Chemical Preparation of Bimetallic Fe/Ag Core/Shell Composite Nanoparticles

Abstract

Bimetallic iron/silver (Fe/Ag) core/shell nanoparticles were prepared by chemical reduction from ferrous sulfate in the presence of sodium borohydride as a reducing agent in water, followed then by redox transmetalation with addition of silver nitrate (AgNO3) solution. When the reduction temperature was increased from room temperature to 85 °C, Fe nanoparticles with a reduced crystallite size ranging from 5.5 to 2.0 nm resulted. The particles changed from spherical to plate-like morphology as the temperature reached 85 °C. Addition of trisodium citrate was able to protect the precipitated Fe nanoparticles from oxidation; nonetheless, the citrate would facilitate chelation of the Fe clusters so that dense Fe aggregates with a mean diameter greater than 100 nm were found as the concentration of trisodium citrate exceeded 3.33 mM. A continuous Ag film was formed on the Fe surface by the redox transmetalation. This Ag film became a raspberry structure involving preferential deposition of particulate Ag on the Fe particles when the AgNO3 concentration exceeded 76.9 mM. Magnetic saturation was found to reduce with the increasing Ag concentration in the bimetallic composite nanoparticles.

Magneto-plasmonic nanostructures for SERS: magnetite decorated by silver and gold nanoparticles

“…[10][11][12] These composites are usually made from a magnetic core and plasmonic shell, however, the reversed structure is also available. 13 The magnetic core is usually made from iron oxide, more specifically, magnetite (Fe 3 O 4 ), 1,10,[14][15][16][17][18] but pure iron, 19,20 cobalt 5 or other materials 3 could be used. The plasmonic part is typically made of gold or silver.…”

“…The plasmonic part is typically made of gold or silver. It can be a solid shell, smooth 4,11,19,21,22 or spiked, 7 or composed of small particles [1][2][3]20,23 that later could be grown into a shell. 18,24 Ag/Au nanoalloys were also used to overlay magnetite nanoparticles.…”