Raman spectroscopy as a powerful technique in the characterization of ferrofluids

Raman spectroscopy has been used to get some insight into the chemical comp osition and structure of magnetic fluids based on ferrites. The inner as we ll as the surface structure of Fe-maghemite and Zn-maghemite have character ized by Raman spectroscopy. It has been shown that different chemical speci es are present on the maghemite surface by changing the laser excitation en ergy. Maghemites modified by the adsorption of aspartic and glutamic acids as well as those modified by the adsorption of methylene blue(MB) have also been investigated by Raman spectroscopy. It has been shown that while FTIR (Fourier transform infrared) spectroscopy gives almost no information rega rding to the surface species, Raman spectroscopy in and off resonance gives suitable information regarding to the adsorbate structure and bonding. The Raman spectroscopy study of the modified maghemites have shown that the or ganic acids adsorb on the maghemite surfarce as glutamate and aspartate che mically bounded to Fe(III) ions on the maghemite surface, and that MB, a ca tion, adsorbs on the maghemite surface as a monomer by ion pair formation w ith coadsorbed nitrate.