Use of the photoacoustic spectroscopy in the investigation of biocompatible magnetic fluids

Abstract
In this study photoacoustic (PA) spectroscopy was used to investigate biocompatible magnetic fluids (BMFs). The observed spectral features, in the 0.3 to 1.0 m wavelength region, are discussed in terms of three distinct bands (L, S, and C). Band-L, in the spectral range of 0.65 to 0.86 m, is related to the characteristic coating layer of the magnetic nanoparticle. Band-S, occurring around 0.50 m, is related to the metal-polyoxy-hydroxy surface layer built up at the surface during the nanoparticle synthesis. Band-C (0.36 to 0.43 m) is associated to the optical absorption of the semiconductor magnetic nanoparticle. Features in band-L and band-S are discussed in terms of surface grafting coefficient of the dextran and DMSA surface-coating agents. Distinct Fe₃O₄ nanoparticles (average diameters of 3.1 and 5.6 nm) are used as core materials and display the nanoparticle size effect.