variable structural hierarchy through their quantitative oxidative dissolution. Then, the composite material serves as a heterogeneous catalyst for reduction of 4-nitrophenol, and a probable reaction mechanism has been suggested. Additionally, the materials were proved to furnish a full-proof enhanced field effect for prolific surface-enhanced Raman scattering (SERS) activity. In a nutshell, the strategy provides a new horizon to design need-based functional material with much practical implication.