An efficient method of SPION synthesis coated with third generation PAMAM dendrimer

• Magnetite NPs based on FeCl3/FeSO4/NH4OH were synthesized by coprecipitation method with modification of temperature and extended synthesis time to achieve smaller and uniform size.
• The particles synthesized at higher temperature and prolonged time showed higher saturation magnetization.
• Optimal particle with higher saturation magnetization and uniform size distribution was obtained at 70 °C and 0.012 M of Fe salt concentration.
• High efficient aminosilane coating of magnetite nanoparticles was obtained by modification of synthesis procedure.
• PAMAM-grafted magnetite nanoparticles with considerable magneto-fluorescent properties were prepared.

In this study, superparamagnetic iron oxide nanoparticles (SPION) were synthesized by coprecipitation of FeSO4·7H2O and FeCl3·6H2O with NH4OH at different temperatures and iron salt concentrations. The results showed that magnetite nanoparticles synthesized at elevated temperature (70 °C) and moderate salt concentration (0.012 M for FeCl3) had the highest saturation magnetization (67.8 emu/g) with the size of about 9 nm. The optimal magnetite nanoparticles with the lowest aggregation and highest magnetic behaviour were coated by polyamidoamine (PAMAM) dendrimer. The samples were characterized with X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, fluorescent spectroscopy and magnetization measurements (VSM). The coated materials illustrated strong magnetic behaviour and XRD pattern like magnetite. The presence of FeOSi bond in FTIR spectra confirmed the formation of thin APTS layer on the surface of magnetite nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA) indicated that the modification of core synthesis technique can raise the efficiency of aminosilane coating reaction (as an initiator for PAMAM dendrimer) up to 98% with the production of about 610 dendritic arms. TGA and FTIR spectra of PAMAM-grafted nanoparticles also verified the perfection of repetitive Michael addition and amidation reactions. The fluorescence spectrum displayed the excitation and emission peaks around 298 and 328 nm, respectively for PAMAM-grafted nanoparticles. We believe the resultant material showed the fluorescent properties which could be an applicable and powerful tool for biomedical diagnostic applications.

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