Surface Plasma Resonance of Gold-coated Iron-oxide Nanoparticles
Yousaf Iqbal · Hongsub Bae · Ilsu Rhee ∗
Department of Physics, Kyungpook National University, Daegu 702-701, Korea
Sungwook Hong
Division of Science Education, Daegu University, Gyeongsan 712-714, Korea (Received 9 December 2014 : revised 23 February 2015 : accepted 23 February 2015)
Gold-coated iron-oxide nanoparticles were synthesized by using chemical reactions. The X-Ray diffraction (XRD) confirmed the crystallinity of the cubic spinel structure. Transmission electron microscope (TEM) images showed that the gold-coated iron-oxide nanoparticles were spherical in shape with an average diameter of 15.5 nm. The binding of the gold to the surface of the iron- oxide nanoparticles was revealed by using measurements made with Fourier transform infrared (FTIR) spectrometer. The vibrating sample magnetometer (VSM) results showed no hysteresis, indicating that the nanoparticles were superparamagnetic with a single domain. A surface plasma resonance was observed in an aqueous solution of the gold-coated iron-oxide nanoparticles, which provided direct evidence that the gold was well bound to the surfaces of the iron-oxide nanoparticles.
The wavelength of the surface plasma resonance of the gold-coated iron-oxide nanoparticles was compared with those of gold nanoparticles. We observed a red-shifted surface plasma wavelength for the gold-coated iron-oxide nanoparticles, which was another piece of evidence for gold being well bound on the surfaces of the iron-oxide nanoparticles.
PACS numbers: 81.05.Ni, 76.60.Es, 61.46.Df, 87.61.-c
Keywords: Iron-oxide nanoparticles, Gold coating, Surface plasma resonance, Superparamagnetic
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