Nonlocal nonlinear optical response of PEGylated superparamagnetic Fe3O4 nanoparticles

Abstract PEGylated superparamagnetic Fe 3 O 4 nanoparticles were prepared using co-precipitation method and analyzed by using X-ray diffraction (XRD), UV–Visible spectroscopy, Fourier-transform infrared (FTIR), Transmission electron microscopy (TEM), Dynamic light scattering (DLS), Vibrating sample magnetometer (VSM) and TG analysis. The XRD results showed that an FCC phase of the Fe 3 O 4 structure was formed by an average lattice constant about 8.379 A. From optical absorbance spectra, the linear absorption coefficient and the band gap of PEGylated Fe 3 O 4 nanoparticles were measured 0.855 cm −1 and 2.27 eV, respectively. The magnetic characteristics indicated that the PEGylated Fe 3 O 4 nanoparticles had the saturation magnetic moments of 61 emug −1 . The measurements of nonlinear optical (NLO) properties of PEGylated Fe 3 O 4 nanoparticles have been performed using a nanosecond Nd:YAG pulse laser at 532 nm by the Z-scan technique. Both bare and PEGylated Fe 3 O 4 nanoparticles clearly were exhibited a negative NLO index of refraction at 532 nm. A nonlocality in NLO response of nanoparticles was observed after PEGylation. The NLO absorption of PEGylated Fe 3 O 4 nanoparticles is attributed to 2-photon absorption. A good NLO absorption was observed for both bare and PEG-coated Fe 3 O 4 nanoparticles at 532 nm. Moreover, the nonlinear susceptibility of PEG-coated Fe 3 O 4 nanoparticles was determined by the Z-scan technique of the order of 10 −9 esu. The outcomes suggest that PEGylated Fe 3 O 4 nanoparticles may be a promising candidate for the NLO applications.