Raman spectroscopy in oleoylsarcosine-coated magnetic fluids: A surface grafting investigation

Raman spectroscopy is used to investigate magnetite nanoparticles pre-coated with oleoylsarcosine and dispersed as stable water-based (WB) and hydrocarbon-based (HB) magnetic fluids (MF's), The Raman spectra obtained from the MF samples and from liquid water were compared and the data discussed in terms of the suppression of the symmetrical hydroxyl (OH) vibrational modes. The effective grafting coefficient of the oleoylsarcosine in the WB-MF, with respect to the HB-MF, was estimated through the OH-stretching Raman modes of the OH-group chemisorbed at the nanoparticle surface. It was found that the OH-grafting coefficient in the HB-MF sample is about 3 times lower than the grafting coefficient in the WB-MF sample.