Citrate-assisted synthesis of prickly nickel microwires and their surface modification with silver

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

We present the synthesis of highly anisotropic nickel nanowires (NWs) and large area, free-standing carpets extending over cm(2) 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 Au(3+), Ag(+), Pt(2+), and Pd(2+). 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 ∼10(10) 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.

Effect of organic modifiers on the structure of nickel nanoparticles and catalytic activity in the hydrogenation of p-nitrophenol to p-aminophenol

Spherical nickel nanoparticles with different sizes and different structures were prepared starting from nickel oxalate and using hydrazine hydrate as a reductant in the presence of citric acid, cetyltrimethylammonium bromide, Tween 40, and d-sorbitol as organic modifiers. The size and structure of the resultant nickel nanoparticles were affected by using different organic modifiers. All of the nickel nanoparticles showed higher catalytic activity and selectivity than the conventional raney Ni catalyst in the hydrogenation of p-nitrophenol to p-aminophenol. Although the catalytic activities of the resultant nickel nanoparticles generally increased with decreasing particle size, the structure of nickel nanoparticles also had an important impact on the catalytic activity.