Improved Spectral Distinction of Iron Oxides Nanoparticles by using Magnetic Extraction
Jia-Ren Lee1, Wei-Cheng Ding1*, Bo-Wen Shiau1
1Department of Physics, National Kaohsiung Normal University, Kaohsiung, Taiwan
* presenting author:丁暐城,
This paper studies optical characteristics of iron oxides nanoparticles prepared by electrochemical reduction method by absorption spectrum. The stabilizer and micelle relaxant in the solution are CTAB and acetone respectively. The absorption peak positions of CTAB and acetone are 221 nm and 264 nm, therefore the clad spectral profile of nano iron oxides become difficult to be identified. In addition to the nano iron oxides, the larger iron oxides particles are also produced during the electrochemical reduction process. The shielding effect of these larger iron oxide easily induce overall absorbance increasing in the absorption spectrum. We use externally applied magnetic fields to collect nano iron oxides and effectively decrease the influence of CTAB, acetone and the larger iron oxide in the absorption spectra. The larger iron oxides in the solution are first attracted to weaker magnet, it is helpful to reduce the shielding effect of larger particles in the absorption spectra. Then the nano iron oxides are collected by stronger magnet. The concentration of residual CTAB and acetone are decreased by rinsing with deionized water. The absorption peak position of collected nano iron oxides solution is observed around 217 nm, but its absorbance is low. We speculate that not only the larger iron oxides but a part of the nano iron oxides are also attracted to weaker magnet. Therefore, the initially collected iron oxides are uniformly dispersed in deionized water; the weaker magnet and deionized water are again used to attract larger particles and rinse out nano iron oxides respectively. Thereby, the concentration of the larger iron oxides in the solution is effectively reduced then the nanoparticles are repeatedly extracted by stronger magnet attracting. Furthermore, total collected nano iron oxides are dispersed in deionized water to measure absorption spectrum. Consequently, the spectral overlap of CTAB, acetone and the larger iron oxides are obviously diminished; the absorption feature of nanoparticles (peak wavelength ~ 217 nm) can be observed distinctly.

Keywords: nanoparticles, iron oxides, magnetic extraction